Organization of the body

1. Anatomy & Physiology
UNIT- II
THE ORGANIZATION OF THE BODY
(Cells, Tissues, Organs, Organ system and cavities)
Ms. K. Rebika Devi
Tutor, RCON, JAMIA HAMDARD

2. LEVELS OF ORGANIZATION
The structures of the human body are
organized of different levels that include:
Chemical level
Molecular level
Cellular level
Tissue level
System level
Organism level
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3. Chemical level
The chemical level includes atoms of the chemical
elements such as:
 Carbon
 Oxygen
 Hydrogen
 Nitrogen
 Calcium
 Sodium
 Potassium
 Magnesium
 Iron
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4. Molecular level
The two or more chemical
elements join to form the
molecules such as
 Proteins
 DNA
 RNA
 Glucose
 ATP
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5. Cellular level
 The cells are the smallest
living units of life. They are
the smallest structural and
functional units of the
human body containing
specialized internal
structures called organelles.
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6. Tissue level
The cells are grouped to form
tissues that work together to
perform a particular function.
They are-
 Epithelial tissue
 Connective tissue
 Muscle tissue
 Nervous tissue
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7. Organ level
 The tissues are grouped
together to form organs. An
organ performs a particular
function and is composed of
two or more different types
of tissues, e.g. stomach
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8. Organ system level
 The organ system consists of related
organs that have a common function,
e.g. respiratory system, digestive
system, skeletal system.
 Organism level: The organism level
is the highest level of organization. It
is formed of all of the system of the
body that work together to make a
functional organism, the human body.
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9. THE CELL
 Cells are the smallest structural and
functional unit of body. They are grouped
together to form tissues. The human body is
developed from a single cell called zygote
which is formed from the fusion of ova and
spermatozoa.
 Individual cells are too small to be seen with
the naked eye. They can be seen in the
laboratory when magnified under a
microscope.
 Cell consists of a plasma membrane and inner
to that there are a number of organelles
suspended in a water fluid called cytosol.
 The organelles include nucleus,
mitochondria, ribosomes, endoplasmic
reticulum, Golgi apparatus, lysosomes and
cytoskeleton.
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10. Plasma membrane
 The plasma membrane is the outer protective covering of
a cell. It consists of two layers of phospholipids with
protein and sugar molecules embedded in the.
 The phospholipid molecules have a head, which is
electrically charged and hydrophilic, and a tail which has
no charge and is hydrophobic.
 The plasma membrane separates the internal and external
environment of the cell and functions as selective barrier.
 It allows for the selective entry and exit of substances into
and out of the cell.
 Head end: Quite soluble in water (i.e. polar or
hydrophilic)
 Tail end: Quite insoluble in water (no affinity for
water/ water fearing) (i.e. non-polar or
hydrophobic). It contains two fatty acid chains which
face each other that meet in water-poor interior of
the membrane.
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11. Functions
 Protective : It forms the outermost boundary of cell organelles.
 Digestive : Takes in food and excretes waste products.
 Property of selective permeability: Non-polar molecules (gases like O2, CO2, and N2,
lipids, steroid hormones, alcohol) can dissolve in the membrane and thus move rapidly
across the membrane.
- Polar molecules (water soluble substances – ions, glucose, urea etc.) have much lower
solubility, therefore, they penetrate the membrane much more slowly.
- This property of selective permeability of cell membrane is useful to maintain the
difference of composition between ECF AND ICF.
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12. Cytoplasm
 The cytoplasm contains all cellular constituents
present between the plasma membrane and nucleus.
 It can be divided into; cytosol and organelles.
 The cytosol is the fluid portion of the cytoplasm and
is the site for all cellular reactions. It constitutes for
about 55% of the total cell volume and about 75-90%
of the cytosol consists of water.
 Cytosol also contains dissolved and suspended
substances like ions, albumin, fats, lipids, ATP, waste
materials, glucose and proteins.
 Organelles are the specialized structures present
inside the cytoplasm, and have specific structure and
functions.
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13. Nucleus
 Nucleus is the largest organelle contained within the
nuclear envelope. Most cells contain nucleus, except a
mature red blood cell.
 Some other cells have multiple nuclei such as skeletal
muscle.
 There is a double layered membrane covering the nucleus
called nuclear envelope and the pores present in the
nuclear envelope are called nuclear pores.
 The nuclear pores help in transport of substances between
the nucleus and cytoplasm.
 The spherical body present at a center of nucleus is the
nucleolus.
 The nucleus contains the genetic material of the body that
directs all the metabolic activities of the cell. It consists of
46 chromosomes, which are made form deoxyribonucleic
acid, the DNA.
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14. Mitochondria
 Mitochondria are the ‘power houses’ of the cell. They are involved in the aerobic
respiration, the process by which chemical energy is made available in the cell.
 The mitochondria generate ATP through chemical reactions. Their number varies depending
on how active the cell is.
STRUCTURE
1. Filamentous or globular in shape; occur in variable numbers from a few hundred to few
thousands in different cells.
2. Made up of outer membrane and inner membrane. Inner membrane folded to form cristae
(shelves) which project into the interior of mitochondrion.
3. Interior (matrix) of mitochondria contains a large number of enzymes to burn glucose in
oxygen. The ultimate result being production of CO2, water and synthesis of ATP.
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15. Cont.. Mitochondria
FUNCTIONS
1. Mitochondria are power generating
units of the cells. They are plentiful
and best developed in parts of cells
where energy requiring processes take
place, e.g. rapidly contracting skeletal
muscles
2. Also contain DNA and can synthesize
proteins.
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16. Ribosomes
 These are the granular structures containing
proteins and RNA. They are the sites for
protein synthesis and they synthesize proteins
from amino acids using RNA.
 These ribosomes are found on the surface of
nuclear envelope and rough endoplasmic
reticulum where they manufacture proteins for
export from the cell.
 Some of the ribosomes are free or unattached
and they synthesize proteins within the
cytosol.
 Ribosomes are also present in mitochondria
and they synthesize mitochondrial proteins.
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17. Endoplasmic reticulum
 Endoplasmic reticulum is a series of interconnected membranous
canal in the cytoplasm.
 They extend from nuclear envelop. There are two different
types; they are rough endoplasmic reticulum and smooth
endoplasmic reticulum.
 Smooth ER or Agranular: contains no granules
a. Agranular ER is site of steroid (adrenocortical hormone) synthesis
in steroid secreting cells and the site of detoxification processes
in other cells.
b. As the sarcoplasmic reticulum, it plays important role in skeletal
and cardiac muscles.
 Rough ER or Granular
a. Contains granules called ribosomes which are attached to the
cytoplasmic side of the membrane.
b. It is the site of protein synthesis, e.g. hormones that are
secreted by the cell and proteins that are found in enzymes.
c. Free ribosomes are also found in the cytoplasm. They synthesize
cytoplasmic protein, e.g. hemoglobin.
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18. Golgi apparatus
 These are the groups of closely folded
flattened membranous sacs with bulging
ends. It is present in all cells.
 The proteins move from the endoplasmic
reticulum to the golgi apparatus where
they are packed into membranous vesicles
called secretory granules.
 It transport proteins to others regions of
the cell.
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19. Lysosomes
 These are the small secretory vesicle formed
by golgi apparatus.
 It contains different types of lysosomal
enzymes.
 Its interior maintains a pH of 5 that is very
acidic than that of the cytosol.
 Lysosomal enzymes help to recycle worn-out
cell structure. Also it helps to destroy foreign
material such as microbes.
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20. Cytoskeleton
These are small protein strands or fibers. It include:
microfilaments, microtubules, centrosomes and cell extensions.
Microfilaments are smallest protein fibers. They provide structural
support and maintain shape of the cell. It also helps in contraction
of the cell as in muscle cell.
Microtubules are larger contractile protein fibers. They are
involved in the movement of organelles within the cell, the
movement of chromosomes during cell division and the movement
of cell extensions.
Centrosomes consists of a pair of centrioles. The centrioles are a
small cluster of microtubules. Centrosomes play an important role
during cell division.
Cell extensions consists of cilia and flagella. They extend from
plasma membrane and their components are microtubules.
Cilia are hair like projections along the free border of some cells.
They help in movement of substances along the surface, e.g.
upward movement of mucus in the respiratory tract.
Flagella are single, long, whip like structure. It helps in movement
of the cell, e.g. tail of spermatozoa.
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21. Tissues
It is the group of cells that forms a structure and
performs particular functions.
It can be classified according to its shape, size and
structure of its cells.
There are four types of the tissues. They are :
I. Epithelial (covering) tissues
II. Connective (supporting) tissues
III. Muscular tissues
IV. Nervous tissues
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22. Epithelial tissue
 These are tissues which are seen in the lining of cavities, hollow
organs, and tubular structures and in glands.
The functions of epithelial tissue is:
 Play an important role of defence and protection body organs
 Show different functions in different organs. For example:
- Secrete gastric juice in stomach.
- Absorb digested food in intestine
- Removes waste as sweat in skin
- Removes inhaled dust particles in trachea.
Types: types of epithelial tissues are based on the number of layers
1. Simple epithelial tissues: Simple epithelial tissues consists of one
layer of cells which rest on the basement membrane.
2. Compound/ Stratified epithelial tissues: In compound epithelial
tissues cell are arranged to form more than one layer.
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23. Simple epithelium
 It is consists of single layer of identical
cells. It is found on absorptive and
secretory surface.
 It consists of
a. Squamous epithelium
b. Cuboidal epithelium
c. Columnar epithelium
d. Ciliated epithelium
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24. Simple Squamous epithelium
 It consists of a layer of
flattened cells. Its cells are
arranged on the basement
membrane.
 It is found in the :
 Inner lining of heart
 Blood vessels
 Lymph vessels
 Lung alveoli.
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25. Simple Cuboidal epithelium
 Cells of simple cuboidal epithelium
are cube shaped and on surface
view cells look either polygonal or
hexagonal.
 They provide limited protection to
an organ.
 It forms glands and kidney tubules.
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26. Simple Columnar epithelium
 It consists of a layer of column like cells.
The cells are arranged on basement
membrane.
 They are seen in the alimentary tract.
The specialized columnar cells are goblet
cells that secrete mucus.
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27. Simple Ciliated columnar epithelium
 It consists of microscopic hair like structure
called cilia on the free border of columnar
cells.
 It consists of single layer of columnar cells.
They are arranged on basement membrane.
 They are seen in the uterine tubes and
airways.
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28. Stratified Epithelium
 The stratified epithelium is formed of different types of cells. They are arranged in many layers.
 It protects the underlying structure from mechanical wear and tear.
 The cells of superficial layer are flat. Superficial layer is formed from the layer below.
 It has no basement membrane. The deeper layer is columnar. Superficial layer is continuously been
shed off.
 Stratified epithelium is of two types. They are stratified squamous epithelium and transitional
epithelium.
Stratified squamous epithelium
They are of two different types like-
i. Keratinized epithelium
ii. Non-keratinized epithelium
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29. Keratinized epithelium
 They are seen on dry surfaces, e.g. skin,
nails, hair. Its superficial layer consists of
dead cells and these dead cells contain a
protein called keratin.
 It makes it a hard water proof outer layer.
It protects the underlying structures from
drying.
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30. Non-keratinized epithelium
 These are found in wet
surfaces, e.g. conjunctiva
of eyes, mouth, pharynx,
esophagus, vagina.
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31. Transitional Epithelium
 It consists of many layers of
cells that are pear shaped.
 They are found in the wall of
urinary bladder.
 It can stretch when the
bladder is filled with urine.
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32. Connective (supporting) tissues
 It is the most widely distributed tissue in our body.
 It has many functions such as
 It supports and strengthens the other tissues
 Acts as a transport medium
 Covers the internal organ and protects them
 Functions as energy reserves and it also helps
in providing immunity.
 Various types of connective tissues include:
a. Loose connective tissue
b. Dense connective tissue
c. Adipose tissue
d. Fibrous tissue
e. Elastic tissue
f. Lymphoid tissue
g. Blood cartilage and bone.
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33. Elements of connective tissue
 It has two main elements. They are connective tissue cells and extra cellular matrix.
1. Connective tissue cells: Connective tissue cells are embedded in extra cellular matrix. They
include:
 Fibroblasts
 Macrophages
 Plasma cells
 Mast cells
 Adipocytes
 WBC.
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34. Fibroblast
It is large, flat structure with branching processes. They secrete fibers and ground substance for the
extra cellular matrix.
Macrophages: These are small irregular shaped structure with many small branching. It destroys
bacteria and cell debris by the process of phagocytosis.
Plasma cells: They are developed from B-lymphocytes. They produce antibodies against antigens.
They help in providing immunity.
Adipocytes: They are fat cells or adipose cell that store fats. They are seen covering the internal
organs.
White Blood Cells: They are present in small numbers in all healthy connective tissues. During
infection or injury WBC migrate to the site of infection or injury.
Mast Cells: They produce histamine. Histamine is released in response to allergic reaction.
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35. Extra Cellular Matrix
It is a part of connective tissue in which connective tissue
cells are embedded. Extra cellular matrix consists of fibers
and ground substance.
1. Fibers : They are present in the extra cellular matrix
between the connective tissue cells. They are secreted
by fibroblasts. It support and strengthen the connective
tissue. The fibers include collagen fibers, elastic fibers
and reticular fibers.
2. Ground substance: It is present in the extra cellular
matrix between connective tissue cells and fibers. It is
made of water, polysaccharide, fat and protein. It may be
liquid, semisolid or calcified. They support the
connective tissue and bind the cells together. It
strengthens the connective tissue. It is a medium for
exchange of substances. It is a medium for
multiplication, growth and migration of connective tissue
cells.
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36. Muscle tissue
 It has the ability to contract and relax
and it help in the movement within the
body and of the body itself.
 It has blood supply to it and the blood
provide oxygen, calcium and nutrients to
the muscles.
 There are three types of specialized
muscle cells. They are:
1. Skeletal muscle
2. Smooth muscle
3. Cardiac muscle
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37. Skeletal Muscle
 These are attached to bones. They help in
the movement of our body.
 They are voluntary and their activity can
be controlled by us.
 They are cylindrical and have multiple
nuclei. It has many striations and is
striated muscles.
 They are stimulated by motor nerves
impulses.
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38. Smooth Muscle
 These muscles are seen mainly on
the walls of the internal organ.
 They are involuntary. They have no
striations and they are non-striated
muscle.
 Each cell of the smooth muscle
fiber contains a nucleus.
 They are stimulated by autonomic
nervous system.
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39. Cardiac Muscle
 These are muscle fibers that are only
seen in heart. It has many branching
fibers and the fibers are
interconnected.
 Each cell has a nucleus. The junctions
between the cells are called
intercalated discs.
 They are involuntary muscle fibers. It
has an intrinsic system that controls
the contraction and relaxation of
heart.
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40. Nervous Tissue
 These are the tissues that
makes up the nervous system.
It is includes excitable cells
and non-excitable cells.
1. Excitable cells: It includes
neurons. They initiate,
transmit, conduct and receive
nerve impulses.
2. Non-excitable cells: It includes
glial cells. They support the
cells of the nervous system.
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41. Organs
 Group of tissues together form an
organ. It performs a specialized
function.
 A group of organs form organ
system. E.g. heart, eyes, lungs,
stomach.
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42. Organ system
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It consists of organs that have common functions. The important system within the human body are:

43. Glands
 These are groups of epithelial cells which release some of their
secretions.
 There are two types of gland. They are exocrine glands and endocrine
glands.
1. Exocrine gland: these are glands that have ducts in them. Their
secretions are carried by their ducts. Their secretions include: saliva,
mucus, pancreatic juice, and gastric juice. E.g. for exocrine gland
include salivary gland, exocrine pancreas, gastric gland, lacrimal gland.
2. Endocrine gland: these are glands that do not have duct in them. Their
secretions are directly entering into the blood stream and their
secretions are mainly hormones. Through blood these hormones reaches
its target organs.
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44. Membranes
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45. Cavities
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Human body cavities and membranes
Name of cavity Principal contents Membranous lining
Dorsal body cavity
Cranial cavity Brain Meninges
Vertebral canal Spinal cord Meninges
Ventral body cavity
Thoracic cavity Heart, Lungs
Pericardium
Pleural cavity
Abdominopelvic cavity
Abdominal cavity
Digestive
organs, spleen, kidneys
Peritoneum
Pelvic cavity
Bladder, reproductive
organs
Peritoneum

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Contd…

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