3 histology of major accessory organs (microanatomy 3)

Question 1

define endocrine and exocrine

Answer 1

endocrine: secretion is delivered from the bottom of the cell into capillaries
exocrine: secretary portions of columnar epithelial cells , from apical surface into duct system- local action eg. sweat gland

Question 2

what are acinar cells

how is autodigestion prevented?

Answer 2

clusters are secretory cells (columnar) surrounding duct cells (cuboidal)

• contain RER and zymogen granules
• produce digestive enzymes (pancreatic protease, amylase and lipase)

autodigestion prevented because secretions are packaged and inactive

Question 3

the role of duct cells in pancreas

Answer 3

secrete bicarbonate ions in relation to amount of HCl produced by stomach

produce water

Question 4

route of bile from liver

Answer 4

• secreted by hepatocytes
• into canaliculi
• combine to form bile ductules -> portal tact-> common hepatic duct

Question 5

gall bladder

Answer 5

• Muscular walled sac
• Epithelium is adapted for salt and water absorption
• Highly folded epithelia with microvilli
• Na+/k+ ATPase pumps out Na+ and CL- and the osmotic gradient draws water into the cells and then enters the capillary network (this is similar to the PCT of the kidney)

Question 6

cholestasis

Answer 6

results from reduced bile flow (eg. obstruction from stones)

or synthesis (hepatocyte damage)

bile accumulates in canaliculi, ruptures and damages hepatocytes and accumulates in blood -> jaundice

Question 7

surface projection of liver

Answer 7

right hypochondriac region, extends to epigastric into left hypochondrium

(largest gland in body)

Question 8

liver structure

Answer 8

lobule

hepatocytes

sinusoids

portal triad

Question 9

blood flow in liver

Answer 9

flows through sinusoid channel-> cental terminal venule-> sinusoid channel-> terminal branch of hepatic portal vein

Question 10

Zones of the liver:

which zone is exposed to toxins first?

which is most oxygenated?

if O2 removed, which die first?

Answer 10

1

1

3

Question 11

how can the liver be organised

Answer 11

lobule or acinus

classic lobule (6 sides)- structural

portal lobule

acinus (axis, functional)

Question 12

hepatocytes

Answer 12

form cords of cells separated by sinusoids. They have microvilli on their apical and basal surfaces (sinusoid facing) and bile canaliculi between adjacent hepatocytes.

Question 13

sinusoids

Answer 13

leaky capillaries

lined by endothelial cells and Kupfer cells

Question 14

Kupffer cells

Answer 14

phagocytoic cells - bacteria and old/ damaged blood cells

Question 15

Ito cells

Answer 15

stellate cells store vit A in lipid droplets in cytoplasm

myofibroblasts, participate in fibrosis and are APCs

Question 16

space of Disse

Answer 16

stellate cells wonder here, contain collagen fibres

Question 17

Cirrhosis

Answer 17

• Alcohol, absorbed from the stomach. The end product is acetaldehyde which is toxic to liver cells
• Slowly progressive: Leads to chronic liver failure
• Hepatocytes die, scarring results, relationship of hepatocytes to blood and bile systems damaged.
• Hepatocyte regeneration leads to nodules of cells with surrounding fibrous scar tissue.
• Hepatocytes can function but this is reduced and eventually demand outstrips supply-start of liver failure
• Liver failure ends in hepatic coma or complications of portal hypertension

Question 18

what happens to stellate cells during cirrhosis, what are the consequences are this

Answer 18

produce lots of collagen- difficult for hepatocytes to interact with blood

backing up of blood in portal system- higher pressure so varices form is oesophagus and anal canal

impact on brain due to blood build up

ascites

Question 19

portal hypertension

Answer 19

destruction of sinusoids so portal venous blood can’t escape. Increased blood pressure in the portal system. Escape route is via anastomoses with systemic venous system which open under high pressure and these anastomotic channels become distended to form varices.

•Those at the lower end of oesophagus bulge into the lumen and can be eroded by gastric acid-torrential haemorrhage (can be fatal)

Question 20

CF as a cause of malabsorption

Answer 20

(autosomal recessive). Mutation of the CFTR gene (cystic fibrosis transmembrane regulator) on chromosome 7 defective Cl- transport

• Disorder of epithelial transport affecting the secretion of exocrine glands
• Production of abnormally viscoid mucus
• Pancreas: clogs up ducts and glands – atrophy and fibrosis and malabsorption due to pancreatic insufficiency. Reduced protein and fat malabsorption and resulting deficiency of some fat soluble vitamins (A, D, K) and oedema.
• Liver: clogs bile canaliculi and leads to cirrhosis
• Reproductive tract affected also