mp3
Complementarity is the
complementary and deterministic
relationship between structure and
function. i.e. structure determines
function, and function determines
structure.
Human Anatomy
and
Physiology I
Laboratory
Mpeg 4 for iPod
Histology:
Epithelial and Connective Tissue
The Histology lab involves study of the appropriate laboratory exercise, completing the Review Sheet for the
exercise, and taking the relevant quiz. Look also at the online histology sites mentioned in the introduction.
Alternately, your instructor may have you turn in drawings of the tissues in lieu of the Review Sheets.
Use the Virtual Microscope or other histology sites for good images of epithelial and connective tissue.
Click on the sound icon for the audio file (mp3 format) for each slide. There is also a link to a dowloadable mp4
video which can be played on an iPod.
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Four Basic Tissue Types:
Epithelial – lining and secretory tissue
Connective – supportive and nutritive tissue
Muscular – contracts to produce movement
Nervous – integration and control
2
All specific tissues fall into one of the four basic types. In this section we look at epithelial and
connective tissues. We will look at nerve and muscle tissues when we cover those topics.
2
Characteristics of Epithelial Tissue
• Closely packed cells of a mostly uniform type
• Cells attached to a basement membrane
• Cells are joined by a junctional complex
•Tight junctions
• Desmosomes and hemidesmosomes
• Gap junctions
3
These are the characteristics common to all epithelial tissues.
3
Epithelium is named according to shape,
structure, and arrangement of cells.
Shapes of Epithelium
•squamous - thin and flat cells
•cuboidal - cube shaped cells
•columnar - column shaped cells
4
One of the major characteristics of epithelial cells is that they come in somewhat standard shapes,
which is the basis for naming them. There are occassional variations, for example a "short columnar"
which is shorter than regular columnar and taller than cuboidal.
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Epithelial Shapes
5
Here are the basic shapes of epithelial cells. Note that the shape and position of the nucleus is a
distinguishing characteristic for each shape, and can be diagnostic for epithelial types.
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Arrangement and Structure
of Epithelial Cells
•simple - single layer of cells
•stratified - multilayered cells
•pseudostratified - false stratified
•transitional - stretchable
•ciliated - cells possess cilia
6
Arrangement and structural characteristics also distinguish different types of epithelial tissue.
6
Simple vs. Stratified
Single Layer
Multi-layered
7
Epithelial tissue is called simple if it is one layer thick, stratified if it is multilayered. The apical surface
is the free surface in both cases, i.e. the surface toward the lumen of an enclosed tubule or duct, or
the surface of the body in the case of the skin. The basal surface is the surface opposite to the apical
surface and is attached to a basement membrane.
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Simple Squamous Epithelium
Basement Membrane
Tissue
Tissue wraps
wraps to
to form
form
capillaries,
alveoli
capillaries, alveoli of
of lungs,
lungs,
etc.
etc.
Simple squamous epithelial cells, attached to a
basement membrane, wrap around to form tubes
and cavities. The basement membrane is on the
outside of these tubes (the basal surface), while
the apical surface is toward the inside. Capillary
walls for instance and the alveoli of the lungs are
formed of this very thin tissue. Thinness is the
hallmark of simple squamous epithelium, which
allows diffusion of substances across the
epithelial membrane.
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8
Functions of Simple Squamous
Epithelium
• The thinnest tissue of the body.
• Allows transport across membranes in lungs and
capillaries.
• Secretes fluid in serous membranes (e.g.
pericardial and pleural membranes, mesenteries).
• Lines cardiovascular system, covers organs, forms
glomerular capsules in kidney.
9
Simple squamous epithelium functions to produce the thinnest membranes of the body such as
capillary walls and alveoli of the lungs. This thinness allows for transport of substances across the
membranes. Simple squamous epithelium is also secretes serous fluid in mesenteries, and lines the
cardiovascular system.
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Mesothelial Lining of Peritoneal Cavity
Plasma
membrane
cytoplasm
nucleus
10
The lining of the peritoneal cavity (roughly the abdominal cavity) is formed of a serous membrane
composed primarily of simple squamous epithelium. You are looking at the epithelium from above and
can see the cells‘ nuclei and plasma membranes.
10
Bowman’s Capsule in the Kidney
Nucleus of
simple
squamous cell
Edgewise view
of simple
squamous cell
11
Cuboidal epithelium also wraps to form tubules and alveoli. These cells are the primary secretory cells
in the body's glands.
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Simple Cuboidal Epithelium
Basement
membrane
Tissue
Tissue wraps
wraps to
to
form
tubules
form tubules and
and
ducts
ducts of
of glands.
glands.
Forms ducts, tubules and secretory cells in
exocrine glands and in organs such as the
kidney.
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Cuboidal epithelium also wraps to form tubules and alveoli. These cells are the primary secretory cells
in the body's glands.
12
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Convoluted Tubules of the Kidney
Nucleus of
cuboidal cell
Lumen of tubule
Cuboidal epithelial
cells
13
The secretory cells of most of the body's glands, as well as other organs such as the liver, kidney,
and spleen are cuboidal epithelial cells, arranged into tubules, alveoli, or acini.
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Simple Columnar Epithelium
Apical
Apical surface
surface
may
may have
have
microvilli
microvilli or
or cilia
cilia
Cell nuclei lie toward
basal surface
•Non-ciliated in the GI tract, e.g. stomach and intestinal
lining.
•Ciliated in portions of the respiratory and genitourinary
tracts.
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Simple columnar epithelium is a lining tissue found where secretion and absorption occur, as in the GI
tract, or kidney. They may have microvilli to provide extra surface area, or cilia where mucus
movement along their apical surface occurs, such as in the large bronchioles of the respiratory tract.
In the GI and respiratory tracts the tissue incorporates goblet cells which secrete mucus.
14
Simple Columnar Epithelium
basement membrane
Tubule lumen
nucleus
15
This is a longitudinal section of a kidney tubule in which the simple columnar epithelial cells are of the
"short columnar" variety, with nuclei which are ovoid and more centered in the cell. These tubules
reabsorb substances and secrete substances in producing urine.
15
Simple Columnar Epithelium
in the Gastrointestinal Tract
Goblet cells
secrete mucus
Basement
membrane
16
Goblet cells are specialized epithelial cells which secrete mucus. Mucus helps protect the GI tract
lining and traps particulates in the respiratory tract.
16
Lining in the Small Intestine
villus
Goblet cell
simple columnar cells
Connective tissue (lamina propria)
17
The lining of the small intestine has several surface modifications to increase its surface area. One is
the finger-like villi seen here. The villi are then covered (or lined as you prefer) with columnar
epithelial cells. Notice the goblet cells which secrete mucus, so called because of their characteristic
goblet shape, narrow at the base and expanded at the apical end. They often give the appearance of
holes punched in the lining tissue.
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Ciliated Simple Columnar Epithelium
Ciliated simple columnar is found in large
bronchioles of the respiratory tract and in
the genitourinary tract.
18
In the respiratory tract the lining is mostly ciliated, with the mucus produced by goblet cells helping to
trap particulates. Ciliary action then moves this mucus up the respiratory passages until it reaches the
throat where it is swallowed.
18
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Ciliated Simple Columnar of Fallopian Tube
nucleus
cilia
lumen
Ciliated simple
columnar cells
connective tissue
19
Ciliated simple columnar epithelium is also found in the fallopian tube, where the cilia help in the
movement of an oocyte and zygote down the tube toward the uterus. The center of a tube is known
as the lumen.
19
Pseudostratified Ciliated Columnar Epithelium
(PCCE)
cilia
Nuclei at different
levels are diagnostic
for pseudostratified
epithelium.
A
A non-ciliated
non-ciliated pseudostratified
pseudostratified
epithelium
epithelium is
is found
found in
in large
large
glands
glands and
and parts
parts of
of male
male
urethra.
urethra.
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20
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Pseudostratified Ciliated Columnar
Epithelium in the Respiratory Tract
Cilia
Goblet cells secrete
mucus
Pseudostratified
epithelial cells
Cilia beat in wave-like fashion to move mucus along the
lining surface, carrying dust and particulates up and out of
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the respiratory tract.
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P.C.C.E. in the Trachea
Lumen of Trachea
nucleus
cilia
P.C.C.E.
Goblet cell
Basal cell
As in most all epithelia, basal cells undergo mitosis
to produce new cells so that the epithelium
constantly exfoliates and is renewed.
22
This shows P.C.C.E. found in the trachea and bronchi of the respiratory tract. In addition to the
pseudostratified epithelial cells, there are also goblet cells which secrete mucus, and basal cells
which undergo mitosis to replace pseudostratified cells which die.
22
Transitional Epithelium
Transitional epithelium lines the urinary tract
where it provides stretchability.
superficial cells
4-5 cells non-distended,
3 cells stretched.
basement membrane
23
Transitional epithelium is found only in the urinary tract, in the urinary bladder and ureter. There it
stretches to allow filling of the bladder and to damp the back-pressure in the ureter during micturition
(urination) which might otherwise damage the kidney.
23
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Transitional Epithelium
Wall of the urinary bladder
Non-distended
transitional
epithelium.
Distension
reduces the
number of cell
layers.
basement membrane
Transitional epithelium lines the renal calyces, the
ureters, the urinary bladder, and a portion of the
urethra.
24
This is transitional epithelium in its unstretched form, when the bladder is empty for example. It is
usually 5 layers thick. Imagine as this tissue stretches and the cells slide against one another, the
number of layers shrinks to 3 or 4. What junctional structures keep the cells from actually pulling
apart?
24
Stratified Squamous
old cells exfoliate from surface
cells move
up from
below
Basal layer
undergoes
mitosis
Stratified squamous epithelium forms the outer layer
or epidermis of the skin. Skin is found as the organ of
the integument and also as the lining of mucous
membranes in the oral cavity, esophagus, anus and
vagina.
25
When an epithelial tissue has more than one layer it is stratified. Stratified squamous epithelium
consists of squamous cells in many layers, and is found as the epidermis, or outer layer, of the
body's skin. Cells in the epidermis are constantly being replaced as new cells are produced by mitosis
in the basal layer and old cells are exfoliated from the apical surface. Humans exfoliate about 90
pounds of cells in the course of a lifetime, and this process keeps the cells of the epidermis constantly
renewed.
25
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Stratified Squamous
in the Epidermis of the Skin
Flattened, cornified cells cover the surface as the stratum
corneum.
epidermis of stratified
squamous epithelium
dermis
Stratum basale cells constantly
26
undergo mitosis.
In the outer skin of the body the cells die and become impregnated with keratin and keratohyaline
before exfoliating. This produces a protective layer of dead cells called the cornified layer or stratum
corneum.
26
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Non-keratinized Stratified Squamous
Epithelium
squamous surface
cell
Stratified squamous
epithelium
Section of vaginal wall.
Connective
submucosa
Notice how the cells of the intermediate layers
of the stratified squamous epithelium do not
flatten and loose their nucleus as they do in
keratinized epithelium (previous slide).
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In the body's internal skin found in the anus, vagina, oral cavity and esophagus, the cells do not
become keratinized and exfoliate while still intact. This is the basis for the ability to identify cancerous
cells which have exfoliated from the cervix of the uterus using a “Pap Smear”.
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Characteristics of
Connective Tissues*
Cells of connective tissues are widely spaced within an
intercellular matrix which determines the characteristics of
each specific tissue.
Intercellular matrix components:
fibers - may be collagen (inelastic), elastin (elastic), or
reticular.
loose or dense structure
ground substance - a semisolid gel containing water,
glycoproteins, and other substances
* Used here the term refers to tissues classified as connective tissue proper as well
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as cartilage and bone tissue.
Connective tissue has characteristics which are almost the opposite of those of epithelial tissue. It has
cells which are widely spaced apart within an intercellular matrix, and the cells may be of several
different types. The matrix may have various combinations of ingredients, which determines the type
of connective tissue.
28
Cells Found in Connective Tissues
fibrocytes, or other generic cell for each tissue:
osteocytes for bone, chondrocytes for cartilage,
adipocytes for adipose, etc.
macrophages and other phagocytic cells.
mast cells - like basophils in the blood, these cells
secrete histamine and heparin which mediate
inflammatory responses.
plasma cells - a type of lymphocyte, they secrete
antibodies. These cells, along with other white blood cells
migrate into connective tissues from the circulation.
29
There will always be one cell type which identifies the specific connective tissue, such as fibrocytes
for the fibrous tissues, osteocytes for bone, chondrocytes for chartilage, and adipocytes for
adipose tissue. These cells may be called -blasts (e.g. fibroblasts) if they are actively producing new
tissue, -clasts if they are breaking down tissue for rebuilding (e.g. osteoclasts), or -cytes (e.g.
osteocytes) if they are mature cells. The other cells are defense cells, very similar to white blood
cells found in the circulation.
29
Areolar Tissue
the Prototype Connective Tissue
30
Areolar tissue is called the prototype connective tissue because it has all the aforementioned
components: three types of fibers, all types of cells, in a loose, fluid-filled intercellular matrix. It is the
most abundant connective tissue, found associated with most epithelial tissues.
30
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Areolar Tissue
Found
Found in
in
outer
outer dermis
dermis
of
of skin,
skin,
Elastic
interstitial
interstitial
fibers
tissue,
tissue,
mesenteries
Mast cell mesenteries
and
and serous
serous
membranes.
membranes.
Collagen
fibers
Reticular fibers
Fibroblast
31
Areolar tissue is found in the outer dermis of the skin beneath the epidermis, in serous membranes of
the body, and is the major interstitial tissue, the tissue which binds cells together. Its intercellular
matrix contains most of the body's water.
31
Adipose Tissue
Low Power
Insulation
Insulation and
and
shock
shock
absorption;
absorption;
fatty
fatty pads
pads
around
around
organs,
organs,
subcutaneous
subcutaneous
fat.
fat.
Connective
matrix
Adipocytes
arteriole
32
Adipose tissue is a tissue which doesn't match the characteristics of other connective tissues. Its
cells are close together, and its matrix is sparse. Fat cells (adipocytes) are filled with a lipid vacuole
which almost completely occupies their cytoplasm. It is found in fat pads and in subcutaneous fat
which function as insulation and shock absorption, as well as nutritional storage.
32
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slide.
capillary
Adipose Tissue
high power
nucleus of
adipocyte
venule
nucleus of
adjacent
fibroblast
33
Adipose tissue is found in large amounts beneath the skin (subcutaneous) and in serous membranes
throughout the body. It is rich in blood vessels as seen in this highly magnified view.
33
Dense Irregular
Connective Tissue
Low power
High
power
Nuclei of
fibroblasts
Collagen
fibers
Found
Found in
in the
the deep
deep
dermis
of
dermis of the
the skin
skin
and
and in
in the
the
submucosa
submucosa of
of the
the
hollow
hollow organs.
organs. 34
Dense regular is also known as fibrous connective tissue, or inelastic tissue. It has bundles of
inelastic collagen fibers, seen in the high power view above. It is found in the inner dermis of the skin
as well as tendons, ligaments, and connective fascia.
34
Dense Regular
(Fibrous Connective Tissue)
Found
Found in
in
tendons,
tendons,
ligaments,
ligaments,
and
and fascial
fascial
coverings.
coverings.
Tendon,
Tendon, l.s.
l.s.
collagen
fibers
nuclei of
fibroblasts
35
Dense regular tissue is found where tensile strength is important, such as tendons and ligaments.
There are few fibroblasts and many dense bundles of inelastic collagen fibers.
35
Elastic Connective Tissue
The
The wall
wall of
of
the
aorta
the aorta
elastic fibers
Found
Found in
in
the
the
stroma
stroma of
of
the
lungs
the lungs
and
and in
in the
the
walls
of
walls of
the
the large
large
arteries.
arteries.
fibroblasts
36
Elastic connective tissue has elastic fibers which are flexible. It is found where flexibility and recoil
are important, such as in the walls of arteries (for the expansion and contraction with the pulse) and
the stroma or internal support of the lungs (for recoil during expiration).
36
Section
Section
of
of
lymph
lymph
node
node
Reticular Connective Tissue
High power
Forms
Forms the
the internal
internal
stroma
stroma of
of the
the soft
soft
organs
organs such
such as
as
the
the spleen
spleen and
and
lymph
lymph nodes.
nodes.
fibroblast
reticular
fibers
lymphocyte
37
Reticular connective tissue forms the internal support of most of the soft epithelial organs, glands,
etc.
37
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slide.
Lab Protocol
1. Identify characteristics, functions and locations of tissues
observed. Suggestion: make a chart showing these things
for the major epithelial and connective tissues.
2. Complete the Review Sheet for the Classification of
Tissues exercise in the lab manual.
3. Take the Histology online quiz.
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