Download Epithelium Lecture

University of mosul
mosul medical college
Anatomy department
Date : 14/3/2013
Epithelium
Submitted
By:
Tahir ali tahir,
Ali ghassan younis,
Sakher bahnam,
Amar abd almaseh,
Suhaib ganem.
_ 2013 _
Team work
Epithelium
Epithelium
All organs of the body are composed of
combinations of the four basic tissues, epithelial,
connective, muscular and nervous.
Epithelium
An epithelium is a sheet of closely apposed cells,
separating a space (lumen) from underlying
tissue.
Epithelium
Examples: covering of the skin (epidermis),
linings of the gut, linings of body cavities (pleural,
peritoneal and pericardial cavities) and linings of
blood vessels (endothelium).
Epithelium
Common features of all epithelia:
A. Close apposition of cells.
B. Free surface of epithelial cells is adjacent to the
space that is limited.
C. Basal surface is adjacent to connective tissue.
Common features of all epithelia:
D. Sheets of epithelial cells may be modified into
tubes forming glands. *
E. Absence of blood vessels
within epithelial layer
(with one exception in
inner ear).
Epithelium
Functions:
A. Protection against abrasion, desiccation
(epidermis).
B. Lubrication (mesothelia).
C. Secretion (glands).
D. Absorption (intestine).
E. Sensory reception (ear, epidermis, etc.).
F. Gas transfer (lungs).
G. Ion transport (kidney).
Epithelium
Classification:
A. Number of cell layers.
1. Simple epithelia have only one layer of cells. *
2. Stratified epithelia have two or more cell layers.
Only cells at the basal surface of the epithelia contact
connective tissue. *
3. Pseudostratified epithelia have their nuclei
arranged at different levels in the epithelium, giving
a stratified appearance. However, all the cells make
contact with the basal lamina.
Epithelium
Epithelium
Epithelium
Classification:
B. Shape of superficial cells.
1. Squamous cells are flattened in the plane of the
epithelium. *
2. Cuboidal cells have heights approximately equal
to width. *
3. Columnar cells are "taller" than they are wide. *
4. Transitional epithelia are capable of changing
shape.
• Simple squamous epithelium
consists of a single layer of
flat, shield-like cells. In a
cross sectional view, the
cells bulge due to the
presence of the nucleus This
tissue may have a protective
function or perform
secretory functions. The
image shows this tissue
lining the alveoli of the lungs.
It also lines the blood vessels
(endothelium) and the
chambers of the heart
(endocardium). It also lines
the body cavities as the
mesothelium of the
peritoneum.
Simple Squamous
Epithelium
Simple Columnar
Epithelium
Simple columnar epithelium
consists of cells which
are taller than wide (*).
This tissue lines the
alimentary canal from the
stomach to the rectum.A
number of mucous
producing cells can be
seen in this view.
*
Simple Cuboidal
Epithelium
• Simple cuboidal epithelium
consists of short cube, prism
or trapezoid-shaped cells (*).
The nuclei are large, spherical
and centrally located in the
cells. This tissue often has a
secretory function. Found in
many glands both exocrine and
endocrine, for example, lining
thyroid follicles and ducts of
sweat glands.
• They are especially common in
kidney tissue.
*
Team work ^_^
Ali ghassan yonis
1st. grade
Gp. B1
Stratified Squamous Epithelium
(non-keratinized)
• The stratified squamous
epithelium that lines interior
spaces of the body does not
form keratin or a dead surface
layer. In a vertical cross
section, the deepest layer
rests on a basement
membrane and is cuboidal in
shape This epithelium is
located lining the mouth,
esophagus and portions of the
pharynx and larynx
Stratified Squamous
(keratinized)
• Stratified squamous
consists of several layers
of generally flat cells (*)
which rest on a
supporting layer of
connective tissue. In skin
the cells of the stratified
squamous produce a
tough fibrous protein
called keratin which
waterproofs the skin. On
the top of the epithelium
the cells die (arrow)
forming the stratum
corneum.
*
Stratified Columnar
Epithelium
• Consists of several layers of cells.
– The cells at the surface are elongated
whereas the cells at the base are cubeshaped.
• Found in part of the male urethra and
parts of the pharynx.
Stratified Columnar
Epithelium
Stratified Cuboidal Epithelium
• Consists of two or three layers of cuboidal
cells that form the lining of a lumen (which is
a space within a tubular structure such as a
blood vessel or intestine).
– The layers provide more protection than a single
layer.
• Locations:
– Lines the larger ducts of the mammary glands,
sweat glands, salivary glands, and pancreas as
well as lines developing ovarian follicles and
seminiferous tubules.
Stratified Cuboidal Epithelium
Pseudostratified Ciliated Columnar
lp
As its name implies, pseudostratified columnar appears
stratified but is not. Each cell in this tissue touches the
basement membrane. This tissue is often ciliated (arrow)
and is richly endowed with mucous producing cells.
Pseudostratified epithelium rest on a supporting connective
tissue called the lamina propria (lp). The lamina propria
consists mainly of areolar connective tissue.
Transitional
Epithelium
Transitional epithelium is located exclusively in the urinary system.
It is found lining the pelvis of the kidney, the ureter, urinary bladder
and a portion of the urethra. This epithelium rests on a lamina
propria of areolar tissue. It is capable of great distension. The cells
of transitional epithelium appear balloon-like when the bladder is
empty of urine.
Most epithelia contain special cells to provide
unique properties that increase the efficiency of
function.
One type of cell that
is commonly used to
categorize epithelia
is the goblet cell, a
mucus secreting cell
found in many
regions of the G.I.
and respiratory
tracts.
Goblet Cell
It derives its name from its characteristic
shape; it is easily seen with the light
microscope.
Team work
Sakher bahnam
1st. grade
Gp. B1
Epithelial Surfaces
Apical Surface (Free)
Lateral Surface
(Intercellular)
Lateral Surface
(Intercellular)
Basal Surface
Free Surface Specializations
Microvilli: because the
diameter of a microvilli is
less than the resolution of
the light microscope,
individual microvilli can
not be seen by this
method.
However, collectively,
microvilli form uniform
borders that appear
brush-like or striated by
light microscopy.
Free Surface Specializations
1. Microvilli:
Core of Actin
Microvilli
Free Surface Specializations
Cilia: these specializations are longer and have
a greater diameter than microvilli and can be
resolved at the light microscope level.
Free Surface Specializations
2. Cilia:
Core of
Microtubules
Dynein
Free Surface Specializations
3. Stereocilia:*
Free Surface Specializations
3. Stereocilia: long microvillar-like structures
found in the epididymis of the male
reproductive tract and in some special sensory
epithelia.
Free Surface Specializations
4. Keratinization: a specialization of stratified
squamous epithelia that are subject to abrasion
or desiccation (example: epithelium covering
the skin, epidermis).
Stratified squamous epithelia are usually
described as being keratinized or nonkeratinized.
Free Surface Specializations
4. Keratinization:
Team work
Amar abd almaseh
1st. Grade
Gp. B1
Intercellular Junctions
Membrane-associated structures
contributing to adhesion or
communication between adjacent
cells.
Intercellular Junctions
Some of these specialized structures act to adhere
epithelial cells to the basal lamina (hemidesmosomes) *
or adjacent cells to each other (zonula adherens and
desmosomes).
ZA: microfilaments, terminal web
Macula adherens, attachment
plaques, cytokeratin
Intercellular Junctions
Some act as impermeable barriers between cells
(impermeable junctions: zonula occludens).
Intercellular Junctions
Some act as impermeable barriers between cells
(impermeable junctions: zonula occludens).
Tight junctions
Intercellular Junctions
They act in intercellular
communication (communicating
junctions: gap junctions).
6-Connexins
Make
Connexons
Intercellular Junctions
The zonulae adherens, hemidesmosomes and
desmosomes are called adherent junctions.*
Intercellular Junctions
A junctional complex is
a combination of
intercellular junctions
consisting of (beginning
from the most apical
region of the
intercellular plasma
membranes) a:*
zonula occludens, *
zonula adherens and*
a desmosome.
Intercellular Junctions
Team work
Suhaib ganem mustafa
1st. Grade
Gp. B1
Basement Membrane
The basement membrane is a thin
structure visible by light microscopy
which is composed of either:
Basement Membrane
The basement membrane is a thicker
structure visible by light microscopy
which is composed of either:
two fused basal laminae.
Basement Membrane
The basement membrane is a thicker
structure visible by light microscopy
which is composed of either:
or a basal lamina and a reticular lamina.
Basement Membrane
Basal Lamina
A layer of extracellular
material between the
basal surface of all
epithelial cells and the
underlying connective
tissue.
Basal Lamina
Dense layer of material (20-100 nm thick) which is
only visible by electron microscopy.*
Composed mainly of type IV
collagen, laminin and
heparin sulfate, a proteoglycan.
Basal Lamina
Attached to connective tissue by type VII collagen.
Basal laminae are also present around other tissue
types which are in contact with connective tissue.
Basal Lamina
Also found between adjacent epithelial cells where
the basal laminae from each adjacent epithelial
cell fuse to form a thicker basement membrane.
Basal Lamina
Components of the basal lamina are secreted by
epithelial, muscle, adipose or Schwann cells.*
Reticular fibers secreted by connective tissue cells
(reticular lamina) may be closely associated with
the basal lamina.
Basal Lamina
Basal Lamina
Functions:
Provides a barrier regulating the exchange of
macromolecules.
Involved in cell-to-cell interactions.
Basal Lamina
University of mosul
mosul medical college
Anatomy department
Date : 14/3/2013
Glandular epithelium
Submitted
By:
Abdullah shamel,
Abdullah thabit ,
Abdullah anwar.
_ 2013 _
Team work
Abdullah shamel
1st. Grade
Gp. B1
Glandular Epithelia
Formed by epithelial cells that secrete a fluid of
different composition than blood or intercellular
fluid.
Secreted substances can be ions, secretory
polypeptides or proteins, lipids or glycoproteins.
Glandular Epithelia
Types of glandular epithelia:
a. Endocrine glands: lose their connection
(ductless) to the surface from which they
originated. Products (hormones) are secreted
into the blood stream. *
b. Exocrine glands: retain their connection (duct)
to the surface. Secretion products (produced
by the secretary portion of the gland) are
transported to the surface via epithelial celllined ducts.
Glandular Epithelia
Types of glandular epithelia:
Glandular Epithelia
Classified by modes of secretion:
1. Merocrine: secretory granules leave by exocytosis
with no loss of cytoplasm.
Glandular Epithelia
Classified by modes of secretion:
2. Holocrine: whole cell is secreted into lumen of
gland.
Glandular Epithelia
Classified by modes of secretion:
3. Apocrine: secretory product and a portion of the
apical cytoplasm of the gland cells are secreted.
Glandular Epithelia
Classified by modes of secretion:
Glandular Epithelia
Classification of Exocrine Glands
Exocrine glands may be classified according to cell
number, and/or the shape and branching pattern of
their secretory portions and ducts.
1. Unicellular: goblet cells
2. Multicellular:
Glandular Epithelia
Exocrine glands :
1. Simple glands: one unbranched duct. Secretory
portion may be tubular, coiled tubular, branched
tubular, or acinar.
Glandular Epithelia
Exocrine glands :
2. Compound glands: more than one duct that
branches repeatably. Secretory portion may be
tubular, acinar, or tubuloacinar.
Exocrine Glands
Secretory activity of glands controlled by nervous
and endocrine systems involving chemical
messengers, neurotransmitters or hormones.
These factors interact with receptors either located in
the gland cells plasma membrane or within the gland
cells cytoplasm.
Exocrine Glands
In the first case, binding to a surface receptor often
results in the activation of a second messenger system
(e.g., adenylate cyclase) while;
binding to cytoplasmic (or nuclear) receptors results
in an activation of specific genes.
Team work
Abdullah thabit
1st. Grade
Gp. B1
Chemical-Messenger-Producing Cells
Three types:
A. Neurocrine: chemical messenger is released at an
intercellular space between adjacent cells.
B. Paracrine: chemical messenger is released into
extracellular fluid and diffuses at some distance to
nearby cells.
C. Endocrine: chemical messenger (hormone) is
released into the blood, which is then transported
to target cells.
Hormones can be: derivatives of cholesterol
(steroids); proteins; polypeptides; or biologically
active amines.
Serous Vs. Mucus-Secreting Cells
Serous:
Cells often triangular in
shaped. *
Serous Vs. Mucus-Secreting Cells
Serous:
Basal regions of cells
basophilic due to rER
Apical area acidophilic due
to secretory granules
Serous Vs. Mucus-Secreting Cells
Serous:
Serous Vs. Mucus-Secreting Cells
Serous:
Serous Vs. Mucus-Secreting Cells
Mucus:
Serous Vs. Mucus-Secreting Cells
Mucus:
Direction of Transport Across Epithelia
*
Absorption
Secretion
Team work
Abdullah anwar
1st. Grade
Gp. B1
Ion-Transporting Epithelia
A. Definition: epithelial cells which are involved in
the transport of certain ions against a
concentration and/or potential (charge) gradient.
B. Requires energy, usually in the form of ATP --->
ADP + Pi; catalyzed by ATPase enzymes, e.g., Na,
K-ATPase.
Ion-Transporting Epithelia
In the proximal tubule cells of the kidney,
Na+ freely enters the apical cytoplasm of the
cell
but is actively transported across the basal
plasma membrane against a charge and
concentration gradient.
Ion-Transporting Epithelia
Na+
enters the
apical cytoplasm
of the cell freely.
Na+
Ion-Transporting Epithelia
but is actively
transported across
the basal plasma
membrane against
a charge and
concentration
gradient. *
Na+
Na+
Ion-Transporting Epithelia
To accomplish this tranlocation of Na+, iontransporting epithelia, contain numerous infoldings
of their basolateral plasma membrane.
Ion-Transporting Epithelia
Na, K-ATPase enzyme has been identified in the
plasma membrane infoldings.
Ion-Transporting Epithelia
Located between the basal infolding are found a great
number of vertically oriented mitochondria (source of
ATP).
Ion-Transporting Epithelia
The basal infoldings can often be visualized as "basal
striations" by light microscopy.
Steroid Hormone-Producing Epithelia
Definition: endocrine epithelial cells which are
involved in the synthesis and secretion of steroid
hormones (steroids).
Steroid Hormone-Producing Epithelia
Morphology:
Polyhedral or rounded acidophilic cell with a central
nucleus.
Steroid Hormone-Producing Epithelia
Frequently the cytoplasm contains rich deposits of
lipid droplets (stain with osmic acid).
Steroid Hormone-Producing Epithelia
Contains abundance of smooth endoplasmic
reticulum and mitochondria that usually contains
tubular rather than
lamellar cristae.