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GI tract Flashcards

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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
absorption
movement of material from GI lumen to ECF ree fatty acids, ions, water
25
motility
perastilus, segmental movement of material through the GI ract as a result of muscle contraction
26
perstalic contractions
propel content forwards circular muscles contract just behind the bolus to push it forwards
27
segmental contractions
mixing contents to break up food and increase exposure to enzymes short segments of intestine alternately contract and relax back and forth
28
bolus
once we have swallowed food
29
chyme
just come from stomach soupy mixture of partially digested food
30
what does the GI secrete
sodium potassium cloride bicarbonate H+ water digestive enzymes mucus
31
short reflexes
integrated in the enteric nervous system and occurs entirely in the gut wall - sensory recepters send information to enteric nervous system via interneurons
32
long reflexes
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
33
GI peptides
may be secreted in both short and long reflexes, or independently signaling molecules that alter GI secretion and motility and eating related behaviours
34
SNS response
inhibits GI motility and secretions
35
PNS response
stimulates GI motility and secretions
36
what are the 3 pairs of salivary glands
parotid sublingual submandibular
37
salivary secretions
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
lysozyme
antibacterial enzyme
39
immunoglobulins
antibodies
40
swallowing reflex
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
epiglottis
shuts over top of trachea so food does not go down there
42
gastric phase
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
gastric mucous cells
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
pepsinogen
is an inactive protease secreted by chief cells of the gastric glands
45
pepsin
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
fats in gastric chemical digestion
minor 10% digested in stomach gastric motility gastric lipase
47
gastric motility
forms an emulsion of lipids and gastric lipase
48
gastric lipase
hydrolyzes triglycerides into monoglycerides and FFAs
49
triglyceride
how we consume and store fats
50
gastric chemical digestion of carbohydrase
none salivary amylase is inactivated at low pH
51
where are free fatty acids absorbed
duodenum (small intestine)
52
what do mucous surface and neck cells secrete
mucus and bicarbonate
53
what is the stimulus for mucus and bicarbonate release
mucus: tonic secretion (always happening, with irritation of mucosa bicarbonate: secreted with mucus
54
what is the function of mucus and bicarbonate secretion
mucus: physical barrier between lumen and epithelium bicarbonate: buffers gastric acid to prevent damage to epithelium
55
what do parietal cells secrete
gastric acid (HCl) pH 2
56
what is the stimulus for parietal cell release
acetylcholine (PNS)
57
function of gastric acid secretion
activates pepsin, denatures dietary protein so pepsin can chop it up, kills bacteria
58
what do chief cells secrete
pepsin(ogen) gastric lipase (10%)
59
what is the stimulus for chief cell release
acetylcholine, acid secretion
60
what is the function of pepsin and gastric lipase secretion
pepsin: digests proteins gastic lipase: digests fats
61
The main functions of the small intestinal phase
regulation of gastric emptying secretions digestion absorption
62
how does the small intestine regulate gastric emptying
chyme in the SI triggers feedback to regulate further release from the stomach
63
what does the SI secrete
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
what does the SI digest
fats, carbs, proteins/peptides
65
what does the SI absorb
nutrients, vitamins, ions, minerals, water
66
enterocytes/transporting epithelium
in wall of SI microvilli increase SA and create brush border digestive enzymes on the brush border nutrient reabsorption occurs along villi
67
crypt epithelial cells
secretion of ions water and hormones safe space, stem cells
68
goblet cells
secrete mucus for protection and lubrication
69
capillaries
transport absorbed nutrients
70
lacteals
transports absorbed fats via lymphatic system projection of lymphatic system
71
exocrine pancreas
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
biliary secretions
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
what can carbs be absorbed as
monosaccharides (absorbable bits, individual sugar bits) glucose, fructose, galactose - end product of carb digestion absorbed by transporters (uniport or symport)
74
oral phase of carb digestion
mechanical digestion by chewing chemical digestion begins with salivary amylase
75
gastric phase of carb digestion
mechanical digestion due to peristaltic contractions (mixing churning) chemical digestion paused in stomach (too acidic) salivary amylase cannot work in acidic environment
76
intestinal phase of carb digestion
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
oral phase of protein digestion
mechanical digestion only
78
gastric phase of protein digestion
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
intestinal phase of protein digestion
mechanical digestion by segmental contractions chemical cleavage by peptidases pancreatic enzymes: endo- and exopeptidases (trypsin,chymotrypsin,carboxypeptidases) brush border enzymes: exopeptidase (aminopeptidase
80
products of protein digestion
di and tri peptides and free amino acides and some small peptides
81
endopeptidases
cleave internal peptide bonds
82
exopeptidases
cleave terminal peptide bonds
83
dietary lipids
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
oral phase of fat digestion
mechanical digestion only, ligual lipase
85
gastric phase of fat digestion
begin chemical digestion by gastric lipase, course emulsification bigger droplets become smaller
86
intestinal phase of fat digestion
major chemical digestion by pancreatic lipase, bile salts, colipase
87
what is the solution to lipids being hydrophobic
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
what do bile salts do to lipids
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
explain fat absorption
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 4. absorbed fats combine with cholesterol and proteins in the intestinal cells to form chylomicrons 5. chylomicrons are removed by the lymphatic system
90
chylomiron
goes into lymph before circulation large fat droplet, must be packed into secretory vesicles by golgi for exocytosis
91
colonic microflora
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
defecation
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
steatorrhea
undigested fat in feces

BPK 205 (14 decks)

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