HCB Objectives 18
1.
Liver functions: Bile synthesis/secretion, protein synthesis, glucose homeostasis,
drug/toxin metabolism
Endocrine gland specializations: enzyme synthesis (glucagon, insulin,
somatostatin, etc.)
Exocrine gland specializations: bile synthesis
Blood regulation specializations: plasma protein synthesis
2.
Anatomical relationships:
a.
Incoming vessels: hepatic artery (20%) and hepatic portal vein (80%)
b.
Outgoing vessels: central vein to sublobular hepatic vein
c.
Bile ducts: takes bile from bile canaliculi (between adjacent hepatocytes)
and empties them through short bile ductules (simple cuboidal) into the
bile duct.
d.
Sinusoids: takes incoming blood flow from portal tract (hepatic artery and
hepatic portal vein) through the liver parenchyma to the central vein
e.
Liver cells:
1. Hepatocytes: bile canaliculi flow between adjacent hepatocytes
2. Sinusoidal endothelial cells: highly fenestrated cells composing the
sinusoid endothelium
3. Stellate cells: fat storing cells which surround the external lumen to
absorb lipid droplets and fat soluble vitamins
4. Kupffer cells: macrophages which live in the lumen of sinusoids and
extend their processes through fenestrae
 Note: A portal tract is made up of a hepatic artery, portal vein,
bile duct, and lymphatic vessel. Hepatic arteries and portal veins
flow in the opposite direction of bile ducts and lymphatic vessels
3.
Classic liver lobe: hexagonal structure with central vein in the center and portal
tracts at the six vertices
Pericentral microenvironment: smaller sinusoidal fenestrae, less endothelial
surface area, better oxygenated, glucose uptake/release, urea formation, glutamine
formation
Periportal microenvironment: larger sinusoidal fenestrae, more endothelial
surface area, poorly oxygenated, glycolytic enzymes, glutaminogenic enzymes
Clinical significance of hepatic microenvironments: injuries prefer zones of
the classic lobule; centrilobular environment is injured by carbon tetrachloride
and acetaminophen, periportal environment is injured by allyl alcohol
4.
Classic lobule: hexagonal structure with central vein in the center and portal
tracts at the six vertices
Portal lobule: hexagonal structure with portal tract in the center and alternating
portal tracts and central veins as the vertices
Hepatic acinus: amorphous distinction to describe areas of
oxygenation/metabolic function; described by the closest area to the hepatic
venules as 1 (most oxygenated) radiating out to the center being 3 (least
oxygenated)
5.
Hepatocyte: polyhedral epithelial cells composing the parenchyma of the liver.
Relationships of apical, basal, lateral surfaces:
a.
Apical surface: face adjacent hepatocytes and enclose bile canaliculi
b.
Basal surface: face space of Disse/endothelial cells, microvilli extend
through fenestrae to increase blood-parenchymal exchange
c.
Lateral surface: cell-cell junctions (gap junctions for exchange and tight
junctions to seal blood supply from bile canaliculi
Molecules being secreted/absorbed at surfaces:
a.
Bile: Absorbed through basal surface through cholesterol and bilirubin;
secreted through apical surface into bile canaliculi
b.
Major plasma proteins: Secreted through basal surface into bloodstream
c.
Glucose, glycogen, drugs, toxins: Absorbed and secreted through basal
surface into/out of bloodstream
6.
Sinusoid cells:
a.
Sinusoidal endothelial cells: highly fenestrated cells composing the
sinusoid endothelium
b.
Stellate cells: fat storing cells which surround the external lumen to
absorb lipid droplets and fat soluble vitamins; synthesize collagen and are
important in fibrotic scarring of cirrhosis
c.
Kupffer cells: macrophages which live in the lumen of sinusoids and
extend their processes through fenestrae
 Note: the Space of Disse is the space between the basal membranes of
hepatocytes and endothelial cells; it is important for the exchange of
materials between hepatocytes and blood