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Epithelial tissue(Textus epithelialis)

E-Learning :December 10, 2010ghufron_histo@yahoo.co.id

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HISTOLOGY

Four Basic Types of Tissue

1. Epithelial

2. Connective

3. Muscle

4. Nerve

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Includes glands and epithelium.

Glands are secretory

Some characteristics:1. is avascular

2. forms a protective barrier that regulates permeability

3. cells may show polarity

4. regeneration (highly mitotic)5. all epithelial contact with a sheet like extracellular structure

called the basal lamina/basal membrane

Epithelial tissue

Textus epithelialis)

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1. Physical protection

2. Control permeability

3. Provide sensation

4.

Produce specialized secretions

Functions of epithelium

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The Polarity of Epithelial Cells

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EPITHELIAL TISSUE

(Textus epithelialis)

Cells are bound tightly together

Little extracellular materialArranged in sheets

Cover internal and external surfaces

Often control passage of material

Classified by shape of cells and number of layers

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CELL SHAPE

Squamous shape

* Thin, flat cells

* Look like fried eggs

Cubodial shape

* square shape- cross

section

* 6 sided polygon- surfaceColumnar

* Rectangular- cross section

* Polygonal-surface view

CELL NUMBERSimple

* Single layer

Stratified

* > 2 layers

Pseudostratified

* Appear stratified- but not

Transitional

* Change shape

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SIMPLE SQUAMOUS

Single layer

Squamous shape

Lining of body cavity, lungs,blood vessels

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STRATIFIED SQUAMOUS

Multi layer

Outer most layer- squamous

cells

Inner- cuboidal or columnar

Lining of mouth, esophagus,

skin

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epithelium stratificatum

squamosum noncornificatum

epithelium stratificatum

squamosum cornificatum

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SIMPLE CUBOIDAL

Single layer

Cuboidal shaped

Kidney tubules, glands

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SIMPLE COLUMNAR

Single layer

Columnar shape

Lining of digestive tract

Modified by presence of cilia

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PSEUDOSTRATIFIED

COLUMNAR

One layer

Appears stratified-but not.

Respiratory tract

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the nuclei appear to lie in various layers, all cell are attached

to basal lamina some do not reach the surface

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Cells attach via cell adhesion molecules

(CAM)

Cells attach at specialized cell junctions :

Tight junctions/zonula occludens

zonula adherens

Desmosomes

Gap junctions

List one function for each type of cell junction.

Connections:

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Channels are formed by pairs of adjacent connexons, which are in turn composed of

six protein subunits that span the lipid bilayer of each cell membrane. The channel

measures about 1.5 nm in diameter, limiting the size of the molecules that can pass

through it. Nutrients and signal molecules may be transported between cells without

loss of material into the intercellular space, membranes are separated by a narrow

space or gap of about 2 nm.

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epithelium

transitionale

the superficial cells are rounded

and bulge into the lumen .

when the epithelium is

stretched, as when the bladder

is full of urine, the epithelium is

thinner than before , and the

superficial cells become

squamous