Download MBBS (Bachelor of Medicine, Bachelor of Surgery) Human Anatomy ppt lectures Topic 28 Simple Epithelium Notes. - anatomy ppt free download human anatomy ppt lectures, medicine notes ppt, anatomy handwritten notes pdf, mbbs 1st year anatomy notes pdf download, best anatomy notes pdf, human anatomy notes pdf, anatomy easy notes pdf, anatomy notes online, anatomy short notes, Anatomy ppt, Powerpoint Presentations and lecture notes.
Epithelial Tissue -- General Features
? Closely packed cells with little extracellular
material
? Many cell junctions often provide secure
attachment.
? Cells sit on basement membrane
? Apical (upper) free surface
? Basal surface against basement membrane
? Avascular---without blood vessels
? nutrients and waste must move by diffusion
Epithelial Tissue -- General
Features
? Good nerve supply
? Rapid cell division (high mitotic rate)
? Functions
? protection, filtration, lubrication, secretion,
digestion, absorption, transportation,
excretion, sensory reception, and
reproduction.
Types of Epithelium
1. Covering and lining epithelium
? epidermis of skin
? lining of blood vessels and ducts
? lining respiratory, reproductive, urinary & GI
tract
2. Glandular epithelium- originate from
invaginated epithelial cells
? secreting portion of glands
? thyroid, adrenal, and sweat glands
Epithelium
? Epithelium is derived from all three germ
layers
? Ectoderm-oral and nasal mucosa,cornea ,
epidermis, glands of skin, mammary glands
? Endoderm-Lining of respiratory and
gastrointestinal tract, liver , panceas
? Mesoderm-lining of urogenital system,
circulatory system and body cavities lining-
mesothelium
Typical
Arrangement
of Epithelial
Tissue and its
Basement
Membrane
Basement Membrane
Basement Membrane
? The basement membrane is a thin sheet of
fibers that underlies the epithelium
? The basement membrane is the fusion of two
lamina, the basal lamina-elaborated by
epithelial cells and the reticular lamina (or
lamina reticularis)-manufactured by cells of
connective tissue
Structure of Basement membrane
? Basement Membrane
? Basal Lamina
? Lamina Lucida
? Extracellular glycoprotein-
Laminin,integrins,entactins,dystroglycans
? Transmembrane laminin receptors-project from epithelial cell
membrane into basal lamina
? Lamina Densa consists of a network of fine filaments.
? Type IV collagen. forms felt-like network of fibers that gives
the basement membrane its tensile strength
Structure of Basement membrane
? Lamina Reticularis
? Type II collagen (as reticular fibers)
? Attaching proteins (between Basal and
Reticular Laminae)-all elaborated by fibroblast
of connective tissue
? Type VI collagen (anchoring fibrils)
? fibrillin (microfibrils)
? Fibronectin
lamina lucida &lamina densa
? Lamina Densa
? dense layer closer to the connective tissue
? 30?70 nm in thickness
? consists of an underlying network of reticular
collagen (type IV) fibrils
? Lamina Lucida
? clear layer close to epithelium
Apical surface
Lateral surface
Epithelium
Basal lamina
Reticular lamina
Connective tissue
Epithelial Tissue
Epithelial Tissue
Functions of basement membrane
? anchor down the epithelium to its loose
connective tissue (the dermis) underneath
? provide structural support to the tissue
? a mechanical barrier, preventing malignant
cells from invading the deeper tissues
Fusion of basal laminae
? Glomerular filtration of the kidney
? by the fusion of the basal lamina from the
endothelium of glomerular capillaries and the
basal lamina of the epithelium of the Bowman's
capsule
? Gaseous exchange between lung alveoli and
pulmonary capillaries
? by the fusion of the basal lamina of the lung
alveoli and of the basal lamina of the lung
capillaries
Basement Membrane
Cancer cells (Malignant)
? If the epithelial cells become transformed
(cancerous) and become 'malignant', they are
able to break through the basement
membrane and invade the tissues beneath.
This characteristic is used in the diagnosis of
malignant epithelial tumors
A poorly functioning basement membrane
Diseases
? Genetic defects
? Injuries by the body's own immune system
? Other mechanisms
? Alport syndrome
? Genetic defects
? Goodpasture's syndrome
? Collagen type IV is autoantigen (target antigen) of autoantibodies
in the autoimmune disease
? Epidermolysis bullosa
? Skin
? Muscular dystrophy
? Dystrophin . a glycoprotein in the plasma membrane of muscle
cells re In muscular dystrophy, this protein is defective or missing
Classification Of epithelium
According to number of cell layers between
basal lamina and free surface and by
morphology of epithelial cells
1. Simple epithelium- composed of single layer
of cells
2. Stratified epithelium- composed of more
than one cells
Terms that help us understand what kinds of tissues we are identifying:
Terms referring to the layers
Simple = one layer
Stratified = more than one layer
Pseudostratified = false layered (appears to be more than
one
layer, but only one); ciliated = with cilia
Terms referring to the cell shapes
Squamous = flat
Cuboidal = cube
Columnar = rectangular (column)
Transitional = ability to change shape
Apical surface
Basal surface
Simple
Apical surface
Basal surface
Stratified
Classification based on number of cell layers.
Squamous
Cuboidal
Columnar
Classification based on cell shape.
The following types of epithelial tissues are covered
in this activity:
1. Simple squamous epithelial tissue (lungs)
2. Simple cuboidal epithelial tissue (kidneys)
3. Simple columnar epithelial tissue (small intestine)
4. Pseudostratified (ciliated) columnar
epithelial tissue (trachea lining)
The following types of epithelial tissues are
covered in this activity
Figure 4.3a Epithelial tissues.
(a) Simple squamous epithelium
Description: Single layer of flattened
cells with disc-shaped central nuclei
and sparse cytoplasm; the simplest
of the epithelia.
Air sacs of
Function: Allows passage of
lung tissue
materials by diffusion and filtration
in sites where protection is not
Nuclei of
important; secretes lubricating
squamous
substances in serosae.
epithelial
cells
Location: Kidney glomeruli; air sacs
of lungs; lining of heart, blood
vessels, and lymphatic vessels; lining
of ventral body cavity (serosae).
Photomicrograph: Simple squamous epithelium
forming part of the alveolar (air sac) walls (125x).
Simple Squamous Epithelium
Figure 4.3b Epithelial tissues.
(b) Simple cuboidal epithelium
Description: Single layer of
cubelike cel s with large,
spherical central nuclei.
Simple
cuboidal
epithelial
cel s
Function: Secretion and
absorption.
Basement
Location: Kidney tubules;
membrane
ducts and secretory portions
of smal glands; ovary surface.
Connective
tissue
Photomicrograph: Simple cuboidal
epithelium in kidney tubules (430x).
Figure 4.3c Epithelial tissues.
(c) Simple columnar epithelium
Description: Single layer of tall cells
with round to oval nuclei; some cells
bear cilia; layer may contain mucus-
secreting unicellular glands (goblet cells).
Simple
columnar
epithelial
Function: Absorption; secretion of
cell
mucus, enzymes, and other substances;
ciliated type propels mucus (or
reproductive cells) by ciliary action.
Location: Nonciliated type lines most of
the digestive tract (stomach to anal canal),
gallbladder, and excretory ducts of some
glands; ciliated variety lines small
bronchi, uterine tubes, and some regions
Basement
of the uterus.
membrane
Photomicrograph: Simple columnar epithelium
of the stomach mucosa (860X).
Figure 4.3d Epithelial tissues.
(d) Pseudostratified columnar epithelium
Description: Single layer of cells of
differing heights, some not reaching
the free surface; nuclei seen at
Cilia
different levels; may contain mucus-
Mucus of
secreting cells and bear cilia.
mucous cell
Pseudo-
stratified
Function: Secretion, particularly of
epithelial
mucus; propulsion of mucus by
layer
ciliary action.
Location: Nonciliated type in male's
sperm-carrying ducts and ducts of
large glands; ciliated variety lines
the trachea, most of the upper
respiratory tract.
Basement
Photomicrograph:
membrane
Pseudostratified ciliated
Trachea
columnar epithelium lining the human trachea (570x).
Given the previous examples
(consider the morphology only)
Can you name?
First, the tissue type
Second, where in the body the tissue is found
What kind of tissue does this represent?
Simple squamous epithelial tissue
Where in the body would you find this tissue?
lungs
What kind of tissue does this represent?
Simple squamous epithelial tissue (superior view)
What kind of tissue does this represent?
Simple cuboidal epithelial tissue
Where in the body would you find this tissue?
Kidneys (tubules)
The lining of the kidney glomerulus (sing.)/glomeruli (pl.) is simple squamous epithelial tissue
What kind of tissue does this represent?
Simple columnar epithelial tissue
Where in the body would you find this tissue?
small intestine
What kind of tissue does this represent?
Pseudostratified (ciliated) columnar epithelial tissue
"false layered"; it looks like more than one layer, but it is not
Where in the body would you find this tissue?
trachea lining
What kind of tissue does this represent?
Stratified squamous epithelial tissue
Where in the body would you find this tissue?
mouth lining
What kind of tissue does this represent?
Stratified cuboidal epithelial tissue
Where in the body would you find this tissue?
salivary glands, sweat glands
What kind of tissue does this represent?
Stratified columnar epithelial tissue
Where in the body would you find this tissue?
male reproductive tract
What kind of tissue does this represent?
Transitional epithelial tissue
Where in the body would you find this tissue?
empty bladder
What kind of tissue does this represent?
Transitional epithelial tissue
Where in the body would you find this tissue?
distended (full) bladder
Figure 4.3e Epithelial tissues.
(e) Stratified squamous epithelium
Description: Thick membrane
composed of several cell layers;
basal cells are cuboidal or columnar
and metabolically active; surface
cells are flattened (squamous); in the
keratinized type, the surface cells are
ful of keratin and dead; basal cells
are active in mitosis and produce the
cells of the more superficial layers.
Stratified
squamous
epithelium
Function: Protects underlying
tissues in areas subjected to abrasion.
Nuclei
Location: Nonkeratinized type forms
Basement
the moist linings of the esophagus,
membrane
mouth, and vagina; keratinized variety
forms the epidermis of the skin, a dry
Connective
membrane.
tissue
Photomicrograph: Stratified squamous epithelium
lining the esophagus (285x).
Figure 4.3f Epithelial tissues.
(f) Transitional epithelium
Description: Resembles both
stratified squamous and stratified
cuboidal; basal cells cuboidal or
columnar; surface cells dome
shaped or squamouslike, depending
on degree of organ stretch.
Transitional
epithelium
Function: Stretches readily and
permits distension of urinary organ
by contained urine.
Location: Lines the ureters, urinary
Basement
bladder, and part of the urethra.
membrane
Connective
tissue
Photomicrograph: Transitional epithelium lining the urinary
bladder, relaxed state (360X); note the bulbous, or rounded,
appearance of the cells at the surface; these cells flatten and
become elongated when the bladder is fil ed with urine.
Cell junctions
? Cell junctions consist of multiprotein
complexes that provide contact between
neighboring cells or between a cell and the
extracellular matrix.
? They also build up the paracellular barrier of
epithelia and control the paracellular
transport.
? Cell junctions are especially abundant in
epithelial tissues.
CelltoCellJunctionsand
Adhesion
A.CellAdhesionMolecules
B.Cell-CellJunctions
1.OccludingJxs-zonulaoccludensortightjunctions
2.AnchoringJxs
a.Desmosomesormaculaadherens(adhesivespots)
b.Zonulaadherensoradhesivebelt
c.Fasciaadherensoradhesivestrips
d.Hemidesmosomes
3.CommunicatingJxsorgapjunctions
Formationofmulticellorganismsrequiresspecificinteraction
betweencellstoholdthecellstogetherandtocommunicate
inordertocoordinateactivities.
A.4typesofCellAdhesionMolecules(CAMs)
areusedtoholdanimalcellstogether:
1. Cadherins
2. Ig-likeCAMs
3. Selectins
4. Integrins
Allaresingle-passtransmembraneproteinsanchoredtothe
cytoskeletonbytheircytoplasmicdomains.
Importance of Cell junction
? Cell junctions enable communication
between neighboring cells via specialized
proteins called communicating junctions.
? Cell junctions are also important in
reducing stress placed upon cells.
? Combined with CAMs( cell adhesion
molecule) and ECM, cell junctions help
hold animal cells together.
Cell junction molecules
Four main types:
? Selectins,
? Cadherins
? Integrins
? Immunoglobulin superfamily
Tissue composition
Cel junctions
Three types of cel junctions:
1. Occluding junctions: seal cel s together into
sheets (forming an impermeable barrier)
2. Anchoring junctions: attach cel s (and their
cytoskeleton) to other cel s or extracel ular matrix
(providing mechanical support)
3. Communicating junctions: al ow exchange of
chemical/electrical information between cel s
Occluding junctions
Example: Tight junctions
of intestinal epithelium
1.Occluding -Tight junction
Each cel
possesses
integral
membrane
proteins that
bind to
similar
proteins in
the adjacent,
forming a
continuous
"weld"
2. Anchoring junctions
Integral membrane proteins connect a cel 's
cytoskeleton to another cel or extracel ular matrix
Anchoring junctions
Integral membrane proteins connect a cel 's
cytoskeleton to another cel or extracel ular matrix
Anchoring junctions
Cytoskeletal fibers (MF, intermediate filaments)
connect to a
Membrane protein receptor
which attaches to another protein in either:
-the extracel ular matrix
or
-another cel membrane
2a. Cadherins and desmosomes
Cel to cel connections
are mediated by
cadherins.
These receptors
extend out from the
cel , binding to other
cadherens
Cadherins participiate in adherens junctions
Under the cel
membrane,
contractile fibers of
microfilaments
connect to cel
membrane proteins
cal ed cadherins
They surround the
cel , forming a belt
Desmosomes
Cadherins can also form localized spot connections
Cadherins
attach to
intermediate
filaments via
anchoring
proteins: a
desmosome
Cel s-to-ECM attachments:
Focal adhesions and hemidesmosomes
Cytoskeletal fibers
attach to
transmembrane
receptors (integrins)
that are attached to
extracel ular matrix
components
?Focal adhesions use
MF
?Hemidesmosomes use
IF
Gap junctions
Gap junctions al ow cel s to exchange electrical
and/or chemical signals
Composed of proteins that form channels that al ow
smal molecules to pass.
Subunits of these channels are connexins that are
assembled together to make connexons. The
connexons from 2 cel s join together to make a gap
junction.
Gap junctions
Summary
Summary
This post was last modified on 05 April 2022