GI system Flashcards
How is oesophageal reflux from the stomach prevented?
- Oesophageal sphincter
- Acute angle of entry of oesophagus into stomach producing a valve like effect.
- Mucosal folds at oesophagogastric junction act as a valve.
- Right crus of diaphragm acts as a ‘pinch cock’.
- +ve intra-abdominal pressure compresses walls of intra-abdominal oesophagus, helping to collapse it.
Define dysphagia
Difficulty swallowing
What may cause dysphagia?
- Neuro-muscular dysfunction, may be due to a stroke, parasitic infections.
- Oesophageal tumour
- Obstruction
- May be congenital
What is peristalsis?
a coordinated wave of contraction behind bolus of food, with relaxation ahead, to propel bolus forward. Involuntary- from intrinsic neuromuscular reflexes.
What is Odynophagia?
pain on swallowing
What is a stricture?
narrowing
What can cause odynophagia?
Severe oesophagitis, a stricture
Name some mechanical causes of dysphagia
enlarged aorta, mediastinal tumour, enlarged LA, oesohpageal or stomach tumours, hiatal hernia (all of these are oesophageal lesions)
Name some neurological oropharyngeal causes of dysphagia
stroke, MS, myasthenia gravis, Parkinson’s disease
What nerve innervates the Masseter muscle and what is this muscle responsible for?
Trigeminal (5th cranial), mastication (chewing)
Which parasympathetic nerve controls salivary secretion and where does this nerve synapse?
Glossopharyngeal nerve (9th cranial), otic ganglion.
Where does the sympathetic nerve controlling salivary secretion synapse?
Superior cervical ganglion
Describe parasympathetic stimulation to salivary glands.
ACh release, acts on M3 receptor, Gq, PLC cleaves PIP2 to IP3 and DAG.
Secretion is watery.
Parasympathetic control responsible for volume (mainly).
Why does water not pass from the saliva into the duct cells during duct cell modification?
Duct cells relatively impermeable to water as tight junctions and lack of aquaporins, so hypotonic saliva produced.
Define a mesentery
a double layer of peritoneum that connects portions of the gut tube or other viscera to the body wall or to each other.
In the developing embryo, how does the mid gut communicate with the yolk sac?
Via the vitteline duct.
What is a Meckels diverticulum?
a vestigial remnant of the vitellointestinal duct (connecting gut tube to yolk sac), forming an outpouching. Rule of 2: 2 inches long, 2 ft from ilio-caecal junction, and 2 types of tissue: small bowel epithelium, and gastric tissue, occurs in 2% of pop.
How are the greater and lesser sacs, and greater and lesser omenta formed?
By rotation of the stomach
What does rotation of stomach achieve?
- vagus nerves put ant. and post. rather than left and right.
- cardia and pylorus shifted from midline, stomach lies obliquely
- contributes to lesser sac lying behing stomach
- forms greater omentum
Name 2 secondarily retroperiotneal organs
Most of duodenum, pancreas
Which part of the duodenum is intraperitoneal?
Duodenal cap
Name 3 retroperitoneal structures
Aorta, IVC, kidneys
How is a structure retroperitoneal?
It never had a mesentery, so never were within the periotneal cavity, and so lie against the post. abdominal wall, with periotneum covering its anterior surface only, and are not suspended in abdominal cavity.
How does duodenum become secondarily retroperitoneal?
Stomach rotation moves duodenum to the right, along with rapid growth of head of pancreas and rapid growth of liver. Duodenum then pressed against post. body wall, and dorsal mesoduodenum fuses with peritoneum.
Define mid-inguinal point and what is found there.
Midpoint between ASIS and pubic symphysis. Femoral artery can be palpated.
Define mid-point of inguinal ligament and what is found there.
Midpoint between ASIS and pubic tubercle. Femoral nerve found here. Deep inguinal ring found just above this point, though now been found to lie just medial to it, so closer to where femoral artery located, which is why may be said to lie at mid-inguinal point.
What is the deep inguinal ring?
Entrance to the inguinal canal.
Why might liver cirrhosis result in tortuous mucosal oesophageal veins?
Liver cirrhosis can cause portal hypertension, and oesophageal varices may result from this due to porto-systemic anastomosis. The L gastric vein drains blood from the oesophagus, and leads into the hepatic portal vein to the portal system, and the azygos vein, into the systemic system. With portal hypertension, blood normally passing through L gastric vein is redirected through oesophageal veins, into the azygos vein, causing dilation of veins in oesophageal mucosa.
What are diverticula and where do they develop?
Out-pouchings of a hollow or fluid filled structure in the body, related to pressure changes. Most common site= sigmoid colon, as has highest intra-luminal pressure.
Where is the dentate (pectinate) line?
Divides hind gut from procto-deum, dividing upper 2/3 of anal canal with columnar epithelium, from lower 1/3 with stratifies squamous epithelium. Blood supply and venous drainage also different between the 2, and pathology below line will be painful.
What are haemorrhoids?
vascular structures in anal canal which swell to stop faecal material from leaking out when it shouldn’t and so help with stool contro. Problems occur if distend beyond normal limits, and become pathological when symptoms produced e.g. bright red bloody stools, pain of defecation, itching and prolapse of haemorrhoidal tissue.
At what point is an incision made for an appendicectomy?
McBurney’s point- 2/3rds of distance between the umbilicus and the right ASIS. Incisions have to be able to close, and provide long-lasting strength, so minimise incidence of incisional hernias.
What is a hernia?
Protrusion of visceral contents through a cavity that normally contains it because of increased pressure or a weakened abdominal wall.
Where are the paired rectus abdominis muscles?
enclosed within rectus sheath- (fibrous CT, sheet of fascia), extends from thoracic cage to pubic bones. Tendinous intersections within muscles attach to deep surface of anterior side of the rectus sheath.
What is the linea alba?
fibrous line formed from midline fusion of aponeuroses of all 6 antero-lateral abdominal muscles.
What are the linea semilunares?
the sites of fusion of the aponeuroses of the 3 antero-lateral abdominal muscles per side at the lateral margin of the rectus sheath.
Describe the structure of the anterolateral abdominal wall, from superficial to deep.
- skin
- superficial fascia (fatty layer of subcutaneous tissue)
- deep, membranous layer of subcutaneous tissue
- deep fascia
- external oblique
- internal oblique
- transversus abdominis
- transversalis fascia
- extraperitoneal fat
- parietal peritoneum
Describe external oblique muscle
- Most superficial muscle of antero-lateral abdominal wall
- Muscle fibres run inferiorly and anteriorly from origin on thoracic cage (5th to 12th ribs)
- Inserts onto linea alba, pubic tubercle and anter. half of iliac crest.
- Lower, inferior margin of aponeurosis forms the inguinal ligament- extends from ASIS to pubic tubercle.
- thoracoabdominal nerves (T7-T11) and subcostal nerve.
How is the rectus sheath formed?
By decussation and interweaving of aponeuroses of flat abdominal muscles. External oblique aponeurosis contributes to ant. wall of sheath throughout its length. Internal oblique aponeurosis contribute to ant. and post. rectus sheaths. Aponeurosis of transversus abdominis forms post. layer of rectus sheath.
Describe internal oblique muscle
- muscle fibres run anteriorly and superiorly from origin on anter. 2/3 of iliac crest, thoracolumbar fascia and CT deep to lateral 1/3 of inguinal ligament.
- inserts into linea alba, 10th-12th ribs.
- Thoracoabdominal nerves (A.rami of T6-T12 spinal nerves) and 1st lumbar nerves.
What would happen if the muscle fibres of 1 abdominal wall muscle abutted the fibres of another.
The muscle fibres would tear themselves apart. Instead, each muscle is covered in epimysium.
Describe transversus abdominis muslce
- fibres run transversely/horizontally from internal surfaces of 7-12th costal cartilages, thoracolumbar fascia, iliac crest, and CT deep to lateral 1.3 of inguinal ligament.
- inserts into linea alba
- Same innervation as internal oblique.
What is the arcuate(Douglas’ line)?
Line marking the disapperance of the posterior rectus sheath below the umbilicus, resulting in inferior 1/4 of rectus abdominis muscle lying directly on transversalis fascia. Disappears about 1/3 of way between umbilicus and the pubic symphysis. So in pfannenstiel incision, there would be no post. sheath to look out for. Also, below this line, the rectus abdominis muscle lies directly on the transversalis fascia.
Where post. rectus sheath is absent., what does rectus abdominis lie on?
The transverslais fascia.
Describe rectus abdominis
-muscle fibres travel from pubic symphysis and pubic crest to the xiphoid process and the 5th-7th costal cartilages.
Describe inguinal canal structure
oblique passage directed inferomedially through inferior part of anterolateral abdominal wall. Lies parallel and superior to medial half of inguinal ligament. Spermatic cord occupies canal in males, round ligament of uterus in females. Also blood and lymphatic vessels, and the ilioinguinal nerve.
2 walls, roof and floor: Anter. wall- external oblique aponeurosis, lateral part reinforced by muscle fibres of internal oblique
Post.- transversalis fascia
Roof- laterally by transversalis fascia, centrally by musculoaponeurotic arches of internal oblique and transversus abdominis, and medially by medial crus of external oblique aponeurosis.
Floor- laterally by iliopubic tracr, centrally by gutter formed by infolded inguinal ligament, and medially by lacunar ligament.
Where does the greater omentum extend to?
From stomach to transverse colon.
What is the falciform ligament?
A peritoneal ligament, formed from the ventral mesogastrium, which connects the liver to the ventral body wall, as attached to visceral peritoneum of liver and parietal periotneum on deep surface of anterior body wall.
What connects the greater and lesser sacs?
The foramen of Winslow (epiploic foramen)
How are the greater and lesser curvatures of the stomach formed?
During longitudinal axis rotation, the posterior wall of the stomach grows more quickly and larger than the anterior part, forming the curvatures.
Why are inguinal hernias more common in males?
Due to passage of spermatic cord through inguinal canal.
Why are femoral hernias more common in females?
Due to wider pelves.
Why might strangulation of a femoral hernia occur?
As sharp, rigid boundaries of femoral ring, part. the concave margin of the lacunar ligament.
Describe differences between direct and indirect inguinal hernias.
Direct- herniation passing medial to inferior epigastric vessels, pushing through peritoneum and transversalis fascia in inguinal triangle to enter inguinal canal. Acquired hernia. Passes through Hesselbach’s triangle.
Indirect- herniation passing lateral to inferior epigastric vessels, to enter deep inguinal ring at the opening of the inguinal canal. Passes lateral to Hesselbach’s triangle. Congenital- failure of processus vaginalis to close properly. This is part of the peritoneum.
What are the borders of Hesselbach’s triangle and what is its clinical relevance?
Inferiorly- inguinal ligament
Laterally- inferior epigastric vessels
Medially- rectus abdominis muscle (lateral border of)
Before longitudinal axis rotation, the stomach comprises anterior and posterior sides, which after rotation faces right or left and is now the greater or lesser curvatures?
Anterior side now faces right, forming the lesser curvature.
Posterior side now faces left, forming the greater curvature.
What is the dentate/pectinate line?
Line demarcating the 2 different parts of the anal canal, the part above the anal canal has simple columanar epithelium and is derived from endoderm, the part below had stratified squamous epithelium, and is derived from ectoderm.
Give the name of the part of the lesser curvature which marks the start of the pyloric antrum.
Angular notch/ angular incisure
What is achalasia?
Problem with enteric NS resulting in failure of lower oesophageal sphincter to relax, and so stomach unable to accomodate food from oesophagus.
Cause of dysphagia.
What is the transverse mesocolon?
An expanse of peritoneum connecting the transverse colon to the posterior abdominal wall.
Where is the fundus of the stomach located?
Directly below the diaphragm
Where does the liver develop?
In the ventral mesetery
Where does the spleen develop?
In the dorsal mesentery (mesogastrium)
What is the hepatoduodenal ligament part of?
The lesser omentum
Where does the duodenum end?
At the duodenojejunal flexure, at L2 vertebral level
What is the axis of the primary intestinal loop?
The SMA
What are the derivatives of the cranial limb of the primary intestinal loop?
Distal duodenum, jejunum and proximal ileum
Where is visceral pain felt if foregut derived?
Epigastric region
Where is visceral pain felt if midgut derived?
Peri umbilical
Where is visceral pain felt if hindgut derived?
Supra public region
What level is the celiac trunk at?
T12
What ligaments does the greater omentum form?
Gastrocolic ligament
Gastrosplenic ligament
Gastrophrenic ligament
Where does a direct inguinal hernia push through in Hesselbach’s trinagle most commonly, and why?
The superficial inguinal ring as further area of weakness
Describe difference between an incarcerated and a strangulated hernia?
Incarcerated- stuck, cannot go back to where it came from, but blood supply intact, though can become strangulated.
Strangulated- blood supply compromised.
What is the saphenous opening?
An opening in the deep fascia (fascia lata) of the thigh, which allows the ascent of the great saphenous vein, which once through opening joins the femoral vein.
What is the dermatomal level of the umbilicus?
T10
Where does the celiac trunk originate from?
The abdominal aorta, immediately after thoracic aorta descends behind the diaphragm to enter the abdomen. Diaphragm- aortic hiatus- level of T12.
Where does the left gastric artery run and what branch does it give off? Also, what artery does it anastomose with?
To the left side of the lesser curvature of the stomach.
Oesophageal branch
R gastric artery
What is the left gastric vein a tributary of?
The portal hepatic vein
Where does the splenic artery run?
Retroperitoneally along superior border of pancreas to spleen from celiac trunk.
What anastomoses form along the greater curvature of the stomach?
Right and left gastro-epiploic arteries.
Which arteries supply upper body and fundus of stomach?
Short and posterior gastric arteries
What is the hepatic portal vein formed from?
The splenic vein and SMV
Which arteries does the splenic artery give rise to?
Left gastroepiploic, the short gastric and the posterior gastric arteries.
What is a peritoneal ligament?
A double layer of peritoneum that connects an organ with another organ or to the abdominal wall.
How is the liver connected to other organs and the abdominal wall by peritoneal ligaments?
-falciform ligament- to anterior body wall
-hepatogastric ligament- to stomach
-hepatoduodenal ligament- to duodenum. This ligament is the thickened free edge of the ventral mesentery, which conducts the portal triad.
All part of lesser omentum.
How is the stomach connected to other organs and the abdominal wall by peritoneal ligaments?
- gastrophrenic ligament-to diaphragm
-gastrosplenic ligament-to spleen
-gastrocolic ligament- to the transverse colon.
All have a continuous attachment along greater curvature, and are all part of greater omentum.
Clinical significance of gastroduodenal artery
Duodenal ulcers may erode posteriorly into the gastroduodenal artery, causing extensive bleeding
What is the dermatomal level of the pubis
T12
Treatment for H.pylori infection
2 antibiotics and a proton pump inhibitor- combination of clarithromycin with either amoxicillin or metronidazole, +PPI e.g. lansoprazole.
How does H.pylori survive in acid environ. of stomach?
It produces urease- converts urea to ammonia- this buffers gastric acid with concurrent production of CO2. Bacterium has urea channels which open at pH less than 6.5, so urea delivered to enzyme.
Basis for urease breath test for bacterium detection.
H pylori can then live within the mucous gel of the barrier, its motility-flagellum and chemotaxis, allowing it to penetrate close to epithelium.
Also, it produces adhesins so can attach to mucosa.
What is GORD?
A digestive disorder where there is regurgitation of stomach contents into lower oesophagus through an effective lower oesophageal sphincter, and the associated symptoms and pathology that this produces.
What structures does celiac trunk supply?
Foregut derived:
so oesophagus, liver/biliary apparatus, spleen, stomach, proximal duodenum and pancreas
At what vertebral level does the caval opening, oesophageal opening and aortic hiatus in diaphragm occur?
Vena cava- T8
Oesophagus- T10
Aortic hiatus- T12
At what vertebral level is the cardial orifice?
T11
What is dyspepsia?
A variety of symptoms including upper abdominal pain, acid reflux, heartburn and nausea/vomiting.
Describe H.pylori
A gram -ve bacterium which is helical in shape and highly motile. Major cause of peptic ulcers. Urease producing and ability to penetrate gastric mucosa enables its survival in acidic stomach environment.
Importance of alkaline tide
HCO3- readily available in blood to be subsequently re-secreted into GI tract by pancreas and liver to neutralise acid as it leaves the stomach
How can we detect H.pylori in a patient?
Urease breath test- give patient radioactively labelled urea, and then see if 20 mins later, radioactively labelled CO2 is produced as this would mean urease has acted upon the urea given, and urease is produced by H.pylori
Why is a PPI more effective than a H2 antagonist at reducing stomach acid production?
Stomach acid produced by parietal cells which have receptors for gastrin, Ach, and histamine which all stimulate acid production via the proton pump. A histamine antagonist will only block the input of histamine to acid production, with receptors for gastrin and Ach still being able to stimulate acid prod., whereas a PPI will block all receptor inputs to acid prod. as it blocks the proton pump necessary for any acid production from the parietal cell.
Why might NSAIDs lead to peptic ulcer formation?
COX1 inhibitors, COX1 being the enzyme responsible for prostaglandin synthesis from arachidonic acid- an eicosanoid, and prostaglandin E increases mucus and alkali prodcution, mucus being produced by neck cells at surface of mucosa, which protects the stomach mucosa from gastric acid, and also increases mucosal blood flow, which again is protective, so inhibition of PG production inhibits these protective mechanisms against harsh acidic environment.
Give 3 causes of oesophageal atresia
- tracheo-oesophageal septum misplacement
- rencanalisation failure
- ischaemia
What is polyhydamnios and why might it occur with oesophagel atresia?
accumulation of amniotic fluid
Atresia results in upper GI obstruction that will prevent normal amniotic fluid swallowing by the fetus
What is the common bile duct formed from?
The cystic duct from the gallbladder and the common hepatic duct from the R and L hepatic ducts from the liver
What prevents reflux of duodenal contents into ampulla of Vater (hepatopancreatic ampulla)?
Sphincter of Oddi
Give 2 functions of mesenteries
- Attach organs to body wall
- Provide a conduit for nerves and blood vessels
During physiological herniation, if the midgut rotates once clockwise, what would happen?
The cranial limb would still enter abdominal cavity 1st and so reside to the left, but would now be anterior rather than posterior to the caudal limb.
What is omphalocele?
Incomplete physiological herniation where primary intestinal loop resides outside of body, with a covering of amnion. Contrast with covering of subcutaneous tissue in an umbilical hernia.
List functions of saliva
- start digestion with secretion of salivary amylase
- protection of oral mucosal environment via bacteriostatic actions, and alkaline secretion- Ca2+ unable to dissolve, protects the teeth.
- Lubrication of food bolus for swallowing and passage down the oesophagus.
What are the 3 phases of swallowing?
Voluntary, pharyngeal and oesophageal
List the key functions of the digestive tract
DAMES
Digestion, absorption, motility, excretion and secretion
How might xerostomia result?
- salivary gland tumour
- calculus blocking saliva outflow from salivary gland
- side effect of anti-muscarinics, inhibit parasympathetic innervation controlling saliva secretion
What might be the causes for a difficulty in swallowing food, and a difficulty in swallowing liquids.
food- mechanical causes of dysphagia e.g. large oesophageal tumour
liquids- problem with neural control e.g. stroke.
How might haematemesis result?
peptic ulcer, gastric cancer, oesophageal varices
Describe chyme
acidic
hypertonic
partially digested
What controls pancreatic enzyme secretion?
CCK
What controls pancreatic alkaline secretion?
Secretin
When in bile released from gallbladder?
When CCK secreted by duodenum during gastric emptying. Stimulates smooth muscle of gallbladder to contract and release bile. CCK also relaxes sphincter of Oddi so bile can pass into duodenum. Vagal stimulation can also cause weak gallbladder contraction.
During what phase of are most pancreatic secretions released?
Intestinal phase
What is cholecystitis?
gallbladder inflammation as result of gallstone impaction in neck of gallbladder, (or cystic duct?) which may cause continuous epigastric pain, vomiting and fever. If stone moves to common bile duct, obstructive jaundice and cholangitis may occur- infection of common bile duct.
What is biliary colic?
Symptomatic gallstones with cystic duct obstruction or bypassing into common bile duct.
How might pancreatitis be caused by gallstones?
Galllstone obstruction of outflow of pancreatic duct, if travel down common bile duct, blocking enzyme release.
Why is liver larger in mature fetus?
Serves as a haematopoietic organ
What is the only nutrient absorbed not to be initially conveyed to liver by portal venous system?
Fat- absorbed into lymphatic system which bypasses liver.
Where does liver lie anatomically?
R hypochondrium, where protected by thoracic cage and diaphragm, deep to ribs 7-11 on R side and crosses midline toward left nipple, so also occupies upper epigastrium and extends into left hypochondrium
Where are the sub-phrenic recesses?
These are sup. extensions of greater sac existing between diaphragm and ant. and sup. aspects of diaphragmatic surface of liver. Separated into R and L by falciform ligament.
What is the subhepatic space?
portion of supracolic compartment of peritoneal cavity, immediately inferior to liver
Describe the heptaorenal recess (hepatorenal pouch/Morison pouch)
posterosuperior expansion of subhepatic space, lying between R part of visceral surface of liver and R kidney and suprarenal gland. In supine position, fluid drains from lesser sac into this recess. Communicates anter. with R subphrenic recess.
Why is liver susceptible to scarring from cellular damage?
As primary site for detoxification of substances absorbed by digestive system. Hepatocytes=stable cells- good regenerative capacity, in G0 of cell cycle so can reenter when needed if receive growth stimulus, this requires activation of proto-oncogenes.
Fibrous tissue surrounds intra-hepatic blood vessels and biliary ducts, making liver firm, and impeding circulation of blood through it when liver cirrhosis.
Describe the bare area of liver
Posterior part of diaphragmatic surface not covered with visceral peritoneum and so in direct contact with diaphragm. Demarcated by reflection of peritoneum from diaphragm to it as anterior and posterior layers of the coronary ligament. These layers meet on R to form R triangular ligament.
Describe triangular ligaments of liver
Result from convergence of anterior and posterior parts of coronary ligament from reflection of peritoneum from diaphragm. A and P layers meet on R to form R triangular ligament. A layer continuous on L with R layer of falciform ligament, and P layer continuous with R layer of lesser omentum. L triangular ligament formed near apex where A and P layers of L part of coronary ligament meet.
Describe relationship of IVC to liver
IVC traverses a deep groove for the vena cava within bare area of liver
What is the fibrous remnant of the ductus venosus
ligamentum venosum
DV was a fetal shunt where blood from umbilical vein bypassed liver to enter IVC as liver not needed to detoxify blood as carried from mother’s placenta.
What is the fibrous remnant of the umbilical vein?
Round ligament/ ligamentum teres hepatis
Where does hepatoduodenal ligament (thickened free edge of lesser omentum) extend from?
from porta hepatis to duodenum, and encloses structures passing through porta hepatis
Where does hepatogastric ligament extend?
from groove for ligamentum venosum to lesser curvature of stomach
Impressions on visceral surface of liver reflect liver’s relationship to which structures?
- stomach- R side of ant. part so pyloric and gastric areas
- duodenum- S.part (duodenal area)
- lesser omentum, which extends into groove for ligamentum venosum
- gallbladder-fossa
- colon-(colic area)- R colic flexure and R transverse colon
- R kidney and suprarenal gland (renal and suprarenal areas).
How is liver divided into 2 anatomical lobes and 2 accessory lobes?
By reflections of periotneum from its surface, fissures formed in relation to those reflections and the vessels serving liver and gallbladder.
How is essentially midline plane separating R and L lobes of liver defined?
By attachment of falciform ligament and left sagittal fissure.
Where are the 2 accessory lobes of liver located?
These are parts of anatomic R lobe and lie on slanted visceral surface, with R and L sagittal fissures on each side, and are separated from each other by porta hepatis.
Why can hepatic lobectomies where R or L part of liver removed, occur without excessive bleeding?
Because liver divisions, as R and L hepatic arteries and ducts, + branches of R and L hepatic portal veins, do not communicate. Most liver injuries involve R part. Can now perform hepatic segmentectomies so remove only those segments with severe injury or affected by tumor. R, intermediate, and L hepatic veins serve as guides to planes between hepatic divisions but also provide major source of bleeding. each hepatic resection requires ultrasonography to establish patient’s segmental pattern as differ in size and shape as result of variation in branching of hepatic and portal vessels.
Where is portal vein formed?
Anterior to IVC and posterior to neck of pancreas, close to L1 vertebra and transpyloric plane
Where do hepatic veins open into IVC?
Just inferior to diaphragm
What are kupffer cells?
specialised macrophages of liver found along sinusoids, and perform phagocytosis
What are the main tributaries of hepatic portal vein?
SMV, splenic vein, gastric veins, cystic veins and IMV- drains into HPV directly in 1/3 of people, but in most enters splenic vein, or SMV.
Where is the gallbladder?
Lies in fossa for gallbladder on visceral surface of liver. Fossa at junction of R and L parts of liver
Describe relationship of gallbladder to duodenum
Gallbladder lies anterior to superior part of duodenum, and its neck and cystic duct are immediately superior to duodenum
How does hepatic surface of gallbladder attach to liver?
Via CT of fibrous capsule of liver
Describe the 3 parts of the gallbladder
Fundus: wide blunt end that usually projects from Inf. liver border at tip of R 9th costal cartilage in MCL
Body: main portion contacting visceral liver surface, transverse colon and superior part of duodenum
Neck: narrow, tapering end, opp. fundus, and directed toward porta hepatis, typically makes an S-shaped bend and joins cystic duct runnning from gallbladder to meet common hepatic duct from liver, to form common bile duct.
Peritoneum completely surrounds fundus and binds its body and neck to liver.
How is cystic duct helped to be kept open?
By spiral fold formed by spiralling of mucosa of neck of gallbladder. This means bile can be easily re-directed into gallbladder when distal end of bile duct closer by sphincter of bile duct and/or hepatopancreatic spincter, or bile can pass into duodenum as gallbladder contracts- stimulated by CCK released on gastric emptying, by I cells.
Spiral fold also offers additional resistance to sudden damping of bile when sphincters closed, and intra-abdominal pressure suddenly increased, e.g. in cough.
Describe cystic duct course
Passes between layers of lesser omentum, usually parallel to common hepatic duct, which it then joins.
Describe arterial supply of cystic duct and gallbladder
Cystic artery, commonly from R hepatic artery from hepatic artery proper, in triangle between common hepatic duct, cystic duct, and visceral liver surface= cystohepatic triangle.
Describe venous drainage of gallbaldder and cystic duct
Cystic veins-enter liver directly or drain through hepatic portal vein, after joining veins draining hepatic ducts and proximal bile duct. Veins from fundus and body enter visceral liver surface directy and drain into hepatic sinusoids= drainage from 1 capillary bed to another, so additional portal sytem.
Lynphatic drainage of gallbladder
Hepatic lymph nodes, often through cystic lymph nodes near neck of gallbladder. Efferent lymphatic vessels from nodes pass to celiac LNs.
Nerves to GB and CD?
From celiac plexus, vagus nerve and R phrenic nerve.
Describe relations of spleen
Anteriorly: stomach
Posteriorly: L part of diaphragm, separating it from pleura, lung and ribs 9-11
Inferiorly: L colic flexure
Medially: L kidney
Arterial supply of spleen
Splenic artery from celiac trunk. Follows tortuous course along superior border of pancreas, posterior to lesser sac and anterior to L kidney. Divides into 5 or more branches between layers of splenorenal ligament. Lack of anastomosis between branches within spleen so vascular segments of spleen formed- 2 in most, 3 in others, with relatively avascular segments between, so allows subtotal splenectomy.
Venous drainage of spleen
Splenic vein- formed by several tributaties emerging at hilum.
What toxins must GI tract cope with?
bacteria viruses chemical protozoa nematodes/roundworms cestodes/tapeworms trematodes/flukes
What innate physical defences protect GI tract from toxins?
- saliva
- colonic mucus
- sight
- smell
- memory
- gastric acid
- small intestinal secretions
- anaerobic environ. in small bowel and colon
- peristalsis
Give 3 viruses resistant to stomach acid
hepatitis A- RNA non-enveloped
polio-picornavirus, RNA non-enveloped
coxsackie
Where is gut associated lymphoid tissue (GALT) found in concentrated nodules?
- tonsils
- peyer’s patches-in ileum
- appendix
A 50 yr old man with liver cirrhosis presents with hand problems- 4th and 5th digits pulled into partial flexion at MP and proximal IP joints, what is this presentation called?
Dupuytren’s contracture- disease of palmar fascia resulting in progressive shortening, thickening and fibrosis of palmar fascia and aponeurosis. Fibrous degeneration of longitudinal bands of palmar aponeurosis on medial side of hand pulls 4th and 5th digits into partial flexion at MP and proximal IP joints
What is mesenteric adenitis?
Enlargement of mesenteric lymph nodes as become inflamed, common cause of RIF pain in children
What investigations may be done in appendicits?
CRP
FBC, look at neutrophils
Describe a femoral hernia
bowel enters femoral canal, presenting as a mass in upper medial thigh or above inguinal ligament, where it points down the leg, unlike an inguinal which point to groin. Neck of hernia felt inferior and lateral to pubic tubercle.
Describe epigastric hernias
pass through linea alba above umbilicus
Describe true umbilical hernias
result of perisitent defect in transversalis fascia- umbilical ring, through which umbilical vessels passed to reach the foetus. Can recur in adulthoood e.g. in pregnancy, or gross ascites.
Paraumbilical occur just above of below umbilicus and are found in a canal bordered by umbilical fascia posteriorly, linea alba anteriorly and rectus sheath laterally.
Why is surgical repair less urgent in omphalocoele than in gastroschisis?
Bowel protrusion protected by membranes e.g. amnion
Give 3 causes of appendicits
Faecoliths
Worms
Lymphoid hyerplasia
Why does alcoholic liver injury produce a ‘fatty’ liver?
Cellular energy diverted away from fat metabolism to alcohol metabolism, so fat accumulates as globules within liver cells.
Toxic acetaldehyde damages liver cells so unable to produce lipoproteins necessary to transport TAGs away from liver
What is liver cirrhosis?
Hepatic fibrosis with nodular regenration producing a shrunken liver. Results from recurrent loss of liver cells or severe tissue architectural damage. Irreversible. Liver cells no loner arranged in acini or lobules, but as nodules. Blood perfuses nodules in haphazard fashion as well-organised zonal structure lost, so organ prone to failure.
Why can excess ammonia cause mental confusion?
NH3 reacts with and removes alpha ketoglutarate from TCA cycle, so diminished energy supply to brain cells. Also increases pH of cells of CNS, interfering with neurotransmitter synthesis and release.
Where in body can ruptured varices as result of porto-systemic anastomosis occur?
- oesophagus
- ano-rectal junction
- umbilical vein in falciform ligment
How does paracetemol overdose lead to liver failure?
Phase II conjugation pathways become saturated so paracetemol undergoes phase I metabolism, producing the metabolite NAPQI which is toxic to hepatocytes. Can give N-acetyl cysteine.
Then undergoes phase II with glutathione, depleting cell of important anti-oxidant for protection against ROS.
Why can alcohol lead to acute pancreatitis?
Results in hyper-stimulation of pancreatic secretions so enzymes produced by acinar cells activated prematurely in pancreatic ducts.
Enzyme responsible for bilirubin conjugation?
UDP-glucoronyl transferase
Liver cirrhosis can result in oesophageal varices, which may present with very significant blood loss with vomiting of blood, why is so much blood lost?
Varices rupture and deficient clotting ability due to liver cirrhosis, so increased PTT, and LOTS of bleeding!
Give 4 key functions of the liver (blood and gut related)
Energy metabolism
detoxification
production of plasma proteins e.g. albumin
Bile production and secretion
What does bile comprise?
Bile acids (salts) Bile pigments Cholesterol Phosopholipids electrolytes water
What 2 important functions of bile acids can be carried out due to amphipathic nature of molecules?
- emulsification of lipid aggregates
- transport and solubilization of lipids in an aq environment
What part of duodenum most prone to peptic ulcers and why?
First part=duodenal cap, as this is the first place that chyme enters once it leaves the stomach and at this point, alkaline secretions have not yet been able to act on the chyme to neutralise it.
Gallbladder functions?
Store, concentrate, and release bile when needed i.e. when chyme enters duodenum
How is liver helped to be suspended in abdominal cavity?
Hepatic veins
R and L triangular, and coronary ligaments
Tone of anterior abdominal wall muscles
Xerstomia may result in parotitis, what bacterial organism causes this infection?
Staphylococcus aureus
Give an example of a H2 antagonist used to reduce gastric acid production
Cimetidine
Which cells of stomach produce histamine?
Enterochromaffin-like cells
Which clotting factors depend on Vit.K for their synthesis?
II(pro-thrombin), VII, IX and X (2,7,9 and 10)
Which organ is the only one that can, in effect, release glucose into the bloodstream to maintain blood sugar levels, and why?
Liver
Contains enzyme glucose 6-phophatase
Where is intrinsic factor produced?
Parietal cells of stomach
Where is most Vit B12 absorbed?
Terminal ileum
Why might someone with Crohn’s disease experience pernicious anaemia?
Chronic inflammation of terminal ileum reduces ability to absorb vitamin B12 necessary for erythropoiesis
If parietal cell destruction, why might patient have pernicious anaemia?
As intrinsic factor not produced as normally produced by parietal cells, and this factor is necessary for VitB12 absorption from the terminal ileum, in order to have erythropoiesis
Which part of GI tract does Crohn’s disease normally affect?
Terminal ileum or proximal colon, but can occur anywhere from mouth to anus
Which part of GI tract does ulcerative colitis normally affect?
Rectum and sigmoid colon
Differences between Crohn’s and ulcerative colitis
Crohn’s: transmural, skip lesions as patch mucosal involvement, granulomas
Ulcerative colitis: Only mucosa affected, inflammation continuous in distribution, increases risk of colon cancer
Describe the distribution of the SMA
Supplies duodenum distal to entry on common bile duct, jejunum, ileum, ascending colon and proximal 2/3 of transverse colon
Where does the ileocolic artery run?
From SMA to caecum
Where do R colic and middle colic arteries run?
From SMA to ascending colon (R colic) and transverse colon (middle colic)
R colic commonly originates from ileocolic artery but may arise as a direct branch of the SMA
At what level is the IMA?
L3
Describe path of L colic artery?
Originates from IMA and supplies ascending colon and distal part of transverse colon
How is arcade of arteries formed in transverse mesocolon?
Anastomosis of L colic artery and middle colic artery
What artery supplies proximal part of rectum ?
Superior rectal artery from IMA
How is blood supplied to sigmoid colon?
Sigmoid branches of IMA
What are the main functions of bile acids?
Emulsification of lipids so large SA prod. for digestion
Lipid transport- micelles
Induction of bile flow
Regulation of bile acid synthesis- normal reabsorption inhibits hepatic synthesis
Water and electrolyte secretion- if bile acids present in colon, can result in diarrhoea
What regualtes platelet prod. by BM?
Thrombopoietin- a glycoprotein hormone
When might alkaline phosphatase levels be elevated?
Cholestasis- obstruction of bile ducts so enzyme released from liver into blood.
Paget’s disease- active bone formation, enzyme released as by-product of osteoblast activity.
Vertebral level of SMA?
L1, originates from anterior surface of abdominal aorta
What are vasa recta?
Straight arteries, * seen in juxtamedullary nephrons of kidney, run from arcade of arteries see in mesentery of small intestine
What does the ileocolic artery bifurcate into close to ileocaecal junction?
Ileal and cecal branches
What does descending branch of R colic artery anastomose with?
Cecal branch of ileocolic artery
Where does middle colic artery arise from and ascend to?
Proximal part of SMA
Ascends into transverse mesocolon where it gives off R and L branches
Major blood supply of transverse colon?
Middle colic artery from SMA
Anastomosis of ascending branch of R colic artery?
With R branch of middle colic artery
Anastomosis of L branch of middle colic artery?
with ascending branch of L colic artery from IMA-L3
Describe the marginal artery
A summation of the anastomoses of adjacent colic branches of SMA and IMA. Lies along inner perimeter of colon, extending from cecum to the sigmoid colon
Describe relationship of SMA to pancreas
Originates posterior to neck of pancreas, then descends and passes anterior to uncinate process of pancreas
Where does the inferior pancreaticodudenal artery originate and what does it supply?
SMA, supplies head of pancreas and duodenum
In addition to its bacteriostatic and immune actions, how else does saliva defend GI tract against toxins?
It washes bacteria and toxins into stomach where acidic environment plays an important defensive role
What is the 1st line of defence of the colon against its contents?
Colonic mucus layer
Colonic microflora drive maturation of colonic mucosa and mucus prod. Mucus barrier can act as an energy source or support medium for growth to intestinal microflora.
Barrier effectively separates microbes from epithelium of colonic wall
Where are the main locations of portosystemic anastomoses?
- Between the oesophageal tributaries of the left gastric vein and the veins draining the rest of the oesophagus- SM oesophageal veins, draining into the azygos system.
- Between the superior rectal veins from the SMV and the middle & inferior rectal veins
draining into the internal iliac vein. - Between the portal tributaries of retro-peritoneal organs (such as ascending and descending colon, kidney, etc.) and the lumbar veins draining eventually into the inferior vena cava.
- Between the veins in and around the falciform ligament-hepatic portal veins, and the veins of the anterior abdominal wall- anterior abdominal veins, draining into the epigastric veins.
- Between the veins of the posterior abdominal wall and bare area of the liver
draining into the inferior vena cava.
Which aminotransferase is specific to the liver?
ALT
Treatment options for viral hepatitis?
Alpha interferon- inhibits viral replication
Antivirals to reduce viral load, e.g. ribavirin and lamivudine.
Why might post-hepatic jaundice be associated with slow blood clotting?
Obstruction in biliary tree means bile salts don’t enter the bowel where required for absorpion of fats, so fats, and subsequently fat soluble vits not abdorbed. Vit K=fat soluble, so Vit K deficiency, and Vit K essential for synthesis of clotting factors II, VII, IX and X.
Describe symptoms of hepatic encephalopathy that may occur in liver failure, and can be potentiated by hypokalemia
Disturbances in consciousness- confusion to coma or death
Asterixis- flapping tremor of outstretched hands
Fluctuating neurological signs- muscualar rigidity and hyperreflexia
Intellectual deterioration- constructional apraxia and slow, slurred speech
Treatment of hepatic encephalopathy?
Reduce protein intake to reduce uraemia and endogenous protein b.down, treat any infection, empty bowel of N-containing material and correct metabolic and coagulation disturbances.
Flumazenil- benzodiazepine receptor antagonsit, can improve condition in ST.
What is hepatic encephalopathy precipitated by?
Sepsis/infection Diuretics e.g. loops and thiazides GI bleeding Alcohol withdrawal Constipation
Features of fulminant hepatic failure
Jaundice Encephalopathy Reduced level of consciousness Hypoglycaemia-renal failure Decrease K+/Ca2+ Haemorrhage
Which metastasis makes up 50% of secondary liver metastases?
Colorectal
What are majority of liver metastases due to?
Portal venous drainage
What does upper 2/3 of stomach secrete?
Pepsin and HCL
What does lower 1/3 of stomach secrete?
Mucus and gastrin
Relations of the inguinal canal?
Anteriorly: external oblique aponeurosis and internal oblique muscle fibres reinforce lateral 1/3
Posteriorly: transversalis fascia laterally, conjoint tendon medially
Roof: fibres of transversalis fascia laterally, internal oblique and transversus abdominis centrally, medially by medial crus of external oblique aponeurosis
Floor: laterally by iliopubic tract, inguinal ligament infolded to form a gutter centrally and lacunar ligament medially
Where is C reactive protein produced?
Liver- hepatocytes produce this inflammatory marker in response to factors secreted by macrophages
L gastric vein blood diverted to oesophageal mucosal veins when portal hypertension. Where does blood in this vein normally come from and how does it drain into the liver?
L gastric vein drains blood from oesophagus via and oesophageal vein: along with the R gastic vein, they enter the portal vein, which takes blood the the liver for detoxification before it enters the systemic circulation
Where is the portal vein formed?
Posterior to neck of pancreas
What name is given to the smooth surface of the liver?
Diaphragmatic surface, separated from visceral surface by sharp inferior border
How are the L and R functional parts of the liver demarcated?
By a line extending along the fossa for the IVC and the gallbladder on the visceral surface
How are shallow depressions created on visceral liver surface?
By organs related to the liver e.g. stomach, oesophagus, R kidney and adrenal gland, duodenum and colon
What name is given to the procedure of endoscopy used to look at the upper GI tract?
Oesophagogastricduodenoscopy
Name the 2 flexures of the colon, located between the ascending and transverse parts, and the transverse and descending parts
Hepatic and splenic flexures
What are intestinal crypts?
Glands lining intestinal epithelia, situated at base of villi. Secrete various enzymes and site of enterocyte multiplication. Enterocytes then migrate along villi, maturing as they go and gaining the capacity to absorb. They are then shed from the tips of the villi, so mucosa is continually renewed by the process of enterocyte multiplication in the crypts and subsequent ascent of the villi.
What is the ‘unstirred layer’?
A layer of mucus and water adjacent to the intestinal wall. Here, enzymes secreted by the enterocytes are trapped and can act on nutrients in the small intestinal lumen as their diffusion is slowed, and so they can be further broken down, completing digestion.
Hoe are the alpha 1,6 glycosidic linkages in amylopectin broken down?
By isomaltase present in the unstirred layer
Why do oral rehydration therapies contain glucose and salt?
In diseased states if you just put water into the gut, it would simply pass through without being absorbed as an osmotic gradient generated by altering osmolarity is necessary as we can’t actively move H20.
If you put water and salt into a solution and ingested this, there would be very limited absorption of Na into the enterocyte and hence very little movement of water across the cell membrane of the enterocyte.
If you add glucose to the solution, even in a disase state, the gut will absorb this.
Net movement of both Glucose and Na into the enterocyte as use of SGLUT1 cotransporter. The movement of Na sets up the movement of water and so water moves into the enterocyte.
So will be greater absorption of water.
Describe how chymotrypsinogen released by pancreatic acinar cells is activated to produce chymotrypsin
Trypsinogen released from pancreatic acinar cells is converted to its active form trypsin by enterokinase. Trypsin then activates chymotrypsinogen
What is ‘mass movement’
Peristaltic movements once or twice a day in transverse and descending colon which rapidly move faeces into the rectum. Resulting stretch of rectum causes urge to defecate.
What is the gastrocolic reflex?
Urge to defecate produced on stomach distension after eating a meal, as stretching of stomach initiates peristalsis, which involves mass movement, so rapid faeces movement into rectum, stimulating defecation urge.
What is classical pernicious anaemia?
Vitamin B12 deficiency resulting specifically from a lack of intrinsic factor production by parietal cells of stomach, hence inability to absorb Vit B12 from terminal ileum. Vit B12 necessary for erythropoiesis and so in its absence, erythropoiesis is ineffective as dysfunctional thymidine synthase, causing a megaloblastic anameia.
Cause of pernicious anaemia?
AI atrophic gastritis, causing destruction of parietal cells, hence reduction in intrinsic factor prod.
What term is given when ulcerative colitis affects the terminal ileum due to a defective ileo-caecal valve?
Backwash ileitis
Potential cure for ulcerative colitis?
Total colectomy
Would result in a stoma (Terminal ileum brought to the surface of abdominal wall, on the right side). Options include an ileoanal or ileorectal anastomosis with an Ileal reservoir. This avoids the need for a permanent stoma.
Other than an oesophageal cancer, what causes of dysphagia make swallowing solids harder than swallowing liquids?
External compression of oesophagus e.g. hiatal hernia, aortic aneurysm
Fibrous stricture
Anything causing a physical obstruction
