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BPK 205 > GI tract > Flashcards

GI tract Flashcards

1
Q

main role of the gastrointestinal tract

A

transfer nutrients and water from food into the body

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2
Q

what environment is the lumen a part of

A

external

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3
Q

name the order of organs in GI tract

A

oral cavity
esophagus
stomach
small intestine
large intestine
rectum

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4
Q

order of the accessory glands

A

salivary glands
liver
gall bladder
pancreas

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5
Q

liver

A

makes vile for digestion

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6
Q

gall bladder

A

stores and concentrates vile

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7
Q

pancreas

A

enzymes, dumps them into small intestine
chemical digestion

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8
Q

oral cavity

A

mechanical and chemical digestion

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9
Q

esophagus

A

passage to the stomach
transport tube, perystalsis

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10
Q

stomach

A

continued digestion,
mechanical (muscular contractions of wall)
chemical

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11
Q

small intestine

A

duodenumm(bulk of chemical digestion and reabsorption), jejunum, ileum

where most digestion and reabsorption happens

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12
Q

large intestine

A

final balance of salt and water
colon absorbs water and electrolytes; production of feces

rectum holds feces until defecation throguh anus

supports an environment that facilitate colonization by healthy bacteria

digests bacteria

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13
Q

order of sphincters of GI tract

A
  1. upper espophageal sphincter
  2. lower esophageal
  3. pyloric
  4. ileocecal
  5. internal anal (no control, smooth muscle), external anal (voluntary, skeletal muscle)
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14
Q

sphincters

A

seperate compartments
rings of smooth muscle
tonically contracted, relaxations allows food to pass
serve as one way valves

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15
Q

Name the order of walls of the GI tract tissue

A
  1. mucosa
  2. submucosa
  3. muscularis externa (circular muscle, longitudinal muscle)
  4. serosa
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16
Q

epithelium of mucosa

A

epithelium:
lines the lumen of the GI tract
single layer of epithelial cells
transporting cells (will have transporters and channels. water, ions, digestive products)
secretory cells (enzymes, mucus, hormones)
stem cells (undifferentiated epithelial cells that can replace the cells face the external environment that are short lived)

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16
Q

mucosa

A

brings nutrients into the body, innermost layer

epithelium
lamina propria
muscularis mucosae

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17
Q

lamina propria of mucosa

A

loose connective tissue
contains glands, lymph vessels, blood supply, nerve fibers

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18
Q

muscularis mucosae of mucosa

A

does not contribute to gastro contraction
adjuster or SA
thin layer of smooth muscle separates muscosa from submucosa
can contract to alter the SA of the mucosa for absorption

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19
Q

submucosa

A

made of loose connective tissue
has nerve trunks, blood supply (larger blood vessels) and lymph vessels
intestine has submucosal plexus (network of neurons regulating gut function)

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20
Q

muscularis externa

A

2 layers of smooth muscle cells
inner circular layers (constrict lumen)
outer longitudinal layers (shorten tract)
stomach has additional oblique layer just below submucosa
the myentric plexus ( another part of the enteric nervous system) located between the two muscle layers

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21
Q

serosa

A

suspends abdominal organs
outer covering of the entire GI tract and is continuous with peritoneal membrane that lines the abdominal cavity
made of secretory epithelium and connective tissue layers. lubricates, protects, suspends

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22
Q

secretion

A

movement of material from cells into lumen or ecf

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23
Q

digestion

A

chemical ad mechanical breakdown of food into absorbable units

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24
Q

absorption

A

movement of material from GI lumen to ECF
ree fatty acids, ions, water

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25
Q

motility

A

perastilus, segmental
movement of material through the GI ract as a result of muscle contraction

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26
Q

perstalic contractions

A

propel content forwards
circular muscles contract just behind the bolus to push it forwards

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27
Q

segmental contractions

A

mixing contents to break up food and increase exposure to enzymes
short segments of intestine alternately contract and relax
back and forth

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28
Q

bolus

A

once we have swallowed food

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29
Q

chyme

A

just come from stomach
soupy mixture of partially digested food

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30
Q

what does the GI secrete

A

sodium
potassium
cloride
bicarbonate
H+
water
digestive enzymes
mucus

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31
Q

short reflexes

A

integrated in the enteric nervous system and occurs entirely in the gut wall
- sensory recepters send information to enteric nervous system via interneurons

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32
Q

long reflexes

A

integrated within CNS
may originate in or outside of the GI tract
feedforward and emotional reflexes are initiated and integrated entirely outside the GI tract. Called cephalic reflexes

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33
Q

GI peptides

A

may be secreted in both short and long reflexes, or independently
signaling molecules that alter GI secretion and motility and eating related behaviours

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34
Q

SNS response

A

inhibits GI motility and secretions

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35
Q

PNS response

A

stimulates GI motility and secretions

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36
Q

what are the 3 pairs of salivary glands

A

parotid
sublingual
submandibular

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37
Q

salivary secretions

A

under automatic control (mostly parsympathetic)

lubrication and moistening of food
solubilization of material for taste
initial digestion of starches (salivary amylase)
lingual lipase contributes minorly to lipid hydrolysis
antibacterial actions (lysozyme, immunoglobulins)

38
Q

lysozyme

A

antibacterial enzyme

39
Q

immunoglobulins

A

antibodies

40
Q

swallowing reflex

A
  1. tongue pushes against soft palate and back of mouth, triggering the swallowing reflex (we stop breathing momentarily (do not want bolus in trachea, automatic)
  2. breathing inhibited as the bolus passes through the airway. Upper esophageal sphincter relaxes
  3. food moves downward into the esophagus, propelled by peristaltic waves and aided by gravity. Gravity helps but is not essential
41
Q

epiglottis

A

shuts over top of trachea so food does not go down there

42
Q

gastric phase

A

digestion (mechanical and chemical)
- gastric contractions continue to break food up and help mix it with gastric acid and secretions for chemical digestions
- produces chyme

protection
- acidic environment destroys pathogens
- mucus and bicarbonate to protect itself - from gastric juice

storage
release of chyme into small intestine is regulated.
until its ready to be released to the next compartment
longer for proteins and fats, shorter for pure carbs

43
Q

gastric mucous cells

A

mucous and bicarbonate
bicarbonate is chemical barrier which fills mucous droplets
mucous is the physical barrier that form wall on inside of the stomach

44
Q

pepsinogen

A

is an inactive protease secreted by chief cells of the gastric glands

45
Q

pepsin

A

starts as pepsinogen then activated by H+ becomes pepsin

optimally active between between 1.8 - 3.5

chops up peptide bonds (protein needs to be denatured) then pepsin begins protein digestion by cleaving specific peptide bonds of polypeptides
- protein product entering small intestine is a mixture of intact protein, polypeptides and some free amino acids

46
Q

fats in gastric chemical digestion

A

minor 10% digested in stomach
gastric motility
gastric lipase

47
Q

gastric motility

A

forms an emulsion of lipids and gastric lipase

48
Q

gastric lipase

A

hydrolyzes triglycerides into monoglycerides and FFAs

49
Q

triglyceride

A

how we consume and store fats

50
Q

gastric chemical digestion of carbohydrase

A

none
salivary amylase is inactivated at low pH

51
Q

where are free fatty acids absorbed

A

duodenum (small intestine)

52
Q

what do mucous surface and neck cells secrete

A

mucus and bicarbonate

53
Q

what is the stimulus for mucus and bicarbonate release

A

mucus: tonic secretion (always happening, with irritation of mucosa
bicarbonate: secreted with mucus

54
Q

what is the function of mucus and bicarbonate secretion

A

mucus: physical barrier between lumen and epithelium
bicarbonate: buffers gastric acid to prevent damage to epithelium

55
Q

what do parietal cells secrete

A

gastric acid (HCl) pH 2

56
Q

what is the stimulus for parietal cell release

A

acetylcholine (PNS)

57
Q

function of gastric acid secretion

A

activates pepsin, denatures dietary protein so pepsin can chop it up, kills bacteria

58
Q

what do chief cells secrete

A

pepsin(ogen)
gastric lipase (10%)

59
Q

what is the stimulus for chief cell release

A

acetylcholine, acid secretion

60
Q

what is the function of pepsin and gastric lipase secretion

A

pepsin: digests proteins
gastic lipase: digests fats

61
Q

The main functions of the small intestinal phase

A

regulation of gastric emptying
secretions
digestion
absorption

62
Q

how does the small intestine regulate gastric emptying

A

chyme in the SI triggers feedback to regulate further release from the stomach

63
Q

what does the SI secrete

A

epithelial cells (all over GI tract): mucus, digestive (brush border made within SI), enzymes
pancreas: bicarbonate: buffer to neutralize acid; digestive enzymes (work at a higher pH)
liver and gall bladder: bile

64
Q

what does the SI digest

A

fats, carbs, proteins/peptides

65
Q

what does the SI absorb

A

nutrients, vitamins, ions, minerals, water

66
Q

enterocytes/transporting epithelium

A

in wall of SI
microvilli increase SA and create brush border
digestive enzymes on the brush border
nutrient reabsorption occurs along villi

67
Q

crypt epithelial cells

A

secretion of ions water and hormones
safe space, stem cells

68
Q

goblet cells

A

secrete mucus for protection and lubrication

69
Q

capillaries

A

transport absorbed nutrients

70
Q

lacteals

A

transports absorbed fats via lymphatic system
projection of lymphatic system

71
Q

exocrine pancreas

A

proteases, amylases and llipases

exocrine secretions travel into main pancreatic duct (dumps bicarbonate into it), then into common bile duct. release into the duodenum is controlled by the sphincter of oddi

72
Q

biliary secretions

A

triggered by lipids in small intestine

non-enzymatic solution of bile salts (amphipathic), bile pigments and cholesterol
bile is made in liver
between meals bile is diverted into gallbladded where is is concentrated and stored

bile salts help with digestion and absorption of fats

73
Q

what can carbs be absorbed as

A

monosaccharides (absorbable bits, individual sugar bits)
glucose, fructose, galactose - end product of carb digestion
absorbed by transporters (uniport or symport)

74
Q

oral phase of carb digestion

A

mechanical digestion by chewing
chemical digestion begins with salivary amylase

75
Q

gastric phase of carb digestion

A

mechanical digestion due to peristaltic contractions (mixing churning)
chemical digestion paused in stomach (too acidic) salivary amylase cannot work in acidic environment

76
Q

intestinal phase of carb digestion

A

most digestion occurs in SI
continued mechanical digestion (segmental contractions)
pancreatic amylase secreted into lumen of the duodenum (to make it smaller and smaller)
brush border enzymes on apical surface of epithelial cells in duodenum and jejunum - fine clipping (sucrase, maltase and lactase are brush border enzymes)

77
Q

oral phase of protein digestion

A

mechanical digestion only

78
Q

gastric phase of protein digestion

A

chemical protein digestion initiated in the stomach : HCl denatures protein; pepsin cleaves peptide bonds
mechanical digestion by peristaltic mixing/churning
results in a mixture of intact protein, large polypeptides and some free amino acids

79
Q

intestinal phase of protein digestion

A

mechanical digestion by segmental contractions
chemical cleavage by peptidases
pancreatic enzymes: endo- and exopeptidases (trypsin,chymotrypsin,carboxypeptidases)
brush border enzymes: exopeptidase (aminopeptidase

80
Q

products of protein digestion

A

di and tri peptides and free amino acides and some small peptides

81
Q

endopeptidases

A

cleave internal peptide bonds

82
Q

exopeptidases

A

cleave terminal peptide bonds

83
Q

dietary lipids

A

triglycerides, cholesterol, phospholipids, fatty acids

provide both an energy source and reserve

form hormones, parts of cell membranes, insulation and shock absorption, transport fat soluble vitamins and other compounds

84
Q

oral phase of fat digestion

A

mechanical digestion only, ligual lipase

85
Q

gastric phase of fat digestion

A

begin chemical digestion by gastric lipase, course emulsification bigger droplets become smaller

86
Q

intestinal phase of fat digestion

A

major chemical digestion by pancreatic lipase, bile salts, colipase

87
Q

what is the solution to lipids being hydrophobic

A

course emulsification - in the stomach by mixing (large fat droplets suspended in chyme)

associated with bile salts in small intestine. fine emulsification increases SA for digestion and eventually forms micellar solution

88
Q

what do bile salts do to lipids

A

first create a stable emulsion of lipid droplets in solution
- pancreatic lipase digest triglycerides with the help of colipase

eventually small discs called micelles are formed and brought close to enterocytes for absorption

89
Q

explain fat absorption

A
  1. bile salts from gall bladder coat fat droplets
  2. pancretic lipase and colipase break down fats (dependent on each other) into monogylcerides and fatty acids stored in micelles
    3a) monoglycerides and fatty acids move out of miclles and enter cells by diffusion
    3b)cholesterol is transported in cells
  3. absorbed fats combine with cholesterol and proteins in the intestinal cells to form chylomicrons
  4. chylomicrons are removed by the lymphatic system
90
Q

chylomiron

A

goes into lymph before circulation
large fat droplet, must be packed into secretory vesicles by golgi for exocytosis

91
Q

colonic microflora

A

bacterial ecosystem
could exten to brain health

helps with digesting dietary fiber
produces vitamin K (50% of total need)
limits growth and invasion of pathogenic microorganisms

92
Q

defecation

A

feces do not normally contain useful nutrient
- presence of nutrient in feces is a marker of intestinal dysfunction

made of undigestible material, dead bacteria and epithelial cells, biliary metabolites, H2O

93
Q

steatorrhea

A

undigested fat in feces

BPK 205 (14 decks)

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