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Phys 2 Exam 2 > GI physiology > Flashcards

GI physiology Flashcards

1
Q

functions of GI

A

digestion & absorption

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2
Q

4 major activities of GI tract

A

Motility propels ingested food from mouth toward the rectum & mixes and reduces the side of food

Secretions from salivary glands, pancreas, and liver add fluid, electrolytes, enzymes, and mucus to the lumen

Ingested foods are digested into absorbable molecules

Nutrients, electrolytes, and water are absorbed from the intestinal lumen into the blood stream

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3
Q

Extrinsic innervation of GI tract

A

sympathetic and parasympathetic

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4
Q

parasympathetic innervation of GI tract

A

supplied by Vagus & Phrenic nerve

Vagus - innervate upper GI

Phrenic - innervate lower GI

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5
Q

Sympathetic innervation

A

preganglionic fibers – postganglionic adrenergic nerve fibers

directly innervate:

  • smooth muscle
  • endocrine
  • secretory cells
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6
Q

Intrinsic innervation of Gi tract

A

enteric nervous system

can carry on if extrinsic failed/ contained in 2 plexuses

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7
Q

GI peptide function

A

Contraction/ relaxation of smooth muscle wall/ sphincters

Secretion of enzymes for digestion

Secretion of fluid and electrolytes

Trophic (growth) effects of GI tract

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8
Q

Paracrine

A

Do not enter the systemic circulation but act locally – reaching their target cells by diffusing over short distances

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9
Q

2 types of paracrine

A

Somatostatin - secreted by D cells of GI mucosa in response to decrease luminal pH

Histamine- secreted by endocrine cells of GI mucosa (H+ secretion region)

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10
Q

smooth muscle

A

no striations / move things along / maintain tension

all contractile tissue of GI tract is smooth muscle

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11
Q

where is smooth muscle not present in GI

A

pharynx , upper 1/3 of esophagus & external sphincter

striated muscle

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12
Q

motility

A

Grinds, mixes, and fragments ingested food to prepare it for digestion & absorption —- then propels food along GI tract

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13
Q

When circular muscle contracts =

A

there is shortening of a ring of smooth muscle

This DECREASES the diameter of that segment

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14
Q

When longitudinal muscle contracts =

A

there is shortening in the longitudinal direction

This DECREASES the length of the segment

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15
Q

phasic & tonic contractions of GI

A

phasic - opening & closing

tonic - chronic contraction

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16
Q

3 functions of chewing

A

mix food with salvia
decreases size of food particles
mixes ingested carbohydrates w/ salivary amylase (carb digestion)

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17
Q

involuntary component of chewing

A

reflexes initiated by food in mouth (mechanoreceptors)

brain stem orchestrates reflex oscillatory pattern of activity to the muscles involved in chewing

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18
Q

swallowing & sensory information (CNS)

A

o Initiated voluntary in the mouth –> but after it is under involuntary (reflex) control

Controlled by swallowing center in medulla

Sensory information (food in mouth) is detected by somatosensory receptors by pharynx

Sensory (afferent) information is carried to swallowing center

The medulla coordinated and directed motor (efferent) output to pharynx and upper esophagus

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19
Q

what happens to swallowing if vagus nerve is damaged?

A

it effects receptive relaxation

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20
Q

Oral phase

A

initiated when tongue forces bolus of food back toward pharynx

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21
Q

Pharyngeal Phase

A

Propel food bolus from the mouth through the pharynx to espoguagus in the following steps:

  • Soft palate is pulled upward
  • Epiglottis moves to cover the opening to the larynx & larynx moves upward against epiglottis
  • Upper esophageal sphincter relaxes
22
Q

Esophageal Phase

A

Controlled in part by the swallowing reflex and by enteric nervous system
 Food is propelled through esophagus to the stomach

• The swallowing reflex closes the sphincter so food cannot reflux into the pharynx

23
Q

primary peristaltic wave

A

Travels down the esophagus propelling the food along

24
Q

swallowing function

A

Upper esophageal sphincter to prevent air from entering the upper esophagus

Lower esophageal sphincter to prevent the acidic gastric contents from entering the lower esophagus

CLOSED except for when food is passing

25
Q

3 components of gastric motility

A

relaxation -receive food
contractions -reduce size & mix
gastric emptying - propels chyme to small intestine

26
Q

Innervation of stomach

A 
extrinsic = ANS
Intrinsic = Plexus
27
Q

receptive relaxation

A

decreases pressure and increases volume of the orad stomach

28
Q

mixing and digestion contractions

A

contractions start in the middle and move distally in the cuadad of stomach

29
Q

gastric emptying

A

rate must be closely regulated to provide time for

  • neutralization of H+ in duodenum
  • digestion and absorption of nutrients

liquid empty faster than solids

30
Q

two major factors that slow gastric emptying (increase gastric emptying time)

A

presence of fat

presence of H+ ions (decrease pH in duodenum)

31
Q

Small Intestine Motility serves to

A

Mix chyme with digestive enzymes and pancreatic secretions

Expose nutrients to the intestinal mucosa for absorption

Propel unabsorbed chyme along the small intestine into the large intestine

32
Q

Parasympathetic Small Intestine Motility

A

stimulation increases contraction

33
Q

Sympathetic Small Intestine Motility

A

decreases contraction

34
Q

Large Intestine Motility

A

Destined for excretion

After the contents of the small intestine enter the cecum and proximal colon, the ileocecal sphincter contracts, preventing reflux into the ileum

Fecal material then moves from the cecum through the colon to the rectum and to the anal canal

35
Q

secretions are produced by

A

salivary glands
gastric mucosa
exocrine of pancreas
liver

36
Q

saliva functions

A

dilution, buffering, & lubrication of food

37
Q

HCl secretions

A

stomach ph = 1 & 2

low pH of the stomach converts pepsinogen to pepsin

38
Q

pepsin

A

protease that begins the process of protein digestion

39
Q

Intrinsic factor secretion

A

mucoprotein/secretroy produce of parietal cells

required for absorption of vitamin B12

only essential secretion of stomach

40
Q

pancreatic secretion consist of

A

An aqueous component that is high in HCO3- which functions to neutralize the H+ delivered to the duodenum from the stomach

An enzymatic component that functions to digest carbohydrates, proteins, and lipids into absorbable molecules

41
Q

Bile

A

mixture of bile salts, bile pigments, and cholesterol solves the problem of insolubility

42
Q

organic constituents of bile

A

bile salts
bile pigments (bilirubin)
cholesterol
phospholipids

bile also contains electrolytes and water (secreted by hepatocytes lining the bile ducts)

43
Q

functions of gallbladder

A

stores bile

concentrates bile

when stimulated to contract
–>ejects bile into lumen of small intestine

begins w/in 30 minutes after a meal is ingested

44
Q

villi & microvilli

A

Increase surface area of the small intestine

Maximize the exposure of nutrients to digestive enzymes

Create a large absorptive surface

45
Q

Villi are longest in the ___

A

duodenum

Most digestion and absorption occurs

Shortest in the terminal ileum

46
Q

Digestion of Proteins

A

o Amino acids, dipeptides, and triptidies

Dietary proteins are digested to absorbable forms by proteases in the stomach and small intestine and then absorbed into the blood

47
Q

Intestinal Absorption

A

Intestinal epithelial cells lining the villi absorb large volumes of fluid

fluid is always isosmotic

o The solute absorptive mechanism vary among the jejunum, the ileum, and the colon

48
Q

functions of liver

A

o Processing of absorbed substances

o Synthesis & secretions of bile acids

o Bilirubin production/ excretion

o Participation in metabolism of key nutrients
(Carbohydrates, protein, and lipids)

o Detoxification and excretion of waste products

49
Q

Metabolic Functions of the Liver

A

Liver participates in the metabolism of carbohydrates, protein, and lipids

50
Q

In carbohydrate metabolism of the LIver

A

o The liver performs gluconeogenesis

o Stores glucose as glycogen

o Releases stored glucose into the bloodstream when needed

51
Q

In protein metabolism of liver

A

o The liver synthesizes the non-essential amino acids

o Modifies amino acids so that they may enter biosynthetic pathways for carbohydrates

52
Q

Detoxification of Substances

A

The liver protects the body form potentially toxic substances that are absorbed from the GI tract

Phys 2 Exam 2 (3 decks)

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