7. Epithelial Tissue

Epithelial tissue

-lines the surface of the body and cavities

-responsible for the formation of glands

-Faces Lumen without cells´

Epithelial tissue Functions

-Secretion, Protection and Absorption

-sensory

What is always below epithelial tissue

Connective Tissue

Basement membrane

specialized basal surface that separates it from the underlying connective tissue

Basal Membrane components

basal laminate + reticular lamina

Apical Surface and functions

Surface of Epithelium, secretion, absorption and movement of contents.

Cilia

-hairlike extensions of the apical plasma membrane

-contains atonement → motility

-respiratory tract and female reproductive system

Microvilli:

-fingerlike cytoplasmic projections

-apical surface of most columnae epithelial cells

-increase absorption

-not motile

Stereocilia

-unusually long, immobile microvilli

-inner ear and male reprdoctive part

Lateral surfaces

in contact with neighboring cells.

Tight junction

-near apical surface

-seal off intercellular space

-keep cell polarity

-keep epithelial cells tightly attached

Adherens junctions - belt desmosome

-anchoring points for cytoskeleton

-Provide mechanical attachment via actin filaments - stabilize

-single continuous layer

Desmosomes

-Strong spot-like adhesions; connect intermediate filaments.

-two dense attachment plaques

-transmembrane glycoprotein

Communicating junctions

-Allow communication and ion exchange between cells.

Basal surface

attached to the basement membrane

Hemidesmosome

-adhering junction of basal plasma to basement membrane

-attach of epithelial cells to basement membrane

Classification by Embryonic Origin: Ectoderm

Skin and glands

Classification by Embryonic Origin: Mesoderm

Endothelium and Mesodelium

Classification by Embryonic Origin: Endoderm

Gastrointestinal coatingand respiratory coating

Coating epithelium

Continuous sheet, one or several layers, covering body surfaces.

Glandular epithelium

participates in the secretion of molecules, forming structures called glands.

Simple

-single layer of cells

-Little protection

-cilia and micrvolli

Simple cuboid

-single layer of cells

-squares with visible nucleus

Simple flattened

-single layer

-flattened cells

Simple columnar / cylindrical

-single layer

-column = säulen

Stratified

-two or more layers

-protective function

-basal cells cuboidal

Stratified squamous non keratinized

-most common

Stratified flattened or squamous non keratinized

Stratified keratinized squamous

-additional protective keratin layer

stratified cuboid

-two or three layers Of cuboidal cells

-robust lining

-.rare

Stratified Columnar or cilyndrical

-cells are columnar

Pseudostratified

-cells rest at Basal membrane

-nuclei near basal membrane

-goblet

Cilia + many layers of cell

Pseudodostratified

Respiratory truck epithelium

Pseudostratified

Keratin on surface + dark line

99% Skin

Stratified Transitional

-polygonal cells

-wave