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.
2
Q
peritoneal cavity
A
between 2 peritoneum’s. contains serous fluid, lubricate mobile digestive organs
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
4
Q
retroperitoneal organs
A
pancreas, duodenum + parts of large intestine no mesentery.
5
Q
intra peritoneal organs
A
stomach, keep mesentery and remain in peritoneal cavity
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
7
Q
sphincters
A
separate the tract into segments with distinct functions.
8
Q
chyme
A
food + secretion
9
Q
epiglottis
A
prevents food from going into trachea.
10
Q
after oral cavity
A
pharynx into larynx and esophagus. to the abdomen.
11
Q
esophagus
A
sekeltal muscles transitions into smooth. ends in stomach
12
Q
stomach
A
3 sections:
- upper fundus
- central body
- lower antrum
13
Q
cardia
A
esophagus connects to stomach
14
Q
pylorus
A
opening stomach and small intestine. guarded by pyloric valve. band of smooth muscle
15
Q
small intestine
A
3 sections:
- duodenum
- jejunum
- ileum
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.
17
Q
large intestine
A
regions
- ileocecal valve
- cecum
- colon
- rectum
- anal canal
18
Q
ileocecal valve
A
between ileum and cecum, controls flow of chyme
19
Q
cecum
A
continues absorption of water + salts. appendix is a winding tube that attaches to cecum
20
Q
colon
A
parts:
- ascending
- right colic flexure
- transverse
- left colic
- descending
- sigmoid
21
Q
rectum
A
3 lateral bends, create tinternal transverse folds –> rectal valves. separate feces from gas to prevent simultaneous passage
22
Q
anal canal
A
2 sphincters
internal and external
internal: smooth muscle
external: skeletal
23
Q
colon function
A
watery chyme converted into feces. water + electrolytes are absorbed into ECF. feces are propelled into terminal section: rectum
24
Q
rectum function
A
distension of wall triggers defecation reflex. feces leave through anus. voluntary control
25
gut
GI tract from stomach to anus
26
gastrointestinal wall
- inner mucosa
- submucosa
- muscularis mucosae
27
mucosa gastrointestinal
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
28
increase surface area
rugae --> stomach
plicae --> small intestine
villi --> intestinal mucosa
also tubular invaginations --> supports connective tissue:
gastric glands --> stomach
crypts --> intestine
submucosal glands --> deepest invaginations.
29
epithelial cells (transport)
include transporting epithelial cells (enterocytes), endocrine + exocrine secretory cells, stem cells. secrete ions + water into lumen and absorb ions water and nutrients into ECF.
30
secretory cells
- mucosal surface release enzymes, mucus and paracrine molecules into lumen
- serosal surface secrete hormones into blood/paracrine messengers into interstitial fluid.
31
junctions
stomach + colon: junctions form tight barrier.
| small intestine: not as tight. considered leaky, water and solutes can be absorbed between them --> paracellular
32
nodules + peyer's patches
intestine collections of lymphoid tissue adjoining epithelium.
these aggregations are major part of gutassociated lymphoid tissue (GALT)
33
submucosa gastrointestinal
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.
34
muscularis externa + serosa
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.
35
myenteric plexus
controls + coordinates motor activity of muscularis externa.
36
serosa
the outer covering the entire GI tract. connective tissue membrane. continuation of peritoneal membrane.
37
motility
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
muscle contractions
3 general patterns.
empty: in stomach contractions passes slowely to other sections.
90 min to reach large intestine --> migrating motor complex. housekeeping function.
39
perisalsis
waves of contraction from one section of the tract to the next. circular muscles contract behind mass. pushes the bolus forward.
40
segmental contractions
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
tonic contractions
can be sustained for minutes/hours and occur in smooth muscle sphincters + anterior portion stomach
42
phasic contractions
contraction-relaxtion cycles lasting few sec. occur in posterior region stomach + small intestine
43
cells of cajal
pacemaker, creates bioelectrical slow wave potential, leads to contraction smooth muscle
44
haustral contraction
presence of food residues is stimulus. involves slow segmentation in transverse + descending colon.
haustrum give colon segmented appearance is distende, muscle contracts.
45
peristalsis large intestine
presence of food is stimulu.
46
mass movement
midway transverse colon, quickly force content to rectum while eating/after.
47
gastrocolic reflex
destension + breakdown products in small intestine is stimulu. increases motility, including mass movement.
48
parietal cells
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
chief cells
pepsinogen
50
G-cells
mucous
51
ECL-cells
histamine
52
bicarbonate secretion
secreted by duodenal cells + pancreas --> NaHCO3.
53
exocrine portion pancreas
lobules --> acini
open ducts whose lumens are part of the body's external environment.
acinar cells secrete enzymes + duct cells secrete NaHCO3.
54
acinar cells
exocrine portion pancreas
| secrete enzymes
55
duct cells pancreas
secrete NaHCO3
56
islet cells pancreas
hormones secretion
57
bicarbonate production
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
sodium + water movement
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
pancreatic cells
produce trypsin, deoxyribonuclease, ribonuclease
60
crypt cells
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
digestive enzymes
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
zymogens
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
salivary glands
produce alfa-amylase --> breaks down glycogen + starch into dextrin + maltose.
64
stomach glands
secrete pepsin --> breaks down proteins into polypeptides
65
liver
produces bile, stored in gallbladder, emulsifies lipids
66
pancreas enzymes
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
intestine enzymes
peptidase: proteins --> AA.
isomaltase: dextrin --> glucose
maltase: maltose --> glucose
sacharase: sacharose --> glucose + fructose
lactase: lactose --> glucose + galactose
nuclease, nucleotidase, nucleosidase: DNA + RNA
68
mucus
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
saliva
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
bile
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
gallbladder
stores and concentrates bile. contraction sends bile into duedenum through common bile duct + bicarbonate and digestive enzymes from pancreas. not essential for digestion
72
crypt cells large intestine
secrete NaCl
73
small intestine absorption
most absorption.
surface area increased by vili and brush border , created from microvilli.
crypts: specialized for fluid + hormone secretion.
74
lacteals
lymph vessels that absorb fats.
75
saccharides
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
intestinal glucose + galactose absorption
use transporters: apical Na+-glucose SGLT symporter + GLUT2 transporter.
fructose is not Na+ dependent. moves across by facilitated diffusion on GLUT5 transporter.
77
intestinal cells, enterocytes energy
glutamine --> AA
78
endopeptidase
attack peptide bonds in interior of AA chains + breaks peptide into smaller fragments.
secreted inactive in stomach, intestine + pancreas
79
exopeptidase
release single AA from peptides by chopping them at the end. most important carboxylpeptidase.
aminopeptidase is less important.
80
amino acids absorption
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
fats
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
micelles
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
nucleic acids
digested by pancreatic + intestinal enzymes. first into nucleotides --> nitrogenous bases + monosaccharides. bases absorbed by active transport, monosaccharides via facilitated diffusion + active transport
84
vitamins
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
mineral absorption
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
hepcidin
regulates uptake of iron. binds to ferroprotin. targeted for destruction by enterocytes.
87
Ca2+ absorption
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
water
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.
