Digestion 1: Function & Structure Flashcards
1
Q
What are the functions of the digestive system?
A
1) supply: water, electrolytes, nutrients to the body
2) motility: move materials from 1 part to another, remove waste
3) absorption
4) defense: prevent infection & autodigestion
2
Q
majority of the lymphoid tissues is found…
A
scattered throughout the Gi tract
3
Q
we have ___ and ____ at the back of the throat for defense
A
tonsils;
lymphoid tissues
4
Q
GALT
A
gut associated lymphoid tissues
5
Q
What structures make up the digestive system?
A
1) tubular GI tract: esophagus, stomach, small & large intestines
2) accessory organs: teeth, tongue, salivary glands, liver, gall bladder, pancrease
6
Q
Purpose of the mouth
A
receptacle for food
7
Q
what happens in the mouth?
A
- tongue: taste & guide food to pharynx
- teeth: mechanical digestion
- salivary amylase & salivary lipase (minimal digestion)
- forms bolus
8
Q
what secretes saliva?
A
salivary glands
9
Q
what does saliva contain?
A
- antibacterial factors
- mucus
- salivary amylase & salivary lipase
10
Q
pharynx is located…
A
at the back of the throat
11
Q
purpose of pharynx
A
push food into esophagus
12
Q
___ protects the larynx during swallowing
A
epiglottis
13
Q
the swallowing reflex begins at…
A
pharynx
14
Q
what feature of the pharynx makes swallowing very easy?
A
epithelial walls are closely adherent to the sides, making the lateral surface very flexible
15
Q
function of esophagus
A
moves food into stomach (peristalsis)
16
Q
which muscles are present in the esophagus?
A
beginning: striated muscles (voluntary)
end: smooth muscles (involuntary)
17
Q
sphincters of the esophagus
A
beginning: upper esophageal sphincter
end: lower esophageal sphincter
18
Q
sphincters of the esophagus control…
A
movement of materials through the esophagus
19
Q
esophagus passes through the ___. what are the implications?
A
thorax;
inhaling will suck food upwards -> this is prevented by the esophageal sphincters
20
Q
functions of the stomach
A
- temporarily stores ingested food
- secretes enzymes for digestion
- mechanical digestion
- slowly empties chyme into small intestines
21
Q
the entire GI tract has a layer of ____ and ___ muscle
A
circular;
longitudinal
22
Q
stomach muscles
A
- circular layer
- longitudinal layer
- oblique muscle layer
23
Q
exit of chyme into the small intestines is controlled by…
A
pyloric sphincter
24
Q
the pyloric sphincter checks …. before allowing food to exit the stomach
A
- pH
- liquid content
- size of particles
…in chyme
25
sections of the small intestines
1. duodenum
2. jejunum
3. ileum
26
how does food move forward in the small intestines?
- peristalsis
| - segmentation
27
main area of digestion and absorption?
small intestines
28
most of the enzymes secreted in the small intestines break down ____
macromolecules
29
absorption of nutrients occurs passively // actively
passively, once the micromolecules are small enough
30
amount of absorption depends on...
time that is spent in small intestines
31
digestion in the small intestines is aided by secretions of...
- liver (via gall bladder) → bile salts
| - pancreas → pancreatic enzymes, bicarb
32
liver is connected to gall bladder by...
common hepatic duct
33
gall bladder secretes things into the small intestines by...
common bile duct
34
entrance of material from gall bladder & pancreas to small intestines is controlled through...
sphincter of oddi
35
secretions of the pancreas & gall bladder is influenced by...
hormones
36
segments of the large intestines
1. ascending colon
2. transverse colon
3. descending colon
4. sigmoid colon
5. rectum
37
how is fecal matter moved in the large intestines?
- segmentation
| - mass movement
38
what happens in the large intestines?
- absorption of water & electrolytes
| - storage of fecal material for expulsion
39
entrance to the large intestine is controlled by...
illeocecal VALVE (not sphincter)
40
the small intestine is large in ____, while the large intestine is large in ____
length;
| diameter
41
how is excretion of poop controlled?
internal & external sphincters
42
muscles of the large intestine
- circular layer
- 1 strip of longitudinal muscle = taenia coli
All circular muscles gather along taenia coli, forming haustra (bulges)
43
bulges in the large intestine =
haustra
44
layers of the GI tract
1. mucosa
2. submucosa
3. muscularis externa
4. serosa
45
mucosa is made up of...
- epithelial walls
- lamina propria
- muscularis mucosae
46
lamida propria
thin layer of connective tissues that have fibroblas, myofibroblasts
47
muscularis mucosae
- waves the villi
| - helps more mucus come out
48
submucosa is made up of...
- Thick, dense layer of connective tissue
- Blood vessels
- Embedded glands
49
muscularis externa is made up of...
longitudinal & circular muscles
| - partial oblique muscle in stomach only
50
serosa layer is made up of...
mesentary system
51
2 components of the enteric nervous system
- submucosal plexus
| - myenteric plexus
52
mesentary system
double membrane tissue that surrounds the GI tract and attaches it to the rear wall of abdominal cavity
53
specialized cells of the mucosa
- epithelial cells / transport cells (parietal, goblet, paneth cells)
- enteroendocrine cells
- exocrine cells (goblet cells, paneth cells)
54
epithelial cells in the mucosa are responsible for...
- secretion: acid, bicarb
| - absorption: nutrients, water, vit
55
enteroendocrine cells
cells that secrete hormone in the GI tract
56
exocrine cells of the mucosa are responsible for...
secreting enzymes, mucus, anti-microbials, etc.
57
goblet cells
secrete mucus
58
paneth cells
secrete anti-microbial compounds
59
parietal cells
secrete HCl
60
where are paneth cells olcated?
at the bottom of the crypt
61
what cell is responsible for immunity/defense in the GI?
paneth cells
62
cells in the GI have a short // long lifespan?
short
63
what is used to replace cells in the GI? Where are they located?
stem cells;
| bottom of crypt → move to top of crypt as it differentiates
64
ENS
enteric nervous system
65
neurons in the ENS
- sensory
- interneuron
- parasympathetic ganglia
- sympathetic postganglionic fibres
66
myenteric plexus
regulates motility
67
myenteric plexus is also known as...
Auerbach's plexus
68
submucosal plexus is also known as...
Meissner's plexus
69
submucosal plexus
regulates secretion and absorption
70
2 main networks of the ENS
1. myenteric plexus
| 2. submucosal plexus
71
where is the myenteric plexus located?
between the circular & the longitudinal layer
72
where is the submucosal plexus located?
in the submucosa
73
How is the activity of the digestive system regulated?
short (ENS) & long (CNS) reflexes
74
receptors/sensors in the ENS
- mechanoreceptors: stretching of stomach
| - chemoreceptors: sense digestion products
75
how does the stomach send information to the CNS (long reflex)?
vagus nerve
76
response from long reflex
- enhance secretion & motility
| - change motility & secretion pattern
77
response from short reflex
- enhance secretion & motility
| - change motility & secretion pattern
78
2 ways the ENS/CNS can be stimulated
1. presence of food
| 2. cephalic phase of digestion (thinking/smelling/seeing food)
79
smelling food sends information to ___ receptors, which then sends info to ___
sensory;
| the cephalic brain
80
how does the cephalic brain send information to secretory cells of the stomach & small intestines?
via neurons of the myenteric & submucosal plexus
81
release of insulin & glucagon is controlled by the short // long reflex?
long
82
parasympathetic control is divided into...
1. cranial division (vagus nerve)
| 2. sacral division (Pelvis nerve)
83
PNS has what effect on digestion?
increase digestion
- increased motility & secretion
- relaxes sphincters
84
cranial division of PNS connects to...
1. esophagus
2. stomach
3. small intestines
85
sacral division of PNS connects to...
1. large intestines
| 2. rectum & anus
86
Steps of PSN control, starting with preganglion neurons and ending with NT secretion
1. pre-ganglion neurons synapse on ganglionic neurons in ENS
| 2. post-ganglionic fibres secrete ACh
87
distribution of SNS control
evenly distributed throughout GI
88
SNS post-ganglionic fibres release...
noradrenaline
89
SNS generally has what effect on digestion?
- inhibit gut movement
- reduce secretions
- cause sphincters to contract
90
SNS pre-ganglionic fibres release...
ACh
91
the SNS pre-ganglionic fibres connects to...
prevertibral ganglia
- celiac
- superior mesenteric
- inferior mesenteric
92
what changes in the GI regulate activity?
Local factors → secretory & enteroendocrine cells
- pH
- physical / chemical stimuli
Hormones → secretion & motility patterns
Neural mechanisms (myenteric/submucosal plexus)
- short reflex: input from stretch & chemoreceptors
- long reflex: input from CNS
93
first layer of control in the ENS is by...
local stimuli
94
sweet taste receptors activate ___, which increase of ___ (this increases glucose uptake from intestinal lumen)
G-proteins;
| incretins
95
GIP
glucose-dependent insulinotropic peptide
96
GLP-1
glucagon-like peptide
97
enterocytes
epithelial cells found in the GI tract
98
2 peptides which stimulates the release of insulin
1) GIP
| 2) GLP-1
99
Sweet taste receptor is...
dimer of T1R2 and T1R3
100
sweet taste receptors can be found...
- in the mouth
| - on enteroendocrine cells in the stomach
101
INCRETINS
general term for GI hormones that stimulate insulin release
102
incretins are secreted by ___ cells
enteroendocrine
103
Where does incretins act?
goes through circulatory system → pancrease
104
local effect of incretin
influence local enterocytes:
- more Na/glucose transporters
- more glucose uptake
- bring more glucose to enterocytes
105
___ circulation = blood flow from heart to digestive system
splanchnic circulation
106
what vessels bring blood to and from the digestive system?
- hepatic artery / hepatic vein
| - digestive tract arteries / hepatic portal vein
107
SPLANCHNIC
general term for internal orgains
108
PORTAL SYSTEM
circulatory system from 1 capillary bed to another
109
all blood from the digestive tract passes through the ____ before entering the ____ → ____
liver;
hepatic vein;
inferior vena cava
110
arteries leading to stomach
celiac artery (left & right gastric arteries)
111
arteries leading to small intestines
- superior mesenteric artery
- hepatic artery (→liver)
- small artery that goes to gall bladder
112
arteries leading to large intestines
superior & inferior mesenteric arteries
113
____ artery supplies blood to majority of the small & large intestines
superior mesenteric
114
___ arteries supply blood to most of the digestive system (though not a main force)
inferior mesenteric
115
capillaries in the villi is used for...
- gas exchange
- transport soluble nutrients
- transport water & electrolytes
116
what is used for fat absorption? where does it go?
central lacteal;
| lymphatic system
117
LACTEAL
projections of the lymph system
118
function of hepatocytes
- remove potentially harmful agents
| - filters & processes the blood
119
blood from the hepatic portain vein & hepatic artery pools in the ____ → _____ vein → drain into ______
sinusoid;
central;
hepatic vein
120
SINUSOIDS
slight enlargement of capillaries
121
bile exits hepatocytes through ___, which then drains into ___ and is stored in the gall bladder
bile canaliculi;
| bile ductules
122
functions of the liver
- glucose & fat metabolism
- protein synthesis
- hormone synthesis
- urea production
- detoxification
- storage
123
liver sends ... via the hepatic vein
metabolites to peripheral tissues
- glucose
- plasma proteins (albumin, clotting factors, angiotensionogen)
- urea
- vit D, somatomedins
- metabolites for excretion
124
liver sends ... via the bile duct
things secreted into duodenum
- bile salts
- bilirubin
- water, ions
- phospholipids
125
.... enters the liver via hepatic portal vein
things absorbed from GI tract
- bilirubin
- nutrients
- drugs
- foreign substances
126
... enters the liver via hepatic artery
metabolites & drugs from peripheral tissues
- bilirubin
- metabolites of hormones & drugs
- nutrients
