???
- Continuous cells in apposition over a large portion of their
surface
- Rest on a continuous extracellular matrix – _________ –
meshwork of fine filaments
• Forms a boundary layer
Control movement of substances from the external
environment and internal milieu, or between
compartments of the body
• Lateral surfaces are highly specialized
EPITHELIAL TISSUE
- Rest on a continuous extracellular matrix – basal lamina –
FUNCTIONS
• ________
- Skin protects from sunlight & bacteria & physical damage
- Lining of small intestine, absorbing nutrients into blood
- Lining of Kidney tubules filtering wastes from blood plasma
- Different glands produce perspiration, oil, digestive
enzymes and mucus
• Protection
• Absorption
• Filtration
• Secretion
ORIGIN: PRIMARY GERM LAYERS
1. ______
- Gives rise to the corneal epithelium, epidermis of the skin.
- Invagination – glandular appendages of the skin,
sudiparous, sebaceous, and mammary glands
2. _______
- Intestinal glands liver and pancreas
o Exocrine glands
o Endocrine glands
3. _______
- Kidneys and reproductive organs, lining of your blood and
lymph vessels, peritoneal cavity and other serous cavities
1. Ectoderm
2. Endoderm
3. Mesoderm
CHARACTERISTICS
• Form continuous sheets (fit like tiles)
• _________
- Topmost surface of epithelial tissue
- All epithelial cells have a top surface that borders an open space – known as a ________
- Basal surface of epithelial tissue
- Underside of all epithelial cells which anchors them to
connective tissue
• _________ (a = without)
- Lacks blood vessels and it is nourished by a connective
tissue.
• Regenerate & repair quickly
• Apical Surface
- All epithelial cells have a top surface that borders an open space – known as a lumen
• Basement Membrane
• Avascularity (a = without)
CLASSIFICATIONS
Cell Shape:
o _________
- Flattened like fish scales
- Their heights being very little as compared to their
width.
- Cubes
- The height and width of the cells of the epithelium
are more or less equal in size
o_________
- Columns
- The height of the cells of the epithelium is
distinctly greater than their width
• Cell Layers:
- One layer
- Many layers: Named for the type of cell at the apical surface
o Squamous
o Cuboidal
o Columnar
o Simple
o Stratified
- Many layers: Named for the type of cell at
the apical surface
- One or more cells that make and secrete a product.
- Secretion: protein in aqueous solution: hormones, acids, oils.
GLANDS
TYPES OF GLANDS
1. ___________
- No duct, release secretion into blood vessels
- Often hormones
- Thyroid, adrenal and pituitary glands
2. ___________
- Contain ducts, empty onto epithelial surface
- Sweat, Oil glands, Salivary glands, Mammary glands
- Shapes/Braches of Exocrine Glands:
• Branching
- ___________: single, unbranched duct
- ___________: branched
• Shape:
- ___________– shaped like a tube
- ___________ – shaped like flasks or sacs
- ___________ – has both tubes and sacs in gland
1. ENDOCRINE GLANDS
2. EXOCRINE GLANDS
- Simple: single, unbranched duct
- Compound: branched
- Tubular – shaped like a tube
- Alveolar – shaped like flasks or sacs
- Tubuloalveolar – has both tubes and sacs in gland
MODES OF SECRETION
- How the gland’s product is released
- Just released by exocytosis without altering the gland at all
- Ex: ___________ and ___________
- The gland ruptures and releases secretion and dead cells as well.
- Sebaceous (oil glands on the face) only example
- Includes whiteheads, blackheads and cellular debris on the skin.
1. Merocrine
- Ex: Sweat glands and salivary glands
2. Holocrine
- Sheetlike extracellular structure
- Visible only with ______ microscope (20-100 nm thick)
- Consists of a delicate network of fine fibrils – ______
- Electrolucent layers on both sides – lamina ______ or lamina ______
- Composed of type ______collagen, ______ and ______
• Type ____ collagen: Monomers of type ….. collagen self-
assembled into a two-dimensional network of evenly
spaced subunits
• ____: large glycoproteins that attach to
transmembrane proteins called integrins at the cells’
basal surface and project through the network of type IV
collagen
• ____ and ____: Respectively a short, rod-like
protein and a proteoglycan, both of these cross-link
laminins to the collagen network and help determine the
porosity of the basal lamina and the size of molecules
able to filter through it.
BASAL LAMINA
- Visible only with electron microscope (20-100 nm thick)
- Consists of a delicate network of fine fibrils – lamina densa
- Electrolucent layers on both sides – lamina rarae or lamina lucida
- Composed of type IV collagen, laminin and proteoglycan
(heparan sulfate)
• Type IV collagen: Monomers of type IV collagen self-
• Laminin: large glycoproteins that attach to
• Nidogen and Perlecan: Respectively a short, rod-like
Attached to the underlying connective tissues by anchoring structures (fibrils) – type ____ collagen
- Components of the basal lamina – secreted by the epithelial, muscle, adipose, and Schwann cells
- May also be closely related to ______ – forms a
layer(…… layer) – produced by connective tissues
Attached to the underlying connective tissues by anchoring structures (fibrils) – type VII collagen
- May also be closely related to reticular fibers – forms a
layer(reticular layer) – produced by connective tissues
- Basement membrane vs Basal lamina
• ________ denotes the fine extracellular layer seen
ultrastructurally
• ________: entire structure beneath the
epithelial cells visible with the light microscope
• Basal lamina: denotes the fine extracellular layer seen
• Basement membrane: entire structure beneath the
INTERCELLULAR COHESION
- Due to the binding action of glycoproteins in the plasma
membrane and calcium ions (________ bond)
- Intercellular junctions:
• _______ ( _________)
• _______
• _______ (_______ )
membrane and calcium ions (weak covalent bond)
• Tight junctions (Zonnulae Occludentes)
• Zonula adherens
• Gap junction
• Desmosome (macula adherens)
• Hemidesmosomes
- Tight junctions (singular ______)
- Forms a band completely encircling the cell
- Closes off the intercellular space
• On electron microscope – ______ appearance
• On cryofracture – replicas show anastomosing lines of
ridges (______) and grooves (______)
- The number of fusion sites or grooves correlate to the
“ ______” of the epithelium
- More fusion sites, less permeable epithelium
- Functions as a tight seal to prevent flow of materials
between cells
- The seal between the two cell membranes is due to tight
interactions between the transmembrane proteins
______ and ______
- In some epithelia there is an electric potential – for
transfer of molecules
- Ring of plasma union between cells
ZONNULAE OCCLUDENTES
- Tight junctions (singular zonnulae occludens)
• On electron microscope – pentalaminar appearance
ridges (P face) and grooves (E face)
“leakiness” of the epithelium
claudin and occludin
- Encircles the cell – distance is greater than the usual 20
nm in these areas
- Provides some adhesion of one cell to another
- Insertion of numerous actin-containing microfilaments
into dense plaques on the cytoplasmic surfaces
- These microfilaments arise from web of filaments
(_______) – provide rigidity to the terminal apex.
- _______ - found in cytoplasm of cells and gives
overall rigidity It also connects it to one lateral side to
other lateral sides.
ZONULA ADHERENS
(terminal web) – provide rigidity to the terminal apex.
- Terminal apex - found in cytoplasm of cells and gives
- ______: can occur almost anywhere on the lateral surface
- Close apposition of cell membranes (2 nm)
- On cryofracture – aggregates of intermembranous
particles found in______ patches
- ______- major protein, MW 26,000 – 30,000
- Proteins (______) form hexamers with a hydrophobic
pore (1.5 nm) – ______
• ______ - aligned to form a hydrophilic channel
between 2 cells → intercellular communications
GAP JUNCTION
- Nexus: can occur almost anywhere on the lateral surface
particles found in circular patches
- Polypetide- major protein, MW 26,000 – 30,000
- Proteins (Connexins) form hexamers with a hydrophobic
pore (1.5 nm) – Connexon
• Connexons - aligned to form a hydrophilic channel
????
- ________ – complex disk-shaped structure on the surface of one cell – matched to another cell
- Membranes are very straight in their regions and farther
apart (>30 nm)
- There is dense material intercellular plaques (attachment plaques) – groups of intermediate filaments of cytokeratin
DESMOSOME
- Macula adherens – complex disk-shaped structure on
the surface of one cell – matched to another cell
- There is dense material intercellular plaques
(attachment plaques) – groups of intermediate filaments
of cytokeratin
- On the contact points of epithelial cell and the basal
lamina
- Morphologically, half a desmosome
- ________ junctions → zonulae adherentes,
hemidesmosomes, and desmosomes
- ________ junctions→ zonulae occludentes
- ________ junctions →gap junctions
- ……..- means half - desmosomes
HEMIDESMOSOMES
- Adhering junctions→ zonulae adherentes,
- Impermeable junctions→ zonulae occludentes
- Communicating junctions →gap junctions
- Hemi - means half - desmosomes
SPECIALIZATION OF THE APICAL SURFACES OF EPITHELIA (3)
__________
microvilli
cilia (stereocilia, kiniocilia)
flagella
SPECIALIZATION OF THE APICAL SURFACES OF EPITHELIA
_________
- Few to numerous projections arising from the surface
(short or long)
- _________
• Longer folds lining of small intestines and proximal
renal tubules
- 1 μm high and 0.8μm wide
- _________ - filamentous coat of variable thickness,
contains glycoproteins
- _________ – extension – covered by plasma membrane
- Interiorly – cluster of 20-30 actin-containing
microfilaments that are cross-linked to each other and to
the surrounding plasma membrane – basal ends
intermingle with the filaments of the terminal web
MICROVILLI
- Microplicae
- Glycocalyx - filamentous coat of variable thickness,
- Microvillus – extension – covered by plasma membrane
CILIA:
- Long non-motile processes of cell (epididymis and
hair cells of the inner ear)
- Longer than microvilli
- Parallel to their base but become sinous at their tips
CILIA
1. STEREOCILIA
________
- Found on the cells for special transport of a mucous
film or fluid over a surface
- Rapid oscillations
- 7-10 μm in length and 0.2 μm in width
- Rapidly stiffen forward → ________ stroke then
more slow relaxation → ________ stroke
- May beat together (________stroke) or
________ stroke (successive rows in sequence) it is more
effective in transporting and usually found in
respiratory tract.
- “________” means kinetics
- Axoneme
• A core complex on EM
• Two single microtubules in the center with nine
doublet microtubules uniformly spaced around –
Central microtubules – 13 protofilaments, similar
to those in the cytoplasm
KINOCILIA
- Rapidly stiffen forward → effective stroke then more
slow relaxation → recovery stroke
- May beat together (isochronal stroke) or
metachronal stroke (successive rows in sequence) it is more effective in transporting and usually found in
- “Kino” means kinetics
- Peripheral microtubules
• Subunit ____
o Complete microtubule (13 protofilaments)
o Incomplete microtubule (10 protofilaments)
• A radial spoke extends from each subunit A to the
central pair
• Subunit A of each doublet is connected by fine ______
to the subunit B of the next doublet
• Short ______ arms project from subunit A to the
subunit B of the next doublet
o 24 nm intervals
• Subunit A
• Subunit B
• Subunit A of each doublet is connected by fine
nexin to the subunit B of the next doublet
• Short dynein arms project from subunit A to the
FLAGELLA
- Internal structure very similar to cilia but longer (15 -
200μm)
- Not commonly found in the body (only in the free-
swimming spermatozoa)
- Undulating movement
• More of propeller’s movement (like ribbon
movement) and they have a lot of energy to move
Simple Squamous Epithelium
- Walls of capillaries, air sacs in lungs
- Form serous membranes in body cavity
- Lines the inside of the heart, where it is called
endocardium; and of blood vessels and lymphatics,
where it is called endothelium.
- Lines some parts of the renal tubules, and in some
parts of the internal ear
Simple Cuboidal Epithelium
-Glands and ducts (pancreas & salivary), kidney
tubules, covers ovaries (germinal epithelium)
- Follicles of Thyroid gland
- Choroid plexuses
- Inner surface of the lens, and the pigment cell layer
of the retina
Simple Columnar Epithelium
- Linings of entire digestive tract
- Ciliated columnar epithelium lines most of the
respiratory tract, the uterus, and the uterine tube
- It is also seen in the efferent ductules of the testis,
parts of the middle ear and auditory tube
- Ependyma lining the central canal of the spinal cord
and the ventricles of the brain
- Special Features:
•Microvilli: bumpy extension of apical surface,
increase surface area and absorption rate.
•Goblet cells: single cell glands, produce protective
Pseudostratified Epithelium
- Respiratory Linings & Reproductive tract
- Some parts of the auditory tube
Stratified Squamous Epithelium
- Skin (keratinized), mouth & throat
Best morphology for protection
Zuletzt geändertvor 2 Jahren