Transcript Stratified Squamous Epithelium

Teamwork
• Human body contains about 100 trillion cells.
• No one cell can carry out all the necessary bodily functions
by itself. So, cells aggregate and form TISSUES.
• Tissue  Collection of cells with a similar structure and
function.
• Study of tissues is known as histology
Tissues
•
There are 4 primary tissue types in the human body:
1.
2.
3.
4.
Epithelial
Connective
Muscle
Nervous
(covering/lining)
(support)
(movement)
(control)
•
These tissues differ in the types and functions of their
cells, and the products of those cells, and their relative
distribution.
•
Which picture on this slide corresponds to which tissue?
Epithelial Tissue
• Covers the surface of the body, lines the
body cavities, forms the external and
internal linings of most organs, and
constitutes the bulk of most glands.
• Functions include:
1. Protection
2. Secretion
3. Sensory reception
4. Absorption
5. Filtration
• It’s found all over the place!
• Looking at the section of skin. Where
would the bulk of the epithelial tissue be
found?
Characteristics of Epithelia
• Composed almost entirely of sheets of close-packed cells –
very little extracellular material.
– Look at the drawing below (it represents the epithelium that lines
much of the respiratory tract) . Do you see much space between
these cells? Now look at the actual slide and notice the same thing.
• Epithelial cells are often strongly connected
to adjacent cells via tight junctions and desmosomes.
– Tight junctions are protein complexes that completely encircle a cell and thus
connect it to all its neighboring cells and it prevents anything from passing b/w
them. Common in lining of the stomach & intestines. (Why here?)
– Desmosomes – “spot weld” that holds cells together and enables a tissue to resist
mechanical stress. Common in the epidermis and cervix. (Why these 2 areas?)
Characteristics of
Epithelia
• Polarity
– Different areas of epithelial cells have
different structures. (If they have
different structures, they can have
different ___________)
– The area of an epithelial cell adjacent to
the exterior or to a body cavity is the
apical side and the opposite area is the
basal side.
• Always supported by a layer of
connective tissue.
– It’s known as the basement membrane
and is labeled by arrows in the pictures to
the right.
More Characteristics of Epithelia
• No blood vessels – it’s avascular.
– Can you pierce your skin with a needle
without bleeding?
• Has the capacity to regenerate.
– Why is this a good thing?
– Considering the locations of epithelial
tissue, is it likely to get damaged?
•
Epithelia characteristics are based on the number of cell layers present and the
shape of the cells in the apical layer.
•
Therefore, epithelium with a single layer of cells, is simple. If there is more than
one layer, the epithelium is stratified.
•
There are 3 cell shapes:
1.
2.
3.
Squamous = flat, scale-like
Cuboidal = cube-shaped
Columnar = column-shaped
Epithelia Types
•
There are at least 6 types:
1.
2.
3.
4.
5.
6.
•
Simple squamous
Simple cuboidal
Simple columnar
Stratified squamous
Stratified cuboidal
Stratified columnar
Two others are special – transitional epithelium
and pseudostratified columnar epithelium.
Simple Squamous Epithelium
• Microscopic Appearance
– Single layer of flattened
cells, shaped like fried eggs
with a bulge where the
nucleus is.
– Nucleus is flattened in the
plane of the cell.
– Cytoplasm may be very thin
and tough to see.
– From a surface view, cells
have angular contours and
nuclei appear round.
Above, the roundish structure is a ball of capillaries
found in the kidneys known as a glomerulus. The
blue arrow indicates the simple squamous
epithelium surrounding it.
Simple Squamous Epithelium
• Locations
– Air sacs (alveoli) of lungs
– Glomerular capsules of
kidneys
– Some kidney tubules
– Lining of heart and all blood
vessels
• This is called endothelium
– Serous membranes
– External lining of visceral
organs
Endothelium
The blue arrow points
directly at the nucleus of
an endothelial cell. What
type of cell does the yellow
arrow indicate?
Simple Squamous
Epithelium
• Functions
– Thinness allows material to
rapidly diffuse or be transported
through the epithelial layer.
• Ex. Gases diffuse across the thin
air sac epithelium in the lungs.
• Blood traveling to the lungs is
high in CO2 and low in O2.
After gas exchange in the lungs,
the blood leaving is high in O2
and low in CO2
• Why is thinness an asset in this
situation?
• In pneumonia, a build-up of
mucus can increase the distance
that the gases must move. Does
this make it easier or harder “to
breathe?”
Simple Squamous Epithelium
• More Functions
– Blood is filtered through the epithelium of the kidney
capillaries.
• This begins the process of removing waste products from
the blood and modifying its ionic content.
– Makes up the serous membranes and secretes a
lubricating fluidserous fluid
Simple Cuboidal Epithelium
• Microscopic Appearance
– Single layer of square or round
cells.
– Centrally-placed spherical
nuclei.
– Apical layer often has
microvilli.
• Microvilli are small extensions
of the cell membrane that
increase the surface area of the
cell.
• You usually want a cell to
have more surface area when it
is involved with secretion or
absorption.
– WHY?
This is a longitudinal section of a kidney
tubule. Notice the almost square-shaped
cells highlighted in red.
Simple Cuboidal Epithelium
• Locations
– Liver
– Pancreas
– Thyroid, salivary, and
most other glands
– Most kidney tubules
– Bronchioles (small
tubes within the lungs)
Cross-Section of a kidney tubule
Simple Cuboidal Epithelium
• Functions:
– Absorption
• Kidney tubules
– Microvilli often present to
increase surface area
• Liver
– Secretion
• Kidney tubules
• Liver
• Pancreas
• Thyroid, salivary, and most
other glands
Cross-section of the thyroid gland
Simple Columnar Epithelium
• Microscopic Appearance
– Single layer of tall, narrow cells.
– Oval or sausage-shaped nuclei,
vertically-oriented, usually located in
the basal half of the cell.
– Secretory vesicles sometimes visible
in apical portion of the cell.
– Microvilli occasionally present.
– Cilia occasionally present.
• Cilia are hair-like extensions of the
cell membrane that can move and
sweep material across the cell surface.
– Goblet cells often interspersed.
• Secrete a lubricating mucus
Simple Columnar Epithelium
• Locations
– Inner lining of
stomach, intestines,
and rectum.
– Inner lining of
gallbladder
– Inner lining of uterus
and uterine tubes
Simple columnar epithelium lining the lumen of the gallbladder.
Simple Columnar Epithelium
• Functions
– Absorption and secretion
• Columnar cells in small
intestine have microvilli to
increase the surface area for
the absorption of nutrients.
– Movement of egg and
embryo in uterine tube.
• b/c of the presence of cilia.
– Secretion of mucus.
• Lots of goblet cells in the
large intestine so as to
lubricate it and ease the
passage of feces.
Stratified Squamous
Epithelium
• Microscopic Appearance
– Multiple cell layers with cells
becoming flatter and flatter
toward surface.
– In keratinized stratified
squamous epithelium, the
apical layers are layers of
dead cells lacking nuclei and
packed with the tough protein
keratin.
– Nonkeratinized stratified
squamous epithelium lacks
the layers of dead cells at the
surface.
This is keratinized stratified squamous
epithelium from the sole of the foot. It
extends the length of the blue line on the left.
Note the multiple layers of clear, dead,
enucleated cells.
Stratified Squamous Epithelium
• Location of keratinized
type
– Epidermis. Palms and
soles of feet are typically
heavily keratinized.
• Locations of nonkeratinized type
– Lining of oral cavity and
surface of tongue
– Lining of esophagus
– Lining of vagina and anal
canal
Non-keratinized stratified squamous epithelium
What do the regions that contain the nonkeratinized version have in common?
Which of these is keratinized and which is nonkeratinized stratified squamous epithelium?
Stratified Squamous
Epithelium
• Functions
– Protection!
– Keratinized version (i.e., dry
epithelium) protects against
mechanical abrasion, water loss,
and pathogen entry.
• Keratin is very strong, waterproof,
and is bacteriostatic (i.e. prevents
bacteria from reproducing).
– Non-keratinized version (i.e., wet
epithelium) also protects from
mechanical abrasion.
• Eating food, swallowing, sexual
intercourse, birth, defecation.
Stratified Cuboidal Epithelium
• Microscopic Appearance
– 2 or more layers of cells.
– Surface layers are square
or round (cuboidal).
• Locations
– Some sweat gland ducts.
– Ovarian follicle
• Cells that surround the
developing egg
Stratified
Cuboidal
Epithelium
• Functions
– Contributes to
sweat secretion.
– Secretion of
ovarian hormones
(e.g., estrogens)
To the left, we
have an oocyte
(i.e., egg cell)
surrounded by
stratified
cuboidal
epithelium. The
oocyte is circled
in blue
Stratified Columnar
Epithelium
• Microscopic Appearance
– 2 or more layers of cells.
– Surface cells tall and narrow with
basally located nuclei.
• Locations
– Rare.
– Small portions of anal canal, pharynx,
epiglottis, and male urethra.
– Sometimes seen in large ducts of
sweat and salivary glands.
• Functions
– Often seen where 2 other tissue types
meet
– Structural integrity of gland ducts
Pseudostratified Columnar Epithelium
• Microscopic Appearance
– Looks multi-layered, but it’s
NOT!
• All cells touch the basement
membrane.
• In stratified epithelia, only
the bottom cell layer touches
the basement membrane.
– Cells are of varying heights
which gives the appearance of
stratification. Nuclei are at
several levels.
– Often has goblet cells
interspersed.
– Cells often have cilia.
Pseudostratified Columnar Epithelium
• Locations:
– Respiratory tract from nasal cavity to bronchi.
• Ciliated
• Goblet cells
– Portions of male reproductive tract
• Non-ciliated
Ciliated pseudostratified epithelium from the respiratory tract. Do you see how it
appears that there are multiple layers. Do you see the cilia (indicated by the arrow)?
Pseudostratified
Columnar Epithelium
• Functions
– In the respiratory tract there are
mucus-secreting goblet cells.
– The mucus traps dust and
bacteria.
– Cilia “sweep” the bacterialaden mucus up the respiratory
tract towards the pharynx
where it can be spit out or
swallowed.
– Smoking paralyzes and can kill
cilia – smokers have to cough
violently to expel their mucus.
Transitional Epithelium
• Microscopic Appearance
– Resembles stratified
squamous epithelium, but the
surface cells are rounded and
often bulge above surface
(dome-shaped).
– Readily see 5-6 cell layers
when relaxed and 2-3 cell
layers when stretched.
– Cells may be flatter and
thinner when epithelium is
stretched.
– Some cells are binucleate,
i.e., they have 2 nuclei.
• Locations
– Predominant epithelium lining
the urinary tract.
Transitional Epithelia
– Found in part of the kidney, the
ureters (i.e. tubes that connect the
kidney to the urinary bladder),
the urinary bladder, and part of
the urethra.
• Functions
– Stretches to allow filling of the
urinary tract.
– Called “transitional” because it
was thought to be an
intermediate between stratified
squamous and stratified
columnar epithelium. Not true
but the name has persisted.
Easy Epithelium Review
Glands
•
A gland is a cell or an organ that
produces and secretes
substances for use inside or
outside the body.
•
Predominantly composed of
epithelial tissue.
•
Secrete substances onto a
surface, into a cavity, or into
the blood
•
Glands are broadly classified as:
1.
2.
Endocrine
Exocrine
Thyroid Gland:
An endocrine
gland
An exocrine
gland
Stomach: Both
an exocrine and
an endocrine
gland
Endocrine Glands
• Ductless glands
• Produce & secrete hormones
Endocrine Glands
• Do not secrete material
into ducts.
• Secrete chemicals called
hormones into the
bloodstream where they
travel through the body
and affect other cells.
Examples: thyroid, thymus,
testes, ovaries, pituitary
gland, pineal, adrenal, etc.
Endo = within
Exocrine Glands
• Secrete material into ducts that lead to
the body surface or to one of the cavities
that is continuous with the body surface,
i.e., digestive, reproductive, respiratory
tract.
The parotid gland (a salivary gland)
• Exo = outside and crine = secrete.
• Can be multicellular or unicellular.
– Multicellular:
• Pancreas, stomach, sweat glands, salivary
glands, mammary glands, sebaceous glands,
etc.
Goblet Cell
– Unicellular:
• Goblet cells.
Exocrine Glands
• Glands w/ ducts
• produce & secrete substances onto
body surfaces (internal/ external)
• 3 types
- holocrine, apocrine, merocrine
(eccrine)
Application
• Carcinoma = cancerous growth of
epithelial tissue.
Endocrine Glands
• Do not secrete material into
ducts.
• Secrete chemicals called
hormones into the
bloodstream where they
travel through the body and
affect other cells.
• Types of glands include:
– Thyroid, thymus, testes,
ovaries, pituitary, pineal,
adrenal, etc.
Endo = within
Connective Tissue
• Most abundant, widely distributed,
and histologically variable of the 4
primary tissue types.
• Consists of cells that are typically
widely separated by lots of
extracellular material (i.e.,
extracellular matrix).
– From the diagram, compare the
density of cells in the epithelial
layers and in the connective tissue
layers. Do you see a difference?
• Most cells are not in contact with
each other, but are distributed
throughout the extracellular matrix.
Functions of Connective Tissue
1.
Binding of organs
2.
Support
3.
Physical protection
4.
Immune protection
5.
Movement
6.
Storage
7.
Heat production
8.
Transport
What do you NOT see a lot of in this micrograph of
connective tissue?
Categories of CT
1. Fibrous connective tissue
(i.e., connective tissue
proper)
2. Supporting connective
tissue
3. Fluid connective tissue
Blood
Tendon
Bone
Fibrous Connective Tissue
• Most diverse type of CT.
• Contain extremely conspicuous fibers – hence the name, fibrous
connective tissue.
• The illustration below shows typical CT fibers, typically made of
multiple strong filamentous proteins twisted about one another.
• Fibrous CT consists of cells, fibers, and something called ground
substance.
Cells of CT:
1.
Fibroblasts
–
–
–
2.
Fibro = fat, blast = making
Large, flat cells with tapered ends;
produce fibers and ground substance.
Inactive ones are known as fibrocytes.
Macrophages
–
–
–
–
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 body.
They activate the immune system when
they encounter foreign matter called
antigens.
Derived from white blood cells known
as monocytes.
Cells of CT
3.
Leukocytes
–
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.
4.
Plasma Cells
–
Certain white blood cells differentiate
into plasma cells when they detect
foreign agents.
–
Plasma cells produce and secrete
antibodies (i.e. proteins that bind to
foreign molecules (i.e. antigens), thus
inactivating them or marking them for
future destruction.
Cells of CT
5.
Mast Cells
–
Often found in CT adjacent to
blood vessels.
–
Secrete a chemical called heparin,
which is an anti-coagulant and a
chemical called histamine which is
a vasodilator.
6.
Adipocytes
–
Adipo = fat
–
Appear in small clusters in some
fibrous connective tissues.
–
If they predominate in an area
adipose tissue.
–
Contain lipid droplets for storage.
Fibers in Connective Tissue
1. Collagen Fibers
2. Reticular Fibers
3. Elastic Fibers
Collagen Fibers as seen with a
scanning electron microscope
Collagenous Fibers
Close-up of a
single fiber
• Interwoven strands of the protein
collagen.
– Most abundant protein in the human
body.
• Thick fibers with great tensile
strength – i.e., it’s tough to pull them
apart.
• In fresh tissue preps, they have a
white appearance, sometimes called
white fibers.
• In stained slides, often pink and they
usually appear quite wavy.
• Tendons, ligaments, and the deep
layer of the skin (the dermis) contain
primarily collagenous fibers.
Multiple fibers
arranged in the
extracellular
matrix
Reticular Fibers
• A thinner collagen
fiber coated with
glycoproteins.
– Stained black in the
adjacent micrograph
of the liver.
• These fibers can
branch extensively
and form networks
or frameworks for
certain organs.
Elastic Fibers
• Made primarily of a protein
called elastin, whose coiled
structure allows it to stretch
and snap back like a rubber
band.
• Contributes to the ability of
the lungs, arteries, and skin
to spring back after they are
stretched.
• Fresh elastic fibers are
yellowish and thus often
In this slide, “A” is an elastic fiber
– what do you suppose “B” is?
Ground Substance
•
Gelatinous material that occupies the space between
the cells and the fibers in connective tissues.
Imagine some Jell-o that a
contains carrots and
grapes. The carrots are
like fibers, the grapes like
cells, and the Jell-o itself is
the ground substance.
Types of Fibrous Connective Tissue
•
2 types based on the
relative abundance of
fibers.
–
–
Loose Connective Tissue
•
Lots of ground substance and
few cells. Fewer fibers.
•
Empty spaces consisting of
ground substance predominate
in tissue sections.
Dense Connective Tissue
•
Fibers occupy the most space.
Much lower number of cells
and less ground substance.
•
Appears densely packed in
tissue sections.
1
Types of Loose CT
1. Areolar CT
2. Reticular Tissue
3. Adipose Tissue
3
2
Areolar CT
Microscopic
Appearance
• Loose arrangement of
collagenous and elastic
fibers. Some reticular
fibers. (All 3 fiber types.)
• Scattered Cells. All 6
types can be present.
• Abundant ground
substance.
• Numerous blood vessels.
(Highly vascular.)
Areolar CT
• Locations
– Underlying nearly all
epithelia.
– Surrounding blood vessels,
nerves, trachea, and
esophagus.
– B/w muscles.
– W/in mesenteries, and the
visceral layers of the
pericardium and the pleura.
• Functions:
– Loosely binds epi. to
deeper tissues.
– Allows passage of
nerves and blood
vessels through to
other tissues.
– Provides an arena for
immune defense.
– Blood vessels provide
nutrients and waste
removal for overlying
epithelia.
Areolar CT
Reticular Tissue
• Microscopic Appearance
– Loose network of
reticular fibers and a type
of fibroblast known as the
reticular cell.
– Infiltrated with numerous
white blood cells.
– Often appears dark purple
or black.
• Locations:
– Lymph nodes, spleen,
thymus, and bone marrow.
Reticular Tissue
• Functions:
– The branching network of
reticular fibers will form a
scaffold-like framework
for lymphatic organs.
• Spleen, thymus, and lymph
nodes.
• Such a framework is known
as a stroma.
• The functional tissue of
these organs is known as the
parenchyma.
Adipose Tissue
• Microscopic Appearance
– Dominated by adipocytes –
large, empty-looking cells
with thin margins.
– Nucleus usually pressed
against the cell membrane –
signet ring appearance.
– Often pale.
– Blood vessels often present.
Adipose Tissue
• Locations
– Subcutaneous fat
beneath skin.
– Breast.
– Around Heart.
– Cushioning organs
• Kidneys
• Eyes
Adipose Tissue
• Functions
– Energy storage.
– Thermal insulation.
– Shock absorption.
– Protection
– Cushioning for
some organs.
Types of
Dense CT
1. Dense regular
2. Dense irregular
2
1
Dense Regular
CT
• Microscopic
Appearance
– Densely packed, parallel,
often wavy collagenous
fibers.
– Slender fibroblast nuclei
compressed between
bundles of collagenous
fibers.
– Scanty open space (i.e.
little ground substance)
– Scarcity of blood
vessels.
Dense Regular Connective Tissue
• Locations
– Tendons.
– Ligaments.
NOTE the waviness of the fibers. What function could this
structural aspect provide?
Dense Regular CT
• Functions
– Ligaments bind bone
tightly to other bones.
Resist stress.
– Tendons attach skeletal
muscles to bone and
transfer muscular
tension to bones.
Dense Irregular CT
• Microscopic Appearance
– Densely packed, collagenous
fibers running in random
directions. Compare this to
dense regular CT.
– Scanty open space (i.e.
ground substance).
– Few visible cells.
– Blood vessels present.
Dense Irregular CT
• Locations
– Deeper portion of
dermis of skin.
– Capsules around
visceral organs,
such as, the liver,
spleen, and
kidneys.
– Fibrous sheaths
around cartilages
and bones.
Dense Irregular CT
• Functions
– Provides a durable,
hard to tear structure
that can withstand
stresses placed in
unpredictable
directions.
– Why aren’t tendons
and ligaments made
like this?
Supporting Connective Tissue
•
They provide the
majority of the structural
support of the human
body.
•
1
2 types
–
Cartilage.
2
–
Bone.
Cartilage
• Supportive CT with a
flexible, rubbery matrix.
• Cells called chondroblasts
secrete the matrix and
surround themselves in it
until they become trapped
in little cavities known as
lacunae (lacuna is Latin
for “lake”).
• Once enclosed in lacunae,
cells are called
chondrocytes.
Cartilage
• Cartilage is avascular and chondrocytes
depend on the diffusion of nutrients
through the stiff, viscous matrix.
•
– Thus, their metabolism and rate of division
(i.e. mitosis) is low and healing of torn
cartilage is a long process.
– It’s avascular b/c chondrocytes produce a
chemical called antiangiogenesis factor
that, like its name suggests, prevents the
growth of blood vessels.
• Based on this, why do you suppose shark
cartilage has been touted as a possible aid in
the fight against cancer?
• The matrix consists of collagenous fibers
that range in thickness from invisibly fine
to conspicuously coarse.
3
Cartilage
•
3 types (classified based on fiber
differences):
1.
2.
3.
2
Hyaline Cartilage
Elastic Cartilage
Fibrocartilage.
1
Hyaline Cartilage
• Microscopic Appearance
– Clear, glassy matrix, often
stained light blue or pink.
• Hyalos is Greek for glass.
– Fine, dispersed collagenous
fibers, not usually visible.
– Chondrocytes often in small
clusters of 3-4 cells within a
single lacuna (known as cell
nests or isogenous groups).
– Covered by a perichondrium –
a fibrous sheath made of dense
irregular connective tissue.
Hyaline Cartilage
• Locations
– Forms the majority of the
fetal skeleton.
– Forms boxlike structure
around larynx and
supportive rings around
trachea and bronchi.
– Attaches ribs to the sternum.
– Forms a thin articular
cartilage over the ends of
bones at moveable joints.
Close-up of Hyaline Cartilage. Notice
the 2 cells in the single lacuna
Hyaline Cartilage
• Functions:
– Eases joint movements.
– Keeps airways open
(i.e. patent).
– Moves vocal cords.
– Precursor of bone in
the fetal skeleton.
– Structural attachment.
Elastic
Cartilage
• Microscopic Appearance
– Elastic fibers form web-like mesh
amid lacunae.
– Always covered by a perichondrium.
• Locations
– External ear.
– Epiglottis – flap of tissue that covers
the trachea when you swallow to
prevent food/liquid from going down
the “wrong pipe.”
– Eustachian tube – connects the ear to
the nasopharynx.
Elastic Cartilage
• Functions
– Provides flexible,
elastic support.
– What happens when
you bend and release
your ear?
A – Chondrocyte
B – Matrix w/ blackish
purple elastic fibers
C -Lacuna
Fibrocartilage
• Microscopic Appearance
– Parallel collagenous fibers
similar to those of tendon.
– Rows of chondrocytes in
lacunae between
collagenous fibers.
• Chondrocytes are fewer and
smaller and are not in
isogenous groups.
– Never has a perichondrium.
• Locations
– Pubic symphysis – the anterior joint
between the 2 halves of the pelvic girdle.
– Intervertebral discs that separate the
bones of the spinal column.
– Menisci (i.e. shock-absorbing pads of
cartilage) in the knee joint.
– At points where tendons insert on bones
near articular hyaline cartilage.
• Functions
– Resists compression and absorbs shock
in some joints.
– Often a transitional structure between
dense connective tissue and hyaline
cartilage.
• For example, at some tendon-bone
junctions.
Fibrocartilage
More Connective Tissues
• Bone is the other supporting
connective tissue.
• Blood is a fluid connective
tissue.
• Both will be discussed in
detail later.
Muscle and Nervous Tissue
• Nervous tissue
– Consists of 2 cell types: Neurons
and neuroglia.
– Detects stimuli, integrates
information, and transmits signals.
• Muscular tissue
– 3 types: skeletal, cardiac, and
smooth.
– Specialized to contract and exert
forces on other tissues.
– Major function is the creation of
movement.
Nervous Tissue
• Characteristics
- specialized to produce &
conduct nerve impulses
(electrical events)
- function: regulate & control body
activities
- location: brain, spinal cord, nerves
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Nervous Tissue
• Characteristics
- vascular
- loss of mitotic ability by neurons
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Nervous Tissue
• Structure:
- 2 major nerve cells
1. neuron – conduct & produce
impulses
 consist of dendrites, cell body, axons
2. neuroglia – numerous
supporting cells surround the
neurons
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Nervous Tissue
Muscle Tissue
• Characteristics:
- specialized to contract (shorten)
-contains contractile proteins
- vascularized
- decreased mitotic ability
- 3 kinds of muscle tissue (skeletal,
cardiac & smooth)
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Muscle Tissue
• Skeletal Muscle:
- struc: long fiber-looking cells (shorten),
striated (light/ dk. bands), multinucleated
- voluntary (conscious control)
- location: lies on bones
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Skeletal Muscle Tissue
Muscle Tissue
• Smooth Muscle:
- struc: spindle-shaped (wide in center,
tapered ends), no striations, uninucleated
- involuntary (no conscious control)
- location: wall of hollow organs (uterus,
bladder & stomach)
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Smooth Muscle Tissue
Muscle Tissue
• Cardiac Muscle Tissue:
- struc: cylindrical-looking-fiber and
highly branched, striations, 1 nuclei,
intercalated disks
- involuntary (no conscious control)
- location: wall of heart
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Cardiac Muscle Tissue
Intercalated
disk
Membranes
• Thin sheet or layer of tissue that covers a structure or
lines a cavity (epithelium with underlying connective
tissueepithelial membrane).
• Two major categories:
– Mucous- epithelium on thick loose connective tissueline
cavities that open to the outside of the body (eg. digestive,
respiratory, excretory and reproductive tracts).
– Serous- simple squamous on thin layer of loose
connective tissuelines trunk cavities and cover organs
located within cavities (eg. pleural, pericardial and peritoneal).
Secrete serous fluid
Epithelial Membranes
The majority of the body’s structures
lined by epithelial membranes.
–
1.
2.
3.
Serosa covering
the heart
Such structures include: body
cavities, tracts, external surfaces of
organs, and the external surface of
the body itself
Mucous membranes
Serous membranes
and even cutaneous membranes
Mucosa lining the duodenum (1st
part of the small intestine
Not an epithelial membrane!
• Line passageways (body cavities)
that open to the external
environment.
– Digestive, respiratory, urinary, and
reproductive tracts.
• Wet membranes that are bathed by
their own secretions or, in the case of
the urinary tract, urine.
• Mucosa have 2 or occasionally 3
layers:
– Lining epithelium (simple columnar or
nonkeratinized stratified squamous) is
adjacent to the lumen.
– Deeper is a layer of areolar CT called
the lamina propria.
– Below this, often times, is a layer of
smooth muscle called the muscularis
mucosae.
Mucous Membranes
(i.e. Mucosa)
• Have absorptive, secretory &
protective functions.
Mucous Membranes
• Often covered with mucus secreted by
goblet cells, multicellular mucous glands,
or both.
– Mucus is often involved in trapping
foreign particles (including bacteria) or
providing lubrication.
– The presence of mucus does not define
a mucous membrane however – e.g., the
mucous membrane lining the urinary
tract lacks mucus.
• Cells modified for absorption are present in
the small intestine
• Cells modified for protection are present
mainly at those positions of the tracts
closest to the exterior.
Normal stomach mucosa
Serous Membranes
(i.e. Serosa)
• Moist membranes found in closed
ventral body cavities – not open to the
exterior.
– Line the insides of the peritoneal, pleural,
and pericardial cavities; and line the outer
surfaces of some of the viscera.
• Consist of a simple squamous epithelium
lying upon a thin layer of areolar CT.
• Secrete a thin, watery fluid that arises
from the blood. It’s called serous fluid.
Serosa
• Provide an efficient means of
lubricating cavity walls and organ
exteriors so as to reduce the
friction associated with
movement.
– Why is this essential?
• The serosa lining the pleural
cavity and the lung exterior are the
parietal and visceral pleurae,
respectively. Those of the heart
are the parietal and visceral
pericardium and those of the
abdomen are the parietal and
visceral peritoneum.
Cutaneous Membrane
• Another name isSkin
• It’s an organ system
consisting of a keratinized
squamous epithelium
(epidermis) firmly attached
to a thick layer of dense
irregular connective tissue
(dermis).
• Unlike other epithelial
membranes, it is exposed to
the air and is a dry
Other Membrane Types
– Synovial-connective tissue only; lines the
inside of joint cavities
– Periosteum-connective tissue only; surrounds
bone.
Synovial
Membranes
• Another type of membrane without an epithelial
layer
– Lines specialized cavities called joint cavities
– Composed of areolar CT and adipose CT with collagen
fibers
– Secretes synovial fluid lubricates the end of bones as
they move at joints, nourishes the cartilage covering
bones, and removes microbes and debris from the joint
cavity.
Periosteum