Skeletalmuscle, heartmuscle, and wallsofholloworgans
nervous tissue
carries electrical signals from onepart of the body to another
epithelial tissue
includes epithelia and glands
epithelia(singular)
Layers of cells covering internal or external surfaces
Glands
structures that produce fluid secretions
functions of epithelial tissue
provide physical protection; control permeability; provide sensation;produce specialized secretions
characteristics of epithelia
Polarity (apical and basal surfaces)
Cellularity (cell junctions)
Attachment (basement membrane)
Avascularity (avascular)
Regeneration
Specialization of epithelial cells
Move fluids over the epithelium (protection)
Move fluids through the epithelium (permeability)
Producesecretions (protection and messengers)
Polarity
apicalsurface
-microvilli increase absorption or secretion
- cilia on a ciliatedepithelium move fluids
Basolateral surface
Integrity of epithelia is maintained by
1. Intercellularconnections
2. Attachment to the basementmembrane
3. Epithelialmaintenance and repair
intercellular connections
support and communication
celladhesionmolecules (CAMs)
transmembraneproteins
what act as intercellular cement?
Proteoglycans
cell junctions
form bonds with other cells or extracellular material
1.) Gap junctions
2.)Tight junctions
3.)Desosomes
gap junctions
-Allow rapid communication
-Cells held together by interlocking transmembrane proteins
- Allow small molecules and ions to pass
Desosomes
CAMs and proteoglycans link opposing plasma membranes
spot desmosomes
tie cells together; allow bend and twist
Hemidesmosomes
attach cells to the basement membrane
tight junctions
Between two plasma membranes; Adhesion belts attaches to terminal web; Prevent passage of water and solutes; Keep enzymes,acids, and wastes in the lumen of the digestive tract; Attachment to the basement membrane
basal lamina
closest to the epithelium
reticular lamina
deeper portion of the basement membrane, provides strength
Epithelial Maintenance and Repair
Epithelial cells are replaced by continual division of stem cells; located near basement membrane
based on shape
Squamous epithelia — thin and flat
Cuboidal epithelia — square shaped
Columnar epithelia — tall, slender rectangles
Based on layers
Simple epithelium — single layer of cells
Stratified epithelium — several layers of cells
Squamous epithelia
-simple squamous epithelia
a.) Absorption and diffusion
-Stratified squamous epithelia
a.) Protect against mechanical stresses
Cuboidal epithelia
-Simple cuboidal epithelia
a.) Secretion and absorption
b.) Glands and portions of kidney tubules
- Stratified cuboidal epithelia
a.) Relatively rare
b.) Ducts of sweat glands and mammary glands
Transitional epithelia
Tolerate repeated cycles of stretching without damage;
Appearance changes as stretching occurs;
Found in urinary bladder
Columnar epithelia
-Simple columnar epithelia
a.) Absorption and secretion
b.) Found in stomach, small intestine, large intestine
Pseudostratified columnar epithelia
Typically have cilia;
Found in nasal cavity, trachea, bronchi
Stratified columnar epithelia
Relatively rare;
Provide protection in pharynx, anus, urethra
Glandular epithelia
Glands are collections of epithelial cells that produce secretions
endocrine glands
release hormones into the bloodstream
exocrine glands
produce exocrine secretions; discharge secretions through ducts onto epithelial surfaces