The Digestive System Part 2 Flashcards
1
Q
*Label this diagram of the stomach
A
there
2
Q
what areas of the stomach secrete
A
the fundus, the body and the antrum
3
Q
what type of mucosa does the body of the stomach contain
A
oxyntic mucosa
4
Q
what type of glands does the antrum contain
A
the pyloric glands
5
Q
what are the two sphincters present in the stomach called
A
the gastroeosophageal and the pyloric
6
Q
what does the luminal surface of the stomach have
A
deep folds
7
Q
where does a peristaltic contraction originate and to where does it go towards
A
a peristaltic contraction originates in the upper fundus and sweeps down towards the pyloric sphincter
8
Q
where does the peristaltic contraction become vigorous
A
the contraction becomes more vigorous as it reaches the thick muscles antrum
9
Q
what is the function of the strong antral peristaltic contraction
A
it propels the chyme forward
10
Q
what two types of contraction occur in the stomach
A
regular peristaltic contractions - ber. strong peristaltic contractions - antrum
11
Q
what does ber stand for
A
basal electrical rhythm
12
Q
list three functions of the stomach
A
stores ingested food until emptied into the small intestine, secretes hcl and enzymes, converts contents into chyme
13
Q
what is the mucosal lining of the stomach divided into
A
the oxyntic mucosa and the pylorid gland area based on the differences in glandular secretion
14
Q
*label this diagram of the excocrine secretory cells
A
there
15
Q
what is an exocrine gland
A
a gland that secretes its products into ducts
16
Q
what is the function of the mucous cells present lining the gastric pits and the entrance of the glands
A
they secrete a thin, watery mucus - alkaline mucous
17
Q
what is the function of the mucous cells when secreting the alkaline mucous
A
a protective function
18
Q
what is the stimulus for the mucous cells to begin secreting alkaline mucous
A
a mechanical stimulation
19
Q
what do chief cells release
A
pepsinogen
20
Q
what is the function of the pepsinogen that the chief cells release
A
once the pepsinogen is activated, it digests protein
21
Q
what is the stimulus for the cheif cells to release the pepsinogen
A
acetylcholine and gastrin
22
Q
what do the parietal cells secrete
A
they secrete hcl and intrinsic factor
23
Q
what stimulates the parietal cells to secrete hcl
A
acetylcholine, gastrin and histamine
24
Q
what is the function of intrinsic factor
A
to absorb vitamin b12
25
what do exocrine secretions collectively make up
gastric digestive juice
26
what are the three endocrine/paracrine secretory cells
enterochromaffin-like cells (ecl cells), g cells and d cells
27
what is the function of enterchromaffin-like cells
to release histamine
28
what is the stimulus for ecl cells to release histamine
acetylcholine and gastrin
29
what is the function of the histamine that is secreted by the ecl cells
to stimulate the parietal cells
30
what do g cells release
they release gastrin
31
what is the stimulus for the g cells to produce gastrin
protein products and acetylcholine
32
what is the function of the gastrin produced by the g cells
to stimulate the perietal/chief/ecl cells
33
what do the d cells produce
they produce somatostatin
34
what is the stimulus for the d cells to produce somatostatin
acid
35
what is the function of the d cells producing somatostatin
to inhibit parietal/g/ecl cells
36
are enterochromaffin-like ecl cells stimulatory or inhibitory
they are stimulatory
37
are g cells stimulatory or inhibitory
they are stimulatory
38
are d cells stimulatory or inhibitory
they are inhibitory
39
what are the two functions of the peristaltic contractions
mixing of the gastric contents and the driving force for gastric emptying
40
The intensity of an- tral peristalsis can vary markedly under the influence of differ- ent signals from what
both the stomach and duodenum; thus, gastric emptying is regulated by both gastric and duodenal factors
41
what factors of the stomach increase the rate of motility and emptying of the gastric contents
volume of chyme, fluidity of chyme and distension of stomach
42
what factors of the duodenum decrease the rate of motility and emptying of the gastric contents
fat, acid, hypertonicity and distension
43
the presence of one or more stimuli in the duodenum activates appropriate duodenal receptors which trigger either one of two types of responses. what are the two types of responses
a hormonal or a neural response
44
the neural response is mediated through both the intrinsic nerve plexuses and the autonomic nerves, what are these reflexes collectively termed
the enterogastric reflex
45
what type of reflex is the intrinsic nerve
short reflex
46
what type of reflex are the autonomic nerves
long reflex
47
the hormonal response involves the release from the small intestine mucosa of several hormones collectively known as the
enterogastrones
48
where does the blood carry the enterogastrones and for what function
the blood carries these hormones to the stomach where they inhibit antral contractions to reduce gastric emptying
49
what are the two most important enterogastrones
secretin and cholecytokinin (cck)
50
what cells produce secretin
s cells
51
what cells produce cck
I cells
52
where are the s cells and I cells producing the enterogastrones found
in the duodenum and jejenum
53
what are two other factors which may impact on gastric motility and emptying
emotion and intense pain
54
what effect does emotion have on gastric motility and emptying
emotion alters the ans balance, it stimulates/inhibits motility and emptying
55
what affect does intense pain have on gastric motility and emptying
intense pain increases the sympathetic activity, decreasing the motility and emptying
56
what three regions make up the small intestine
the duodenum, the jejunum and the ileum
57
how would you describe the small intestine
as a coiled hollow tube roughly 8-10feet long
58
what is the small intestine the primary site of
the primary site of digestion and absorption
59
what three specialisations increase the absorptive surface of the small intestine
circular folds, villus and microvilli
60
the circular folds of the small intestine increase the absoptive surface by how much
3-fold
61
the villus of the small intestine increase the absorptive surface area by how much
10 fold
62
list four features of the villus in the small intestine
epithelial cells cover the surface. they have a connective tissue core. there is a capillary network. there is a terminal lymphatic vessel
63
what do the microvilli form
a brush border
64
by how much do the microvilli increase the absorptive surface of the small intestine
20 fold
65
the microvilli of the small intestine have membrane bound enzymes, list three
enterokinases, disaccaridases and aminopeptidases
66
the surface modifications of the small intestine - the circular folds, the villi and the microvilli - altogether increase the overall absorptive surface area by how much
600 fold
67
what are the three secretions into the duodenum
the intestinal juice, the pancreatic juice and bile
68
roughly how much intestinal juice is secreted into the duodenum per day
1.5 litres per day
69
what cells secrete intestinal juice
exocrine cells in the small intestine mucosa
70
what do the exocrine cells in the small intestine mucosa secrete which makes up the intestinal juice
aqueous salt and mucus secretion
71
what is the aqueous salt and mucus secretion secreted by the exocrine cells in the small intestine making up the intestinal juice called
the succus entericus
72
roughly how much pancreatic juice is secreted daily
1-2 litres a day
73
what two cells are involved in secretions making up the pancreatic juice
acinar cells and duct cells
74
what do the acinar cells release
pancreatic enzymes that digest all three food stuffs
75
what are the three pancreatic enzymes that the acinar cells secrete
pancreatic proteolytic enzymes, pancreatic amylase and pancreatic lipase
76
give an example of a pancreatic proteolytic enzyme released by acina cells
trypsinogen
77
what do proteolytic enzymes digest
protein
78
what do amylase enzymes digest
carbohydrate
79
what do pancreatic lipase digest
fat
80
what do the duct cells of the pancreas secrete
aqueous alkaline solution
81
what is the aqeuous alkaline solution secreted by the duct cells rich in
NaHCO3
82
the pancreatic exocrine secretion is under hormonal control, what happens when there is acid in the duodenal lumen
it results in an increase release of secretin from the duodenal mucosa. the secretin is carried by the blood to the pancreatic duct. this releases in an increased secretion of aqueous NaHCO3 solution into the duodenal lumen
83
what is the function of the NaHCO3 being released into the duodenal lumen
to neutralise the acid in the duodenal lumen
84
when there are fat and protein products in the duodenal lumen, which cells secrete more substance and which substance do they secrete
i cells secrete more cck from the duodenal mucosa
85
when there is fat and protein in the duodenal lumen, more cck is carried by the blood to the pancreatic acinar cells, what happens next
an increased secretion of pancreatic digestive enzymes into the duodenal lumen takes place which digests the fat and protein products
86
roughly how much bile is secreted into the duodenum on a daily basis
250ml-1litre per day
87
where is bile synthesised and secreted from
liver
88
where is bile stored
in the gall bladder
89
what is the main function of bile salts
to aid in fat digestion and absorption
90
what are dietary carbohydrates converted into
monosaccharides
91
where does digestion of carbohydrates begin
in the mouth
92
what enzyme is present in the mouth for carbohydrate digestion
salivary amylase
93
what does salivary amylase cconvert glycogen and starch into in the mouth
oligosaccharides
94
what enzymes are present in the small intestine for the digestion of carbohydrates
pancreatic amylase and disaccharidases
95
what role do the disaccharidases have
they convert disaccharides into monosaccharides
96
what role does pancreatic amylase have
convert glycogen, oligosaccharides and starch into disaccharides
97
glucose and galactose are absorbed in the small intestine by what type of transport
secondary active transport in which symport carriers such as the sodium and glucose co transporter SGLT is involved
98
how do glucose and galactose leave the enterocyte
by facilitated diffusion through the glut-2 passive transporter
99
how does fructose enter an enterocyte - by which type of transporter
glut-5 which is a passive transporter, so it enters by facilitated diffusion
100
how does fructose leave an enterocyte into the interstitial fluid
through the glut-2 passive transporter, so it exits by facilitated diffusion
101
how do carbohydrates enter the blood, in which form do they have to be broken down to
monosaccharides enter the blood
102
what must proteins be digested into
amino aids
103
digestion of proteins begins where
in the stomach
104
gastric pepsin in the stomach converts proteins into what
large polypeptides
105
what three types of enzymes do we have in the small intestine
pancreatic proteolytic enzymes, aminopeptidases and intracellular peptidases
106
what converts dipeptides to amino acids
dipeptidases
107
in protein absorption, small peptides are absorbed at the apical membrane by which two methods
symporter driven by H+ and Na+ - tertiary active transport
108
how do small peptides pass through the basolateral membrane
by facilitated diffusion which is passive
109
how do amino acids enter the enterocyte via the apical membrane
by na+ co transporters - symporters- secondary active transport
110
how do amino acids leave through the basolateral membrane
via a passive transporter, facilitated diffusion
111
what are proteins broken into to enter the blood capillary
amino acids
112
why are lipids a challenge to digest
lipids are hydrophobic so chemical and physical transformations must take place before they are digested and absorbed
113
why does the insolubility of fat in water present a special problem in digestion
because fat must be transferred from the watery chyme through the watery bodily fluids, even though fat is not water soluble
114
what is lipid converted into
monoglycerides and free fatty acids
115
what enzyme aids in digestion of lipids
pancreatic lipase
116
why are micelles key in the absorption of lipids
micelles are water-soluble particles that can carry the end products of fat digestion. the monoglycerides and free fatty acids passively diffuse from the micelles through the lipid component of the epithelial cell membranes to enter the interior of these cells.
117
bile secretion is modulated by what three regulatory systems
chemical regulation, hormonal regulation and neural regulation
118
what is used in the chemical regulation of the secretion of bile
bile salts
119
what hormone is used for the seretion of bile
secretin
120
what nerve is used in bile secretion
vagus nerve
121
what four substances make up the bile - (they form a aqeuous alkaline fluid)
bile salts, cholesterol, lecithin and bilirubin
122
what two parts make up bile salts
a lipid soluble part and a water soluble part
123
where do bile salts adsorb onto
the surface of fat droplets
124
the mixing movements of the small intestine result in the breaking up of
fat droplets
125
what prevents the bile salts and lipid from re-coalescing in the small intestine
the water soluble surface
126
what two components of bile are involved in the formation of micelles which are water soluble
bile salts and lecithin
127
describe the core of a micelle
hydrophobic - consisting of monoglycerides and free fatty acids
128
describe the shell of a micelle
hydrophillic
129
what is the function of the micelle
to transport h2o insoluble substances to the enterocytes
130
what does the lipid empulsion formed allow
This lipid emulsion prevents the fat droplets from coalescing and thereby increases the surface area available for attack by pancreatic lipase.
131
what is the function of pancreatic lipase
Lipase hydrolyzes the triglycerides into monoglycerides and free fatty acids.
132
what happens when a micelle approaches the apical membrane of a enterocyte
When a micelle approaches the absorptive epithelial surface, the monoglycerides and fatty acids leave the micelle and passively diffuse through the lipid bilayer of the luminal membranes.
133
what happens to the free fatty acids and the monoglycerides once they enter an enterocyte after diffusion across the apical membrane
The monoglycerides and free fatty acids are resyn- thesized into triglycerides inside the epithelial cells.
134
what happens to the triglycerides in the enterocyte
These triglycerides aggregate and are coated with a layer of lipoprotein from the endoplasmic reticulum to form water-soluble chylomicrons.
135
how do chylomicrons leave the basal membrane of the enterocyte
Chylomicrons are extruded through the basal membrane of the cells by exocytosis.
136
chylomicrons are unable to cross the basement membrane of the capillaries so where do they go instead
Chylomicrons are unable to cross the basement membrane of capillaries, so instead they enter the lymphatic vessels, the central lacteals.
