Tissues (Part 1)
Epithelial Tissues
A sheet of cells (usually I layer) that covers a body surface/lines a body cavity. creates boundaries
Functions of epithelia:
• Protection (mechanical/chemical/infectious)
• absorption (GI tract)
• Filtration(kidney)
• Excretion(kidney)
• Secretion (glands, GI tract)
• sensory reception ( taste buds, olfactory membranes)
Structural Characteristics of Epithelia:
• .Polarized
◦apical (facing lumen) and basal (towards supporting tissue)
• Tight junctions and desmosomes
◦cell membranes are tightly bound to prevent fluid leakage; stapler at cell
membrane
• Basement membrane( connective tissue)
◦basal lamina( supportive sheet of glycoproteins) & reticular lamina( primary
collages fibres)
◦Strong physical support, attachment of epithelial cells and connective
tissue, cell movement
• Innervated and avascular(no blood capillaries)
• Nourished by diffusion
• Regenerate regularly via mitosis
producing secretions
solocated near
apicalsurfaces
allowsvesicles
tobringsecretions
intolumen
Cancerous epithelial cells fail to respect
boundary imposed by basement membrane
Epithelial Tissues
A sheet of cells (usually I layer) that covers a body surface/lines a body cavity. creates boundaries
Functions of epithelia:
• Protection (mechanical/chemical/infectious)
• absorption (GI tract)
• Filtration(kidney)
• Excretion(kidney)
• Secretion (glands, GI tract)
• sensory reception ( taste buds, olfactory membranes)
Structural Characteristics of Epithelia:
• .Polarized
◦apical (facing lumen) and basal (towards supporting tissue)
• Tight junctions and desmosomes
◦cell membranes are tightly bound to prevent fluid leakage; stapler at cell
membrane
• Basement membrane( connective tissue)
◦basal lamina( supportive sheet of glycoproteins) & reticular lamina( primary
collages fibres)
◦Strong physical support, attachment of epithelial cells and connective
tissue, cell movement
• Innervated and avascular(no blood capillaries)
• Nourished by diffusion
• Regenerate regularly via mitosis
producing secretions
solocated near
apicalsurfaces
allowsvesicles
tobringsecretions
intolumen
Cancerous epithelial cells fail to respect
boundary imposed by basement membrane
