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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
PSNS activity
- increase activity - increase motility - increase secretions - relax sphincters
26
SNS activity
- decrease activity - decrease motility - decrease secretion - contract sphincters
27
phases of GI control
1. cephalic 2. gastric 3. intestinal
28
cephalic (feed-forward)
- sight, smell, taste, chewing - extrinsic nervous system - increase PSNS (via Vagus n.) - increase exocrine secretions in mouth and stomach - increase gastric motility
29
gastric (food in the stomach)
- 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
30
intestinal (food in small intestine)
- 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
31
mouth/pharynx/esophagus secretions
1. saliva (mouth) | 2. mucus
32
salvia
- about 1.5 L/day - activated during cephalic phase (both PSNS and SNS stimulate) - SNS = mucus - PSNS = watery
33
water secretion
moistens food, and dissolves molecules to facilitate chemoreception
34
mucus secretion
lubricates food and facilitates formation of a bolus for a swallowing
35
bicarbonate secretion
neutralizes acids in foods and bacterial metabolism
36
lysozyme secretion
kills bacteria to maintain heath of gums and teeth
37
amylase secretion
begins in the digestion of polysaccharides - salivary amylase
38
lipase secretion
begins the digestion of triglycerides - lingual lipase | - activated in the stomach
39
xerostomia
- no saliva | - difficulty chewing, speaking, swallowing, halitosis (bad breath), and tooth decay (but no trouble digesting)
40
mucus
- secreted through the tract (esophageal glands) | - forms slippery, protective surface, and buffers pH (bicarbonate)
41
digestion
minor digestion of carbohydrates (salivary amylase)
42
absorption
virtually no foods, some drugs like nitroglycerine
43
what is the main function of the mouth/pharynx/esophagus?
ingestion
44
chewing
- 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
45
swallowing
- deglutition - 100x / hour - 2400x / day
46
motility
- feeding - chewing (mastication) - swallowing (deglutition)
47
upper esophageal sphincter
anatomic sphincter
48
lower esophageal sphincter
true physiologic sphincter
49
swallowing process
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
50
gag reflex
initiated by object in throat that wasn't put there by swallowing
51
peristaltic wave
- takes about 5-9 seconds | - local stretch activates secondary peristaltic wave
52
how does fluid to the stomach
fluid gets to the stomach without peristalsis in 1-2 seconds via gravity
53
how does solid food get to the stomach
peristaltic is needed for solid food
54
LES sphincter
relaxes so the bolus can enter the stomach
55
weak LES means
acids reflux --> heart burn
56
stomach layers of muscle (superficial to deep)
1. longitudinal muscle 2. circular muscle 3. oblique muscle
57
oblique muscle
"churns"
58
gastric rugae
- increases surface area | - allows for distention
59
pyloric sphincter
controls movement of chyme into duodenum
60
where has the least amount of muscle in the stomach
the upper portion (cardiac region)
61
where has the most amount of muscle in the stomach
the lower portion (pyloric region) | - increase contraction strength
62
chyme
gastric juice + food
63
gastric juice
about 2 L / day
64
mucous cells
secrete mucus
65
parietal cell
secretes hydrochloric acid and intrinsic factor
66
chief cell
secretes pepsinogen
67
enteroendocrine cells
- secretes gastrin - histamine - somatostatin
68
HCl functions
1. dissolves food / denatures proteins (mechanical digestion) 2. kills bacteria 3. activates pepsin + lipase (lingual + gastric)
69
frilosec
proton pump inhibitor used to treat acid reflux and gastric ulcer
70
stomach lumen
excessive vomiting leads to metabolic alkalosis and K+ depletion
71
gastrin
- gastric hormone | - increase gastric secretions + motility (gastric phase)
72
ACh
neurotransmitter (PSNS)
73
histamine and somatostatin
paracrine agents
74
histamine
most important because it potentiates response of gastrin and ACh
75
pepsin + zantac
H2R (histamine receptor) blocks to treat acid reflux / gastric ulcer
76
cephalic phase pathway
parasympathetic nerves to enteric nervous system
77
cephalic phase result
increase HCl secretion
78
gastric phase pathways
long and short neural reflex and direct stimulation of gastrin secretion
79
gastric phase result
increase HCl secretion
80
intestinal phase pathways
long and short neural reflexes; secretin, CCK, and other duodenal hormones "enterogastric reflex"
81
intestinal phase result
decrease HCl secretion
82
pepsin
only works at low pH
83
intrinsic factor
binds to and facilitates absorption of vitamin B12 in the distal ileum
84
pernicious anemia
- no intrinsic factor | - vitamin B12 needed for red blood cell production
85
receptive relaxation
- 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
peristaltic waves
- 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
where is the electrical rhythm (slow waves) produced?
longitudinal smooth muscle | ---> frequency = 3/min
88
what does the neural/hormonal inputs modulate membrane potential
determine force | NOT frequency
89
gastric emptying stimulated by
- stomach distension - gastrin = gastric phase
90
gastric emptying inhibited by
"enterogastric reflex" = intestinal phase
91
hypertonicity
can be problem if no stomach = increased water = decreased blood volume = decreased blood pressure
92
types of digestion in stomach
1. mechanical | 2. chemical
93
mechanical digestion in stomach
- physical grindage - oblique layer of muscle - HCl
94
chemical digestion in stomach
- 15% protein (pepsin) | - 10-15% fat (gastric lipase) + lingual lipase
95
absorption in stomach
- not much: | - --> aspirin (and other weak acids)
96
small intestine contains
- duodenum - jejunum - ileum
97
duodenum
- first 10 inches | - receives secretions from liver and pancreas
98
small intestine
about 9-12 feet long
99
jejunum
- next 40% | - most Digestion and absorption occurs here
100
ileum
- last 50% - less muscle and fewer vessels - vitamin B12 absorption
101
intestinal secretions
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
endocrine cells of pancreas
insulin and glucagon into blood
103
exocrine cells
(digestive enzymes secreted) - pancreatic lipase - pancreatic amylase - proteases (ex: trypsin) - -> secreted as zymogens - CCK stimulates release
104
duct cells
(secrete bicarbonate) - neutralizes HCl from stomach - secretin stimulates release - mechanism of bicarbonate production = opposite of HCl
105
hepatopancreatic sphincter
regulates passage of secretions into duodenum
106
accessory duct
always open
107
what does bile contain
- bile salts and lecithin - cholesterol - bilirubin
108
bile salts and lecithin
- emulsify fats - reabsorbed in ileum - 500-1000 mL/day
109
cholesterol
excreted
110
bilirubin
- from RBC breakdown - excreted - metabolites makes urine yellow and feces brown
111
bile
- constantly secreted by liver | - stored and concentrated in gallbladder
112
secretin and CCK
- decrease gastric motility + secretions | - enterogastric reflex
113
CCK
- increase bile flow | - increase pancreatic enzymes
114
secretin
- increase bicarbonate production / secretion
115
what is the small intestine made for
absorption
116
what increases the surface area within the small intestine
- circular folds - villi - microvilli (brush border)
117
capillary network
nutrients absorbed
118
lacteal
lymphatic capillary = fats + fat soluble vitamins are absorbed in the lymph
119
digestion and absorption of carbs
- 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
digestion and absorption of proteins
- some digestion in stomach by pepsin - most by pancreatic proteases and brush boarder enzymes in small intestine - absorption in small intestine
121
micelles
keep most of the insoluble fat digestion products in small, soluble aggregates
122
digestion and absorption of fats
- 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
liver
- 'detoxifies' the blood and plays a major role in nutrient metabolism - NOT directly involved in digestion - play important role in metabolism
124
carboyhdrate metabolism
regulates blood glucose (glycogenesis, glycogenolysis, gluconeogenesis)
125
lipid metabolism/transport
- regulates fat metabolism and transport of fat / cholesterol to / from tissues - synthesis of lipoproteins (VLDL, LDL, HDL)
126
fluid into tract
- 8-9 L/day | - 7 L from secretions
127
fluid absorbed
- 99% | - 80% in small intestine via osmosis
128
how many GI cells per day?
+17 billion cells / day | --> entire epithelium replaced every 8 days
129
motility in small intestine
1. segmentation | 2. peristalsis
130
segmentation
- 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
small intestine peristalsis
- 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
large intestine
- about 4 ft long | - less SA and no villi
133
large intestine function
- temporary storage and concentration of undigested material - reclaim more water
134
large intestine secretions
- protective alkaline mucus - bicarbonate - K+ ions
135
large intestine digestion
bacterial digestion of complex polysaccharides (fiber)
136
large intestine absorption
- Na+ (water follows) - product of bacterial metabolism - -> vitamins (B5, B7, K), fatty acids, sugars
137
large intestine motility types
1. segmentation (haustration) 2. mass movements 3. defecation
138
haustration
- segmentation | - about every 30 min
139
mass movements
- gastrin stimulates (gastrocolic reflex) - long-range, rapid movements that occur during a new meal - pack the rectum and stimulate the defection reflex
140
rectal stretch
(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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