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ANAT 261 > digestive system V and VI > Flashcards

digestive system V and VI Flashcards

1
Q

name liver functions

A

endocrine secretion
exocrine secretion
inactivation or elimination of substances
conversion of substances
hemopoiesis
storage of substancesd

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2
Q

describe endocrine secretion - liver functions

A

secreted into blood
somatomedin - GH, tells liver to produce this and tells cells of epiphyseal plate - chondrocytes to grow and multiply, albumin, fibrinogen, prothrombin, transferrin - iron carrier, vldl = very low density lipoprotein, precursor of ldl

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3
Q

describe exocrine secretion - liver functions

A

not to circulation
goes to bile, bile acids, billirubin, it also secretes, phospholipids and cholesterol

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4
Q

describe inactivation/secretion of substances - liver functions

A

glucuronyl transferase conjugates glucuronic acid to bilirubin - goes to bile, also to barbituates, antihistaminics, anticonvulsants, insecticides, and other drugs,
endocytosis of hormones and cholesterol - ldl particles- bad cholesterol
liver has ldl receptors - way to eliminate toxins from body hormones go to target organ to trigger a function, hormone cannot be circulating forever so its removed by receptor mediated endocytosis - live has receptors for hormone

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5
Q

describe conversion of substances - liver functions

A

tetra-iodothyronine (t4. thyroxine, thyroid hormone) –> tri-idodthyronine (t3 - more potent) converted by liver cells

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6
Q

describe hemopoiesis - liver functions

A

production of rbcs
during fetal development
after birth - bone marrow takes over

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7
Q

describe storage of substances - liver functions

A

glycogen - sugar and lipids - cholesterol, triglycerides

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8
Q

describe capsule of ct of liver

A

penetrates at level of porta hepatis
glissons
separates liver into hepatic lobules = prismatic structures

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9
Q

what is porta hepatis

A

entrance of 2 branches of hepatic arteries (start in abdominal aorta and then branches)
exit of hepatic duct = brings bile synthesized in liver to gallbladder

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10
Q

describe common bile duct

A

ends at level of si
bile will go to intestines
Emulsifies fat - digestion of lipids

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11
Q

describe hepatic vein

A

exits through hepatic vein and drains blood into inferior vena cava

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12
Q

describe histology of liver

A

ct between lobules = across and down
bile duct goes in opposite directions of hepatic artery and portal veins
located in portal space =
branch of hepatic artery = arteriole
branch of portal vein = venule
portal space = ct blood vessels and bile ducts, large areas of ct

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13
Q

describe hepatic lobule

A

subdivided by chords of hepatocytes

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14
Q

describe hepatocytes

A

pale colour, forms row of cells separated by blood vessels - liver sinusoids - go from periphery to central vein

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15
Q

describe veins of hepatocytes

A

sinusoids
central vein opens into sublobular vein
which drains in hepatic vein

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16
Q

what are bile canaliculi

A

opens into bile duct and takes bile to common bile duct and gallbladder
bile released when fatty meal

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17
Q

describe sinusoids

A

see endothelial cells
separates hepatocytes
NO BM
only reticular fibers, irregular in size
Permeable capillaries
separated = no tight junctions
everything goes through easy

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18
Q

describe kupffer cell

A

phagocytic cells - old rbcs, particulate matter, bacteria

bigger than edothelial cell
processes can extend to sinusoids - long

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19
Q

what opens into sinusoids

A

arteriole - branch of hepatic artery and venule - branch of hepatic vein

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20
Q

describe cholangiole and bile duct

A

equivalent to intercalated duct = between lobes, interlobular
cholangiole opens into bile duct
bile secreted by hepatocytes
bile duct covered by columnar or cuboidal cells - depends on size of bile duct

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21
Q

describe nuclei of hepatocytes

A

can be binucleated
small cubes forms plate = communication between plates = opening

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22
Q

what is at the end of bile canaliculi

A

tight junctions
changes directions where bile circulates, since do not want bile to be in circulation

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23
Q

what is space of disse

A

between endothelial cells and hepatocytes = space of disse
where exchange happens

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24
Q

what are cholangioles also called

A

herings canals
bile ductules

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25
Q

what are sinusoids lined by

A

endothelial cells and kupffer cells sometimes

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26
Q

name main activities of hepatocyte

A

endocytic and secretory activities

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27
Q

describe endocytic activity of hepatocyte

A

receptor mediated endocytosis of ligands = hormones, ldl, hdl, chylomicrons
digested and stored as aas
triglycerides, monosaccharides etc
Dissociation of ligand and then receptor will be recycled to cell surface to continue cycle - important, liver degrades these substances after since they should not be circulating

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28
Q

describe secretory activity of hepatocyte

A

rer = synthesizes apolipoproteins and sends to golgi - ser stores long chain fatty acids, triacylglycerols, phospholipids and cholesterol and sends to golgi
golgi = packs complex and secrets into space of disse and lumen vldl - apolipoprotein complex, contains cholesterol secreted by liver, produced by hepatocytes

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29
Q

why is removing ldl important

A

could lead to plaque in artery

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30
Q

what are other functions of hepatocytes

A

peroxisome
ser

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31
Q

describe peroxisome of hepatocyte

A

similar to lysozyme - has crystalline structure
catalyses reaction - turns hydrogen peroxide to water and oxygen
removes hydrogen peroxide
beta oxidation of long fatty acid chains - FA - by product = hydrogen peroxide
catabolism of alcohol
breakdown of purines amp/gmp to uric acid - eliminated by kidneys
cholesterol synthesis

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32
Q

describe SER of hepatocyte

A

synthesized bile cholesterol + taurine = taurocholic acid
bilirubin conjugated to glucuronic acid
will be elimated at level of bile canaliculi - do not want it to go to circulation

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33
Q

describe a portal lobule

A

surrounded by portal spaces
3 central veins all drain into the same portal space = makes portal lobule

34
Q

describe hepatic acinus

A

metabolic effects
hepatocytes closer to portal space = metabolically active since closer to oxygen
as go towards central vein = less oxygen and more elements from waste metabolism

35
Q

what do all bile ducts drain into

A

hepatic duct and all goes to gall bladder

36
Q

what is turnover of hepatocytes

A

150 days
very low
expanding - expanding population of cells

37
Q

what is mitotic index

A

1 cell every 20 000

38
Q

what is surgical excision

A

cells divide actively until organ reaches normal size

39
Q

describe repeated damage to hepatocytes

A

like alcoholism = results in proliferation of ct = cirrhosis - liver will not recover and be small

40
Q

what is hepatitis

A

tight junctions affected and bile leaks out = leads to jaundice

41
Q

describe pancreas

A

The pancreas is a mixed exocrine & endocrine gland

endocrine portion is composed of islets of langerhans
exocrine portion is a compound acinar gland similar in structure to parotid gland

42
Q

describe exocrine pancreas

A

exocrine pancreas produces a slightly alkaline fluid & proteins consisting 15 or more of main enzymes (mainly) & pro-enzymes (zymogens - Zymogenic granules) capable digesting the components of ingested food in small intestine
i.e. Carbohydrates (breakdown to mnosaccharides lipids (to triglycerides), proteins to amino acids) & nucleic acids (phosphate group Remove from nucleic acids by enzymes - like alkaline phosphatase)

43
Q

both pancreas and salivary glands derive from…

A

evaginations of endodermal lining of embryonic primitive intestine

44
Q

describe accessory pancreatic duct

A

drains secretory products into duodenum

45
Q

describe main pancreatic duct

A

join to common bile duct coming from gallbladder
Together = drain into duodenum

46
Q

what does bile promote

A

digestion of fat and pancreas provides lipids and other zymogens or enzymes

47
Q

describe exocrine and endocrine pancreas

A

endocrine = islets of langerhans
serous acini = exocrine

48
Q

describe formation of pancreas

A

blind ended tubules are lined by undifferentiated simple columnar epi cells which undergo sequential branching - many ducts
epithelial rudiments begin to organize into acini and lobules
some cells further differentiate from these forming acini = form islets of langerhans

49
Q

describe exocrine pancreas

A

Divided in lobes and lobules
compound acinar = similar to salivary glands

50
Q

describe ct of pancreas

A

capsule penetrates at level of pancreatic duct and separates liver into lobes and lobules

51
Q

describe interlobar duct and ct

A

large amounts of ct
large ducts

52
Q

describe interlobular duct and ct

A

thin septi of ct = subdivides lobe into small lobules

53
Q

describe intercalated duct

A

drain into small lobular duct - equivalent to intercalated duct of salivary glands
short cells, pale, sometimes cuboidal or squamous
connected to serous acini

54
Q

describe interlobular duct and ct of adult pancreas

A

line by columnar ep
cells pale
dont stain well

55
Q

describe serous acini

A

exocrine pancreas
pyramidal shaped cells, round nucleus, tends to be basophilic, apex = acidophilic due to zymogen secretory granules with enzymes - picks up eosin

56
Q

describe centroacinar cells

A

pale
center of serous acini

57
Q

describe islets of langerhans

A

surrounded by thin capsule of ct - fibrocytes, reticular fibers, diagnostic - use as landmark

58
Q

describe serous acinus cell

A

no myoepithelial cells in serous acini
secreting into lumen so tight junctions

59
Q

describe serous acinar cell

A

pyramidal
tight junctions
ribosomes - ribonucleoproteins, react well with hematoxylin so basophilic at base
rer - well devlopped and mitochondria - active cell
golgi prominent - packs enzymes into condensing granule
zymogen granules - has protein, dark in em, electron dense, fully mature
exocytosis

60
Q

describe pancreatitis

A

medical emergency
can happen after excess alcohol = enzymes start to dissolve own pancreas - leaks out, enzymes more powerful than stomach

61
Q

what regulates the exocrine pancreas

A

cck
secretin
Unconstituted, only when digestion

62
Q

describe cck

A

produced by enteroendocrine cells of duodenum
promotes exocytosis

63
Q

describe secretin

A

stimulates secretion of water and bicard
produced by enteroendocrine cells of duodenum

64
Q

what do centroacinar cells produce

A

water and bicarbonate

65
Q

describe zymogen granules

A

contain proenzymes
all converted by enterokinase
trypsinogen to trypsin (remove aa from trypsinogen and convert to active trypsin)
procarboxypeptidase to carboxypeptidase
proelastase to elastase
pro phospholipase a to phospholipase a

66
Q

describe enterokinase

A

located in microvilli of enterocytes of duodenum
small enzyme - protease

67
Q

describe active enzymes of pancreas

A

15 active enzymes
lipase - important of tj, role in pancreatitis
amylase
RNase
DNase

68
Q

what is role of trypsin inhibitor

A

Secreted by centroacinar cells
prevents early activation of trypsin
provides protection against reflux of trypsin from gut

69
Q

describe endocrine pancreas

A

Islets of langerhans
will organize in 2 ways = follicles like in thyroid or cords associated to fenestrated capillaries
pancreatic cells of islets of langerhans associated to fenestrated capillaries

70
Q

how many islets of langerhans in pancreas

A

5x10^5-10^6 = 2% of pancreas
200um in diameter
considered to be endocrine microunits

71
Q

name cell types

A

alpha
beta
delta
pancreatic polypeptide cells

72
Q

describe alpha cells of endocrine pancreas - %, size, location, hormone, function

A

15-20%
large
periphery
glucagon
glycogen breakdown and gluconeogenesis

73
Q

describe beta cells of endocrine pancreas - %, size, location, hormone, function

A

70% smaller
central
insulin - opposite of glucagon
uptake of glucose by liver and lower glucemia when eating

only one gene encodes insulin

74
Q

describe delta cells of endocrine pancreas - %, size, location, hormone, function

A

5%
large
periphery and central
somatostatin
inhibits release of glucagon and insulin via paracrine action and HCl secretion by parietal cells

75
Q

describe pancreatic polypeptide cells of endocrine pancreas - %, size, location, hormone, function

A

1%
large
periphery and central
pancreatic polypeptide
stimulates activity of chief cells

76
Q

describe role of glucagon

A

plays major role in maintaining normal concentrations of glucose in blood and has opposite effect of insulin

77
Q

what is glucagon. synthesized as

A

proglucagon and proteolytically processed ro glucagon within alpha cells of pancreatic iselts
final product = linear peptide of 29 aas
primary sequence highly conserved in vertebrates

78
Q

where is proglucagon expressed

A

also expressed within intestinal tract where it is processes to glucagon, like peptides = enteroglucagon - not into glucagon

79
Q

what is major effect of glucagon

A

major effect of glucagon = increase blood concentration of glucose as brain has an
absolute dependence on glucose as fuel
When blood levels of glucose begins to fall below normal Range -glucagon stimulates
breakdown of glycogen stored in liver and/or activates hepatic gluconeogenesis
like when asleep

80
Q

why are fenestrations important in islet cells

A

allows passage of hormones into lumen of capillary

81
Q

what does chronic ingestion of alcohol lead to

A

acute pancreatitis = due to obstruction of duct system and activation of trypsin or release of enzymes into intercellular space

82
Q

explain type 1 diabetes

A

insulin dependent diabetes mellitus develops before age of 15 which is apparently cause by an autoimmune destruction of the beta cells of islets

ANAT 261 (27 decks)

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