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Biochemistry > The Pancreas, Liver, and Gallbladder > Flashcards

The Pancreas, Liver, and Gallbladder Flashcards

1
Q

name 3 gastrointestinal digestive organs. of those, which are endocrine organs?

A
  • pancreas (endocrine)
  • liver (endocrine)
  • gallbladder
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2
Q

what general functions do gastrointestinal digestive organs do?

A

regulate digestion and maintain metabolic homeostasis

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3
Q

what are characteristics of exocrine glands?

A
  • secretion onto a surface
  • made up of epithelial cells
  • diverse secretion types
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4
Q

what are characteristics of endocrine glands?

A
  • secretion into the vasculature
  • made up of epithelial and non-epithelial cells
  • exocytosis
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5
Q

describe the basic structure of exocrine glands

A
  • acinus (secretory portion) containing secretory vesicles
  • duct (conducting portion)
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6
Q

what are 3 types of exocrine glands?

A
  • merocrine glands
  • holocrine glands
  • apocrine glands
  • remember, it is the cells themselves within the glands that are producing the secretions
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7
Q

describe merocrine glands

A
  • most common exocrine gland that releases products via exocytosis at the apical end of secretory cells
  • ex. salivary glands, pancreas
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8
Q

describe holocrine glands

A
  • secretory cells disintegrate to form secretion
  • ex. sebaceous glands
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9
Q

describe apocrine glands

A
  • secretion of membrane-enclosed apical cytoplasm containing proteins and lipids
  • ex. mammary glands (also merocrine in function)
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10
Q

T or F:

the pancreas has endocrine and exocrine functions

A

true

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11
Q

describe the cells and the products they release of the endocrine and exocrine functions of the pancreas

A
  • endocrine: islets of langerhans, protein and polypeptide hormones
  • exocrine: acinar cells, releases digestive molecules into the duodenum
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12
Q

what is the function of acinar cells?

A
  • exocrine function in the pancreas
  • they exocytose zymogen granules into intercalated ducts
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13
Q

name 4 zymogen granules

A
  • alpha-amylase
  • lipases
  • nucleases
  • proteases
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14
Q

what is the function of alpha-amylase?

A

hydrolyze long-chain carbohydrates

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15
Q

what is the function of lipases?

A

hydrolyze lipids

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16
Q

what is the function of nucleases?

A

hydrolyze DNA and RNA

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17
Q

what is the function of protease? what is the cascade responsible for the functional process?

A
  • proteases are zymogens
  • they are inactive until they reach the duodenum
  • they hydrolyze proteins
  1. trypsinogen enters the duodenum; activated by enterokinase (turns trypsinogen into trypsin)
  2. activated trypsin cleaves chymotrypsinogen into chymotrypsin
  3. activeated trypsin activates elastase
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18
Q

T or F:

zymogens are activated in the liver to protect acinar cells

A

false:

they are activated in the duodenum to protect acinar cells

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19
Q

what are contracinar cells?

A
  • produce HCO3 to create an alkaline solution that flushes secretions into the duodenum
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20
Q

what 2 molecules induce acinar and contracinar exocrine activity?

A
  • cholecystokinin (CCK) - neuropeptide of the central and enteric nervous system; I cells
  • secretin - S cells
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21
Q

islets of langerhans include which 4 major cell types?

A
  • alpha cells
  • beta cells
  • delta cells
  • PP cells
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22
Q

what is the function of alpha cells?

A
  • islets of langerhans cell type
  • secrete glucagon
  • 30% of islet cells
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23
Q

what is the function of beta cells?

A
  • islets of langerhans cell type
  • secrete insulin
  • 65% of islet cells
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24
Q

what is the function of delta cells?

A
  • islet of langerhans cell type
  • secrete somatostatin - inhibit GI and pancreatic endocrine and exocrine secretion
  • 4% of islet cells
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25
Q

what is the function of PP cells?

A
  • islets of langerhans cell type
  • secrete pancreatic polypeptide - inhibits exocrine secretion, reduce GI motility, inhibit gastric acid secretion
  • <1% of islet cells
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26
Q

what are 4 main functions of the liver?

A
  • blood reservoir
  • bile secretion
  • detoxification
  • metabolic homeostasis
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27
Q

how does the liver function in metabolic homeostasis?

A
  • carbohydrate metabolism
  • lipid metabolism
  • protein metabolism
  • storage
  • serum protein production
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28
Q

the liver has vasculature coming from how many different places?

A
  • 2 (dual blood supply)
  • hepatic artery and portal vein
  • receives 30% of cardiac output
  • this is important in the liver’s detoxification function
29
Q

T or F:

the liver is the largest organ in the body

A

true

30
Q

T or F:

the liver cannot regenerate

A

false:

the liver is highly regenerative

31
Q

what are 3 major cell types of the liver?

A
  • hepatocyte
  • kupffer cell
  • sinusoidal epithelial cell
32
Q

what are hepatocytes?

A
  • polarized epithelial cells
  • metabolism of carbohydrates, proteins, and lipids
  • produces bile from cholesterol
  • detoxifies endogenous and xenobiotic molecules
33
Q

what are kupffer cells?

A
  • liver-specific macrophage
  • removes pathogens and debris from the blood
  • help prevent infection
34
Q

what is the Couinaud system?

A
  • it divides the lobes of the liver into lobules
  • lobules are 3mm wide and 7mm long
35
Q

what are sinusoidal epithelial cells?

A
  • line sinusoids in liver
  • large pores between cells (fenestrae)
  • no basement membrane
  • allows the liver to take on excess blood
36
Q

describe blood flow through the liver

A
  • blood flows into liver via portal vein and hepatic artery
  • blood diffuses through hepatic sinusoids
  • contacts hepatocytes, kupffer cells, and sinusoidal cells
  • filtered through into bile duct or blood leaves via the central vein
37
Q

the hepatic artery and portal vein supply the liver. what percent of the blood supply of the liver is coming from each source?

A
  • 70% from portal vein
  • 30% from hepatic artery
38
Q

blood from the portal vein enters the liver, but it first drains blood from which 5 organs?

A
  1. stomach
  2. spleen
  3. pancreas
  4. small intestine
  5. colon
39
Q

describe the blood flow and resistance of the liver

A
  • high blood flow
  • low resistance
40
Q

which blood vessel allows first-pass metabolism?

A
  • portal vein
  • this allows the liver to conduct rapid assessment of dietary products
41
Q

kupffer cells filter the blood. blood from which 2 organs does it primarily filter?

A

clears colon and intestinal bacteria

42
Q

T or F:

the liver provides rapid assessment of dietary products

A

true

43
Q

is the liver a blood buffer and reservoir?

A
  • yes
  • normal volume: 450mL
  • expansion: 0.5-1L
44
Q

what are the 3 structure-function liver architecture classifications?

A
  • classic hepatic lobule
  • portal lobule
  • hepatic acinus
45
Q

describe the classic hepatic lobule structure-function liver architecture classification

A
  • hexagonal prism of portal canals
  • blood drains from the portal vein and hepatic artery to the central vein
  • endocrine focus - when endocrine products are released from the liver, they are released into the central vein
46
Q

describe the portal lobule structure-function liver architecture classification

A
  • bile drains from hepatocytes to the bile ducts
  • exocrine focus - production and drainage of bile
47
Q

describe the hepatic acinus structure-function liver architecture classification

A
  • microvascular liver unit divided into circulatory zones
  • gradient of hepatocyte oxygenation
  • hepatic functions differ across zones
48
Q

what are the 3 hepatic acinus zones?

A
  1. zone I - periportal zone; oxygen and nutrient rich; most active in regulating blood sugar and protein metabolism
  2. zone II - intermediate zone
  3. zone III - peripheral zone; oxygen poor; high concentration of detoxifying enzymes
49
Q

the liver maintains systemic metabolic homeostasis in which 5 major ways?

A
  • carbohydrate metabolism
  • fatty acid metabolism
  • protein metabolism
  • storage
  • protein production
50
Q

describe how the liver maintains metabolic homeostasis via carbohydrate metabolism

A
  • glycogen storage
  • gluconeogenesis
  • normalizes blood glucose
51
Q

describe how the liver maintains metabolic homeostasis via fatty acid metabolism

A
  • oxidizes fatty acids
  • produces ketone bodies
  • synthesizes fatty acids
  • synthesizes triglycerides, phospholipids, and cholesterol
  • forms lipoproteins to transport lipids and fatty acids
52
Q

describe how the liver maintains metabolic homeostasis via protein metabolism

A
  • deaminates amino acids
  • forms urea to remove ammonia from the blood
  • synthesizes non-essential amino acids
53
Q

describe how the liver maintains metabolic homeostasis via storage

A
  • vitamins
  • fatty acids
  • iron
54
Q

describe how the liver maintains metabolic homeostasis via protein production

A
  • acute phase proteins
  • clotting factors
  • albumin
  • apolipoproteins
55
Q

the liver detoxifies endogenous and exogenous molecules. describe phase I and II of hepatocyte xenobiotic (drug)/molecule elimination

A

phase I:

  • drugs/molecules converted to more polar compounds; oxidized
  • cytochrome p450 and microsomal oxidases

phase II:

  • drugs/molecules/phase I metabolites conjugated to hydrophilic molecules
  • transferases

some drugs/molecules are directly transported into the bile
metabolites are eliminated in the bile or urine

56
Q

what is bile?

A

a heterogenous liver secretion containing bile salts, cholesterol, phospholipids, bilirubins, and waste

57
Q

bile salts are the products of what?

A

cholesterol metabolism

58
Q

what cell produces bile?

A

hepatocytes

59
Q

T or F:

bile is a mixed micelle solution

A

true

60
Q

T or F:

bile acidifies intestinal contents

A

false:

it alkalanizes it

61
Q

what is the function of bile acting as a detergent?

A

it solubilizes dietary lipids and fatty acids

62
Q

bile from the liver eliminates toxic _____ waste and _____

A
  • endogenous
  • xenobiotics
63
Q

describe the path bile takes from the gallbladder to the duodenum

A
  1. gallbladder
  2. cystic duct
  3. common bile duct
  4. merges with main pancreatic duct
  5. major duodenal papilla
  6. duodenum
64
Q

what is the function of CCK relative to bile?

A
  • stimulates bile release
  • contracts gallbladder smooth muscle
  • relaxes hepatopancreatic sphincter
65
Q

what is the function of secretin relative to bile?

A
  • it stimulates HCO3 secretion into the bile
  • serves to neutralize the acids from the stomach
66
Q

what is a zymogen?

A
  • an inactive enzyme precursor
  • activated in the duodenum
  • activated form serves to protect acinar cells
67
Q

in the hepatic acinus model, which zone contains hepatocytes that are most susceptible to damage during hypoxia or toxic conditions?

A
  • zone III
  • this region is oxygen poor and rich in detoxifying enzymes, and therefore regeneration and repair of hepatocytes here is inefficient
68
Q

describe how bile is recycled

A
  • via the enterohepatic pathway
  • bile is released from the gallbladder into the duodenum
  • reuptake of bile salts into the liver
  • production of bile in the liver
  • bile stored in the gallbladder
69
Q

list the following in order of decreasing % in bile:

chenodeoxycholic acid

lithocholic acid

deoxycholic acid

cholic acid

A
  • cholic acid - 50%
  • chenodeoxycholic acid - 30%
  • deoxycholic acid - 15%
  • lithocholic acid - 5%

Biochemistry (32 decks)

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