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UT BME 365S > Exam 3: Digestive System > Flashcards

Exam 3: Digestive System Flashcards

1
Q

major processes of the digestive system

A

digestion

absorption

secretion

mobility

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2
Q

primary functions of the digestive system

A

digestion, absorption, elimination

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3
Q

digestion

A

process of breaking down food into smaller chemicals used as nutrients by the body

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4
Q

mechanical digestion

A

physical breakdown of food into smaller pieces

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5
Q

chemical digestion

A

enzymes break down food into small molecules that the body can use

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6
Q

absorption

A

absorption of digested food (nutrients) from the tract to the blood stream in the body (from GI lumen to ECF)

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7
Q

elimination

A

excretion of waste from the body

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8
Q

mouth

A

movement: chewing
digestive juice: saliva
food particles broken down: starches

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9
Q

esophagus

A

movement: swallowing
digestive juice: none
food particles broken down: none

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10
Q

stomach

A

movement: muscle mixes food with digestive juices
digestive juice: stomach acid
food particles broken down: protein

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11
Q

small intestine

A

movement: peristalsis
digestive juice: small intestine digestive juice
food particles broken down: starches, protein, and carbohydrates

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12
Q

pancreas

A

movement: none
digestive juice: pancreatic juice
food particles broken down: starches, fats, and protein

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13
Q

liver

A

movement: none
digestive juice: bile acids
food particles broken down: fats

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14
Q

motility

A

movement of material through the GI tract as a result of muscle contraction

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15
Q

secretion

A

movement of material from cells into lumen or ECF

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16
Q

which GI processes are the primary regulated functions? why?

A

motility and secretion

motility: food cannot move too rapidly or else not everything will be digested and absorbed

secretion: allows digestive enzymes to break down food into an absorbable form when the food is at the correct location

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17
Q

what controls motility, secretion, and growth of the digestive tract?

A

enteric nervous system

this takes place INDEPENDENTLY of control from the central nervous system

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18
Q

enteric nervous system

A

200-600 million nerve cells

spans from esophagus to the anal sphincter

branches extend to the liver, gall bladder, biliary tract, and pancreas

aka “second brain”

connections exist between it and the CNS and are known as the Gut-Brain Axis

part of the autonomic nervous system (controls bodily functions that are not consciously directed); consists of the parasympathetic, sympathetic, and enteric nervous systems

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19
Q

parasympathetic nervous system

A

rest and digest: controls the body’s ability to relax

constricts pupils

stimulates flow of saliva

constricts bronchi

slows heartbeat

stimulates peristalsis and secretion

stimulates bile release

contracts bladder

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20
Q

sympathetic nervous system

A

fight of flight: controls the body’s response to an attack

dilates pupils

inhibits salivation

relaxes bronchi

accelerates heartbeat

inhibits peristalsis and secretion

stimulates glucose production and release

secretion of adrenaline and noradrenaline

inhibits bladder contraction

stimulates orgasm

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21
Q

chewing

A

masticating

physical breakdown by teeth and tongue

hydrolysis: enzymatic breakdown via amylase

makes the bolus

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22
Q

salivary secretion

A

humans have over 200 different proteins and peptides in the saliva

water and mucus soften and lubricate food for easy swallowing/dissolves food for taste

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23
Q

what glands secrete saliva

A

sublingual gland: under the tongue

submandibular gland: under the jawbone

parotid gland: near the hinge of the jaw

24
Q

salivary amylase

A

breaks down amylose (starch) into maltose (sugar made of two glucose molecules bound together)

inactivated in the stomach by gastric acid

25
Q

salivary lingual lipase

A

functional only at very low pH

degrades fats but only with stomach acid

26
Q

protective effect of saliva

A

damages bacterial cell wall to disable bacteria and viruses

27
Q

lysozyme

A

antibacterial salivary enzyme that damages bacterial cell wall

28
Q

salivary immunoglobulins

A

disable bacteria and viruses

29
Q

bolus

A

crushed foods and salivary juices including enzymes

30
Q

esophagus

A

fibromuscular tube to propel bolus from mouth to stomach via peristalsis

31
Q

esophageal sphincter

A

circular localization of ring-shaped muscle

uses close-open motions by the skeletal muscle (volunatary control)

32
Q

importance of motility

A
  1. moves food from mouth to anus
  2. mechanically mixes food to break it into uniformly small particles –> maximizes exposure of the particles to digestive enzymes via increased surface area
33
Q

how is GI motility determined/modified?

A

determined: properties of the GI smooth muscle

modified: chemical input from nerves, hormones, and paracrine signals

34
Q

slow wave potentials

A

cycles of smooth muscle contraction and relaxation that are associated with cycles of depolarization and repolarization; spontaneous depolarizations in GI smooth muscle

35
Q

where do slow wave potentials originate from?

A

network of cells called the interstitial cells of Caja aka ICCs

ICCs are pacemakers for slow wave activity in the GI tract

36
Q

the longer the duration of the slow wave…

A

the more action potentials fire and the greater the contraction force in the muscle

37
Q

the likelihood of a slow wave firing an action potential depends primarily on input from the…

A

enteric nervous system

38
Q

action potentials fire when…

A

slow wave potentials exceed threshold

39
Q

the force and duration of muscle contraction are directly related to…

A

the amplitude and frequency of action potentials

40
Q

peristalsis

A

progressive waves of contraction that move from one section of the GI tract to the next

circular muscles just behind the bolus contract to push the bolus forward into a receiving segment (where the circular muscles are relaxed), then this segment contracts and so on

41
Q

segmental contractions

A

mainly occur in the large and small intestines

short (1-5 cm) segments of intestine alternately contract and relax (circular muscles contact, longitudinal muscles relax)

this movement churns the intestinal contents to mix them and maintain its contact with the absorptive epithelium

42
Q

gastroesophageal reflux disease

A

GERD

occurs when stomach acid frequently flows back into the tube connecting your mouth and stomach

43
Q

stomach

A

breaks down bolus by chemical (gastric juice), biological (by pepsin hydrolysis), and mechanical (churning) functions

produces chyme (a mixture of degradation products of bolus including enzymes and gastric juices)

44
Q

long reflexes

A

originate outside the digestive system and includes feedforward reflexes called cephalic reflexes (originate in the brain)

begin with stimuli from sight, smell, sound, or thought of food –> prepare the digestive system for food that the brain is anticipating

45
Q

short reflexes

A

originates in the enteric nervous system within the wall of gut

46
Q

activation of g-cells and gastrin release is triggered by…

A

neural reflexes

47
Q

regulation/secretion in the stomach

A

activation of g-cells and gastrin release is triggered by neural reflexes

long reflexes: parasympathetic neurons from the vagus nerve stimulate g-cells to release gastrin into the blood

short reflexes: mediated by an ENS neurotransmitter called gastrin-releasing peptide (GRP); stimulated by the presence of amino acids and peptides in the stomach

48
Q

example of regulation/secretion in the stomach

A
  1. activation of g-cells through long and short reflexes
  2. g-cells release gastrin
  3. gastrin activates ECL cells
  4. ECL cells release histamine and increases mobility
  5. histamine activates parietal cells
  6. parietal cells release HCl
  7. HCl activates chief cells
  8. chief cells release pepsinogen
  9. pepsinogen is activated to pepsin by HCl

pepsinogen –> pepsin (via HCl)

49
Q

acid secretion in the stomach

A

parietal cells deep in the gastric glands secrete HCl into the stomach lumen

H+ from water inside the parietal cell is pumped into the stomach lumen by an H+-K+-ATPase (K+ enters the cell and Cl- follows H+ through open chloride channels)

50
Q

cytoplasmic pH of the parietal cells

A

7.2

51
Q

normal salivary flow rate

A

0.5 mL/min

52
Q

maximal secretion of saliva after rinsing with 0.5 M citric acid

A

7.4 mL/min

53
Q

bicarbonate effect in the stomach

A

bicarbonate is absorbed into the blood

buffering action makes blood leaving the stomach less acidic –> alkaline tide that can be measured as a meal is being digested

alkaline tide that occurs after a meal creates a temporary increase in pH

54
Q

bicarbonate secretion

A

carbonic anhydrase (CA) converts OH- and CO2 to bicarbonate ions

HCO3- ions are pumped out to ECF from cytoplasm of parietal cells by the basolateral Cl–HCO3 exchanger

Cl- are absorbed by Cl–HCO3- exchanger

55
Q

proteases for protein digestion

A

proteases are secreted as inactive proenzymes (zymogens) from epithelial cells in the stomach, intestine, and pancreas and are activated in the GI tract lumen

56
Q

protease types

A

endopeptidase + exopeptidase

UT BME 365S (3 decks)

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