Digestive glands

Question 1

Origin of digestive glands

Answer 1

Endoderm -> Gut tube epithelium

Question 2

Three salivary glands + characteristics

Answer 2

Parotid - purely serous
Submandibular - mostly serous, some mucous
Sublingual - mostly mucous, some serous

• Serous cells in demilune when both are present (mucous takes over middle of the acinus)

Question 3

Overall histology of salivary gland

Answer 3

Acini with secretory cells and contractile myoepithelial
Intralobar ducts - intercalated (simple squam or cub) -> striated (simple column)
Interlobar ducts (pseudostratified->strat column)

Question 4

Striated ducts

Answer 4

Larger intralobar
Simple columnar
Infolding of basement membrane with lots of mitochondria (-> pink striations)
Ion transport, secretes lysozyme, transports IgA from plasma cells

Question 5

Functions and content of saliva

Answer 5

Lubrication - water and glycoproteins (mucous)
Digestive - alpha-amylase -> carbohydrates
Immune - IgA, lysozyme
Protective - pellicles -> protein film

Approoox 1500 cc/d

Question 6

Functions/secretions of pancreas

Answer 6

All serous
Digestive enzymes - amylase, lipase, trypsinogen, ribonuclease
- controlled by cholecystokinin
Ions - mostly bicarb - buffers gastric acid and allows activation of enzymes
- controlled by secretin

Question 7

Histology of pancreas

Answer 7

All serous
No striated ducts, intercalated less obvious
No myoepithelial cells
Centroacinar cells - ducts inside lumen - release bicarb

Question 8

Functions of liver

Answer 8

Protein synthesis - clotting factors, albumin
Bile metabolism - bilirubin, phospholipids, cholesterol
Detox/inactivation - oxidation, methylation, conjugation
Storage - lipids -> triglycerids, carbs -> glycogen
Gluconeogenesis

Question 9

Classic liver lobule histology

Answer 9

Portal triad peripheral - hepatic artery, portal vein, bile duct
Blood flows through sinusoids -> central vein in middle
Hepatocytes line sinusoids, send bile -> canaliculi -> terminal ductule -> bile duct in triad

Question 10

Hepatic sinusoids

Answer 10

Carry mixed blood from hepatic artery and portal vein
Large, discontinuous capillaries (incomplete basement, large fenestrations) to facilitate transport
Thin perisinusoidal space (of Disse) between basement and hepatocytes (many microvilli)
Flows from triad to central vein

Question 11

Portal triad

Answer 11

Bile duct branch - identify via simple cuboidal epithelium!
Hepatic artery
Portal vein (blood mixes into sinusoids)

Question 12

Kuppfer cells

Answer 12

Local macrophages in liver

Localized to internal endothelium of sinusoids

Question 13

Ito cells

Answer 13

Vitamin A storage
Local immunity

Localized to perisinusoidal space (of Disse)

Question 14

Hepatocyte organization

Answer 14

Organized into plates along sinusoids
Microvilli along basal surface (in perisinusoidal space) - both absorption and secretion
Lateral domain - tight junctions with neighboring hepatocytes
Bile exocytosis through small apical surface into bile canaliculi (sealed by tight junctions)

Usually have multiple domains - labelled for what they are bordering!

Question 15

Bile flow

Answer 15

Opposite of blood flow!
Bile canaliculi (between hepatocytes) ->
terminal duct (choleagiole, canals of Hering) ->
bile duct branch in triad

Question 16

Functions of gallbladder

Answer 16

Storage of bile

Concentration of bile - epithelium pumps Na and Cl to intercellular space -> osmotic gradient -> water leaves lumen

Question 17

Histology of gall bladder

Answer 17

Simple columnar epithelium in folds, not villi
- microvilli on apical surface, plicae/folds on lateral surface for ion pumping
Lamina propria, no muscularis mucosa!, disorganized muscularis externa
Visceral pleura on outer surface, adventitia where attached to liver