Gastrointestinal Flashcards
What layer of the trilaminar disc forms the inner linings of the digestive tract & respiratory system?
Endoderm
What weeks of development does the embryo form the primitive gut?
4-8
In weeks 4-8, what structure is the gut tube suspended from?
Dorsal mesentery
What layer of the trilaminar disc forms the epithelium of the mouth & rectum?
Ectoderm
What layer of the trilaminar disc forms the muscular & fibrous elements of the gut?
Mesoderm
What layer of the trilaminar disc forms the inner epithelium and glands of the gut?
Endoderm
Describe the 4 steps of the dilatation of the stomach & its rotation
- Fusiform dilatation of the caudal end of the gut tube. 2. Dilatation - greater dorsally than ventrally, forming the greater curvature. 3. Rotates 90 degrees clockwise around the longitudinal axis. 4. The greater curvature is now on the left, and the lesser curvature is on the right.
Is the duodenum intraperitoneal or retroperitoneal?
Parts 2, 3, & 4 are retroperitoneal
What process pulls the duodenum into a C-shaped loop in the embryo?
Rotation of the stomach
The liver bud splits into cranial & caudal parts - what structures do each consist of?
Cranial - liver and bile duct. Caudal - gallbladder and cystic duct
Which structures do the two pancreatic buds develop from - dorsal bud & ventral bud?
Dorsal bud - dorsal mesentery, ventral bud - bile duct
What structure is formed when the ventral pancreatic bud moves to lie posteriorly & inferiorly to the dorsal bud?
Uncinate process of the pancreas
What is annular pancreas?
When the ventral bud of the pancreas fails to rotate, and partially or fully encircles the duodenum.
What structures does the foregut consist of?
The oesophagus to the first two parts of the duodenum
What structures does the midgut consist of?
The last two parts of the duodenum to 2/3rds along the transverse colon
What structures does the hindgut consist of?
The last 1/3rd of the transverse colon to the proximal 2/3rds of the rectum
Stomach retro or intraperitoneal?
Intraperitoneal
Jejunum and ileum retro or intraperitoneal?
Intraperitoneal
Caecum and appendix retro or intraperitoneal?
Intraperitoneal
Transverse colon retro or intraperitoneal?
Intraperitoneal
Liver and gallbladder retro or intraperitoneal?
Intraperitoneal
Sigmoid colon retro or intraperitoneal?
Intraperitoneal
Ascending and descending colon retro or intraperitoneal?
Retroperitoneal
Tail of pancreas retro or intraperitoneal?
Intraperitoneal
Spleen retro or intraperitoneal?
Intraperitoneal
Rectum retro or intraperitoneal?
Retroperitoneal
Head, neck & body or pancreas retro or intraperitoneal?
Retroperitoneal
Kidneys, suprarenal gland & ureters retro or intraperitoneal?
Retroperitoneal
Abdominal aorta retro or intraperitoneal?
Retroperitoneal
Inferior vena cava retro or intraperitoneal?
Retroperitoneal
What process results in the formation of the umbilical cord?
Liver growth reduces cavity space and causes intestinal loop herniation
What does the superior mesenteric artery act as a rotatory axis for?
90 degree anticlockwise rotation of the midgut
At what week does the coiling of the small intestine occur?
8 weeks
What is an omphalocoele/exomphalos?
Herniation of the bowels into the umbilical cord
What layer of the trilaminar disc forms the bladder & urethra?
Endoderm
What week does the cloaca separate into the rectum and urogenital sinus?
8 weeks
What investigations does new-onset unexplained dysphagia warrant? (3)
Endoscopy, barium swallow, MRI
What investigation does epigastric pain/vomiting warrant?
CT abdo
What investigations would you perform in suspected bowel obstruction? (2)
XR abdo, CT abdo
What investigations would you perform in suspected bowel perforation? (2)
XR chest, CT abdo
What investigation would you perform in a suspected swallowed foreign body?
XR
What investigations are used for staging of oesophageal cancer? (2)
CT, PET-CT
What muscle provides voluntary control of the oesophagus?
Cricopharyngeus/Upper oesophageal sphincter
What muscle types does the oeseophagus have? (2)
Striated muscle proximally, smooth muscle distally
What muscle provides involuntary control of the oesophagus?
Lower oesophageal sphincter
What layers does the oesophageal wall consist of, inner to outer? (5)
Mucosa -> submucosa -> circular layer muscularis -> longitudinal layer muscularis -> adventitia
What foods decrease LOS pressure (relaxes)? (6)
Chocolate, fatty foods, caffeine, citrus, garlic, tomato
What drugs decrease LOS pressure (relaxes)? (11)
Alcohol, anticholinergics, beta-agonists, calcium channel blockers, dopamine, nicotine, nitrates, progesterone, oestrogen, tricyclic antidepressants
What foods increase LOS pressure? (3)
Protein, carbohydrates, refluxed acid
What drugs increase LOS pressure? (5)
Alpha-agonists, beta-blockers, cholinergics, metoclopramide, domperidone
What do parietal cells secrete, and where are they?
HCl, gastric body
What do G cells secrete, and where are they?
Gastrin, gastric antrum
What do ECL (Enterochromaffin-like Cells) cells secrete, and where are they?
Histamine, gastric body
What do D-cells secrete, and where are they?
Somatostatin, whole stomach
Function of gastrin?
Stimulates HCl secretion via histamine release & direct parietal cell stimulation, stomach distension,
Function of histamine in the stomach?
Stimulates H2 receptors on parietal cells; stimulates HCl release
Function of somatostatin?
Inhibit secretion of gastrin, ghrelin, secretin, cholecystokinin (CCK), etc.
What is Zollinger-Ellison syndrome?
Excessive gastrin secretion (10x normal upper limit), resulting in a reduced gastric pH (more acidic!)
What is pyloric stenosis?
Congenital hypertrophic pyloric stenosis - obstruction that presents from 3-6wks old, with visible peristalsis & a palpable mass after feeding. Can be acquired - ulcer scar, antral tumour, tumours of the pancreatic head
What can cause acute gastritis? (5)
Irritants (smoking, alcohol), drugs (aspirin, NSAIDs, oral steroids), severe stress (burns, trauma, surgery, shock, sepsis), radiation, chemotherapy
Characteristics of acute ‘stress’ ulcers? (5)
Does not penetrate the muscularis propia, no scarring under ulcer, no endarteritis obliterans, heals by regeneration, can be anywhere and multiple
Characteristics of chronic ‘peptic’ ulcer?- (5)
Penetrates muscularis propia, scarring under ulcer, endarteritis obliterans (arterial occlusion), heals by repair with fibrous scar, single & usually antral
Complications of peptic ulcers? (4)
Perforation, haemorrhage, pyloric stenosis, malignant change
Characteristics of gastric vs duodenal ulcers? (4)
Gastric - slightly more common in males, no genetic factors, pain on eating, slightly older average age of onset. Duodenal - much more common in males, genetic factors very important, pain relieved by eating, slightly younger age of onset.
Primary malignant gastric neoplasia types? (3)
Adenocarcinoma, malignant gastrointestinal stromal, lymphoma
Risk factors for gastric neoplasia? (8)
Genetic, blood group type A, carcinogenic diet, pernicious anaemia, operated stomach, atrophic gastritis, adenomas, more common in males >50y/o.
Gastric lymphoma type & treatment?
Mucosa Associated Lymphoid Tissue (MALT), B-cell lymphoma, treated with abx.
What do chief cells secrete? (2)
Pepsinogen, leptin
What are the stages of gastric secretion?
Cephalic - thought or oral ingestion of food, vagus nerve. Gastric - food in stomach, distension, vagal stimulation. Intestinal - food in small intestine, gastrin, followed by enteric inhibitors.
What type of feedback loop is gastrin secretion?
Negative
Function of PGE2 in digestion?
Directly inhibits parietal cells.
What can cause too little acid secretion in the stomach? (3)
Inflammation & gastric atrophy (autoimmune gastritis, H. Pylori gastritis), iatrogenic (drugs, fundoplication-related dysphagia, vagotomy), associated with infectious diarrhoea/gastric adenocarcinoma