Flashcards in GI Deck (252):
What must the GI tract convert food too?
What is the fluid balance of hype GI tract?
1.5 L saliva
2.5 L stomach secretions
9 L small intestine and pancreatic secretions
12.5L absorbed in small intestine
1.35L absorbed in large intestine
What does the lower oesophageal sphincter comprise of?
Acute angle of entry of oesophagus
Oesophagus passes through oesophageal hietus and right crux of diaphragm
High pressure in abdomen collapses oesophagus
Circular muscle of oesophagus
Folds of oesophageal mucus membrane
What are the functions of saliva?
Begin digestion of carbs
Moisten mucus membranes
Reduce breakdown of teeth
Why is saliva necessary in the mouth?
Non keratanized epithelium so vulnerable to dehydration
Mucus membrane exposed to external environment so vulnerable to infection
Teeth would decay rapidly without protection and maintainance
What are the constituents of saliva that aid its function?
What types of saliva are there?
Mucous - rich in mucin
Serous - rich in enzymes
Which salivary glands produce which types of saliva? What volume of saliva does each contribute?
Parotid - serous - 25%
Sublingual - mucus - 5%
Submandibular - both - 70%
What distinguishes the submandibular gland Histologically?
The presence of demilunes - serous glands that move back out of the acini during preparation.
What do the acinar cells secrete when making saliva?
An isotonic solution with normal cations, high iodine and consequently low chlorine ions.
How are acinar secretions modified by ductal cells?
Absorption of Na+ with less K+ excretion thus hypotonic
Exchange of Cl- for HCO3- thus alkali
How is a sodium gradient set up in saliva ductal cells?
Na+/K+ ATPase on basal membrane extrudes Na+ setting up a gradient in the cell drawing ductal Na+ in
Some K+ released into duct
Remainder of K+ excreted in cotransport with Cl- into the blood
How is HCO3- created within the ductal salivary cells?
Inward diffusion of CO2
Combination with H2O creating HCO3- and H+
H+ extruded into blood in exchange for Na+ down its gradient
How does resting saliva differ from stimulated saliva?
More hypotonic (less Na+, marginally higher K+) due to longer spent in duct
Less HCO3- and less enzymes as less stimulation for their release
How is saliva secretion controlled?
Stimulation (taste, smell, reflex) trigger increased parasympathetic stimulation to the glands - this causes increased secretion. Reduced sympathetic stimulation causes vasodilation resulting in increased blood flow
Stimulation of the sympathetic NS also increases gland activity but reduces blood flow, as a result secreation decrease
Which cranial nerves supply which salivary glands?
Parotid - CN IX - glossopharangeal
Sl and SM - CN facial via the chorda tympani
What is the term for:
Difficulty in swallowing
What can cause dysphagia?
Neurological causes - cve, myesthenia gravis, parkinsons, MS
Oesophageal causes - tumour, stricture, right atrial hypertrophy, enlarged aorta, achalaesia (lack of peristalsis due to enteric NS destruction).
How does lateral folding of the embryo contribute to the formation the GI tract?
Somatic mesoderm that surrounds the amniotic cavity pinches the yoke sac creating a tube suspended by splanchnic mesoderm lined with ectoderm.
What does craniocaudal folding cause in the GI tract?
Cuts the connection between the GI tract and the yoke sac down to one tube - the vitelline duct
What occurs at either end of the primitive gut tube?
Direct connections between endoderm and ectoderm - the stomatodeum and proctodeum
What does endoderm form in the GI tract?
What forms the GI tract muscles? What else does this layer form?
The splanchnic mesoderm.
Also forms the visceral peritoneum
What are the divisions of the gut?
Foregut - oesophagus to major duodenal papilla
Midgut - major duodenal papilla to 2/3rds along transverse colon
Hindgut - last 1/3rd of transverse colon to rectal canal (pectinate line)
How is the gut tube suspended in its cavity?
What splits this cavity?
The dorsal mesentery
Which section of the gut also has a ventral mesentery?
What does this do to the cavity?
Forgut - stomach to major duodenal papilla.
Divides the intraembryonic coelom into a right and left sac.
How do the mesenteries change around the stomach?
The stomach twists clockwise carrying the mesenteries with it. The stomach also tilts as the greater curvature (was posterior now right side) grows faster than the lesser. This causes the dorsal mesentery to become horizontal on its attachment to the bottom edge of the stomach.
What develops in the dorsal and ventral mesogastrium?
Dorsal - spleen
Ventral - liver
What does the ventral mesogastrium form in the adult?
The lesser omentum connecting the lesser curvature to the liver
The surroundings of the liver
The falciform ligament connecting the liver to the anterior abdominal wall
What does the dorsal mesogastrium form in the adult?
The splenorenal ligament anchoring the spleen to the posterior abdo wall
The greater omentum from the greater curvature of the stomach draping down then back up attaching to the transverse colon
What attaches the transverse colon to the posterior abdominal wall?
What does this form?
This forms the lesser sac in conjunction with the greater and lesser omentum
What is the communication between the greater and lesser sac called?
The epiploic foramen of Winslow (omental foramen)
What is the function of the lesser sac?
Gives the stomach room to expand
What abdominal organs are retroperitoneal?
Most of the duodenum
Acending and descending colon
What occurs with the mesentery of secondary retroperitoneal organs?
Fuses with the posterior abdominal wall becoming fusion fascia
What are the anterior abdominal wall muscles and where do the hey attach attach from superficial to deep
External oblique - runs inferiomedially from lower ribs to central aponeurosis
Internal oblique - runs superiomedially from iliac spine to central aponeurosis
Transverse abdominus - runs around the trunk from the transverse processes of the vertebra to the central aponeurosis
What two layers sit behind the 3 layers of anterior abdominal muscles?
The transversalis fascia
The parietal peritoneum
What muscles are found within the central aponeurosis? What lines border them?
The rectus abdominus
Laterally bound by Lina semilunaris
Centrally divided by Lina alba
Divided horizontally by tendinous intersections
What is the difference between superior and inferior to the arcuate line of Douglass?
Superior to it the tendons forming the aponeurosis pass either side of rectus abdominus
Below it all fibres of the aponeurosis pass in front of rectus abdominus leaving just the transversalis fascia behind.
Where is the arcuate line of Douglass?
1/3rd of the distance from the umbilicus to the pubis symphysis
Describe with an example, referred pain on a somatic nerve
Stimulation of a proximal part of the nerve causing pain to be perceived at the distal part of the nerve - e.g shingles
What fibres do visceral sensory fibres follow back to the spine?
What does this cause?
Perception of sensation of the dermatome at the level that the sympathetic fibres left the cord.
What stimulates visceral sensation?
Strong muscle contraction
Roughly where do the 3 gut regions refer pain?
Foregut - epigastric
Midgut - umbilical
Hindgut - suprapubic
Where does pain from
Appendix - umbilicus
Liver - right hypochonrium
Spleen - left hypochonrium
Retroperitoneal - central back to umbilical
Renal colic - flank to groin
Gall bladder - right hypochondriac to epigastric to right scapula tip
Diaphragm - left shoulder
What is a connection between the umbilicus and bladder called? How does it present?
Failure of closure of alantosis
Urine from umbilicus either at birth, or in later life when obstruction (e.g. Enlarged prostate) causes raised pressure.
Can cause an umbilical cyst
What is a patent vitelline duct? How does it present? He can it be differentiated from a Urachal problem?
Failure of the vitelline duct to close
Connection between bowel and umbilicus
Causes an umbilical cyst
Differentiate from Urachal cyst by injecting die and seeing if it goes to bowel or bladder.
What is the rule applied to merkals diverticulum?
2% of population
2' from the cecum within the ilium
2 types of tissue (gastric and intestinal)
Differentiate the types of congenital GI content herniation
Exampholos (omphalocele) - herniation of abdo contents including peritoneum - high rates of mortality due to concurrent abnormalities
Gastroschisis - abdominal contents without peritoneum off midline. No usual concurrent abnormalities so low mortality
What is divarication of recti?
Midline bulge due to weakness in Lina alba. Evident when sitting up.
What is the commonest abdominal hernia?
Which sex gets more femoral hernias?
What are the two sorts of inguinal hernia? Differentiate them.
Direct - bowel passes medial to the inferior epigastric vessels through a weakness in hesselbachs triangle. It passes out of the superficial inguinal ring external to the spermatic cord.
Indirect - bowel passes through the internal inguinal ring lateral to the inferior epigastric vessels, through the inguinal canal and out through the external inguinal ring within the spermatic cord. As a result can enter the scrotum.
What triangle do direct inguinal hernias pass through?
Where do femoral hernias pass?
Inferior to the inguinal ligament through the femoral canal
Why are femoral hernias more serious than inguinal hernias?
They are more likely to strangulate
What is a spigelian hernia?
A hernia medial to the Lina semilunaris at or below the arcuate line of Douglas.
What is the term for a partial hernia? What are the risks associated with this?
A richters hernia
Can strangulate without obstructing the bowel so harder to detect
What is a common complication of any operation to the abdo?
What are the main complications of a hernia?
Incarceration (not reducible)
Strangulation (painful, red, hard, non reducible mass - causes ischemic bowel)
What size of hernia is more likely to strangulate?
Small - they have a smaller opening!
What are the functions of the stomach? How does it meet them?
Store food between meals - expandable
Sterilise food - acidic
Digest food - secretes enzymes, mechanical churning, acidic
What enzyme does the stomach secrete? What cell type secretes it?
Pepsinogen from chief cells, cleaved to pepsin
Why does pepsin have an action large than just the individual breakdown of proteins in the stomach?
Proteins tend to be structural - holding other substances together, thus breaking down proteins causes the food to disintegrate increasing surface area
Where is acid secreted into the stomach (region, cell and region of cell) ?
From parietal cells located in gastric pits. Components are secreted into cannuliculi
How is acid secreted in gastric cells?
Mitochondria split h2o to h+ and oh-
oh- combined with co2 to hco3-
hco3- secreted into blood in exchange for Cl-
H+ pumped into canaliculus in exchange for K+ using ATP.
Cl- also secreted
What does the production of h+ in parietal cells of the stomach do to the blood?
How is acid secretion controlled in the stomach? What triggers/inhibits each modality?
A combination of the vagus nerve releasing ach, mast cells releasing histamine and g cells releasing gastrin.
All three methods stimulate parietal cells.
Vagus activity is triggered stomach distension, anticipation etc.
Gastrin activity is triggered by sensing polypeptides in the lumen and inhibited by sensing of low pH and by somatostatin release.
Histamine is stimulated ach and gastin, thus serves to amplify the effects of there other two.
What are the phases of control during stomach acid secreation?
Cephalic - feel, smell, taste all trigger CNx stimulation releasing acid
Gastric - stomach distension triggers CNx stimulation, peptides in lumen trigger gastrin secretion, food buffers stomach raising pH triggering gastrin secretion
Intestinal phase - stomach empties - pH drops reducing gastrin secretion, chyme enters duodenum, initially increases acid secretion then triggering somatostatin release inhibiting gastrin. Decreased stomach stretch lowers CNx activity.
Which stomach cells secrete mucus?
Why does mucus stay in position around the stomach?
Sticky so hard to displace
Thixotrophic (if disturbed becomes more runny so fills any gaps)
How does gastric mucus protect against acid?
Contains HCO3- and basic groups which buffer the acid
Constantly replaced so as it becomes saturated new is produced below.
Unstirred thus h+ has to diffuse right through to reach stomach wall
What controls gastric mucus secretion?
These increase in response to the same stimuli as acid secretion so attack is matched with defence.
What drugs increase stomach defence?
H2 receptor antagonists - eg ranitidine - inhibit the actions of histamine preventing amplification of CNx and gastrin
Proton pump inhibitors - inhibit the H+/K+ synporter a in the caniculus.
H-pylori elimination therapy
Drugs that harm stomach defences
NSAIDs - inhibit COX reducing prostaglandins decreasing mucus production
Aspirin - as per NSAIDs non-ionised in stomach so absorbed into lining then ionises causing damage
Alcohol - irritates stomach causing gastritis
How does the stomach expand?
What is the advantage of this method?
Actively relaxes under vagus nerve control
No pressure increase therefore decreased reflux
How do stomach contractions move food?
Pacemaker in cardia fires 3/minute initiates wave of contraction
Slows as stomach widens then accelerates as it narrows towards the pyloric antrum
Small particles are pushed ahead of the wave but larger ones are overtaken sorting food ready to be squirted into the duodenum
When the wave reaches the pylorus it causes contraction closing the sphincter.
What slows emptying of the stomach?
Lipids in duodenum
Low pH in duodenum
Hypertonicity in duodenum.
What is the timeframe for physiological herniation?
Week 6 to week 10
Why does the midgut herniate?
The entire GI tract expands out of proportion to the rest of the body, the midgut most of all
How can the midgut be subdivided?
On which subdivision is the cecum located?
The vitelline duct divides the midgut into a cranial and caudal limb
The cecum is on the caudal limb
What rotations does the midgut undergo? On what axis?
On the axis of the SMA
3 x 90 degree anticlockwise rotations, 1 on herniation, 2 on return
The rotation brings the caudal limb in front of the cranial (colon in front of duodenum
How does the midgut return to the abdominal cavity?
The jejunum first moving to the left side then successive return of the rest to the right side. The cecum returns to the right upper quadrant the decends.
What are the devisions of the peritoneum? What is the mobility of each?
Superior, descending, inferior, ascending.
First 3cm of superior is intraperiotoneal
. Rest of duodenum is retroperitoneal
What problems can arise from physiological herniation?
All malrotations increase risk of volvulus
Only one 90 degree turn - the colon returns first and all sits on the left with the small intestine on the right
The first turn is clockwise - the duodenum and SMA sit anterior to the transverse colon - risk of compression
Sub hepatic cecum - failure of cecum to decend - appendix then also in this region!
What effect does cell proliferation have in the GI tract?
Blocks the lumen of the oesophagus, bile duct and proximal small intestine.
What is recanalisation?
What happens if it fails?
The reopening of the areas of the GI tract that became obstructed.
Atresia (obstruction) or stenosis (narrowing) of the tract
What is the main cause of atresia in the jejunum, ilium and large bowel?
Vascular accident causing necrosis - can cause unjointed sections, holed sections or sections joined by a fibrous band.
How does the hindgut contribute to the urinary system?
Forms the epithelium. Of. The. Bladder
What forms the end. Of the hindgut?
The cloacal membrane with the proctodeum
What separates the hindgut from the alantosis?
The urorectal septum
What is the innervation to the proctodeum?
What divides the region derived from the proctodeum and that derived from the hindgut in the adult?
The pectinate line
What pathologies can effect the anal canal/rectum?
Imperforate anus - failure of the cloacal membrane to rupture
Hind gut fistula - failure of the urorectal septum to fully separate the hindgut from the alantosis (bladder)
What sort of bacteria causes stomach ulcers, what is its specifics?
Gram -ve flagellated, helical aerobe.
Produces urease breaking down urea to co2 and ammonia to produce alkali environment in stomach
How do h pylori protect themselves from stomach acid?
Produce ammonia from urea making CO2 using urease
Live under the stomach mucus layer
How is h pylori transmitted?
Who is most at risk?
Oral oral and faeco oral routes
Percentage increases with age - thought to be due to more chance of transmission when the older generation were children rather than more risk as elderly. Cohort effect!
More effected in developing countries.
What does h pylori cause?
Peptic ulcers (implicated in 95%)
Gastritis (implicated in 80%)
Small implication in GI cancer
What are the two sorts of GI ulcer?
Peptic ulcer - ulcer in the stomach or duodenum
Duodenal ulcer - ulcer of the duodenum only
What is the effect of an antral h pylori infection?
Increased acid secretion due to increased parietal cells and gastrin
Metaplasia of duodenum to stomach like columnar cells
H pylori colonise proximal duodenum
Formation of duodenal ulcers
Where do h pylori settle to cause gastric ulcers?
In the body of the stomach reducing mucus secretion (and acid secretion)
What are complications of ulcers?
Erosion through blood vessel (gastric - splenic artery, duodenal - gastroduodenal artery)
Obstruction (if near pyloric sphincter)
What are other risk factors for peptic ulcer disease?
Zollinger-Ellison syndrome (gastrin secreting tumor of the pancreas)
What is gastritis?
Inflammation of the stomach. With signs of. Inflammation on biopsy, not just a red. Stomach!
What are the main branches of the coeliac trunk?
Left gastric, splenic and common hepatic
What forms the circulation to the greater curve of the stomach? What do these arteries branch off?
The right and left gastroepiploic from the gastroduodenal and splenic respectively
What does the common hepatic artery branch into?
The right gastric, proper hepatic and gastroduodenal
What state is chyme in when it reaches the duodenum?
Acidic, hypertonic and partially digested
How is chyme made isotonic?
Water moves from interstitial space between the cells
What is the exocrine pancreas Histologically?
Compound branched acinar glands
Acini drain into intercalated duct
Intercalated duct drains to intralobular duct (simple cuboidal)
Intralobular duct drains to interlobular duct (stratified cuboidal)
Interlobular ducts into major or minor pancreatic duct
What enzymes do acinar cells secrete?
What are the vesicles containing the pancreatic enzymes called in the acinar cells?
What triggers the release of zymogen granules?
CNx, hypertonic chyme and lipids stimulate APUD cells in the duodenum to release cholecystokinin (cck)
Cck stimulates zymogen granule release
How are pancreatic enzymes activated?
Enterokinase in intestinal brush border cleaves trypsinogen into trypsin. Trypsin cleaves all the others.
How is premature activation of trypsin prevented?
Alpha 1 antitrypsin, a protease inhibitor, stops its activation within the pancreas.
Other than zymogen granules what else dose the pancrease release?
Hco3- from duct cells
After alkali tide hco3- is high in the blood
Forms co2 and water
Co2 enters cell and recombines with water forming h and hco3
H+ extruded in exchange for sodium (using the sodium gradient from Na/Katpase)
Hco3- extruded into duct
How are pancreatic duct cells regulated?
Increased production at alkali tide
Secretin released from terminal jejunum in response to lowered pH enhanced by cck
What are the two broad functions of the liver?
What are examples of each?
Effecting the blood - plasma protiens, cholesterol synthesis, metabolism and detoxification)
Effecting the gut - bile production
What are the functions of bile?
Excretion of waste products
How is the liver structured on a macroscopic scale?
Anatomically divided into four lobes, the left, the right, the Quadrate and the caudate
Surgically (functionally) has 8 lobes each with its own blood supply
Which of the caudate and the quadrate lobes is superior? Which of the main lobes do they belong too?
Caudate superior (posterior)
Belong to the left
What are the two microscopic structures of the liver?
Hepatic acini model (functionally)
Hepatic lobule model (structurally)
What is the hepatic lobule model of the liver?
The structural model
Central branch of hepatic vein
Surrounding branches of portal triad (portal vein, bile duct and hepatic artery).
Blood flows from portal vein and merges with that from hepatic artery providing oxygenation. Passes through sinosoid lined with hepatocytes to hepatic vein. Bile drains in reverse back down blind ended canals to the bile duct.
What is the hepatic acini model of the liver?
Portal triad centrally with hepatic vein branches peripherally
Zones away from the triad towards the hepatic vein 1-2-3
Zone 3 most vulnerable to injury as further from O2 supply
What vessels converge to form the portal vein?
Splenic (which also includes inferior mesenteric), superior mesenteric, right gastric and left gastric (which also includes oesophageal)
What are the components of bile? What produces each?
Bile acid dependant components from acinar like cells - bile acids and pigments
Bile acid independent components from duct cells - HCO3-
What are bile acids?
What are examples?
How are they altered and why?
Eg. Cholic acid or Chenodeoxycholic acid
Conjugated to glycine or taurine to form bile salts to produce amphipathic structure.
What are bile pigments?
Describe the cycle of bilirubin
Haemoglobin to biliverdin to bilirubin in body
Transported to liver on albumin as insoluble
In liver bilirubin undergoes glucuronidation making it soluble
Conjugated bilirubin excreted in bile
Not reabsorbed due to large size
In terminal ilium bacteria convert some into urobilogen
Urobilogen reabsorbed and excreted by kidneys
What enzyme causes glucuronidation of bilirubin?
In which disease is it deficient?
Udp glucuronosyl transferase
How does bile increase the efficiency of lipid breakdown?
Amphipathic bile salts emulsify lipids increasing surface area
Colipase links bile salts to lipase for maximal efficiency
What occurs with cleaved fatty acids in the GI tract?
Micelles formation with cholesterol and bile salts
Fatty acids absorbed in proximal small intestine
Bile salts continue to terminal ileum where they are absorbed, some are lost in the gut.
How does the body deal with the timing of the return of bile acids to the liver?
Reabsorbed bile acids return to the liver after several hours prior to the next meal. As a result they are not immediately required so are stored in the gallbladder. Cck causes release from the gallbladder when chyme stimulates apud cells.
How does the gallbladder condense bile?
Na and Cl ions are removed with concurrent osmotic movement of water out of the bile.
What sort of gallstones are there? Why do they form? What other diseases may bring about gallstones?
Pigment stones (increased bilirubin, reduced bile salts)
Cholesterol stones (excess cholesterol, reduced bile salts)
High bilirubin can result from haemolytic anaemia
Low bile salts can result from absorption disorders such as chrones
What are the three classifications of jaundice?
Example of each
Blood test result of each
Pre-hepatic - e.g. Haemolytic anaemia - liver overwhelmed with bilirubin and unable to conjugate it all. Shows: raised unconjugated bilirubin, raised lactate dehydroginase
Hepatic - e.g. Hepatitis - liver non functioning. Shows: Mixed conjugated and unconjugated bilirubin, raised AST and ALT, deranged INR
Post hepatic - e.g. Gallstones - bile unable to leave. Shows: raised conjugated bilirubin, raised ALP, no urobilogen
Where can gallstones obstruct - what conditions are associated with each obstruction?
Cystic duct - cholecystitis
Common bile duct - billary colic, ascending cholangitis
Pancreatic duct - pancreatitis
What are the 3 main classifications for GI toxin defence?
Give some examples of innate physical defences of the GI tract
Deification and vomiting
Describe salvias protective role against toxins?
Washes toxins to stomach
Contains IgA reducing adherence of pathogens
Alkali neutralising pathogen acid
What pathogens can survive stomach acid?
How do intestinal secretions protect against toxins?
Bile acts as a detergent reducing adherence and pancreatic enzymes contain proteases
Which regions of the GI tract are anaerobic?
Large and small intestine
What is the lack of saliva called? What infection can it lead to? What causes this?
Staphylococcus aureus (gram +ve aerobic cocci)
What is the infection risk of anti acids?
Decrease stomach acidity increasing risk of
How can mycobacterium be cultured from the stomach? Why?
Stomach washes in the morning as overnight pt coughs up and swallows mucus. Mycobacterium tuberculosis is acid fast.
Do you get bacteria in the small bowel? If not why not?
The small bowel is normally sterile due to
Secretions containing proteases and detergents
Lack of nutrients
Shedding of epithelium cells
What specific mechanisms aid innate cellular defences protect the GI tract?
The portal system brining all absorbed substances to the liver
Kupffer cells (fixed macrophages) in the liver
Where are the main aggregations of GALT in the GI tract?
Tonsils (pharangeal, palatine, linguinal)
Payers patches in small intestine mucosa, becoming more common the more distal travelled.
How does GALT work?
Covered in a specialised epithelium that samples lumen (essentially the afferent lymph vessel)
Centre is many B cells surrounded by lymphocytes and macrophages
Activated B cells travel to nearby lymph nodes exaggerating any response.
What can cause appendicitis?
What is the inflammation of a lymph node of the mesentery called?
What causes it?
What can it be confused with?
What is the main complication
What is typhoid?
Fever, headache, abdo pain, hepatosplenomegaly, lymphadonopathy, macupapular rash
Infects payers patches in terminal ilium which can cause perforation,
Why does alcohol damage the liver?
Build up of acetylaldehyde (midstep of metabolism) damages cells
NADP - NADPH favours increased fatty acid synthesis
Fat deposited in zone 3
What are causes of hepatitis?
Inflammatory bowel disease
Alpha 1 antitrypsin deficiency
What is fulminant hepatic failure?
Failure of the liver within two weeks causing encephalopathy
What is liver cirrhosis?
Stellate cells in the space of diss secrete collagen
This causes fibrosis of the liver causing necrosis of hepatocytes
It is irreversible
What is the cause of portal hypertension?
Increased resistance to blood flow increasing pressure in the venous system.
Where are risks of portosystemic anastamosis formation in oesophageal hypertension?
Umbilicus - caput medusae following recannulisation of ligamentum teres
Rectum - haemorrhoids
Oesophagus - oesophageal varacies
What are other causes of portal hypertension other than cirrhosis?
Portal vein thrombosis
Schistosomiasis (Shistosoma mansoni)
Hepatic vein obstruction
What causes ascites?
Low albumin lowering oncotic pressure
Renal sodium retention causing water retention
Increased hydrostatic pressure due to portal hypertension
What are liver signs (other than portal hypertension and ascites) and why
Puritis - bilirubin itches
Spider naevi - high oestrogen due to decreased metabolism
Palmer erythema - high oestrogen due to decreased metabolism
Leukonychia - hypoalbumaemia
Clubbing - unknown mechanism
Encephalopathy - build up of ammonia due to reduced action of liver and from diet in portosystemic shunts.
What is Wilson's disease?
What is the pathomomonic sign
Autosomal recessive disease
Inappropriate deposition of copper during transport
Causes hepatitis, dementia
Kayser fleischer rings
What is the cause of most liver tumours?
Secondaries to colorectal cancer
What is the cause of pancreatitis (the common link to all causes)
What are the acute and chronic effects
Innapropriate digestion of its own tissues by pancreatic enzymes.
Causes necrosis, oedema and haemorrhage acutely
Causes fibrosis and calcification chronically
What are the causes of pancreatitis?
What general adaptions do the intestines have to maximise absorption?
Large surface area
How is surface area maximised in the small and large bowels?
Small - valvular conniventes, folding of the mucosa into villi, brush borders of microvilli
Large - crypts of leiberkuhn, microvilli
How does the small intestine move?
Contraction of smooth muscle intermittently along the course controlled by pacemakers activating different sections at different times. Faster proximally then slowing distally. Food pushed both ways but as faster proximally then general movement distal.
True peristalsis once or twice a day to clear the intestine of debris
How does the large intestine move?
Much like segmenting moving contents back and fourth but faster proximally so moves distally.
Propels faeces into rectum, usually following a meal
How are muscles organised in the large intestine?
Circular layer contracted permanently at set points creating houstra
Longitudinal layer condensed into the three taenia coli
How is deification controlled?
Two sphincters internal and external (NOTE, internal next to bowel, external behind internal, not further out)
Internal under autonomic parasympathetic control
External under voluntary control
Pressure receptors sense increasing faeces - sacral reflex that can be modified by higher centres - overridden if pressure is too high!
What are the parts of the end of the colon
The sigmoid colon, the rectum (the pelvic part of the GI tract), the anal canal, the anus
What are the components of carbohydrates?
Amylose (alpha 1-4 chains)
Amylopectin (alpha 1-4 and alpha 1-6 chains)
What are the subcategories of the amylases?
Alpha amylase - alpha 1.4 bonds between glucose
Isomaltase - alpha 1.6 bonds between glucose
Maltese - maltose to 2 glucose
Sucrase - sucrose to glucose and fructose
Lactase - lactose to glucose and galactose
How are glucose monomers transported into enterocytes? Through what channels?
Synport using a sodium ion gradient set up by Na/KATPase on the basal membrane
How is glucose expelled from the basal cell membrane of enterocytes?
How do fructose and galactose enter the enterocytes?
Explain the principle of oral rehydration salts
Giving sodium and glucose together at optimal concentrations maximises absorption and osmotic pressure drawing water with it out of hitherto GI tract.
What is special about a neonatal Gi tract re. Proteins?
It is open - IgG from mothers milk can pass between enterocytes
In non-neonates how are proteins broken down in the GI tract by specific proteases?
Pepsin - nr aromatic amino acids
Trypsin - nr basic amino acids
Chemotrypsin - nr aromatic amino acids
Carboxypeptidase - c terminal
Where is protein breakdown completed?
The brush border
How can amino acids be absorbed into enterocytes?
Alongside Na gradient
Active pumping of h+ into lumen
How are electrolytes absorbed in the GI tract? (Na, Cl, Ca, Fe)
Na - gradient set up by active pumping on basal membrane
Cl - follows Na to equalise charge
Ca - active transport on basal membrane creating gradient
Fe - combines with gastroferrin, then transferrin, into enterocytes, back to free ion, into blood then back onto another transferrin
How is vit b12 absorbed?
Combination with intrinsic factor in stomach then absorbed in terminal ilium
What areas of the GI tract may damage result in vit b12 deficiency?
What is absorbed of note in the terminal ilium?
What changes in the small intestine between the three areas?
Less villi / valvulae conniventes distally
More payers patches distally (max in terminal ilium)
Duodenum - APUD cells, brunners glands
Jejunum - secretin releasing cells
Ilium - absorption of bile salts, urobilogen and vit. B12
What deficiencies could result from surgical removal of the stomach?
Iron (no gastroferrin)
Vit b12 (no intrinsic factor)
What artery connects the inferior and superior mesenteric arteries?
The marginal branch
What are the branches of the SMA
What are the branches of the IMA?
The major specific symptoms of chrones are:
Infrequent gross bleeding
The major specific symptoms of UC are
Always gross bleeding
Rare perianal disease
Which IBD is improved by smoking?
What are the usual ages and genders for IBD
Chrones - 15 to 30 or over 60
UC young adult females
Other than chrones and UC what other IBDs are there?
What are the specific signs of chrones?
Mouth to anus distribution
Lines of ulcers
The major signs of UC are
Continuos from rectum inwards
No fistulation, granulomas, cobble stoning, fibrosis
What are the radiological signs of chrones and UC?
Chrones - string sign of kantor
UC - collar button ulcer
What are general symptoms of IBD
Bloody diarrhoea (more UC)
Faecal urea / pneumaturea (chrones)
What are differentials for IBD
What are extra intestinal symptoms of IBD
Increased cancer risk
Primary sclerosing cholangitis
How to Dx IBD
What is the progression of UC
What are treatments for IBD
Topical therapy for proctitis
What are some benefits of commensal GI bacteria?
Vitamine synthesis (K, B12, thiamine)
Prevent colonisation by pathogens
Kill non indigenous bacteria
Stimulate malt development
Stimulate natural antibodies
Alter environment (e.g. Lactobacilli in vagina convert glycogen to lactic acid)
What is the main bacteria in the GI tract? What is its classification?
Bacteroides fragalis - anaerobic gram -ve. Bacilli
Give an example of a gram +ve anaerobic bacilli from the GI tract?
Clostridia sp. (e.g. Clostridium difficile / tetani)
What are some gram +ve cocci associated with the GI tract
What are some gram -ve cocci associated with the gi tract
What gram +ve aerobic bacilli are associated with the GI tract?
Give a few gram -ve bacillus aerobics associated with the GI tract
What causes oral thrush?
Which bacteria is associated with infective endocarditis post dental procedures? What makes this mores likely?
Streptococcus viridans (gram +ve aerobic cocci)
What is the most common cause of tonsillitis? What percentage?
What is the most commonest cause of bacterial tonsillitis?
Streptococcus pyrogens (gram +ve aerobic cocci)
What is the risk of GI surgery?
What abx mitigates this?
Peritonitis from GI bacteria
Most GI bacteria are anaerobic therefore treat with metronidazole
Gentamicin as a general broad spectrum
Commonest causes of uti
Escherichia coli (gram -ve aerobic bacilli)
Enterococcus faecalis (gram +ve aerobic cocci)
On a uti culture you find a gram -ve aerobic bacillus, what is it likely to be?
On a uti culture you find a gram +ve aerobic bacillus, what is it likely to be?
Lactobacillus - not the causitive organism!
On a uti culture you find a gram -ve aerobic cocci, what is it likely to be?
Neisseria gonorrhoeae - not a uti!
On a uti culture you find a gram +ve aerobic cocci, what is it likely to be?
There is a green pus covering someone's legs, what is the likely cause?
Pseudomonas aeruginosa (gram -ve aerobic bacilli)
A patient has truisms and an arching back. What is the infection. What is the term for the arching back. What is the treatment?
Airway and ventilation if RS involvement
Benzos for spasm
What is the causitive organism for gas gangrene?
Clostridium perfringens (gram +ve anaerobic bacilli)
What is the big complication of clostridium difficile infection, what sort of bacteria is it?
Pseudo membranous colitis
Gram +ve anaerobic bacilli
What are the two main types of oesophageal cancer? In what part of the oesophagus is each more common? What risk factors are associated with each?
Squamous cell carcinoma - upper 2/3rds - associated with red meat, tannin, HPV, smoking and geography (China)
Adenocarcinoma - lower 1/3rd - associated with barrets oesophagus (and therefor GORD) progressing through metaplasia then dysplasia.
What are symptoms of oesophageal cancer?
Dysphagia (solids, progressive)
Constant pain (suggests invasion)
What is the prognosis of oesophageal cancer?
Around 5% 5 year survival due to late presentation.
What is the general classification of stomach tumours? What are the subdivisions?how do they appear Histologically?
Intestinal (well differentiated - glands like)
Diffuse (poorly differentiated - signet ring cells poor cohesion)
What are macroscopic signs of stomach cancer?
How is gastric cancer staged?
Early (localised to mucosa / submucosa) vs late (
How does gastric cancer present?
Virchows node enlargement
What drugs other than standard chemo may be of use in gastric adenocarcinoma?
Herceptin if her2 expressed
Other than adenocarcinomas what other cancers can effect the stomach?how are they treated?
Gastrointestinal stromal tumours from the mesenchyme. Treated with surgery and imatanib
Gastric lymphomas. H pylori eradication can be curative if don early enough! Otherwise surgery.
What do most tumours of the large intestine develop from? What implication does this have?
More polyps means more cancer risk
What are most large intestine polyps?
Benign spontaneous adenomas
What signs on an adenoma polyp in the large bowel make it more likely to become malignant?
What genetic conditions raise risk of colon cancer?
Familial adenomatous polyposis - autosomal dominant. 100s to 1000s of adenomas thus high risk of one becoming malignant
Gardeners syndrome - like fap but also ostomas of skull
Hereditary non polyposis colon cancer (HNPCC) - autosomal dominant, polyps form and progress rapidly to cancer, preference for right colon so hard to see.
What mutations are required for a colonic adenoma to mutate into an adenocarcinoma?
Are most colorectal cancers sporadic or inherited?
65 - 90% sporadic
What are risk factors for colon cancer?
High fat diet
Slow gut transit time
Low fibre diet
What are symptoms of colorectal cancer?
Altered bowel habits
Pr bleeding / occult blood
What is the term for feeling incomplete emptying of bowels post deification?
What ct scan sign may show?
Apple core stricture
How can colorectal cancers be staged?
Dukes score - A (confined to wall) B (local spread clear lymphatics) C1 (lymph nodes involved) C2 (highest lymph nodes involved)
What are most pancreatic cancers?
Most are ductal
What are risk factors for pancreatic cancer?
Chronic pancreatitis (therefore, alcohol, CF etc)
Where do most cases of pancreatic cancer occur?
Head or ampulla of vater
How can pancreatic cancer present?