Download - 2 Epithelial Tissue
-
7/29/2019 2 Epithelial Tissue
1/84
EPITHELIAL TISSUE
-
7/29/2019 2 Epithelial Tissue
2/84
EPITHELIAL TISSUE - Introduction
n The outer surface of the body and the luminalsurfaces of cavities within the body are lined
by continuous cellular sheets called
Epithelial Membranes orepithelia
n which along with various glands that developfrom them, constitute epithelial tissue
-
7/29/2019 2 Epithelial Tissue
3/84
EPITHELIAL TISSUE - Origin
n Epithelial component of skin arises fromectoderm
n Epithelial lining and glands of the digestivetract are derived from endoderm
n Serous linings of the peritoneal, pleural,pericardial cavities, and also the circulatory
system, are products ofmesoderm
-
7/29/2019 2 Epithelial Tissue
4/84
EPITHELIAL TISSUE - Functions
n Epithelia mediate a wide range of activitiessuch as
q Selective diffusionqAbsorptionq Secretionq Physical protection and containment
-
7/29/2019 2 Epithelial Tissue
5/84
EPITHELIAL TISSUE Common
Characteristicsn Cell Junctionsq Membrane specializations that bind adjacent
epithelial cells
n Basement Membraneq Membrane which separates epithelia from
underlying supporting tissue
n Polarityq Basal surfaceqApical surface
-
7/29/2019 2 Epithelial Tissue
6/84
Classification of epithelium
n Epithelial membranes are classified according to thenumber of constituent cell layers and the cell
shape at the free surface
n Simple epithelium - Single layer of cellsn Stratified epithelium At least 2 layers thickn Pseudostratified epithelium - epithelium is only
one cell thick, but it gives the impression of being
stratified because some of its cells are shorter thanothers and therefore do not reach its free surface
-
7/29/2019 2 Epithelial Tissue
7/84
EPITHELIAL TISSUE Other Names
nEndotheliumq Epithelial tissue lining the blood vesselsq Derived from Mesoderm
n Mesotheliumq Epithelial tissue lining the serous body cavities like
pleura, pericardium, & peritoneum
q Derived from Mesodermn Glandular Epithelium
q Epithelium that is primarily involved in secretion isoften arranged into structures called glands
-
7/29/2019 2 Epithelial Tissue
8/84
SIMPLE EPITHELIA
n Consists of a single layer of cellsn Found at interfaces involved in selective
diffusion, absorption and/or secretion
n Provide little protection against mechanicalabrasion
n Cells range in shape from extremely flattened totall columnar cells
n Exhibit a variety of surface specializations, suchas microvilli and cilia, which facilitate their
specific surface functions
-
7/29/2019 2 Epithelial Tissue
9/84
SIMPLE SQUAMOUS EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
10/84
SIMPLE SQUAMOUS EPITHELIUM
n Pavement Epitheliumn Consists of a single
layer of flat, scale
shaped cellsn Best suited in areas
where the primary
function is diffusion
q Lungs Gasesq Capillaries - Fluids
-
7/29/2019 2 Epithelial Tissue
11/84
SIMPLE SQUAMOUS EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
12/84
SIMPLE SQUAMOUS EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
13/84
SIMPLE SQUAMOUS EPITHELIUM Silver Method/Neutral Red preparation
-
7/29/2019 2 Epithelial Tissue
14/84
SIMPLE SQUAMOUS EPITHELIUM
n Common sites:q Alveoli of lungsq Free surface of serous pericardium, of the pleura, & of the
peritoneum collectively called as Mesothelium
q Inside of the heart called as Endocardiumq Inside (luminal side) of the blood vessels called as
Endothelium
q Thin walled tubules in the renal medullaq Some parts of Inner ear
-
7/29/2019 2 Epithelial Tissue
15/84
SIMPLE CUBOIDAL EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
16/84
SIMPLE CUBOIDAL EPITHELIUM
nConsists of single layer ofcuboidal cells
n In transverse section thecells appear square
n Best suited for areas withexcretory, secretory, &
absorptive functions
q Collecting tubules of thekidney and the smallexcretory ducts of the
salivary glands andpancreas
-
7/29/2019 2 Epithelial Tissue
17/84
SIMPLE CUBOIDAL EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
18/84
SIMPLE CUBOIDAL EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
19/84
SIMPLE CUBOIDAL EPITHELIUM
n Common sites:q Follicles of thyroid glandq Ducts of many glandsq
Surface of ovary called as Germinal Epitheliumq Choroid plexusq Inner surface of lensq Pigment cell layer of retina
-
7/29/2019 2 Epithelial Tissue
20/84
SIMPLE COLUMNAR EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
21/84
SIMPLE COLUMNAR EPITHELIUM
n Consists of single layer of tallcolumnar cells
n Best Suited in places withabsorptive function like Small
Intestine or Places withsecretory function likeStomach & gall bladder
n Seen in linings of minor ductsof many exocrine glands
-
7/29/2019 2 Epithelial Tissue
22/84
SIMPLE COLUMNAR CILIATEDEPITHELIUM
-
7/29/2019 2 Epithelial Tissue
23/84
SIMPLE COLUMNAR EPITHELIUM
n Simple secretory columnarepitheliumq Mucous secreting as well as
protective
q No cilia or microvilli
n Simple ciliated columnarepitheliumq Cilia cover the free surface
n Simple columnar epitheliumwith microvilliq Striated borderq Brush border
-
7/29/2019 2 Epithelial Tissue
24/84
SIMPLE COLUMNAR EPITHELIUM
Goblet Cells: The apical parts of the secretory epithelium contains mucouscontaining vesicles which are light staining. These cells are called Goblet cells.
-
7/29/2019 2 Epithelial Tissue
25/84
SIMPLE COLUMNAR EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
26/84
SIMPLE COLUMNAR EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
27/84
SIMPLE COLUMNAR EPITHELIUM
n Common sites:q Simple columnar (without cilia or microvilli)
n Lines the stomach, uterine cervix, & large intestineq Simple ciliated columnar
n Seen in most of respiratory tract, uterus, & uterine tubesn Also seen in efferent ductules of testis, parts of middle ear &
auditory tube, ependyma lining central canal of spinal cord, &ventricles of brain
q Simple columnar with microvillin Striated border
q Small intestinen Brush border
q Gall bladder
-
7/29/2019 2 Epithelial Tissue
28/84
-
7/29/2019 2 Epithelial Tissue
29/84
PSEUDOSTRATIFIED COLUMNAREPITHELIUMn All component cells lie in
contact with the basement
membrane
n Nuclei are visible at more thanone level
n Some of its cells are shorterand do not reach its free
surface
n Pseudostratified ciliatedcolumnar epitheliumq With scattered goblet cells,
lines most of the major airways
-
7/29/2019 2 Epithelial Tissue
30/84
PSEUDOSTRATIFIED COLUMNAREPITHELIUM
-
7/29/2019 2 Epithelial Tissue
31/84
PSEUDOSTRATIFIED COLUMNAREPITHELIUM
-
7/29/2019 2 Epithelial Tissue
32/84
PSUEDO-STRATIFIED EPITHELIUM
n Common sites:q Some part of auditory tubeq Ductus deferensq Male urethra (membranous & penile part)
n Ciliated pseudostratified columnar epitheliumq Trachea & in large bronchi
-
7/29/2019 2 Epithelial Tissue
33/84
STRATIFIED EPITHELIA
n Consists of two or more layers of cells
n Mainly perform protective function
n Poorly suited for absorption and secretion
-
7/29/2019 2 Epithelial Tissue
34/84
STRATIFIED SQUAMOUS EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
35/84
STRATIFIED SQUAMOUS EPITHELIUM
n Several layers of cellsn Cells of deepest (or basal) layer rest on basement
membrane & are usually columnar in shape
n As we go to periphery (basal to outer layers) Cellsbecome polyhedral or cuboidal and eventually become
squamous.
n Sub-typesq Non-keratinizedq Keratinized
-
7/29/2019 2 Epithelial Tissue
36/84
STRATIFIED SQUAMOUS NONKERATINIZING EPITHELIUM
n Cells on surface layer hasnuclei & are living
n It lines the wet surfacessubmitted to wear and tear
n Lines the inside of the mouth,the esophagus, the vagina, &the cornea
-
7/29/2019 2 Epithelial Tissue
37/84
STRATIFIED SQUAMOUS NONKERATINIZING EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
38/84
STRATIFIED SQUAMOUSKERATINING EPITHELIUM
n The cells near the free surfacetransform into scales of soft
keratin that remain strongly
adherent to the underlying
layers of living cellsn These cells are dead & lose
their nuclei
n Suitable for protecting surfacesn Seen in epidermal layer of
skin
n Resists water loss and uptake
-
7/29/2019 2 Epithelial Tissue
39/84
STRATIFIED SQUAMOUSKERATINING EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
40/84
SQUAMOUS CELL CARCINOMA
-
7/29/2019 2 Epithelial Tissue
41/84
STRATIFIED CUBOIDAL EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
42/84
-
7/29/2019 2 Epithelial Tissue
43/84
TRANSITIONAL EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
44/84
TRANSITIONAL EPITHELIUM
n The microscopic appearanceof Transitional epitheliumchanges as the membranestretches
n In the unstretchedconfiguration usually seen insections, the roundedsuperficial cells bulge out
n Under lateral tension, thesecells are attenuated andsquamous
n Lines almost all ofthe urinarytract.( urinary bladder , ureter )
n Some surface cells of thebladder are multinucleated
-
7/29/2019 2 Epithelial Tissue
45/84
TRANSITIONAL EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
46/84
TRANSITIONAL EPITHELIUM
-
7/29/2019 2 Epithelial Tissue
47/84
MEMBRANESPECIALIZATIONS
Cell Junctions, Cilia, Microvilli, & Stereocilia
-
7/29/2019 2 Epithelial Tissue
48/84
CELL JUNCTIONS
n Tight junctions or Occluding junctions (Zonulaoccludens)
n Adhering junctionsq Adhesive spots (Desmosomes or macula adherens)q Adhesive belts (Zona adherens)q Adhesive strips (Fascia adherens)q Hemidesmosomes or focal spots
n Gap junctions or Communicating junctions
-
7/29/2019 2 Epithelial Tissue
49/84
Junctional complex
-
7/29/2019 2 Epithelial Tissue
50/84
Tight junctions ( Zonula Occludens)
n Formed by fusion ofopposed cell
membranes
nIt extends completelyaround apical cell
border
-
7/29/2019 2 Epithelial Tissue
51/84
Tight Junctions
-
7/29/2019 2 Epithelial Tissue
52/84
Tight junctions ( Zonula Occludens)
n Transmembrane proteins form the so-called sealing strands that 'stitch' the
membranes together
n Each 'stitch' comprises two molecules ofthe transmembrane protein claudin, one
an integral part of each opposing plasmamembrane, linked tightly together
-
7/29/2019 2 Epithelial Tissue
53/84
TIGHT JUNCTIONS
n Act as barriers that prevent movement of molecules intointercellular spaces
n Seen in between cells of membranes that arespecialized for absorption or secretion
n Prevent leakage of substances absorbed by cells againstconcentration gradient
n Leaky tight junctionsq Incomplete tight junctions
-
7/29/2019 2 Epithelial Tissue
54/84
Fascia Occludens
n Structurally similar but discontinuous strips oftight junctions
n Found between the endothelial cells liningblood vessels, except in the vessels of the
brain where they are of the continuous
(zonula occludens) type
-
7/29/2019 2 Epithelial Tissue
55/84
-
7/29/2019 2 Epithelial Tissue
56/84
Desmosomes
n Most common type of cellular junction
n The fibrils seen in the intercellular space (linking the twoplaques) represent CAMs (Cellular adhesion molecules)
n CAMs normally seen areq Integrins (Desmogleins I, II)q Desmoplakinsq Plakoglobin
-
7/29/2019 2 Epithelial Tissue
57/84
Zonula Adherens
n This lies basal to Zonula Occludensn It extends continuously around celln Major site of attachment of microfilaments to
cell membrane. Many of these microfilamentsare arranged circumferentially as marginal
band
n CAMs present are cadherins
-
7/29/2019 2 Epithelial Tissue
58/84
Zonula Adherens
n Differ from Macula adherensq By forming a continuous band passing all around the apical part
of the epithelial cells
q By not having a filaments traverse the gaps between the cells
-
7/29/2019 2 Epithelial Tissue
59/84
Fascia Adherens
n Similar to Zonular adherensn Differ by not going all around the cells (form strips of
attachment)
n Seen in smooth musclesn Intercalated discs of cardiac musclesn Junctions between glial cells & neurons
-
7/29/2019 2 Epithelial Tissue
60/84
-
7/29/2019 2 Epithelial Tissue
61/84
-
7/29/2019 2 Epithelial Tissue
62/84
i l C l
-
7/29/2019 2 Epithelial Tissue
63/84
Junctional Complex
B b
-
7/29/2019 2 Epithelial Tissue
64/84
Basement membrane
n Matrix structure called a basementmembrane strongly attaches epithelial cells
to the adjacent connective tissue
n Basement membrane is made up off twoadjacent basal lamina or more commonly
basal lamina and reticular lamina.
B b
-
7/29/2019 2 Epithelial Tissue
65/84
Basement membrane
n Basal lamina is made up ofq Type IV collagenq Lamininq Heparan sulphate
n Reticular laminaq Reticular fibers
-
7/29/2019 2 Epithelial Tissue
66/84
EPITHELIAL GLANDS
EPITHELIAL GLANDS
-
7/29/2019 2 Epithelial Tissue
67/84
EPITHELIAL GLANDS
n Are subdivided intoq Exocrine glandsq Endocrine glands
n Exocrine Glandsq Develop as down growths of an epithelial membrane and
secrete onto its surface through their ducts
n Endocrine glandsq Are ductless, they release their secretory product close to
the external surface of thin walled blood vessels. (Product
enters blood stream).
-
7/29/2019 2 Epithelial Tissue
68/84
EPITHELIAL GLANDS
-
7/29/2019 2 Epithelial Tissue
69/84
EPITHELIAL GLANDS
n Goblet cellsq Mucous secreting uni-
cellular exocrine glands
q They assume shape ofgoblet because secretory
vesicles accumulate and
compress neighboring cells
q Nucleus lies in stem likebasal region
qSynthesis of Mucus beginsat rER and glycosylation is
completed in golgi
apparatus
G bl ll
-
7/29/2019 2 Epithelial Tissue
70/84
Goblet cell
E i l d
-
7/29/2019 2 Epithelial Tissue
71/84
Exocrine glands
n Made up ofq Secretory unitq Duct with its supporting connective tissue
n Secretory unitq Group of epithelial cells that release their
secretion into a lumen
nDuctq Epithelially lined tube that conveys the secretion
to epithelial surface
Gl d
-
7/29/2019 2 Epithelial Tissue
72/84
Glands
n Simple glandqA gland with a single unbranched ductq E.g. Sweat gland
n Compound glandqA gland with a branching tree like duct systemq E.g. Pancreas
Si l Gl d
-
7/29/2019 2 Epithelial Tissue
73/84
Simple Gland
-
7/29/2019 2 Epithelial Tissue
74/84
C mp nd rin l nd
-
7/29/2019 2 Epithelial Tissue
75/84
Compound exocrine glands
n Parenchymaq Epithelial component
n Stromaq Supporting connective tissue (Together with blood
vessels and nerve fibres)
n Capsuleq
Gland is enclosed by a fibrous connective tissue
-
7/29/2019 2 Epithelial Tissue
76/84
-
7/29/2019 2 Epithelial Tissue
77/84
Depending on the type of secretory
-
7/29/2019 2 Epithelial Tissue
78/84
Depending on the typeofsecretoryproduct
n Serous glandsq Produce watery
secretions
n Mucous glandsq Produce viscid mucus
n Mixed glands
Serous glands Vs Mucous glands
-
7/29/2019 2 Epithelial Tissue
79/84
Serous glands Vs Mucous glands
n Serous glandsq Brightly stainedq Basal part is basophilic
q Large spherical nucleus
n Mucous glandsq Appear paleq Mucus can be stained by
PAS stain
q Nucleus small flattenedagainst basal cell boarder
Serous Mucus and Mixed secretory units
-
7/29/2019 2 Epithelial Tissue
80/84
Serous, Mucus and Mixed secretory units
-
7/29/2019 2 Epithelial Tissue
81/84
-
7/29/2019 2 Epithelial Tissue
82/84
Secretory cells of exocrine glands also can
-
7/29/2019 2 Epithelial Tissue
83/84
Secretory cells of exocrine glands also canbe differentiated inton Merocrine glands (eccrine or epicrine)
q Release their secretion by Exocytosisq E.g. Pancreatic acinar cells
n Holocrine glandq Entire cell is sacrificed in producing the secretionq E.g. Sebaceous glands associated with hair follicle
n Apocrine glandq The apical portions are sacrificed during releaseq Eg: Atypical Sweat glands
Endocrine glands
-
7/29/2019 2 Epithelial Tissue
84/84
Endocrine glands
n Instead of releasing their secretions intoducts, they discharge them into the blood
stream
n Secretions of endocrine glands are calledhormones
n They elicit functional changes in target cells