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BBS1002 > case 9 > Flashcards

case 9 Flashcards

1
Q

peritoneum

A

most extensive membrane

visceral peritoneum: covers external surfaces of most GI organs continuous in parietal peritoneum –> lines body wall.

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2
Q

peritoneal cavity

A

between 2 peritoneum’s. contains serous fluid, lubricate mobile digestive organs

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3
Q

mesentery

A

double layer of peritoneum, extends to GI organs from body wall, proves routes for blood vessels, lymphatics + nerves. holds organs in place + stores fat.
dorsal and ventral

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4
Q

retroperitoneal organs

A

pancreas, duodenum + parts of large intestine no mesentery.

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5
Q

intra peritoneal organs

A

stomach, keep mesentery and remain in peritoneal cavity

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6
Q

begin GI tract

A

oral cavity, receptacle for food.
contains 3 paris of salivary glands (sublingual), submandibular (under mandible) + parotid near hinge of jaw.
major: submandibular
minor: sublingual + parotid

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7
Q

sphincters

A

separate the tract into segments with distinct functions.

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8
Q

chyme

A

food + secretion

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9
Q

epiglottis

A

prevents food from going into trachea.

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10
Q

after oral cavity

A

pharynx into larynx and esophagus. to the abdomen.

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11
Q

esophagus

A

sekeltal muscles transitions into smooth. ends in stomach

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12
Q

stomach

A

3 sections:

  • upper fundus
  • central body
  • lower antrum
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13
Q

cardia

A

esophagus connects to stomach

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14
Q

pylorus

A

opening stomach and small intestine. guarded by pyloric valve. band of smooth muscle

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15
Q

small intestine

A

3 sections:

  • duodenum
  • jejunum
  • ileum
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16
Q

two accessory glandular organs

A

pancreas + liver
secretions enter duodenum through ducts. sphincter keeps pancreatic fluid + bile from entering small intestine, except during a meal.

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17
Q

large intestine

A

regions

  • ileocecal valve
  • cecum
  • colon
  • rectum
  • anal canal
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18
Q

ileocecal valve

A

between ileum and cecum, controls flow of chyme

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19
Q

cecum

A

continues absorption of water + salts. appendix is a winding tube that attaches to cecum

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20
Q

colon

A

parts:
- ascending
- right colic flexure
- transverse
- left colic
- descending
- sigmoid

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21
Q

rectum

A

3 lateral bends, create tinternal transverse folds –> rectal valves. separate feces from gas to prevent simultaneous passage

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22
Q

anal canal

A

2 sphincters
internal and external
internal: smooth muscle
external: skeletal

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23
Q

colon function

A

watery chyme converted into feces. water + electrolytes are absorbed into ECF. feces are propelled into terminal section: rectum

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24
Q

rectum function

A

distension of wall triggers defecation reflex. feces leave through anus. voluntary control

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25
Q

gut

A

GI tract from stomach to anus

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26
Q

gastrointestinal wall

A
  • inner mucosa
  • submucosa
  • muscularis mucosae
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27
Q

mucosa gastrointestinal

A

inner lining
- single layer epithelial
- lamina propria, subepithelial connective tissue, holds epithelium.
contains nerve fibers + small blood and lymph vessels. absorbed nutrients taken up here
- muscularis mucosae: thin layer smooth muscle. contraction affects absorption

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28
Q

increase surface area

A

rugae –> stomach
plicae –> small intestine
villi –> intestinal mucosa
also tubular invaginations –> supports connective tissue:
gastric glands –> stomach
crypts –> intestine
submucosal glands –> deepest invaginations.

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29
Q

epithelial cells (transport)

A

include transporting epithelial cells (enterocytes), endocrine + exocrine secretory cells, stem cells. secrete ions + water into lumen and absorb ions water and nutrients into ECF.

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30
Q

secretory cells

A
  • mucosal surface release enzymes, mucus and paracrine molecules into lumen
  • serosal surface secrete hormones into blood/paracrine messengers into interstitial fluid.
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31
Q

junctions

A

stomach + colon: junctions form tight barrier.

small intestine: not as tight. considered leaky, water and solutes can be absorbed between them –> paracellular

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32
Q

nodules + peyer’s patches

A

intestine collections of lymphoid tissue adjoining epithelium.
these aggregations are major part of gutassociated lymphoid tissue (GALT)

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33
Q

submucosa gastrointestinal

A

has larger blood and lymph vessels.
contains submucosal plexus: one of two major nerve networks of enteric nervous system. innervates cells in epithelial as well as smooth muscle of musculris mucosae.

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34
Q

muscularis externa + serosa

A

2 layers smooth muscle, inner circular + outer longitudinal.
contraction:
circular: decreases diameter lumen
longitudinal: shortens tube
stomach: oblique muscle between circular and submucosa
myenteric plexus between longitudinal and circular muscles.

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35
Q

myenteric plexus

A

controls + coordinates motor activity of muscularis externa.

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36
Q

serosa

A

the outer covering the entire GI tract. connective tissue membrane. continuation of peritoneal membrane.

37
Q

motility

A

2 purposes
- moving food from mouth to anus
- mechanically mixing food to break it down.
determines by properties of tract’s smooth muscle
+ modified by chemical input from nerves, hormones + paracrine signals.

38
Q

muscle contractions

A

3 general patterns.
empty: in stomach contractions passes slowely to other sections.
90 min to reach large intestine –> migrating motor complex. housekeeping function.

39
Q

perisalsis

A

waves of contraction from one section of the tract to the next. circular muscles contract behind mass. pushes the bolus forward.

40
Q

segmental contractions

A

short segments of intestine alternately contract + relax. circular contract + longitudinal relax. may occur randomly. mix the intestinal contents and keep them in contact with epithelium. contract sequentially, oral-to-aboral directing

41
Q

tonic contractions

A

can be sustained for minutes/hours and occur in smooth muscle sphincters + anterior portion stomach

42
Q

phasic contractions

A

contraction-relaxtion cycles lasting few sec. occur in posterior region stomach + small intestine

43
Q

cells of cajal

A

pacemaker, creates bioelectrical slow wave potential, leads to contraction smooth muscle

44
Q

haustral contraction

A

presence of food residues is stimulus. involves slow segmentation in transverse + descending colon.
haustrum give colon segmented appearance is distende, muscle contracts.

45
Q

peristalsis large intestine

A

presence of food is stimulu.

46
Q

mass movement

A

midway transverse colon, quickly force content to rectum while eating/after.

47
Q

gastrocolic reflex

A

destension + breakdown products in small intestine is stimulu. increases motility, including mass movement.

48
Q

parietal cells

A

secrete hydrochloric acid into lumen of stomach. pH cells is 7.2. they pump H_ against higher gradient.
- process:
H+ from water inside cell pumped into stomach lumen by H+-K+-ATPase in exchange K+. CL- follows H+ through chloride channel. net secretion of HCL>
bicarbonate is made and absorbed into blood.

49
Q

chief cells

A

pepsinogen

50
Q

G-cells

A

mucous

51
Q

ECL-cells

A

histamine

52
Q

bicarbonate secretion

A

secreted by duodenal cells + pancreas –> NaHCO3.

53
Q

exocrine portion pancreas

A

lobules –> acini
open ducts whose lumens are part of the body’s external environment.
acinar cells secrete enzymes + duct cells secrete NaHCO3.

54
Q

acinar cells

A

exocrine portion pancreas

secrete enzymes

55
Q

duct cells pancreas

A

secrete NaHCO3

56
Q

islet cells pancreas

A

hormones secretion

57
Q

bicarbonate production

A

requires high levels of carbonic anhydrase, similar to renal tubule + RBC.
secreted by apical CL-HCO3 exchanger.
hydrogen produced along HCO3 leaves the cell with H+-NA+ exchangers. H+ reabsorbed into intestinal circulation helps balance HCO3-.

58
Q

sodium + water movement

A

passive + driven by electrochemical + osmotic gradients. net movement of negative ions from ECF attracts Na+, moves through leaky junctions.
secreton of Na+ + HCO3- into lumen creates osmotic gradient and water follows.

59
Q

pancreatic cells

A

produce trypsin, deoxyribonuclease, ribonuclease

60
Q

crypt cells

A

small intestine + colon, secreate NaCl, mixes with mucus help lubricate contents. active step is CL- secretion. it enters by Na+-K+-Cl- co transporter (NKCC). exits into lumen via CFTR channels.

61
Q

digestive enzymes

A

secreted by
- exocrine glands: salivary/pancreas
- epithelial cells: mucosa stomach + small intestine.
many enzymes bound to apical membranes of intestinal cells, anchored by transmembrane portein ‘stalks’/ lipid anchors

62
Q

zymogens

A

inactive proenzyme form.
must be activated in the lumen. this late actviation allows enzymes to be stored in cells that make them without damagin cells. often have prefix -ogen added to them

63
Q

salivary glands

A

produce alfa-amylase –> breaks down glycogen + starch into dextrin + maltose.

64
Q

stomach glands

A

secrete pepsin –> breaks down proteins into polypeptides

65
Q

liver

A

produces bile, stored in gallbladder, emulsifies lipids

66
Q

pancreas enzymes

A

secretes trypsin + chymotrypsin.
chymotrypsin works on aromatic AA and trypsin on basic AA.
AA break down into polypeptides.
peptidase: proteins –> AA.
lipase: emulsified fats –> monoglycerides + fatty acids.
alfa-amylase –> starch + glycogen into dextrin + maltose

67
Q

intestine enzymes

A

peptidase: proteins –> AA.
isomaltase: dextrin –> glucose
maltase: maltose –> glucose
sacharase: sacharose –> glucose + fructose
lactase: lactose –> glucose + galactose
nuclease, nucleotidase, nucleosidase: DNA + RNA

68
Q

mucus

A

viscous secretion composed of glycoproteins –> mucins.
function: protective coat GI mucose + lubricate contents of gut.
made of special exocrine cells :
- mucous cells: stomach
- serous cells: salivary glands
- goblet cells: intestine
parastic infections cause increases in mucus.

69
Q

saliva

A

hypoosmotic fluid secreted by salivary glands.
exocrine organized into acini + ducts.
components: water, ions, mucus + proteins.
composition determined in 2 epithelial transport steps
- acinar cells fluid resembles ECF in composition (NaCl). fluid passes through duct, epithelial cells along reabsorb Na+ and secrete K+ until composition is more like ICF.
ducts low water permeability, net removal results in hypoosmotic.

70
Q

bile

A

non-enzymatic solution
secreted from hepatocytes/liver cells
components:
- bile salts, facilitate enzymatic fat digestion. made of bile acids + AA
- pigments, bilirubin, wate products of hemoglobin/degradation
- cholesterol, excreted in the feces.

71
Q

gallbladder

A

stores and concentrates bile. contraction sends bile into duedenum through common bile duct + bicarbonate and digestive enzymes from pancreas. not essential for digestion

72
Q

crypt cells large intestine

A

secrete NaCl

73
Q

small intestine absorption

A

most absorption.
surface area increased by vili and brush border , created from microvilli.
crypts: specialized for fluid + hormone secretion.

74
Q

lacteals

A

lymph vessels that absorb fats.

75
Q

saccharides

A

restricted to monosaccharides.
cellulose: used as dietary fiber.
amylase: breaks down long glucose polymers into smaller chains + maltose.
maltose + other disaccharides broken down by intestinal brush border ezymes: disaccharidases. end products: glucose, galactose, fructose

76
Q

intestinal glucose + galactose absorption

A

use transporters: apical Na+-glucose SGLT symporter + GLUT2 transporter.
fructose is not Na+ dependent. moves across by facilitated diffusion on GLUT5 transporter.

77
Q

intestinal cells, enterocytes energy

A

glutamine –> AA

78
Q

endopeptidase

A

attack peptide bonds in interior of AA chains + breaks peptide into smaller fragments.
secreted inactive in stomach, intestine + pancreas

79
Q

exopeptidase

A

release single AA from peptides by chopping them at the end. most important carboxylpeptidase.
aminopeptidase is less important.

80
Q

amino acids absorption

A

free AA are carried by Na+ dependent cotransport and few H+ dependent.
di/tripeptides carried into mucosal cells on oligopeptide transporter PepT1, uses H+ dependent. once insed the oligopeptides have 2 possible fates. most digested into AA than transported into circulation.
other: intact on H+ dependent exchanger. mainly essential AA.

81
Q

fats

A

bile salts are amphipathic, have both hydrophobic and hydrophilic region.
hydrophobic: associate with surface lipid droplets while polar side chains interact with water.
lipases: removes 2 fatty acids from each triglycerdie and form 2 free fatty acids and one monoglyceride.
lipase not able to penetrate bile salts. fat digestion needs co-lipase. secreated by pancreas. desplaces bile salts, allowing lipase acces to fats.
phopholipids are digested by pancreatic phospholipase.

82
Q

micelles

A

formed by fatty acids, bile salts, monoglycerides, phospholipids + cholesterol. enter unstirred aqueous layer close to enterocytes.
fatty acids + monoglycerides move into smooth ER –> recombine into triglycerides. they join cholesterol to form chylomicrons, have to be transported through lacteals.

83
Q

nucleic acids

A

digested by pancreatic + intestinal enzymes. first into nucleotides –> nitrogenous bases + monosaccharides. bases absorbed by active transport, monosaccharides via facilitated diffusion + active transport

84
Q

vitamins

A

fat soluble vitamins absorbed in small intestine with fats.
water soluble vitamins absorbed by mediated transport.
exception: B12. made by bacteria, obtain most supply from sea food, milk, meat.
intestinal transporter for B12 found only in ileum, only recognizes it with protein: intrinsic factor.

85
Q

mineral absorption

A

occurs by active transport.
iron + calcium intestinal absorption is actively regulated. decreased concentrations leads to increased uptake.
heme iron: absorbed by transporter on enterocytes.
ionized iron: actively absorbed by cotransport with H+ on protein: divalent metal transporter 1 –> DMT1.
inside cell: enzymes convert heme iron to Fe2+. iron leaves the cell on ferroportin (transporter).

86
Q

hepcidin

A

regulates uptake of iron. binds to ferroprotin. targeted for destruction by enterocytes.

87
Q

Ca2+ absorption

A

passive unregulated movement –> paracellular pathways.
hormonally regulated: takes place in duodenum.
calcium enters enterocyte through Ca2+ channels and actively transported across basolateral membrane by Ca2+ ATPase or Na+-Ca2+ antiporter.
regulated by vitamin D3.

88
Q

water

A

absorbed in small intestine. 0.5 L per day in colon. follows osmotic gradient. enterocytes + colonocytes absorb Na+ using 3 proteins: Na+ channels, Na+-Cl symporter and Na+-H+ exchanger (NHE).
small intestine: lot of Na+ is taken up by Na+ dependent organic solute uptake.
basolateral side: primary transporter: Na+-K+ ATPase. chloride uptake uses CL-HCO3 exchanger and basolateral Cl- channel.
potassium + water absorption in intestine occur by paracellular pathway.

BBS1002 (10 decks)

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