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Flashcards in Epithelium Deck (18):

Tissue Types

o Epithelium – strongly adherent cells with very little extracellular substance
o Connective tissue – abundance of extracellular matrix; less cells more “other” stuff
o Nerve – cells that receive, generate, and transmit nerve impulses
o Muscle – cells with specialized function of contraction



shape of cells
basal lamina
lamina propria


Shape of Cells

– how we name the cells
 Shape of nuclei
 Polarity of cell – what the business end is
• Apical – faces surface/lumen
• Basal – communicates with connective tissue deep


Basal lamina

– bottom basal end of epithelium; interacts with fibrous, microfilament reticular lamina
• Lamina lucida – area between membrane of basal cells and lamina densa
• Lamina densa – dense area between lamina lucida and lamina propria
o Made up of :
 Type IV collagen – basal lamina specific; only found in basal lamina; helps with the functions of basal lamina
 Laminin and type IV collagen networks held together by:
• Laminin and entactin (glycoproteins)
• Perlecan (proteoglycan)
 Type VII collagen – helps crosslink basal lamina to underlying tissue
 Support
 Barrier
 Proliferation
 Polarity
 Migration
 Metabolism


Lamina propria

– underlying connective tissue deep to epithelium and basement membrane
• Provide nutrition to epithelium
• Bind to neighboring structures


Junctional Epidermolysis Bullosa

– identify using staining for type IV collagen (basal lamina specific collagen)
o Clinical
 Blistering skin condition
 Alopecia – hair loss
 Nail loss or deformed nails
o Histopathology
 Anchoring filaments disrupted
 Hemidesmosome malformed
 No anchor to basement membrane of epithelium – resulting in separation and blistering


Intracellular Junctions

o Communication, adhesion, seal
o Types from apical to basal
 Tight junction (zonula occludens) – band
• Always apical because they are barrier junctions
 Zonula adherens – actin filaments form terminal web
• Always apical because they are barrier junctions
 Desmosome (macula adherens) – forms attachment plaque using cytokeratin (intermediate filament-epithelial junctions), desmin, vimentin, cadherins
• Can occur anywhere
• Hemidesmosome – desmosome that occurs at basal end connecting epithelium to basal lamina and reticular lamina/basement membrane
 Gap junctions – uses connexon protein; allow for communication between cells
• ATP, hormones, ions, etc. can pass through
• Can occur anywhere
• Connexon is made up of 6 connexin units
o Hydrophilic pore


Pelizaeus-Merzbacher-like Disease

o Clinical – rapid involuntary eye movements (nystagmus), ataxia and impaired motor development, difficult articulating
o Histopathology – mutations in a gap junction protein (connexin 46.6)
 Central and peripheral myelination is disrupted



o On almost all cells
o Increase surface area
o Glycocalyx – carbohydrates added onto microvilli; makes microvilli visible giving it a striated/brush border/appearance



long, non-motile, microvilli



– 9+2 microtubule arrangement under the plasma membrane that extend out on apical surface of epithelium
o Motile
o On apical surface of epithelium that need to clear area or keep things moving


Simple Epithelium

 Squamous – large nucleus; cobblestone appearance
• Endothelium – lines the blood vessels; very leaky
• Mesothelium – covers organs
 Cuboidal – nucleus is in center
• Surface of ovary
• Kidney
• Tubules in glands
 Columnar – nuclei towards basal surface; taller than they are wide; locations where you are absorbing or excreting
• Lining of intestine
• Lining of uterus


Stratified Epithelium

– name based on the most superficial layer of cells; mostly cuboidal cells will be at basal surface along basal lamina; germ cells will be located near basal lamina where they are continuously making new cells; located where there is a lot of abrasion and turnover of cells
 Squamous (cuboidal)
• Skin – keratinized – nonliving
o keeps skin from drying out and protect bad things from getting underneath
• Vagina – nonkeratinized – live surface cells
 Columnar/cuboidal – very rare
• In large duct
 Transitional – specialized; outermost layer are dome shaped cells; often binucleated cells
• Bladder
• Upper urethra
• ureter
o Pseudostratified – nuclei often occur at different levels but look closely and each cell attaches to basement membrane
 Respiratory tract – contains goblet cells and cilia


Glandular Epithelium

o Purpose – secrete proteins, lipids, and protein/carbohydrate complexes
o Exocrine – secreted into lumen that goes into duct and out into organ
 Starts as bud from epithelium; cell divison and migration deep as duct forms
• Retains connection to surface
 Merocrine – release their secretions via exocytosis without any loss of cellular components
• Myoepithelial cells – at the base of gland
o Has actin and myosin in it; hugs edge of glandular material and will contract in merocrine glands to excrete substance
 Holocrine – secrete by exploding the cell
• Sebaceous gland – secrete oil
 Apocrine – combination; loses the apex of the cell when secreting
 Exocrine Gland Structure
• Acinar – looks like grapes on stem
• Tubular
• Any combination of above
o Endocrine – secreted into bloodstream
 Loses connection to surface of epithelium
 Glandular surface will grow near blood vessel
o Unicellular - Goblet cell – secretes onto surface of epithelium



o Metaplasia
 Carcinoma – epithelial origin
 Adenocarcinoma – glandular epithelial origin


Ion Transport

o Active transport
o Transcellular transport (base to apex or apex to base)


Serous and Mucous Cells

o Secretory granules – digestive enzymes
o Mucins – hydrophilic glycoproteins


Diffuse Neuroendocrine System

APUD cells