Epithelium

Question 1

Tissue Types

Answer 1

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

Question 2

Epithelium

Answer 2

shape of cells
basal lamina
lamina propria

Question 3

Shape of Cells

Answer 3

– 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

Question 4

Basal lamina

Answer 4

– 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

Question 5

Lamina propria

Answer 5

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

Question 6

Junctional Epidermolysis Bullosa

Answer 6

– 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

Question 7

Intracellular Junctions

Answer 7

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

Question 8

Pelizaeus-Merzbacher-like Disease

Answer 8

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

Question 9

Microvilli

Answer 9

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

Question 10

Sterocilia

Answer 10

long, non-motile, microvilli

Question 11

cilia

Answer 11

– 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

Question 12

Simple Epithelium

Answer 12

 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

Question 13

Stratified Epithelium

Answer 13

– 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

Question 14

Glandular Epithelium

Answer 14

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

Question 15

Renewal

Answer 15

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

Question 16

Ion Transport

Answer 16

o Active transport

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

Question 17

Serous and Mucous Cells

Answer 17

o Secretory granules – digestive enzymes

o Mucins – hydrophilic glycoproteins

Question 18

Diffuse Neuroendocrine System

Answer 18

APUD cells