EPITHELIAL TISSUE

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• EPITHELIAL TISSUE
• CONNECTIVE TISSUE
• MUSCULAR TISSUE
• NERVOUS TISSUE

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Respiratory Passages Pleural cavities Hart
and Blood vessels Pericardium
Oral cavity Skin Digestive Tract Peritoneum
Urinary tracts Glands Limph vessels
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FUNCTIONS OF EPITHELIA

• COVERING EPITHELIA
• covering of surfaces and lining of cavities
• protection of covered tissue
• absorption - intestines, proximal tubules of
  kidney
• GLANDULAR EPITHELIA
• secretion - exocrine glands
• NEUROEPITHELIAL CELLS
• sensation - olfactory epithelium , taste buds
• MYOEPITHELIAL CELLS
• contractility - salivary glands, sweat glands

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COMPONENTS OF BASAL LAMINA

• COLLAGEN TYPE IV
• LAMININ, FIBRONECTIN (glycoproteins)
• PROTEOGLYCANS - (HEPARAN SULFATE)
• ANCHORING FIBRILS - COLLAGEN TYPE VII

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FUNCTIONS OF BASAL LAMINA

• Selective barrier between connective tissue and
  epithelium
• Adhesion of the connective tissue and the
  epithelium

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POLARITY OF EPITHELIA

• APICAL SURFACE
• BASAL SURFACE - rests on basal lamina

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TYPES OF EPITHELIA

• ACCORDING TO NUMBER OF LAYERS
• simple
• stratified
• pseudostratified
• ACCORDING TO SHAPE OF CELLS
• squamous
• cuboidal
• columnar

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• SIMPLE SQUAMOUS EPITHELIUM
• endothelium, mesothelium

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SIMPLE SQUAMOUS EPITHELIUM
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• SIMPLE CUBOIDAL EPITHELIUM
• proximal and distal renal tubules

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• SIMPLE CUBOIDAL EPITHELIUM

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• SIMPLE COLUMNAR EPITHELIUM
• stomach, small and large intestine, oviduct

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• SIMPLE COLUMNAR EPITHELIUM

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• PSEUDOSTRATIFIED EPITHELIUM
• respiratory passages, epididymis

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• STRATIFIED SQUAMOUS EPITHELIUM
• keratinised - skin
• nonkeratinised - oral cavity, vagina

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STRATIFIED SQUAMOUS EPITHELIUM
keratinised nonkeratinised
Skin
Cornea
Esophagus
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• STRATIFIED COLUMNAR EPITHELIUM
• ocular conjunctiva

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• TRANSITIONAL EPITHELIUM
• urinary bladder, ureter

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INTERCELLULAR JUNCTIONS

• membrane associated structures responsible for
  cohesion and communication between cells
• ADHERING JUNCTIONS
• IMPERMEABLE JUNCTIONS
• COMMUNICATING JUNCTIONS

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TIGHT JUNCTION - ZONULA OCCLUDENS

• LOCATION - the most apical
• SHAPE - band encircling the cell
• MORPHOLOGY - network of linear fusion sites
  between membrane associated proteins
• FUNCTION - close off the intercellular space
  (leakiness of the epithelium)

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TIGHT JUNCTION - ZONULA OCCLUDENS
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TIGHT JUNCTION - ZONULA OCCLUDENS
Prevent the flow between the cells
Prevent the movement of membrane proteins
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DESMOSOME
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DESMOSOME -MACULA ADHERENS

• LOCATION - along the lateral membranes
• DISK-SHAPED
• MORPHOLOGY -
• attachment plaques - desmoplaquin
• intercellular space - desmoglein
• cytokeratin filaments
• FUNCTION - very firm adhesion of neighbor-cells

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ZONULA ADHERENS
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ZONULA ADHERENS

• LOCATION - just below tight junction
• SHAPE - band encircling the cell
• MORPHOLOGY -
• dense plagues - a-actinin, vinculin,
  myosin, tropomyosin
• intercellular space - E-kadherin and
  calcium ions
• actin-containing microfilaments
• FUNCTION - adhesion of neighbor-cells

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HEMIDESMOSOME

• LOCATION - contact zone between epithelium and
  basal lamina
• DISK-SHAPED
• MORPHOLOGY - half a desmosome
• FUNCTION - binds the epithelial cell to basal
  lamina

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INTERCELLULAR JUNCTIONS

• Electron transmission microscope

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GAP JUNCTION -NEXUS

• LOCATION - anywhere along the lateral membranes
  of epithelial cells
• MORPHOLOGY - hexamers of proteins with a
  hydrophilic pore in the center (connexon)
• FUNCTION - interchange of small molecules
  between adjacent cells (cyclic AMP, ions)

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GAP JUNCTION -NEXUS
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GAP JUNCTION - NEXUS
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MICROVILLI

• Extension of cytoplasm - 1mm long
• Actin-containing microfilaments
• FUNCTION - increase the surface area
• LIGHT MICROSCOPE - BRUSH BORDER

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MICROVILLI
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MICROVILLI brush border
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CILIA

• LONG PROJECTIONS - 10 mm
• MOTILE
• STRUCTURE
• central pair of microtubuls
• 9 pairs at the periphery
• INSERTED INTO BASAL BODIES
• FUNCTION - permit a current of material over
  epithelium

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CILIA
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STEREOCILIA - long microvilliFLAGELLA -
similar in structure to cilia
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GLANDULAR EPITHELIA - Glands

• FUNCTION - secretion of products which are used
  in other parts of the organism

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SEROUS GLANDS

• ACINAR SECRETORY PORTIONS
• SECRET CLEAR FLUID SECRETION
• SEROUS CELLS
• ruonded nucleus at basal part of cytoplasm

• abundant RER
• basophilic cytoplasm
• well visible secretory granules at the apex

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SEROUS CELLS
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MUCOUS GLANDS

• TUBULAR SECRETORY PORTIONS
• SECRET MUCUS
• MUCOUS CELLS
• flat nucleus at the basis
• large, translucent secretory granules
• well developed Golgi complex

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SUBLINGUAL GLANDS
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TYPES OF EXOCRINE GLANDS
APOCRINE secretory product is discharged with
apical part of cytoplasm
HOLOCRINE secretory product is shed with whole
cell

• MEROCRINE
• secretory granules leave the cell by exocytosis

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NUTRITION OF EPITHELIA

• NO BLOOD VESSELS IN EPITHELIA
• NUTRIENTS AND PRECURSORS OF PRODUCTS DIFFUSE FROM
  CONNECTIVE TISSUE ACROSS THE BASAL LAMINA TO
  EPITHELIAL CELLS

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RENEWAL

• REPLACEMENT OF OLD CELLS BY NEW ONES
• MITOTIC DIVISIONS
• OCCUR IN ALL EPITHELIA