Gastrointestinal Science Flashcards
Name the two directions of food movement in the GI tract.
Aboral (oral to anal) and oral (anal to oral)
Name the organs of the alimentary tract and the accessory GI organs.
Tongue, pharynx, oesophagus, stomach, liver, gall bladder, pancreas, duodenum, jejunum, ileum, caecum, colon, appendix, rectum, anus, salivary glands, biliary tree
What is the purpose of the mouth and oropharynx?
Chops and lubricates food, and begins digestion of carbohydrates
What are the two main purposes of the stomach?
Physical and chemical digestion
Describe the makeup of the small intestine.
Duodenum, jejunum, ileum. Connects by the caecum
Describe the makeup of the large intestine.
Connects by caecum. Then appendix, colon
Name the two components of the rectum and describe the purpose of the rectum and anus.
Sigmoid and descending.
Regulates expulsion of faeces
What are the accessory structures of the GI tract?
Liver, gallbladder, salivary glands, pancreas
Name the histological layers of the GI tract.
Mucosa (epithelium (NOT endo), lamina propria), submucosa, muscularis externa (circular and longitudinal muscle)
Name the two nerve plexuses of the GI tract. Where are they located?
Submucous (submucosal), myenteric (muscularis externa)
What are the four functions of the GI tract?
Motility (movement), secretion, digestion, absorption
Describe the muscle makeup of the alimentary tract.
Smooth muscle except at the extreme ends of the tract (oral and anal) where it is skeletal
Describe how muscle in the GI tract allows motility.
By circular muscle (makes lumen longer/narrower), longitudinal (shorter/fatter), very outer musclaris externa (change in absorptive area, mixing)
What is the name of food when it reaches the duodenum?
Chyme
What is the name of the pacemaker cells of the alimentary canal?
Interstital cells of Cajal
Which cellular component allows spread of action potential in the gut?
Gap junctions
Describe how an action potential is created in the gut.
‘Slow waves’ are constantly being created by pacemaker cells. When they reach above the membrane potential threshold they fire calcium APs
Describe the effect of prolonged firing of APs.
Greater force, which means greater muscle tension
Which stimuli increase the ‘resting potential’ of ICC action potentials, making it more likely for the threshold to be reached?
Neuronal, hormonal, mechanical
Describe the parasympathetic supply of the gut.
Vagus nerve, and sacral nerves S2 - S4
Describe the effects of parasympathetic and sympathetic supply to the alimentary tract.
Parasympathetic - increases digestion/secretion, relaxes sphincters/stomach.
Sympathetic - increases sphincter tone, decreases blood flow/secretion
What are the main purposes of the GI plexuses?
Myenteric - motility and sphincter control
Submucous - epithelium, blood vessels
Name the three components of GI reflex circuits.
Sensory, interneurons, effectors
Name the three types of GI reflex circuit.
Local, short, long
What is the name of a reflex which takes place entirely within the vagus nerve?
Vaso-vagal
What is glycogenesis?
Formation of glycogen
What is glycogenolysis?
Splitting of glycogen to form glucose
What is gluconeogenesis?
Formation of glucose from amino acid, glycerol, or lactic acid precursors
Describe the difference between glycogen stored in the liver and muscle cells.
In the liver it is used to regulate blood sugar. In muscle it is not available to the blood stream, just for glycolysis
Name and describe the two types of link in glycogen.
Alpha 1-4 glycosidic = straight chain
Alpha 1-6 glycosidic = branches
Which enzyme attaches primers to glucose residues for binding to glycogen?
Glycogenin
Name the intermediates of the metabolic pathway for glycogenesis.
G6P, G1P, UDP-glucose, [glucose]n+1
Name the three main enzymes in glycogenesis.
Glucophosphomutase, UTP-glucose phosphorylase, glycogen synthase
Name the main enzyme in glycogenolysis.
Glycogen phosphorylase (although many other enzymes are required to debranch glycogen)
Name the three main enzymes in gluconeogenesis, and which reactions they catalyse.
Phosphenol pyruvate carboxy kinase (PEPCK); pyruvate -> phosphenol pyruvate
Fructose-1,6-phosphatase (F1,6bP -> F6P)
Glucose-6-phosphatase (G6P -> glucose)
Which enzymes do the gluconeogenesis enzymes bypass?
Pyruvate kinase, phosphofructokinase, hexokinase
What is the name of the cycle which converts muscle lactic acid back to glucose?
Cori cycle
Why is fat an essential energy source?
Stores lots of energy, provides essential fatty acids, and for fat-soluble vitamins (A, D, E, K)
What is an essential fatty acid?
One the body needs but cannot synthesise
What are the chemical properties of lipids, TAGs, and fatty acids?
Non-polar, usually straight chain, usually cis, compact, alipathic (doesn’t form rings)
Name the three main fatty acids and their configuration.
Palmitic acid (16:0), Stearic acid (18:0), Oleic acid (18:1)
What are the alpha, beta, and omega carbons of fatty acids?
Alpha - adjacent to the carbon of the carboxyl group
Beta - adjacent to alpha
Omega - furthest from carboxyl group
Describe the process by which fat is absorbed into the mucosa.
TAGs degraded by lipases to fatty acids. These bind with monoacylglycerols, crossing the membrane to form TAGs again. These bind with other lipids/proteins to form chylomicrons
Describe the first stage of energy release from fatty acids (i.e. cytoplasmic).
Fatty acid + CoA -> acyl-CoA.
Acyl-CoA + carnatine -> acyl-carnatine + CoA
Acyl-carnatine crosses the mitochondrial matrix
Describe the second stage of energy release from fatty acids (i.e. mitochondrial matrix).
Acyl-carnatine + CoA -> acyl-CoA + carnatine
Acyl-CoA -> acetyl-CoA, FADH2, NADH, shortened acyl-CoA
Name the process by which acyl-CoA is transported into the mitochondrial matrix.
The carnatine shuttle
By which process is acyl-CoA broken down in the mitochondrial matrix?
Beta oxidation
What is the main purpose of ketones in respiration?
Can be converted to acetyl-CoA in starvation/diabetes
What are the clinical signs of ketone use in respiration?
Severe acidosis, breath smells of acetone
How are fatty acids created from acetyl-CoA?
Citrate transports to cytoplasm. Acetyl-CoA carboxylase converts to malonyl-CoA. This, plus NADH and fatty acid synthase creates fatty acids.
Which two substances promote acetyl-CoA carboxylase?
Insulin and citrate
Which three substances inhibit acetyl-CoA carboxylase?
Glucagon, adrenaline, palmitoyl-CoA
Under which conditions is lipogenesis most likely to occur?
The fed state, with a supply of carbohydrates, energy, and citrate
How are excess fatty acids stored?
In adipose, by VLDL
Why are amino acids that are not in use degraded?
There is no way to store them
Where in the GI tract are proteins degraded, how, and what into?
Stomach - proteolytic enzymes, and single amino acids or di-/tripeptides
When may degradation of proteins pose a problem to the liver?
High concentrations of nitrogen in side groups - NH4+/NH3 is toxic
Describe the transamination stage of amino acid catabolism.
An alpha-amino acid transfers the alpha-group to ketoglutarate, forming an alpha-keto acid. Also formed is glutamic acid
How is glutamic acid (the product of deamination) tranferred to the liver?
As alanine (w/ pyruvate) or glutamine (with NH4+)
Describe the de-amination step of amino acid catabolism.
Glutamate breaks off NH4+ (NAD accepting an electron to become NADH). A ketoglutarate is also formed
Describe the reactants and products of the urea cycle.
Reactants - NH4+, aspartic acid, ATP
Products - urea, fumerate, carbon skeletons
Describe how carbon skeletons of the urea cycle may be used.
Ketogenic - forms acetyl-CoA or fatty acids
Glucogenic - forms pyruvate or glucose
What is the name of the condition that blocks degradation of phenylalanine and tyrosine?
Alcaptonuria
Describe maple syrup urine disease.
Urine smells of maple syrup. Blocks valine, isoleucine, and leucine. Treated by diet, otherwise mental/physical retardation occurs
Describe phenylketouria.
Buildup of phenylalanine. Can cause severe mental retardation. Limit phenylalanine in the diet
How may a urea cycle defect be treated?
Drugs that remove nitrogen, gene therapy, low protein diet
What is the epithelium of the oral cavity and oropharynx?
Stratified squamous
What is the epithelium of the nasal cavity and nasopharynx?
Respiratory - keratinized pseudostratified columnar
Name the four papillae of the tongue.
Fungiform, circumvallate, foliale, filiform
Name the main feature of the posterior 1/3 of the tongue.
Associated with lymphoid aggregates
Name the four tonsils.
Palatine, lingual, tubual, pharyngeal
Name the three areas of the stomach.
Cardia, body, pylorus
Describe the difference between the epithelium of the isthmus and fundus of the stomach.
Isthmus mostly parietal cells
Fundus mostly chief cells
Describe the gastric pits of the cardia, fundus, and pylorus.
Cardia - deep, loose, tortous
Fundus, shallow, straight, long
Pylorus - deep, branched, coiled, high density
Describe how the pyloric sphincter differs from the pylorus.
More smooth muscle
Describe the two main features of the small intestine’s epithelium.
Microvili, crypts of Lieberkuhn
Where are Brunner’s glands, and what do they do?
Duodenum. Protect duodenum from gastric juices and neutralise chyme
What are Peyer’s patches?
Gut-associated lymphoid tissue (GALT)
Name two unique cells found in the crypts of Lieberkuhn.
Paneth cells - immune role
Stem cells - replenish the epithelium
Name the five main type of cell found in the small intestine.
Enterocyte, enteroendocrine, goblet, Paneth, stem
What two main types of cell are found in the colon?
Absorptive and goblet (lubricates)
Describe the smooth muscle alignment in the colon.
Not continuous - three strips teniae coli
How does the appendix’s histology differ from the colon?
Fewer crypts. Circular lymphoid tissue
Describe the epithelium of the anal canal.
Non-keratinized stratified squamous (becomes keratinized after the anus)
What is the main endothelium of the liver?
Simple squamous, fenestrated
Name the main components of the hepatic lobules.
Portal tracts/triads, sinusoids, space of Disse, Kupffer cells, hepatocytes, hepatic stellate cells
Describe the composition of the portal tract/triad.
Hepatic artery, portal vein, and bile duct
What is the purpose of hepatic stellate cells?
Makes connective tissue and stores vitamin A
What are Kupffer cells?
Macrophages in the liver
Describe the composition of bile.
Bilrubin (pigment of Hb that makes faeces brown), and bile salts
Which liver cells modify bile?
Cholangiocytes
Which cellular structures allow movement of bile?
Bile canaliculi
Describe the epithelium of the gall bladder.
Simple columnar
How does the gall bladder get rid of bile?
Pumps Na/Cl between epithelial cells. Osmotic pressure change causes water to rush in and remove bile
Which two main factors stimulate gallbladder action?
Vagus nerve, hormone cholecystokinin
What is the name for gallstones?
Cholecystitis
Describe the white blood cell components at each end of the pancreas. Why is this the case?
Basal end - basophilic, due to much RER
Apical end - eosinophilic, due to zymogen
How does the digestive cascade begin?
An enteropeptidase converts trypsinogen to trypsin
What is the name of pancreatic duct cells in the cavity (acini)?
Centroacinar cells
Where does the pancreas join the duodenum?
Hepatopancreatic ampulla (of Vater)
Which group of joints open the mouth?
Temporomandibular joints (TMJs)
Name the four TMJs. Which opens the mouth?
Medial pterygoid, lateral pterygoid, temporous, masseter. Lateral pterygoid opens
Describe the classification of teeth.
Upper jaw is maxillary, lower is mandibular.
1, 2: Incisors. 3: canine. 4, 5: premolar. 6,7,8: molar.
Which cranial nerves supply general sensation of the mouth?
CN V2 (maxillary trigeminal) and CN V3 (mandibular trigeminal)
Name the three salivary glands.
Parotid, sublingual, submandibular.
What is the name for the gums?
Gingiva
Describe the routes of the 2nd and 3rd division of the trigeminal nerve.
2 -> pons, foramen rotundum, face
3 -> pons, foramen ovale, TMJs
Name the four tongue muscles.
Palatoglossus, styloglossus, hypoglossus, genioglossus
Describe the nerve supply of the tongue.
Anterior 2/3: general sens V3, special sens VII
Posterior 1/3: general & special sens both IX
Tongue muscles (except palatoglossus) supplied by XII
Describe the route taken by cranial nerve VII, the facial nerve.
Pontomedullary junction, temporal bone via internal acoustic meatus, stylomastoid foramen, anterior tongue with muscles for facial expression and mouth
Name CN IX and XII.
IX - glossopharyngeal (tongue and pharynx)
XII - hypoglossal (tongue muscle)
Describe the muscle and nerve anatomy of the oesophagus.
Circular constrictor muscles overlap each other. All connect to the midline raphe. X supplies voluntary. IX and X supply involuntary. Plexus is present
Name the three types of GI contraction.
Cervical (head), thoracic, diaphragmatic
Describe the two sphincters of the oesophagus.
Top sphincter - anatomical. Bottom - z line, physiological. Intragastric pressure < intrathoracic pressure
Which condition will reduce efficacy of the oesophageal lower sphincter?
A hernia
Describe how food is swallowed. Also give the cranial nerves involved.
Lips close (VII), bolus pushed to oesophagus (XII), soft palate and larynx elevate (X), oesophagus contracts (IX, X), the pharynx raises and shortens, and peristalsis occurs
What are the three general areas of the GI tract, derived from embryological origin?
Foregut (up to pylorus, 1/2 pancreas), midgut (to proximal end of transverse colon, 1/2 pancreas), hindgut (descending colon to anus)
Name the nine areas on the ‘chest grid’.
Top row - hypochondrium, epigastric (RH, E, LH)
Middle - lumber (flank), umbilical (RL, U, LL)
Bottom - iliac fossa, pelvic (RI, P, LI)
Give descriptive words for the peritoneum.
Thin, transparent, semi-permeable
Name the three categories of peritoneal organ.
Intraperitoneal (entirely visceral), retroperitoneal (visceral in anterior only), mesentery (double visceral wrap)
Where does communication between the greater and lesser stomach sac occur?
Omental foramen
Which nerve fibres do visceral afferents travel back to the CNS with?
Sympathetic
Name the visceral afferent spinal outlets for the three Gi categories.
Foregut - T6-9, Midgut - T 8-12, Hindgut - T10 - L2
Name the four fibres in which somatic motor, somatic sensory, and sympathetic fibres are conveyed in.
Thoracoabdominal, subcostal, iliohypogastric, ilioinguinal (7-11th ICs, T12. two halves of L1)
Describe the progression of pain felt in appendicitis.
Dull and aching to sharp stabbing in right inguinal area
What is ascites?
Collection of fluid in the peritoneal cavity.
Which procedure should be used to treat ascites? Why must care be taken?
Paracentesis (‘abdominocentesis’). Must drain lateral to rectus sheath, to avoid inferior epigastric artery
What is the name for pain that comes and goes?
Colicky pain
Which four factors should be considered when assessing pain?
Location, character (visceral, somatic), referral pattern, and timing
At which levels are the abdominal organs supplied by sympathetic nerves?
T5 - L2
Describe how the sympathetic supply reaches the organs of the abdomen from the CNS.
Abdominopelvic splanchnic nerves -> prevertebral ganglia -> periarterial plexus (hitches a ride)
How does the adrenal gland’s sympathetic innervation differ from normal sympathetic supply? Where?
No synapse at the ganglia, synapses directly with cells. T10 - L1
Where are foregut, midgut, and hindgut pain typically felt?
Epigastric, umbillical, pelvic
Name the main regions of the stomach. What are the two halves called?
Fundus, body, antrum, pylorus. Orad, caudad
How does activity of the orad stomach break down food?
Weak tonic contractions with low amplitude. Minimal mixing.
What may increase or decrease rate of orad contractions?
Vagal increases, gastrin decreases
How does activity of the caudad stomach break down food?
Slow waves that reach potential. Retropulsion against the pylorus breaks down food (faster velocity) and allows it to pass through
What is the name for the wave that passes from caudad stomach through to the duodenum?
The antral wave (/pump)
Which three factors change rate of caudad stomach antral waves?
Rate of emptying, distension, consistency
Which factors decrease rate of stomach emptying?
Neurons and hormones (fat, acid), hypertonicity, distention
Name the two types of epithelium in the stomach regions and which cells they primarily are composed of.
Orad - oxyntic, parietal
Caudad - pyloric, chief
Which chemicals may the orad stomach epithelium secrete?
HCl, peptinogen and pepsin, intrinsic factors, gastroferrin, mucus
Which chemicals may the pyloric stomach epithelium secrete?
Gastrin (increasing HCl), somatostatin (decreasing HCl),mucus
There are two pathways of secreting H for HCl in the stomach - direct and indirect. Briefly describe them.
Direct - ACh, gastrin, or histamine may act directly on mucosal cells, or ACh/gastrin may act on ECLs to activate histamin release
What is the name of a chemical which promotes secretion from a cell?
A secretagogue
Which chemicals prevent H+ secretion from the stomach epithelium?
Somatostatin and prostaglandin
By which chemical pathways do the secretagogues for H+ in the stomach epithelium act?
ACh/gastrin - IP3 and PIP2
Histamine - adenylyl cyclase
Name the three secretory phases. Describe them.
Cephalic - ACh, gastrin, and histamine released
Gastric - distension causes secretion.
Intestinal
Which factors will decrease acid secretion in the stomach?
Food buffers, pH, D cell inhibition
Which channels are involved for H+ secretion in the stomach?
K+, Cl- (CFTR), Na/K ATPase, H/K ATPase, Cl-/HCO3 symporter
What is segmentation?
Contraction of the circular muscle in the intestine to divide chyme into segments, breaking it down
What is the mechanism of segmentation? What may affect its rate?
Slow wave thresholds - gastroileal reflex, or autonomic innervation triggers and increases/decreases respectively
Which two main hormones trigger H+ release in the stomach?
Gastrin and secretin
Which two main hormones inhibit gastric emptying?
Gastric inhibitory peptide (GIP), and glucose-like protein 1 (GLP1).
Which hormones trigger the MMR, and appetite respectively?
Motilitin, ghrelin
Describe the actions of the stomach hormone cholecystokinin (CCK).
Inhibits gastric emptying, pancreatic enzymes, and Oddi sphincter tone. Promotes secretion and bile
Which factors promote succus entericus, and which inhibits it?
Distension, irritation, gastrin, CCK, secretin, vagal activity increase, sympathetic activity decreases
What are the two components of succus entericus, and where do they come from?
Mucus, aqueous salt
Goblet cells, crypts of Lieberkuhn
Which channel proteins are mainly associated with succus entericus release?
Na/K ATPase, Na/K/2Cl cotransporter, CFTR
What is the name of the electrical activity of peristalsis?
Migrating motor complex
What is the main purpose of the migrating motor complex?
A housekeeping function - cleans up
Which factors may promote peristalsis, and which supress or inhibit it?
Promotes - motilitin
Suppresses - gastrin, CCK
Inhibits - vagus, eating
Describe the difference between the exocrine and endocrine pancreas.
Exocrine - digestive juices containing proteases, lipases, amylases etc from acinar (centroacinar) cells
Endocrine - glucagon/insulin from islets of Langerhans
What is the purpose of pancreatic duct cells?
Secrete alkaline HCO3-, neutralising chyme and protecting the mucosa from self-digestion
Name the five main proteases.
Elastin, chymotrypsin, trypsin, carboxypeptidase A & B
Name the two stages of assimilation.
Digestion and absorption
Briefly describe the breakdown of carbohydrate.
Starch -> oligosaccharides (alpha-amylase) -> monosaccharides (oligosaccharidase)
Describe the actions of the carbohydrate-lytic enzymes.
Alpha-amylase breaks alpha 1-4 glycosidic links internally. Oligosaccharidases break terminal a 1-4 links
Name four of the main oligodendrocytes.
Maltose, sucrose, isomaltase (all faster than absorption) lactase (slower than absorption)
Name the main entry and exit channels of glucose in enterocytes.
Entry - SGLT1 (Na/glucose symporter), GLUT5 (fructose entry), GLUT2 (all exit)
Briefly describe the breakdown of protein.
Protein -> peptides (HCl, pepsin) -> oligopeptides (trypsin, chymotrypsin, elastase, carboxypeptidase A/B) -> amino acids (membrane protein)
Describe the difference between endopeptidases and exopeptidases.
Endo- break down to 2-6 peptide chain
Exo- break down to single amino acids.
Trypsin, chymotryspin, elastase are endo
Carboxypeptidase A/B are exo-
Describe the movement of amino acids in enterocytes at the apical and basolateral membranes.
Apical - 7 methods (5 require Na)
Basolateral - bidirectional. 3 efflux 2 influx
How are di/tri/tetrapeptides absorbed in the enterocyte?
Absorbed by H+ methods, degraded within the cell
Name the two main enzymes associated with lipolysis.
Gastric and pancreatic lipase
Describe how most lipids/fats are broken down outside enterocytes.
Micelle formation. Outer lipids hydrolysed by pancreatic lipase, replaced by inner lipids, shrinking micelle
When fats have been broken down, they typically have around 12 carbons. What happens to those > 12, and < 12?
< 12 - diffusion
> 12 - chylomicron storage
Describe the role of bile salts in fat degradation.
Bile salts increase surface area, but block access by lipases - colipase fixes this
Describe the problems that may arise from lack of bile salts.
Steahorroea (fat in stool), and fat-soluble vitamin deficiency
Which drugs should be used to treat hypercholesterolaemia?
Ezetimbe - NPC1LP1, statins
Why is iron important physiologically?
Component of Hb (2/3 of body store)
How is iron absorption/degradation matched?
By the duodenum
Describe the problems caused by a lack/excess of iron.
Anaemia, toxicity to the liver, heart, pancreas
Describe briefly the absorption of Fe3+ into enterocytes.
Absorped by channel protein, (can be stored by apoferratin), exits by ferraportin. Transported across by mobilfarrin. Reduced by a factor to Fe2+
Name the reduction factors for Fe3+.
HCl, vitamin C, Dctyb (duodenal cytochrome B), gastroferrin
Describe how haem may be degraded in enterocytes.
Degradation to Fe2+ and bilverdin by haem oxidase
Which factor increases absorption of iron, and which decreases ferraportin expression?
Absorption - blood loss
Ferraportin - hepcidin
Describe vitamin B12.
Not water soluble. Not in vegetables - vegans may suffer from insufficiency
Which three factors do fat-soluble vitamins require to be absorbed?
Bile secretion, intact mucosa, mixed micelles
Describe the absorption of calcium in enterocytes.
Passively absorbed (paracellular), actively (transcellular). Mostly active in chyme. Regulated by 1,25-dihydroxyvitamin D (calcitrol) and parathyroid
Describe where each layer of GI histology originates embryologically.
Visceral mesoderm - lamina propria, muscularis mucosae, muscularis externa, CTs
Endoderm - epithelium, associated ducts/glands
Neural crest - ENS, Meissner’s, Auerbach’s plexuses
Which embryo landmarks does the intestinal mesentry originate from?
(Ventral) falciform ligament, lesser omentum
(Dorsal) mesogastrium, mesoduodenum, mesocolon
When are the oesophagus, circular muscle, and longitudinal muscle formed?
Week 4, 5, 8
Describe what occurs during week 4 of gastrointestinal development.
Caudal foregut dilates. Dorsal border grows and rotates 90 degrees
Duodenum formed from caudal foregut (1, 2) and cranial midgut (3, 4)
Describe how the liver is developed during embryological growth.
Liver bud -> mesoderm of the septum transversum, which forms haematopoetic, Kupffer, and connective cells
Endoderm -> hepatocytes, biliary tree
Describe how the pancreas is developed during embryological development.
Dorsal pancreatic bud -> dorsal duct -> main duct
Ventral swaps sides (R->L) and becomes retroperitoneal
Ventral is bilobed, wrapping round and forming the annular pancreas
Describe the formation and development of the spleen during embryological development.
W5, from mesoderm. Haemopoetic then lymphatic
Lobes becomes notches
Describe the development of the midgut through embryological growth.
(bottom half of duodenum to proximal 2/3 colon)
w4 - yolk sac communicates with midgut. YS narrows to form the vitelline duct.
Rotates out as an outgrowth to form structures
w10 - re-entry (small intestine first, caecum last)
Name the main defects that can occur with midgut development.
Meckel’s diverticulum
Vitelline cyst/fistula
Which embryological structure forms the perineal body, anal membrane, and anorectal canal?
The cloaca and cloacal membrane (hindgut)
Name the main defects that can occur with anal formation.
Urorectal, rectovaginal, and rectoperineal fistulas.
Name the three main organs associated with bile and their role in this system.
Spleen (formation of bilirubin), liver (converts to bile), gallbladder (stores/concentrates bile)
Why is bile important?
To aid in absorption of fats in the small intestine.
What is the name of the major artery which supplies the foregut organs? How does it divide?
The celiac trunk - splenic, left gastric, hepatic trifurcation
The celiac trunk trifurcates. What does each division then bifurcate to?
Gastroduodenal and superior pancreatico-duodenal
Describe the spleen.
Intraperitoneal. Pain felt in left hypogastric region. Ribs 9-11. Moves with respiration
Describe the blood supply of the stomach.
L/R gastric arteries (lesser curvature)
L/R gastro-omental arteries (greater curvature)
Both sets anastamose.
What is the name of the vessel that supplies the gallbladder with blood? Where does it arise?
The cystic artery. The right hepatic artery
Describe the pain supply around the gallbladder.
Visceral afferents T6-9. Pain felt in epigastic/hypogastric regions (+/- referral to right shoulder)
Describe the division of the liver.
4 anatomical (L/R/quadrate/caudate) 8 functional (I-VIII), each with own vessel set Segmentectomy can be performed
Describe the most common cause of hepatomegaly.
Increased central venous pressure means backup through IVC and hepatic veins. No valves
Name the two pouches surrounding the liver.
Hepatorenal (Morison’s), subphrenic
Name the main veins surrounding the liver.
Splenic, inferior/superior mesenteric, hepatic portal vein, IVC (see notes for assembly)
Name the three main ligaments surrounding the liver, and what they attach to.
Coronary - diaphragm
Falciform - anterior abdominal wall
Ligamentum teres - umbilical vein remnant
What is the difference between paracellular and transcellular transport?
Transcellular occurs through cells, paracellular through tight junctions
Lymphoid tissue is typically found in two different types in GI tissue. Describe these.
Scattered - typically crypts
Organised - Peyer’s patches
Describe the process by which T cell activation of dendritic cells causes them to migrate to the lumen.
T cells (guided by CCR7, L-selectin) Paracellular transport Maturation of dendrites (a4B2, CCR9) Drains to thoracic duct Attaches by MaDCAM1
Which feature of dendrites allows greater neutralisation of pathogens in the GI tract?
Extension across cells into the lumen
Describe the composition of the humoural response in the GI mucosa.
80% IgA (a J dimer), 15% IgM, 5% IgG
Describe, in general, non-specific terms, the role of commensals in the GI tract.
Assist in hyporegulation of immune/T cells, prevents maturation of dendrites
Describe the specific pathway in which T cells cause genetic transcription of immune factors.
T cells activate IKK pathway
This phosphorylates IaB
This moves NFaB into the nucleus to bind to DNA
Which specific chemicals do commensal organisms in the GI tract release to downregulate NFaB and dendrite maturation?
NFaB -> PPARgamma
IaB -> don’t need to know (just be aware)
Dendrites -> PGE2, TGF-B, TSLP
How can T cells destroy virally infected GI mucosal cells?
MHC class I, perforin/granzyme/FAS-ligand paths
How can non-specific (innate) immune cells stimulate a response locally in the GI tract?
PRRs trigger the NFkB path, releasing chemokines, cytokines, and defensins
Describe the relationship between dendrites and activation of T cells.
Immature dendrites activate TH3/Treg
Mature dendrites activate TH1/TH2
Describe the role of TH2 cells in GI mucosal immunity.
Activates eosinophils, mast cells, and stimulates B cells to release IgE. Can also stimulate repair/mucus secretion in mucosal cells
Describe the role of TH1 cells in GI mucosal immunity.
Stimulates B cells to produce IgG2a, activates macrophages
Describe what occurs when mucosal immunity is disregulated.
Infected macrophages travel to lymph nodes, infecting CD4 cells, spreading the infection.
Describe the mechanism of food allergy.
Type I hypersensitivity. Cross-linking of IgE on mast cells with specific food antigens.
Describe the effects of general and local histamine release.
General -> systematic anaphylaxis
Local -> acute uritcaria (hives)/wheal and flare
What is the primary GI response to asthma and seasonal rhinoconjunctivitis?
Mucus secretion
How does Coeliac’s cause malnutrition? Which specific immune components does this involve?
Damage to the small intestine
Gamma interferon from gluten specific T cells -> IL-15 -> proliferating IEL, killing epithelial cells
What two tests should be used for diagnosing of Coelic’s disease?
Biopsy (gold standard, especially in paeds)
Serology useful for IgA levels
Describe the immunologic effects of Crohn’s disease.
Distal ileum/colon (although all GI tract can be affected)
Focal/discontinous inflammation with deep, eroding fissures (+/- granulomas)
Which specific immune components are present in Crohn’s disease?
TH1, gamma interferon, IL-12, TNF alpha
Describe the immunologic effects of ulcerative colitis.
Starts at rectum, moves proximally
Can result in arthritis/uveitis/skin lesions
Distorted crypts, monocyte/neutrophil/plasma cell infiltration
How should Crohn’s and ulcerative colitis be treated?
With NSAIDs and immunosupressive drugs
What do the following crypt cells secrete: chief, D cell, G cell, enterochromoffin-like cell (ECL), parietal, mucus?
Chief - pepsinogen, D - somatostatin, G - gastrin, ECL - histamine, parietal - HCl, mucus - mucus and bicarbonate
Describe how the crypts of Lieberkuhn are kept at a pH of 6-7 while the stomach is at a pH of 1.
Mucus/bicarbonate layer secreted by mucus cells
Is crypt secretion typically paracrine, exocrine, or endocrine?
Paracrine
Name the receptors that histamine, ACh, gastrin, and somatostatin affect.
H2, M3, CCK2, SSRT2
Describe the mechanism by which antacids can reduce indigestion.
Binds H+/HCO3- to form H2O/CO2, buffering HCl
Describe the mechanism of, indication of, and effects of misoprostol.
Prostaglandin E1 analogue.
Indicated for peptic ulcers.
Can cause abdominal pain, diarrhoea, and induce labour
Name three prostaglandin E1 analogues, other than misoprostol.
Lanzoprasole, ameprazole, pantoprazole
Describe the mechanism and effects of proton pump inhibitors.
Irreversibly binds H+/K+ ATPase.
Indicated for peptic ulcers.
Can increase pH, leading to impaired stomach defences
Describe how the treatment of H. pylori should occur with benign peptic ulcer formation.
PPIs and abx
clarithromycin, amoxicillin/metronidazole
Name the five types of anti-emetic, and which receptor they target.
Anti-histamines (H1, brain). Anti-muscarinics (M1, brain). 5-HT3 antagonists (5-HT3 receptor). Dopamine antagonists (D2). Neurokinin-1 antagonists (NK1)
Describe anti-diarrhoeal drugs.
Electrolyte replacment. Binds to u-opiate receptors.
Can be combined with atropine.
Name the three main laxatives.
Lspagula husk, lactulose, senna-stimulant purgative
How is the iliocaecal sphincter opened?
The gastroileal reflex, driven by CCK and gastrin. Opened when duodenum is distended (and closed when colon distended).
Name the main cause of appendicits.
Faecalith
Name the ions secreted and absorbed by the colon.
Absorbed - Na, Cl, H2O
Secreted - K, HCO3, mucus
Which features of the colon assist in absorption of ions?
Folds, crypts, microvilli.
Goblet cells, which secrete trefoil protein and glycosaminoglycans (host defence)
Which three methods does the colon have to move material along its length?
Haustration (like segmentation, but slower, to allow absorption). Peristalsis-like movement 1-3 times a day (gastrocolic response), defaecation
What are the main advantages of colon commensal bacteria?
Competes with pathogens, motility/mucosal integrity, vitamin K synthesis, activates some IBD drugs
What is the name of air expelled through the anus? Where can it arise from?
Flatus - swallowed air or indigestable carbohydrates
Give the main symptoms and treatment of IBS.
Diarrhoea, constipation, abdominal pain. Symptomatic relief (linaclotide constipation, amitriptyline for pain)
Give the five main functions of the liver.
Metabolism of carbohydrates, fats, and proteins. Stores vitamins and glycogen. Kupffer cells - immunity/bilirubin breakdown
Name the many components of liver primary juice.
Cholic, chenodeoxycholic acids, electrolytes (Na/K/Ca/Cl/HCO3), lipids, phospholipids, cholesterol, IgA, bilirubin, metabolic waste
What is the name of the ducts in which liver primary juice run to bile ducts?
Canaliculi
Cholelithiasis is formation of gallstones in the liver tracts. Describe treatment.
Laparascopic cholecystectomy, analgesia, atropine/GTN for biliary spasm
By which process do bile salts/acids return to the liver?
Enterohepatic recycling
Describe how some bile salts may be degraded to bile acids in the GI tract.
Bacteria can dehydroxylate
What are bile salt/acid sequestrants?
Resins. Stop bile salt/acid being reabsorbed by binding.
Name the three main bile acid/salt sequestrants/resins.
Colveselam, colestepol, colestyramine
Name the set of enzymes in the liver responsible for most metabolism reactions.
Cytochrome P450 (CCY)
Describe cytochrome P450 enzymes.
A family of monooxygenases in the liver ER
What is hepatic encephalopathy?
Failure of the urea cycle to degrade ammonia. Toxic buildup leads to incoordination, drowsiness, coma, cerebral oedema, and death.
Describe the metabolism of aspirin in the liver.
Aspirin (drug) -> salicylic acid (derivative) -> glucuronide (conjugate)
How should hepatic encephalopathy be treated?
With lactulose or antibiotics
Describe the bile flow from liver and gallbladder to the duodenum.
R + L hepatic ducts -> common hepatic
CH + cystic -> common bile duct
CBD + common pancreatic -> ampulla of Vater
Name the three main sphincters in the bile flow.
Bile duct sphincter, pancreatic sphincter, sphincter of Oddi
Which investigation may be used to visualise the biliary tree?
Endoscopic retrograde cholangiopancreatotography
Describe the main cause of extra/post-hepatic obstructive jaundice.
Gallstones/carcinoma in the head of the pancreas, causing bile to back up to the liver (forcing bilirubin into the blood)
Name the four areas of the pancreas.
Head, uncinate process, body, tail
Name the main cause of pancreatic pain. Where does it present in the patient?
Pancreatitis - epigastric/umbillical regions
The duodenum and pancreas have an intimate relationship. Describe the vasculature between them.
Superior and inferior gastropancreatic arteries (from common hepatic and superior mesenteric respectively)
Name the four areas of the duodenum.
Superior -> descending -> horizontal -> ascending
Describe the main difference between the epithelium of the jejunum and the ileum.
Jejunum -> plicae circularis
Ileum -> much smoother
Where does the duodenum become the jejunum?
At the duodenaljejunal (one word) fixture
Describe how chylomicrons are transported to venous circulation.
Through lacteals -> left venous angle
Name the four main lymphatic systems of the GI tract.
Celiac, superior mesenteric (midgut), inferior mesenteric (hindgut), lumbar
Name the eight main components of the liver function test.
Liver - AST/ALT Biliary - ALP/GGT Pancreas -amylase/lipase Prothrombin time (PT) Bilirubin (conjugated/unconjugated)
Of the enzymes in the liver function test, which are more specific? To where?
ALT - liver/hepatocytes
GGT - biliary tree
Lipase - pancreas (amylase also salivary)
Which clotting factors does the liver produce?
I, II, V, VII, IX, X, XII, XIII (1, 2, 5, 7, 9, 10, 12, 13)
What are the three causes of malabsorption?
Luminal digestion, mucosal disease, structural disease
Name the specific disease states that cause malabsorption.
Coeliac, lactase malabsorption, tropical sprue, Whipple’s, Crohn’s, Parasites, bacterial overgrowth
Name some causes of malnutrition.
Disease, hospital admission, chronic, acute, psychosocial
What are the symptoms of malnutrition?
Impaired immune response, fatigue, water/electrolyte disturbances, thinness, history weight loss, loose clothes, swallowing
What is the main tool for malnutrition, and describe it?
MUST - BMI/% weight loss/acute effects
Name the two types of tube feeding.
Enteral (nasogastric, nasojejunal, percutaneous)
Parenteral (specialist and expensive)
What is the name of the site where fluid can collect next to the colon?
Paracolic gutters
Name the three main cavities in the peritoneal cavity.
Supracolic, infracolic, paracolic gutters
The position of the appendix is variable. In which position is it usually found?
Retrocaecal
What is the name of the point at which the appendicel orifice can be palpated?
McBurney’s point
Which component allows movement of the sigmoid colon?
Mesentery
Describe the arterial supply of the GI tract from the abdominal aorta.
Celiac trunk, SMA, IMA
Splits into left common iliac, right common iliac
Lateral branches to kidneys/adrenal glands etc.
What is the name of the anastamosis between the SMA and IMA?
Anastomosis of Drummond
Name the three venous anastamoses between hepatic and systemic flow.
Ligamentum teres, distal oesophagus, rectum/anal canal
What is the name of the muscle which forms the pelvic floor? Which three muscles are these split into?
Levator ani -> iliococcygeus, pubococcygeus, puborectalis
Describe the two nerve supplies to the levator ani.
Nerve to levator ani
Pudendal (S2, 3, 4)
What is the name of the division between the colon and rectum? What anatomical level does it occur?
Rectosigmoid junction, S3
What is the name of the division between the rectum and anus?
Pectinate line
Describe the three main sphincters of the anal canal.
Internal -> sup 2/3 -> symp/para
External -> inf 1/3 -> pudendal/distension
Puborectalis -> voluntary
Give the anatomical landmarks of the 1. sympathetic supply, 2. somatic motor supply, 3. parasympathetic.
- T12-L2, 2. S2-4, 3. S2-4
Describe the course of the pudendal nerves.
Branch of sacral plexus -> greater sciatic foramen
Describe the embryonic layers as divided by the pectinate line.
Visceral and parietal
Name the three main abdominal lymph nodes.
Internal, external, and common iliac
Name the fat and loose connective tissue around the anus that communicates posteriorly.
Ischioanal fossae
Describe the linea alba and linea semilunaris.
Linea alba - from xiphoid to pubic symphesis
Linea semilunaris - lateral to anterior abdomen
Name the five layers of muscle in the abdomen and their muscle fibre orientation.
External oblique (hands in pockets), internal oblique (hands on chest), transversalis abdominus (horizontal), transversalis fascia, parietal peritoneum
Where are the sites of direct and indirect inguinal hernias?
Direct - Hesselbach’s triangle
Indirect - inguinal canal
What is the name of the structure that connects the inguinal canal to the skin?
The gubernaculum
What is the name of the area of innate weakness in femoral hernias?
Myopectineal orifice
Name the dimensions of the inguinal canal.
Superior - conjoint tendon (internal oblique + transversus abdominus)
Inferior - inguinal ligament
Anterior - external oblique
Posterior - transversalis fascia
When does a hernia become a medical emergency?
When it becomes strangulated.
