1
Q
why is chewing gum good for your teeth after a meal?
A
- increase salivary secretion
- increase salivary amylase and material agents (lysozyme and IgA)
2
Q
what is IgA?
A
he main immunoglobulin found in mucous secretions, including tears, saliva, sweat, colostrum and secretions from the genitourinary tract, gastrointestinal tract, prostate and respiratory epithelium.
3
Q
why does your tummy grumble when you are hungry?
A
- cephalic phase of digestion
- gastric secretions and motility increased by
- parasympathetic NS, gastrin, gherlin (the hunger hormone)
4
Q
are there more cells or bacteria in your body?
A
bacteria
5
Q
parts of the GI tract
A
oesophagus, stomach, small intestine (duodenum, jejunum, ilieum), large intestine (colon), rectum, anus
6
Q
what is the role of the GI tract?
A
metabolise and digest/ferment carbohydrates and lipids
-synthesise vitamins (B and K)
7
Q
How is vitamin B12 absorbed within the GI system?
A
vitamin B12 is ingested in protein form, it must first undergo a proteolytic cleavage in the stomach or duodenum where it will bind to an R-binder and enter into the duodenum for further cleavage.
-Vitamin B12 then enters the blood bound to another binding protein, transcobalamin, the complex is known as holotranscobalamin (Active B12). The majority of vitamin B12(70-80%) in blood is bound to haptocorrin and only a minor proportion (20-30%) is bound to transcobalamin.
8
Q
How can a lack of B12 lead to anaemia?
A
- Pernicious anaemia…specific type of anaemia that restults from the impaired absorption of vitamin B12 in the small intestine.
- Vitamin B12 is structurally complex essential nutrient involved in many biological processes, including nervous system function and red blood cell formation.
- Patients with this type of anaemia exhibit neurological symptoms such as muscle weakness, numbness and tingling sensation aswell as the typical symptoms of anaemia.
- (RBCs don’d develop normally due to lack of B vitamins (B12 and folate), leads to decreased RBCs… causes include lack of intrinsic factor, diet low in in B vitamins, decreased absorption of B vitamins… treatment is life long supplements).
9
Q
why is anaemia?
A
a condition that occurs when the number of red blood cells/ the amount of haemoglobin found in them drops below normal.
10
Q
how is anaemia diagnosed?
A
testing blood (Hb conc)
11
Q
what does a deficiency in B12 lead to?
A
MACROCYTIC ANEMIA
12
Q
how does a lack in B12 lead to anaemia?
A
- Atrophic gastric muscoa fails to secrete normal secretions
- lack of intrinsic factor (IF) from gastric glands
- no binding of B12 to IF
- B12 isn’t protected from digestion by GIT enzymes and doesn’t bind to receptor sites in cells of terminal ileum
- failure to absorb B12 from GIT (without IF)
- pernicious anaemia
13
Q
where do you find the parietal cells and what do they release?
A
- In the gastric pits of the fundus
- release intrinsic factor and HCl
14
Q
where would you find chief cells and what do they release?
A
Fundus and pepsinogen
15
Q
where would you find D cells and what do they release?
A
found in the stomach and intestine and they release somatostatin
16
Q
where would you find G cells and what do they release?
A
- deep in the pyloric gland of the stomach (antrum) (occasionally in the duodenum)
- release gastrin
17
Q
What are the different glands found in the cell wall of the stomach?
A
- pyloric
- fundic
- cardiac
18
Q
Where is the funds in the stomach?
A
at the top
19
Q
where is the body in the stomach?
A
the middle
20
Q
where is the pyloric antrum in the stomach?
A
The bottom
21
Q
Where would you find chief and parietal cells?
A
in the funds and the body
22
Q
where would you find G and D cells?
A
In the pyloric antrum (and duodenum)
23
Q
what do cardiac glands secrete and where would yo find them?
A
Mucus, near the neck
24
Q
what do funcdic glands secrete?
A
HCl
25
what do pyloric glands secrete?
gastrin
26
What is gastric acid primarily released in response to?
proteins arriving in the stomach
27
how can the Parasympathetic NS increase gastric acid?
via gastrin
28
look at the diagram for stomach acid secretions
...
29
Stomach motility- which was does the peristaltic wave travel?
peristaltic wave travel towards the antrum (bottom) mixing the food
30
How long does gastric emptying take?
1-3hours depending on the nature of the food ingested
31
what opens to allow small amounts of chyme out of the stomach?
the pylorus
32
how is gastric motility regulated?
neurally and humorally
33
how is gastric motility regulated neurally?
- mostly enteric reflexes, plus autonomic
- stimulatory-parasympathetic
- inhibitory- sympathetic
34
where does the humoral response for the gastric motility stem from?
duodenum
35
what is the stimulatory and inhibitory hormones in the humoral response for gastric motility?
Stimulatory- motilin
| Inhibitory- secretin, CCK and somatostatin
36
what does gastrin in the stomach do?
Gastrin is in the stomach and stimulates the gastric glands to secrete pepsinogen (an inactive form of the enzyme pepsin) and hydrochloric acid. The secretion of gastrin is stimulated by food arriving in the stomach.
37
what does secretin in the stomach do?
Secretin is in the duodenum and signals the secretion of sodium bicarbonate in the pancreas and it stimulates the secretion of bile in the liver.
38
what does Cholecystokinin (CCK) do with gastric motility?
Cholecystokinin (CCK) is in the duodenum and stimulates the release of digestive enzymes in the pancreas and the emptying of bile from the gall bladder.
39
what does motion do in gastric motility?
Motilin is in the duodenum and increases the migrating myoelectric complex component of gastrointestinal motility and stimulates the production of pepsin.
40
what does somatostatin do in the stomach motility?
exerts an inhibitory effect on the parietal cells, decreases stomach acid production and by preventing the release of other hormones, including gastrin, secretin and histamine which effectively slows down the digestive process.
41
How are proteins absorbed within the small intestine?
- brush bearer enzymes, plus intracellular peptidase complete the job of digesting small peptides to amino acids
- amino acids transported across the GI epithelium by Active transport?
42
what is secondary active transport?
form of active transport across a membrane which couple the movement of an ion down its electrochemical gradient to the uphill movement of another molecule or ion against a conc gradient
43
how are simple fats absorbed in the small intestines?
monoglycides aan fatty acids pass across GI epithelium by simple diffusion
44
what do the hormones secretin and CCK promote?
pancreatic secretions
45
what are bile salts recycled via?
enterohepatic circulation
46
what is secreted in the bile?
- bile salts and lecithin to assist digestion and facilitate absorption of fats
- bicarbonate
- waste material
47
what is in pancreatic secretions?
digestive enzymes, targeting proteins, CHOs and fats
| -bicarbonate
48
what are bile and pancreatic secretions stimulated by?
- chyme in duodenum (distension, acid, fats and osmolarity)
| - hormones: CCK, secretin
49
what are HDLs? and what are they involved in?
- high density lipoproteins (good cholesterol)
| - involved in reverse cholesterol transport and collects cholesterol from peripheral tissues and deliver it to the liver
50
what are LDLs? and what are they involved in?
- low density lipoproteins (bad cholesterol)
- involved in transporting cholesterol from the liver to the hepatic portal tissue, where it can become deposited in blood vessel walls, oxidised and attract inflammatory cells leading to arteriosclerosis.
51
what do statins do?
Inhibit the synthesis of cholesterol within the liver, and up regulate the LDL receptors in the liver
52
what is HMG CoA?
the intermediate between Acetyl coA and Mevalonic acid in the synthesis of cholesterol
53
how is the HMG CoA regulated in the short term? and long therm?
Short term: hormonal regulation
Long term:
-High intracellular cholesterol
-Decreases the transcription of HMG-CoA gene
-Decreases the synthesis of cholesterol
54
what are the 5 basic functions of the digestive system?
- Digestion
- Absorption
- motility
- secretion
- excretion
55
what are the 4 major roles of the salivary secretions?
- moisten and lubricate food (bolus)- mucus
- initiate digestion of polysaccharide and lipids
- dissolve food
- antibacterial actions (IgA + lysozyme)
56
what is salivary secretions controlled by?
autonomic nervous system
57
what type of muscle makes up the oesophagus?
-upper 1/3 striated
-middle 1/3 mixture
-lowest 1/3 smooth
...voluntary action initially then becomes reflex
58
where does 90% of nutrient absorption occur?
```
small intestine
(absorption occurs in the first 1/4- duodenum and jejunum)
```
59
which enzymes break down proteins?
Trypsin, chymotrypsin, elastase and carboxypeptidate
60
what breaks down fats?
lipases
61
what breaks down polysaccharides?
amylase
62
what breaks down nucleic acids?
Ribonuclease and deoxyribonuclease
63
what do the liver and gall bladder secrete?
bile (bile salts, lecithin (phospholipid) bicarbonate ions, cholesterol, bile pigments, trace metals
64
what happens in the large intestine?
reabsorption of water, absorption (10%) of nutrients (lack of villi, and doesn't produce enzymes, provides lubrication for faecal material)
- absorptoni of important vitamins produced by bacteria
- storage and compaction of faecal matter (prior to defecation)
65
what role does the enteric nervous system play in the digestive system?
- can act independently of CNS
- Myenteric plexus- controls mainly smooth muscle contraction/tone
- Submucosal plexus- control mainly GI secretions and blood flow
66
what role does the autonomic NS play in the control of the digestive system?
VAGUS NERVE (parasympathetic)- increases motility and secretions (rest and digest)
sympathetic- decrease motility and secretions (fight or flight)
67
why are the 3 routes for gastrointestinal reflexes?
1) regulation of one area of enteric nervous system to another region
2) extrinsic nerves prevertebral sympathetic ganglia
3) vagus nerve via sensory neurones to brain and brain stem
68
what are the 3 phases of gastric acid secretion and stomach emptying?
- cephalic
- gastric
- intestinal
69
what happens in the cephalic phase?
- initated by smell/ taste
| - mediated via enteric and parasympathetic NS
70
what happens in the gastric phase?
- initiated in the stomach
- mediated via the enteric and Parasympathetic NS and the hormone gastrin
```
Initiated in stomach:
distension, protein
Gastrin mediated:
released by local and neural control
action both direct and indirect (via histamine)
```
71
what happens in the intestinal phase?
-initiated in duodenum
-mainly inhibitory hormones
-promoted continued digestion within small intestine
-Stimulatory:
protein in duodenum gastrin release
Inhibitory:
lowers pH, fat in duodenum
secretin, GIP, CCK ...gastrin inhibition
somatostatin: direct action and via gastrin
72
Cephalic phase
- parasympathetic and submucosal plexus stimulates:
- mucus (mucous cells), pepsinogen (chief cells) and HCl production (parietal cells)
-gastrin (G cells), GI hormone stimulates gastric secretions
73
gastric phase
-the arrival of food in the stomach leads to marked secretions and contractility
-histamine - stimulates parietal cells to release more HCl (response to parasympathetic NS and gastrin)
CNS- vagus nerve ( parasympathetic)
74
what does Histamine do?
released from enterochromaffin-like (ECL) cells (paracrine mechanism) in response to ACh and gastrin
75
what does somatostatin do?
Inhibits secretion of CCK, gastrin, secretin, GLIP – thus inhibiting a number of functions – also inhibits HCL secretion – released in response to HCL (neg feedback) – released from D-cells in pyloric gland and duodenum
76
what happens in the intestinal phase?
Hormones that inhibit gastric acid secretions/ gastric emptying... CCK, secretin, somatostatin
77
what does CCK do?
Cholecystokinin (CCK) – released by I cells in small intestine, stimulates pancreatic secretions & gall bladder contraction
78
what does secretin do?
released by s cells in response to low pH, stimulates pancreatic and bile secretions
79
what does somatostatin do?
inhibits everything, released by D cells
80
Motilin
peptide hormone – m cells of duodenum and jejunum, stimulates gastric and intestinal motility – released in response to fat, pH and neuronal stimulation
81
Factors inhibiting stomach emptying
- Duodenal distension
- Irritation of duodenum mucosa
- Lipids, FA, Protein and CHO (moderately)
- Acidity – pH <3.5-4
- Increase in osmolarity – indicative of the entrance into the duodenum of large volumes of soluble partially-digested particles
