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Anatomy 403 > Digestive System > Flashcards

Digestive System Flashcards

1
Q

Digestive system

A

process ingested food into a form that the body can use

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2
Q

Use food for:

A
  • fuel
  • raw materials
  • essential nutrients (iron, etc)
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3
Q

basic processes

A
  1. motility
  2. secretion
  3. digestion
  4. absorption
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4
Q

motility

A

mixing/stirring and propulsion

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5
Q

secretion

A

exocrine (digestive juices) and endocrine (hormones)

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6
Q

digestion

A

mechanical (physical) and chemical (enzymes)

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7
Q

absorption

A

designed to maximize (not regulated)

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8
Q

carbohydrates

A
  • monosaccharides
  • –> glucose
  • –> fructose
  • –> galactose
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9
Q

proteins

A

amino acids

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10
Q

triglycerides

A

monoglyceride plus 2 free fatty acids

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11
Q

serosa

A

makes fluid to decrease friction

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12
Q

deepest muscle layer to superficial

A
  1. serosa
  2. muscularis externa
  3. submucosa
  4. mucosa
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13
Q

muscularis externa contains

A
  • circular muscle
  • myenteric plexus
    longitudinal muscle
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14
Q

circular muscle

A
  • narrowing motions

- mix contents

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15
Q

myenteric plexus

A

regulates motility

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16
Q

longitudinal muscle

A

shortening motions = peristalsis

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17
Q

submucosa contains

A
  • major blood and lymphatic vessels

- submucosal plexus

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18
Q

submucosal plexus

A

regulates secretion

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19
Q

mucosa contains

A
  • epithelium (superficial)
  • lamina propria
  • muscularis mucosa (deep)
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20
Q

mucosa

A
  • increase surface area

- rapidly dividing (constantly replaced)

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21
Q

gastrointestinal histology

A
  • high SA for absorption
  • many blood vessels to transport absorbed nutrients
  • highly innervated to regulate / coordinate = enteric nervous system
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22
Q

GI hormones

A
  • gastrin
  • CCK
  • secretin
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23
Q

intrinsic

A

enteric nervous system (within gut)

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24
Q

extrinsic

A

autonomic nervous system (increase / decrease function within GI tract)
ex: histamine, somatostatin

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25
Q

PSNS activity

A
  • increase activity
  • increase motility
  • increase secretions
  • relax sphincters
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26
Q

SNS activity

A
  • decrease activity
  • decrease motility
  • decrease secretion
  • contract sphincters
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27
Q

phases of GI control

A
  1. cephalic
  2. gastric
  3. intestinal
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28
Q

cephalic (feed-forward)

A
  • sight, smell, taste, chewing
  • extrinsic nervous system
  • increase PSNS (via Vagus n.)
  • increase exocrine secretions in mouth and stomach
  • increase gastric motility
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29
Q

gastric (food in the stomach)

A
  • stretch, acidity, amino acids/peptides
  • intrinsic and extrinsic nervous system
  • gastrin and histamine
  • increase PSNS + Enteric NS
  • increase gastrin + histamine
  • both = increased gastric secretions and increased motility
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30
Q

intestinal (food in small intestine)

A
  • stretch, acidity, osmolarity, digestive products
  • intrinsic and extrinsic nervous system
  • CCK secretion
  • “Enterogastric relfex”
  • increased secretion + increased CCK
  • –> decreased secretions
  • –> decreased motility
  • –> slows down stomach emptying to give duodenum time to work
  • increased SNS + decreased PSNS
  • –> increased secretions into the intestine
  • –> increase intestinal motility
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31
Q

mouth/pharynx/esophagus secretions

A
  1. saliva (mouth)

2. mucus

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32
Q

salvia

A
  • about 1.5 L/day
  • activated during cephalic phase (both PSNS and SNS stimulate)
  • SNS = mucus
  • PSNS = watery
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33
Q

water secretion

A

moistens food, and dissolves molecules to facilitate chemoreception

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34
Q

mucus secretion

A

lubricates food and facilitates formation of a bolus for a swallowing

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35
Q

bicarbonate secretion

A

neutralizes acids in foods and bacterial metabolism

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36
Q

lysozyme secretion

A

kills bacteria to maintain heath of gums and teeth

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37
Q

amylase secretion

A

begins in the digestion of polysaccharides - salivary amylase

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38
Q

lipase secretion

A

begins the digestion of triglycerides - lingual lipase

- activated in the stomach

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39
Q

xerostomia

A
  • no saliva

- difficulty chewing, speaking, swallowing, halitosis (bad breath), and tooth decay (but no trouble digesting)

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40
Q

mucus

A
  • secreted through the tract (esophageal glands)

- forms slippery, protective surface, and buffers pH (bicarbonate)

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41
Q

digestion

A

minor digestion of carbohydrates (salivary amylase)

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42
Q

absorption

A

virtually no foods, some drugs like nitroglycerine

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43
Q

what is the main function of the mouth/pharynx/esophagus?

A

ingestion

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44
Q

chewing

A
  • mastication
  • break-up food, increase surface area, mix with saliva, chemoreception (taste receptors)
  • voluntary (skeletal) but coordinated by pattern generator in brainstem
  • doesn’t affect rate of digestion –> mainly for taste and prevent choking
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45
Q

swallowing

A
  • deglutition
  • 100x / hour
  • 2400x / day
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46
Q

motility

A
  • feeding
  • chewing (mastication)
  • swallowing (deglutition)
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47
Q

upper esophageal sphincter

A

anatomic sphincter

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48
Q

lower esophageal sphincter

A

true physiologic sphincter

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49
Q

swallowing process

A
  1. begins with voluntary closing of lips and elevation of lips and elevation of the tongue becomes an irreversible reflex when bolus hits back on the oral cavity
  2. usual blocks nasal passage
  3. epiglottis down & glottis up and closed
  4. peristalsis
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50
Q

gag reflex

A

initiated by object in throat that wasn’t put there by swallowing

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51
Q

peristaltic wave

A
  • takes about 5-9 seconds

- local stretch activates secondary peristaltic wave

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52
Q

how does fluid to the stomach

A

fluid gets to the stomach without peristalsis in 1-2 seconds via gravity

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53
Q

how does solid food get to the stomach

A

peristaltic is needed for solid food

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54
Q

LES sphincter

A

relaxes so the bolus can enter the stomach

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55
Q

weak LES means

A

acids reflux –> heart burn

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56
Q

stomach layers of muscle (superficial to deep)

A
  1. longitudinal muscle
  2. circular muscle
  3. oblique muscle
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57
Q

oblique muscle

A

“churns”

58
Q

gastric rugae

A
  • increases surface area

- allows for distention

59
Q

pyloric sphincter

A

controls movement of chyme into duodenum

60
Q

where has the least amount of muscle in the stomach

A

the upper portion (cardiac region)

61
Q

where has the most amount of muscle in the stomach

A

the lower portion (pyloric region)

- increase contraction strength

62
Q

chyme

A

gastric juice + food

63
Q

gastric juice

A

about 2 L / day

64
Q

mucous cells

A

secrete mucus

65
Q

parietal cell

A

secretes hydrochloric acid and intrinsic factor

66
Q

chief cell

A

secretes pepsinogen

67
Q

enteroendocrine cells

A
  • secretes gastrin
  • histamine
  • somatostatin
68
Q

HCl functions

A
  1. dissolves food / denatures proteins (mechanical digestion)
  2. kills bacteria
  3. activates pepsin + lipase (lingual + gastric)
69
Q

frilosec

A

proton pump inhibitor used to treat acid reflux and gastric ulcer

70
Q

stomach lumen

A

excessive vomiting leads to metabolic alkalosis and K+ depletion

71
Q

gastrin

A
  • gastric hormone

- increase gastric secretions + motility (gastric phase)

72
Q

ACh

A

neurotransmitter (PSNS)

73
Q

histamine and somatostatin

A

paracrine agents

74
Q

histamine

A

most important because it potentiates response of gastrin and ACh

75
Q

pepsin + zantac

A

H2R (histamine receptor) blocks to treat acid reflux / gastric ulcer

76
Q

cephalic phase pathway

A

parasympathetic nerves to enteric nervous system

77
Q

cephalic phase result

A

increase HCl secretion

78
Q

gastric phase pathways

A

long and short neural reflex and direct stimulation of gastrin secretion

79
Q

gastric phase result

A

increase HCl secretion

80
Q

intestinal phase pathways

A

long and short neural reflexes; secretin, CCK, and other duodenal hormones
“enterogastric reflex”

81
Q

intestinal phase result

A

decrease HCl secretion

82
Q

pepsin

A

only works at low pH

83
Q

intrinsic factor

A

binds to and facilitates absorption of vitamin B12 in the distal ileum

84
Q

pernicious anemia

A
  • no intrinsic factor

- vitamin B12 needed for red blood cell production

85
Q

receptive relaxation

A
  • prepares the stomach to receive food
  • mediated by serotonin and nitric oxide and released from enteric neurons
  • storing “food” is a key function; contractions are weak in the fundus body
86
Q

peristaltic waves

A
  • waves are smooth muscle contraction mix and propel food
  • pyloric sphincter only allows small amount of chyme into duodenum after each wave
  • –> opening is size of tip of little finger
87
Q

where is the electrical rhythm (slow waves) produced?

A

longitudinal smooth muscle

—> frequency = 3/min

88
Q

what does the neural/hormonal inputs modulate membrane potential

A

determine force

NOT frequency

89
Q

gastric emptying stimulated by

A
  • stomach distension
  • gastrin
    = gastric phase
90
Q

gastric emptying inhibited by

A

“enterogastric reflex” = intestinal phase

91
Q

hypertonicity

A

can be problem if no stomach = increased water = decreased blood volume = decreased blood pressure

92
Q

types of digestion in stomach

A
  1. mechanical

2. chemical

93
Q

mechanical digestion in stomach

A
  • physical grindage
  • oblique layer of muscle
  • HCl
94
Q

chemical digestion in stomach

A
  • 15% protein (pepsin)

- 10-15% fat (gastric lipase) + lingual lipase

95
Q

absorption in stomach

A
  • not much:

- –> aspirin (and other weak acids)

96
Q

small intestine contains

A
  • duodenum
  • jejunum
  • ileum
97
Q

duodenum

A
  • first 10 inches

- receives secretions from liver and pancreas

98
Q

small intestine

A

about 9-12 feet long

99
Q

jejunum

A
  • next 40%

- most Digestion and absorption occurs here

100
Q

ileum

A
  • last 50%
  • less muscle and fewer vessels
  • vitamin B12 absorption
101
Q

intestinal secretions

A
  1. hormones: CCK, secretin
  2. mucus
  3. Na+, Cl-, bicarbonate –> water follows
  4. Pancreas:
    digestive enzymes –> (lipases, amylase, nucleases, proteases)
    Bicarbonate
  5. Liver: bile
102
Q

endocrine cells of pancreas

A

insulin and glucagon into blood

103
Q

exocrine cells

A

(digestive enzymes secreted)

  • pancreatic lipase
  • pancreatic amylase
  • proteases (ex: trypsin)
  • -> secreted as zymogens
  • CCK stimulates release
104
Q

duct cells

A

(secrete bicarbonate)
- neutralizes HCl from stomach

  • secretin stimulates release
  • mechanism of bicarbonate production = opposite of HCl
105
Q

hepatopancreatic sphincter

A

regulates passage of secretions into duodenum

106
Q

accessory duct

A

always open

107
Q

what does bile contain

A
  • bile salts and lecithin
  • cholesterol
  • bilirubin
108
Q

bile salts and lecithin

A
  • emulsify fats
  • reabsorbed in ileum
  • 500-1000 mL/day
109
Q

cholesterol

A

excreted

110
Q

bilirubin

A
  • from RBC breakdown
  • excreted
  • metabolites makes urine yellow and feces brown
111
Q

bile

A
  • constantly secreted by liver

- stored and concentrated in gallbladder

112
Q

secretin and CCK

A
  • decrease gastric motility + secretions

- enterogastric reflex

113
Q

CCK

A
  • increase bile flow

- increase pancreatic enzymes

114
Q

secretin

A
  • increase bicarbonate production / secretion
115
Q

what is the small intestine made for

A

absorption

116
Q

what increases the surface area within the small intestine

A
  • circular folds
  • villi
  • microvilli (brush border)
117
Q

capillary network

A

nutrients absorbed

118
Q

lacteal

A

lymphatic capillary = fats + fat soluble vitamins are absorbed in the lymph

119
Q

digestion and absorption of carbs

A
  • some digestion in mouth by salivary amylase
  • most by pancreatic amylase and brush boarder enzymes in small intestine
  • all (fructose, glucose, galactose) converted to glucose in the liver
  • absorption in the small intestine
120
Q

digestion and absorption of proteins

A
  • some digestion in stomach by pepsin
  • most by pancreatic proteases and brush boarder enzymes in small intestine
  • absorption in small intestine
121
Q

micelles

A

keep most of the insoluble fat digestion products in small, soluble aggregates

122
Q

digestion and absorption of fats

A
  • bile salts emulsify fat
  • pancreatic lipase digests fat
  • micelles are in equilibrium
  • fatty acids and monoglycerides diffuse accords the intestinal membrane
  • resynthesizes into triglycerides and packaged into chylomicrons fro transporting the lymph/blood
123
Q

liver

A
  • ‘detoxifies’ the blood and plays a major role in nutrient metabolism
  • NOT directly involved in digestion
  • play important role in metabolism
124
Q

carboyhdrate metabolism

A

regulates blood glucose (glycogenesis, glycogenolysis, gluconeogenesis)

125
Q

lipid metabolism/transport

A
  • regulates fat metabolism and transport of fat / cholesterol to / from tissues
  • synthesis of lipoproteins (VLDL, LDL, HDL)
126
Q

fluid into tract

A
  • 8-9 L/day

- 7 L from secretions

127
Q

fluid absorbed

A
  • 99%

- 80% in small intestine via osmosis

128
Q

how many GI cells per day?

A

+17 billion cells / day

–> entire epithelium replaced every 8 days

129
Q

motility in small intestine

A
  1. segmentation

2. peristalsis

130
Q

segmentation

A
  • during meal (when food is present)
  • basic electrical rhythm (slow waves) produced in circular smooth muscle
  • frequency:
    12/min –> duodenum
    9/min –> ileum
  • neural/hormonal inputs modulate membrane potential: determines force
131
Q

small intestine peristalsis

A
  • migrating myoelectric complex (MMC)
  • after a meal
  • before more “food” reaches small intestine
  • stops when food reaches stomach (receptive relaxation)
  • removes remaining food and prevents bacterial growth
  • “the intestinal housekeeper”
132
Q

large intestine

A
  • about 4 ft long

- less SA and no villi

133
Q

large intestine function

A
  • temporary storage and concentration of undigested material
  • reclaim more water
134
Q

large intestine secretions

A
  • protective alkaline mucus
  • bicarbonate
  • K+ ions
135
Q

large intestine digestion

A

bacterial digestion of complex polysaccharides (fiber)

136
Q

large intestine absorption

A
  • Na+ (water follows)
  • product of bacterial metabolism
  • -> vitamins (B5, B7, K), fatty acids, sugars
137
Q

large intestine motility types

A
  1. segmentation (haustration)
  2. mass movements
  3. defecation
138
Q

haustration

A
  • segmentation

- about every 30 min

139
Q

mass movements

A
  • gastrin stimulates (gastrocolic reflex)
  • long-range, rapid movements that occur during a new meal
  • pack the rectum and stimulate the defection reflex
140
Q

rectal stretch

A

(defecation)

  1. stimulates contraction of rectum
  2. relaxes the internal anal sphincter
  3. external anal sphincter (skeletal muscle)
    - –> voluntary relaxation when ready

Anatomy 403 (13 decks)

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