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Chapter 5: Tissues!
The study of tissues = Histology

There are four major tissue
types in the body:
 Epithelial
 Muscle
 Nerve
 Connective
Epithelial Tissue
A) Locations
covers all body surfaces – inside
and outside
• forms inner lining of body
cavities and organs
•
B) Structure

Damaged cells are continually
replaced.
Cells are tightly packed and often
attached to one another by
desmosomes & tight junctions
Substances readily pass between cells
 e.g. gap junctions
C) Functions of Epithelial Tissue
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Protection
Absorption
Filtration
Secretion
D) Types of Epithelial Tissues
1. Simple Squamous Epithelial
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Absorption
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diffusion
filtration
e.g. air sacs (alveoli) of lungs
Endothelium
2. Simple Cuboidal Epithelial
• Absorption
• Secretion
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liver
thyroid
kidney
tubules
Cross-Section of a kidney tubule
3. Simple Columnar Epithelial
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Absorption
Movement (e.g. egg and embryo move
along uterine tube)—by cilia at cell
surface
Secretion (e.g. goblet cells in the large
intestine secrete mucus to ease the
passage of feces.)
lining of the gallbladder
Goblet cell
4. Stratified Squamous Epithelium
 multi-layered protection

protects against mechanical
abrasion, water loss, and pathogen
entry
e.g. sole of
the foot
5. Stratified Cuboidal Epithelium
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Protection
e.g. sweat gland ducts, mammary glands
e.g. ovarian follicle
(cells surround an
oocyte)
6. Pseudostratified Columnar Epithelium
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looks multi-layered, but it’s NOT!
cells are of varying heights , and nuclei are
at several levels.
goblet cells present
often ciliated at the surface
e.g. respiratory tract
Here, we have pathogens traveling down the pharynx
trying to attack the surface cells. How can they be
repelled???
Ahhh!!! It’s so
sticky and slimy!
The mucosal cells lining the trachea release a
flood of mucus, trapping the pathogens!
blub, blub . . . .
The cilia successfully sweep the pathogens
up and away!
7. Transitional Epithelium

resembles stratified squamous epithelium,
but surface cells are rounded and often
bulge above surface (dome-shaped)

distensible
e.g. urinary bladder and tract lining
Connective Tissue
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found throughout the body, and as
parts of various organs
composed of connective tissue cells
+ extracellular matrix
extracellular matrix = fibers +
ground substance [fluid-solid]
Functions:
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protects internal organs, provide
support, connect organs together
provide framework
fill spaces
produce blood cells
provide immune protection
tissue repair
Composition
1. Fibers
Collagen Fibers as seen with a
scanning electron microscope
a) collagenous fibers
interwoven strands of collagen (protein)
 most abundant protein
 thick fibers with great tensile strength
 white & wavy appearance
e.g. tendons, ligaments, deep layer of the
skin

Close-up of a
single fiber
b) elastic fibers
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made of elastin protein
coiled structure to stretch and snap back
like a rubber band
e.g. lungs, arteries, and skin
c) reticular fibers
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very thin collagen
fibers that branch
extensively
form frameworks for
organs
e.g. liver
2. Ground substance

Gelatinous material between the connective
tissue cells and fibers [fluid to semi-solid to
solid]
Types of
Connective
Tissues
A) Fibrous connective tissues
1) Loose Connective Tissue
a) areolar connective tissue
 Loose
arrangement of all 3 fiber types
:
e.g. under epithelia, surrounding blood vessels,
nerves, between muscles
b) reticular tissue
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loose network of reticular fibers
form a scaffold-like framework for
lymphatic organs.
e.g. lymph nodes, spleen
c) adipose tissue
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adipocytes – large, clear cells with thin
margins.
Subcutaneous fat beneath skin, breast,
heart, eyes
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Functions of adipose tissue:
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Energy storage
Thermal insulation
Shock absorption
Protective cushioning
2. Dense Connective Tissue
a) Dense Regular CT
Densely packed, parallel, often wavy
collagenous fibers
 Little open space
e.g. ligaments bind bone to other bones
tendons attach skeletal muscles to bone

b) Dense Irregular CT

durable, hard to tear; withstands
stress from unpredictable directions
e.g. deeper part of dermis, capsules
around organs, sheaths around bones.
1. Dense regular
2. Dense irregular
B) Supporting connective tissues
* provide structural support of the
human body
1. Cartilage
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has a flexible, rubbery matrix.
Cells secrete the matrix and surround themselves in
cavities known as lacunae
a. hyaline cartilage
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clear, glassy matrix
small clusters of 2-4 cells within a single lacuna
(space)
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fetal skeleton
supportive rings around trachea and bronchi.
attaches ribs to the sternum.
b. Elastic cartilage: elastic fibers
within the matrix
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flexible, elastic support
e.g. outer ear
c. fibrocartilage
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Parallel collagenous fibers similar to those of
tendon; very dense
resists compression and absorbs shock
:
e.g. pubic symphysis –between the 2 halves of the
pelvic girdle
:
e.g. intervertebral discs of the spinal column
hyaline cartilage
(collagen fibers widely
dispersed, difficult to see)
elastic cartilage
fibrocartilage
2. Bone Tissue
bone matrix = hydroxyapatite (calcium
phosphate)
C) Fluid Connective tissue
(Specialized)
Blood
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transports oxygen, nutrients, wastes
produces cells for the immune response
Muscle Tissue
Muscle Tissue
Function:
movement, by contraction of
muscle cells
a muscle cell = muscle fiber
3. Muscle Tissue
1) Skeletal muscle
• attached to bones by tendons
• long fibers, striated (banding pattern),
multi-nucleated
• voluntary contractions
• whole muscle action is due to the
contraction of multiple muscle fibers.
Skeletal Muscle
2) Smooth muscle
• in walls of internal organs and blood
vessels
e.g. for increasing blood pressure, peristalsis
of the digestive tract, uterine contractions
during labor (birth)
• “spindle” shaped cells (tapered ends),
single nucleus
• involuntary contractions
Smooth Muscle
Smooth Muscle
3) Cardiac muscle
• in the walls of the heart
• branched cells, single nucleus, striated
• intercalated discs at the junctions
between ends of cells
• involuntary contractions
Cardiac Muscle
Cardiac Muscle
Nerve Tissue
Function: senses and responds to
stimuli via electrical nerve
impulses
“It’s electric!”
* nerve cell = neuron
Structure of a neuron
Motor End Plate – neuron to muscle
Additional slides . . .
Fibrous Connective Tissue
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Most diverse type of CT
extremely conspicuous fibers
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The illustration below shows a 3-D model of some typical
CT fibers, typically made of multiple strong filamentous
proteins twisted about one another.
Fibrous CT consists of cells, fibers, ground
substance
Cells of Fibrous CT:
Fibroblasts
1.
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Fibro = fat, blast = making
Large, flat cells with tapered ends;
produce fibers and ground substance.
Inactive ones are known as fibrocytes.
Macrophages
2.
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Macro = large, phage = eating
Large phagocytic cells that wander
through connective tissue, where they
engulf and destroy bacteria, other
foreign particles, and dead or dying cells
of our own body.
They activate the immune system when
they encounter foreign matter called
antigens.
Derived from white blood cells known
as monocytes.
Cells of Fibrous CT
Leukocytes
3.
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Leuko = white, cyte = cell
White blood cells that crawl out of the
bloodstream and spend the majority of
their time in the CT. Many are phagocytes
that wander in search of pathogens.
Plasma Cells
4.
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Certain white blood cells differentiate into
plasma cells when they detect foreign
agents.
Plasma cells produce and secrete
antibodies (proteins that bind to foreign
molecules (antigens), thus inactivating
them or marking them for future
destruction.
Cells of Fibrous CT
Mast Cells
5.
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Often found in CT adjacent to
blood vessels.
Secrete a chemical called
heparin which is an anticoagulant and a chemical
called histamine which is a
vasodilator.
Adipocytes
6.
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Adipo = fat
Appear in small clusters in
some fibroconnective tissues.
If they dominate an area, we
call that area adipose tissue.
Contain huge droplets of
lipids for storage.
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:
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fibers running in random directions.
Hyaline Cartilage
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:
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Eases joint
movements.
Keeps airways
patent.
Moves vocal cords.
Precursor of bone in
the fetal skeleton.
Structural
attachment.
Elastic
Cartilage
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Elastic fibers form weblike mesh amid lacunae.
Always covered by a
perichondrium.
Loose CT
Figure A
Figure B