Physiology Flashcards
(122 cards)
1
Q
- Choose the INCORRECT statement. Absorption of water/fluid…
A) occurs largely in the small intestine
B) occurs as a simultaneous process to secretion in the small intestine
C) is driven by the electrolyte movement, usually anions, across the luminal membrane
D) is aided by the large surface area provided by the folds, villi and microvilli
E) may occur in the small intestine in the villi
A
C) is driven by the electrolyte movement, usually anions, across the luminal membrane
Absorption is driven by electrolyte movement across the luminal membrane, but usually the absorption of Na ions or positive ions - CATIONS, not Anions which are negatively charged.
2
Q
- Regulation of gastric acid secretion…
A) also regulates intrinsic factor secretion
B) mostly involves enteroendocrine secretions in the cephalic phase
C) is mediated by the effect of acetylcholine (released by the PNS) on G cells thereby stimulating gastrin secretion
D) mostly increases acid production in the intestinal phase
A
A) also regulates intrinsic factor secretion
The factors which stimulate gastric acid secretion also stimulate Intrinsic Factor secretion. In the cephalic phase, acid production is stimulated through the vagal nerve and in the intestinal phase is mostly inhibited by enteroendocrine mechanisms. The PNS stimulates G cells via gastrin-releasing peptide (not acetylcholine).
3
Q
- Phase II of the MMC is characterised by motility which is…
A) quiet and minimal
B) submaximal and irregular
C) maximal and regular
A
B) submaximal and irregular
Phase I is quiet, Phase II submaximal and irregular and Phase III is maximal and regular.
4
Q
- The final secretion of the salivary glands is…
- hypotonic/isotonic/hypertonic?
- rich in…?
A
Hypotonic and bicarbonate-rich.
The initial secretion of the salivary glands is isotonic and during ductal modification, it becomes hypotonic and rich in bicarbonate (as Na & Cl are reabsorbed to a greater extent than K & HCO3 are secreted).
5
Q
- What is eructation?
A) burping
B) vomiting
C) farting
D) gurgling noises in the stomach
A
A) Burping
6
Q
- Which of the following will pass most slowly through the stomach?
A) Croissant with peanut butter
B) Skim flat white
C) water
D) Low fat yoghurt
A
A) Croissant with peanut butter.
Croissants and peanut butter have a high fat content and this will slow the gastric emptying.
7
Q
- What is the name of the motility pattern that occurs for short periods of time in the large intestine and is responsible for the distension of the rectum and the feeling of urgency?
A) peristalis
B) segmentation
C) haustrations
D) mass movements
A
D) Mass movements.
Mass movements are multi-haustral contractions that move the fecal matter along - usually into the rectum, causing distention and a feeling of urgency. Peristalsis is similar but it is given a different name here as the matter in the large intestines is not just a bolus but a larger volume which continues to fill large portions the intestines. Segmentation is the main motility pattern of the small intestine in the digestive phase and haustrations are the equivalent in the large intestine and allow fluid to be absorbed from the fecal matter.
8
Q
- Vomiting of gastric contents can cause…
A) metabolic alkalosis
B) metabolic acidosis
A
A) Metabolic alkalosis.
As gastric contents do not enter the small intestine, the alkaline tide is maintained. Think deeply about this. (no acidic stomach contents to stimulate somatostatin from the D cells in the pyloric gland area; no somatostatin to negatively feedback on G cells to reduce acid production and hence elevated HCO3- entering the blood, the ‘alkaline tide’)
9
Q
- Bile…
A) is stored and concentrated in the liver
B) is used to excrete toxic substances
C) is acidic in nature
D) contains substances that are required for the digestion of proteins and carbohydrates
A
B) is used to excrete toxic substances
Bile is stored and concentrated in the gallbladder (not liver). It is an alkaline secretion, rich in bicarbonate that contains bile salts and lecithin which aid in the digestion of lipids (not proteins or carbohydrates). It is a vehicle which allows the excretion of toxic substances from the body.
10
Q
- Which of the following is NOT found in saliva in large concentrations and plays little role in digestion?
A) Lipase
B) Amylase
C) Protease
D) Mucus
A
C) Protease
There is always mucus in the GIT. Lingual lipase and salivary amylase….remember? Although lingual lipase also doesn’t do that much. The saliva also contains small amounts of kallikreins (proteases) but they are not significant in digestion. Best answer here is protease.
11
Q
- To achieve the final pancreatic secretion exchange of which two ions takes place during ductal modification?
A) Na and Cl B) K and Cl C) HCO3 and Cl D) Na and K E) HCO3 and PO4 F) Na and HCO3
A
C) HCO3 & Cl
The process of ductal modification allows exchange of chloride & bicarbonate producing a bicarbonate rich pancreatic solution.
12
Q
- Which of the following gives the correct order of the gut wall layers starting innermost?
A) submucosa, muscularis externa, mucosa, serosa
B) mucosa, submucosa, muscularis externa, serosa
C) muscularis externa, mucosa, submucosa, serosa
D) serosa, muscularis externa, submucosa, mucosa
A
B) mucosa, submucosa, muscularis externa, serosa
13
Q
- Which of the following is NOT a mechanism stimulating acid secretion?
A) distention of the antrum => local ENS reflex
B) amino acids in stomach antrum => stimulating G cells
C) low pH in stomach => stimulating D cells
D) sight of food => stimulating vagal outflow
A
C) low pH in stomach => stimulating D cells
Stimulation of D cells increases somatostatin secretion which inhibits acid secretion
14
Q
- Which of the following does not relate to smooth muscle properties or function within the GIT?
A) unitary smooth muscle
B) functions as a syncytium
C) has gap junctions (low resistance pathways)
D) has a flat resting membrane potential
A
D) has a flat resting membrane potential
Smooth muscle in the gastrointestinal tract has a slow wave potential - undulating membrane potential which can generate action potentials when it reaches threshold
15
Q
- Which of the following has the lowest volume of secretion per day?
A) stomach B) pancreas C) liver D) small intestine E) large intestine
A
E) large intestine
The large intestine secretes very small volumes per day - almost neglible and mostly mucus. The other options secrete quite large volumes - go check the lecture notes.
16
Q
- Which of the following occurs when parietal cells are stimulated?
A) tubulovesicles fuse with the luminal membrane
B) tubulovesicles are snipped off the luminal membrane
C) mitochrondrial activity decreases
D) luminal surface area decreases
A
A) tubulovesicles fuse with the luminal membrane
When parietal cells are stimulated, the tubulovesicles (containing proton pumps) fuse with the luminal membrane increasing its surface area and capacity for acid production. Acid production requires energy and mitochondrial activity would increase (not decrease).
17
Q
- Which of the following motility patterns is characteristic during fasting?
A) peristalsis
B) segmentation
C) mass movements
D) migrating motor complex
A
D) migrating motor complex
The MMC occurs during fasting and has three characteristic phases. It occurs approximately every 90 minutes starting at the stomach and continuing through to the ileum. The MMC can be disrupted by feeding.
18
Q
- Vitamin B12 absorption…
A) is increased in patients who have had gastric bypass surgery
B) occurs in the duodenum
C) requires complex formation with bile salts
D) may decrease if acid production is decreased
A
D) may decrease if acid production is decreased
Vitamin B12 absorption requires formation of the VitB12/Intrinsic Factor complex. IF is secreted by parietal cells and under the same conditions as acid secretion. If acid secretion decreases, IF secretion will decrease and vitamin B12 absorption will decrease. Additionally a decrease in acid secretion may affect the liberation of vitamin B12 from food (maldigestion) which will affect absorption. Bypass surgery produces low levels of acid secretion in the small proximal stomach pouch.
19
Q
- If there is a 15 ul/cm/min secretory flux and a 50 ul/cm/min absorptive flux occurring simultaneously, then what is the net flux result?
A) 60 ul/cm/min secretion
B) 60 ul/cm/min absorption
C) 35 ul/cm/min secretion
D) 35 ul/cm/min absorption
A
D) 35 ul/cm/min absorption
Secretion and absorption are separate processes that occur at the same time. The net effect is the balance of the two individual components. If 50 is being absorbed whilst 15 is being secreted then the combined effect is 50-15 = 35 absorption.
20
Q
- Which of the following is true with regard to the summed volumes being secreted into the gastrointestinal tract in a typical day?
A) saliva + small intestine < gastric juice + pancreatic secretions + bile
B) gastric juice < small intestine
C) saliva > gastric juice
D) small intestine > bile + pancreatic secretions
A
A) saliva + small intestine < gastric juice + pancreatic secretions + bile
Whilst you don’t need to know the exact numbers it helps to know their relative amounts. Small intestine (~1000ml), saliva (~1500ml), bile + pancreatic secretions (~2000ml) and the gastric juice (~2500ml)
21
Q
- In the jejunum the following are absorbed:
A) sugars, amino acids, NaHCO3
B) glucose, amino acids, calcium, bile salts
C) sugars, NaCl, vitamin B12
D) amino acids, intrinsic factor, iron
A
A) sugars, amino acids, NaHCO3
Bile salts, vitamin B12 and intrinsic factor are all absorbed in the ileum. Sugars and amino acids are absorbed co-transported with Na in the jejunum and NaHCO3 is absorbed preferentially to NaCl. HCO3 being absorbed in the form of CO2 and H20 not as HCO3.
22
Q
- The following are fat soluble vitamins:
A) A, D, B1
B) B1 & B2 (does that remind you of a song?)
C) A, D, E, K
D) B5, A, K, D
A
C) A, D, E, K
Vitamins B & C are water soluble.
23
Q
- What is the function of aldosterone?
A
Aldosterone levels are influenced by Na & K levels in the body. Aldosterone increases to aid Na conservation by allowing Na to be reabsorbed through the ENaC (epithelial sodium channels) in the colon. Aldosterone also increases the number of Na/K pumps on the basolateral membrane in the same cells as the combination of the Na/K pumps & the ENaC increases the Na absorption from the lumen of the large intestine.
This is the same process which occurs to stimulate Na reabsorption in the late distal tubule & collecting duct of the renal tubule.
24
Q
- Which one of the following is NOT TRUE of Cholecystokinin (CCK):
A) stimulates production of a more alkaline pancreatic secretion
B) is released from I cells in response to luminal amino acid/fat content
C) stimulates secretions of the acinar cells in the pancreas
D) relaxes the Sphincter of Oddi
A
A) Stimulates production of a more alkaline pancreatic secretion.
CCK is released from I cells in response to the presence of amino/acids or fats in the duodenal lumen and via an endocrine action stimulates the ACINAR (not DUCT) cells. Acinar cells produce digestive enzyme content whilst duct cells modify the secretion making it more alkaline.
SECRETIN from S cells responding to increased luminal acidity stimulates the production of a more alkaline pancreatic secretion.
25
25. With respect to salivary secretion:
A) the final secretion will be alkaline even at high flow rates
B) the initial secretion is hypotonic with respect to plasma
C) the saliva is saltier [contains more NaCl] at low flow rates compared to high flow rates
D) it is primarily under endocrine control
A) the final secretion will be alkaline even at high flow rates
The primary salivary secretion from the acinar cells is isotonic & plasma-like in electrolyte composition. As the secretion travels through the duct cells it undergoes modification so that Na & Cl are absorbed (making the final secretion less salty) and K & HCO3 are secreted (making the final secretion more alkaline). Absorption occurs to a greater extent than secretion so the final secretion will be hypotonic. While less modification takes place at high flow rates, bicarbonate secretion is maintained and the final secretion will be alkaline. Salivary secretion is primarily under neural (not endocrine) control.
26
26. The intestinal phase of gastric acid secretion is largely regulated by...
A) the parasympathetic nervous system
B) the enteroendocrine secretions of the GIT
C) a combination of the parasympathetic nervous system and the enteroendocrine secretions of GIT
B) the enteroendocrine secretions of the GIT
Once food enters the intestines it is mainly the enteroendocrine cells responding to the composition of the chyme in the lumen that feeds back to inhibit gastric acid secretion (& gastric motility/emptying).
27
27. Which of the following is INCORRECT about Bile
A) It is produced by hepatocytes
B) It is stored in the gallbladder
C) It contains bile salts
D) It is recycled
D) It is recycled.
Bile SALTS are recycled. Bile salts are just one component of Bile - so Bile as such is not recycled. Bile is produced by the hepatocytes & stored and concentrated in the gallbladder.
28
28. The cephalic phase of gastric secretion:
A) is mediated by the vagus nerve
B) begins when food is tasted
C) accounts for about 80% of the total acid secretion
D) involves secretions from enteroendocrine cells in the duodenum
A) is mediated by the vagus nerve.
The cephalic phase of acid secretion is responsible for about 30% of the total acid secreted & is initiated with the sight & smell of food (even before it is tasted). It is mediated entirely through the vagus nerve.
29
29. Glucose is an end product of the reaction catalyzed by
a) Sucrase
b) Lactase
c) Maltase
d) Lipase
e) Amylase
c) Maltase
Know your disaccharides &monosaccharides. Maltose is composed of 2 glucose molecules so maltase breaks this down into glucose. Maltose also digests malto-triose to glucose molecules. Sucrose is composed of a fructose & a glucose and is broken down by sucrase. Lactose is glucose & galactose digested by lactase. Lipases digest lipids. Amylase is an endo-enzyme so can't produce individual glucose molecules. Dextrinase can produce glucose molecules but it wasn't an option.
30
30. Removal of the proximal small bowel will have which one of the following effects:
A) decreased gastric acid secretion
B) increased gastric acid secretion
B) increased gastric acid secretion
Inhibitory feedback on gastric acid secretion is largely initiated by the enteroendocrine cells in the duodenal & jejunal mucosa. Without this feedback, gastric acid secretion would be increased (as in, inhibition would be lost).
31
31. The transporter (on the basolateral membrane) that is important for chloride secretion in the crypts is:
A) Na/H pump
B) H/K exchanger
C) HCO3/Cl exchanger
D) NaK2Cl symporter
D) NaK2Cl symporter
The NaK2Cl symporter brings in chloride ions that can then leave via the chloride channels on the luminal membrane. Na follows the Chloride and water follows by osmosis giving a largely NaCl secretion.
32
32. Causes of diarrhoea include:
```
A) loss of absorptive mucosa
B) infections e.g. cholera
C) secretagogue secreting tumours
D) osmotically induced mechanisms
E) all of the above
```
E) all of the above
Lactose intolerance is an example of an osmotically induced diarrhoea. Some tumours secrete high concentrations of hormones/peptides that are secretagogues (that is they cause secretion). Cholera etc stimulate the opening of the chloride channels in the crypts causing fluid secretion and losing absorptive mucosa is a problem as the SI needs to absorb around 7 litres per day otherwise the absorptive capacity of the LI is overwhelmed.
33
33. Net electrolyte secretion in the large intestine occurs for:
A) Na and Cl
B) HCO3 and Cl
C) HCO3 and K
D) K and Na
C) HCO3 and K
This is why diarrhoea can produce a loss of HCO3 and K - producing metabolic acidosis and hypokalemia.
34
34. Intestinal calcium absorption is increased by:
A) increased vitamin D levels
B) increased vitamin A levels
C) increased vitamin B levels
D) increased vitamin C levels
A) increased vitamin D levels
Increased vitamin D causes an increase in the brush border Ca binding proteins and so increases calcium aborption
35
35. The following is a feedback reflex
A) gastro-gastric reflex
B) gastro-ileal reflex
C) gastro-colic reflex
D) entero-gastric
D) entero-gastric
Feedback means the stimulation occurs more distally in the GIT and the response ealier (feeding back to slow down the progress of the chyme through the system). The entero gastric reflex is stimulated in the intestines and provides a response to slow the stomach (gastric) motility.
36
36. Amylase produces...
a) alpha-limit dextrins
b) glucose & fructose
c) dissacharides
d) glucose and galactose
e) none of the above
f) a & c
f) a & c
it doesn't produce any of the monosaccharides
37
37. Na absorption in the small bowel:
A) occurs by secondary active transport
B) decreases with glucose absorption
C) occurs by active transport at the apical membrane
D) occurs with chloride, both moving through tight junctions
A) occurs by secondary active transport
Na absorption occurs across the luminal, apical membrane (not through tight junctions w chloride) by secondary active transport - i.e. secondary to the Na gradient set up by the Na/K pump on the basolateral membrane. So the active transport is on the basolateral membrane not apical. As Na is cotransported with glucose, Na absorption increases w glucose absorption.
38
38. After a fatty meal, most of the fat would be:
A) absorbed into the portal circulation & transported to the liver
B) absorbed into the portal vein & transported to the hepatic artery
C) absorbed as chylomicrons into the lymphatics
D) absorbed as triglycerides into the portal vein & bypass the liver
C) Absorbed as chylomicrons into the lymphatics
Most of the fats are packaged as chylomicrons & absorbed into the central lacteal of the villi (not the capillaries and so not entering the portal circulation).
39
39. Release of which one of the following increases the pH of the duodenal contents:
```
A) Secretin
B) Gastrin
C) Intrinsic factor
D) Cholecystokinin
E) Gastrin Releasing Peptide
F) Pepsin
```
A) Secretin
Secretin stimulates BICARBONATE SECRETION & therefore makes the duodenal contents more alkaline. Intrinsic factor & pepsin have no effect on pH. Gastrin & Gastrin Releasing Peptide (neurotransmitter from the vagus innervating G cells) both stimulate acid secretion so decrease pH. Cholecystokinin can increase pH but only in that it augments the effects of Secretin.
40
40. Gastric acid secretion is decreased by:
A) Vagal inhibition
B) Luminal peptides and amino acids
C) Histamine release from ECL cells
D) Distention of the stomach wall
A) Vagal inhibition
Vagal stimulation increases acid secretion so vagal inhibition will decrease acid secretion. Luminal peptides and amino acids stimulate gastrin release from G cells and increase acid secretion. Distension of the stomach wall stimulates acid secretion by short (ENS) and long (Vagal) reflexes. Histamine stimulates H2 receptors on parietal cells and stimulates acid secretion via cAMP pathway.
41
41. In the small intestine, glucose is absorbed:
A) passively
B) in combination with sodium
C) by facilitated diffusion
D) cotransported with chloride
B) in combination with sodium
Glucose is absorbed via secondary active transport in combination with sodium via the SGLT transporter on the apical membrane. Sodium also co-transports amino acids & other solutes (via other transporters).
42
42. Following ingestion of a meal:
A) Digestion of fat & carbohydrate begin in the mouth whilst protein digestion begins in the stomach
B) Digestion of protein begins in the mouth & fats and carbohydrates begin in the stomach
C) Most fluid & electrolytes are absorbed in the large bowel
D) Composition of the food has no effect on transit time through the bowel
A) Digestion of fat & carbohydrate begin in the mouth whilst protein digestion begins in the stomach.
Lingual lipase and salivary amylase begin the digestion of fats and carbohydrates (respectively) in the mouth whilst pepsin begins the digestion of proteins. The lipase and amylase action are minimal but the enzymes are present. Protein digestion does not occur in the mouth unless we are talking manual breakdown through chewing. Most fluids and electrolytes are absorbed in the small (not large) bowel and transit time is affected by the composition of the food - for example, high fat meals slow emptying from the stomach - so increase the transit time through the bowel.
43
43. Retropulsion refers to:
A) the mixing of the gastric contents
B) the emptying of the stomach
C) Harry & Ron transiting the barrier at Platform 9 and 3/4
D) the frequency of the slow wave in the Interstitial Cells of Cajal
A) the mixing of the gastric contents.
Retropulsion refers to the "throwing back" effect that occurs when gastric contents are propelled against a closed pyloric sphincter causing a mixing of the gastric contents. Retropulsion is similar to Harry & Ron NOT being able to transit the barrier at platform 9 & 3/4 (because Dobby had magically sealed it). Whilst the frequency of the slow wave potential in the stomach will determine the highest rate of peristaltic wave activity & hence the amount of gastric mixing it is not what "retropulsion" is referring to.
44
44. In the fasting state, the type of motility occurring in the small intestine is:
A) peristalsis
B) migrating motor complex
C) segmentation
D) mass movements
B) migrating motor complex
| What are 4 of its features?
45
45. What are the four basic processes of the gastrointestinal tract?
A) Digestion, elimination, chewing, fasting
B) Secretion, digestion, elimination, absorption
C) motility, secretion, ruminating, elimination
D) Digestion, absorption, secretion, motility
D) Digestion, absorption, secretion, motility
The four basic processes are digestion (of foodstuffs), absorption (into the blood or in the case of fats into the lymphatic system), secretion (of acid, mucus, digestive enzymes, water, electrolytes etc.) & motility (just to keep things moving along!).
46
46. The four layers of the gut wall in no specific order are: submucosa, serosa, muscularis externa & mucosa
True or False?
True!
The mucosa is the innermost layer where absorption and section take place followed by the submucosa which contains veins & arteries & connective tissue & such like. The muscularis externa is made up of 2 muscle layers - the inner circular layer & the outer longitudinal layer. They provide for all types of movements such as grinding, mixing, peristalsis, mass movements, expulsion, swallowing etc. Lastly there is the serosal layer.
47
47. The four anatomical areas of the stomach are:
A) Trunk, head, body, legs
B) Cardiac, body, funny, antral
C) Fundus, cardia, corpus, antrum
D) Fungus, body, corpus, antrum
C) Fundus, cardia, corpus, antrum
The cardia is the area around the junction of the lower oesophagus and the stomach. The fundus is the area which is at the top of the stomach (usually above the level of the cardia). The corpus (or body) of the stomach makes up most of the stomach with the antrum being the last third or so just prior to the pylorus.
48
48. The mucosa in the corpus is called the oxyntic mucosa.
True or False?
True!
Oxyntic mucosa is mucosa that produces acid. The corpus and the fundus have oxyntic mucosa. The cardia and the antrum generally don't produce acid.
49
49. The MMC (migrating motor complex):
A) occurs just after feeding
B) is initiated in the duodenum
C) has four characteristic phases
D) has a function of mixing food with intestinal contents
E) cycles approximately every 90 minutes or so
E) cycles approximately every 90 minutes or so
The MMC is the motility pattern that occurs during fasting. It is initiated in the stomach (not duodenum) and progresses down to the terminal ileum. On reaching the ileum the complex is reinitiated in the stomach. The MMC has 3 phases. Phase 1 is a period of inactivity - the quiet phase. Phase 2 is made up of irregular, non-maximal contractions and Phase 3 is a shorter period of regular maximal contractions. It is thought to be a housekeeper function - moving debris through the intestines during fasting.
50
50. Some cell types found in the Antrum (and their secretions) are:
A) D cells which secrete somatostatin & G cells which secrete gastrin
B) S cells which secrete somatostatin & G cells which secrete glucagon
C) G cells which secrete gastrin & P cells which secrete pepsinogen
D) D cells that secrete duodenum & G cells which secrete gastrin
A) D cells which secrete somatostatin & G cells which secrete gastrin
D cells produce somatostatin (it's also the same in the pancreas where the delta (D) cells also produce somatostatin.) Gastrin is produced by G cells. Chief cells produce pepsinogen and alpha cells produce glucagon.
51
51. The mucosa in the Antrum is called the pyloric gland area.
True or False?
True!
The mucosa in the antrum is close to the pylorus and is the pyloric gland area. It doesn't produce acid but contains enteroendocrine cells such a D & G cells.
52
52. Pepsinogen is secreted by
```
A) chief cells
B) parietal cells
C) D cells
D) G cells
E) stem cells
```
A) chief cells
Pepsinogen is activated in the presence of HCl to produce pepsin which is an endopeptidase - can produce smaller peptide chains from complex proteins.
53
53. Which of the following statements is correct with respect to the 2 main nerve plexuses & the functions for which they are generally responsible.
A) The mucosal plexus is responsible for motility & the submucosal plexus is responsible for absorption
B) The submucosal plexus is responsible for absorptive/secretory functions & the myenteric is responsible for motility
C) The serosal plexus is responsible for secretion & the myenteric plexus is responsible for motility
D) Auerbach's plexus is responsible for motility & the myenteric plexus is responsible for absorption
B) The submucosal plexus is responsible for absorptive/secretory functions & the myenteric is responsible for motility
The submucosal plexus being close to the mucosa helps to regulate the absorptive and secretory functions that occur here. The myenteric plexus is found between the inner circular and outer longitudinal muscle layers which are responsible for the numerous types of motility found in the GIT.
54
54. The lumen is on the serosal side of the gut wall.
True or False?
False!
The lumen is on the mucosal (innermost) side of the gut wall.
55
55. Which nervous system is known as the 'rest and digest' nervous system?
A) sympathetic nervous system
B) parasympathetic nervous system
C) enteric nervous system
D) autonomic nervous system
B) parasympathetic nervous system
The sympathetic NS is the fight or flight NS. The parasympathetic is the rest and digest. They are both part of the autonomic nervous system which has three divisions: the sympathetic, parasympathetic and enteric nervous systems.
56
56. Salivary secretion starts off __________ and after ductal modification becomes __________ .
```
A) isotonic, hypotonic
B) isotonic, hypertonic
C) hypotonic, isotonic
D) hypotonic, hypertonic
E) hypertonic, isotonic
F) hypertonic, hypotonic
```
A) isotonic, hypotonic
The initial primary secretion is very similar to plasma in composition so is isotonic but becomes hypotonic after the absorption of Na and Cl exceeds secretion of K and HCO3 in the duct cells.
57
57. Salivary secretion is primarily under
A) endocrine (hormonal) control
B) neural (parasympathetic, sympathetic) control
C) a mixture of endocrine and neural control
B) neural (parasympathetic, sympathetic) control
The control of salivary secretion is entirely under neural control. The parasympathetic and sympathetic nervous systems both stimulate salivary secretion but the parasympathetic stimulates a watery copious secretion while the sympathetic stimulates a thick mucous secretion
58
58. Pancreatic secretions start off _____________ and after ductal modification they are _____________ .
```
A) isotonic, isotonic
B) isotonic, hypotonic
C) isotonic, hypertonic
D) hypotonic, hypertonic
E) hypertonic, hypotonic
```
A) isotonic, isotonic
Pancreatic secretions start off as a plasma-like secretion so are isotonic but following ductal modification (exchange of chloride and bicarbonate ions) the secretion remains isotonic.
59
59. CCK comes from which cells?
A) D
B) G
C) S
D) I
d) I Cells
Somatostatin comes from D cells, Gastrin from G cells, Secretin from S cells and CCK from I cells. The D stands for delta, S stands for 'small' and the I stands for 'intermediate' - G we hope stands for GASTRIN.
60
60. Secretin is also known as "Nature's antacid"
True/False?
True!
In acidic conditions, then it's Nature's antacid to the rescue. Secretin release is stimulated by acid in the duodenum. Secretin, released from S cells, will stimulate the alkaline secretions of the pancreatic ducts, of the liver and of the brunners glands.
61
61. Cholecystokinin (CCK) stimulates/produces the following:
A) contraction of the gallbladder
B) pancreatic digestive enzymes (acinar cells)
C) relaxation of the sphincter of Oddi
D) all of the above
D) all of the above
CCK stimulates the production of pancreatic digestive enzymes in response to fats & proteins in the duodenum. Additionally, it stimulates the contraction of the gallbladder to release bile into the small intestine through the sphincter of Oddi (which it relaxes).
62
62. Which section of the gastrointestinal tract typically absorbs the most fluid each day?
A) stomach
B) small intestine
C) large intestine
D) mouth
B) small intestine
The small intestine typically absorbs about 7 litres of fluid each day. The stomach absorbs almost no fluid, but secretes a couple of litres of acid. The large intestine absorbs around 2 litres per day to form semi-solid stools that are not too hard (gives you constipation) or soft (bit of diarrhoea) but just right (thank goodness).
63
63. Cholera toxin induces diarrhoea via the following mechanism:
A) by inserting ENaC (epithelial sodium channels) in the apical membrane
B) by opening chloride channels in the apical membrane
C) by stimulation of VIP on the basolateral membrane
D) by increasing the sodium potassium ATPase activity
B) by opening chloride channels in the apical membrane
It just does ... need to know your mechanisms. Secretion of fluid into the intestinal lumen is usually driven by the secretion of an anion - in this case chloride. Sodium and water follow to balance and equilibrate. More secretion and normal absorption will mean that the net flux will be either decreased absorption or (if secretion is greater now than absorption) will tip over to secretion.
64
64. SAQ: Explain why a decrease in the number of villi could cause diarrhoea. (8 marks, 8 mins)
Each * indicates a mark.
Villi are found in the small intestine*, where they increase the surface area* for absorption of water* and nutrients*.
A lack of villi mean that the absorptive capacity of the small intestine is decreased*. The small intestine usually absorbs approx. 7L of fluid* and most of the end products of digestion*.
As the absorption of nutrients may be impaired, and the nutrients remain in the intestine, this may produce an osmotic effect * drawing more water into the lumen of the small intestine.
The combination of these two factors (decreased absorptive capacity & stimulated secretion) will mean a higher volume of fluid is presented to the large intestine.*
The large intestine having no villi, has a smaller capacity for absorption of fluid* (usually about 2 L per day and a max capacity of double this, ~ 4 L per day)*
If the amount of fluid entering the large intestine is greater than the absorptive capacity of the large intestine* a watery stool (diarrhoea)* will result.
65
65. The postganglionic fibres of the parasympathetic nervous system secrete:
A) Noradrenaline (norepinephrine)
B) Acetylcholine
C) Acetylcholine or peptides
D) Adrenaline
C) Acetylcholine or peptides
The postganglionic fibres of the parasympathetic nervous system are part of the enteric nervous system and may secrete either acetylcholine, peptides or both.
66
66. The autonomic nervous system has this many divisions:
A) two
B) three
C) four
B) three
Three divisions - the sympathetic, the parasympathetic and the enteric nervous systems
67
67. Short reflexes originate in the enteric nervous system and are carried out entirely within the wall of the gut
T) True
F) False
T) True
68
68. Which one of the following is not an endocrine secretion of the pancreas?
```
A) Somatostatin
B) GIP (Glucose-dependent insulinotropic peptide)
C) Pancreatic polypeptide
D) Glucagon
E) Insulin
```
B) GIP (Glucose-dependent insulinotropic peptide)
Endocrine secretions enter the blood. Insulin, glucagon, somatostatin and pancreatic polypeptide are the endocrine secretions. GIP is found in enteroendocrine cells - within the intestines.
69
69. Which of the following does NOT stimulate G cells?
A) local distension in the antrum of the stomach
B) presence of amino acids
C) Gastrin releasing peptide from the vagal nerve terminals
D) Somatostatin from neighbouring D cells
D) Somatostatin from neighbouring D cells
Somatostatin secreted in a paracrine fashion from D cells onto neighbouring G cells has an inhibitory effect.
70
70. Somatostatin release is stimulated by:
A) a high pH in the stomach
B) acetylcholine from the parasympathetic innervation
C) gastrin from neighbouring G cells
D) distension of the stomach
C) gastrin from neighbouring G cells
A low stomach pH below 3 stimulates somatostatin release. The parasympathetic system exerts an inhibitory effect on D cells. Gastrin released in a paracrine fashion stimualates the release of somatostatin from the nearby D cells. Distension of the stomach stimulates G cells not D cells.
71
71. The intestinal phase of acid secretion is mediated by:
A) the vagus
B) both vagal & enteroendocrine mechanisms
C) mostly enteroendocrine mechanisms
D) none of the above
C) mostly enteroendocrine mechanisms
When food enters the intestines acid production slows and is inhibited. This is achieved mainly by the enteroendocrine cells responding to the presence of chyme in the small intestine and feeding back to the stomach to decrease acid production.
72
72. Cholecystokinin has the following functions:
```
A) relaxation of the sphincter of Oddi
B) contraction of the gallbladder
C) stimulates digestive enzymes from the acini cells of the pancreas
D) A and B above
E) A, B and C above
```
E) A, B and C above
Cholecystokinin from the I cells in the duodenum is released in an endocrine fashion in response to lipids and proteins (amino acids) in the small intestine. CCK serves to stimulate the release of bile (by contracting the gallbladder and relaxing the sphincter of Oddi) and stimulates the production (release) of digestive enzymes from the pancreatic acini cells into the primary secretion of the pancreas and ultimately the final pancreatic secretions.
73
73. Secretin responds to which of the following stimuli?
A) acid in the stomach
B) acid in the duodenum
C) amino acids in the duodenum
D) amino acids in the stomach
B) acid in the duodenum
Secretin from S cells in the duodenum respond to the presence of acidic chyme as it enters the duodenum from the stomach. Secretin stimulates the production of an alkaline aqueous solution from the duct cells of the pancreas. It also stimulates the alkaline secretions of the Brunner's glands and the bile.
74
74. SAQ: Explain how cholera toxin can give you diarrhoea and suggest ways to treat this. (10 marks/10 minutes).
There are two parts to this question – the explanation will be worth 8 marks and the ways to treat it worth 2 marks. I would happy to have you draw a diagram similar to that attached and annotate with dot points.
Part 1: Explanation – any of the following statements worth 1 mark each up to a total of 8 marks.
1. Firstly some kind of statement explaining how diarrhea can occur in general absorption/secretion type scenarios – I have given three ways of approaching this and any or them would earn you a mark. Diarrhoea occurs (a) when then normal net absorption that occurs in the small and /or large intestine is decreased or is converted to a net secretion – (b)If the absorptive capacity of the intestines is insufficient to cope with an increase in secretion (c) If the total amount left in the stools following absorption in the small and large intestine is substantially greater than the normal 100 mls per day.
2. Cholera toxin enters the GIT through the oral route and although some of this may be sterilized and killed in the stomach due to acid action, its effect will ensue if it makes its way to the small intestine.
3. The receptor that responds to the cholera toxin is found on the luminal membrane
4. Stimulation of the luminal membrane receptor causes adenylcyclase to breakdown ATP into cAMP increasing its concentration
5. cAMP stimulates the opening/activation of chloride channels on the luminal membrane causing chloride efflux into the lumen
6. Sodium ions move through the paracellular spaces as the lumen becomes more negative and water follows
7. The increased chloride secretion drives the secretion of fluid into the lumen and this may overwhelm the absorptive capacity of the small and large intestine causing diarrhea.
8. Chloride efflux is driven by increased intracellular concentrations- chloride being brought into the cell via a NaK2Cl symporter on the basolateral membrane
9. The symporter is driven by the Na/K exchanger on the basolateral membrane which decreases the intracellular sodium concentration and drives the symporter to bring in Na and with it K and Chloride.
10. The cholera effect usually lasts 3-4 days as the effect lasts until the affected cells die
Part 2: Treatment: Any of the following statements will earn a half a mark, except for point 4 which is worth 1 mark, up to a total of 2 marks.
1. Diarrhoea causes dehydration and treatment involves rehydration
2. Absorption of fluid occurs through the villi – mostly in the small intestine and is driven largely by sodium reabsorption (with chloride and water following)
3. As fluid loss includes water and electrolytes, both water and electrolytes replacement should be part of the treatment
4. Addition of glucose to the rehydration fluid will stimulate fluid absorption as absorption of sodium can be co-transported with glucose.
75
75. Digestion occurs mainly in the:
A) stomach
B) small intestine
C) large intestine
D) mouth
B) small intestine
Most digestion and absorption of nutrients occurs in the small intestine. The mouth begins the digestion of carbohydrates (salivary amylase) but this action is inhibited in the acid environment of the stomach. In the stomach there is mechanical breakdown and a bit of protein breakdown to smaller peptide fragments, but not full digestion - this occurs in the small intestine with the addition of the bile and the pancreatic enzymes.
76
76. Carbohydrates need to be broken down into the following units to be absorbed:
A) glucose, galactose, fructose
B) galactose, lactose, glucose
C) fructose, sucrose, lactose
D) glucose, maltose, fructose
A) glucose, galactose, fructose
Carbohydrates are absorbed in their monosaccharide form. The monosaccharides are glucose, galactose and fructose. Glucose and galactose are absorbed across the luminal membrane by a SGLT-1 (sodium glucose transporter #1) and fructose by a GLUT 5 transporter.
77
77. Which one of the following statement about bile salts are INCORRECT?
A) Bile salts are produced by the conjugation of bile acids
B) Bile salts are reabsorbed in the terminal jejunum
C) Bile salts are recycled through the enterohepatic circulation
D) They aid in the emulsification of fats
B) Bile salts are reabsorbed in the terminal jejunum
Bile salts are reabsorbed in the terminal ILEUM and recycled to be excreted in the bile again.
78
78. Amylase breaks down
A) Carbohydrates
B) Proteins
C) Lipids
D) Nucleic Acids
a) Carbohydrates
Proteases or peptidases break down proteins and lipases break down lipids.
79
79. Starch is a:
A. polymer of glucose and fructose molecules
B. polymer of glucose molecules
C. chain of amino acids
B. polymer of glucose molecules
Starch is made up of glucose molecules which are cleaved into smaller fragments by amylase.
80
80. Pepsin comes from
A) goblet cells
B) parietal cells
C) ECL cells
D) Pepsinogen
D) Pepsinogen
Pepsinogen is secreted by chief cells and is the precursor of pepsin
81
81. The enterocytes lining the villi of the small intestine contain the following brush border enzymes:
A) lactase, sucrase, maltase, dextrinase
B) fructase, sucrase, maltase, lactase
C) galactase, fructase, sucrase, alpha-limit dextrinase
D) lactase, maltase, fructase
A) lactase, sucrase, maltase, dextrinase
Lactase to breakdown lactose to glucose and galactose; sucrase to breakdown sucrose to glucose and fructose; maltase to breakdown maltose and malt-triose into glucose molecules, and alpha-limit dextrinase to breakdown small chains of glucose molecules into individual glucose molecules.
82
82. Pepsin would be active at the following pH:
A) 12
B) 9
C) 6
D) 3
D) 3
Pepsin is most active in an acidic environment - pH around 2-3 is a favourite and above 5 just doesn't cut it.
83
83. Choose the INCORRECT statement. In the small intestine:
A. motility ceases when the extrinsic nerves to the intestine are cut
B. vitamin B12 is absorbed
C. the final digestion of disaccharides into monosaccharides takes place
D. absorption of chloride of ions take place mostly by passive diffusion
Option A is incorrect as motility persists after extrinsic denervation - the enteric nervous system can regulate this.
Vitamin B12 is absorbed in the terminal ileum. Disaccharides are broken down into monosaccharides by the brush border.
Disaccharidases & chloride absorption is mostly passive following sodium ions which are actively absorbed.
84
84. SAQ: Why are proton pump inhibitors the most effective treatment for gastric reflux? (10 marks/10 minutes)
Using a diagram would be fine here.
1. Proton pumps are found on the luminal membrane of the parietal cells in the oxyntic mucosa of the stomach.
2. The activity of the proton pump is related to the amount of acid produced in the stomach. The protons are matched with chloride ions producing HCL.
3. There are two intracellular pathways that can stimulate acid production – stimulation of the proton pump being the final step in both these processes.
4. The two intracellular pathways comprise: A – the calcium pathway and B the cAMP pathway
5. Increased intracellular calcium (from increased intracellular release and increased influx) combines with calmodulin forming a complex which stimulates the proton pump
6. Increased cAMP combines with Protein Kinase A forming a complex which stimulates the proton pump
7. Histamine stimulates acid secretion via the cAMP pathway
8. Acetylcholine stimulates acid secretion via the calcium pathway (when directly stimulating the parietal cell) or via the cAMP pathway when indirectly stimulating the parietal cell through the ECL cell.
9. Current therapies for treating gastric reflux include inhibiting the cAMP pathway using H2 receptor antagonists (e.g. ranitidine and cimetidine)
10. Or inhibiting vagal stimulation of the parietal cell (inhibiting the calcium pathway) or of the ECL cell (inhibiting the cAMP pathway) – by the use of atropine.
11. Because proton pump inhibitors block both the calcium and cAMP pathways and therefore direct and indirect stimulation of gastric acid secretion, they are more effective than a therapy that inhibits one pathway alone.
These types of statements or any others that are relevant and correct would attract a mark each up to a total of 10 marks. Point 11 is the most important point here and would attract 2 marks if you have both parts of that point – that is blocks both pathways (1 mark) and that therefore is more effective than inhibition of a single pathway (1 mark).
85
85. Absorption of nutrients takes place mainly in the
A. stomach
B. small intestine
C. large intestine
D. mouth
B. small intestine
Very little absorption occurs in the mouth or stomach. Mostly all occurs in the small intestine and really just absorption of water and electrolytes in the large intestine. And yes I take the point of my swatty student regarding separating digestion and absorption - some digestion occurs in the stomach but mainly mechanical. But point taken I will distinguish the processes in future.
86
86. The volume of fluid and secretions entering the small intestine is ______________ the volume of fluid leaving the small intestine
A) less than
B) greater than
C) equal to
B) greater than
In total about 9 litres enters the small intestine (including the succus entericus) and only about 2 litres continues on to the large intestine - on average.
87
87. Absorption of water in the small intestine occurs in the _________ driven mostly by the absorption of _______ions whilst secretion occurs in the __________ driven mostly by the secretion of ______________ ions.
A. villi, bicarbonate, crypts, chloride
B. surface epithelial cells, sodium, villi, chloride
C. villi, sodium, surface epithelial cells, bicarbonate
D. villi, sodium, crypts, bicarbonate
E. villi, sodium, crypts, chloride
E. villi, sodium, crypts, chloride
Absorption occurs in the villi driven by the movement of sodium across the luminal membrane (secondary active transport) primarily driven by the sodium-potassium pump on the basolateral membrane. Secretion occurs in the crypts mostly driven by the loss of chloride through channels in the luminal membrane
88
88. Which of the following transporters or channels involved in sodium absorption will be more active in the digestive phase?
A. ENaC (epithelial sodium channels)
B. sodium hydrogen exchangers
C. SGLT1
D. chloride bicarbonate exchangers
C. SGLT1
After eating, the transporters that carry (cotransport) products of digestion will be more active - the sodium GLUCOSE cotransporter SGLT1 and the sodium amino acid cotransporters
89
89. Which of the following is not a function of acid in the stomach?
```
A. helps sterilize stomach contents
B. aids formation of IF-Vit B12 complex
C. activates pepsinogen
D. denatures proteins
E. liberates vitamin B12 from food
```
B. aids formation of IF-Vit B12 complex
Intrinsic factor and vitamin B12 do not complex in the stomach but B12 complexes with HAPTOCORRIN in this acidic environment
90
90. Which of the following is unlikely to cause diarrhoea?
```
A. infection causes loss of villi
B. removal of a large segment of small intestine
C. high levels of somatostatin
D. increased intestinal motility
E. lactose intolerance
```
C. high levels of somatostatin
Somatostatin is an absorptagogue and stimulates intestinal absorption - thereby increasing the chance of constipation not diarrhoea. Remember D cells are found in many parts of the GIT - in the pancreas and the small intestine AND in the antrum/pylorus of the stomach.
91
91. (*advanced) The combination of sodium hydrogen exchangers with chloride bicarbonate exchangers is likely to produce the following effect in the small intestine:
A. absorption of NaCl
B. absorption of NaHCO3
C. secretion of chloride
D. secretion of sodium
A. absorption of NaCl
By adding the chloride-bicarbonate exchanger to the sodium hydrogen exchanger the absorption of ions across the epithelial cell changes from mostly sodium bicarbonate to sodium chloride
(Idk if this pattern follows all the time for exchanges: but first molecule in, second molecule out, i.e. sodium-hydrogen exchanger: sodium in, hydrogen out, or e.g. chloride-bicarbonate: chloride in, bicarbonate out.)
92
92. Absorption of dietary fat:
A. occurs normally if the intestine contains lipase but not bile salts
B. occurs mainly in the terminal ileum
C. must occur normally for adequate absorption of vitamins A, D, and K
D. is not affected by pathological (caused by some pathology and therefore very large) increases in gastric acid production
C. must occur normally for adequate absorption of vitamins A, D, and K
Both lipase and bile salts are required for normal absorption of dietary fat. Absorption of fats normally occurs in the JEJUNUM. Very large increases in gastric acid secretion increase the acidity in the duodenum and can affect (can inactivate) the pancreatic lipases which work best at more neutral/alkaline pHs.
93
93. SAQ: Explain why bacon and eggs will empty more slowly from the stomach than Gatorade (10 marks/10 mins).
* indicates 0.5 marks
B & E => solid*, lots of fat & protein *
Gatorade => liquid* & isotonic*
Foods must be chyme - liquid mush to be able to leave stomach*
Gatorade already liquid but B&E needs to be churned up first* (stomach digestive actions - acid, grinding *etc)
Gastric emptying regulated* by hormones* and short*/long* reflexes
Things that affect rate of leaving stomach:fat content*, protein content*, tonicity*
Increased fat or protein SLOWS gastric emptying* - feedback* thing due to hormones and stuff in the duodenum*
B&E higher osmolarity* and more volume* also feedsback to slow stomach
Tonicity that's not isotonic - either hypo* or hyper* will slow gastric emptying
B&E due to high fat and protein will stimulate receptors in duodenum feeding back to slow the stomach emptying (think it might be CCK*)
Gatorade sails through - liquid and isotonic
94
94. Choose the INCORRECT statement.
A. Auerbach's plexus is concentrated within the muscularis externa
B. Meissner's plexus primarily controls the tone and frequency of motility patterns in the gastrointestinal tract
C. The myenteric plexus contains post-ganglionic fibres of the parasympathetic nervous system
D. The submucosal plexus supports the functions of absorption and secretion at the mucosal surface.
B. Meissner's plexus primarily controls the tone and frequency of motility patterns in the gastrointestinal tract
Auerbach's plexus also called the myenteric plexus is concentrated between the inner circular and outer longitudinal muscle layers of the muscularis externa. As the nerves here are close to the major muscle layers that primarily support their function in terms of tone, rate or frequency of contraction etc. Meissner's plexus (also called the submucosal plexus) is found in the submucosal layer and supports the functions of digestion and absorption at the mucosal surface. As the enteric nervous system is found in the gastrointestinal wall, it is comprised of the nerves in these plexuses. The parasympathetic nervous system has long preganglionic (not postganglionic) fibres which synapse close to or within the target organ. In this case they synapse within the enteric nervous system so the postganglionic fibres of the PNS are part of the ENS including the myenteric and submucosal plexuses.
95
95. When chyme moves from the stomach to the duodenum:
A. Gastric secretion stops
B. Gastric secretion returns to its baseline "interdigestive" level
C. Gastric secretion continues, but only if the vagi are intact
D. Gastric secretion continues, but at a reduced rate which is relative to the amount of chyme left in the small intestine
D. Gastric secretion continues, but at a reduced rate which is relative to the amount of chyme left in the small intestine
Gastric secretion will reduce when chyme moves from the stomach to the duodenum as there is feedback to the stomach slowing motility and secretions - this is the 'intestinal phase' of secretion. Interdigestive levels of secretion will occur when there is no food left in the small intestine. Gastric secretion can continue without the influence of the vagi especially in the intestinal phase as this is controlled mostly by enteroendocrine hormone levels.
96
96. The basic mechanism of digestion in the intestines is:
```
A. transamination
B. oxidation
C. reduction
D. hydrolysis
E. deamination
```
D. hydrolysis
Digestion is the breakdown of foodstuffs occurring with the addition of water (and an enzyme)
97
97. Primary peristalsis and secondary peristalsis of the esophagus are differentiated in that the former:
A. is initiated by swallowing
B. is more rapid
C. is dependent on neural control
D. is confined to the upper esophagus
A. is initiated by swallowing
Primary peristalis is initiated when food is thrown to the back of the throat and swallowed. Secondary peristalsis is initiated by the distension caused by the bolus lodged in the esophagus. Primary and secondary peristalis occur at the same rate, are under neural control and occur along the length of the esophagus.
98
98. The principal function of the ileocecal valve is
A. facilitate the storage of chyme in the ileum
B. prevent the reflux of fecal contents
C. prevent the entry of chyme into the appendix
D. none of the above
B. prevent the reflux of fecal contents
99
99. Emptying of the gallbladder is regulated by:
A. hormonal control of the sphincter of Oddi
B. hormonal control of the muscular wall of the gall bladder
C. the rate of bile secretion
D. vagal control of the sphincter of Oddi
B. hormonal control of the muscular wall of the gall bladder
The gall bladder empties when the muscles in the wall of the gall bladder contract. Bile will empty into the duodenum if the sphincter of Oddi is relaxed. Cholecystokinin (CCK) causes contraction of the gall bladder and relaxation of the sphincter of Oddi.
100
100. Which of the following is not a fat-soluble vitamin?
A. A
B. D
C. C
D. K
C. C
A, D, E and K are the fat soluble vitamins. In the diet they are dissolved in fats. Therefore they require adequate fat digestion to allow for their absorption. If the fats are not digested and consequently are not absorbed then the fat soluble vitamins will be lost in the faeces.
101
101. SAQ: List possible physiological consequences (symptoms/signs etc) of having a gastrinoma - a tumour which secretes very high levels of gastrin. Give your reasons. (10 marks/10 minutes)
There are probably quite a few answers here I haven't thought of however as long as they are correct and relevant you will earn marks. I have given 8 examples of answers but I wouldn't expect to get that many. I would give 0.5 marks for naming the symptom or sign and then 1.5 => 2 marks for the explanation depending on how many steps or details there are in the explanation. All this up to a maximum of 10 marks.
Symptom/sign then Physiological Reason/Mechanisms given for each point below.
1. Gastric ulcer/s Due to high Gastrin levels => increased gastric acid production overwhelming the protective mucus layer and causing erosive damage to the mucosa
2. Duodenal ulcer/s As above => high gastrin => high acid production => very acidic chyme may overwhelm neutralizing mechanisms in the duodenum with erosion of the mucosa and ulcer formation
3. Fat in the stools Increased acid production overwhelming neutralising mechanisms within the duodenum => causing lipases to be inactivated (they work at more neutral pH) => maldigestion of fats => fat appears in stools
4. Alkaline blood Magnitude of the alkaline tide is relative to acid production. If acid production outstrips bicarbonate secretion in the bile, pancreatic secretions and Brunner's glands etc. then the blood will be relatively more alkaline
5. Vitamin B12 deficiency Vitamin B12 is absorbed as a complex with intrinsic factor. This complex forms when the vitamin B12/haptocorrin complex dissociates by the action of pancreatic enzymes (these may be inactivated in the more acidic environment) and the B12/IF complex forms in the more alkaline environment so this may not occur. No complex formation => no B12 absorption.
6. Reflux (oesophagal erosion) Increased acid production => regurgitates through lower oesophagal sphincter causing erosion of the oesophagal mucosa or at the least “heartburn” and symptoms of reflux (burning sensation in chest)
7. High somatostatin levels In response to increased acid production => high levels of somatostatin which may decrease motility and intestinal fluid secretion in other parts of the GIT
8. Abdominal cramping Gastrinoma => increased gastrin levels =>Gastrin is involved in the gastroileal reflex causing increased motility in the ileum
102
102. Slow waves are
A. undulating waves of spontaneous depolarization and repolarization which occur in the smooth muscle in the gastrointestinal wall
B. action potentials
C. responsible for the contractions of the muscularis externa
D. have frequencies between 20 and 50 per minutes
A. undulating waves of spontaneous depolarization and repolarization which occur in the smooth muscle in the gastrointestinal wall
slow waves are a resting potential which doesn't rest but spontaneously depolarizes and repolarizes. The frequency of the slow waves is dependent on the section of the GIT and ranges from around 3-5 in the stomach to about 10-12 in the small intestine. Action potentials (and muscle contractions) may be generated when the slow wave reaches threshold.
103
103. Mass movement is
A. a single vigorous, multihaustral, peristaltic contraction and relaxation of the intestine
B. a local, non-propogated contraction and relaxation of the intestine
C. dilation of the intestinal lumen
D. most common in small intestine
A. a single vigorous, multihaustral, peristaltic contraction and relaxation of the intestine
Mass movements cause fecal matter to be moved along the large intestine by a vigorous peristaltic wave contracting and relaxing the large intestine. Local, non-propogating contractions would best describe segmentation.
104
104. Feed-forward mechanisms are associated with
A. increased sphincter tone
B. decreased sphincter tone
C. no change in sphincter tone
B. decreased sphincter tone
Feed-forward reflexes are preparing the way for foodstuffs that are coming. In effect therefore they clear the way by increasing motility and relaxing the relevant sphincter so that matter can be moved on in preparation for the meal to come.
105
105. Choose the INCORRECT statement. Gastric secretions
A. increase when a hungry person sees and smells food
B. increase in response to the presence of food in the mouth
C. contain a substance which aids the absorption of vitamin B12
D. cannot digest gastric mucosal cells because the cell membrane contains a pepsin inactivator
D. cannot digest gastric mucosal cells because the cell membrane contain a pepsin inactivator
Gastric mucosal cells are protected by a mucus coating
106
106. In the large intestine
A. the major proportion of intestinal water is absorbed
B. sugars, fats and proteins are absorbed
C. marked peristalsis occurs in response to gastric filling
D. large amounts of water are secreted each day
C. marked peristalsis occurs in response to gastric filling
Most intestinal water is absorbed in the small (not large) intestine. The large intestine absorbs approximately 2 litres of water and salts each day (not sugars, fats or proteins which are absorbed in the small intestine). Very little secretion of water occurs in the large intestine - mucus is secreted. The gastro-colic reflex causing peristaltic contraction in the large intestine in response to filling of the stomach.
107
107. Phase II of the Migrating Motor Complex is associated with
A. maximal regular contractions over a short time period
B. irregular, non-maximal contractions
C. random contractions interspersed with periods of quiet
D. a quiet time with very little muscle activity
B. irregular, non-maximal contractions
Phase I is quiet, Phase II is irregular, non-maximal and Phase III is regular and maximal. The MMC occurs during fasting.
108
108. High salivary flow rates cause the final saliva solution to:
A. become more hypotonic compared to low salivary flow rates
B. to become saltier than low salivary flow rates
C. to become less alkaline than low salivary flow rates
D. contain more potassium than low salivary flow rates
B. to become saltier than low salivary flow rates
Modification of the initial salivary secretion entails reabsorption of Na and Cl and secretion of K and HCO3. The reabsorption occurs to a greater degree than does the secretion so the final solution become hypotonic. At high salivary flow rates this modification is limited and the final solution becomes more like plasma.
109
109. In the gastric phase, acid secretion is NOT stimulated by
A. long vagovagal reflexes
B. local enteric reflexes
C. secretions of S cells
D. secretions of G cells found in the antrum/pylorus
C. secretions of S cells
S cells secrete Secretin which is Nature's antacid - it inhibits acid secretion.
110
110. Which of the following is an exopeptidase?
A. Pepsin
B. Trypsin
C. Carboxypolypeptidase
D. Chymotrypsin
C. Carboxypolypeptidase
Exopeptidases cleave individual amino acids from the ends of polypeptides. Carboxypolypeptidase cleaves individual amino acids from the carboxyl ends of polypeptides. Trypsin and Chymotrypsin both split proteins into polypeptides. Pepsin initiates protein digestion breaking down proteins to peptones, proteoses and some polypeptides.
111
111. SAQ: Outline the physiological consequences of diarrhoea (10 marks/10 minutes)
1. Diarrhoea is excessive fluid in the stools
2. Loss of iso-osmotic fluid
3. Dehydration (Decreased extracellular fluid volume)
4. Decreased Blood volume
5. Decreased Blood pressure
6. Stimulation of the RAAS
7. Secretion of the large intestine include bicarbonate and potassium so this loss will be increased
8. Loss of bicarbonate => metabolic acidosis (2 marks)
9. Loss of potassium => hypokalemia (2 marks)
Points such as those in points 1 => 7 earn you 1 mark each and points 8 and 9 have two parts so 1 mark per part. All this and other relevant and accurate statements up to a total of 10 marks.
112
112. Which of the following is NOT found in saliva?
A. Lipase
B. Amylase
C. Protease
D. Mucus
C. Protease
There is always mucus in the GIT. Lingual lipase and salivary amylase.
113
113. To achieve the final pancreatic secretion exchange of which two ions takes place during ductal modification?
```
A. Na and Cl
B. K and Cl
C. HCO3 and Cl
D. Na and K
E. HCO3 and PO4
F. Na and HCO3
```
C. HCO3 and Cl
We take up CHLORIDE and secrete bicarbonate producing a bicarbonate rich pancreatic solution.
114
114. Which of the following gives the correct order of the gut wall layers starting innermost?
A. submucosa, muscularis externa, mucosa, serosa
B. mucosa, submucosa, muscularis externa, serosa
C. muscularis externa, mucosa, submucosa, serosa
D. serosa, muscularis externa, submucosa, mucosa
B. mucosa, submucosa, muscularis externa, serosa
115
115. Which of the following is NOT a mechanism stimulating acid secretion?
A. distention of the antrum => local ENS reflex
B. amino acids in stomach antrum => stimulating G cells
C. low pH in stomach => stimulating D cells
D. sight of food => stimulating vagal outflow
C. low pH in stomach => stimulating D cells
Stimulation of D cells increases somatostatin secretion which inhibits acid secretion
116
116. Which of the following does not relate to smooth muscle properties or function within the GIT?
A. unitary smooth muscle
B. functions as a syncytium
C. has gap junctions (low resistance pathways)
D. has a flat resting membrane potential
D. has a flat resting membrane potential
Smooth muscle in the gastrointestinal tract has a slow wave potential - undulating membrane potential which can generate action potentials when it reaches threshold
117
117. Which of the following has the lowest volume of secretion per day?
```
A. stomach
B. pancreas
C. liver
D. small intestine
E. large intestine
```
E. Large intestine
The large intestine secretes very small volumes per day - almost neglible and mostly mucus. The other options secrete quite large volumes - go check the lecture notes.
118
118. Which of the following occurs when parietal cells are stimulated?
A. tubulovesicles fuse with the luminal membrane
B. tubulovesicles are snipped off the luminal membrane
C. mitochrondrial activity decreases
D. luminal surface area decreases
A. tubulovesicles fuse with the luminal membrane
When parietal cells are stimulated, the tubulovesicles (containing proton pumps) fuse with the luminal membrane increasing its surface area and capacity for acid production. Acid production requires energy and mitochondrial activity would increase (not decrease).
119
119. Which of the following motility patterns is characteristic during fasting?
A. peristalsis
B. segmentation
C. mass movements
D. migrating motor complex
D. migrating motor complex
The MMC occurs during fasting and has three characteristic phases. It occurs approximately every 90 minutes starting at the stomach and continuing through to the ileum. The MMC can be disrupted by feeding.
120
120. Vitamin B12 absorption
A. is increased in patients who have had gastric bypass surgery
B. occurs in the duodenum
C. requires complex formation with bile salts
D. will decreased if acid production is decreased
D. will decreased if acid production is decreased
Vitamin B12 absorption requires formation of the VitB12/Intrinsic Factor complex. IF is secreted by parietal cells and under the same conditions as acid secretion. If acid secretion decreases, IF secretion will decrease and vitamin B12 absorption will decrease.
121
121. SAQ: List the steps involved in Vitamin B12 absorption and explain why a gastrectomy (removal of the stomach) would cause vitamin B12 deficiency. (10 marks/10 mins)
There are two sections to the question – listing the steps involved then explaining the deficiency.
The list is worth 6 marks (any of the following statements or other accurate and relevant statements would earn you a mark up to total of 6)
1. Consume food containing B12
2. Liberate B12 from food (action of acid)
3. B12 combines with haptocorrin in stomach
4. IF secreted into stomach and travel to SI
5. B12/haptocorrin complex travels to SI where is breaks up due to pancreatic enzyme action
6. B12 and IF form complex in SI (less acidic environment favours this)
7. B12/IF complex absorbed in the terminal ileum
The explanation is work 4 marks (any of the following statements or other accurate and relevant statements would earn you a mark up to total of 4)
• Gastrectomy removes the stomach and therefore removes acid, gastric haptocorrin and IF.
• Lack of acid decreases digestion of VitB12 food
• Lack of IF means no formation of Vit B12/IF complex
• No complex – no absorption -> deficiency.
122
122. SAQ: List the steps in protein digestion (10 marks/10 minutes)
SAQ: List the steps in protein digestion (10 marks/10 minutes)
1. Three possible stages to protein digestion: luminal/brush border (membrane) and cellular
2. Ingest protein
3. HCl denatures proteins in stomach
4. Pepsinogen => pepsin in presence of HCl in stomach
5. Pepsin (endopeptidase) breaks down proteins to small peptide chains
6. Chyme enters duodenum and protein content stimulates release of CCK from I cells
7. CCK stimulates release of pancreatic digestive enzymes including inactive proteases (could list them here)
8. Trypsinogen converted to trypsin by brushborder enterokinase/enteropeptidase
9. Trypsin then activates other proteases (could give details e.g. chymotrypsinogen=> chymotrypsin etc.
10. Pancreatic protease action peptides=> amino acids, di- and tri-peptides
11. Smaller peptide chains acted on by brush border peptidases
12. Absorption via luminal Na/AA symporter
13. Some cellular digestion by di- and tri-peptidases
Any of these would earn you a mark (yes even #2) and any other accurate and relevant statements. It would be a good idea to list the steps in lipid and carbohydrate digestion also and know these (not as the answer to this question obviously but for your revision). Which bits of the digestion occurs in each phase? Cephalic, gastric and intestinal????
