Chapter 3 cells and tissues

Cells – Cell Theory
 In 1665, and English scientist named
Robert Hooke looked at empty cork cells
and identified the first cells
 he used the word cell to describe the
empty spaces in the cork

 Robert Brown was the first
person to discover the nucleus:
the cell part that controls most
of the cell’s activities
 Two German biologists Mathias
Schleiden and Theodor
Schwann formed the theory that
all plants and animals are made
up of cells

 All these ideas combined into the
modern Cell Theory:
 1. All living things are made of one or
more cells
 2. Cells are the basic units of structure
and function
 3. All cells come from existing cells

Cells – The basics
 All cells are primarily made of four
elements: Carbon, Oxygen, Hydrogen,
Nitrogen
 Living cells are about 60% water

Cells – Interstitial Fluid
 In addition to large amounts of water,
the body cells are constantly covered in
a dilute saltwater solution called
interstitial fluid
 This fluid is derived from blood

Two main types of cells
Prokaryotic Cells Eukaryotic Cells
 “pro” means before
 More primitive
 Lack a nucleus
 DNA is free floating
 “eu” means true
 More complex
 Have a nucleus that
contain DNA
 Have organelles (“tiny
organs”)

Cells – The generalized cell
 No one cell type is exactly like another
 Most do have the same parts
 Let’s talk about a generalized cell: a
basic cell used to demonstrate most cell
features

Cells – The generalized cell

The cell – The nucleus
 Nucleus: controls all of the cell’s
activities
 Contains DNA
 The “boss” of the cell
 Determines how and when
proteins are made
 Controls cell reproduction
 The nucleus usually conforms
to the shape of the cell

The cell – the nucleus
 Is enclosed by a nuclear membrane (or
nuclear envelope)
 Nuclear membrane: structure that
surrounds the nucleus and separates it
from the rest of the cell
 Nuclear pores: openings in the nuclear
membrane that allows molecules to pass
 Nucleoplasm: the jelly-like fluid between
the two layers of the nuclear membrane

 Nucleolus: the center of the nucleus
 Some cells contain multiple nucleoli
 Contains the DNA
 Helps makes ribosomes
 Contains chromatin

 Chromatin: a loose network of DNA combined
with protein scattered throughout the nucleus
 When a cell is dividing, the Chromatin
condenses and coils to form chromosomes
 Chromosomes: threadlike structures with
information that determines traits a living thing
will have

The cell – the plasma
membrane

membrane
 Plasma membrane: a fragile, transparent
barrier that contains the cell contents and
separates them from the surrounding
environment
 It is semi-permeable or selectively
permeable which means it allows some
things to pass while blocking others

membrane
 The plasma
membrane is a
phospholipid bilayer
 This means it has
two layers of fats
that line up tail to
tail

membrane
 The phospholipids each
have a hydrophilic and a
hydrophobic end
 This allows the
membrane to reseal itself
quickly when damage
occurs
 A substantial amount of
cholesterol is also found
in the plasma membrane

membrane
 The proteins scattered in the lipid bilayer
are responsible for most of the
membrane’s specialized functions
 Ex. enzymes, hormone receptors,
binding sites, protein channels, etc

The cell – Specializations of the
plasma membrane
 Let’s talk about microvilli
and membrane junctions
 Microvilli: tiny fingerlike
projections that greatly
increase the cell’s
surface area to increase
the rate of absorption

The cell – specializations of the
plasma membrane
 Membrane junctions: specialized
connections between plasma
membranes
 Three main types are:
 1. Tight junctions
 2. Desmosomes
 3. Gap junctions

The cell – membrane junctions
 1. Tight junctions: impermeable
junctions that bind cells together into
leakproof sheets that prevent
substances from passing through the
extracellular space between cells
 Plasma membranes fuse together like a
zipper
 Ex. in the small intestine, these junctions
prevent digestive enzymes from seeping
into the bloodstream

 Tight Junction

 2. Desmosomes: anchoring junctions that
prevent cells subjected to mechanical
stress from being pulled apart
 Structurally these junctions are buttonlike
thickenings of adjacent plasma membranes
(plaques), connected by fine protein
filaments
 Thicker protein filaments extend from the
plaques inside the cells to the plaques on
the cells’ opposite side, forming an internal
system of strong wires
 Ex. skin cells

 Desmosomes

 3. Gap junctions: common to heart cells
and embryonic cells, these junctions
function mainly to allow communication
 Chemical molecules (nutrients, ions, etc)
pass directly from one cell to another
through the gap
 In gap junctions, the neighboring cells are
connected by connexons: hollow cylinders
composed of proteins that span the entire
width of the adjoining membranes

 Gap junctions

The cell – the cytoplasm
 Cytoplasm: the cellular material outside
the nucleus and inside the plasma
membrane
 It is where most chemical reactions
occur inside the cell
 Made of three major elements:
 1. the cytosol
 2. the organelles
 3. inclusions

The cell – the cytoplasm
 The cytosol is the semitransparent fluid
that suspends the other elements
 The organelles or “tiny organs” are the
machinery of the cell
 Inclusions are chemical substances that
may or may not be present, depend on
the cell type
 Include stored nutrient, lipids, glycogen,
mucus, various crystallized products, etc

Organelles - Mitochondria
 Mitochondria: energy-producing
organelle in animal cells
 Consists of two membranes
 The outer is smooth and featureless
 The inner contains shelflike protrusions
called cristae

Organelles – Mitochondria
 Break down food through the
process of cellular respiration
to form ATP molecules
 ATP molecules provide the
energy for all cellular work
 “Busy” cells such as liver and
muscles cells have larger
amounts of mitochondria

Organelles - Ribosomes
 Ribosomes: tiny, bilobed, dark bodies
made of proteins and RNA
 Site of protein synthesis in the cell
 Two types:
 Free – free floating in the cell
 Bound/Attached – attached to the
Endoplasmic Reticulum

Organelles - Ribosomes
 Ribosomes: tiny particles of RNA and
protein
 The sight of protein synthesis
 Two types:
 1. Free – free-floating in the cytoplasm
 2. Bound/Attached – found on the rough
Endoplasmic Reticulum

Organelles – Endoplasmic
Reticulum
 Endoplasmic Reticulum: a system of
fluid-filled sacs and membranes located
near the nucleus that packages and
exports protein, lipids and other small
molecules.
 Accounts for about half of a cell’s
membrane

Reticulum
 Endoplasmic Reticulum: a system of
fluid-filled canals (cisterns) that coil and
twist through the cytoplasm
 Accounts for about half the cell’s
membranes
 Provides a network of channels for
carrying substances

Reticulum
 Two forms of the ER:
 1. Rough ER: studded with ribosomes
 All of the building materials of cellular
membranes are formed either in or on it:
 Proteins are packaged and sent out in
transport vesicles
 Greater number in organs that require more
proteins,
○ Ex. pancreas

Reticulum
 2. Smooth ER: plays no role in protein
synthesis
 Functions in lipid metabolism and
detoxification
 Therefore there are many smooth ER in
liver cells

Reticulum

Organelles – Golgi
Apparatus
 Golgi Apparatus: flattened stack of
membranous sacs that modifies and
packages proteins and lipids
 Forms secretory vesicles including
lysosomes

Organelles - Lysosomes
 Lysosomes: small, enzyme-filled
organelles
 Digest worn-out cell structures, foreign
substances, etc
 Many in phagocytes, cells that dispose
of bacteria and debris

Organelles - Peroxisomes
 Peroxisomes: mebranous sacs
containing powerful oxidase enzymes
that use molecular oxygen to detoxify a
number of harmful or poisonous
substances
 Most important function is to “disarm”
free radicals

 Free radicals: highly reactive chemicals
with unpaired electrons that can
scramble the structure of proteins and
nucleic acids
 Free radicals are usually produced by
cellular respiration but if they
accumulate they have devastating
effects on the cell

 Peroxisomes convert free radicals to
hydrogen peroxide
 Are created by budding from the Golgi
apparatus

Organelles - Cytoskeleton
 Cytoskeleton: an elaborate network of
protein
 the cell’s “bones and muscles”
 Determine:
 Cell shape
 Supports the organelles
 Provides the machinery needed for
intracellular transport and various types of
cellular movement

 3 types of cytoskeleton:
 1. Microfilaments
 Involved in cell motility and changes in cell
shape
 2. Microtubules
 Determine the overall shape of a cell and
the distribution of organelles
 3. Intermediate Filaments
 Help form desmosomes, resist pulling forces
on the cell

 Centrioles: rod-shaped bodies that lie at
right angles to each other
 Made up of fine microtubules
 Best known for their role in cell division
 (direct the formation of the mitotic
spindle)

 Some cells have projections known as
cilia and flagella
 Cilia: whiplike cellular extensions that
move substances along the cell surface
 Ex. ciliated respiratory cells moving mucus
 Flagella: substantialy longer projections
formed by the centrioles
 only flagellated human cell is a sperm cell

Cell Diversity
 1. Cells that connect body parts
 2. Cell that covers and lines body organs
 3. Cells that move organs and body parts
 4. Cells that stores nutrients
 5. Cells that fight disease
 6. Cells that gather information and
controls body functions
 7. Cells of reproduction

1. Cells that connect body parts
 Fibroblast: most common connective
cells in animals
 Elongated shape
 Secretes cable-like fibers
 Produce large amounts of collagen
 Abundant rough ER and large Golgi
Apparatus (make and secrete necessary
proteins
 Important in wound healing

1. Cells that connect body parts
 Erthrocyte: red blood cell
 Carries oxygen in the bloodstream
 Concave disk shape
 Extra surface area
 So much oxygen-carrying pigment
(hemoglobin) is packed in that
other organelles have been
excluded to make room

2. Cells that cover and line
body organs
 Epithelial cell
 Hexagonal shape
 Allows cells to pack
together
 Many intermediate
filaments that resist
tearing

3. Cells that move organs and
body parts
 Skeletal muscle and smooth muscle
cells
 Elongated
 Filled with many contractile filaments
 Can shorten with great force
○ Moves bone
○ Change size of internal organs

4. Cells that store nutrients
 Fat cell (adipose cell)
 Large and spherical
 Produced by large lipid droplets in the
cytoplasm

5. Cells that fight disease
 Macrophage (phagocytic cell)
 Long, extendable pseudopods (“false
feet”)
 Crawl through tissue to reach infection
sites
 Lysosomes within the cell digest the
infectious microorganisms

6. Cells that gather information
and control body functions
 Nerve cell (neuron)
 Has long processes for receiving and
transmitting messages
 Processes are covered with an
extensive plasma membrane
 Large rough ER to synthesize
membrane components

7. Cells of reproduction
 Oocyte (female): egg cell
 Largest cell in the body
 Contains several copies of all organelles

7. Cells of reproduction
 Sperm (male)
 Long and streamlined (built for
swimming)
 Flagellum acts as a motile whip to
propel the sperm

Membrane Transport
 The fluid environment on both sides of
the plasma membrane is an example of
a solution.
 Solution: a homogeneous mixture of two
or more components

Membrane Transport - solutions
 Every solution is made of two major
components – a solvent and solutes
 Solvent: the substance present in the
largest amount that does the dissolving
 Usually a fluid (liquid or gas)
 Solute(s): the substance(s) present in
smaller amount that get dissolved

Membrane Transport
 Intracellular Fluid: a solution containing small
amounts of gases, nutrients, and salts dissolved in
water
 Interstitial Fluid: the fluid that continuously bathes
the exterior of our cells
 A rich, nutritious “soup”
 Contains amino acids, sugars, fatty acids, vitamins, etc

Membrane Transport
 Quick reminder!
 Plasma membranes are selectively or
semi-permeable
 This means they let some things pass
while blocking others

Membrane Transport
 Movement of substances through the
plasma membrane happens two ways
 1. Passive Transport
 2. Active Transport

Passive Transport
 Passive Transport: movement in which
substances are transported across the
membrane without energy input from the
cell

Passive Transport
 Diffusion: the
movement of
particles from an
area of high
concentration to an
area of low
concentration
 High to Low, Go with
the Flow!

Passive Transport
 The particles are said to
move down their
concentration gradient:
the gradual change in
the concentration of
solutes in a solution
 Speed of diffusion is
affected by the size of
the molecules (smaller
= faster) and
temperature (warmer =
faster)

Passive Transport
 The hydrophobic core of the plasma
membrane makes it a physical barrier to
diffusion
 Particles will still diffuse if:
 1. they are small enough to pass through the
membrane pores
 2. they can dissolve in the fatty portion of the
membrane
 3. they are assisted by a membrane carrier

Passive Transport
 Simple diffusion:
unassisted diffusion
of solutes through
the plasma
membrane
 Facilitated diffusion:
provides passage
for certain needed
substances that are
both lipid-insoluble
and too large to
pass through the
pores

Passive Transport
 Although facilitated diffusion follows the
laws of diffusion, a protein membrane
channel is used
 This acts as a transport vehicle

Passive Transport
 Substances that
pass into and out
of cells by diffusion
save energy
 Includes the
movement of key
molecules like
water, glucose,
oxygen and carbon
dioxide

Passive Transport
 Osmosis: the diffusion of water
across a selectively permeable
membrane
 Remember water is highly polar
and is repelled by the non-polar
core of the membrane, so it must
pass through aquaporins
 aquaporins: special pores created
by membrane proteins that allow
osmosis to occur

Passive Transport
 Filtration: the process by which water
and solutes are forced through a
membrane by fluid, or hydrostatic
pressure
 In the body, this is usually seen in blood

Passive Transport
 This is a passive process
 The gradient however, is the pressure
gradient that pushes solute-containing
fluid (the filtrate) from high-pressure
areas to low pressure areas
 Important to kidneys

Active Transport
 Whenever a cell uses some of its ATP
supply to move substances across the
membrane, the process is considered
active
 Active Transport: also called solute
pumping, requires ATP –energized
protein carriers to transport substances
across the membrane

Active Transport
 The ATP-energized protein carriers used
in active transport are called solute
pumps
 Amino acids, some sugars, and most
ions are transported across the
membrane in this way
 And in most cases, they travel against
the concentration gradient
 This is opposite to the direction in which
substances would normally flow

Active Transport
 Movement against the concentration
gradient requires energy (ATP)
 Ex. Sodium-Potassium Pump
 Simultaneously carries Sodium (Na+)
ions out of the cell and Potassium (K+)
ions into the cell
 The Na-K Pump is essential for normal
nerve cell transmissions

Vesicular Transport
 Vesicular transport: moves substances
in or out of cells without their actually
crossing the plasma membrane
 Requires ATP

Vesicular Transport
 Two main types:
 1. Endocytosis
 2. Exocytosis

Vesicular Transport
Endocytosis Exocytosis
 Endocytosis take up, or
engulf, extracellular
substances by enclosing
them in a small membrane
vesicle
 Once the vesicle, or sac, is
formed, it detaches from
the plasma membrane and
moves into the cytoplasm,
where it fuses with a
lysosome and its contents
are digested
 Exocytosis moves
substances out of cells
 Is how cells actively
secrete hormones, mucus
and other products
 Products are packed in
small vesicles or sac
 The sac migrates to the
plasma membrane and
fuses
 The contents are then
spilled outwards

Vesicular Transport
 Three types of endocytosis:
 1. phagocytosis: “cell eating”
 Ingestion of solid substances
 2. pinocytosis: “cell drinking”
 Ingestion of liquid substances
 3. Receptor-mediated endocytosis: main
cellular mechanism for taking up specific
target molecules
 Both receptor and the target molecule are taken
into the vesicle

Cell Division
 The cell life cycle is the series of
changes a cell goes through from the
time it is formed until it divides
 The cycle has two major periods:
 1. Interphase, in which the cell grows
and carries on it usual metabolic
activities
 2. Cell Division, time when the cell
reproduces itself

Cell Division - Interphase
 Interphase has three major stages
 1. G1 – Growth 1
 Cell increases in size
 2. S – Synthesis
 DNA and organelles are replicated
 3. G2 – Growth 2
 Continued cell growth before division

Cell Division
 Mitosis: division of the nucleus
 Cytokinesis: division of the cytoplasm

Cell Division
 Mitosis is divided into
four major phases:
 1. Prophase
 2. Metaphase
 3. Anaphase
 4. Telophase
 And results in two
identical daughter
cells

1. Prophase
 As cell division begins, the chromatin
threads condense to form barlike bodies
called chromosomes (“colored bodies”)

1. Prophase
 The centrioles separate from each other
and begin to move to opposite sides
(“poles”) of the cell
 The direct the assembly of the mitotic
spindle
 The mitotic spindle provides the
structure for attachment and movement
of the chromosomes for the duration of
mitosis

1. Prophase
 The nuclear envelope and nucleoli break
down and disappear
 Chromosome attach randomly to spindle
fibers at the centromere

2. Metaphase
 The chromosome cluster and align
along the metaphase plate (center of the
spindle midway)
 Creates a straight line of chromosomes

3. Anaphase
 The centromeres split
 The sister chromatids split (now called
chromosomes again)
 Chromatids move to opposite poles of
the cell
 When chromosome movement ends

4. Telophase
 Essentially prophase in reverse
 Chromosomes uncoil and become
chromatin again
 Spindle fibers break down and
disappear
 Nuclear envelopes reform and nucleoli
reappear around each group of
chromatin

Cytokinesis
 Cytokinesis usually begins during late
anaphase and finishes in telophase
 A contractile ring of microfilaments forms
a cleavage furrow over the midline of the
spindle
 This squeezes the original cytoplasmic
mass into two parts
 Each daughter cell is smaller, but
genetically identical

Mitosis and Cytokinesis
 Mitosis and Cytokinesis usually go
together, but sometimes the cytoplasm
does not divide
 This creates binucleated or
multinucleated cells
 This is common in liver cells

Protein Synthesis
 DNA is the blueprint for protein
synthesis
 A gene is defined as the DNA segment
that carries the information for building
one protein of a poly peptide chain

Protein Synthesis - RNA
 DNA requires a messenger and a
decoder to complete the building of
proteins
 These jobs are carried our by RNA
 There are three varieties of RNA
involved in protein synthesis:
 1. transfer RNA (tRNA)
 2. ribosomal RNA (rRNA)
 3. messenger RNA (mRNA)

Protein Synthesis
 Protein Synthesis occurs in two major
phases:
 1. Transcription – when complementary
mRNA is made at the DNA gene
 2. Translation – when the information carried
in the mRNA molecules is “decoded” and
used to assemble proteins

Protein Synthesis -
Transcription
 Transcription involves the
transfer of information from
DNA’s base sequence into
the complementary base
sequence of mRNA
 Occurs in the nucleus
 Only DNA and mRNA are
involved in transcription
 Each DNA triplet (three-base
sequence) complements a
mRNA codon

Protein Synthesis -
Transcription
 So if the DNA sequence is:
 ATG – TCT – GAA
 (triplets)
 The transcribed mRNA sequence is:
 UAC – AGA – CUU
 (codons)

Protein Synthesis - Translation
 In translation the language
of nucleic acids (the base
sequence) is “translated”
into the language of proteins
(amino acids)
 Occurs in the cytoplasm
 Involves three major
varieties of RNA

 Once the mRNA attaches to the
ribosome, tRNA comes into the picture
 Each tRNA carries or “transfers” an
amino acid to the ribosome
 They match a three-base anticodon
with the codon of the mRNA as it reads
through the ribsome

 Once the first tRNA has moved itself into
the correct position, the ribosome moves
the mRNA strand along, bringing the next
codon into position to be read by the tRNA
 As each amino acid is brought in, they are
joined together by enzymes
 As the amino acids join, each tRNA is
released
 When the last codon, or “stop” codon is
read, the protein is released

Body Tissues
 Tissues: groups of cells that are similar
in structure and function
 Four primary tissue types:
 1. Epithelial (covering)
 2. Connective (support)
 3. Muscular (movement)
 4. Nervous (control)

Epithelial Tissues
 Epithelial Tissue (epithelium): the lining,
covering and glandular tissue of the
body
 Helps form boundaries and separate
 Nearly all substances the body gives off
or receives must pass through the
epithelium

Epithelial Tissues
 Functions of the epithelium:
 Protection
 Absorption
 Filtration
 Secretion

Epithelial Tissues -
Characteristics
 1. Fit closely together (except glandular cells)
 Bound together by many desmosomes and tight
junctions
 2. One free edge or surface
 Apical surface
 3. Lower surface rests on a basement
membrane
 4. No blood supply of their own
 Avascular
 Depend on diffusion from the capillaries
 5. Regenerate themselves, if well nourished

Classification
 Each epithelium is given two names
 The first indicates the relative number of
cell layers

Classification
 The classifications by cell arrangement are:
 Simple epithelium – one layer
 Stratified epithelium – more than one layer

Classification
 The second indicates the shape of the
cell.
 There are:
 Squamous – flattened like scales
 Cuboidal – Cube-shaped
 Columnar – Column-shaped
 (stratified epithelia are named for the
cells at the free surface not those on the
basement membrane)

Classification

Epithelial Function
 Simple Epithelia are concerned mainly
with absorption, secretion and filtration
 Stratified epithelia function primarily to
protect

Glandular Epithelium
 A gland consists of one or more cells
that make and secrete a particular
product
 This product is called a secretion
 Usually consists of protein molecules in
an aqueous solution fluid

 Two major types of glands develop from
epithelial sheets:
 1. Endocrine glands
 2. Exocrine glands

Endocrine Glands
 Endocrine glands:
glands that lose their
connection to the
surface or duct (also
called ductless glands)
 Secretions diffuse
directly into the blood
vessels that weave
through the gland
 Ex. thyroid, adrenals,
pituitary

Exocrine Glands
 Exocrine glands:
gland that retain
their ducts
 Secretions empty
through the ducts to
the epithelial
surface
 Ex. sweat and oil
glands, liver,
pancreas

 The term secretion
also indicates an
active process in
which the glandular
cells obtain needed
materials from the
blood and use them
to make their
secretion, which
they then discharge

Connective Tissue
 Connective Tissue: connects body parts
 Found everywhere in the body
 Most abundant and widely distributed of
the tissue types

Connective Tissue
 The characteristics of connective tissue
include:
 1. Variations in blood supply
 Most connective tissue is well vascularized
 Exceptions – Ligaments, Tendons,
Cartilages
○ As a result these heal very slowly
 2. Extracellular Matrix
 Varying amounts of a nonliving substance
outside the cells

Connective Tissue
 The extracellular matrix distinguishes
connective tissue from other cell types
 Has two main elements – a structureless
ground substance and fibers

Connective Tissue
 The ground substance of the matrix is
composed largely of water plus some
adhesion proteins and large, charged
polysaccharides
 The adhesion proteins are the “glue”
that allows the connective tissues to
attach themselves to matrix fibers
embedded in the ground substance
 The charged polysaccharides trap water
as they intertwine

Connective Tissue
 Various types and amounts of fibers are
in the matrix and form parts of the matrix
itself
 Including collagen (white) fibers, elastic
(yellow) fibers and reticular (fine
collagen) fibers

Connective Tissues
 Because of the extracellular matrix,
connective tissue can form soft packing
tissue around organs, bear weight, and
withstand stretching and other abuses

Connective Tissue
 There is great variation in connective
tissue
 The major classes are:
 Bone
 Cartilage
 Dense Connective
 Loose Connective
 Blood

Connective Tissue - Bone
 Bone (osseous tissue)
 Composed on bone cells sitting in
cavities called lacunae (pits) and
surrounded by layers of a very hard
matrix that contains calcium salts and
large numbers of collagen fibers
 Important in protecting and supporting
other body organs

Connective Tissue -
Cartilage
 Less hard and more flexible than bone
 Found a few places in the body
 Most widespread is hyaline cartilage:
abundant collagen fibers hidden by a
rubbery matrix with a glassy blue-white
appearance

Connective Tissue -
Cartilage
 Forms supporting structures in the
larynx, attaches ribs to the breastbone,
covers ends of bones at joints

Connective Tissue
 There are other types of cartilage:
 Fibrocartilage: highly compressible that
forms the cushionlike disks between the
vertebrae of the spinal column
 Elastic cartilage: is found where a
structure where elasticity is desired
 Ex. external ear

Connective Tissue
 Dense Connective Tissue:
collagen fibers as its main
matrix element
 Crowded between the collagen
fibers are rows of fibroblasts
that manufacture the building
blocks of the fibers
 Forms tendons and ligaments

Connective Tissue
 Tendons: attach skeletal muscles to
bones
 Ligaments: connect bones to bones at
joints
 Ligaments are more stretchy and elastic
than tendons

Connective Tissue
 Loose Connective Tissue: softer, have
more cells and fewer fibers
 Areolar Tissue: most widely distributed
connective tissue variety in the body
 Cushions and protects body organs

Connective Tissue
 When a body region is inflamed, the
areolar tissue in the area soaks up the
excess fluid like a sponge, and the area
swells and becomes puffy
 This is called an edema

Connective Tissue
 Adipose Tissue:
commonly called
fat, areolar tissue in
which fat cells
predominate
 Forms
subcutaneous
tissue

Connective Tissue
 Reticular connective tissue: a delicate
network of interwoven reticular fibers
associated with reticular cells, which
resemble fibroblasts
 Forms stroma, the internal framework
which can support many free blood cells
and in lymphoid organs

Connective Tissue
 Blood: (vascular tissue)
is considered connective
tissue because it
consists of blood cells
surrounded by nonliving,
fluid matrix called blood
plasma
 The “fibers” of blood are
soluble protein
molecules that become
visible only during blood
clotting

Muscle Tissue
 Muscle tissue: highly specialized to
contract, or shorten, to produce
movement

Muscle Tissue
 Three main types:
 1. skeletal muscle
 2. cardiac muscle
 3. smooth muscle

Muscle Tissue
 Skeletal Muscle
 attached to the skeleton
 can be controlled voluntarily
 when contracted they pull on
bones or skin
 the cells of skeletal muscle
are long, cylindrical,
multinucleate and have
obvious striations

Muscle Tissue
 Cardiac Muscle
 Found only in the heart
 As it contracts, the heart acts as a pump
and propels blood through the blood
vessels
 Has striations
 Uninucleate, relatively short, branching,
and fit tightly together through intercalated
disks
 Under involuntary control

Muscle Tissue
 Smooth Muscle (visceral muscle)
 No visible striations
 Single nucleus, spindle-shaped
 Found in the walls of hollow organs
 As it contracts, the cavity of an organ
contracts or enlarges
 Contracts more slowly than the other
two types
 Ex. peristalsis

Nervous Tissue
 Think neurons
 All neurons receive and conduct
electrochemical impulses from one part
of the body to another
 Irritability and conductivity are their two
major functional characteristics

Nervous Tissue
 Drawn out cytoplasm, allow for long
signal transmission
 With supporting cells, neurons make up
the structures of the nervous system

Tissue Repair
 Tissue repair occurs in two major ways:
 Regeneration – replacement of
destroyed tissue by the same kind of
cells
 Fibrosis – involves repair by dense
connective tissue by the formation of
scar tissue
 Depends on the type of tissue damaged and
the severity of the injury

Tissue Repair
 Tissue injury sets the following steps in
motion:
 1. capillaries become permeable
 Fluid rich in clotting proteins seep into the
injured areas
 2. granulation tissue forms
 Delicate pink tissue composed largely of new
capillaries
 3. surface epithelium regenerates
 Makes its way across the granulation tissue

Three other important
terms:
 Neoplasm: an abnormal mass of
proliferating cells
 Benign or malignant
 Hyperplasia: when certain body tissues
may enlarge because there is some
local irritant or condition that stimulates
the cells
 Atrophy: a decrease in size in an organ
or body area that loses its normal
stimulation

Chapter 3 cells and tissues

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Chapter 3 cells and tissues