Chapter 4 vocab Flashcards
Tissues
Collections of specialized cells and cell products that performs specific functions
Histology
Study of tissues
Functions of Epithelial Tissue
- Provide physical protection
- Control permeability
- Provide sensation
- Produce specialized secretions
Characteristics of epithelia
- Polarity
- Cellularity (cell junctions)
- Attachment (basement membrane)
- Avascularity (avascular)
- Regeneration
Specializations of epithelial cells
- Move fluids over the epithelium (protection)
- Move fluids through the epithelium (permeability)
- Produce secretions (protection and messaging)at
Integrity of epithelia maintained by
- intercellular connections
- attachment to basement membrane
- epithelial maintenance and repair
Apical surface
Microvilli increase surface area and absorption
Cell Adhesion Molecules (CAMs)
Transmembrane proteins that serve as support and communication (intercellular connections)
Cell junctions
Form bonds with other cells or extracellular material
- Gap junctions
- Tight junctions
- Desmosomes
Gap Junction functions
- Allow rapid communication
- Cells held together by interlocking transmembrane proteins (connexons)
- allows small molecules and ions to pass
- coordinate contractions in heart muscle
Tight junctions
- between two plasma membranes
- adhesion belt attaches to terminal web
- prevent passage of water and solutes
- keep enzymes, acids, and wastes in the lumen of the digestive tract
Desmosomes
- CAMs and proteoglycans link opposing plasma membranes
- attachment to basement membrane (basal lamina and reticular lamina)
Spot desmosomes
- tie cells together
- allow bending and twisting
Hemidesmosomes
attach cells to basement membrane
Classification of epithelia based on shape
- Squamous: thin and flat
- Cuboidal: square shaped
- Columnar: tall, slender rectangles
Classification of epithelia based on layers
- Simple epithelium: Single layer of cells
- Stratified epithelium: Several layers of cells
Simple squamous epithelium
Absorption and diffusion
Mesothellum
lines body cavities (simple squamous)
endothellum
forms inner lining of heart and blood vessels (simple squamous)
stratified squamous epithelia
- Protects against mechanical stresses
- Keratin adds strength and water resistance
simple cuboidal epithelia
- secretion and absorption
- glands and portion of kidney tubules
stratified cuboidal epithelia
- relatively rare
- 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
simple columnar epithelia
- absorption and secretion
- Found in stomach, small intestine, and large intestine
pseudostratified columnar epithelia
- typically have cilia
- found in nasal cavity, trachae, bronchii
stratified columnar epithelia
- relatively rare
- provide protection in pharynx, anus, urethra
Glands
Collections of epithelial cells that produce secretions
Endocrine glands
- release hormones that enter bloodstream
- no ducts
Exocrine glands
- produce exocrine secretions
- Discharge secretions through ducts onto epithelial surfaces
Gland structure
- unicellular glands
- multicellular glands
Goblet cells
- unicellular exocrine glands
- secrete mucin, mixes with water to form mucus
Multicellular exocrine glands classified by…
- Structure of duct
- Shape of secretory portion of gland
- Relationship between ducts and glandular areas
Methods of secretion
- Merocrine
- Apocrine
- Holocrine
Merocrine secretion
released by secretory vesicles (exocytosis)
Apocrine secretion
released by shedding cytoplasm
holocrine secretion
- released by cells bursting, killing gland cells
- Gland cells replaced by stem cells
