Human Physiology Ch 18

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The Digestive System
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1

function of GI tract

transfer nutrients, water, and electrolytes from ingested food into bodys internal environment

2

four functions of digestive system

motility

secretion

digestion

absorption

3

motility

movement of food through body

4

chemical digestion is done by what?

enzymes

5

swallowing is initiated by what?

involuntarily when bolus is pushed to back of mouth

6

what is vomitting?

reverse peristalsis

7

what is the pH of the stomach

ph of 2

8

what pushes food through esophagus?

peristalsis

9

what does the esophogus secrete?

mucus

10

what is the bottom sphincter of the esophagus?

esophageal sphincter

11

function of the stomach

store, mix, and prepare food for digestion

12

4 stomach secretions

HCl

mucus

pepsin

gastrin

13

sphincter at bottom of stomach

pyloric sphincter

14

what is chyme?

liqufied mixture of food

15

what does the pyloric sphincter do?

controls the release of chyme into small intestine

16

what is pepsin used for?

protein digestion

17

what does salivary amylase do?

enzyme

breaksdown carbohydrates

18

which has a bigger influence on saliva secretion? sympathetics or parasympathetics?

parasympathetics

19

what do parietal cells secrete into stomach?

HCl

20

what do chief cells secrete into stomach?

pepsinogen

21

what is pepsinogen converted into?

pepsin

22

stomach factor that plays greatest role in gastric emptying

amount of chyme in stomach

23

what does fat do to gastric emptying?

delays

24

what does acid do to gastric emptying?

delays it until it is neutralized

25

if small intestine is distended too much what happens?

gastric emptying is inhibited

26

how does SI handle stomach acid?

neutralizes it with bicarbonate

27

what is the site of most diegstion and absorption of nutrients?

small intestine

28

three segments of small intestine

duodenum

jejunum

ileum

29

what is segmentation and where does it occur?

small intestines

squeezing that mixes chyme and exposes it to more enzymes

30

what purpose do villi and microvilli serve in SI?

increase surface area to maximize absorption

31

where are water soluble particles absorbed? (proteins and carbs)

in capillaries in villi

32

where are fat soluble particles absorbed? (fats lipids)

in lacteals

33

where are enzymes in the small intestines?

within the brush border membrane of epithelial cells

34

what enzymes are in the brush border membrane of epithelial cells of the SI

peptidases

disaccharidases

35

do SI secretions contain enzymes?

no

36

where is fat digested?

lumen of small intestine

37

what enzyme digests fat?

pancreatic lipase

38

functions of the large intestine

absorb water and electrolytes

vitamin synthesis

formation and storage of fecal matter

39

sections of the large intestine

colon

cecum

appendix

rectum

illiocecal sphincter

40

how is the large intestine different than the small intestine?

no digestive enzymes

no villi

no hormones

not tightly coiled

intestinal microflora (bacteria)

41

how long does it take the stomach to empty?

4-5 hours

42

how long does it take for food to transit through the colon

30-40 hours

43

accessory organs of the GI tract

pancreas

liver

gall bladder

44

endocrine function of pancreas

secrete insulin and glucagon

45

exocrine function of pancreas

secrete pancreatic juices

46

pancreatic juices

amylase

lipase

proteases

bicarbonate

47

what is a portal blood supply

capillary-vein-capillary

48

which organ is the largest and most important in metabolism?

liver

49

functions of liver

produces plasma protein

removes bilirubin

manufactures bile salts

alcohol metabolism

stores nutrients

removes and degrades toxins

50

why is stool brown?

due to liver removing bilirubin

51

where is bile made?

liver

52

where is bile stored and concentrated?

gall bladder

53

where does bile go once it leaves the gall bladder?

small intestine

54

what are bile salts?

derivatives from cholesterol

55

function of bile

fat emulsifier

56

where does bile go after digestion?

reabsorbed into blod

57

what are mycells?

smaller particles for lipase to breakdown

58

what is digestive motility and secretion regulated by?

intraluminal content

autonomous smooth muscle function

intrinsic nerve plexuses

extrinsic nerves-parasympathetics

GI hormones

59

luminal stimuli

mechanoreceptors

osmoreceptors

chemoreceptors

60

gastrin

secreted by stomach in presence of protein

increases HCl

61

CCK

secreted by small intestine in the presence of fat

decreases motility

62

GIP

secreted by small intestine in presence of glucose

increase insulin

63

secretrin

secreted by small intestine in presence of AA

increase HCO3- from pancreas, which decreases motility

64

phases of gastric secretion

cephalic phase

gastric phase

intestinal phase

65

cephalic phase

initiated when receptors in head stimulated by senses (smell/taste/hear bacon)

66

gastric phase

begins when food reaches stomach

presence of protein increases gastric secretions

67

intestinal phase

initiated by stimuli in intestinal tract (distension, acidity, etc)

68

amylase breaks down starches and forms it into what?

glucose

69

protein is broken down into what?

amino acids

70

where do amino acids go?

hepatic portal vein

71

fat digestion

reassembled as triglycerides, then chylomicron, then lipoproteins

72

where do lipoproteins go?

into lacteals in small intestine then into circulation

73

what regulates hunger?

hypothalamus

74

function of leptin

long term regulator

inhibits hunger

75

ghrelin function

increase hunger

76

PYY function

inhibits hunger

77

CCK

inhibits hunger

78

insulin function

inhibits hunger

long term regulator

79

3 components of energy expenditure

basal metabolic rate

thermic effect of food

thermic effect of exercise

80

what component of energy expenditure is most variable?

thermic effect of food

81

BMR % of energy expenditure

50-70%

82

TEF % of energy expenditure

10%

83

TEE % of energy expenditure

30-35%