Tissues: Epithelium Flashcards
epithelial tissue basic functions
covers body surfaces and lines hollow organs, body cavities, ducts; and forms glands
connective tissue
protects, supports, and binds organs
-stores energy as fat and provides immunity
muscular tissue
generates the physical forces needed to make body structures move and generate body heat
nervous tissue
detect changes in body and responds by gnerating nerve impulses
3 tissue layers
ectoderm (nervous), endoderm, and mesoderm (connective and muscle)
-epithelial is all of them
tight junctions
web-like strands of transmembrane proteins
-in stomach, intestines, and urinary bladder
desmosomes
- contain plaque and cadherins that extend into the intercellular space to attach adjacent cells
- plaque is connected by intermediate filaments that have keratin
- good in heart and skin
hemidesmosomes
- look like half a desmosome
- anchor cells to basement membrane
- transmembrane glycoprotein: integrin
- integrin attaches to basement membrane’s intermediate filaments and protein, laminin
gap junctions
connect neighboring cells with connexons (made of connexin)
allow ions, nutrients, waste, chemical and electrical signals to pass from cell to cell
3 functions of epithelial tissue
- selective barrier
- secretory surfaces
- protective surfaces
surfaces of epithelial cells
- apical (free surface)
- lateral surface (faces adjacent cells)
- basal surface (opposite to apical)
Basement membrane (of epithelial tissues) structure
- thin double extracellular layer
- basal lamina = closer to and excreted by epithelial cells –> contains laminin, collagen, glycoproteins, and proteoglycans
- reticular layer = closer to and secreted by underlying connective tissue cells –> contains collagen
different epithelial cell shapes and their functions
squamous = good for filtration or rapid diffusion cuboidal = food for secretion/absorption columnar = special secretion/absorption transitional = bladder
Where to find simple squamous epithelium? (both endothelium and mesothelium)
endothelium = heart, blood vessels, and lymph vessels
mesothelium = serous membranes
both derived from mesoderm
where to find simple cuboidal epithelium?
thyroid glands and kidneys
where to find nonciliated simple columnar epithelium
- linings of digestive, respiratory, reproductive, and urinary tracts
- also stomach lining
- have microvili and goblet cells
where to find ciliated simple columnar epithelium
uterine tubes
where to find pseudostratified columnar epithelium
ciliated: trachea
stratified squamous spithelium
characteristics and where to find
- new cells pushed up to apical layer
- as cells move away from blood supply, they harden and die
- can be keratinized (superficial layer of skin)
- can be unkeratinized (mouth, esophagus, vigina)
stratified cuboidal epithelium
-pretty rare
for protection of esophageal glands
stratified columnar epithelium
- rare
- for protection and secretion in esophageal glands
transitional epithelium
only in urinary system
endocrine glands
- don’t have ducts
- secretions are hormones and theydiffuse into bloodstream
- their function is to maintain homeostasis
exocrine glands
- secrete products into ducts that empty onsurface of epithelium
- skin surface or luman of hollow organ
- secretions include mucus, sweat, oil, earwax, saliva, and digestive enzymes
Structural classification of exocrine glands
- Ducts - “simple” if unbranched, “compound” if branched
2. Shape - tubular, acinar (round), or tubuloacinar
Functional classification of exocrine glands
- Merocrine = protein is synthesized in cell and carried out with vesicle (exocytosis)
- Apocrine = secretions hang out at apical end of cell until that whole end is pinched off and secreted into duct
- Holocrine = cell explodes, dies, disintigrates, and the whole thing is secreted
