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A & P 2 > Lecture 13: Digestive system part 2 > Flashcards

Lecture 13: Digestive system part 2 Flashcards

1
Q

What are the 5 primary functions of the digestive system

A
  1. ingestion
  2. Propulsion
  3. Digestion
  4. Absorption
  5. Defecation
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2
Q

define ingestion

A

ingestion of food to the alimentary canal

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3
Q

define propulsion

A

movement of food along the canal

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4
Q

What are the 2 subcategories of propulsion

A
  1. voluntary : deglutition or swallowing (oropharynx)

2. Involuntary : Peristalsis (esophagus, stomach, small intestine, large intestine)

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5
Q

define digestion

A

reduction of food into particles to be assimilated

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6
Q

What are the 2 categories

A
  1. Mechanical degestion: physical alteration of food by chewing (mastication), churning (stomach), and segementation (small intestine)
  2. Chemical digestion: by catabolic enzymes
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7
Q

define absorption

A

passage of digested end-products of the alimentary canal to (active or passive transport)

  • cardiovascular system
  • Lymphatic system
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8
Q

define defecation

A

expulsion of non-digestible or non-absorbed material

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9
Q

What parts are involved in transforming food to a bolus that is swallowed (mastication)

A 
lips
cheeks
palate
tongue
salivary glands
gums
teeth
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10
Q

what controls mastication

A

voluntary + many stretching reflexes (mechanoreceptors)

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11
Q

What causes the propulsion of the bolus

A

deglutition (swallowing)

food goes from mouth -> oropharynx -> laryngopharynx ->oesophagus

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12
Q

what coordinates the propulsion / deglutition of the bolus

A

tongue, soft palate, pharynx, esophagus

  • 2 phases
    1. buccal
    2. pharyngeal-esophageal
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13
Q

What happens in the 1st phase of propulsion the Buccal (oral) phase

A
  • it is a voluntary action
  • bolus pushed by tongue against palate & towards the back of oral cavity up to oropharynx; upper esophageal sphincter contracted
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14
Q

What happens in th 2nd phase of propulsion the pharyngeal - esophageal phase

A
  • involuntary action
  • bolus in oropharynx stimulate mechanoreceptors
  • oropharynx sends an impulse to center of deglutition (medulla oblongata, inferior part of pons)
  • medulla sends impulse that provokes elevation of soft palate & uvula to close the nasopharynx & elevation of larynx that cause epiglottis to tip over the larynx (interrupt respiration)
  • bolus reaches esophagus (respiration restarts)
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15
Q

What is peristalsis

A

smooth muscle

  • wave-like ripple
  • stretch in tract causes reflex contraction of circular muscle -> forward movement
  • causes additional contractions
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16
Q

what is segmentation

A

smooth muscle

  • mixing movement
  • forward and backwards movement in single region
  • helps mix food and digestive fluids
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17
Q

when bolus mixes with gastric juices it turns to

A

chyme

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18
Q

what happens a few minutes after bolus enters stomach

A

mixing wave ( churning) which is specific peristaltic movement of stomach (involuntary-propulsion) every 15 - 20 seconds

19
Q

How does stomach empty chyme into small intestine

A

a bit of chye is pushed into duodenum via pyloric sphincter while rest returns into stomch (retropulsion)
-this cycle keeps repeating until stomach is empty

20
Q

Gastric motility: how long does it take to empty stomach and what controls it

A
  • takes ~ 2-6 hours

- controlled by hormonal and nervous mechanisms

21
Q

What are the hormonal mechanisms that control gastric motility

A
  • fats in duodenum stimulate the release of gastric inhibitory peptide (GIP)
  • which decreases peristalsis of gastric muscle and slows passage of chyme into duodenum
22
Q

what are the nervous mechanisms that control gastric motility

A
  • enterogastric reflex
  • receptors in duodenal mucosa are sensitive to presence of acid and distention
  • impulses over sensory and motor fibers in the vagus nerve cause a reflex inhibition of gastric peristalsis
  • increases in acid and distention in duodenum -> inhibitor of peristalsis -> decreased chyme entering duodenum
23
Q

Intestinal motility includes what 2 types of movement

A

peristalsis and segmentation

24
Q

What does segmentation in duodenum and upper jejunum do

A

mixes chyme w/ digestive juices frfom the pancreas, liver, and intestinal mucosa

25
Q

What helps move chyme from small intestine to large

A

rate of peristalsis picks up as chymes approaches end of jejunum; moving it through rest of s. intest into l. intest

26
Q

How long does it take chyme to move through small intestine

A

~ 5 hours

27
Q

What helps regulate and stimulate peristalsis in intestines

A
  • regulated in part by intrinsic stretch reflexes

- stimulated by cholecystokinin (CCK)

28
Q

What is chemical digestion

A

changes in chemical composition of food

29
Q

changes in chemical composition of food is from

A

hydrolysis (catabolism)

30
Q

what is the catalyst in chemical digestion

A

extracellular, organic (protein)

31
Q

what are the principles of enzyme action in chemical digestion

A
  • specific in their action
  • optimal function at specific pH
  • most catalyze a chem reaction in both directions
  • enzymes continually destroyed in body and must continually be synthesized
  • most digestive enzymes synthesized as inactive proenzymes (need another molecule to be activated)
32
Q

Enzymes are involved in the breakdown of (3)

A
  • carbohydrates
  • proteins
  • lipids
33
Q

what are carbohydrates

A

saccharide compouds (sugars)

34
Q

what forms disaccharides

A

polysaccharides are hydrolyzed by amylases (in saliva and from pancreas)

35
Q

what is final step of carbohydrate digestion after it is turned to disaccharides

A

final steps are catalyzed by sucrase, lactase and maltase (found in cell membrane of epithelial cells covering villi lining intestinal lumen)

36
Q

what are protein compounds composed of

A

twisted chains of amino acids

37
Q

stage 2 of protein digestion

A

proteases catalyze hydrolysis of proteins into intermediate compounds and finally amino acids

38
Q

stage 3 protein digestion

A

main proteases: pepsin in gastric juice, trypsin in pancreatic juice, peptidases in intestinal brush border

39
Q

how is fat digested

A
  • fats are insoluble in water
  • must be emulsified by bile in small intestine before being digested
  • pancreatic lipase is the main fat-digesting enzyme
40
Q

what does mucus do

A

lubricates food and, with water, facilitates mixing

41
Q

what does amylase do

A

an enzyme that begins digestion of starches

42
Q

salivary lipase

A

a small amount released in saliva

43
Q

what does sodium bicarbonate do in saliva

A

increases the pH for optimal amylase function

A & P 2 (13 decks)

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