Chapter 18 The Digestive System Flashcards
1
Q
function of the digestive system
A
processes food into molecular forms that are transferred into internal environment
2
Q
motility
A
movement of food through the gastrointestinal (GI) tract
3
Q
how is food transported through the gastroinstetinal tract
A
via ingestion, mastication, declutition, and contraction of smooth muscles
4
Q
secretion
A
release of exocrine and endocrine secretion into lumen (inside) of GI tract for digestion
5
Q
digestion
A
chemical/mechanical breakdown of food from macromolecules to smaller molecules,
6
Q
why are molecules breakdowned in digestion
A
for absorbtion
7
Q
absorbtion
A
transport of digested end products into blood/lymph
8
Q
storage and elimination
A
temporary storage followed by elimination of indigestible food molecules
9
Q
location of immune barrier
A
immune system cells
physical barrier
10
Q
location of majority of immune system cells
A
GI mucosa
11
Q
physical barrier
A
to pathological organisms and toxins
12
Q
location of immune system cells
A
in connective tissue outside of intestinal epithelium
13
Q
breakdown of carbohydrates, proteins and lipids
A
hydrolysis reactions (breakdown of substance due to reaction with water)
14
Q
structures
A
gastrointestinal (GI) tract/alimentary canal
accessory organs and tissue
15
Q
gastrointestinal (GI) tract/alimentary canal
A
mouth, pharynx, esophagus, stomach, small intestine, large intestine
appx. 30 ft. long
16
Q
accessory organs and tissue
A
teeth, tongue, salivary glands, liver, gallbladder, pancreas
17
Q
responsibility of accessory organs and tissue
A
secrete substance into the tract via connecting ducts
18
Q
secreted substances in the stomach
A
HCl
Pepsinogo
Mucus
Intrinsic factor
19
Q
secreted substances in the small intestine
A
bile
bicarbonate
enzymes
20
Q
location of digestion and absorbtion
A
long tube connected to external world at both ends
21
Q
layers/tunics of the gut wall
A
mucosa submucosa muscularis serose (from most inside to most outside)
22
Q
responsibility of mucosa
A
absorbtion and secretion
mucus secretion
23
Q
layers of mucosa
A
epthelium
lamina propria
muscularis mucosae
24
Q
what is the lamina propria connceted to
A
lymph nodules
25
muscularis mucosae
thin smooth muscle layer
| creates small folds (increase surface area)
26
submucosa
connective tissue, serves mucosa
| blood/lymph vessels
27
submucosal plexus
neuronal innervation (nervale Versorgung) for muscularis mucosae
28
responsibility of muscularis externa
segmental and peristalitic contraction to move food and pulverize and mix it with digestive enzymes
29
muscularis externa
inner circular layer of smooth muscle
| outer longitudinal layer of smooth muscle
30
myenteric plexus
in muscularis externa
| neurons for entire GI tract
31
serosa
connective tissze covered with epithelium
32
who increases the surface area for absorbtion of nutrients
villi
33
when does the villi increase the surface area
by projecting into the lumen of the small intestine
34
mastication
chewing of food in mouth
mix food with saliva
start of digestion
35
deglutition
swallowing
36
when does deglutition occur
when food or drink stimulate pressure receptors in pharynx
37
what happens when pressure recpetors in the pharynx are stimulated
afferent input to the medulla
| efferent output to muscles in pharynx and esophagus
38
what do muscle of moth and tongue creat when they mix food and saliva
bolus
39
what prevents food to enter the nasal passage
soft palate
40
what closes the opening of the larynx
glottis
41
what covers the glottis to prevent food to enter in the trachea
epiglottis
42
what moves food into the stomach in the esophagus
peristalsis
| =wavelike muscular contraction
43
esophagus
muscular tube
connects pharynx to stomach
lined with empithelium and skeletal and smooth muscle
44
what controls bolus to move into stomach and prevents movements back into esophagus
lower esophageal sphincter
45
stomach
further digestion to form bolus to chyme
stores food
kills bacteria
peristaltic waves to move chyme to small intestine
46
folds in inner surface of stocack
gastric rugae
47
who is responsible for the gastric motility within the stomach
smooth muscle
48
cell types in the gastric glands of the mucosa of the stomach
```
mucous neck cells
parietal cells
chief cells
enterochromaffin-like (ECL) cells
G cells
D cells
```
49
mucous neck cells
secrete mucus
50
parietal cells
secrete hydrochloric acid (HCl)
51
chief cells
secrete pepsinogen
52
G cells
secrete gastrine (hormone)
53
D cells
secrete somatostatin
54
what does the gastric mucosa also secrete
intrinsic factor
55
what regulates hunger and is secreted by the stomach
ghrelin
56
gastric juice
pH < 2
is acidic
secretion of gastric cells + water
activates pepsin (from pepsinogen)
57
what is hydrochloric acid (HCl) responsible for
acidic pH in the gastric lume
58
what does the acid prodcution by parietal cells depend on
generation of carbonic acid
59
what does the secretion of hydrogen ions into the stomach lumen depend on
primary active transport by H+/K+ ATPase pumps
60
molecule that secrets into lumen of stomach when bicarbonate secretes into bloodstream
Cl-
61
what is HCl secretion/inhibited by parietal cells stimulated by
secreted: gastrin, histamine, ACh
inhibited: somatostatin
62
stimulation of gastrin secretion
by presence of partially digested proteins in the stomach
63
what does mucus layer contain that protects stomach from acid and pepsin
bicarbonate
64
what does acidity (HCl) in the gastric lumen convert
pepsinogen to pepsin
65
small intestin
longest part of GI tract (3m)
| mucosa contains goblet cells
66
what do goblet cells in small intestine secrete
mucus
lymphocytes
lymphatic nodules
67
folds in mucosa in small intestine
villi
68
increase of surface area for food absorbtion
due to Microvilli or brush border in the villi
69
digestive enzymes in small intestine
embedded in microvilli
| stay attached to epithelial membrane while work on chyme
70
what gets digested in the small intestine
carbohydrates, lipis and proteins
71
absorbtion within the small intestine
carbohydrates, lipids, AAs, vitamines, minerals, ions, water, electrolytes and bile salt
72
brush border enzymes
embedded in plasma membrane of microvilli
| active site face cheyme in lumen
73
motility within small intestine
slow to ensure proper absorbtion of nutrients
74
main contraction in small intestine
segmentation
75
what controls segmentation in the small intestine
enteric nervous system
76
segmentation
simultanous contraction at different location
77
large intestine/colon
large diameter
no villi
no digestion
absorbtion of electrolytes water and vitamins
78
what does mucosa in the large intestine contain
mucus secreting goblet cells, lymphocytes and lymphatic nodules
79
primary activities in large intestine
active transport of sodium coupled with water
80
how much water enters Gastrointestinal tract?
1.5 L per day
81
amount of water secreted by Gastrointestinal tract into lumen
8-10 L
82
how much fluid is excreted in feces
< 200ml
83
how does water absorbtion work
active Na+ pumping into epthelial cells
create osmotic pressure gradient
water absorbed into ISF and bloodstream
84
defecation
waste product
occurs when rectal muscle contracts
internal and external sphincters relax
85
what helps to push feces from rectum through anal canal
contraction of abdominal and pelvic muscle
86
liver
```
bile production
detoxication of blood
carbohydrate metabolism
lipid metabolism
protein synthesis
```
87
liver cells
hepatocytes
88
what are hepatocytes seperated by
sinusoids
89
bloodflow in liver
blood enters through portal triad
hepatic sinusoids
leaves lobule through central vein
hepativ veins
90
amount of bile produced by the liver
250-1500ml daily
91
components of bile
```
bile pigment
bile saltss
lecithin
bicarbonate ions
cholesterol
trace metals
```
92
bile pigment
bilirubin (from breakdown of heme)
not water soluable
carried in blood
liver converts into water soluble form
93
bile salts
cholesterol based
form micellesin aqueous solution
most recirculate 6-10 times per day, rest excreted in feces
94
what allows breakdown of fat in chyme
fat enters micellesand their amphipathetic nature allows breakdown
95
emulsification
breakdown of fat by bile salts
96
bile pathway in liver
```
secreted by hepatocytes
bile caniculi
bile ducts
gallbladder
small intestine
```
97
what stimulates bile secretion into small intestine
cholecystokinin (CCK)
98
amount of reabsorbed cholesterol based bile salts
95% reused in liver
99
structure of bile salt
bile acid
glycine (AA)
taurine (AA)
has a polar and nonpolar end
100
endocrine functions of the pancreas
insulin, glucagon
cluster of cells
islets of Langerhans
secreted into blood
101
exocrine function of the pancreas
pancreatic juice
| secreted through pancreatic duct into duodenum of small intestine
102
pancreatic juice
bicarbonate and around 20 enzymes
103
amylase
```
enzyme in pancreatic juice
digests starch (Stärke)
```
104
trypsin
enzymes in pancreatic juice
| digests protein
105
lipase
enzyme in pancreatic juice
| digests triglycerides
106
what plays a major role in the prodcution of digestive enzymes
excocrine cells in the pancreas
107
regulation of digestive processes
hormonal and neural regulation
108
three phases of the digestive control
cephalic phase
gastric phase
intestinal phase
109
cephalic phase
secretion stimulated by sight, smell, taste, chewing
| first 30 min of meal
110
what does the vagus nerve stimulate during the cephalic phase
chief cells to secrete pepsinogen,
| gastric acid secretion by ECL cells stimulation that secrete histamin -> stimulates parietal cells to secrete HCl
111
gastric phase
initiated by arrival food in stomach
| causes distension, acidity, AAs, peptides
112
what causes AA and peptide in the gastric phase
stimulation of chief cells to secrete pepsinogen
| G cells to secrete gastrin -> secretion histamin from ECL cell -> stimulate HCL from parietal cells
113
Acidity in gastric phase
inhibits gastrin secretion
114
intestinal phase
inhibtion of gastric acidity and motility that small intestinehas time to absorb
115
what is the intestinal phase initiated by
distension, acidity, osmolarity & various digestive products like fat
116
what are inhibitory hormones secreted by
small intestine
117
regulation of intestinal function
paracrine regulation
intestinal reflexes
enteric nervous system
118
paracrine regulation
paracrine substances affect contraction, absorbtion and secretion
119
intestinal reflexes
various reflexes affect motility
120
enteric nervous system
division of autonomic NS
| sensory neurons, interneurons, autonomic motor neurons, glial cells
121
networks that connect neurons and glial cells in enteric NS
```
myenteric plexus (in entire GI)
Submucosal plexus (just in SI and LI)
```
122
what does chyme stimulate
interneurons -> motor neurons -> smooth muscle contraction
123
regulation of pancreatic juice secretion
chyme in SI stimulates gastric ohase and reflex secretion of pancreatic juice and bile
124
cholecystokinin (CCK)
secreted by duodenum
| stimulates secretion of pancreatic juice enzymes
125
secretin
secreted by duodenum
| stimulates bicarbonate and water secretion from pancreas
126
what causes CCK secretion
protein and fat in chayme
127
what causes secrretin secretion
reduced pH in SI
128
what increases bile volume
bicarbonate secreted by liver
129
what causes higher bile delivery into duodenum
contraction of gallbladder
130
what stimulates the liver to secrete bile
bile arriving in duodenum
| secretin and CCK
131
daily intake of carbohydrates
250-300g
132
salivary amylase (enzyme)
digests carbs from mouth to stomach
| small % of carb digestion
133
pancreatic amylase
in SI
| most of carb digestion
134
brush border amylases
in SI
135
constructions in which pancreatic analyses form carbs
oligosaccharide
maltriose
maltose
136
absorbition of carbs
monosaccharides transported into epithelial cells of SI
fasiliated diffusion into ISF
after into capillary
137
daily protein intake
60-90g
138
what does pepsin do to protein
forms it to short-chain polypeptides
139
which pancreatic juice enzymes digest polypeptides into free AAs
trypsin, chymotrypsin, elastase, carboxypeptidase
140
what brush border enzymedigest polypeptides into free AAs
aminopeptidase
141
what happens to free AAs
enter epithelial cells
| secreted into ISF - capillaries
142
where does breakdown of proteins occur
SI
143
daily lipid intake
70-100 g
144
digestion of lipids
by pancreatic lipase in SI aided by pancreatic colipase
| lipids in chyme stimulate secretion of bile -> emulsification of lipids
145
phospholipase A
digests phospholipids into fatty acids and lysolecithin
146
what is released with the digestion of triglycerides
fatty acids and monoglycerides - bind to micelles of bile salts
147
what happens to fatty acids, monoglycerides and lysolecithin
leave micelles, enter epithelial cells of SI
form chylomicrons
secreted by exocytosis into blood
