Histology of Epith _med_ June 28 2011

8/3/2019 Histology of Epith _med_ June 28 2011

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HISTOLOGY OFEPITHELIAL

TISSUERowena F. Genuino, MD

Department of Anatomy

Not to be copied without permission


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EPITHELIUM

Sheet of closely

adherent cells

covering anaturally occurring

surface

CT

2Not to be copied without permission


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FUNCTIONS OF

EPITHELIUM SELECTIVE BARRIER

ABSORPTION

SECRETION

PROTECTION

OTHERS - Sensation, Contractility,Transport



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EPITHELIUM

EXTERNAL COVERING Skin

INTERNAL LINING

CLOSED CAVITIES Peritoneal, Pleural, Pericardial

cavities

Blood vessels

OPEN-ENDED TUBES

Dig, GU, Resp

SECRETORY UNITS Glands



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CHARACTERISTICS

OF EPITHELIUM HIGHLY CELLULAR(scanty ECM)

+ IC JUNCTIONS POLAR

Apical (e.g. microvilli)

Lateral (IC jxns)

Basal (BM)

SELF-RENEWING

Stem cells



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EPITHELIUM (Light

microscope)



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CLASSIFICATION

OF EPITHELIUM

Based on No. of layers

SIMPLE vs STRATIFIED

Absorption Protection

Exchange Barrier

Secretion Not to be copied without permission


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Based on cell shape

SQUAMOUS CUBOIDAL

COLUMNARNot to be copied without permission


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SIMPLE EPITHELIA



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Endothelium

SURFACE VIEW, SEMSIDE VIEW Not to be copied without permission


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MESOTHELIUM

SURFACE VIEWSIDE VIEW

MESOTHELIUM + some CT =

SEROSA



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SIMPLE CUBOIDAL

Kidney tubule

SIMPLE CUBOIDAL EPITHELIUM



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SIMPLE COLUMNAR

Lining of galbladder



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PSEUDOSTRATIFIED

EPITHELIUM Single layer butto different levels ofnuclei

Some cells do not reachthe apical surface(=basal cells), theirnuclei are in lower layers

Limited distribution: resp& male reproductive tract



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PSEUDOSTRATIFIED

BRONCHUS

TRACHEA

Others:Vas deferens

Epididymis



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STRATIFIED EPITHELIUM



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STRATIFIED SQUAMOUS NON-KERATINIZING

Uterine cervix

Skin

STRATIFIED SQUAMOUS

KERATINIZINGNot to be copied without permission

(


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STR. SQ. NON-KER EPITH (Vagina)



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STRATIFIED CUBOIDAL

Larger excretory duct of salivary gland



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TRANSITIONAL EPITHELIUM

Barrier Distensible due to

ability to change

number of layers

Urinary tract



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TRANSITIONAL

Urinary bladder (contracted)


TRANSITIONAL EPITH


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TRANSITIONAL EPITH

(Urinary bladder)



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SURFACE

MODIFICATIONS

APICAL LATERAL

BASAL



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APICAL MODIFICATIONS

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CILIA MICRO

VILLI

STEREO

CILIA



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MICROVILLI Closely packed --

increases absorptivesurface (small

intestine, kidney)

Finger-like

evaginations of PM ---

Upright parallel array

due to core of actin

filaments Anchored to terminal

web for rigidity



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MICROVILLI (=Brush/Striated

border under LM)



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MICROVILLI

IDNEY TUBULE

SMALL INTESTINE



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STEREOCILIA

Non-motile

=Elongated microvilli

Absorptive (seminalfluid in male

reproductive tract);

Sensory (ear)

Long, thin, clumped

at ends



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STEREOCILIA


CILIA


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CILIA Motile

Move mucus/ovum

across surface (resp

tract/oviduct) Core of

microtubules

(=axoneme)

Attached to basalbody



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CILIA Axoneme = 9 + 2pattern

9 peripheral doublets2 central singlets

Basal body = 9 + 0

pattern

9 peripheral triplets



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CILIA

DYNEIN ARMS



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CILIA



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CILIA

OVIDUCT

TRACHEA



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JUNCTIONAL

COMPLEX

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Occluding jxn

Tight jxnAnchoring jxns

Intermediate jxn

Desmosome

Hemidesmosome

CommunicatingGap jxn


ZONULA


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ZONULA

OCCLUDENS

Unique to epith Narrow gap where PM

of adj cells come in

contact in many fusion

sites

Occludins (transmemb

proteins)

Seals the IC space/

Maintains polarity



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ZONULA OCCLUDENS


ZONULA


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ZONULA

OCCLUDENS Anastomosing network ofridges+grooves= fusionsites


ZONULA


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ZONULA

ADHERENS

Wider IC space

(+) IC filaments

cytoplasmic denseplaques to which actin

filaments are anchored

Actin filaments attached

to terminal web



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ZONULA ADHERENS



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MACULA ADHERENS

(DESMOSOMES) Discontinuous spot

welds/buttons

Wider IC space than ZA w/ intercellular linked

filaments

Cytoplasmic attachment

plaque Attached to Interm.

Filaments

anchor/loop back todissipate physical forces



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MACULA ADHERENS

Only jxn present in

stratified squamous

epith



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HEMIDESMOSOME

Between basal epith.

cells and underlying

BM where (+) abrasion &

shearing forces

Cornea, skin, mucosa

of oral cavity,esophagus, vagina



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TERMINAL BAR



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NEXUS (=GAP JUNCTION)

Closely apposed PM

but no fusions

Connexons IC communication



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BASAL SURFACE

MODIFICATIONS

BASAL LAMINA 50-100 nm thick

EM: 2 layers (l. lucida + l. densa)

=EXTERNAL LAMINA (when it surrounds nerve-

supporting cells & muscle cells)

=BASEMENT MEMBRANE (when very thick, seen

under LM, BL +underlying CT fibers)



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FUNCTIONS OF BASAL

LAMINA Attachment

Selective barrier

Polarity

Tissue scaffolding - wound healing,

repair



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BASEMENT

MEMBRANE

BASAL LAMINA

LAMINA LUCIDA

laminin

LAMINA DENSA

Type IV collagen

Proteoglycans Fibronectin

SUB-LAMINA

DENSA

Anchoring fibrils

(Type VII coll)


BASEMENT MEMBRANE


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BASEMENT MEMBRANE

GLOMERULUS TRACHEA



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GLANDS

Groups of epithelial

cells specialized forsecretion

Varied


GLANDULAR


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GLANDULAR

EPITHELIAL

TISSUE


/ DUCTS


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+/- DUCTS



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EXOCRINE

GLANDS UNICELLULAR GOBLET CELL

(resp/int)

MULTICELLULAR

SECRETORY

EPITHELIAL SHEET

(gastric) TRUE

INVAGINATION



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CLASSIFICATION OF

EXOCRINE GLANDS BASED ONBRANCHING SIMPLE

COMPOUND BASED ON SHAPE

OF SECRETORYPORTION

TUBULAR ACINAR

TUBULO-ACINAR

SACCULARNot to be copied without permission

SIMPLE


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SIMPLE

TUBULAR

GLANDColon


SIMPLE TUBULAR GLAND


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SIMPLE TUBULAR GLAND(Colon)



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SIMPLE

COILEDTUBULAR

Sweat gland



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SIMPLE

BRANCHED

ACINARSebaceous gland



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COMPOUNDBRANCHED

TUBULAR

Duodenal glands



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COMPOUND

TUBULO-

ACINARPancreas


Pancreas


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Pancreas


COMPOUND TUBULO ACINAR


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COMPOUND TUBULO-ACINAR

GLAND

Submandibular gland



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COMPOUND SACCULARMAMMARY GLAND PROSTATE GLAND


TYPE OFMUCOUS


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SECRETION MUCOUS

mucin - viscous fluid

rich in mucopolys

protective or lubricating

function

pale cytoplasm (mucin-

filled)

flattened nucleus

SEROUS

watery secretion

Enzyme-rich

spherical nuclei

dark staining cytoplasm

(secretory granules)

Esophageal

Mucous gland

Pancreas



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SEROUS-SECRETING CELL

(PANCREATIC ACINAR CELL)



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MIXED SEROMUCOUS

ACINI (Submandibular gland)

SEROUS DEMILUNE


A OC


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MODE OF

SECRETION MEROCRINE

Pancreas, etc

APOCRINE Mammary gld

HOLOCRINE

Sebaceous gland

APOCRINE

HOLOCRINE Not to be copied without permission

ORGANIZATION OF LARGE


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ORGANIZATION OF LARGE

EXOCRINE GLANDS

Example: pancreas

Capsule - condensation of

CT

Septa - extend inward fromcapsule to divide gland into

lobes

Thinner septa - further

divide into lobules Reticular fibers - delicate

network which surrounds

aciniNot to be copied without permission


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EXOCRINE GLANDS

CT component --

STROMA

Epithelialcomponent --

PARENCHYMA



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DUCTAL SYSTEM OF

EXOCRINE GLANDS Intercalated duct Striated duct

Intralobular duct

Interlobular duct

Lobar duct

Main duct


ENDOCRINE GLANDS


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ENDOCRINE GLANDS

Ductless, lessorganized, cellsarranged in cords &

columns except for thyroid

gland (rounded unitsenclosing storedhormone precursors)

Highly vascular

Hormones - distanttarget organs

PITUITARY GLAND

THYROID GLANDNot to be copied without permission

ORGANIZATION OF


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ORGANIZATION OF

ENDOCRINE

GLANDS DISCRETE ORGANS

Cords Adrenal, Hypophysis

Follicles Thyroid

SMALL ISLANDS withinan Exocrine gland

Leydig cells in testis Islets of Langerhans in

pancreas



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THE END

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Histology of Epith _med_ June 28 2011