GI Flashcards
Regulating gastric acid secretion: What stimuli are involved in the intestinal phase?
Low pH in duodenal lumen, duodenal distension, presence of amino acids and fatty acids in the duodenum.
What cells secrete histamine?
Enterochromaffin like cells.
What are the consequences of vitamin A deficiency?
Night blindness, growth retardation, increased susceptibility to infection.
Name 2 ions that striated ducts reabsorb.
Na+ and Cl-
What enzyme is needed for fat digestion?
Pancreatic lipase.
What is the function of micelles?
They are lipid transport systems. They move to the epithelial brush border and release the fatty acids and monoglycerides for absorption.
What is the anterior layer of rectus sheath formed from?
External oblique aponeurosis and the anterior lamina of the internal oblique aponeurosis.
Is stage 3 of swallowing voluntary or involuntary?
Involuntary.
How do amino acids get absorbed into the blood?
Passive diffusion.
What is the mechanism for Cl- and HCO3- reabsorption?
Cl- is actively reabsorbed in exchage for HCO3-. The intestinal contents therefore become more alkaline.
Define malnutrition.
A lack of nutrition due to not eating enough, being unable to absorb nutrients, eating the wrong things.
Is vitamin A fat or water soluble?
Fat soluble.
What is the function of the muscles of the soft palate in swallowing?
They act to tense and elevate the soft palate.
If water input is 9L, how much is reabsorbed and how much is excreted in the faeces?
8.8L is reabsorbed and 0.2L is excreted in the faeces.
What molecule is produced that aids absorption?
Micelles.
How many pharyngeal arches are there?
5 (4 pharyngeal clefts and pouches).
Name the 4 main defence mechanisms against gastric acid secretion.
- Alkaline mucous.
- Tight junctions between epithelial cells.
- Replacing damaged cells.
- Feedback loops.
What is the recommended daily intake of vitamin A for men and women?
Women - 600µg. Men - 700µg.
What is the function of the muscles of the floor of the mouth in swallowing?
They raise the hyoid bone and larynx.
What are the end products of starch digestion?
Maltose!
Also maltotriose, glucose polymers and alpha-dextrins.
What happens in stage 2 of swallowing?
The nasopharynx closes off due to soft palate elevation. The trachea is closed off by the epiglottis. Elevation of the hyoid bone shortens and widens the pharynx.
How does Na+ move across the small intestine?
Na+ is actively transported from the lumen by pumps located in the cell membranes in the ileum and jejunum.
At what vertebral level is the intertubercular plane?
L4.
Where are the stem cells that replace the epithelium located?
The base of crypts.
On average, how much gastric acid do we secrete a day?
2L
What does the first pharyngeal arch form?
Muscles for mastication. Innervation: Cn 5.
What is the epithelium lining of interlobular ducts?
Simple columnar epithelium.
How long do lipid stores in a 70Kg adult last?
3 months.
Name 2 areas of the body with a low pH to combat bacteria.
Stomach and vagina.
What are the 5 stages of midgut development?
- Elongation.
- Herniation.
- Rotation.
- Retraction.
- Fixation.
Name 3 sources of vitamin A.
- Oily fish.
- Dairy.
- Liver
What fuels does the brain use?
Glucose and ketone bodies.
What can cause pernicious anaemia?
If you have low levels of intrinsic factor you will have B12 deficiency. This will mean fewer RBC’s will be formed leading to pernicious anaemia.
What is the precursor molecule for pepsin?
Pepsinogen.
What are the 4 layers of the GI tract?
- An innermost mucosa.
- A sub-mucosa.
- An external muscle coat (muscularis externa)
- A serosa.
Why is pepsin action terminated in the small intestine?
The pH in the small intestine is too alkaline and so it denatures.
What digests lipids in the small intestine?
Pancreatic lipases.
Is saliva hypotonic or hypertonic?
Hypotonic - water reabsorption and ion secretion.
What happens in stage 3 of swallowing?
The pharyngeal constrictor muscles sequentially contract producing peristaltic waves. This propels the bolus of food down the Oesophagus. This is followed by depression of the hyoid bone.
Where in the layers of the GI tract would Auerbach’s plexus be found?
In the muscularis externa between the circular and longitudinal layers of muscle.
Do parotid glands have mainly serous or mainly mucous acini?
Mainly serous acini.
What substances emulsify lipids?
Bile salts and phospholipids.
Give 4 complications of malnutrition.
- Apathy.
- Depression.
- Increased risk of infection.
- Anaemia.
Do sublingual glands have mainly serous or mainly mucous acini?
Mainly mucous acini.
What ions are reabsorbed at striated ducts?
Na+ and Cl-
What enzyme(s) hydrolyse cholesterol esters in the intestinal lumen?
Pancreatic esterases.
Why is endoscopy preferred to a barium meal?
Produces a better image and is more accurate. Also prevents exposure to radiation as a barium meal requires an X-ray.
What happens to the posterior rectus sheath below the arcuate line?
It is absent. The rectus abdominis is in direct contact with the transversalis fascia.
What is the function of mixed micelles?
Lipid transport systems.
Give 2 examples of an endopeptidase.
- Trypsin.
2. Chymotrypsin.
What happens in the retraction stage of midgut development?
In the 10th week the herniated midgut returns into the expanded abdominal cavity. Th jejunum is first to return.
How many B vitamins are there?
8.
The end products of fat digestion combine with bile salts and cholesterol to form what?
Mixed micelles.
Name 4 molecules to make up micelles.
- Fatty acids.
- Monoglycerides.
- Bile salts.
- Phospholipids.
Name 3 monosaccharides.
- Glucose.
- Fructose.
- Galactose.
What is the arcuate line?
The lower limit of the posterior rectus sheath.
Histamine is secreted by enterchromaffin like cells. What are enterochromaffin cells?
Enterchromaffin cells are located in the intestine and secrete serotonin, not histamine.
Define ulcer.
A breach in a mucosal surface.
What are the pacemaker cells of the small intestine called?
Interstitial cells of Cajal.
At what vertebral level is the subcostal plane?
L2.
Name 2 drugs that can be used to reduce gastric acid secretion.
- Proton pump inhibitors.
2. H2 receptor antagonists.
What are the axis of stomach rotation?
Longitudinal and anteroposterior.
What enzyme(s) hydrolyse peptide bonds in the stomach?
Pepsins.
Does parasympathetic innervation stimulate or inhibit salivary secretion?
Stimulates.
What mechanism speeds up the digestion of fats?
Emulsification - the surface area for lipase action is increased.
What is the importance of HCO3- being exchanged for Cl-?
HCO3- moving out of the cell increases the rate of the forward reaction and so more H+ are produced. Cl- moving into the cell then moves into the stomach lumen via Cl- channels and combines with H+ to form HCl.
What is the optimum oral pH?
7.2
Give 3 functions of HCl in the stomach.
- Solubilisation of food particles.
- Kills microbes.
- Activates pepsinogen forming pepsin.
What happens in the elongation stage of midgut development?
Rapid elongation forms the primary intestinal loop. The proximal part of the loop forms the small intestine and the distal part forms the large intestine up to 2/3 TC.
What are the 4 phases important in regulating gastric acid secretion? Do these phases turn secretion on or off?
- Cephalic phase - turning ON.
- Gastric phase - turning ON.
- Gastric phase - turning OFF.
- Intestinal phase - turning OFF.
What are the consequences of vitamin A toxicity?
Anorexia, vomiting, headache, reduced bone density, conjunctivitis.
Name 5 factors that can decrease the strength of peristaltic contractions.
- Duodenal distension.
- Low pH in duodenum lumen.
- Increased duodenal osmolarity.
- Increased sympathetic action.
- Decreased parasympathetic action.
What nerve passes through the parotid gland but does not innervate it?
The facial nerve (Cn 7) gives rise to its 5 terminal branches in the parotid gland.
Are lipids hydrophobic or hydrophilic?
Hydrophobic.
What are proteins digested into?
Dipeptides, tripeptides and amino acids.
Inside the intestinal epithelial cell, triglycerides combine with other lipids e.g. cholesterol to form what molecules?
Chylomicrons.
Name 2 ions that striated ducts secrete.
K+ and HCO3-
Why are fatty acids and monoglycerides re-synthesised into triglycerides inside the epithelial cell?
To maintain a diffusion gradient allowing for further reabsorption.
Where does the midgut begin and end?
Major duodenal papilla to 2/3 along the TC. (In embryo - liver bud to 2/3 along TC).
What is the importance of the striated duct basal membrane being highly folded?
It is folded into microvilli for the active transport of HCO3- against its concentration gradient.
Why might an elderly person be at risk of malnutrition?
- Immobility - unable to cook and eat.
- Dental problems meaning its difficult to chew foods.
- Decreased appetite.
- Not eating the right things.
What happens to the fatty acids and monoglycerides inside the intestinal epithelial cells?
They are re-synthesised into triglycerides in the smooth ER.
What is the mechanism of the H+/K+ ATPase proton pump?
It pumps H+ into the stomach lumen and K+ into the parietal cell.
What are the functions of vitamin C?
Synthesis of collagen, neurotransmitters and carnitine. It has an antioxidant ability and can absorb non-haem iron.
What can cause Barrett’s oesophagus?
GORD.
At what vertebral level is the intercristal plane?
L4/5.
Briefly describe the cephalic phase.
The parasympathetic nervous system is triggered by stimuli. This releases Ach. Ach acts on parietal cells and on gastrin and histamine. HCl secretion increases.
What ions are exchanged on the side of the parietal cell in contact with the capillaries?
Cl- is pumped into the parietal cell and HCO3- moves out of the parietal cell into the capillary.
Which papillae do not bear taste buds?
Filiform papillae.
Are serous acini dark staining or pale staining on a histological slide?
Dark staining.
Mucus acini = pale staining
What is the parasympathetic innervation of the Parotid gland?
Cn 9 - glossopharyngeal.
What is the cause of lactose intolerance?
A deficiency in lactase.
Name 3 organs that secrete digestive enzymes.
- Stomach.
- Pancreas.
- Salivary glands.
What is the parasympathetic innervation of the Sublingual gland?
Cn 7 - facial.
What protein binds pancreatic lipase to the surface of the lipid?
Co-lipase. This is essential, pancreatic lipase can not work without it.
What ducts do striated ducts lead on to?
Interlobular (excretory) ducts.
What neurotransmitter is involved in regulating gastric acid secretion?
Ach.
What molecules make up phospholipids?
1 glycerol backbone, 2 fatty acids and 1 phosphate group.
What is mucous acini secretion composed of?
Mucin - needed for lubrication.
Why is the pyloric sphincter closed as the peristaltic wave reaches it?
This prevents chyme entering the duodenum and so the gastric contents are forced back and mixed together in the body of the stomach.
What artery ascends through the parotid gland?
The external carotid artery.
What envelopes the rectus abdominis above the arcuate line?
It is enveloped by the internal oblique aponeurosis.
Where does Cl- and HCO3- reabsorption mainly take place?
In the ileum and colon.
What muscles contributes to the upper oesophageal sphincter?
Cricopharyngeus.
What does the ventral mesentery become?
The lesser omentum.
What is the advantage of emulsifying lipids?
It increases the SA for digestion and so digestion is more efficient.
Why does the left vagus nerve become the anterior vagal trunk and the right vagus become the posterior vagal trunk?
Due to the 90 degrees clockwise rotation of the stomach in its longitudinal axis.
Are the pharyngeal clefts formed in the endoderm or ectoderm?
Ectoderm.
What enzyme(s) further break down peptides in the small intestine?
Pancreatic proteases.
What is the recommended daily intake of vitamin C?
40mg.
What is the intertubercular plane?
A line that joins the tubercles of the iliac crests.
What happens in fixation of midgut organs?
This is when some regions of the gut lose their dorsal mesentery. These regions become retroperitoneal.
Where does the majority of complex polysaccharide digestion occur?
In the large intestine via gut bacteria.
What are the end products of fat digestion?
Free fatty acids and monoglycerides.
Give 4 risk factors for GORD.
- Obesity.
- Pregnancy.
- Hiatal hernia.
- Smoking.
(Sedentary lifestyle is not a risk factor).
What cells secrete Gastrin?
Enteroendocrine cells / G cells.
Briefly describe the gastric ON phase.
Gastrin is released in response to the stimuli. This acts on parietal cells and triggers release of histamine (histamine then acts on parietal cells too). HCl secretion increases.
What is the pH range of saliva?
6.2 - 7.4
Where in the layers of the GI tract would Meissner’s plexus be found?
In the submucosa.
Regulating gastric acid secretion: What stimuli are involved in the gastric OFF phase?
Low pH in gastric lumen.
What fuels does muscle use?
Glucose, ketone bodies, amino acids and triacylglycerol.
Name 3 disaccharides.
- Sucrose (glucose and fructose).
- Lactose (glucose and galactose).
- Maltose (glucose and glucose).
Is stage 1 of swallowing voluntary or involuntary?
Voluntary.
What does the dorsal mesentery become?
The greater omentum.
What happens in the rotation stage of midgut development?
The elongated intestinal loop rotates 270 degrees anticlockwise.
What are the consequences of vitamin C deficiency?
Weakness, shortness of breath, aching, bleeding gums, thickening of skin.
By what process are the products of protein digestion absorbed into the intestinal epithelial cells?
Secondary active transport coupled to H+ or Na+.
What vertebral level does the umbilicus mark when lying down?
L3.
What is the function of the Vagus nerve in regards to parietal cells?
The vagus nerve stimulates the release of Ach which then acts on the parietal cells to increase HCl production.
What emulsifies lipids?
Bile salts.
Which of the main salivary glands is constantly active?
Submandibular.
What hormone is involved in regulating gastric acid secretion?
Gastrin.
What activates pepsinogen?
Low pH.
What cells secrete somatostatin?
D cells.
What are free sugars and starch associated with effecting?
They can cause shifts in blood glucose and insulin due to their rapid absorption. This can strain the pancreas.
Briefly describe the gastric OFF phase.
Gastrin is inhibited in response to stimuli and histamine is therefore indirectly inhibited. Somatostatin is also released and this inhibits parietal cells. HCl secretion decreases.
What does the sixth pharyngeal arch form?
Intrinsic muscles of the Larynx. Innervation: Recurrent laryngeal nerve (Cn 10).
What are the 2 types of pancreatic proteases?
- Endopeptidases.
2. Exopeptidases.
What type of starch is the most desirable and why?
Slowly digestible starch. It is slowly digested and absorbed and so has little influence on blood glucose and insulin.
How does K+ move across the small intestine?
Via passive diffusion. Movement is determined by the potential difference between lumen and capillaries.
What happens in the herniation stage of midgut development?
The rapid growth of the intestinal loop means it is pushed into the extra embryonic cavity in the umbilical cord.
What triglyceride bonds is pancreatic lipase able to hydrolyse with ease?
1 and 3 bonds (the 2 bond is hydrolysed at a slower rate).
Describe 2 ways in which the transpyloric plane can be drawn.
- The midpoint between the suprasternal notch and the pubic symphysis.
- Connects the two points marked by the insertion of the rectus sheath into the costal margin.
What is the epithelium lining of intercalated ducts?
Simple cuboidal epithelium.
What is the innermost mucosa layer composed of?
- A folded epithelium.
- Lamina propria (connective tissue).
- Muscularis mucosa (ring of smooth muscle).
What are triglycerides broken down into?
Monoglycerides and 3 fatty acids.
Name 2 factors that can increase the strength of peristaltic contractions.
- Gastrin.
2. Gastric distension.
What does the fourth pharyngeal arch form?
Cricothyroid muscle. Innervation: External branch of superior laryngeal nerve (Cn 10).
What enzyme anchors lipase to the surface of an emulsified lipid droplet?
Colipase.
How does water move across the small intestine?
It moves freely by osmosis and also via aquaporins.
What clinical feature would you see in a patient with fat malabsorption?
Pale and smelly faeces.
Are the pharyngeal pouches formed in the endoderm or ectoderm?
Endoderm.
Name 6 muscles/groups of muscles that are involved in swallowing.
- Buccinator.
- Suprahyoids.
- Muscles of the palate.
- Muscles of the floor of the mouth.
- Infrahyoids.
- Pharyngeal constrictor muscles.
What is the intercristal plane?
It connects the highest points of the pelvis at the lower back.
On average, how many peristaltic waves are there a minute?
3 (slow repol/depol cycles).
Regulating gastric acid secretion: What stimuli are involved in the gastric ON phase?
Gastric distension, presence of peptides and amino acids in the stomach.
What do parietal cells secrete?
HCl and intrinsic factor.
Where does the H+ come from in gastric acid?
In parietal cells: H2O + CO2 = HCO3- + H+
What is the optimum pH for pepsins?
1.6-3.2
Name 2 diseases that can cause malabsorption.
- Crohn’s disease - loss of plicae circulares.
2. Coeliac disease - vili atrophy.
Regulating gastric acid secretion: What stimuli are involved in the cephalic phase?
Sight, smell, taste of food. Chewing.
Do submandibular glands have mainly serous or mainly mucous acini?
They have serous and mucus acini.
What is the function of the infrahyoids?
To depress the hyoid bone and larynx.
Where is the first site of starch digestion?
In the mouth via salivary amylase.
Briefly describe the intestinal phase.
The enterogastrones secretin and CCK are released in response to stimuli. Secretin inhibits gastrin and stimulates further somatostatin release. HCl secretion decreases.
Why are fatty acids and monoglycerides re-synthesised into triglycerides inside the intestinal epithelial cells?
To maintain the concentration gradient for further absorption of fatty acids and monoglycerides.
What is the function of the pharyngeal constrictor muscles?
They contract sequentially producing peristaltic waves which drive food into the oesophagus.
What is the hydrogen ion concentration of gastric acid?
> 150mM
What clinical feature would you see in a patient with protein malabsorption?
Swollen ankles.
What is refeeding syndrome?
Metabolic disturbances (hypokalemia, hypomagnesemia etc) that occur due to reinstitution of nutrition to patients who are starved/severley malnourished.
What are the functions of chylomicrons?
Chylomicrons move through the lymphatics and the blood stream to tissues.
Name the abdominal intraperitoneal organs.
Spleen, Small intestine, Appendix, Liver, Transverse colon, Stomach, Sigmoid colon.
What bonds does pancreatic amylase break?
alpha 1-4 linkages.
Why are the foregut, midgut and hindgut divisions different in the adult compared to in the embryo?
It changes due to the formation of the ampulla of vater.
What happens in stage 1 of swallowing?
Food is compressed against the roof of the mouth and is pushed to the oropharynx by the tongue.
Why does helicobacter pylori cause peptic ulcers?
Helicobacter pylori lives in gastric mucus. It secretes urease. Urease breaks into CO2 and NH3. The NH3 combines with H+ to form NH4+. NH4+ damages the gastric epithelium, an inflammatory response is triggered and mucosal defence is reduced.
What enzyme is responsible for protein digestion in the stomach?
Pepsin.
Explain the mechanism that produces the symptoms of lactose intolerance.
Lactose intolerance has an osmotic effect. H2O and fermentable sugars enter the the large intestine lumen and cause diarrhoea, bloating and pain.
What type of cells are secretin and CCK?
Enterogastrones.
What structure, visible microscopically, is primarily responsible for absorption?
Villi.
What does the second pharyngeal arch form?
Muscles for facial expression. Innervation: Cn 7.
Name 4 sources of vitamin C.
- Citrus fruits.
- Green leafy veg.
- Potatoes.
- Kidney.
What enzymes are responsible for protein digestion in the small intestine?
Pancreatic proteases.
Why is the stomach the shape it is?
Due to differences in growth rates. The greater curvature grows faster than the lesser curvature.
Where does the foregut begin and end?
Mouth to the major duodenal papilla. (In the embryo - oropharyngeal membrane to the liver bud).
Define BMR.
The energy needed to stay alive at rest, usually 24kcal/kg/day.
Give 3 symptoms of lactose intolerance.
- Bloating.
- Diarrhoea.
- Pain.
What is the optimum pH for pepsin action?
1.6 - 3.2
Is vitamin C fat or water soluble?
Water soluble (easily lost when boiled).
Name 3 physical tests for malnutrition.
- BMI.
- Amount of body fat.
- Height.
Where in the stomach are peristaltic contractions the most powerful?
In the gastric antrum.
What are the functions of vitamin A?
Vitamin A is needed for cellular growth and differentiation. It is also important for eyesight and lymphocyte production.
What does the third pharyngeal arch form?
Stylopharyngeus muscle. Innervation: Cn 9.
What is the maximum volume of the stomach?
1.5L
How long do glycogen stores in a 70Kg adult last?
About 12 hours.
Does the oesophagus have a serosa layer?
No!
What enterogastrones are involved in regulating gastric acid secretion?
Secretin and CCK.
Why might someone with enterocyte loss be unable to break down lactose?
Enterocytes at villi contain lactase. If the enterocytes are lost they may have lactase deficiency.
Is stage 2 of swallowing voluntary or involuntary?
Involuntary.
Name 4 factors that can affect the composition of saliva.
- Stimulus.
- Age.
- Gender.
- Drugs.
Are B vitamins fat or water soluble?
Water soluble.
Name 3 polysaccharides.
- Starch.
- Cellulose.
- Glycogen.
Name 3 physical mechanisms of absorption.
- Endocytosis.
- Diffusion/facilitated diffusion.
- Active transport.
Briefly describe starch digestion.
Begins in the mouth via salivary amylase. In the small intestine pancreatic amylases catalyse alpha 1-4 linkages forming maltose. The end products are further broken down by enzymes e.g. maltase on the luminal membrane; this forms monosaccharides. The products diffuse into the blood.
What paracrine factors are involved in regulating gastric acid secretion?
Histamine and Somatostatin.
Name 3 things that can cause peptic ulcers.
- Helicobacter pylori.
- NSAIDS.
- Chemical irritants.
What does pepsin break proteins into?
Peptide fragments.
Name 3 structures that cross the transpyloric plane.
- The pylorus of the stomach.
- The gall bladder.
- The pancreas.
What enzyme are parietal cells abundant in?
Carbonic anhydrase.
What are the consequences of vitamin C toxicity?
Diarrhoea, nausea, renal stone formation.
What is the serous layer composed of?
Composed of a simple squamous epithelium that covers the outside surface of the gut tube facing the peritoneal cavity.
Give 2 examples of an exopeptidase.
- Carboxypeptidases.
2. Aminopeptidases.
Which type of pancreatic protease can form monomers?
Exopeptidases.
Name 2 endocrine secretions from the duodenum?
- Secretin.
2. CCK.
Describe Barrett’s oesophagus.
When the stratified squamous oesophageal epithelium changes to a simple columnar one at the lower end of the oesophagus. This can be caused by prolonged acid reflux from the stomach.
What abdominal plane would you refer to when carrying out a lumbar puncture?
The intercristal plane. It joins the highest points of the pelvis posteriorly and marks the space between L4 and L5.
Where in the small intestine are bile salts absorbed?
Jejunum.
What is the function of endopeptidases?
They break peptide bonds between non-terminal amino acids.
Which muscle(s) manipulate food in chewing. Elevate the hyoid bone and flatten the floor of the mouth?
Buccinator and Suprahyoids.
What organelle is abundant in striated ducts and why?
Mitochondria. For the active transport of ions.
What is the function of exopeptidases?
They break peptide bonds between terminal amino acids and so form monomers.
Where does the hindgut begin and end?
Distal 1/3 of TC to anal canal. (In embryo - distal 1/3 of TC to cloacal membrane).
Why do NSAIDS cause peptic ulcers?
They inhibit cycle-oxygenase 1.
Cycle-oxygenase 1 is needed for prostaglandin synthesis, prostaglandins stimulate mucus secretion. Without cycle-oxygenase 1 there is less mucus and so the mucosal defence is reduced.
What percentage of BMR do these organs use?
a) Brain.
b) Liver.
c) Muscle.
a) 20%.
b) 21%.
c) 22%.
What are the 2 key stages for fat digestion?
- Emulsification.
2. Triglyceride hydrolysis.
Name the abdominal retroperitoneal organs.
Supradrenal glands, Aorta, IVC, Duodenum (except cap), Pancreas (except tail), Ureters, Colon (ascending and descending), Kidneys, Oesophagus, Rectum.
What is the parasympathetic innervation of the Submandibular gland?
Cn 7 - facial.
What is the volume of an empty stomach?
50ml
Where do peristaltic waves begin?
In the gastric body.
At what vertebral level is the transpyloric plane?
L1.
Where is the swallowing centre found?
Medulla oblongata.
What is the posterior layer of the rectus sheath formed from?
The posterior lamina of the internal oblique aponeurosis and the transversus abdominis aponeurosis.
What enzyme digests starch in the small intestine?
Pancreatic amylase.
How is vitamin B12 absorbed?
It binds to a protein, intrinsic factor. It is then absorbed in the terminal ileum via endocytosis.
What is the muscular externa composed of? What is its function?
Composed of 2 layers of smooth muscle: circular and longitudinal. Nerves that are part of the enteric nerve plexus are also present here (Aurebach’s plexus). Contraction of the muscle helps to break down and food and propel it along the GI tract.
What forms the anterior rectus sheath below the rectus abdominis?
The external oblique, internal oblique and transversus abdominis aponeurosis’ all form the anterior rectus sheath. There is no posterior rectus sheath.
What fuels does the liver use?
Glucose, amino acids, fatty acids.
What is the function of saliva?
It acts as a lubricant for chewing, swallowing and speech. It is important in oral hygiene; has a role in immunity, wash and it can also act as a buffer.
What are B vitamins important for?
Cell metabolism and energy production.
What is the subcostal plane?
A plane parallel to the lowest points of the costal margins.
What is the function of intercalated ducts?
They connect acini to larger striated ducts.
What connects the midgut to the yolk sac?
The Vitelline duct.
What is receptive relaxation?
Smooth muscle in the body and fundus of the stomach relaxes prior to the arrival of food, this allows the stomach volume to increase. There is afferent input from Cn 10. NO and serotonin also influence relaxation.
What 2 groups can pancreatic proteases be divided into?
- Endopeptidases e.g. trypsin.
2. Exopeptidases e.g. carboxy dipeptidases.
What do chief cells secrete?
Pepsinogen and gastric lipase.
Give 5 functions of hepatocytes.
- Creation and storage of energy in the form of glycogen.
- Synthesise and secrete plasma proteins.
- Remove amino groups from amino acids for the production of urea. (Deamination).
- Uptake, synthesis and excretion of bilirubin and bile acids.
- Detoxification and inactivation of drugs and toxins.
What clinical feature would you see in a patient with vitamin K malabsorption?
Bruising.
Chief cells secrete pepsinogen and and an enzyme. What is the enzyme?
Gastric lipase.
How are chylomicrons formed?
Triglycerides, phospholipids and cholesterol combine with proteins inside the epithelial cell forming chylomicrons.
What is serous acini secretion composed of?
alpha amylase - this is needed for starch digestion.
Where in the stomach are G cells most numerous?
In the antrum.
What is the submucosa layer composed of?
Loose connective tissue containing glands and lymph tissue. Many blood vessels and a rich plexus of nerves that is part of the enteric nervous system (Meissner’s plexus) are also found in the submucosa.
What molecule is responsible for the activation of pepsinogen into pepsin?
HCl.
