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13. Gastrointestinal > 6. The Liver, Biliary Tree, and Pancreas > Flashcards

6. The Liver, Biliary Tree, and Pancreas Flashcards

1
Q

What is the chyme like that enters the duodenum?

A

Acidic, hypertonic, and partly digested.

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2
Q

How is the acidic nature of chyme corrected for in the duodenum?

A

HCO3- secreted from pancreas, liver, and duodenal mucosa - prduced during the production of gastric acid.

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3
Q

How is the hypertonic nature of chyme corrected for in the duodenum?

A

By the osmotic movement of water into the duodenum across its wall.

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4
Q

How is the partly digested nature of chyme corrected for in the duodenum?

A

Digestion completed by enzymes from the pancreas and duodenal mucosa, with bile acids from the liver.

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5
Q

What are the two components of bile?

A

Bile acid dependent and bile acid independent.

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6
Q

What secretes the bile acid dependent component of bile?

A

Cells lining the canaliculi.

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7
Q

How do bile salts travel?

A

Conjugated to amino acids, and travel as micelles.

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8
Q

What is the role of bile acids/salts?

A

Major role in digestion and absorption of fat.

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9
Q

What are the parts of the bile acid dependent component of bile?

A

Bile acids/salts, cholesterol, and bile pigments.

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10
Q

What is the major bile pigment?

A

Bilirubin.

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11
Q

What secretes the bile acid independent component of bile?

A

Cells lining the intra-hepatic bile ducts.

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12
Q

What does the bile acid independent component of bile consist of?

A

Alkaline juive, HCO3-, like that from pancreatic duct cells.

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13
Q

What is the basic functional unit of the liver?

A

A lobule surrounding a central vein, which drains blood from the liver to the systemic veins. Blood from the hepatic portal vein and hepatic arteries enter at the periphery of the lobule through sinusoids lined by hepatocytes to the central vein.

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14
Q

What does the duodenum secrete in response to gastric emptying?

A

Cholecystokinin.

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15
Q

What does cholecytokinin do?

A

It stimulates the contraction of the gall bladder, ejecting concentrated bile acids together with enzymes from the pancreas.

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16
Q

What are bile acids released through?

A

The ampulla of vater.

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17
Q

What is the path of bile acids?

A

Released through the ampula of vater, continue to the terminal ileum, actively absorbed by the epithelium.

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18
Q

How are bile acids recycled?

A

Venous return from gut enters hepatic portal blood, hepatocytes actively take up bile acids and re-secrete them into canaliculi.

19
Q

Why are some bile acids not recovered?

A

they are unconjugated by gut bacteria and lost.

20
Q

How are lost bile acids replaced?

A

By hepatocytes replacing them.

21
Q

Where are bile acids stored?

A

In the gallbladder.

22
Q

How is the volume of bile acid stored in the gallbladder reduced?

A

The bile acids are concentrated by the transport of salt and water across the gall bladder epithelium.

23
Q

What is the risk of concentrating bile acids in the gallbladder?

A

Precipitation, leading to gall stones.

24
Q

When do asymptomatic gallstones become symptomatic?

A

When they move into the neck of the gall bladder of biliary tree.

25
Q

What are the symptoms of gallstones in the neck of the gall bladder or biliary tree?

A

Biliary colic or obstruction followed by inflammation and sometimes infection.

26
Q

What is cholecystitis?

A

Inflammation of the gallbladder from gall stones in the neck of the gallbladder or in the biliary tree.

27
Q

Why is biliary colic pain worse after eating?

A

The secretion of cholecystokinin will cause the gall bladder to contract.

28
Q

What are the exocrine secretion of the pancreas?

A

Alkaline juice (HCO3-), and enzymes - proteases (trypsin, chymotrypsin, elastase, carboxypeptidase), amylases, and lipases.

29
Q

What are the partsof the exocrine pancreas?

A

Acini and ducts.

30
Q

What is the acini of the exocrine pancreas?

A

Secrete inactive precursors of enzymes, package into condensing vacuoles -> zymogen granules that are secreted by exocytosis.

31
Q

What do the ducts of the exocrine pancreas do?

A

Secrete alkaline juice (HCO3-).

32
Q

How is alkaline juice secreted?

A

Na-K-ATPase sets up the Na+ concentration gradient, H+ exported into ECF using gradient. H+ combines with HCO3- -> H2O and CO2 - taken up into cell. Reform H+ and HCO3- inside the cell. HCO3- exported into the duct lumen and H+ is recycled.

33
Q

What stimulates alkaline juice secretion by the pancreatic ducts?

A

Secretin.

34
Q

What causes secretin release?

A

Low pH causes jejunal cells to release it.

35
Q

How are the acinar secretions of the pancreas controlled?

A

Stimulated by cholecystokinin (released from duodenal APUD cells in response to hypertonicity and fats).

36
Q

How are duct secretions of the pancreas controlled?

A

Stimulated from secretin (released from jejunal cells in response to low pH).

37
Q

Why is effective action of digestive enzymes against fats hard?

A

Fats are insoluble in water, so tend to aggregate into larger globules, so enzymes aren’t as effective.

38
Q

How do bile acids help fat digestion in the duodenum?

A

The bile acids enable fats to be incorporated into small micelles, with fats in the middle and polar components of bile acids on the outside. The micelles have a high surface area for lipase action and carry the products into the unstirred layer next to the mucosa to diffuse into epithelial cells.

39
Q

What happens to micelles of fat in the epithelial cells?

A

Reconstituted into triacylglycerols and re-expelled as chylomicrons - small particles made of lipid covered in phospholipids which facilitate transport of fat in lymphatic system from gut to systemic veins.

40
Q

What causes steatorrhoea?

A

If bile acids or pancreatic enzymes are not secreted in adequate amounts.

41
Q

What is steatorrhoea?

A

Fat in the faeces. This makes them pale, float, and smell foul.

42
Q

What causes jaundice?

A

The bile pigment bilirubin is made from haemoglobin breakdown. It is normally conjugated in the liver and secreted in the bile to be excreted. If it can’t be excreted, it accumulates in the blood - jaundice.

43
Q

What is jaundice?

A

An accumulation of bilirubin in the blood.

13. Gastrointestinal (17 decks)

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