Subject Human Body

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Human Body: An Introduction to Anatomy & Physiology
Bruce G. Stewart
General Objectives
 To define anatomy and physiology and list and describe selected sub-disciplines;
 To explain the relationship between structure and function;
 To outline and define the levels of organization of the human body and explain why each level is
critical to understanding the human body as a whole;
 To list and briefly explain the major components and functions of each system;
 To know the characteristic processes of life demonstrated by the living human body;
 To list selected resources and environmental components needed for human survival;
 To define homeostasis and describe its significance;
 To complete and Internet exercise (Ben's Bad Day) to reinforce understanding of homeostasis,
interactions between body systems, and feedback mechanisms;
 To describe the affect of disease on homeostasis;
 To understand, identify, and define selected anatomical positions, terms of body direction, body
region, and body plane or section;
 To identify and name major body cavities along with their subdivisions and organs contained;
 To describe the location and general function of serous membranes.
Related Textbook Readings
 Marieb (2010) Chapter 1
Lecture Outlines, Notes, and Selected Exercises
I. Anatomy, Physiology and Their Sub-disciplines
A. Anatomy - the study of structure
1. Gross anatomy - the big picture... large body structures; can be studied from different perspectives
depending on the focus
a. regional anatomy (e.g. everything in the head)
b. systemic anatomy (e.g. system by system which is our primary approach in a general anatomy and
physiology course)
c. surface anatomy (e.g. for learning where to take the pulse or where to do a hypodermic injection)

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2. Microscopic anatomy - the small stuff... beyond human ability to see with the unaided eye
a. cytology - the study of cells which includes the "anatomy" or physical makeup of the parts; this aspect
can be thought of as "cell anatomy."
b. histology - the study of tissues which includes the "anatomy" or physical makeup of the type of cells and
their organization in to tissue types; this aspect can be thought of as "tissue anatomy."
3. Developmental anatomy and embryology
a. developmental anatomy - a discipline that follows (by the comparative method of science!) the
distinctive stages of anatomical development over time spans of the human life; of course, these changes
are connected to changes in physiology
b. embryology - the discipline that includes the developmental changes from conception to birth
B. Physiology - the study of function
1. cell physiology - the study of function at the cellular level (e.g. the process of energy extraction and
convertion by mitochondia)
2. tissue physiology - the study of function at the histological level (e.g. the processes involved in
producing muscle tissue contractions); this requires knowledge and application of principles of cellular
physiology
3. organ and system physiology - the study of the function of individual organs or entire body systems (e.g.
neurophysiology, cardiovascular physiology, osteophysiology)
C. Structure and Function are Complementary
1. This may seem self-evident, but it is worth mentioning; the anatomy (including cytology, histology and
gross) of the a particular structure or system determines its ability to perform particular functions.
Physiology also relates to the anatomy of structures, particularly in the area of development and
maintenance.
2. This complementarity is good reason to study both anatomy and physiology at the same time!
II. Hierarchical Levels of Organization of Life
A. Text Box and Table on Complexity
Hierarchical complexity refers to the many levels of organization and interaction in living things. Sylvia
Mader (2003) notes that each level has properties that are more than a simple sum of its parts. Because
living systems are so much more highly organized and complex than non-living systems, English biologist
and author, Richard Dawkins, has even termed chemistry and physics as the "simple sciences!" He does
not mean "easy" sciences, but rather that biology has so many more levels with unique properties and
interactions. As one moves up the hierarchy from chemical to ecosystem, there are emergent properties
(Johnson and Losos 2008) that are unique to that level and which cannot be understood by simply

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knowing the lower level components and their functions.
The next table lists these levels along with a brief description of each. Read over the whole table, but for
our human anatomy and physiology class, you need know only the information for the levels up to the
multicellular, complex organism.
TABLE. Hierarchical Levels of Organization of Life: Subatomic Through Ecosystems
Level Examples Fields of Study
(there are many others)
Definition or
Properties
subatomic
particles
protons, neutrons, elections
atomic and nuclear
physics
fundamental particles of matter;
affected by nuclear and
electromagnetic forces
atoms
atoms of oxygen, carbon,
nitrogen, hydrogen, etc.
chemistry, physics
smallest unit of an element;
affected by electromagnetic
forces, and possesses unique
chemical and physical properties
molecules a molecule of insulin
biochemistry, molecular
biology
smallest unit of a compound;
affected by electromagnetic
forces, and has unique chemical
and physical properties
organelles
nucleus, cell membrane,
ribosomes, etc.
cytology, molecular
biology, physiology
organized part of a cell with
unique chemical functions
cells
an amoeba, a muscle cell, a
bone cell
cytology, physiology
smallest unit of life that can
perform all life processes
tissues
muscle tissue, nervous
tissue, vascular tissue,
reproductive tissue,
connective tissue, epithelial
tissue
histology, physiology
groups of cells that perform the
same function
organs
a heart, a bone, a lung, a
pituitary gland, etc.
anatomy, physiology
groups of tissues that help
perform a certain function
organ
systems
skeletal system, nervous
system, respiratory system,
cardiovascular system,
reproductive system,
endocrine system, muscular
system, excretory system,
integumentary system
anatomy, physiology
groups of organs that help
perform a certain function
complex
multicellular
organisms
a fox squirrel, a robin, a
roundworm, etc.
human anatomy and
physiology, natural
history, behavior,
morphology, physiology,
systematics, mammalogy,
herpetology, ornithology,
ichthyology, entomology,
etc. (these "ologies"
apply to populations and
communities as well.
an organized and coordinated
group of organ systems that
existed independently as a unit
that can perform all of life’s
processes

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populations
all fox squirrels in a given
bottomland forest, all post
oak trees in a given forest
natural history,
population ecology
a group of organisms of the same
species living within a defined
area
communities
a bottomland hardwood
forest, a pond, a freshwater
stream, etc.
natural history,
community ecology
a group of populations of different
species that live in a defined area
ecosystems
similar to the communities
above but including all
living and non-living
components
landscape ecology,
ecosystem ecology
a group of interacting
communities that occur in a
defined area; includes living and
non-living components
III. Humans Share Critical Properties and Process of Life in General
A. Text Box on Properties and Processes of Life (Including Homeostasis)
Humans are made of Cells - Cellular Organization
The cell theory includes an expression of consistent observations made for over 300 years since the
invention of the microscope. These observations have shown that all living things have a fundamental unit
of structure called the cell. Cells are small structures surrounded by a complex membrane that encloses
an even more complex array of cell organelles that perform the various critical processes of life. The entire
body of some organisms is composed of only a single cell, whereas some others have trillions! The
human brain alone has billions of cells. All living things are made of cells.
Humans Obtain and Manage Energy and Nutrients - Metabolism and Nutrient
Management
A rock can passively have its energy increased! When sunlight strikes a rock, the temperature of the rock
and the total amount of thermal energy it possesses increases. However, a rock cannot control this
process, nor can it use the energy to do work or to obtain nutrients.
Living things by contrast can obtain and control energy through processes like photosynthesis and
metabolism. Photosynthesis is the conversion of visible sunlight energy into other stored or usable forms
of energy. Metabolism is the process of converting energy from a stored form (e.g. energy in a sugar
molecule) to other forms. All living things perform metabolism, but for those that cannot photosynthesize it
is the only way to get usable energy. One type of energy releasing metabolism is called aerobic
respiration. It is basically the opposite of photosynthesis and therefore requires energy rich molecules like
simple sugars and oxygen to work. The energy from photosynthesis and metabolism can be used to do
work such as building molecules of the body structure and creating movement.
Nutrients are substances that an organism takes in and uses for growth and maintenance. Some nutrient
molecules, like glucose, provide two needs for living things. One is that chemical energy is stored in these
molecules and that energy can be extracted by metabolic processes by organisms. The other provision is
the chemical elements found in nutrient molecules. These molecules contain atoms and and molecular
arrangements that serve as raw materials for building their own molecules that make up their bodies.
To summarize, all forms of life show metabolic activity; they extract & transform energy from their
environment and use it for manipulating materials in ways that assure their own maintenance, growth,

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development & reproduction. All living things obtain and manage nutrients for the purpose of extracting
energy and obtaining raw materials needed for the structure and function of their bodies.
Humans Maintain Their External and Internal Conditions in Balance - Homeostasis
Living things must keep levels of internal conditions at levels appropriate for other life processes to occur.
These include things like temperature, pH (acid levels), nutrients, hormones, water, waste concentrations,
and many others. Similarly, external conditions must be appropriate for life. For example, lizards
thermoregulate (adjust their body temperature) by such behaviors as orienting in certain ways to the sun
and moving to rocks that have appropriate temperatures. In this way, their can keep their muscle tissues
at temperatures for optimum performance. This helps them capture prey and escape from predators. The
term that refers to all ways that an organism regulates its internal and external environment is
homeostasis. The ability to respond to stimuli in the environment is often called irritability. This ability
allows all forms of life to use homeostatic controls that maintain the living state even when internal and
external conditions change. These controls may be behavioral or physiological.
Feedback mechanisms are used to adjust conditions so as to maintain a livable balance for many
physiological and physical conditions of the human body. These fall into two main categories: positive
feedback mechanisms and negative feed back conditions. Negative feedback loops are very common in
living things. For example, when your blood sugar rises, special cells in your pancreas release insulin
which promotes cellular uptake of glucose. Lowered glucoses shuts down insulin release. (Another
hormone, glucagon, is important in blood sugar levels and it has its own negative feedback loop).
Negative feedback is illustrated frequently with a familiar example: the thermostat's control of room
temperature. See your text for this example.
Positive feedback can be described as a cascade of events that stop only when they hit a "wall." That is,
they stop when a job is completed. An example of this is the beautiful cascade of events that occur when
you injury yourself and have a loss of blood. The blood clotting process covered in detail in a chapter later
in your textbook is an intricate set of chemical steps that proceeds full force until the bleeding is stopped.
Internet Learning Activity - Ben's Bad Day. Visit this link and follow the instructions to observe
how Ben's body responds to various challenges to maintain homeostasis.Note how Ben's body can detect
stimuli (both internal and external) and then respond appropriately to keep his internal conditions. All living
things must be able to accomplish similar feats.
Human Beings Reproduce and Pass Genetic Codes to Future Generations -
Reproduction and Heredity
Life is unique in its possession of a chemical coding mechanism that allows organisms to produce
offspring of their own kind. One special type of nucleic acid, DNA, is the code-carrying molecule. All living
things possess their own copies of the genetic instructions to operate their bodies. These instructions are
contained in subsets of DNA codes called genes. Furthermore, these instructions can be duplicated and
passed on to reproductive cells that develop into offspring directly or through combinations in sexual
reproduction. Aspects of an organism that are due to this genetic code are referred to as genetically
inherited characteristics. All living things exhibit distinctive patterns of heredity. This is not to say that the
phenotype (form) of an organism is not influenced by environmental factors. Maybe you remember the
long running "nature versus nuture" debate in psychology. The genetic code dictates the "nature"
component of living organisms, and all organisms share this property.
DNA is the storehouse of genetic information for all organisms. Mutations, however, introduce variations in
the patterns, and this allows survival in changing environments. Nature is the testing ground for the

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combination of patterns that come to be expressed in each individual. This is concept of mutation is
especially important in human disease where we are have to be constantly working to develop vaccines
for the lastest flu mutant. Also, much human suffering is caused by mutations that create homeostatic and
physiological breakdowns of many sorts.
Humans Exhibit Growth and Development
From the beginning of the life of each organism, its body undergoes an amazing series of changes. Cells
are replicated, materials are constructed, body size increases, and body form develops. The master plan
for these processes is found in the coded instructions (genes) of DNA. Growth and development follow
this genetic program faithfully. (Although do not forget that the genetic program received may be different
in detail to that of the parents, and that environment plays an important role.)
Think of the process of metamorphosis in butterflies. This has intrigued humans throughout history.
Sexual reproduction between a male and female of the same species produces a fertilized egg (zygote).
This zygote divides and produces immense numbers of descendant cells that differentiate into the various
tissues, organs and organ systems of the caterpillar (the larval stage). This herbivorous (plant eating)
larva enters the pupa stage in which the entire body is overhauled and transformed. Finally, the adult
butterfly emerges in all its glorious beauty!
From the moment of its emergence, each living thing goes through a series of developmental stages, a
continuum of changes in form and behavior. These developmental stages unfold at about the same rate
and in the same way for all organisms of a given species. You yourself went through distinctive stages
(e.g. the "terrible twos")
B. Aspects of Human Life Functions as Listed in Marieb -
1. Boundaries, Movement, Responsiveness, Digestion, Excretion, Metabolism, Reproduction, Growth
a. Read these in your textbook, and note how they fit in with the previous material in these Notes on the
Web.
b. Example: boundaries are required to maintain safe internal conditions for homeostasis. This would fall
under the general property of homeostasis.
c. Example: responsiveness (=irritability) is the ability to respond to external and internal stimuli. This is
also required to maintain homeostasis.
d. Example: excretion is required to keep from... well... filling up with nasty waste! This is also required to
maintain homeostasis.
e. Examples: other "life functions" listed by Marieb are directly described previously (e.g. metabolism).
Read and learn the materials in the Notes on the Web and the brief materials in your text on all of these.
C. Survival Needs as Listed in Marieb - Nutrients, Oxygen, Water, Normal Body Temperature,
Atmospheric Pressure
1. As with the "life processess" mentioned in "B" above, the survival needs described in your text fall
under previously discussed categories, particularly homeostasis. Nonetheless, learn the brief materials in
your text on these to add to our Notes on the Web.

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D. Aspects of Homeostatis Discussed in Marieb - Mechanisms, Negative Feedback, Positive Feedback,
Imbalances.
1. As with the previous sections, these topics have been discussed in your Notes on the Web, however,
read and learn the material from your textbook to supplement our Notes on the Web.
E. Eleven body systems - integumentary, skeletal, muscular, nervous,
endocrine, cardiovascular, lymphatic/immune, respiratory, digestive, urinary,
reproductive. A major part of API and APII involve learning how these
various body systems contribute to the critical processes of life, including
homeostatis, of the normally functioning human body.
IV. Language of Anatomy
A. Anatomical Position - see textbook for images. Standup! Place yourself in the standard anatomical
position: face forward with your legs more or less parallel (feet slightly apart), your arms downward but
held slightly away from your hips, and your thumbs on the outside.
1. Note that descriptions of anatomy throughout our book and in our labwork, etc. use directional terms as
if the body was in the anatomical position.
2. Know all of the directional terms found in your text plus one additional one defined in the list below:
 superior versus inferior
 cranial versus caudal
 rostral - toward the nose (often used when studying the brain and other head
structures)
 ventral versus dorsal
 anterior versus posterior
 lateral versus medial
 intermediate
 proximal versus distal
 superficial versus deep
 external versus internal
Note that all of these directional terms are relative and may be used to describe relationships that are far
from the extreme ends of the body. For example, the knee is superior to the foot even though both are
inferior to the hip joint.
B. Regional Terms Used to Describe the Human Body
1. Major Divisions (two)
a. Axial (head, neck and trunk)
b. Appendicular (appendages and their connections to the trunk)
2. Regional Terms - Specific Area Terminology

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a. Examine and learn those labeled on the diagram in your book. You should learn the technical term and
may define it by the short common description found in parentheses after it
b. For the record, the following text box shows most of these terms. The terms required for you to commit
to memory at this time are shown in bold. The detailed subdivision terms you can learn as you go through
the body systems later. Some of these regions can be seen from the anterior view, some from the
posterior view, and some from both views.
 Cephalic
 nasal
 oral (=buccal)
 frontal
 orbital
 mental
 otic
 occipital
 Cervical
 Thoracic
 axillary
 sternal
 mammary
 Abdominal
 brachial
 antecubital
 Pelvic
 inquinal
 Pubic
 Upper Limb (= Upper Extremity)
 acromial
 brachial (arm)
 antecubital
 olecranal
 antebrachial (forearm)
 Manus
 digital (fingers)
 carpal
 metacarpal
 palmar
 Lower Limb (=Lower Extremity)
 coxal (hip)
 femoral (thigh)
 patellar
 politeal
 crural (leg)
 sural (calf)
 fibular or peroneal
 hallux
 umbilical
 Pedal
 tarsal (ankle)
 calcaneal
 metatarsal
 digital
 plantar
 hallux (big toe)
 Back (dorsum/dorsa)l
 vertebral
 scapular
 lumbar
 sacral
 gluteal
 perineal
C. Study of Non-human Mammals in Human Anatomy: An Explanation and Historical Note
A large proportion of human anatomy courses across the nation (and in Oklahoma) use non-human
mammalian dissection materials to help teach students understand human anatomy. You may wonder
why this is of educational value. Mammalian anatomy, particularly between certain mammal groups, is
amazingly similar... so similar that you would be challenged at first to distinguish between some organs
(e.g. kidneys, hearts, etc.) from a human and another mammal! In fact, the similarities can be so striking
that the famous Greek anatomist, Galen of the 2nd century AD, actually based much of his human
anatomy descriptions on non-human primates (e.g. apes). Galen could not always research internal
human anatomy by using cadavers so he used other closely-related species that were so similiar that no
one successfully challenged his accuracy for some fourteen centuries!
Human and ape anatomy are so similar that the Church did not realize the basis for Galen's excellent
research. The Church therefore adopted Galen's human anatomy writings as the final word (revealed from
God) without knowing that much of his work was actually based on the anatomy of apes! It wasn't until
1543 AD that Andreas Vesalius published his great human anatomy treatise, "De Humani Corporis
Fabrica," which finally cracked the dogmatic position of the Church and others on the details of Galen's
work. It was not a peaceful transition, and some were put to death for questioning Galen! Consider the
following quote from Moore (1993):

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Initially Vesalius had much opposition, since even suggesting that such an ancient and respected
authority as Galen might have erred was not in the best of taste. One brave, free spirit who suffered
because he thought otherwise was Michael Servetus (1511-1553), a scholar of broad interests, mainly
theological, but also a serious student of Galen. In the course of his studies, he came to the conclusion
that Galen was not correct in all matters. Servetus hypothesized, for example, that blood does not pass
directly through those Galenic pores from right ventricle to the left but instead goes from the right ventricle
to the lungs, where it picks up air, and then back to the left ventricle. Mainly because he questioned Galen,
whom the Church had named as the authority on anatomy and physiology, Servetus was captured while
at prayer and, after a brief trial, was sent up in flames on October 27, 1553. Lest the reason be in doubt,
one of his offending books was hung from his neck so it too was consumed on the pyre.
Now you can realize that honorable people have actually sacrificed their lives in order to find the scientific
truth of human anatomy! You should also now realize the great educational value that you can gain by
conscientiously studying the non-human, mammalian specimens we will explore in some of our lab
sessions. Specifically, we will dissect minks for muscles and sheep brains for the nervous system. Also,
some histological slides used to study microscopic anatomy will be from non-human mammals.
D. Anatomical Variability
It is important to understand that each individual varies in many details of anatomy and physiology. This
fact often passes by the beginning student of human anatomy. They examine the drawings and figures in
their textbooks and wonder, "Why can't we just learn this on the diagrams?" "Why do we have to identify
these structures on the a specimen?" The answer, in part, is that the diagrams do not look exactly like the
real thing! Your textbook authors, Marieb and Hoehn (2007), state that about 90% of structures will fit a
"textbook description." This means that 10% do not! Study of actually specimens and the ability to identify
structures on multiple specimens of the same organ (for example) are required for the student to
understand anatomy at a deeper level.
E. Body Cavities and Membranes
1. Dorsal Body Cavity - central nervous system cavities both of which are continuous with one another
a. cranial cavity - brain
b. vertebral (=spinal) cavity - spinal cord
2. Ventral Body Cavity - houses visceral organs
a. thoracic cavity - portion above the diaphram and within the ribs and muscles of the chest
 pleural cavities - lungs
 mediastinum - esophagus, trachea, and others along with the pericardial
cavity housing the heart
b. abdominopelvic cavity - below the diaphram
 abdominal cavity - stomach, intestines, spleen, etc.
 pelvic cavity - protected by bony pelvis and containing the urinary bladder,
some reproductive organs, and the rectum
3. Membranes of the Ventral Body Cavity - thin double-layered tissue linings called the serosa or serous
membrane

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a. parietal serosa - lines walls
 parietal pericardium - heart
 parietal pleura - lungs
 parietal peritoneum - abdominopelvic
b. visceral serosa - surrounds (adheres to surface of) organs
 visceral pericardium - heart
 visceral pleura - lungs
 visceral peritoneum - abdominopelvic
c. serous fluid - reduces friction and contains white blood cells that help remove abrasive materials to
keep the fluid clean.
F. Abdominopelvic Quadrants - note superficial organs found in each as shown in your text. You do not
have to memorize these at this time.
a. right upper quadrant
b. left upper quadrant
c. right lower quadrant
d. left lower quadrant
G. Other Body Cavities - know the oral and digestive, nasal, orbital, middle ear, and synovial cavities as
described in your text. (You do not have to memorize these at this time.)
V. Medical Imaging - Review these various incredible tools. Only three will included as testing material,
but you will benefit from having a bit of knowledge about all of them. The three to learn now are: Postitron
Emission Tomography (PET), Sonography (ultrasound imaging), and Magnetic Resonance Imaging (MRI).
Reminder about Textbook Study
As with other topics, your textbook has excellent presentations of the materials on the introduction to
anatomy and physiology. While you should focus on the specific material in the Notes on the Web, you
should always use your textbook as a resource for illustrations and for understanding content that your
notes cover. Check the general objectives above to make sure that you have covered all of the topics in
the textbook readings.
As with all materials throughout the semester, you will have opportunities to ask questions or ask that any
relevant material from your assignments be discussed in class.

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Histology and Cell Structure
Some knowledge of cell structure is usually required for introductory courses in Human Anatomy and Physiology (e.g. ITEC),
Human Biology (e.g. A-Level) and other first-level courses in health sciences and related subjects.
This page includes the basic structure of a general human cell (i.e. an animal cell rather than a
plant cell) and some of the organelles within it.
Histology
Histology is the microscopic study of the structure of tissues using special staining
techniques combined with light and electron microscopy. The detail of even the general cell
structure summarised below cannot be observed without the use of these modern techniques.
Cell Structure
The structure of cells varies according to the type and purpose of the cell (for example, which
functions it is performing and in which part of the body).
All cells contain organelles.
These are structures within the cell that are specialised for particular functions.
The following diagram illustrates a single cell and simple representations of key organelles:

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It is also important to know something about each of these organelles:
Organelle Structure/Function
Cell Membrane The cell membrane keeps the cell together by containing the organelles within
it. Cell membranes are selectively-permeable, allowing materials to move both
into and outside of the cell.
Centrosomes The centrosomes contain the centrioles, which are responsible for cell-
division.
Cytoplasm Cytoplasm is a jelly-like substance that is sometimes described as "the cell-
matrix". It holds the organelles in place within the cell.
Goli Apparatus The goli apparatus of a cell is usually connected to an endoplasmic
reticulum (ER) because it stores and then transports the proteins produced in
the ER.
Lysosomes Lysosomes are tiny sacs filled with enzymes that enable the cell to utilize its
nutrients. Lysosomes also destroy the cell after it has died, though there are
some circumstances (diseases/conditions) in which lysosomes begin to
'break-down' living cells.
Microvilli "Microvilli" is the pural form; "Microvillus" is the singular form.
Microvilli are finger-like projections on the outer-surface of the cell.
Not all cells have microvilli.
Their function is to increase the surface area of the cell, which is the area

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through which diffusion of materials both into, and out of, the cell is possible.
Mitochondria "Mitochondria" is a plural term; which is appropriate as these are not found
alone. The quantity of mitochondria within cells varies with the type of cell.
These are the energy producers within the cell. They generate energy in the
form of Adenosine Tri-Phosphate (ATP). Generally, the more energy a cell
needs, the more mitochondria it contains.
Nuclear Membrane The nuclear membrane separates the nucleus and the nucleolus from the rest
of the contents of the cell.
Nuclear Pore Nuclear pores permit substances (such as nutrients, waste, and cellular
information) to pass both into, and out of, the nucleus.
Nucleolus The nucleolus is responsible for the cell organelles (e.g. lysosomes,
ribosomes, etc.).
Nucleus The nucleus is the "Control Center" of the cell, which contains DNA (genetic
information) in the form of genes, and also information for the formation of
proteins.
Information is carried on chromosomes, which are a form of DNA.
Ribosomes Ribosomes interpret cellular information from the nucleus and so synthesize
appropriate proteins, as required.
Rough Endoplasmic
Reticulum (RER)
"Rough" indicates that there are ribosomes attached to the surfaces of the
endoplasmic reticulum. The endoplasmic reticulum is where proteins and
lipids are produced within the cell, and is also concerned with the transport of
these materials within the cell.
Smooth Endoplasmic
Reticulum (SER)
"Smooth" indicates that there are no ribosomes attached to the surfaces of
the endoplasmic reticulum.The endoplasmic reticulum is where proteins and
lipids are produced within the cell, and is also concerned with the transport of
these materials within the cell.
Other components of a typical cell not shown on the above simple diagram include:
Cilium; Cytosol (component of cytoplasma); Glycogen granules; Intermediate filament; Microtubule;
Microfilament; Pericentriolar area (around the Centrioles); Peroxisome; Secretory vesicle.

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Cell Membrane
A simple representation of the structure of animal cell membranes is shown below.
This is illustrates a cross-section of the
phospholipid bilayer that forms the
membrane around the outside of all
animal (including human) cells.
This plasma membrane consists mainly
of phospholipids and proteins, most of the
membrane proteins being glycoproteins.
The two components of the phospholipids
are the
heads (represented by black circles), and
the
fatty acid tails (that extend into the
phospholipid bilayer).
Other molecules present in the plasma
membrane generally include cholesterol
(as illustrated) and glycolipids.
Note that this membrane is non-rigid; if it
had a cell-wall then it would be rigid - but
a plant cell !
Integral Proteins extend through the bilipid layer and among the fatty acid tails of the phospholipids -
though not necessarily all the way through the plasma membrane.
.

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Introduction to Cell Division
This follows the page about the structure of an animal cell.
Living cells divide to form new cells in order to repair worn-out or damaged tissues throughout
an organism, and (in the gametes only) to enable the exchange of genetic material at the initial
stage of the process of sexual reproduction. (A gamete is a mature sex cell, specifically the ovum
of the female or the spermatozoon of the male.)
The two types of cell division are generally called mitosis and meiosis but, strictly, these terms
refer to the stages of division of the cell nucleus for somatic (non-reproductive) and reproductive
cells, respectively.
Definition of Mitosis
Mitosis is the type of cell division by which a single cell divides in such a way as to produce two
genetically identical "daughter cells". This is the method by which the body produces new cells
for both growth and repair of aging or damaged tissues throughout the body.
Mitosis is also referred to as "binary fission". Further detail about the process of mitosis is
included on the page about mitosis, and also on the illustrations of mitosis.
Definition of Meiosis
Meiosis, which is also referred to as "reduction division", is the form of cell division in which
a cell divides into four "daughter cells" each of which has half**
of the number of
chromosomes of the original cell. Meiosis occurs prior to the formation of sperm (in males)
and ova (in females). That is - meiosis only occurs in the "gametes".

16. 16 | P a g e
**
The cells return to having the normal (called "diploid") number of chromosomes after
fertilization of the ova by the sperm.
Meiosis consists of two successive divisions, each of which is divided into four phases. The first
meiotic division is similar to mitosis (defined above) and the second meiotic division is the
"reduction" stage.
Meiosis enables the exchange of genetic material between chromosomes.
Further detail about the process of meiosis is included on the page about meiosis.
Definitions:
Before studying the pages about the processes of mitosis and meiosis, it is useful to understand
the following terms:
Chromosome
A chromosome is a thread-like structure found in the nucleus of cells.
Chromosomes are composed of a long double filament of DNA (deoxyribonucleic acid) coiled
into a helix together with associated proteins. Genes (the most basic units of genetic material)
are arranged in a line along the length of chromosomes.
The nucleus of each human somatic cell (i.e. those relating to the nonreproductive parts of the
body) contains 46 chromosomes - 23 of maternal origin (from the mother) and 23 of paternal
origin (from the father).
Diploid
The word "diploid" is an adjective that may be used to describe cells, nuclei or organisms in
which each chromosome (except the Y sex chromosome) is represented twice, a situation
sometimes summarised as 2n. This is better understood when compared with the term
"haploid":
The word "haploid" (and also the word "monoploid") is an adjective that may be used to
describe cells, nuclei or organisms that contain a single set of "n" unpaired chromosomes.
An example of use of these adjectives is: "In the case of the human species, the gametes are
haploid following meiosis."
But what is n ?
n is a number that varies according to species. In the human species, n=23, therefore there are
46 chromosomes in all human body parts except for the gametes, which contain only 23.
Chromatid
The simplest complete definition of a chromatid is that it is one-half of a replicated

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chromosome.
The more detailed version is that a chromatid is one of two identical strands of DNA that,
together, form a chromosome - each chromosome being composed of two sister chromatids
joined together at a centromere.
The term "chromosome" applies provided that the centromeres remain in contact. When the
centromeres separate (during anaphase of mitosis and anaphase 2 of meiosis), the strands
previously called "chromosomes" are referred to as "daughter-chromosomes".
Centromere
A kinetochore is another term for a centromere.
A centromere (or "kinetochore") is the part of a chromosome at which the two chromatids (see
above) are attached together. This (centromere) becomes attached to the spindle during mitosis
and meiosis.
When chromosome division occurs the centromere divide longitudinally.
The Digestive System - Introduction
Understanding the human digestive system consists of knowledge of the following aspects and
how they interact with each other.
 The names and locations in the body of the organs of the digestive system.
 The digestive process (overview).
 The passage of matter through the digestive system,
that is the digestive process(es) by which foodstuffs are broken down at key stages along the
alimentary canal.
 The structure and functions of the main parts (organs) of the digestive system - considering
each organ individually.
 The chemical break-down of food,
that is how each of the important components of food (food groups) is processed by the body,
including the basic chemistry of these processes.
 Recognising and understanding the causes and effects of the most common disorders of the
digestive system.
Key learning objectives are highlighted in bold-green text in the above list and are described
here on pages (or series of pages), links to which appear in the index-list on the left.

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Use the interactive diagram above to learn and remember the main structures of the digestive
system.
The human digestive system can be described in two parts, they are the components of the
alimentary canal (see "Transit through the alimentary tract") and the
accessory organs.
About the Alimentary Canal About the Accessory Organs
The "alimentary canal" is also known as the
"alimentary tract". It is a tube of approx. 9m
long (in total, in an adult) that passes from
the mouth to the anus and includes the
following parts:
 mouth
 throat
 oesophagus (sometimes
labeled"esophagus")
 stomach
 small intestines
 large intestines
 rectum
 anus
Organs, glands, and tissues that assist the
digestive process, e.g. by supplying
fluids/chemicals, but which ingested
material does not actually pass through may
be referred to as accessories (to the
digestive process/system). These include:
 teeth
 tongue
 salivary glands (parotid,
submaxillary, sublingual)
 liver
 gallbladder
 pancreas
Note that the appendix is not mentioned in either of the two categories above because is is a
'vestigial organ', which means that (although it is thought to have been useful to distant
ancestors of our species), the appendix does not play an active role in the digestive process. It is
included in descriptions of the digestive system because it is attached to the large
intestine. It is useful to know about the appendix to study conditions & disorders
of the digestive system, among which appendicitis is often included.
Notes about the Locations of Parts of the Digestive System:
The locations of parts of the human digestive system are shown above but might not be
completely clear from the diagram because these tissues and organs over-lap when drawn (in 2-
dimensions). This is unavoidable because some parts are located in front of / behind other parts -
as well as above, below, etc.. The following notes are therefore included for clarification:
Teeth - The teeth are located inside the mouth - which is also known as the
"buccal cavity".

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Humans have two sets of teeth, the first during childhood and the second set
(ideally) throughout adult life. The lower row of teeth are inset into the
mandible (lower jaw bone) and the upper row of teeth are inset into the
maxillae (upper jaw bones).
Tongue - The tongue is located at the floor of the mouth between the two lateral
portions of the mandible (lower-jaw). The base of the tongue is connected to
the midline of the floor of the mouth by a fold of membrane called the
lingual frenulum and is controlled by several muscles including the
hyoglossus.
Salivary
Glands
- The salivary glands are located in the lower part of the face and secret
into the buccal cavity.
There are 3 main salivary glands:
(1) The parotid gland is the largest salivary gland and is located on the
side of the face immediately below and anterior to the external ear.
(2) The submaxillary gland is located below the jaw towards the
front of the neck/lower-jaw.
(3) The sublingual gland is the smallest salivary gland and is located
below the mucous membrane of the floor of the mouth. It is narrow and has a
flatten shape, resembling an almond.
Epiglottis - The epiglottis is the flap of cartilage located at the back of the throat
behind the tongue, and in front of the larynx.
Trachea - The trachea is not part of the digestive system but is included on the above
diagram to clarify the action of the epiglottis, which acts as a "switch" -
directing foodstuffs / air from the buccal cavity into either the oesophagus
(leading to the stomach) or the trachea (leading to the lungs).
Oesophagus - The oesophagus is a muscular canal that extends from the throat at the
back of the mouth to the stomach.
Diaphragm - The diaphragm is a thin musculo-fibrous septum that is not part of the
digestive system but is included above because it separates the thorax
(containing e.g. the lungs) from the abdomen (which contains much of the
digestive system, as shown). The diaphragm divides these two bodily
cavities, forming the floor of the thorax and the roof of the abdomen.
Stomach - The stomach is located between the lower end ("termination") of the
oesophagus and the start of the small intestines - at which the
pylonic sphincter of the stomach releases contents of the stomach
into the duodenum (the first and upper-most part of the small
intestines).
Liver - The liver is located in the upper right-side of the abdominal cavity (i.e.
immediately below the diaphragm). It is divided into two lobes, the left-lobe
being smaller than the right-lobe.
Note that the diagram above shows the liver on the left-hand-side because it

20. 20 | P a g e
is a diagram of the anterior view of the digestive system - that is looking at
the front of a person, hence the left-hand-side of the diagram represents the
right-hand-side of the body.
Gall Bladder - The gall bladder is an approx. cone-shapes musculo-membranous sac
located in a fossa under the right-lobe of the liver.
Pancreas - The pancreas is located behind the stomach and partly within the curve
of the duodenum.
Note that the diagram above appears to show the pancreas in front of the
stomach (given that the diagram above is an anterior view of the digestive
system) and does not explicitly show the pancreas lying partly within the
curve of the duodenum. Unfortunately this is unavoidable when including all
of the main digestive organs in this diagram because an ordinary anterior
view would not include anything behind something else included in the same
view. We have therefore included the pancreas (represented in a pale colour)
apparently in front of the stomach - with this note in clarification.
For a clearer representation of the location of the pancreas partly within the
curve of the duodenum, see the main/largest diagram on the page about
passage through the alimentary tract - a small version of
which also appears at the top-right of this page.
Small
Intestines
- The small intestines are located in the lower part of the abdomen,
within the large membrane known as the peritoneum (which has 2 layers
separated by a small amount of liquid, enabling the organs contained within
it to move freely over and around each other). The small intestines progress
from the pyloric sphincter, through with they receive material from
the stomach, into the first of three parts - called the duodenum. The
next two parts of the small intestines are the jejunum and the ileum.
Large
Intestines
- The large intestines are located in the lower part of the abdomen,
within the large membrane known as the peritoneum (which has 2 layers
separated by a small amount of liquid, enabling the organs contained within
it to move freely over and around each other). The large intestines begin at
the bottom of the abdomen, where material is received from the ileum, i.e.
the final part of the small intestines. In common with the small intestines, the
large intestines are also described in three parts:
(1) The cecum is the first part of the large intestine and so receives
material from the ileum.
(2) The second part of the large intestines is the colon, which initially rises
upwards within the abdomen (ascending colon), then moves across
the body beneath the liver and stomach (transverse colon), then
finally passes downwards back to the lower abdomen (descending
colon).
(3) The third and final part of the large intestines is the rectum - also

21. 21 | P a g e
described separately - which is located in the approx. centre of the lower
abdomen.
Appendix - The appendix extends from the cecum, forming a narrow tube that
may pass in any of several directions, incl. e.g. upwards behind the cecum, to
the left behind the ileum, or downwards and inwards. The appendix varies in
length from approx 25mm to 220mm (in adults), typical length approx.
75mm. The appendix is held in position by an approx. triangular fold of
peritoneum.
Rectum - The rectum is the terminal (i.e. end) part of the large intestine and
extends from the sigmoid flexure to the anal orifice. It is approx. 12-20cm or
5-8 inches long in total - estimates in textbooks vary - and may be described
in three parts, according to the curve formed by this final part of the large
intestine. The three parts have approx. proportions 10cm, 7.5cm, and 2.5 -
4cm (the last part being slightly longer in men than in women), or values in
similar proportions for recta of slightly different total length.
The rectum ends at the anus, from which indigestible matter is released
from the body during defecation.
Anus - The anus is located at the base of the abdomen.
The Functions of the Liver (Digestive System)

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This follows the pages about an introduction to the liver and the anatomy of the liver.
Reminder about the Liver:
The liver is an accessory organ within the human digestive system. This means that it assists with the
digestive processes, e.g. by supplying substances useful to the digestive process - but that ingested
material (i.e. food and drinks and the substances they are broken down into as they pass through the
digestive system) does not pass through the liver.
The liver has over 500 functions (only some of which are described on these pages).
The main functions of liver as an accessory organ within the human digestive system are:
1. The secretion of bile and bile salts, and
2. Phagocytosis of bacteria and dead or foreign materials.
These processes* are described below, followed by short summaries of some of the other
functions of the liver.

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Main Functions of the Liver - For Digestion
1.
Secretion of
bile and bile
salts
Bile: Liver cells called hepatocytes secrete bile, which is a a
yellow/green (though may appear as dark as brown) slightly alkaline
liquid.
Bile Salts are also produced produced by the liver.
2.
Phagocytosis
of bacteria
and dead or
foreign
materials
Within the liver, blood passes through spaces called sinusoids -
instead of through capillaries (as elsewhere in the body). A special
type of cell called Kupffer's Cells, which are also known as stellate
reticuloendothelial cells, are located in the sinusoids and destroy many
types of unwanted particles present in the bloodstream through the liver.
Such particles include:
 bacteria,
 antigens, i.e. other substances from outside of the body
(sometimes called "foreign matter"),
 imperfect or no-longer functioning blood cells
(e.g. damaged leucocytes and erythrocytes).
Other Important Functions of the Liver (Not specifically concerning Digestion)
3.
Carbohydrat
e metabolism
(also
Maintenance
of normal
blood glucose
level)
Recall that the general breakdown of carbohydrates is:
Carbohydrates Polysaccharides
Glucose, which is then converted to:
 Energy
 Glycogen
(i.e. Stored Energy)
 excess to Fat
(Adipose Tissue)
Maintenance of normal blood glucose level:
 When blood glucose is low the liver breaks stored glycogen down into
glucose, for release into the blood stream.
 The liver converts certain amino acids and lactic acid into glucose.
 The liver can convert some other sugar molecules (e.g. fructose,
galactose) into glucose.
 When blood glucose is high the liver converts glucose to glycogen and
triglycerides (for storage).
4.
Lipid ("Fat")
metabolism
Liver cells called hepatocytes perform several important roles concerning
fat ("lipid") cells.

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These include:
 Break-down of fatty acids - generating adenosine triphosphate (ATP),
which is important for the contraction and relaxation of muscles.
 Synthesis of lipoproteins, which are important for the movement of fatty
acids, cholesterol ans triglycerides to and from cells.
 Storage of certain triglycerides
 Synthesis of cholesterol (as well as using cholesterol to produce bile
salts).
5.
Protein
metabolism
Liver cells called hepatocytes perform important roles re. the processing
of protein cells.
These include:
 Synthesis of all plasma proteins except for -globulins.
Plasma proteins produced in the liver include:
albumin, lipoprotein, transferrin, caeruloplasmin, globulins (but not -
globulins), -antitrypsin, -fetoprotein, fibrinogen, prothrombin, Factors
V, VII, IX, X and XII, and XII.
 De-amination of excess amino acids, i.e. removal of the -NH2 part
(called the "amino group") from amino acids, enabling the remaining
parts to be re-used, e.g. for conversion to ATP, carbohydrates, or fats.
 Conversion of the ammonia (NH3) resulting from the de-amination of
excess amino acids, into urea (via the ornithine cycle). That urea is
ultimately excreted from the body as a part of urine.
This is an important detoxification process because ammonia is more
toxic than the urea it is converted to, for subsequent excretion via the
urinary system.
6.
Processing
drugs
The liver can detoxify substances such as alcohol - but is considered to be
adversely affected by consumption of excessive quantities of alcohol over
extended periods of time.
The liver is also understood to process various common drugs, e.g.
penicillin, into bile.
7.
Processing
hormones
The liver is able to chemically change "process" certain hormones,
such as thyroid hormones and steroid hormones e.g. estrogen and
aldosterone.
6. and 7. are identified in different ways in different textbooks and other teaching materials.
E.g. They may be described (collectively) as "biotransformation" and, in some cases as
"de-toxification" processes.

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8.
Excretion of
bilirubin
Bilirubin ia a component of bile, which is produced by the liver.
The source of bilirubin is the heam of aged (i.e. no-longer optimally
functioning) red blood cells, which also known as erythrocytes.
Following the liver secreting bilirubin as part of the fluid bile, it is
eventually removed from the body (i.e. excreted) because most of the
bilirubin in the bile is then metabolised by bacteria in the small
intestines, then eliminated from the body in the faeces.
9.
Storage of
vitamins and
minerals
The liver stores several important chemicals, then releases them when
they are needed somewhere else in the body. Such chemicals include:
 Glycogen,
 The fat soluble vitamins (A, D, E and K), the liver being the location of
the body's main store of these.
 Vitamin B12
 Minerals: Iron (Fe) and Copper (Cu).
10
.
Activation of
vitamin D
The liver is one of the parts of the body that, together with the skin and
the kidneys, participate in forming the active form of vitamin D.
(Vitamin D is necessary for absorption of the minerals calcium and
phosphorous, and for regulation of the permeability of cell
membranes.)
11
.
Protection
(of the body)
Several processes that occur in the liver can be described as protecting the
body, especially e.g. by helping to remove substances that will not serve a
useful purpose. Some such processes are already mentioned above - such
as phagocytosis (2.) and detoxification (incl. in 5. and 6.).
Another protective process performed by the liver is the filtration of portal
blood, which removes certain toxins and microorganisms from the blood
before it re-enters systemic circulation.
12
.
Haematopoie
sis
Haematopoiesis is the formation of the cellular components of blood.
The liver is the main site of embryonic haematopoiesis.
However, this function of the liver ceases before birth (bone marrow
having been supplementing the haematopoiesis performed by the liver
from about 5 months gestation).
* The numbers listed above are soley to aid memory and discussion of this page between viewers/visitors.
A healthy liver peforms these and many other functions, as needed, and in no particular sequence

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Classification of Tissue Types
This page is part of the section about the structure and function of different Tissue Types and indicates how the tissues
mentioned in this section may be described in relation to each other, e.g. Adipose Tissue, Areolar Tissue, Blood Tissue,
Bone Tissue etc. are all different types of "Connective Tissue". To read about the individual tissue types, see the links listed
on the left.
There are Four (4) Basic Types of Animal Tissue:
Type of
Tissue:
Epithelial
Tissue
Connective
Tissue
Muscular
Tissue
Nervous
Tissue
Functions
of type of
tissue:
Covers body
surfaces and
lines body
cavities
Binds and
Supports body
parts
Enables
movement of
structures within
the body and
movement of the
entire
person/animal
Enables
responses to
stimuli and
coordinates
bodily
functions
Each of the tissue-types listed in the panel on the left falls into one of the four categories above.
However, the four "Basic Types" of animal tissues can be sub-divided further as each includes
several different sub-types of the tissue, each being specialised to meet specific needs and/or
perform particular tasks.
1. Epithelial Tissue
Epithelial tissue exists in many forms and can be classified or sub-divided in different ways.
Types of Epithelial Tissue:
Types of Epithelial Tissue
(in this classification)
Covering and Lining Epithelial Tissue
Classification by Cell Shape:
Squamous
Cuboidal
Columnar
Transitional
Classification by Arrangement of Layers:

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Simple Epithelium Simple squamous epithelium,
Simple cuboidal epithelium,
Nonciliated simple columnar
epithelium,
Ciliated simple columnar epithelium.
Stratified Epithelium Stratified squamous epithelium,
Stratified cuboidal epithelium,
Stratified columnar epithelium,
Transitional epithelium.
Pseudostratified columnar
Epithelium
Pseudostratified columnar
epithelium.
Glandular Epithelial Tissue
Endocrine Glands (Tissue of) Endocrine Glands
Endocrine Glands (Tissue of) Exocrine Glands
Each of the sub-divisions of epithelial tissue identified above can be described in terms of its
structure (using both text and diagrams), location, and function within the body.
2. Connective Tissue
Connective tissues serve the general purpose of supporting and connecting the tissues of the body,
and vary considerably in structure and composition. Teaching materials (incl. textbooks and
websites) sub-divide this tissue category in various different ways - hence it is useful to be aware
of variations and overlap in classifications and terminology.
Types of Connective Tissue:
Embryonic Connective Tissue
Mesenchyme
Mucous connective tissue
Mature Connective Tissue
Loose Connective Tissue:
Areolar Tissue
Adipose Tissue
Reticular Tissue

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Dense Connective Tissue:
Dense Regular Connective Tissue
(White Fibrous Tissue)
Dense Irregular Connective Tissue
Elastic Connective Tissue
(Yellow Elastic Tissue)
Cartilage Tissue:
Hyaline Cartilage
Fibrocartilage
Elastic Cartilage
Bone (Osseous)
Tissue:
Compact Bone
Spongy Bone
Blood Tissue:
Erythrocytes
Thrombocytes
Leucocytes
Lymphatic Tissue:
Lymph
3. Muscular Tissue
There are three (3) types of muscular tissue:
Skeletal
Muscle
located throughout the body and under conscious (i.e.
"voluntary") control, main function movement of the structures of

29. 29 | P a g e
(Tissue) - the body, and the body as a whole, e.g. by walking, running, etc..
More about Skeletal Muscle [in the Glossary].
Cardiac
Muscle
(Tissue) -
which is found only in the heart and is important for effective
blood-flow through the heart.
More about Cardiac Muscle [in the Glossary].
Smooth
Muscle
(Tissue) -
involuntary muscle tissue located around the walls of many
internal structures such as the stomach and intestines and
important for aiding the passage of materials/fluids through those
structures.
More about Smooth Muscle [in the Glossary].
4. Nervous Tissue
Nervous tissue consists of two (2) main types of cells:
Nerve Cells
(also known as Neurons or
Neurones) -
whose purpose is to transmit (electrical)
nerve impulses that move information
around the body.
.
Neuroglia
(also known as simply Glia) -
which support and protect nerve cells,
depending on the particular type of glia.
Examples of types of glia include
astrocytes, ependymal cells, microglial
cells, oligodendrocytes and Schwann cells.

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The Structure and Functions of Bones
Introductory Note: Knowledge of the structure and function of bones and aspects of skeletal system generally are essential
parts of training in human biology, medicine and associated health sciences. This page is intended to include the detail
required for most Basic / First Level Courses in many therapies, and some ITEC Diplomas.
This page is divided into the following sections:
1. The Functions of The Skeleton
generally - as opposed to the functions of particular bones.
2. Types of Bones
with examples.
3. The Structure of Bone
with diagram and definitions.
1. Functions of The Skeleton
1.
Support
The skeleton is the framework of the body, it supports the softer tissues and provides
points of attachment for most skeletal muscles.
2.
Protection
The skeleton provides mechanical protection for many of the body's internal organs,
reducing risk of injury to them.
For example, cranial bones protect the brain, vertebrae protect the spinal cord, and the
ribcage protects the heart and lungs.
3.
Assisting in Movement
Skeletal muscles are attached to bones, therefore when the associated muscles contract
they cause bones to move.
4.
Storage of Minerals
Bone tissues store several minerals, including calcium (Ca) and phosphorus (P). When
required, bone releases minerals into the blood - facilitating the balance of minerals in
the body.
5.
Production of Blood Cells
The red bone marrow inside some larger bones (including, for example, the ....) blood
cells are produced.

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(Red Blood Cells, White Blood Cells and Platelets are described on the page:
Structure & Functions of Blood.)
6.
Storage of Chemical Energy
With increasing age some bone marrow changes from 'red bone marrow' to 'yellow bone
marrow'.
Yellow bone marrow consists mainly of adipose cells, and a few blood cells. It is an
important chemical energy reserve.
2. Types of Bones
There are axial and appendicular bones.
(The appendages are the arms and
legs, which contain approx. 30 bones
each.)
There are typically 22 bones in the head.
There are 33 bones in the spine.
These include:
7 cervix (neck);
12 thorax;
5 lumbar;
5 sacral;
4 coccyx.
The pelvic girdle is fused to the sacrum
at the sacro-illiac joint.
The pelvis is the part that is added onto
the spine.
The thorax (chest) consists of 12 pairs of
ribs:
7 pairs 'true' ribs (joined directly to the
sternum ("breast-bone"));
3 pairs 'false' ribs (joined to the
sternum ("breast-bone") by cartilage);
2 pairs 'floating' ribs (not connected to
the sternum ("breast-bone") at all,
connected to the diaphragm.;
The shoulder girdle consists of the scapula (shoulder blade) and the clavicle ("collar bone").

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The following table summarises the five main categories of bones, together with another
category (sutural bones).
1.
Long bones:
"Long bones" have greater length than width and consist of a shaft and a variable number
of endings (extremities).
They are usually somewhat curved for strength.
Examples include femur, tibia, fibula, humerus, ulna and radius.
2.
Short bones:
"Short bones" are roughly cube-shaped and have approximately equal length and width.
Examples include ankle and wrist bones.
3.
Flat bones:
"Flat bones" have a thin shape/structure and provide considerable mechanical protection
and extensive surfaces for muscle attachments.
Examples include cranial bones (protecting the brain), the sternum and ribs
(protecting the organs in the thorax), and the scapulae (shoulder blades).
4.
Irregular bones:
"Irregular bones" have complicated shapes and so cannot be classified into any of the
above (shape-based) categories. Their shapes are due to the functions they fulfill within
the body e.g. providing major mechanical support for the body yet also protecting the
spinal cord (in the case of the vertebrae).
Examples include the vertebrae and some facial bones.
5.
Sesamoid bones:
"Sesamoid bones" develop in some tendons in locations where there is considerable
friction, tension, and physical stress. They may therefore form in the palms of the hands
and the soles of the feet, however their presence and quantity varies considerably from
person to person.
Examples common to everyone include the patellae (kneecaps).
6.
Sutural bones:
"Sutural bones" are classified by their location rather than by their shape. They are very
small bones located within the sutural joints between the cranial bones. The number of
sutural bones varies considerably from person to person, therefore these are un-named
bones.

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3. The Structure of Bone
Bones grow from their ends (extremities).
Under normal circumstances bones stop growing when the owner reaches his.her late teens or
early twenties.
Bone marrow (see diagram below) produces stem cells, such as erythrocytes (red
blood cells) and leucocytes (white blood cells).
Definitions of main types of bone tissue:
Compact (also known as "compact") tissue forms the outer shell of bones. It consists of a
very hard (virtually solid) mass of bony tissue arranged in concentric layers (Haversian
systems).
Cancellous (also known as "spongy") tissue is located beneath the compact bone and
consists of a meshwork of bony bars (trabeculae) with many interconnecting spaces
containing bone marrow.
Bone Markings / Features on Bones
Bone markings and the features of bones (including the correct words used to describe them) are
often required by first-level courses in human anatomy and associated health science
subjects. It is important to be familiar with the terminology used to refer to bone markings in
order to communicate effectively with professionals involved in healthcare, research, forensics,
and related disciplines.
The following terms used to describe bone markings or features on bones are in alphabetical
order with short definitions:
Word /
Term
(Bone Marking
or Feature)
Meaning / Description Type of
bone
marking
Example(s)
1. Angle A corner Feature of shape
of bone
Inferior angle (lower) and superior angle
(upper) are the rounded angles or "corners"
of the scapula.
2. Body The main portion of a bone The diaphysis of long bones such as the
humerus.
3. Condyle Rounded bump or large rounded
prominence. Such rounded
surfaces usually fit into a fossa
on another bone to form a joint.
Process - forms
joints
The medial condyle of the femur
(bone), upper-leg.
4. Crest Moderately raised and therefore
prominent border or ridge. Such
crests are often sites for a
Process - attach
connective
tissues
The iliac crest of the ilium (bone), which is
part of the hip.

34. 34 | P a g e
muscle attachment.
5. Diaphysis Shaft (main section) of a long-
bone
The long straight sections of e.g. the
humerus, fibula, tibia and femur.
6. Epicondyle Bump near a condyle; often give
appearance of a "bump on a
bump"; for muscle attachment
Process - attach
connective
tissues
The medial epicondyle of the
humerus, which is larger and more
prominent than the lateral
epicondyle (of the humerus bone).
7. Epiphysis The end part of a long bone
which usually has a larger
diameter than the shaft-part of
the bone (which is called the
diaphysis).
Articular part
(ends) of long
bones.
The proximal epiphysis (shoulder-end) and
the distal epiphysis (elbow-end) of the
humerus bone.
8. Facet A smooth flat articular surface.
Such flat surfaces may form a
joint with another facet or flat
bone.
Process - forms
joints
Facets (surfaces) of spinal vertebrae, e.g.
the superior articular facets of cervical
vertebrae.
9. Fissure Long, crack-line hole for blood
vessels and nerves
Channel-like
cleft or crack
The tympanomastoid fissure (also known
as the auricular fissure) separates the
tympanic portion of the temporal
bone from the mastoid portion of the
temporal bone and carries the
auricular branch of the vagus nerve through
the bone structure.
10. Foramen
(pl.
foramina)
Round hole through which blood
vessels, nerves or ligaments
pass.
Hole The foramen magnum of the
occipital bone at the base of the
skull.
Also vertebral foramina in the vertebrae of
the spine.
11. Fossa
(pl. fossae)
A shallow depression (the word
suggests "ditch" or "trench").
Such depressions in the surface
of bones often receive another
articulating bone with which a
joint is formed.
(Shallow)
depression
The mandibular fossa of the
temporal bone, forming part of
the skull behind the ear/s.
12. Head A rounded projection that forms
part of a joint (in combination
with a fitting part of an adjacent
bone) and is separated from the
shaft of the same bone by a
narrow portion (usually called a
"neck").
Process - forms
joints
Head of the femur at the top of the
femur (bone), upper-leg.
13. Line Similar to a crest but not raised
as much - may be relatively faint
Superior temporal line and inferior
temporal line on the outer surfaces of each
of the parietal bones of the
skull.
14. Margin Edge of a flat bone or flat portion
of the edge of a flat area
The supraorbital margin on the external
surface of the frontal bone forms
the upper boundary of the base of the orbit
(approx located on the upper surface of the
eye sockets towards the lateral sides so
upper-right of right eye and upper-left of left
eye).
15. Meatus A tube-like opening or channel Channel through External auditory meatus of the

35. 35 | P a g e
(pl. meati) extending within a bone. bone
temporal bone, forming the part
of the skull behind the ear.
16. Neck A section of bone (esp. of long
bones) between the "head" and
the "shaft" of the bone, the
"neck" of a bone is a narrowed
portion, usually located at the
base of the "head" of the bone.
Neck of the femur below the top "head" of
the femur (bone), upper-leg.
17. Notch A V-like depression in the
margin or edge of a flat area
Articulatory
surface
The radial notch of the ulna (inner bone
of the lower forearm) is a narrow, oblong,
articular depression on the lateral side of the
coronoid process; it articulates with the head
of the radius (outer bone of the lower
forearm).
18. Process A raised area or projection Process - attach
connective
tissues
The vertebrae have transverse process(es)
and spinous process(es) which are, in
general, more pronounced the lower the
position of the vertebrae down the spine.
19. Ramus
(pl. rami)
Curved portion of a bone, like a
ram's horThe trans
Curved surface The inferior pubic ramus and the superior
pubic ramus are features of the lower part
of the pelvis bone.
20. Sinus Cavity within a bone Cavity The sphenoidal sinuses are the semi-open
areas enclosed by the sphenoid
bone that act as drains from the nasal
cavity.
21. Spine or
Spinous
process
Similar to a crest but raised
higher; a sharp, pointed, slender
projection. Such sharp raised
projections called spines are
often sites for muscle
attachment.
Process - attach
connective
tissues
The spinous processes of vertebrae,
which together form the "spine" (backbone).
22. Sulcus
(pl. sulci)
Groove, crevice or furrow. Such
elongated depressions may
accommodate a blood vessel,
nerve or tendon.
Channel-like
depression
Sigmoid sulcus on the inner surface of the
mastoid portion of the temporal
bone(s) - which form part of the skull
(behind the ears).
23. Trochanter Large blunt bump-like projection
(larger than a tuberosity, which
is in turn larger than a tubercle)
Process - attach
connective
tissues
Only one human example: the greater
trochanter at the top of the femur
(bone), upper-leg.
24. Tuberosity Large rounded or oblong
projection that may look like a
raised bump. Such
rounded/oblong projections
called tuberosities are often sites
for muscle attachment.
Process - attach
connective
tissues
The deltoid tuberosity of the
humerus (bone), upper-arm.
25. Tubercle Small tuberosity that may also
be described as a round nodule
or warty outgrowth.
Process - attach
connective
tissues; can also
form articular
surfaces
The non-articular part of each rib tubercle
attaches to the ligament of the tubercle.
Note: This table lists bone markings and features on bones in alphabetical order. It is a numbered list because some
people find it easier to remember sets of information by also remembering how many of each type of item they have to recall.

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The Structure of Skin
Introductory Note: Knowledge of the structure of skin is essential for successful completion of accredited courses in many
bodywork therapies, such as Massage, Reflexology, Aromatherapy, Indian Head Massage, and others. In most cases the
structure of the skin is just a small part of a larger module, which typically also includes further details about the physiology of
these structures and also associated aspects of pathology. (Is is important for therapists to be aware of and able to recognise
common skin conditions as these may constitute "contraindications" - that is, reasons NOT to proceed with a treatment.)
The following diagram illustrates the basic structure of the skin, labelling key components.
It may be useful preparation for, and/or revision of, courses in bodywork therapies.
The components labelled in the above diagram include the following:
Click on the terms coloured pink for more information
 Adipose tissue;
 Artery;
 Blood capillaries;
 Capillary bed;
 Connective Tissue;
 Deep sensory receptor;
 Dermis; Epidermis;
 Erector muscle;
 Free nerve endings;
 Stratum Germinativum;
 Hair;
 Hair follicle;
 Hair shaft;
 Hypo-dermis;
 Nerve endings;
 Pore;
 Sebaceous Gland;
 Sebum;
 Stratum basale;
 Statum corneum;
 Stratum granulosum;
 Stratum lucidium;
 Stratum spinosum;
 Sub-cutaneous;
 Sweat gland;
 Vein.
Functions of the Skin
The main functions of the skin include:
1. Protection of the human body
2. Sensation i.e. transmitting to the brain information about surroundings
3. Temperature regulation
4. Immunity i.e. the role of the skin within the immune system
5. Enables movement and growth without injury
6. Excretion from the body of certain types of waste materials
7. Endocrine function e.g. re. Vitamin D

37. 37 | P a g e
It is useful to be able to describe each of the above functions of the skin in further detail with
examples and explanations of the mechanisms that apply in each case.
Function of the Skin Example(s) How does the skin perform this
function ?
What is/are the mechanism(s) ?
1. Protection
Of the body from:
 ultraviolet (UV)
radiation e.g. sun
damage
 dehydration
 microorganisms
e.g. bacterial
invasion
 mechanical trauma
/ physical injuries
 The physical/mechanical barrier
formed by the surface (stratum
corneum layer) of the skin.
 Mechanical strength of the tissues
that form the skin.
 Keratin - a type of protein that is found
in the skin.
 Melanin - a dark-coloured light-
sensitive pigment that is found in the
skin and that protects against
excessive amounts of ultraviolet (UV)
radition, usually coming from the sun.
2. Sensation
Pressure/touch,
heat/cold, pain
 Somatic sensory receptors
3. Temperature
Regulation
Retention or release of
heat - depending on
outide of body
temperature
 Release of sweat from sweat glands
followed by evapouration of sweat
from the surface of the skin (body)
 Regulation of blood flow to regions of
skin, especially the extremities of the
body (i.e. limbs / appendicular
skeleton)
4. Immunity
Destruction of
microorganisms &
interaction of skin with
the body's immune
system
 Langerhans cells (of the epidermis)
 Phagocytic cells
 Epidermal dendritic cells
5. Permits movement
& growth
Growth of body / bodily
tissues and adaptation of
contours of body/skin
during movement
 Elastic properties of skin (epidermis
and dermis)
 Recoil properties of the skin
(epidermis and dermis)
 Elastic properties of subcutaneous
tissue
 Recoil properties of subcutaneous
tissue
See the structure of skin for info
about layers of skin.

38. 38 | P a g e
6. Excretion
Excretion of water, urea,
ammonia and uric acid
 Waste products released from the
body via the surface of the skin,
regulated by the volume and
composition of sweat
7. Endocrine
Synthesis of Vitamin D  Vitamin D (strictly D3, as there are
different types of vitamin D) is made
when an organic chemical in the skin
called 7-dehydrocholesterol reacts
with UVB ultraviolet light - usually due
to natural daylight but could be from
articifical sources - that falls onto the
skin. Vitamin D3 is produced in the two
innermost layers of the skin - called
the stratum basale and stratum
spinosum.
However, it is important to also be
aware than excessive amounts of
ultraviolet light, especially over a
certain range of wavelengths, falling
onto the skin may lead to sunburn and
is also associated with an increased
risk of skin cancer - which may occur
later.
Note that the information above summarises the main functions of the skin only.
Different textbooksand websites list different numbers of "main functions" of the skin.
Coursework and exam questions often ask for a specific number of examples of functions of the
skin.
Generally, lists of functions of the skin such as in the table above are given in no particular order
but there may be an order of importance of functions of the skin (or "integumentary system") in
or for specific situations.
E.g. when playing badminton inside a leisure centre regulation of body temperature and
excretion of waste products from the body may be more important that synthesis of vitamin D
because the latter applies primarily in situations of natural daylight.

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The Structure and Functions of Blood
Note: Knowledge of the structure and function of blood and aspects of the heart and vascular system are part of training in
various therapies, (incl. e.g. Massage, Aromatherapy, Acupuncture, Shiatsu, etc.). This page is intended to include detail
suitable for introductory courses, and some ITEC Diplomas.
This page is divided into the following sections:
1. The Functions of Blood
(generally - as opposed to the functions of particular components of blood).
2. The Composition of Blood
(incl. the different types of blood cells and their properties and functions).
3. Process of Oxygenation of Tissues due to Circulation of Blood
4. Types of Leucocytes (White Blood Cells)
1. Functions of Blood
1.
Transports:
Dissolved gases (e.g. oxygen, carbon dioxide);
Waste products of metabolism (e.g. water, urea);
Hormones;
Enzymes;
Nutrients (such as glucose, amino acids, micro-nutrients (vitamins &
minerals), fatty acids, glycerol);
Plasma proteins (associated with defence, such as blood-clotting and anti-bodies);
Blood cells (incl. white blood cells 'leucocytes', and red blood cells 'erythrocytes').
2.
Maintains Body Temperature
3.
Controls pH
The pH of blood must remain in the range 6.8 to 7.4, otherwise it begins to damage cells.
4.
Removes toxins from the body
The kidneys filter all of the blood in the body (approx. 8 pints), 36 times every 24 hours.
Toxins removed from the blood by the kidneys leave the body in the urine.
(Toxins also leave the body in the form of sweat.)

40. 40 | P a g e
5.
Regulation of Body Fluid Electrolytes
Excess salt is removed from the body in urine, which may contain around 10g salt per
day
(such as in the cases of people on western diets containing more salt than the body
requires).
2. Composition of Blood
Blood consists of many components (constituents).
These include:
55%Plasma
45%Components, i.e. 'Blood Cells'.
Of these, 99% are erythrocytes (red blood cells) and 1% are leucocytes (white blood cells)
and thrombocytes (blood platelets).

41. 41 | P a g e
The following table includes further general information about the constituents of blood.
Structure Functions
Plasma
Normal blood plasma is 90-92 %
water.
This is the straw-coloured fluid in
which the blood cells are suspended,
and consists of:
The medium in which the blood
cells are transported around the
body (by the blood vessels)
and are able to operate effectively.
Helps to maintain optimum body
temperature throughout the
organism.
Helps to control the pH of the
blood and the body tissues,
maintaining this within a range at
which the cells can thrive.
Helps to maintain an ideal balance
of electrolytes in the blood and
tissues of the body.
Dissolved substances including
electrolytes such as sodium,
chlorine, potassiun, manganese,
and calcium ions;
Blood plasma proteins (albumin,
globulin, fibrinogen);
Hormones.
Erythrocytes
(Red blood
cells)
Immature erythrocytes have a
nucleus but mature erythrocytes
have no nucleus.
Carry oxygen (process described in
more detail - below).
Haem
Erythrocytes have a "prosthetic
group" (meaning "in addition to" -
in this case, in addition to the cell).
The active component of this
prosthetic group is Haem.
Haem relies on the presence of
iron (Fe).
Haem combines with oxygen to
form oxyhaemoglobin:
... continued in section
below.
Erythrocytes are eventually broken
down by the spleen into the blood

42. 42 | P a g e
pigments bilinubin and bilviridin,
and iron. These components are
then transported by the blood to
the liver where the iron is re-
cycled for use by new
erythrocytes, and the blood
pigments form bile salts. (Bile
breaks down fats.)
Have a longevity of approx. 120
days.
There are approx. 4.5 - 5.8 million
erythrocytes per micro-litre of
healthy blood (though there are
variations between racial groups
and men/women).
Leucocytes
(White blood
cells)
There are different types of
leucocytes (described in more
detail - below), classified as:
Granular: e.g. Neutrophils,
Eosinophils, Basophils.
Agranular (do not contain
granules): e.g. Monocytes,
Lymphocytes.
Major part of the immune system.
Have a longevity of a few hours to
a few days (but some can remain
for many years).
There are approx. 5,000 - 10,000
leucocytes per micro-litre of blood.
Trombocytes
(Platelets)
Blood platelets are cell fragments; To facilitate blood clotting - the
purpose of which is to prevent loss of
body fluids.
Disk-shaped;
Diameter 2-4 um
(1 micro-metre = 1 um =
0.000001m);
Have many granules but no
nucleus;
Have a longevity of approx. 5-9
days.
There are approx. 150,000 -
400,000 platelets per micro-litre of
blood.

43. 43 | P a g e
3. The Oxygenation of Blood
The oxygenation of blood is the function of the erythrocytes (red blood cells) and takes place in
the lungs.
The sequence of events of the blood becoming oxygenated (in the lungs) then oxygenating the
tissues (in the body) is as follows:
The Right Ventricle (of the heart) sends de-oxygenated blood to the lungs.
While in the lungs:
1. Carbon Dioxide diffuses out of the blood into the lungs, and
2. Oxygen (breathed into the lungs) combines with haemoglobin in the blood as it passes
through the lung capillaries.
Oxyhaemoglobin returns to the heart via the pulmonary vein and then enters the systemic
circulation via the aorta.
There is a low concentration of oxygen in the body tissues. They also contain waste products
of the metabolism (such as carbon dioxide).
Due to the high concentration of oxygen in the blood and the low concentration of oxygen in
the tissues,
... the high concentration of carbon dioxide in the tissues diffuses into the blood. (95% of
this carbon dioxide dissolves in the blood plasma.)
Blood returns from the tissues back to the heart via the superior vena cava (from the upper-
body) and the inferior vena cava (from the lower-body)

44. 44 | P a g e
4. Types of Leucocytes (White Blood Cells)
Further notes about the types of leucocytes identified above:
Lymphocytes:
The term "antigen" refers to something that is not
naturally present and 'should not be in the body'.
T Cells (lymphocytes) are activated by the thymus
gland.
B Cells (lymphocytes) are activated by other
lymphoid tissue. The 'B' indicates 'bone marrow'
cells.
Phagocytosis:
A phagocyte is a cell able to engulf and digest bacte
protozoa, cells, cell debris, and other small particles.
Phagocytes include many leucocytes (white blood ce
and macrophages - which play a major role in the bo
defence system.
Phagocytosis is the engulfment and digestion of bact
and other anigens by phagocytes.

45. 45 | P a g e
Both T-cells and B-cells:
(1) destroy antigens, and
(2) produce 'memory cells' and anti-bodies.
Basophils:
An increased (higher than usual) percentage of
basophils in the blood may indicate an inflammatory
condition somewhere in the body.
Neutrophils & Monocytes:
Neutrophils are the first leucocytes to respond to
bacterial invasion of the body. They act by carrying
out the process of phagocytosis (see opposite), and
also be releasing enzymes - such as lysozyme, that
destroy certain bacteria.
Monocytes take longer to reach the site of infection
than neutrophils - but they eventually arrive in much
larger numbers.Monocytes that migrate into infected
tissues develop into cells called wandering
macrophages that can phagocytize many more
microbes than neutrophils are able to.
Monocytes also clear up cellular debris after an
infection.
Eosinophils:
An increased (higher than usual) percentage of
eosinophils in the blood may indicate parasitic
infection somewhere in the body.
This is the end of this article but further information about blood vessels, the structure
and functions of the heart,
systemic circulation, and the vascular system generally are included on other pages of
this website.
Lymphocytes: Monocytes: *Basophils: *Neutrophils: *Eosinophils:
Approx. 24% of
leucocytes are
lymphocytes. These
produce anti-bodies and
include:
* T-Cells
* B-Cells
* Natural Killer Cells
Approx. 4% of leucocytes
are monoocytes. These are
also known as phagocytes.
They combat microbes by
the process of
phagocytosis.
60-70% of leucocytes are
basophils.
Diameter 10-12 micro-metres.
Phagocytosis. Destruction of
bacteria with lysozyme and
strong oxidants.
2-4% of leucocytes are
neutrophils.
Diameter 10-12 micro-
metres.
Combat the effects of
histamine in allergic
reactions;
Phagocytize antigen-antibody
complexes;
Destroy some parasitic
worms.
0.5-1% of leucocytes are
eosinophils.
Diameter 8-10 micro-
metres.
Liberate heparin,
histamine, and seratonin
in allergic reactions,
intensifying
inflammatory response.
* It is only possible to observe the differences between these by staining them.

46. 46 | P a g e

47. 47 | P a g e
Components of the Central Nervous System
This page summarises basic information about the main parts of the Central Nervous System
(which is sometimes referred to by its initials: "CNS").

48. 48 | P a g e
Component Function(s) Structure
Cerebellum Long Term Memory
Co-ordination (e.g. balance)
Muscle Tone
Movement
Posture
Maintenance of muscle tone, balance,
and the synchronization of activity in
groups of muscles under voluntary
control, converting muscular
contractions into smooth coordinated
movement.
However, it does not initiate
movement and plays no part in the
perception of conscious sensations or
in intelligence.
The cerebellum is the largest part of
the hindbrain.
It bulges back behind the pons varolii
and the medulla oblongata, and is
overhung by the occipital lobes of the
cerebrum. Like the cerebrum, it has an
outer grey cortex and a core of white
matter.
The cerebellum has three broad bands
of nerve fibres – the inferior, middle,
and superior cerebellar peduncles –
which connect it to the medulla, the
pons varolii, and the midbrain
respectively.
Cerebrospinal
Fluid (CSF)
Bathes the brain and spinal cord
Allows nutrients and waste
products to diffuse between the
blood and the brain/spinal cord.
Protects the nerves against
mechanical damage
Cerebrospinal fluid is also the subject
of
cranio-sacral therapy, which is a
huge subject in it's own right.
A clear watery fluid whose normal
contents include glucose, salts,
enzymes, and some white blood cells
(but no red blood cells).
This fluid moves within its cavity,
typically beating at 6-12 beats per
minute, though this can rise to 12-50
beats per minute (such as in the case
of a person who has a "pulsating"
headache).
Cerebrum The Cerebrum is also known as the
Cortex
(Cortex = Cerebrum), and is the
largest and most highly developed
part of the brain.
This is the ‘learning’ part of the brain,
and the seat of all intelligent
behaviour.
It is responsible for the initiation and
coordination of all voluntary activity
in the body and for governing the
functioning of lower parts of the
The cerebrum is composed of two
hemispheres separated from each
other by the longitudinal fissure in
the midline.
Each hemisphere has an outer layer
of grey matter, the cerebral cortex,
below which lies white matter
containing the basal ganglia. Nerves
of the cortex are arranged on the
outside surfaces as grey matter.
The corpus collosum is a massive
bundle of nerve fibers that connect

49. 49 | P a g e
nervous system. the two hemispheres - at the bottom
of the longitudinal fissure.
Hypothalamus The Hypothalamus is the "Receptor
Centre", and "Control Centre" of the
body.
It contains several important centers
controlling body temperature and
eating, and water balance. Examples
include osmo-receptors that balance
water/salt levels and control the
water content of the blood.
(See diagram opposite.)
It is also the Saiety Center (that is
concerned with "satisfaction"), for
things like hunger, thirst, sex.
It is also closely connected with
emotional activity and sleep, and it
functions as a center for the
integration of hormonal and
autonomic nervous activity through
its control of the pituitary secretions.
The posterior lobe of the pituitary
secrets two hormones:
A.D.H. (Anti-diuretic hormone,
as known as vasopressin – in
U.S.)
This works on the kidney tubules.
Secretion of ADH tells the
kidneys to re-absorb more water,
resulting in more concentrated
urine. Non-secretion of ADH
results in more peeing, and
weaker urine.
Oxytocin.
The region of the forebrain in the
floor of the third ventricle, linked
with the thalamus above and the
pituitary gland below.
Medulla
Oblongata
The functions of the medulla
oblongata concern the body's
involuntary processes, such as:
Breathing;
Heart-rate;
The medulla oblongata is the
extension within the skull of the upper
end of the spinal cord, forming the
lowest part of the brainstem.

50. 50 | P a g e
Swallowing;
Salivation;
Vomiting;
Blinking.
The cranial nerves VI – XII leave the
brain in this region.
The Meninges Mechanical protection of the Brain
and Spinal column.
The meninges consist of three parts,
the dura mater, the arachnoid mater,
and the pia mater.
The structures of these are mentioned
below.
Meninges -
Dura Mater
Outermost layer of mechanical
protection of the Brain and Spinal
column.
The outer-most layer of the meninges
is inelastic, tough, and thicker than the
other two layers.
Meninges -
Arachnoid
Mater
Middle layer of mechanical protection
of the Brain and Spinal column.
The inner two membranes are together
called the leptomeninges; between
them circulates the cerebrospinal
fluid.Meninges -
Pia Mater
Innermost layer of mechanical
protection of the Brain and Spinal
column.
Pons Varolii The pons varolii is the part of the
brainstem that links the medulla
oblongata with the thalamus.
Contains numerous nerve tracts
between the cerebral cortex and the
spinal cord, and several nuclei of grey
matter.
(The trigeminal nerves emerge from
the front surface of the pons varolii.)

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The Structure of Muscle
(and associated connective tissues)
Skeletal muscles consist of 100,000s of muscle cells that are also known as "muscle fibers".
These cells act together to perform the functions of the specific muscle of which they are a part.
This is possible due to the integration of the muscle with the other tissues and structures of other associated body
systems - especially the bones (skeletal system) or, in the cases of facial muscles, the skin
(integumentary system), and also the nerves (nervous system).
A general example of muscle and associated tissues is illustrated below.
Tissue Type: Periosteum Periosteum is the outer layer of bone (as illustrated below).
It is to this layer that ligaments and tendons are attached.
Tendon Tendons attach muscle to bone.
They are tough pale coloured (whitish) cords formed from many parallel bundles of
collagen fibres. Tendons are flexible (they bend around other tissues, changing
position as they move), yet inelastic.
Tendon sheath
(not illustrated
above)
Some tendons are surrounded by tubular double-layered sacs that are lined with
synovial membrane and contain synovial fluid. These structures are called "tendon
sheaths". Their purpose is to minimise friction associated with movement at the
join, and to facilitate movement of the joint.
Fascia The word "fascia" means bandage - a fitting analogy as the tissue called fascia
takes the form of sheets or broad bands of fibrous connective tissue that cover
muscles or organs, forming an outer-wrapping.
There are two types of fascia: (1) Superficial Fascia, and (2) Deep Fascia.
Superficial fascia consists of areolar connective tissue and adipose tissue, and may
also be referred to as the "subcutaneous layer" of the skin. Deep Fascia is
more relevant to the study of muscle structures because it is deep fascia that holds
the muscles together. It consists of dense fibrous connective tissue.
Skeletal
Muscle
(="Voluntary"
Muscle)
The type of muscle that causes movement of the skeletal system (especially limbs),
and of skin in the cases of the muscles of facial expression in the head and neck
area has many names. These include "skeletal muscle" (because it moves bones),
"voluntary muscle" (because it is usually under conscious control), and "striated
muscle" (because they have a striped appearance).
Perimysium Perimysium is a fibrous sheath that surrounds and protects bundles of muscle
fibres.
(It is shown as thin pale grey lines in the cross-section of skeletal muscle illustrated
above.)
Epimysium Epimysium is fibrous elastic tissue that surrounds muscle.
Note that there are usually many muscle fascicles that form a single muscle, and
epimysium surrounds the total bundle of many fascicles - as compared with

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perimysium (the fibrous sheath that surrounds and protects individual
fascicles, filling the spaces between the fascicles within the bundle of fascicles that
forms the muscle itself), and endomysium (the fine connective tissue that
surrounds and protects each individual muscle fibre - also known as a "muscle
cell", hence filling the spaces between muscle fibres within each muscle fascicle).
Fascicle The term fascicle (sometimes expressed as a "fasciculus"), refers to a "bundle",
such as a bundle of muscle fibres e.g. as illustrated above, or alternatively a bundle
of nerve fibres.
Endomysium Endomysium is the name of the fine connective tissue sheath that surrounds/covers
each single/individual muscle fibre.
Muscle Fiber
(="Muscle
Cell")
Muscle fibres also known as "muscle fibers" (American spelling), and "muscle
cells" are special cells that are able to contract, thereby causing movement - of
other tissues/parts of the body.
There are three types of muscle: striated/skeletal muscle (causing the movement of
bones/limbs), smooth muscle (surrounding organs and blood vessels), and cardiac
muscle (forming the walls of the heart).
Myofibril Myofibrils are small contractile filaments located within the cytoplasm of striated
muscle cells. These filaments cause the distinctive appearance of
skeletal=voluntary=striated muscle because they consist of bands of alternating
high and low refractive index.
This gives the muscles their striped appearance

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Introduction to the Human Endocrine System
This page is a basic introduction to the Human Endocrine System.
General Introductory Notes:
Basic summary notes about the endocrine system include:
Hormones are 'chemical messengers'.
Hormones have 'target organs'.
Endocrine glands are ductless glands that secret hormones directly into the blood.
Functions of Hormones:
1. Hormones help to regulate:
Volume and Chemical Composition of Extra-Cellular Fluid.
Metabolism
Biological Clock (Circadian Rhythms)
Glandular Secretions
Contraction of smooth and cardiac muscle fibres
Some immune system activities.
2. Hormones control growth and development.
3. Hormones govern the opertation of reproductive systems.
Comparison between the Endocrine System and the Nervous System:
1. Hormones are transported around (to their target organs) the body by the blood.
Therefore hormonal responses are relatively slow compared with nervous responses.
2. Many hormonal responses (e.g. growth) occur over relatively long periods of time.
3. The main purpose of the Endocrine System is to maintain Homeostasis within the body
(that is, to keep the internal environment constant/within balance), whereas
the key function of the Nervous System is to receive and respond to stimuli.
4. Generally, the endocrine system is controlled by the Nervous System (through the
Hypothalamus, mediated by the Pituitary Gland).
This is the end of this page but information about the Locations of and Hormones
secreted by the main Endocrine Glands and other aspects of the Endocrine
System, such as Diabetes and other Conditions that Affect the Endocrine

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System are included on other pages of this website.

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Hormones secreted by the main Endocrine Glands:
Endocrine
Gland
Hormone(s) Secreted Function(s) of Hormones
(1)
Hypothalamus
Part of the Brain: The Control and Relay Centre of the Endocrine System.
(2) Pituitary Known as the "Master Gland", this part of the brain consists of three lobes called "anterior",
"interior" and "posterior".
Posterior Oxytocin - more info Stimulates utrine contraction and brest contraction for
milk release.
Posterior Anti-Diuretic Hormone
(ADH), also known as
'vasopressin'. - more info
Stimulates re-absorption of water from kidney tubules.
Hypo- causes Diabetes Insipidus (large amounts of
urine produced).
Anterior Prolactin (PRL) - more info Production of breast milk (works in men too).
Anterior Human Growth Hormone
(HGH) - more info
Growth
Hypo- Dwarfism
Hyper- Gigantism
Thyroid Stimulating
Hormone (THS) - more info
Stimulates the thyroid to release thyroxin.
Anterior Adrenocorticotrophic
Hormone (ACTH) - more
info
Stimulates the adrenal cortex to produce:
Corticosteroids - mineral corticoids
- glucocorticoids
- cortisol (natural anti-inflammatory)
- androgens, e.g. acdosterone.
Anterior Luteinizing Hormone (LH)
- more info
Brings about ovulation and maintains the corpus luteum.
Anterior Follicle Stimulating
Hormone (FSH) - more info
Stimulates growth/development of Graafin follicles (= a
mature follicle in the ovary prior to ovulation, containing
a large fluid-filled cavity that distends the surface of the
ovary) on approx. 28 day cycle.
Melanin Stimulating
Hormone (MSH)
Gonadotrophins - more info Secondary sexual characteristics.
Anterior Interstitial Cell Stimulating
Hormone (ICSH) - more
info
Works on the seminiferous tubules in the testes – to
produce sperm – which take 21 days to mature.
(If not ejaculated within 21 days, the sperm are re-
absorbed back into the body.)