Alimentary Flashcards
Name x5 functions of the gastrointestinal tract
Digestion Absorption Hormone regulation Immunity Excretion
Which part of the colon passes down to the anus?
Sigmoid colon
Why is the gastrointestinal tract known as an external membrane?
It can be accessed through sphincters without crossing a membrane.
Recall the common signs and symptoms of gastrointestinal tract disease (general and upper)
General GI disease: Malaise, rapid weight loss, anorexia, anaemia
Upper GI tract: Haemoptysis, malaena, nausea, vomiting, dysphagia, odynophagia, heartburn
What is the difference between signs and symptoms?
Signs = externally visible Symptoms = internally experienced by the patient. Only noticeable to the patient.
Define malaise
Being generally unwell from an indeterminable cause.
Define malaena
Black tarry stool
What is malaena usually due to?
Upper GI bleeding
Define vomiting
Rapid ejection of stomach contents
Define odynophagia
Sensation of pain whilst swallowing food/ fluid.
What usually causes heartburn?
Acid regurgitation
Define belching
Excess air in the stomach escaping through the mouth
Define ‘referred pain’
When pain is felt in one location of the body but felt in another.
What is epigastric pain?
Discomfort in the central upper abdomen
In which quadrant is most liver and gallbladder pain usually felt?
In the right upper quadrant.
Name x5 indications a patient may present with for hepatobiliary disease
Pain in the right upper quadrant Biliary colic Jaundice Ascites Pale stool Dark urine
What happens in a biliary colic
Contraction of the gallbladder
Define jaundice
Yellowing of the skin, sclera and mucus membranes
What causes jaundice?
Increased amounts of circulating bilirubin
Name x1 hallmark symptom of liver failure
Jaundice
What causes dark urine?
Elevated conjugated bilirubin
What is the name of the substance which is responsible for giving poo its brown colour?
Stercobilin
Give x3 causes of ascites
Liver failure
Cancer
Malnutrition
What is ascites?
Accumulation of fluid in the abdominal cavity (>30mL).
Define steatorrhoea
Excess fats in stool caused by e.g. reduced lipase activity
Name 4 symptoms/signs of Mid GI tract disease
Diarrhoea
Steatorrhoea
Abdominal pain
Abdominal distension
Name x4 symptoms/signs of Lower GI tract disease
Abdominal pain
Rectal bleeding
Constipation
Diarrhoea
Give x2 causes of incontinence
Neural damage to anal sphincters
Mechanical damage to anal sphincters
Define cachexia
Muscle wasting
What is the term for enlargement of the lymphoid tissue
Lymphadenopathy
Define Koilonychia
Spooning of nails
In which quadrant is the liver located?
The upper right quadrant
Define haemorrhoids
Swollen superficial blood vessels (internal = painless, external = discomfort).
Define fistula
Alternate pathway e.g. anal fistula = not through the entire anal canal.
Define fissure
Tear/ ulceration of the mucosal lining
Define proctitis
Inflammation of the inner rectum
Name one diagnostic technique used in identifying proctitis
Sigmoidoscopy
Name 3 key factors to approaching pain
History
Examination
Investigations
What is the abbreviation in investigating pain?
SOCRATES
How will the signs of an upper gastrointestinal bleed (e.g. oesophagus) differ from a lower gastrointestinal bleed?
Upper GI bleed = malaena and haematemesis
Lower GI bleed = blood in urine/ stool; has not been modified by GI enzymes.
How many teeth does an adults have normally?
32 teeth
How many incisors does an adult have?
8
How many canines does an adult have?
4
How many pre-molars does an adult have?
8
How many molars does an adult have?
12
Which teeth are responsible for grinding the teeth down into smaller pieces?
Premolars and molars.
What is the proper name for the jawbone?
The mandible
Which is the largest muscle in the jaw and the one responsible mainly for biting?
The Massater muscle
Which are the two different places that the oral cavity can lead?
Lungs and stomach
Which are the two muscles which control whether oral contents go to the lungs or down the oesophagus to the stomach?
Epiglottis and the upper oesophageal sphincter
Describe the two types of muscle making up the upper oesophageal sphincter
Constrictor pharyngeus medius
Constrictor pharyngeus inferior
Describe the components of the lower oesophageal sphincter
Internal component = makes up circular smooth muscle of the oesophageal wall.
External component = makes up the diaphragm (voluntary).
Describe the pressure differences between the stomach and the pancreas
The stomach is under positive pressure whereas the oesophagus is mainly under negative pressure.
What is the epithelial lining arrangement of the oesophagus?
Non-keratinising stratified squamous epithelium until reaching the lower oesophageal sphincter (LOS), where the lining becomes simple columnar.
How many phases of swallowing are there and name each one.
There are 4 phases of swallowing: 0 - oral phase 1 - pharyngeal phase 2 - upper oesophageal phase 3 - lower oesophageal phase
Describe segmentation in the stomach
Pushes fluid towards the pyloric sphincter and solid chyme back to the body of the stomach.
What is the main protein secreting cell of the stomach?
Chief cell. Will see many RER and GA.
Which cell in the stomach secretes pepsinogen?
The Chief cell.
Which cell in the stomach secretes HCl?
The Parietal cell.
What structures will you see in the parietal cell?
Mitochondria, canaliculi, long cytoplasmic tubulovesicles which contain H+/K+ ATPase.
What will you see in an active parietal cell?
Tubulovesicles fuse with the canaliculi
How would inhibition of carbonic anhydrase influence acid secretion in the stomach?
This would decrease the amount of H+ being formed
Decrease HCl
Name one treatment to decrease HCl concentration in the stomach
Carbonix anhydrase inhibitor
What activates the breakdown of pepsinogen to pepsin?
HCl.
What is the most difficult to digest out of carbohydrates, protein and fats?
Protein. Pepsin’s role is to breakdown proteins into smaller fragments.
Name one substance which stimulates HCl production
Histamine (released from chromaffin cells)
Name the three phases of gastric secretion
Cephalic, gastric, intestinal
Name the three substances which are released from the intestine and inhibit stomach action
Cholecystokinin, secretin, gastric inhibitory peptide
What is the mechanism of Omeprazole?
Inhibits the Proton pump. = targets H+/K+ ATPase pump.
How does blood enter the liver?
Dual blood supply
Hepatic artery
Hepatic portal vein
What percentage of resting cardiac output goes to the liver?
25%
What is the difference between the hepatic artery and hepatic portal vein roles?
Hepatic artery: oxygenates liver
Portal vein: Contains everything absorbed from the small intestine and colon
What is the functional unit of the liver?
Acini
Give x2 disadvantages of switching from carbohydrate to fat metabolism
Fats provide less energy and fat metabolism is a slower process.
What are the products of transamination between alanine and a-ketoglutarate?
Pyruvate and glutamate
Which lipoprotein has the highest fatty acid content?
VLDL
What is segmentation?
Mixes contents of the lumen through contraction of the lumen circular muscle.
Alternate contraction and relaxation of circular muscle in the gut wall. Major effect = mixing and mechanical breakdown. Minor effect = propulsion.
Give one function of segmentation
Mixes enzymes with chyme
Where does most digestion of carbohydrates occur?
In the small intestine
What is the role of pancreatic amylase?
To digest COMPLEX carbohydrates to disaccharides or oligosaccharides (not monosaccharides; this is done by other enzymes).
What is the function of emulsification?
To increase the surface area of digestion
Through which two pathways are triglycerides made from FFAs and monoglycerides?
Monoglyceride acylation
Phosphatidic acid pathway
Segmentation involves sequential contraction. True or false.
False; involves random contraction
What is the function of bile salts?
Solubilise the products of lipid digestion
Islet tissue is most abundant in which part of the pancreas?
The tail
Can you swallow whilst upside down?
Yes; peristalsis is stronger than gravity.
Which nerve controls gastrointestinal motility?
The myenteric plexus
Name the layers of the gastrointestinal tract
Mucosa, submucosa, muscularis propria, adventitia/serosa.
Where is the myenteric plexus found?
In between the circular and longitudinal muscle in the muscularis propria layer.
Does any digestion occur in the oesophagus?
No. It’s primary role is to transport bolus from the oral cavity to the stomach.
Does any absorption occur in the oesophagus?
No. It’s primary role is to transport bolus from the oral cavity to the stomach.
Why is the oesophagus more susceptible to damage than the stomach?
It produces less protective mucous.
Describe and explain differences between oesophageal pressure and stomach pressure
The oesophagus operates at a lower pressure than the stomach pressure. This gradient is maintained by the LOS.
Describe how the stomach digests food.
Chemically (acid and enzymes) and mechanically (mixing and churning).
Describe the stomach mucosa
Columnar epithelium which invaginates into gastric pits lined with endocrine and exocrine cells.
The stomach can be split into how many regions? Name these regions.
5; fundus, cardia, body, pyloric antrum, pyloric canal
Where is gastric acid secreted from in the stomach, and how much of it?
Fundus and body - up to 2L a day.
How is the wall of the stomach different to other parts of the digestive tract?
It contains one extra oblique layer of smooth muscle inside the circular layer.
When the stomach is empty is it in a contracted or relaxed state?
Contracted.
What adaptation of the stomach aids its resevoir function?
Its rugae. The stomach folds stretch out when the stomach is filled.
What is the zymogen for protease?
Pepsinogen
What are the two main substances chief cells in the stomach secrete?
Pepsinogen and lipase
How does gastric lipase work?
By removing a fatty acid from a triglyceride.
When will G cells secrete gastrin?
- Vagus nerve stimulation
- In the presence of peptides in the stomach
- Stomach distension
Give x4 effects of Gastrin
- Increases gastric acid secretion
- Increases motility
- Stronger contractions
- Opening of pyloric sphincter
- Increases bile acid and pancreatic acid secretion through binding to receptors on the pancreas and gallbladder.
What affect does somatostatin have on acid secretion?
Somatostatin released from D cells inhibits histamine release from ECL cells and inhibits HCL release from Parietal cells.
Name two cells in the stomach which will have no effect on pH
Chief cells and stem cells.
Name x3 cells in the stomach which will increase the pH
D cells, I cells, S cells; all inhibit HCl secretion in some way.
Summarise the role of the stomach in the digestion of proteins.
The chief cell releases pepsinogen which is converted to pepsin by HCL. Pepsin converts long chain amino acids to shorter peptide chains. Mechanical mixing ensures good mixing of zymogens, HCL and protein.
What is the most likely effect of sympathetic stimulation of the stomach?
Decreased GI motility.
What is the most likely effect of sympathetic stimulation of mucous secretion within the stomach?
Decrease
Which stomach cell is associated with pernicious anaemia. Explain your answer.
Parietal cells produce intrinsic factor. Intrinsic factor is needed to bind with b12 for B12 to be absorbed.
Give x3 functions of the liver
Metabolic functions (synthesis), secretory functions, detoxification (breakdown of pathogens)
Give x3 functions of bile
Emulsification
Cholesterol homeostasis
Toxin excretion
What is the name of the structure in the liver which divides the right and left lobe?
The falciform ligament
Describe the blood supply of the liver
The liver has a dual blood supply - hepatic artery and hepatic portal vein both coming into the liver.
What is the structural unit of the liver?
The hepatic lobule (hexagonal)
What is the functional unit of the liver?
The acinus
Name 3 liver cells
Kupffer cells
Hepatocytes
Hepatic stellate cells
Cholangiocyte (secrete bicarbonate)
What is the main liver cell?
The hepatocyte
How much bile is produced a day?
500mL per day.
What is a cholecystectomy?
Removal of the gallbladder
What is bile made up of?
Cholesterol, bile salts and and bilirubin
Where is bile produced and from which cells?
From the liver: hepatocytes (60%) and cholangiocytes (40%). Hepatocytes are involved with primary secretion and cholangiocytes are involved with secondary modification.
What are the names of the salts the liver secretes into bile?
Cholic acid and chenodeoxycholic acid.
Are bile salts hydrophilic or hydrophobic?
Neither; they are amphipathic.
Name two things that the gallbladder does to bile.
Stores bile
Acidifies bile by absorbing HCO3-.
Which cell is usually located in the space of Disse and what is its main everyday function?
Hepatic stellate cell.
Function = storage of Vitamin A.
Which is the most important function of the small intestine?
Absorption of nutrients and water.
What are the landmarks that show where the small intestine starts and ends?
Pyloric sphincter - ileocaecal valve.
Where are villi found?
On the small intestine
Name the invaginations in the small intestine
Crypts of Lieberkuhn
Name x2 things in mucous
Water and glycoproteins
Name x3 examples of enteroendocrine cells
G, I, D and S cells
What do I cells secrete?
Cholecystokinin
Which are the immunological cells of the small intestine?
The Paneth cells
What is peristalsis?
Sequential contraction of circular muscle and longitudinal muscle in the gut wall to propel contents. Major effect is propulsion, minor effect is mixing.
What is the migrating motor complex?
Periodic contractions during the fed state.
Is there digestion of sugars in the stomach?
No. This resumes in the duodenum with pancreatic amylase following minor digestion in the oral cavity.
Name the three different disaccharides pancreatic amylase can break proteins down to
Lactose, maltose, sucrose
Pepsin requires what kind of environment to function?
Acidic
Is Gastric juice acidic or alkaline?
Alkaline; bicarbonate
How is galactose absorbed into the small intestine?
At the apical membrane, galactose is absorbed by the SGLT-1 transporter with Na+. At the basolateral membrane, galactose is absorbed through GLUT-2 through facilitated diffusion.
From which anatomical regions does the oesophagus start and end?
C5-T10.
Pharynx to stomach (gastrooesophageal sphincter).
Which structure prevents reflux at the lower oesophageal sphincter?
The diaphragm.
Describe the structure of epithelium post Z line at the lower oesophageal sphincter
SIMPLE columnar
In which organ are chief cells and parietal cells found?
The stomach
Tubulovesicles are found where and contain what?
Tubulovesicles are found in parietal cells and contain H+/K+ ATPase.
Parietal cells have a lot of which enzyme?
Carbonic anhydrase.
Bicarbonate ions are exchanged for which ions in the parietal cell?
Chloride ions.
How would inhibition of carbonic anhydrase influence acid secretion in the stomach?
Wouldn’t allow the formation and dissociation of carbonic acid, meaning a lack of protons and a lack of exchange of HCO3- for Cl- to form HCL.
Name the x3 pumps involved with forming HCL in the parietal cell
Na+/K+ ATPase pump
HCO3-/Cl- pump
H+/K+ ATPase pump
What is the mechanism of Ranitidine?
Histamine receptor antagonist
What is a cholecystectomy?
Removal of the gallbladder
Are there any differentiating transitions between the duodenum, jejenum and ileum?
No. All have the same histological features. Only distinguishing features. e.g. Ileum has Peyer’s patches.
Which cells are found in the Crypts of Lieberkuhn?
Paneth cells
Stem cells
(In the small intestine).
What effect does the Cholera enterotoxin have?
Prolonged opening of chloride channels
Excessive secretion of water.
Treat cholera with rehydration; lots of water lost in secretion.
Which cells protect stem cells in the small intestine?
Paneth cells.
Where is GLUT-2 found?
On the basolateral membrane; controls exit
GLUT-5 transports which molecule?
Fructose
SGLT-1 transports which molecules?
Glucose and galactose
Is the duodenum environment acidic or alkaline?
Alkaline
How are amino acids absorbed in the small intestine?
Facilitated diffusion and secondary active transport.
Are lipids soluble or insoluble in water?
INSOLUBLE.
Why are lipids harder to digest?
They are insoluble in water.
Describe digestion of lipids
- Secretion of bile and lipases
- Emulsification
- Enzymatic hydrolysis of ester linkages
- Solubilization of products in bile salts.
Name the parts of the pancreas
Head, neck, tail, body, uncinate process (hook)
Where does the pancreas drain into the duodenum?
The sphincter of Oddi
What are the two bifurcations of the common bile duct?
The cystic duct (leads to the gallbladder) Hepatic duct (leads to the liver)
Where do the head and tail of the pancreas sit?
The head sits in the duodenum
The tail sits in the spleen
Where does the pancreas receive its blood supply?
Superior mesenteric artery and the coeliac trunk.
Hepatic portal vein (to the liver).
Is the majority of the pancreas endocrine or exocrine?
Exocrine
Which system uses ducts?
The exocrine system.
Define zymogen
Inactive enzymes. (proteases)
Which are the most abundant cells in the islet of langerhans?
Insulin secreting b cells (70%)
Name x2 exocrine cells of the pancreas
Acinar cell
Duct cell
What is in the acinar cell of the pancreas?
Plenty of RER and zymogen granules
What is the purpose of the duct cell of the pancreas?
To secrete HCO3-.
Where are zymogens released from in the pancreas?
The acinar cells
Name x5 enzymes the pancreas makes
Amylase Lipase Trypsinogen Zymogen proteases Procolipase
Where is enterokinase released from and what is its role?
Released from the duodenum and converts trypsinogen to trypsin.
What is the role of trypsin?
Activates inactive enzymes. e.g. zymogen proteases to proteases
Where does the conversion of polysaccharides to disaccharides occur?
In the small intestine
What can happen in acute pancreatitis relating to zymogens?
Zymogens are activated inappropriately in the absence of enterokinase. e.g. trypsinogen to trypsin.
Cholecystokinin is secreted from where?
The acinar cells of the pancreas
Secretin is secreted from where?
The duct cells of the pancreas
Most gastric acid secretion usually occurs in which phase?
The intestinal phase
What does Phospholipase A2 do?
Hydrolyses fatty acids resulting in lysophospholipids and free fatty acids.
Where are bile salts absorbed?
In the ileum of the small intestine. They are then transported back to the liver for recycling.
What are the two pathways triglycerides are remade from monoglycerides and free fatty acids?
Monoglyceride acylation (major) Phosphatidic acid pathway (minor)
What are the components of a chylomicron and what is the main component?
Triglycerides (80%), phospholipids and cholesterol.
What substances are produced from the endocrine secretions of the pancreas?
Pancreatic juices. Exocrine; secreted into the duodenum via pancreatic ducts.
Does Cystic fibrosis involve the endocrine or exocrine parts of the pancreatic system?
Both.
Name the two exocrine cells of the pancreas
Acinar cells and duct cells.
Which pancreatic cells are rich in bicarbonate?
Centroacinar and duct cells.
Name x3 sources of bicarbonate
Bile
Pancreatic Juice
Brunner’s Glands
Is pancreatic venous blood acidic or alkaline?
Acidic; HCO3- leaves and enters blood.
Name two things the pancreas does to avoid enzymes auto-digesting itself.
- Secretes enzymes in the form of zymogens
2. Contains trypsin inhibitor
Where do pancreatic enzymes become activated?
In the duodenum
Where is enterokinase found?
On the brushborder of the small intestine.
Which is the enzyme which is actually secreted in its active form from the beginning?
Lipase BUT requires colipase. Lipase also require Bile salts for function.
What patient sign will you expect whilst an individual takes Orlistat?
Steatorrhoea.
When will Secretin be released?
When H+ increases in the blood (when food is eaten)
Causes the pancreatic duct to secrete HCO3-.
Negative feedback switches off secretin release
What controls homeostasis of bicarbonate ions?
Secretin
What controls homeostasis of enzyme secretion?
Cholecystokinin
When will Cholecystokinin be released?
Via the vagus nerve. CCK stimulates trypsin inhibitor and proenzymes.
No negative feedback for CCK. Stops once you stop eating.
Where do most duodenal ulcers occur?
In the duodenal cap (in the first part of the small intestine).
Name x3 individual structures of the large intestine which differentiate it from the small intestine
Pocketed walls, fatty tags, ribbons of longitudinal muscle (taeniae coli).
What is the large intestine made up of?
Caecum, appendix, Colon, rectum and anal canal.
The appendix protrudes from which structure?
The caecum
The pudendal nerve controls which sphincter?
The external anal sphincter
How does potassium move into the lumen of the large intestine?
Passively through gap junctions.
Why does the large intestine not have any villi?
Villi are needed for nutrient absorption and all nutrient absorption takes place in the small intestine.
What is the most prevalent species of bacteria in the stomach?
The bacteriodetes (gram-negative, anaerobic)
Give x3 roles of microbiota
- Act as competition for pathogens
- Synthesis and excrete Vitamin K
- Stimulate tissue development
What is meant by ‘faecal transplant’
Insert faeces into body to reintroduce normal gut flora
