GI Flashcards
What is the inguinal ligament formed from?
The thickening and rolling of the external oblique aponeurosis.
What is the innervation of the internal oblique, the external oblique and the transverse abdominis?
The external oblique is from the anterior rami of T7-T12.
The internal oblique and transverse abdominis is from the anterior rami of T7-L1.
What is the innervation of the rectus abdominis?
Anterior rami of T7-T11.
What is the rectus sheath, and at which point does it change? Describe these changes.
It is the enveloping of the rectus abdominis, by the aponeurosis of the external oblique, the internal oblique and the transverse abdominis.
At the point of the arcuate line, the aponeuroses move anteriorly to the rectus abdominis, rendering the posterior support the transversalis fascia and peritoneum, only.
What is the origin, insertion and actions of the external oblique?
Origin - 5th to 12th ribs.
Insertion - Iliac crest, inguinal ligament and linea alba.
Actions - flex the trunk, compress the abdominal viscera and to rotate the trunk contralaterally.
What is the origin, insertion and actions of the internal oblique?
Origin - Iliac crest, lateral inguinal ligament and thoracolumbar fascia.
Insertion - ribs 10-12, linea alba and pubic crest.
Actions - compression of the abdominal viscera, flexion of the trunk and ipsilateral rotation of the core.
What is the origin, insertion and actions of the transverse abdominis?
Origin - Costal cartilages of the lower ribs, thoracolumbar fascia, medial lip of the iliac crest and inguinal ligament.
Insertion - linea alba and pubic crest.
Actions - compresses abdominal viscera and for core stability.
What is the origin, insertion and actions of the rectus abdominis?
Origin - pubic crest and tubercle, and pubic symphyses.
Insertion - costal cartilages of ribs 5-7 and xiphoid process.
Actions - compression of the abdominal viscera and core support.
What causes a 6-pack to arise?
The tendinous intersections within the rectus abdominus muscle.
What are the 4 layers of the gut?
The mucosa, submucosa, muscularis externa and the serosa.
What forms the mucosa?
The epithelium, lamina propria and muscularis mucosae.
What is the function of the muscularis mucosae?
To keep the crypts dynamic.
Where are the meisseners and mynteric plexuses found?
The meisseners plexus is found within the dense connective tissue of the submucosa.
The mynteric plexus is found within the two layers of the muscularis externa.
What immune components does the lamina propria have?
It contains macrophages, IgA and antibodies.
What can non-keratinised stratified squamous epithelia do that keratinised cannot?
Secrete mucous - not involved in preventing water loss.
What are the mucous cells called between the gastric glands and crypts and what makes them different?
They are neck mucous cells which are irregular shaped and smaller than surface mucous cells.
What types of cells are located in the crypts of the small intestine and colon?
Stem cells - to replace the epithelium every 2-4 days.
Panneth cells - produce antibacterial proteases.
Enteroendocrine cells - produce hormones.
What do Brunner’s glands secrete and why?
The secrete an alkaline mucous substance into the duodenum to neutralise the acidic chyme.
What are the columnar cells in the colon called, and what are their adaptations?
Colonocytes which microvilli, but are not used for absorption.
What is the function of mucous within the colon?
It supports the microbiome and protects the colon from invasion of the bacteria within the epithelial layer.
What is the relevance of the coloncytes intracellular spaces?
They are large spaces which contains a large number of Na/K ATPases, which keep the Na+ concentration very low, which facilitates movement of the Na+ into the spaces/ colonocytes for the final water reabsorption.
What is the parasympathetic and sympathetic innervation of the gut?
The parasympathetic is from predominantly from the vagus nerve, but with some innervation from the pelvic nerves.
The sympathetic is from T5-L2.
How does the sympathetic nervous system innervate the gut?
The pre-ganglionic neurons bypass the sympathetic chain to form the splanchnic nerves and synapse onto the pre-vertebral ganglion, situated anterior to the vertebral column.
The post-ganglionic neurons then produce their effects on the gut tissues.
What are the 3 splanchnic nerves?
The greater, lesser and least splanchnic nerves.
What is the function of the meissener and mynteric plexuses?
Meissener’s plexus control secretion and blood flow.
Mynteric control gut motility.
What types of hormones are all the hormones released from the gut, and give examples of the hormones involved in the 3 types of secretions.
They are all peptide hormones.
Endocrine - gastrin, cholysystokinin and secretin.
Paracrine - somatostatin (released from D-cells).
Neurocrine - gastrin-releasing peptide (released from G-cells).
Where are enteroendocrine cells and what are they stimulated by?
They are found in the mucosa, between epithelial cells, and are stimulated by stretch, and food taken into the GI.
What types of cells release gastrin and where are they found?
G-cells, found in the antrum of the stomach and colon.
What are G-cells stimulated and inhibited by, and what do they stimulate themselves?
They are stimulated by stretch, by protein breakdown and by the vagus nerve. They are also stimulated by gastrin-releasing peptide.
They are inhibited by somatostatin (which is stimulated by low pH).
G-cells stimulate parietal cells to release acid, from the stomach.
Where are I-cells found, what are their secretions and what are they stimulated by?
They are found in the duodenum and jejunum.
They secrete cholecystokinin.
They are stimulated by the breakdown of fats and proteins, and low pH.
What is the function of cholecystokinin?
It relaxes the sphincter of Oddi, allowing secretions to enter the duodenum.
Contracts gall bladder for bile secretion.
Stimulates the pancreas to release digestive enzymes.
What do S-cells secrete, and what is their stimulation?
They secrete secretin.
These are stimulated by acidic chyme.
What is the function of secretin?
It stimulates bicarbonate-rich secretions to be released from the gallbladder and pancreas, into the duodenum.
What is gastrin-inhibitory polypeptide stimulated by, and what is its function?
It is stimulated by the breakdown of all food.
It’s function is to inhibit gastric acid secretions and increase insulin secretions.
What separates the abdominal cavity from the thoracic and pelvic cavities, but why are these not actual separations?
It is separated from the thoracic cavity by the diaphragm, but it contains perforations to allow the passage of blood vessels and structures such as the trachea and oesophagus.
It is ‘separated’ from the pelvic cavity by the pelvic brim, which is not actually a separation, and allows the abdominal viscera to extend into the pelvic cavity.
What is the peritoneal cavity made of?
It is formed from layers of mesothelium, which consists of the simple squamous epithelia, which can secrete the serous fluid contained within the cavity.
What are the intra-peritoneal and retroperitoneal viscera?
The intra-peritoneal viscera are enveloped by the peritoneum, whereas the retroperitoneal viscera have only their anterior surface covered by parietal peritoneum.
What are two layers of peritoneum connecting to the retroperitoneal space called, and what passes within it?
A mesentery.
Blood vessels, lymphatics and nerves pass within this.
What are the two layers of peritoneum passing between two intra-peritoneal organs called?
Peritoneal ligament.
What are the directions of the muscle fibres of the internal oblique, external oblique and transverse abdominus?
Internal oblique - superomedial.
External oblique - inferomedial.
Transverse abdominus - transverse.
What are the UOS and LOS of the oesophagus and what are their functions?
Upper oesophageal sphincter - prevents air from entering the oesophagus.
Lower oesophageal sphincter - prevents gastric acid reflux.
What are the greater and lesser sacs of the peritoneum, and how do they form?
The greater sac is the sac that envelops all of the intraperitoneal viscera, that can be seen when opening the abdominal cavity. The lesser sac is a sac that does not envelop anything and is found behind the liver, extending down.
They are formed through the twisting of the liver and stomach during embryology.
What is mass movement?
Rapid peristalsis of the large bowel, emptying contents into the rectum.
What process triggers the sensation to defecate?
The stretch of the rectum.
How does the saliva confer pathogenic protection?
It contains antibacterial agents.
Where can lower lobe pneumonia pain be felt?
Hypochondrium.
What is a hiatus hernia?
A portion of the stomach pushing through the right crus of the diaphragm.
What is D1 of the duodenum?
The duodenal bulb - the most proximal part of the duodenum, closest to the stomach.
What is the difference between structures passed through in omphalocele and gastrochisis?
Omphalocele is a herniation through the umbilicus.
Gastroschisis is a herniation through the body wall.
In an omphalocele, what are the intestines contained within, and what does this protect them from?
They are contained within the peritoneum, protecting them from amniotic fluid.
What defects are omphalocele’s associated with?
Heart and neural tube defects.
What is gastroschisis due to, and what can the damage be?
It is due to abnormal embryonic folding, which can lead to amniotic fluid damaging the bowel, and twisting of the bowel, leading to ischaemia.
Where are is the pain felt from the foregut viscera, midgut viscera and huindgut viscera? State the nerve and dermatome associated with it.
Foregut viscera - epigastric region, from the greater splanchnic nerve, in the T5-T9 dermatomes.
Midgut viscera - peri-umbilical region, from the lesser splanchnic nerve, in the T10-T11 dermatomes.
Hindgut viscera - supra-pubic region, from the least splanchnic nerve (and lumber splanchnic nerves), in the T12-L2 dermatomes.
Which sensory nerves relay information to the brain regarding pain of the abdomen?
The visceral afferent nerves.
Outline the route of the visceral afferent nerves from the gut.
The visceral afferents run in opposition to the sympathetic innervation of the gut:
- From the viscera, via the splanchnic nerves.
- To the pre-vertebral ganglion, which split into the spinal nerves.
- The spinal nerves travel back to the spinal cord at the levels of T5-L2.
What are the layers of a hernia, from superficial to deep? State what the common contents of the hernia are.
Skin, then the layers of abdominal wall muscles that it protrudes in. Then the parietal peritoneum (and usually visceral, depending on the organ).
They are usually loops of bowel or omentum, but can be any structure of the abdominal cavity.
What are the 3 common weaknesses of the abdominal wall, and what else can weaken the wall?
The inguinal canal, femoral canal and umbilicus.
Surgical incision, particularly through muscles, can weaken the abdominal wall.
How does the gubernaculum guide the testes?
It is a condensed band of mesenchyme which is attached to the inferior pole of the testes and labioscrotal swelling (before sexual differentiation).
The gubernaculum then shrinks, pulling the testes down, through the inguinal canal, into the scrotum.
What descends into the scrotum prior to the testes, and what does it become within the scrotum?
The processus vaginalis descends into the testes to become the tunica vaginalis, which encloses most of the testes, acting as a protective capsule.
What determines how far down the inguinal canal and scrotum the hernia can migrate?
The processus vaginalis’ obliteration. The lower the obliteration, the further towards/ within the scrotum the hernia can protrude.
What is the conjoint tendon?
The joining of the internal oblique and transversus abdominus’ aponeuroses.
What structures are the deep and superficial inguinal rings located within?
Deep is within the transversalis fascia.
Superficial is within the external oblique aponeurosis.
What do femoral hernias often protrude out of?
The saphenous opening.
What are the 3 sections of mesoderm, and what do they form?
Paraxial - somites, which forms the skeletal muscle, vertebra and cartilage.
Intermediate - kidneys and gonads.
Lateral plate - formed of splanchnic and somatic. Splanchnic forms the viscera and the somatic forms the body walls.
What do the ectoderm and endoderm form?
Ectoderm - epidermis, CNS and PNS.
Endoderm - epithelia of the GI and other tracts.
What happens during cranio-caudal folding, up to the 4th week?
The mesoderm undergoes a pinching manoeuvre, forming the blind-ended gut tube.
The ectoderm thickens where it overlies the mesoderm, forming the brain and spinal cord.
What connects the midgut to the yolk sac, and what is formed should this not obliterate before birth?
The Vitelline duct - Meckles diverticulum (an out pouch of the small intestine) can form, where faecal can leak out into the anterior abdominal wall.
What occurs during ventral folding?
The lateral folds come together and fuse, forming the ventral abdominal wall.
What forms the visceral and parietal peritoneum?
Visceral - splanchnic mesoderm.
Parietal - somatic mesoderm .
What does the intraembryonic coelom give rise to?
The thoracic and abdominal cavity.
What are the somatopleuric and splanchnopleuric mesoderm, and what do they form?
Somatopleuric - somatic mesoderm and ectoderm together, forming the body walls and dermis.
Splanchnopleuric - splanchnic mesoderm and endoderm, forming the viscera (organs).
What two membranes make the gut tube blind-ended, and when do they rupture?
The cephalic end is enclosed by the bucco/oropharyngeal membrane. This ruptures during the 4th week.
The caudal end is enclosed by the cloacal membrane. This ruptures during the 7th week.
What does the cloaca form, and where is it located?
It separates to become the urogenital sinus and anorectal canal, within the hindgut.
What degree does the stomach rotate by?
90 degrees.
What is the difference between somatic and splanchnic mesoderm pain localisation?
The somatic mesoderm can localise the pain, whereas the splanchnic mesoderm cannot.
What structures do the spleen and liver rotate within?
The spleen in the dorsal mesentry.
The liver in the ventral mesentry.
What connects the liver and gallbladder?
Common bile duct.
Where do the left and right vagal trunks go to after rotation?
The left forms the anterior vagal trunk.
The right forms the posterior vagal trunk.
Label the peritoneal ligaments.
What does the ventral bud of the pancreas form from?
The hepatic diverticulum.
If the ventral and dorsal pancreatic buds don’t fuse, then what occurs?
The accessory pancreatic duct is formed, proximal to the main pancreatic duct.
What is the mid point of the inguinal canal an anatomical mark for?
The deep inguinal ring.
What is the remnant of the gubernaculum in males?
The scrotal ligament.
Where does the inguinal ligament run between?
Pubic tubercle to anterior superior iliac spine.
What is the major papilla?
The point at which the pancreas and liver join to the duodenum - in D2.
What is annular pancreas?
Where each of the ventral buds travel in opposite directions, surrounding the duodenum.
What is the clinical presentation of annular pancreas?
Vomiting with bile in as it is below the major papilla.
What is pancreas divisum?
Where the accessory duct (from the ventral bud) drains into the major papilla, with the main duct (from the dorsal bud) going to the minor papilla.
What is the problem with pancreas divisum?
The secretion of the main duct of the pancreas cannot all enter the duodenum, potentially leading to infection.
What is pyloric stenosis?
A narrowing of the pyloric lumen, as the contents leave the stomach, due to hypertrophy of the circular and longitudinal musculature of the stomach, resulting in projectile vomiting as the food cannot pass through.
What is the underlying cause of an umbilical hernia?
Incomplete closure of the umbilical ring.
What is the medial portion of the floor of the inguinal canal?
Lacuna ligament.
What are the names of the open incisions made in appendix surgery and cholecystectomy?
Gridiron for appendix.
Kocher for cholecystectomy.
What is the vascular supply to the anal canal?
Cranial part - superior rectal artery, from the inferior mesenteric artery.
Caudal part - inferior rectal artery, from the internal pudendal artery.
Where does the midgut start?
The mid-point of the second part of the duodenum - D2 - at the point where the common bile duct and major pancreatic duct drain (major papilla).
When does physiological herniation occur, why does it happen and what is its axis?
It occurs at the 6th week and re-enters the foetal body at the 10th week.
It occurs due to the enlargement of both the small intestine and liver at the same time, meaning there is insufficient space within the abdominal cavity.
The superior mesenteric artery is the axis.
What happens during physiological herniation, and what is the outcome?
The small intestine herniates out of the umbilical cord, and elongates. It then undergoes 3 anti-clockwise rotations, leaving the caecum in the right iliac fossa, the ascending colon lying to the right of the small intestine and transverse colon anterior to the small intestine.
Why does gastroschisis occur?
Due to incomplete lateral folding, meaning that the ventral abdominal wall does not form correctly.
What are vitelline cysts and fistulas?
Vitelline cyst - this is where the midpoint of the vitelline duct is patent.
Vitelline fistula - this is where there is no obliteration of the duct, allowing the faecal material to extrude through the umbilicus.
What is Meckles diverticulum?
Where the vitelline duct does not obliterate correctly, leading to a small out pouch within the midgut, where faecal material can accumulate.
What are the rule of twos, relating to Meckles diverticulum?
It is seen in 2% of the population.
Located 2 feet proximal to ileo-caecal valve.
Detected in under twos.
2:1 ratio in males to females.
What are two abnormalities that can occur with recanalisation, and where are they most frequently seen?
Stenosis - where the lumen is narrowed.
Atresia - where the lumen is completely occluded.
It is most frequently seen in the duodenum.
Which non-gastrointestinal structure is found in the hindgut?
Bladder epithelium.
What does the allantois become?
The urachus, then median umbilical ligament.
How does the cloaca split, and what does it become?
The urorectal septum, formed from mesoderm, divides the cloaca into the urogenital sinus and anorectal canal.
What are the stomodeum and proctodeum?
Stomodeum - ectodermal wall that ruptures and opens the primordial mouth to the amniotic fluid.
Proctodeum - ectodermal wall that ruptures and opens the primordial anus to the amniotic fluid.
What is the pectinate/ dentate line?
The border between ectoderm and endoderm of the anus.
It is where the stratified squamous epithelia become simple columnar epithelia.
What is the white line?
The border between where the epithelia becomes non-keratinised stratified squamous epithelia, from keratinised (skin).
How does the pain and blood supply to the anus differ above and below the pectinate line?
Above the pectinate line, stretch and chemical injury is felt as vague pain, due to it being formed from (splanchnic) mesoderm. The blood supply is also from the gut.
Below the pectinate line, the pain is localised due to being of ectodermal origin. The blood supply is systemic - internal pudendal artery.
What is an imperforate anus?
Imperforate anus is where the anus has formed but the cloacal membrane fails to obliterate. This is treated surgically, and so leads to few complications.
What is anorectal agenesis?
Where poor blood supply to the hindgut leads to the rectum and anus not forming correctly.
What is an anorectal fistula?
A connection between the rectum and anal canal, and the bladder or vagina.
This leads to faecal material entering these spaces, which can lead to severe infections.
How does the mucous content in the saliva aid the body?
It helps with swallowing and speech.
How does the saliva act in aiding protection?
It has a cooling effect.
It washes away debris stuck between the teeth.
It secretes lysozymes which break down the cell wall of bacteria.
It secretes lactoferrin which chelates iron, reducing the availability, preventing bacterial multiplication.
How are salivary amylase and lingual lipase adapted to act for longer?
Salivary amylase - food in the stomach inhibits the effects of pH against the enzyme, allowing it to work for longer.
Lingual lipase - has the ability to survive within acidic conditions and the proximal duodenum.
What is the constituents of the secretions from the parotid, submandibular and sublingual glands?
Parotid - serous secretions containing a high proportion of enzymes. 25% of the total saliva.
Submandibular - mixed, containing both serous and mucous secretions. 70% of the total saliva.
Sublingual - mucous secretions. 5% of the total saliva.
How much saliva is secreted per day?
1.5L.
Why do the salivary secretions become hypotonic if they are formed as isotonic?
As they pass through the salivary ducts, the ducal cells absorb sodium and chloride ions much faster than they secrete bicarbonate and potassium ions.
The ductal cells are impermeable to water, meaning water cannot follow, out of the lumen.
How are secretions pushed out of the acinus?
Myoepithelial cells contract around the acini.
What is the parasympathetic supply to the salivary glands?
Parotid - glossopharyngeal nerve.
Submandibular and sublingual - facial nerve.
What are some causes of xerostomia?
Medications - anticholinergics and SSRIs.
Autoimmune.
Dementia.
Radiotherapy.
Dehydration.
What autoimmune condition can attack the salivary glands, and what is the clinical presentation?
Sjogrens.
Dry mouth, swollen and painful glands.
What are salivary stones, what is their presentation and where are they most commonly seen?
Sialoliths.
This is calcification, blocking the duct of the salivary gland, most commonly the Wharton’s duct of the submandibular gland.
There is swelling and associated pain with salivating.
How do the movements of the tongue in the oral phase of swallowing help swallowing?
The tongue is pushed against the hard palate and then backwards.
This pushed the bolus against the oropharynx initiating the reflex.
When pressed against the hard palate, it prevents food from coming back out when swallowing.
How long does the pharyngeal phase last?
Around 0.2 seconds.
What are some causes of poor coordination of swallowing, why are these the case?
Cerebrovascular accidents - stroke.
Parkinson’s disease.
Multiple sclerosis.
The pharyngeal phase is controlled neurally. If there is disruption in this then the muscles will not work together efficiently.
What are the symptoms of dysphagia, when it is due to problems coordinating swallowing?
Unable to close the mouth leading to dribbling or protrusion of food from the mouth.
Material entering the respiratory tract, leading to coughing/ choking and potentially pneumonia.
What are some causes of dysphagia due to a physical blockage?
Fibrous rings forming within the oesophagus, often seen in scarring due to acidic reflux.
Oesophageal cancer.
Achalasia - failure of the lower oesophageal sphincter to relax.
What are the internal and external surfaces of the gums called?
Internal - lingual surface.
External - buccal surface.
What structure does the parotid duct penetrate and where does it do it?
It penetrates the buccinator, at the level of the 2nd upper molar.
Where are the parotid, sublingual and submandibular glands located?
Parotid - inferior to the zygomatic arch, superficial to the masseter and superior to the mandible.
Sublingual - the floor of the mouth.
Submandibular - within the submandibular triangle, underneath the mandible, above the hyoid.
What determines whether swallowing or the gag reflex will occur?
The nature of the stimulus - whether it is pleasant or not.
Age - infants have a much poorer control over the neural pathway.
How can a food bolus at the junction of the oesophagus and pharynx be treated?
A drug may be given to relax the muscles of the junction.
Surgery may be performed to remove it.
What 5 methods does the body have to prevent gastro-oesophageal reflux?
Weakness in the conjoint tendon increase the risk of what kind of herniation?
Direct inguinal hernia.
State the ligaments of the liver and their attachments.
Falciform ligament - attaches the anterior surface of the liver to the anterior abdominal wall.
Coronary ligament - has anterior and posterior folds; attaches the superior surface of the liver to the inferior surface of the diaphragm. They units to form the triangular ligaments.
Right and left triangular ligaments - left is at the apex of the liver to the diaphragm. The right is from the right lobe of the liver to the diaphragm.
Lesser omentum - attaches the liver to the lesser curve of the stomach and the duodenum.
What does the lesser omentum consist of?
Hepatoduodenal ligament - duodenum to the liver.
Heptogastric ligament - stomach to the liver.
State the 3 branches of the coeliac trunk.
The splenic artery.
The left gastric artery.
Common hepatic artery.
What is the route and branches of the splenic artery?
Formed from a branch of the coeliac trunk, running behind the stomach, to the spleen.
It gives branches to the body and tail of the pancreas.
It gives off the short gastric vessel, which supplies the fundus of the stomach.
It gives off the left gastroepiploic artery, which supplies some of the greater curve of the stomach.
Outline the blood supply to the greater curvature of the stomach.
The greater curvature is supplied by the anastomosis between the left gastro-epiploic, from the splenic artery, and the right gastro-epiploic, from the gastro-duodenal artery.
Outline the blood supply to the lesser curve of the stomach.
The left gastric artery branches from the coeliac trunk and meets the right gastric artery, which is a branch of the proper hepatic artery (usually).
Outline how the right crus of the diaphragm is structurally and functionally adapted.
The right crus is structurally different from the costal diaphragm and loops around the oesophagus, helping to form the lower oesophageal sphincter.
It contracts to compress the oesophagus, particularly where there is an increase in intra-abdominal pressure, preventing reflux from the stomach.
What is receptive relaxation? Why does this occur?
Peristalsis of the oesophagus causes relaxation of the proximal aspect of the stomach - opening the lower oesophageal sphincter.
This fundus distends as it relaxes and the ruggae elongate.
This allows for the stomach to fill with contents without a significant rise in pressure, reducing the risk of reflux.
What are the 3 muscles of the stomach, superficial to deep?
Longitudinal.
Circular.
Oblique.
What cell types are found in the gastric pits, and where are the gastric pits located?
Parietal cells, chief cells and enteroendocrine cells.
The gastric pits are found invaginating the epithelium.
How do prostaglandins act to protect the stomach?
Increase the muscosal blood flow for removal of H+ ions.
Support the mucous layer of the stomach.
General protective mechanism.
What is the proton pump?
The hydrogen/ potassium ATPase, which pumps hydrogen ions into the lumen of the stomach and taking potassium ions into the parietal cell.
How are the parietal cells changed when entering the stimulated phase, and what other adaptions do they have?
The tubulovesicles that have proton pumps come into contact with the potassium-permeable apical membrane.
The apical membrane is involuted, forming canaliculi, which also contain microvilli, increasing the surface area for the H+/K+ ATPase to function across.
What are the sensory triggers for the cephalic phase of digestion?
Smell, sight and taste.
What are the gastric triggers for the gastric phase of digestion?
Stretch of the stomach.
Presence of amino acids and small peptides.
Presence of food buffers the pH, so the low pH inhibition (somatostatin) is removed.
What are the intestinal triggers for the intestinal phase of digestion?
Chyme entering the duodenum.
Partially digested protein in the duodenum.
How are parietal cells activated?
Cholecystokinin receptors are activated by gastrin, released from G-cells.
Histamine receptors are activated by histamine, released from entero-chromaffin like cells.
Muscarinic receptors are activated by acetylcholine, released from the vagus nerve.
How are G-cells stimulated?
Vagus nerve released gastrin-releasing peptide, as a result of stretch of the stomach.
Vagus nerve also releases ACh, as a result of sensory triggers.
Peptides in the stomach.
How are entero-chromaffin like cells stimulated?
Vagus nerve releases ACh which binds to muscarinic receptors.
Cholecystokinin receptors are stimulated by gastrin.
How is acid secretion inhibited?
A decrease in pH is sensed by the D-cell.
Somatostatin is released and binds to the somatostatin-receptor on the G-cell.
Gastrin release is inhibited.
How is HCl produced in the parietal cell?
In the presence of carbonic anhydrase, within the parietal cell, water and carbon dioxide come together to form carbonic acid.
H2CO3 then dissociates into H+ and HCO3-.
The proton pump then pumps H+ ions into the lumen of the stomach, drawing in potassium ions.
The potassium ions are then extruded into the lumen of the stomach (via ROMK receptors).
The anion exchanger then exchanges bicarbonate ions for chloride ions.
The chloride ions are then pumped into the lumen via chloride channels, where they combine with the hydrogen ions to form HCl.
The HCO3- ions are taken away in the venous blood.
What is the alkaline tide?
The increase in pH within the venous blood draining the stomach, due to the exchange of bicarbonate ions for chloride ions. It is seen after eating, when the parietal cell increases its HCl secretions.
What is the mechanism of the lower oesophageal sphincter?
Intrinsic smooth muscle of the oesophagus is in a constant state of contraction, but relaxes when food goes down the oesophagus.
The right crus of the diaphragm can contract and wraps around the oesophagus - an increase in pressure causes the crus to pull tighter.
Oblique angle of entry of the oesophagus.
What is the issue with strictures of the oesophagus?
Fibrous scar tissue narrows the lumen of the oesophagus, leading to dysphagia.
What is fundoplication?
Where the fundus of the stomach is wrapped around the lower oesophagus, below the diaphragm, preventing gastric acid reflux.
What are the lifestyle management for gastro-oesophageal reflux disease, and what is their general overall aim?
To decrease intra-abdominal and intra-gastric pressure, predominantly, to decrease the risk of reflux.
How can bile reflux be a cause of acute gastritis?
Reflux through the pyloric sphincter causes chemical injury to the stomach.
How can autoimmune chronic gastritis lead to pathological changes?
Autoantibodies attack the parietal cells.
This causes:
- Atrophy of the body of the stomach, leading to gastritis.
- Decrease acid production, which can increase the risk of infections.
- Decrease intrinsic factor release, leading to a lack of B12 absorption.
What are the signs/ symptoms of autoimmune chronic gastritis?
Pernicious anaemia - megaloblastic.
Neurological symptoms - numbness in the hands and feet, and confusion.
Anorexia - loss of appetite.
Glossitis - inflammation of the tongue.
How does helicobacter pylori benefit some people?
Helps control the stomach microbiome.
How does helicobacter pylori use chemotaxis, and how does it stay in the required place?
It senses the increase in pH and uses its flagella to move there.
It has adhesins which bind to the gastric epithelia, resisting peristalsis.
Where is the urease found within the H.Pylori, and what is the beneficial function of it?
It is found within the cytoplasm.
It converts urea and water in carbon dioxide and ammonia.
The ammonia alkalises the outer membrane and the surrounding environment.
What is the function of cytotoxic-associated gene A, released from helicobacter pylori? What risk is associated with this?
A protein is formed and inserts into the stomach epithelia, causing inflammation by stimulating IL-8.
It increases the risk of stomach cancer.
What is the function of vacuolating toxin A, released from helicobacter pylori?
VacA is a protein that toxic to the stomach epithelia.
It also increases the paracellular permeability.
How can helicobacter pylori in the antrum affect the stomach and duodenum?
It can activate the gastrin cells, as it releases ammonia which increases the pH, which increases the number, and amount of acid released from the body of the stomach.
It can enter the duodenum and cause ulceration.
The decrease in pH can also cause metaplasia of the duodenum, increasing the risk of cancer.
How can helicobacter pylori increase the risk of cancer when it colonises the body or fundus of the stomach?
Atrophy of the parietal cells occurs.
This leads to dysplasia, increasing the risk of cancer.
What are the antibiotics used to eradicate H.Pylori, and what are the side effects seen in 5% of patients?
Clarithromycin and metronidazole.
Diarrhoea and nausea is sometimes seen.
How can NSAIDs cause peptic ulcer disease?
They inhibit prostaglandins, decreasing the mucosal blood flow and bicarbonate mucous secretions.
Where do chronic peptic ulcers form?
At the mucosal junctions between:
- Duodenum and the antrum of the stomach.
- Antrum and body of the stomach.
If there is very severe peptic ulcer disease, what infectious complication can occur?
Peritonitis as there is erosion through the wall of the stomach, leading to contents leaking out into the peritoneal cavity.
Where else can erosion of the wall occur, due to severe ulceration, and what is the consequence of this?
The gastro-duodenal artery, due to a posterior duodenal ulcer, leading to blood pooling in the stomach causing haematemesis (vomiting blood).
Rarely, it can erode through the splenic artery.
What is malaena?
An upper gastrointestinal bleed where the haem is oxidised as it passes through the tract, leading to black, tar-coloured stools.
This occurs if there is a small, gradual bleed, not a large bleed, such as in haematemesis.
What are the symptoms of peptic ulcer disease?
Pain - epigastric and back pain, worsened after meals.
Haematemesis and malaena from bleeding.
Early satiety due to the muscularis externa being replaced with scar tissue, meaning the stomach cannot expand as much.
Weight loss due to associating eating with pain.
How can the timing of pain be used to help determine where the peptic ulcers are?
Immediately after eating - gastric.
A while after eating and at night - duodenal, as the pyloric sphincter opens, allowing chyme to enter.
What is the treatment for an active bleeding peptic ulcer disease?
What is the main function of motilin, and the effects it has on the brain, gallbladder, pancreas and stomach?
Increase pepsinogen secretions.
What are the small bowel, transverse mesocolon or sigmoid mesocolon?
Small bowel mesentry - attaches the jejunum and ileum to the posterior abdominal wall.
Transverse mesocolon - attaches the transverse colon to the posterior abdominal wall.
Sigmoid mesocolon - attaches the sigmoid colon to the posterior abdominal wall.
What are the properties of chyme leaving the stomach?
It is semi-solid - part liquid and part solid, that is partially digested and has a low pH due to gastric acid secretions.
How are biliary secretions controlled?
Cholecystokinin stimulates the contraction of the gallbladder and relaxation of the sphincter of oddi, leading to bile - an alkaline substance - being secreted into the duodenum.
What are the components of bile?
Bile salts, acid and pigments, phospholipids, conjugated bilirubin, electrolytes and water.
Describe how the microscopic appearance of the liver relates to its function of digestion.
There are hepatocytes arranged in lobules, with bile ducts running between the lobules. This allows for bile to be synthesised and released into the bile ducts, then common hepatic ducts, then drain into the common bile duct, which is attached to the cystic duct from the gallbladder.
What are the 4 parts of the duodenum and their importance?
D1 (superior) - connected to the liver by the hepatoduodenal ligament and is the most common site of ulceration.
D2 (descending) - curves around the pancreas and is where the major papilla is located.
D3 (inferior) - crosses over the IVC and aorta.
D4 (ascending) - joins the jejunum, at the duodenojejunal flexure, with the suspensory muscle contracting, pushing contents into the jejunum.
What branch of the aorta supplies the midgut, and what is its course in the abdomen?
Superior mesenteric artery - it travels in an oblique direction, heading towards the right iliac fossa.
It is at the level of L1.
What are the 4 branches of the superior mesenteric artery to the midgut?
Jejunum and ileum - branching of the SMA to the left occurs, which anastomose forming arcades.
Caecum and terminal ileum - ilio-caecal branch.
Ascending colon - right colic artery.
Proximal 2/3rds of the transverse colon - middle colic artery.
What branch of the aorta supplies the hindgut, and what is its course in the abdomen?
Inferior mesenteric artery.
It is given off at the L3 level and passes into the pelvis, after having given off multiple branches, to form the superior rectal artery.
What are the two main branches of the inferior mesenteric artery, and what do they supply?
Left colic artery, which supplies the descending colon.
Sigmoidal artery, which supplies the sigmoid colon.
What is the marginal artery of the gastrointestinal system?
Anastomoses between the branches of the superior mesenteric artery and the inferior mesenteric artery, supplying oxygenated blood to the colon.
Which part of the colon can be damaged by a low blood pressure, and why?
The splenic flexure - a vascular watershed area of the GI tract. A decrease in blood pressure can lead to ischaemia.
This is because the superior mesenteric artery’s middle colic artery anastomoses with the (ascending branch of the) left colic artery, here.
Where does the portal vein form, and at what spinal level is this?
Behind the neck of the pancreas.
It forms at the level of L1.
Which sections of the duodenum are retroperitoneal?
Descending, horizontal and ascending - D2, D3 and D4.
Anatomically, what is significant about the level at which the major papilla lies in the duodenum?
It is midway though D2.
It is the point at which the foregut becomes the midgut.
What is the relationship between the pancreas, duodenum and SMA?
The neck of the pancreas wraps around the superior mesenteric artery, leaving the head of the pancreas in the C-shape of the duodenum (with the uncinate process also here, a bit more distal), posterior to the artery.
Where, retroperitoneal or intraperitoneal, does the pancreas lie?
The uncinate, head and body are intra-peritoneal.
The tail is retroperitoneal, closely related to the spleen, wrapped in the spleno-renal peritoneum.
What is the free edge of the lesser omentum formed from, and what does it envelop?
The ventral mesentery of the foregut is the only ventral mesentry, meaning that it has no connections to any mesentries of the mid- and hindgut.
It envelops the portal vein, hepatic arteries and a portion of the bile duct.
Which veins unite to form the portal vein?
The splenic vein and superior mesenteric veins.
The inferior mesenteric vein drains into the splenic vein.
What are the paracolic gutters and where are they found?
There is a left and a right, which are spaces between the colon and abdominal wall.
Left - between the lateral abdominal wall and the descending colon.
Right - between the lateral abdominal wall and ascending colon.
Where is the hepatorenal recess, and what can it be useful for?
Space between the right anatomical lobe of the liver and right kidney.
It is the lowest point of the peritoneal cavity when supine and so ultrasound can be used to detect peritoneal fluid for ascites.
Why is the osmotic pressure in the stomach so high?
The stomach is relatively impermeable to water.
The breakdown of food increases the osmolarity - the greater the breakdown, the higher the osmotic pressure it exerts.
What is the release of chyme controlled by?
Pyloric sphincter.
What are the 3 structures of the pancreatic secretory part, and what are their functions?
Acinus - synthesise enzymes.
Centroacinar cells - form the aqueous part of the secretion.
Ductal cells - modifying the aqueous secretions, producing a bicarbonate solution.
What are the different pancreatic secretions, their proportions and methods of secretions?
Exocrine - 90% of the secretions are enzymatic and drain via the major pancreatic duct.
Endocrine - 2% hormonal secretions, which drain into the splenic vein.
What is the neural and hormonal control of the pancreas, and their functions?
Sympathetic, via greater splanchnic nerve - inhibits the function via vasoconstriction.
Parasympathetic - vagus nerve and stimulation of cholecystokinin, stimulates.
What stimulates the actions of the vagus nerve on the pancreas and release of cholecystokinin?
Hypertonicity.
Small peptides.
Fats.
What is the organelle composition within hepatocytes, and how does this relate to its function?
Contains lots of RER and SER for synthesis of proteins and lipids.
Contains stacks of Golgi membranes - modification and movement of the products.
Also contains glycogen granules.
What are the two components of bile?
Bile acid dependent - bile acids and pigments that are secreted into bile canaliculi.
Bile acid independent - alkaline solution that is secreted by duct cells, stimulates by secretin.
Explain how portal hypertension can cause umbilical varices.
When there is sufficient pressure in the portal system, the anastomoses between the portal system and ligamentum teres (remnant of umbilical vein) causes the the ligamentum teres to distend. This leads to a caput medusa appearance.
Explain the drainage of bile from the liver and gall bladder, and how this communicates with the pancreas.
How do ulcerations appear on colonoscopy?
White streaks.
What are some different locations of the appendix?
Retro-caecal.
Pelvic.
Sub-caecal.
Para-ileal (pre or post).
What are some blockages that can occur, of the appendix?
Faecolith - hard part of faeces.
Lymphoid nodule hyperplasia - seen usually due to viral infections.
Foreign body.
What sign can be seen on a CT scan with a patient with Crohn’s disease?
Target sign - thickening of the full bowel wall and obstruction.
What are the different types of ulcerative colitis?
What are some risk factors for gastric cancer?
What are the differences between left and right sided colon cancer, and which is a apple-core sign seen most commonly in?
Most commonly seen in left-side as the cancer has stenoses the lumen, around the outside.
What is pseudomembranous colitis?
An inflammatory condition where elevated yellow plaques form and join together, creating a pseudomembrane.
What is the difference on X-rays of small and large bowel obstructions?
How are AAAs diagnosed and investigated?
What is seen in toxic megacolon?
Very dilated colon >6cm, with extensive mucosal islands.
Oedema.
Pseudopolyps.
Label this diagram of a CT scan at T12.
Label the following CT scan of L1.
Label the following CT scan a L3.
Complete the CT scan of L3.
Identify the structures of the CT angiography.
What is riglers sign?
Where the bowel wall is clearly defined due to gas on both sides - penumoperitoneum.
What sign is seen in a caecal volvulus?
Reverse C-shaped caecum.
What sign is seen for bowel wall oedema and what condition is this most commonly seen in, in younger patients?
Thumb-printing sign.
Ulcerative colitis where the bowel wall is oedematous and thickened.
RED.
What is achalasia and how is it seen on a barium swallow?
Impaired relaxation of the lower oesophageal sphincter.
A bird-beak/ rat-tail stricture is seen.
What is seen in this barium swallow?
Oesophageal malignancy:
- Strictures.
- Rough appearance of the mucosa.
What are the tests done for testing liver function and those that test for damage?
What sign is seen in the eyes for those with Wilson’s disease?
Kayser-Fleischer ring.
What are some preventable and non-preventable causes of liver cirrhosis?
What are some signs and symptoms of liver cirrhosis?
What is the management of decompensated liver cirrhosis with the following complications:
- Ascites.
- Bleeding/ varices.
- Hepatic encephalopathy.
- Increased risk of hepatocellular carcinoma.
