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111: Anatomy/Phys 2 > 4.0 Digestive > Flashcards

4.0 Digestive Flashcards

1
Q

how are contents of stomach released to duodenum, what happens upon the release

A
  • when stomach ready to release pyloric sphincter opens, stomach contracts to release contrents
  • only small amount of chyme goes into SI
  • duodenum detects contects have entered it -> secrets secretin (bc of dec pH), GIP and CCK (bc senses lipids and carbs)
  • those hormones enter circulation and inhibit peristalsis, inhibit chief cells from releasing pepsinogen, and parietal cells from releasing acid and intrinsic factpr
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2
Q

what triggers the release of CCK

A

pressence of lipids and carbs

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3
Q

what triggers release of GIP

A

presence of lipids and carbs

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4
Q

what triggers the release of secretin

A

dec pH

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5
Q

what is the status of digestion of the chyme when it enters the SI

A
  • Chyme is slowly released into duodenum ( v acidic could damage if too much at a time)
  • no fat digestion!
  • carbs and proteins are only partially digestioned
  • chyme is hypertonic and has low pH -> requres constant mixing for proper digestions
  • virtually all ntrient abs takes place in SI
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6
Q

digestion of alcohol

A

20% in stomach

80% in SI

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7
Q

what is the most common type of motion in the SI?

what initiates it?

A
  • segmentation = most common
  • initated by intrinsic paceaker cells (Cajal cells)

*moves contents steadily twds ileocecal valve

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8
Q

pacemaker activity in diff regsions of small intestine

A

cajal cell pacemaker activity differs in different regions of the GI tract:

-3 per minute in the stomach

12-14 per minute in the duodenum lots

8-9 per minute in the ileum

3 per minute in the colon

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9
Q

how is the intensity of segmentation controled

A
  • by short and long reflexs

Long reflex: PSN activity enhances, SNS activity decreases

  • more intense the contractions = greater mixing

* basic contractile rhythems of varioues intestinal regions remain unchances

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10
Q

when does peristalsis occur?

what happens during it?

A
  • peristalsis occurs after most nutrients have been absorbed
  • segmentations movements wane and duodenal mucosa begins to release motilin
  • peristaltic waves initiate at the duodenum and sweep slwoly along the intestine, mving 5-70cm before dying out
  • each wave is initiated a bit more distally (migrating motility complex MMC)
  • process sweeps the alst remnants of meal, bacteria and other debris into LI
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11
Q

release of ____ regulates peristalsis

A

released ACh by ACHe releasing (cholinergic) sensory neuron in SI sends messages to diff interneutons in myenteric plexus

  • regualtes peristalsis
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12
Q

what are the two places ACh can be sent for peristalsis, what is the effect?

A
  • impulses sent proximally: causes contraction and shortening of circular muscle layer
  • impulses sent distally cause shortening of logitudional layer and distension of intestine

* overall: proximal area constricts and foces chyme along tract - lumen of distal part of intestine enlage to receive it

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13
Q

release of ____ stimulates pancreatic secretion

A
  • secretin and cholecystokinin (CCK)
  • > Acidic chyme enterine duodenium signals releast of Sectretin

*causes secretion of bicarbonate rich pancreatic juice

-> fatty protein in chyme entering duodenum incudces CCK releas

*causes secretion of enzyme rich pancreatic juices

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14
Q

What controls the flow of digestive juices? what relaxes it?

A

Sphincter of Oddi (hepatopancreatic sphincter) controls flow of digestive juices (bile and pancreatic)

Cholecystokinin(CCK) relaxes it

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15
Q

describe the composition of pancreatic juice

A
  • has enzymes and electrolytes (primarily HCO3-_ that neutralize acid chyme
  • from exnymes are released as inactive zymogen and hten activatied

Zymogens in pancreatic juice: trypsin, chrmotrypsin, elastase, carboxypeptidase, phospholipase

Active enzymes: lapase, amylase, cholesterolesterase, ribonucleaes, deoxtribonuclease

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16
Q
A
17
Q

what physical featues in the small intestine help with the absorption of nutrients

A
  • large circular folds
  • filli and microvilli
  • blood capillaries

*ahve a lacteal running thru middle of villi

18
Q

how are carbohydrates abrobed

A

*primarily in SI

  • begins in mouth with salivary amylase -> starts starch digestion
  • pancreatic amylase -> digests startch to oligosaccharides
  • Oligosaccharides hydrolyed by brush border enzymes (disaccharides -> monosaccharides)

*Beta 1,4 bonds in cellulose not hydrolyzed

19
Q

how are sucrose, maltosea nd alctose broekn down

A

Sucrose —sucrase—> Glucose + fructose

Maltose — maltase—> glucose + glucose

Lactose —lactase—> glucose + galactose

20
Q

how are protiens digested

A
  • Pepsin in stomch -> cleaves proteins -> polypeptides
  • in SI: Pancreatic enzymes: trypsin, chymotrypsin and carboxypeptidase

brush border enzymes: aminopeptidaes, carboxypeptidass, dipeptidases

21
Q

how do proteins get absorbed

A
  • AA by cotransport with Na+
  • Dipeptides and tripeptides via secondary active transport with H+ gradient (then broekn down itno single aa)
22
Q

How are fats digested?

A
  • bile salts are produced and released by SI, stored in gall bladder -> to duodenum
  • hydrophobic side ass w/ lipid and hydrophillic w/ water -> forms a bile-acid coated lipid droplet

*enzymes can only attach the surface so need to icnrease the SA by breaking down fat globule into smaller parts

  • once emulsified -> digestion by lipases -> longchain FA and monoglycerides
23
Q

how are fats absorbed

A
  • short chian fatty acids -> simple iffusion across SI into blood capillary
  • > long chain fA and monoglycerides -> simple diffusion but processed i epithelium as chylomicrons -> then go to lacteal of a villus
24
Q

describe the digestion of nucleic acids

A
  • digested by Pancratic ribconucleases and doxyribonuclease in SI
  • absorbed by active transport via membrane carriers

> absorbed in villi & transported to liver via hepatic portal vein

25
Q

what electrolytes are absorbed/how?

A
  • Na+ is coupled with absorption of glucose and AAs
  • Iron is transported into cells where it binds to ferritin
  • Anions passively follow the electrical potential established by Na+
  • K+ diffuses across the intestinal mucosa in response to osmotic gradients
  • Ca2+ absorption is regulated by vitamin D and parathyroid hormone (PTH)
26
Q

what methods can ions be transported by?

A
  • diffusion, co transport, active, or carrier mediated
27
Q

how is water absorbed

A

95% is absorbed in SI by osmosis

  • water moves bidirectionally across intestinal mucosa
  • Net osmosis occurs whenever a concentration gradient is established by active transport of solutes into mucosal cells
28
Q

what are the 3 unique features of the LI

A
  • Teniae coli - three bands of longitudinal smooth muscle in its muscularis
  • Haustra - pocketlike sacs caused by the tone of the teniae coli
  • Epiploic appendages - fat-filled pouches of visceral peritoneum

* saclike cecum lies below the ileocecal valve and contains a wormlike vermiform appendix

29
Q

what types of cells are found in the large intestine?

what strucutral features is it missing that other organs in the digestive system have?

A
  • colon mucose = simple columnar epithelium except in anal canal
  • anal canal = stratefied squamous epithelium -> merges w/ true skin surrounding the anus
  • Does NOT have circular folds, villa, or cells that secrete digestive enzymes
30
Q

what produces mucus in the LI

A
  • goblet cells
  • eases the passage of feces and protects intestinal wall from irritating acids and gases
31
Q

describe the motility of the large intestine

where does it priamrily occur

A
  • movements = haustral contractions (slow segmentating movements lasting 1min, occur ever 30 sec
  • occurs ainly in transverse and descending colon -> reflect local controls of smooth muscle within the walls of the individual haustra
  • as haustrum fills with food residue, the distension stimulates its muscle to contract, which propels the luminal contents into the next haustrum
  • LI has mass movements contractile waves -> move over alrge areas of colon 3-4x/day, forces contents to rectum
32
Q

what reflexes are activates when food enters teh stomach

A
  • Gastroileal reflex: in the SI
  • Gastrocolic reflex: in colon
33
Q

what does bulk (fiber) do to the stool

A
  • softens the stool and can inc strength of colon contractions
34
Q

what is the function of large intestine

A
  • Other than digestion of enteric bacteria, no further digestion takes place
  • reclaims vitamins, water and electorlytes

*major fucntion is propulsion of fecel material towards anus (storage)

*not essential for life (but convient bc want to be able t control your defication)

35
Q

describe the bacteria in the colon

A
  • remaining bacteria from the SI colonize the colon
  • > Metabolize some host-derived proteins (mucin, heparin, and hyaluronic acid)
  • > Ferment some of the indigetibel carboydrates (cellulose, xylan and others)
  • release irritating acids and mix of gases (dimethyl sulfide, H2, N2, CH4, and CO2)
  • 500mL of gas (flatus)/day, more if consume carb heavy foods (beans)
  • synthesize B complex vitamind and most of vit K in liver requires to synthesize some of the clotting proteins
36
Q

describe the anus

A
  • has a pectinate line to sep superior and inferior
  • > Superior: mucoase innervated by visceral sensory fibers, INSENSITIve to pain
  • > Inferior: very sensitive to pain bc of somatic sensroy fibers’
  • has 2 superficial venous plexuses: 1 in part of anal columns and 2 the anus

*If these (hemorrhoidal) veins are inflamed, itchy varicosities called hemorrhoids can form

37
Q

painful vs not painful hemorrhoids

A
  • external are painful, if on internal vein will hang out ed of anus
38
Q

describe defication

A
  • dsitension of rectal walls caused by feces
  • > stimulates contraction of rectal walls
  • > relaxes internal anal sphincter
  • Voluntary signals stimulate relaxation of the external anal sphincter and defecation occurs

111: Anatomy/Phys 2 (31 decks)

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