GI Theme 2 Flashcards
(172 cards)
1
Q
what is involved in chemical digestion in the mouth
A
a-amylase
- starch digestion at pH 7
-when bolus & enzyme hit pH 2.5 gastric juices hydrolysis will cease
lingual lipase
-breakdown of triglycerides into fatty acids and glycerol
2
Q
what is involved in mechanical digestion int eh mouth
A
breaks into pieces
mixes with saliva
3
Q
what are the function of the stomach
A
storage
digestion
protection
4
Q
how does the stomach have a protective fucntion
A
acids destroys bacteria and other pathogens (HCl)
5
Q
outline mechanical digestion in the stomach
A
gentle mixing waves
more vigorous waves
intense waves near the pylorus
with each wave a small amount of chyme enters the duodenum
6
Q
outline protein digestion in the stomach
A
HCl denatures protein molecules
HCl transforms pepsinogen into pepsin that breaks peptide bonds between certain amino acids
7
Q
outline fat digestion in the stomach
A
gastric lipase splits the triglycerides in milk fat
most effective at pH6 to 6
8
Q
what is the cytoplasmic pH of the parietal cells
A
7.2
9
Q
which cells secrete mucus and bicarbonate
A
mucus cells in the neck of gastric glands
10
Q
how does gastric mucous & bicarbonate provide protection
A
creates a barrier protecting stomach from autodigestion
mucus-physical barrier
bicarbonate- chemical barrier
11
Q
how are GI secretions regulated
A
Long cephalic reflexes
- CNS (feeds forward & emotional reflexes)
Short reflexes
-ENS (motility & secretion: enzymes and hormones)
12
Q
what is the enteric ns
A
subdivision of the peripheral ns controlling GI system
capable of autonomous functions
can recieve from the autonomic ns
13
Q
how are gastric secretions and motility regulated
A
CNS & ENS
- cephalic phase
- gastric phase
- intestinal phase
14
Q
what happens in the cephalic phase
A
“stomach getting ready”
- cerebral cortex stimulates parasympathetic ns
- vagus n increases stomach muscle and glandular activity
15
Q
what happens in the gastric phase
A
“stomach working”
- nervous control keeps stomach active
- endocrine influences over stomach activity
16
Q
what is the function of D-cells
A
decrease stomach acid production
17
Q
what happens in the intestinal phase
A
“stomach emptying”
- intestinal activity increased (duodenum)
- distension, fatty acids or sugar signal medulla
- hormonal influences
18
Q
what is the role of the sympathetic nervous system in the intestinal phase
A
slow stomach activity
19
Q
what does secretin do in the intestinal phase
A
decerases stomach secretions
20
Q
what does cholecystokinin (CCK) do in the intestinal phase
A
decreases stomach emptying
21
Q
what does gastric inhibitory peptides(GIP) do in the intestinal phase
A
decrease stomach secretions, motility and emptying
22
Q
what do D cells secrete, what does this do & what is its stimulus
A
somatostatin
inhibits acid
acid in stomach
23
Q
what do G cells secrete, what does this do & what is its stimulus
A
gastrin
stimulates acid secretion
acetlycholine, peptides
24
Q
what do chief cells secrete, what does this do & what is its stimulus
A
pepsinogen & gastric lipase
protein digestion
ActChl, secretin, acid
25
what do mucous cells secrete, what does this do & what is its stimulus
mucus & bicarbonate
physical barrier & chem protection
irritation & secreted with mucus
26
what do parietal cells secrete, what does this do & what is its stimulus
gastric acid & Intrinsic factor
activates pepsin, denatures protein, kills bacteria & vit B12 absorption (IF)
ActChl, gastrin, histamine
27
what do enterochromaffin like cells secrete, what does this do & what is its stimulus
histamine
stimulates acid secretion
ActChl, gastrin
stimulates acid secretion
28
what nutrients does the stomach absorb
water esp if cold
electrolytes
drugs (aspirin & alcohol)
29
why would the palatal and lingual tooth surfaces be at risk of erosion
patient suffering from reflux (gastric goes through oesophagus into oral cavity)
30
which patients may be more at risk of aspiration of stomach contents when under GA
hiatus hernia
non fasted
pregnant
31
which drugs can cause a dry mouth
chelates and complexes
| protein pump inhibitors (omeprazole)
32
which drugs can cause a chalky taste
antacids
33
which drug can cause staining of tongue, erythema multiforme & swelling and pain of salivary gland
H2 receptor antagonists - ranitidine
34
what is the approx length of the SI
6 meters
35
what is the approx length of the duodenum and jejunum
2.5m
36
what is the approx length of ileum
3.5m
37
what is the function of the small intestine
mechanical digestion- weak peristalsis
chemical digestion
absorption of nutrients across intestinal enterocyte
38
how long does chyme stay in the small intestine
3 to 5 hrs
39
what is meant by segmentation in the SI
local mixing of chyme with intestinal juices
| sloshing back and forth
40
what paracrine hormones are involved in the regulating the small intestine
secretin
GIP
GLP-1
CCK
41
what does secretin do
regulates water homeostasis & secretions in the stomach pancreas and liver
located in S cells of duodenum (intestinal glands
42
what is GIP produced by
k cells of duodenal and jejunal mucosa
43
what is GLP-1 produced by
intestinal enteroendodrine L-cells and some ENS and brainstem neurones
44
what does CCK do in the SI
stimulates release of digestive enzymes and bile from the pancreas and gall bladder
hunger suppressant
produced by enteroendocrine duodenal cells
45
how does chemical digestion occur in the small intestine
pancreatic juice
46
what cells produce pancreatic juice
acinar
47
how does pancreatic juice enter duodenum
pancreatic duct
48
what does pancreatic juice contain
proteases
lipases
amylase
sodium bicarbonate to neutralise chyme
49
which hormones regulate pancreatic juice secretion
CCK- enzyme rich
| secretin- bicarbonate rich
50
what are incretins
hormones that stimulate decrease of blood glucose levels
51
when are incretins released
at the beginning of intestinal phase of digestion
| GIP & GLP
52
how do incretins cause a decrease a blood glucose levels
stimulate insulin release from pancreatic b cells
| inhibit glucagon release from pancreatic a-cells
53
what hormone regulates bile
CCK
54
which hormone stimulates goblet cells
VIP
55
which enzymes break down carbs in the small intestine
sucrase-isomaltase
- sucrose = glucose + fructose
lactase
-lactose= glucose + galactose
56
how may lactose intolerance occur
damage to intestinal mucosa(age, drug treatment or chemotherapy)
57
where are the enzymes that break down carbs located
apical membrane of SI
58
where are peptidases found
brush border
59
how & where are food proteins hydrolysed for peptidases to act upon
pepsin - stomach
| pancreatic proteases- duodenum onwards
60
what do enterokinases do
partially hydrolyse pancreatic zygomen proteases to release the active enzyme
61
do brush border hyrolases act on lipids or nucleic acids
no
62
why are tight junctions important for the function of polarised cells
keep extracellular fluids surrounding apical and basolateral membranes separate & prevent diffusion of membrane proteins and glycolipids between fucntional domains
63
what are the consequences of tight junctions
prevent passage of molecules and ions between cells
| must enter by active transport
64
peristaltic waves cause aid mechanical digestion in the large intestine, outline how
haustral churning
gastroilial reflex
gastrocolic reflex
65
what happens the the haustral churning part of mechanical digestion in the LI
relaxed pouches filled from below muscular contractions (elevator)
66
what happens the the gastroilial reflex part of mechanical digestion in the LI
when stomach full gastrin hormone relaxes ileocal sphincter so small intestine will empty and make room
67
what happens the the gastrocolic reflex part of mechanical digestion in the LI
when stomach fills a strong perostaltic wave moves contents if transverse colon into rectum
68
are enzymes involved in chemical digestion in theLI
no, only mucus is secreted
69
what do bacteria ferment in the LI during chemical digestion
undigested carbs into CO2 and CH4
undigested proteins into simpler substances
bilirubin into simpler substances that produce colour
70
what vitamins do bacteria produce in the colon
K and B
71
what are faeces
dead epithelial cells, undigested foods, bacteria
72
what occurs during defecation in the LI
gastrolic reflex moves faeces into rectum
stretch receptors signal
parasympathetic nerves contract muscles of rectum and relax int anal sphincter
external sphincter is voluntarily controlled
73
What is the blood supply of the liver ?
hepatic artery from the abdominal aorta
| portal vein - nutrient rich blood from the GI tract
74
How are hepatocytes arrnaged ?
hexagonally
75
What are the hepatocytes in contact with ?
bile canaliculi on one side and the blood stream on the other
76
What are between hepatocytes ?
vascular spaces called sinusoids
77
What are kupffer cells ?
phagocytic macrophages which attach to sinusoids and play a protective roole
78
What does a portal triad conssit of ?
hepatic artery
portal vein
bile duct
79
What are the functions of the liver ?
```
filtering of blood
protein synthesis
carb metabolsim
lipid metabolsim
secretion of bile
```
80
How can the liver remove hormones , drugs and active molecules from the blood ?
excretion into the bile
phagocytosis by kupfer cells
chemical alteration
81
How is ammonia produced in the liver ?
deamiantion by amino acids
82
What does the liver do with ammonia ?
convert it intp urea to be excreted into the urine
83
How is ammonia released from glutamate ?
deamination of glutamate into alpha ketoglutarate produced ammonium ions
glutamate dehydrogenase
84
How is ammonia turned into urea ?
in the urea cycle
85
What is the route for the production and release of bile ?
bile is made in the liver
secreted into the hepatic duct
joins the cystic duct from the gall baldder
enters the duodenum through the common bile duct which goes through the pancreas
86
What does bile act for fats ?
emulsifier
87
What hormone regulates bile production ?
CCK
88
Where are chylomicrons produced ?
in the intestinal mucosa
| enoplasmic reticulum of enterocytes
89
Where are chylomicrons found ?
in the blood and the lymph
90
Where are newly formed chylomicrons secreted from ?
through the basolateral membrane
| into lymphatic vessels to veins
91
What is the role of chylomicrons ?
transport fat from the intestine top the liver and the adipose tissue
92
What do chylomicrons consist of ?
95% TAG
5% cholesterol
Apo B48
93
What are chylomicrons recognised by ?
lipoprotein lipases on the lining of blood vessels
94
What happens in chylomicron breakdown ?
broken down into FFA- oxidiesed for energy
LDL
HDL - taken up by the liver
reminants - taken up by the liver
95
What is the bile production rate in the liver ?
250-1500 ml a day
96
What is bile pigment ?
bilirubin
97
Where is bilirubin formed ?
spleen
bone marrow
liver
98
What is bilirubin a derivative of ?
haem groups without iron
99
What does bilirubin combine with ?
glucorinic acid - conjugated bilirubin
100
What is conjugated bilirubin converted into ?
urobilogen
| by intestinal bacteria
101
What is urobilogen absorbed by ?
intestine into the hepatic vein
102
What does bile consist of ?
bile acids and bile salts
detergents for fat ingestion
glucoronic acid
103
95% of bile acid is reabsorbed by?
ileum
104
What is the sphincter oddi ?
betwene the bile duct and thre duodenum
105
What is the pancreas an outgrowth from ?
duodenum
106
What are the 2 types of glands found in the pancreas ?
endocrine and exocrine glands
107
What is the arrangement of cells in the exocrine pancreas ?
arranged as raspberry like acini around a central lumen
| compound acinar
108
Many lumens contact each other to form what ?
ductules - coalesce to form the pancreatic duct
109
What do acinar cells form from ?
invagination of embryonic endoderm
110
What do the acianr cells open into ?
pancreatic duct
111
What is the apical membrane orientated towards ?
lumen
112
What is the basolateral membrane orientated towards ?
bloodtstream
113
Which hydrolytic enzymes do acinar cells synthesisie ?
amylases
proteases
lipases
nucleases
114
What are enxymes usually sotred as in the exocrine acinar cells and how are they released ?
as zymogens
| as secretory vesivles in the apical membrane
115
What does the basolaterla membrane contain ?
receptors which hormones bind to to regualte zymogen secretion from the secretory vesicles in the apical membrane
116
What is the neural control of the exocrine pancreas ?
vagus in anticipation of a meal
117
As chyme nters the duodenum what doe CCK do ?
circualtes to the basoalterla membrane of acinar cells and binds to a specific receptor
118
What is secretin released from ?
enteroendocrione cells
119
What is secretin reelase din repsonse to ?
acid in the duodenum
120
What does secretin do ?
activates the secretion of bicarbinate from the pancreas
| as pH increases bicarbonate release is stopped
121
What is the secretin receptor on the basolaterla membrane of the acinar cells like n?
7 pass trans membrane structure
| GPCR
122
How are proteases sotred in the exocrone pancreas ?
as zymogen sin the secretory vesicles in the apical membrane of the acianr cell s
123
What are tehe enzymes released from the exocrine pancreas ?
lipases
phospholipas A2
amylases
124
Where is bicarbiante relesed from in the oancres ?
epithelial cells in the pancreatic duct
125
What are the endocrine cells in the pancreas arranged as ?
isleets of langerhans
126
What are the hormones released from the endocrine opancreas and where from ?
alpha cells - glucagon
beta cells - insuklin
delta cells - somatostain - GHIH
127
What is vomiting controlled by ?
emetic centre in the chemoreceptor trigger zone in an area of the meduall oblangata
128
What is the process of vomiting ?
increaseed parasymapthetic acrtivity leads to increased salivation
retroperistalsis
increase in abdominal pressure and decrease in intrathoracic pressure
propel stomach contents into the oesophagus
129
What is the sympathetic resposne in vomiting ?
sweating and increased HR
130
What are the cell to cell junctions in the apical membrane ?
tight junctions
claudin and occludin
adaptor proteins which link to underlying actin- Z0-1 AND Z0-2
131
What are the cell0 cell junctions in the basolateral membrane ?
adherens junctions
E-cadherin
A AND BETA CATENIN
132
What is the gut assocaited lymphoid tissue ?
protects agaisnt antigens entering across the intestinal mucosal barrier
aggregates of lymphoid tissue
133
What are peyers patches ?
bumps of lymphoid tissue in mucosa of GI tract
| macrophages , dendritic cells and B and T lymphocytes found within
134
What are M cells ?
microfold cells
135
What are the role of M cells ?
specialised epithelial cells that overly peyers patches
| provide info about the contents of the gut lumen to the immune cells of the GALT
136
What does the apical surface of the M cells contain ?
clathrin coated pits with embedded receptors
137
What happens when antigens bind to the receptor ?
transcytosis to basolateral membrane
released to intestinal fluid macrophages and lymphocytes
trigger inflammatory response
138
What do M cells transport microbes by ?
endocytosis
phagocytosis
transocytosis
139
What do dendriticc cells do ?
convert T cells into T reg cells - release IL10
| supresses unecessary immune response
140
Damage to the intestinal epithelium leads to what ?
epithelial cells release signalling molecules
inhibition of IL10
D and T cells produce IL and TNF
neutrophils undergo NETosis and Apoptosis
141
How does food poisoning occur with M cells ?
some bacteria have evolved receptors which bind to M cell receptors
bacteria transported acorss M cells
immune system react- diarrhoea and vomiting
142
Good intestinal bacteria ?
biotin
vitamin K
intestinal flora
143
Good bacteria generate which antomicrobial peptides ?
lysoxymes
lactoferrin
defensins
144
What are the 2 types of multicellular glands ?
acinar and tubular
145
What is the epithelium in the excretory duct ?
pseudostratified columnar epithelium
146
Which salivary duct has pseudostratified columnar epithelium ?
excretory
147
Which parts of the salivary duct has simple cuboidal epithelium ?
intercalated dcut
148
What are serous demilunes ?
mixture of mucous and serous cells
149
What nutrients are abosrbed by the stomach ?
water , drugs , electrolytes and alcohol
150
What are some proteins produced in the liver ?
lipoproteins
| plasma proteins- albumin, fibrinogen, globulin,transferrin
151
In what form is pigment secreted int the bile ?
conjugated bilirubin
152
What are the gut defence mechanisms ?
```
taste and mouth fell
vomiting
gastric acid
hydrolytic enzymes
mucosal epithelial barrier
GALT
intestinal bacteria
```
153
What controls vomiting ?
the enteric centre in the chemoreceptor trigger zone in the medulla oblanagata
154
What initiates vomiting ?
chemoreceptors and the CNS
155
What is the parasympathetic contribution to vomiting ?
increased salivation
| retroperistalsis
156
Describe the pressure changes in vomiting ?
abdominal muscles contract- increase in abdominal pressure
lowering of thoracic pressure
propels stomach contents into the oesophagus
157
What is the sympathetic response in vomiting ?
sweating and increased heart rate
158
What type of junctions are in the mucosal epithelial barrier ?
tight junctions
159
What is the role of the mucosal epithelial barrier ?
keeps the ECF around the apical and basolateral memebranes separate
160
what is Gut Associated Lymphoid Tissue (GALT)
protects against antigens entering the body across mucosal barrier
161
what is a component of MALT
system of nodes
162
where are the collection of lymph nodes of MALT
tonsils
appendix
payers patches
163
what are microfold (M) cells
specialised epithelial cells that overlie peyers matches
164
what do M cells do
provide info about lumen contents to immune cells of GALT. move particles into lymphoid vessel
165
what does the apical surface of m cells contrian
clathrin-coated pits with embedded receptors
166
what do Dendritic cells do
accept antigen and develops reaction on whether is harmful.
associate with basal membrane with epitherlial cells and hijack proecsses through tight junction
project processes into intestinal lumenn
167
what do T lymphocytes do
develop into regulatroy t lymphoctes which generate iL10 important for response
168
how do m cells transport microbes and food particels
endocytosis
phagocytosis
transcytosis
169
outline the pathiophysiology of gut immune function
- Damage of intestinal epithelium
- Epithelial cells release signalling molecules
- inhibition of IL10 production by TReg cells
- D cells start to produce IL6, IL12 and IL23
- T cells start to produce IL17, IFγ and TNFα
- Neutrophils undergo NETosis
- Neutrophil apoptosis, start of cell repair and regeneration
170
what do bacteria (salmonella etc) do to cause food poisoning
have surfaces tha bind to m cells and are transported across epithelial barriet into body
- diarrhoea nad vomiting
171
what are the Intestinal bacteria (good bacteria!)
biotin
vit k
intestinal flora
antomicrobal polypeptides
172
what are the antomicrobal polypeptides
- Lysozymes- effective against gram + species (streptococcal)
- Lactoferrin- antiviral properties
- Defensins- antiviral properties
