Liver

Question 1

Basic functions

Answer 1

1. take up digested nutrients
2. store and release glucose, TGs, and vitamins
3. synthesize albumin, prothrombin & fibrinogen, a & B globulins, glucose, FAs and TGs, cholesterol and PPlipids, lipoproteins
4. Takes up and destroys/detoxifies metabolites, drugs, xenobiotics, bacteria, IG complexes, worn out cells and ptns
5. bile formation and secretion
6. sequesters IgA
7. converts T4 to T3
8. embryonic hematopoiesis

Question 2

Hepatocytes

Answer 2

epithelial cells that form parenchyma of liver
polyhedral
arranged in cords or plates
Central nucleus, may be polyploid or binuleate
central prominent nucleolus
contain large quantities of glycogen/lipids
short microvilli on free surface going into perisinusoidal space
have tight junctions, gap junctions, and desmosomes in lateral surfaces
Capable of all basic liver functions
Activity depends on position of cell in lobule and state of the animal

Question 3

Kupffer cells - structure

Answer 3

line liver sinusoids along with endothelial cells
stellate shaped
have Fc and C’ receptors on their surface
have receptors for ASGP-R, MP-R, and LDL-R
stain intense indigo

Question 4

Kupffer cells - function

Answer 4

fixed macrophage of sinusoids

1. phagocytize immune complexes, opsinized bacteria, fibronectin opsinized particulates
2. binds Hgb and breaks it down to bilirubin to go to hepatocyte for further processing
3. Degrade RBCs (recognition involves glycoptn or -SH changes on RBC surface)
4. antigen processing and presentation

Question 5

Fat-storing cell (Ito cell)

Answer 5

Has characteristic lipid droplets

Vitamin A is rapidly taken up and stored in the lipid droplets

Question 6

Endothelial cells

Answer 6

Finestrated
without diaphragms
no pericytes
basal lamina indistinct
type IV collagen and laminin detectable

Question 7

Liver parenchyma

Answer 7

Hepatocytes
Sinusoids
Sinusoidal cells

Question 8

General liver structure

Answer 8

Covered by visceral peritoneum = thin capsule/serosa that may contain smooth ms.
Separated into lobes (visible grossly)
Lobes separated into lobules = hexagonal in cross section; 1-2mm in diameter; only grossly visible in the pig

Question 9

Lobule organization

Answer 9

Hexagonal in shape
Centered around central v.
Triads (portal areas/canals) are at 3 or more hexagon vertices
Triads contain each a hepatic a. portal v., and bile duct (& lymphatics)
Plates/cords of hepatocytes radiate from central v. to form internal structre
sinusoids = small bl. vssls; located b/t hepatocyte plates & drain into central v.
Sinusoilds are lined by endothelial cells and Kupffer cells
Bile canaliculi = areas of expanded EC space; run from near central v. to peripheral bile ductules and drain into interlobular bile ducts; wall is formed by hepatocyte plasma membrane

Question 10

Classic lobule

Answer 10

polygonal in shape
portal canals are in periphery of lobule and v. is in center
emphasizes endocrine function

Question 11

Portal lobule

Answer 11

Triangular shape
Portal triad is at center
Central v. is at peripheral apexes
Emphasizes exocrine function of liver

Question 12

Liver acinus (Rappaport’s lobule)

Answer 12

Oval
Terminal branches or portal triad along central axis
blood flow from central axis to two central vv located at the periphery of the lobule
describes peripheral to central gradient of metabolism thru zonation
zone 1: receive blood w/highest concentration of nutrients (last to die, 1st to regenerate)
zone 2: receives blood of intermediate quality
zone 3: receives blood w/the lowest nutrient content (1st to die)