bleeding in the GI tract Flashcards
large intestine from proximal to distal is made up of…
colon: caesum, appendix, ascending colon, transverse colon, desending colon, sigmoid colon
rectum
anal canal
anus
functions of the small intestine
defence - commensal bacteria
absorption - H2O & electrolytes
excretion - of formed stool
where are the paracolic gutters found
between lateral edge of ascending colon and descending colon and abdominal wall
what can happen in the paracolic gutters and what is it part of
part of peritoneal cavity
potential site for pus collection
where do the caecum and appendix lie
both lie in the right illiac fossa
where does the appendiceal orifice lie
posteromedical wall of caecum
corresponds to McBurney’s point on the abdominal wall
1/3 of the way between right ASIS to umbilicus
maximum tenderness in case of appendicitis
where does the sigmoid colon lie
lies in the left illiac fossa
advantages and disadvantages of sigmoid mesocolon
gives considerable degree of movement
neg: sigmoid colon at risk of twisting around itself (sigmoid volvulus)
clinical results in bowel obstruction
bowel at risk of infarction if left untreated
where does the abdominal aorta lie
midline retroperitoneal structure
3 midline peritoneal branches of abdominal aorta
celiac trunk (foregut organs)
superior mesenteric artery - midgut organs
inferior mesenteric artery - hindgut organs
3 lateral branches of abdominal aorta supply what
kidneys/adrenal glands
gonads (testes/ovaries)
body wall (posterolateral)
what does the abdominal aorta bifurcate into and at what level
common iliacs
L4
further bifurcates into internal and external iliacs
branches of the superior mesenteric artery
inferior pancreaticoduodenal
middle colic artery
right colic artery
ileocolic branches
appendicular
jejunal and ileal arteries
jejunal vs ileal arteries
Jejunum
Longer vasa rectae
Larger and fewer arcades
Ileum
Shorter vasa rectae
Smaller and many arcades
branches of the inferior mesenteric artery
left colic artery
sigmoid arteries (multiple)
superior rectal artery
marginal artery of drummond
There exists arterial anastomoses between the branches of the SMA and the IMA
Depending on the health of these anastomotic vessels, and the speed at which obstruction of a vessel occurs, these anastomoses could help prevent intestinal ischaemia
- by providing an alternative (collateral) route by which blood can travel
blood supply to rectum and anal canal
superior rectal artery - a branch of IMA
- hindgut extends to proximal half of the anal canal
remainder of GI tract is supplied by the internal iliac artery
- there is an anastomoes between these vessels
main venous systems of the GI tract
hepatic portal venous system
- Drains venous blood from absorptive parts of the GI tract & associated organs to the liver for ‘cleaning’
systemic venous system
- Drains venous blood from all other organs and tissues into the superior or inferior vena cava
main the main veins of the GI tract
inferior vena cava hepatic portal vein splenic vein superior mesenteric vein inferior mesenteric vein
3 clinically important sites of venous anastomosis - what is the suggnificance of these veins
the presence of small collateral veins means blood can flow both ways:
Either into the systemic or portal venous system
There are no valves in these veins
Normally there is very little blood flow within these collateral veins
3 clinically important sites for portal- systemic anastomoses
skin around ambilicus
distal end of oesophagus
rectum/anal canal
venous drainage of the rectum and anal canal
superoir rectal veil –> inferior mesenteric vein
middle rectal vein –> internal iliac vein
inferior rectal vein –> internal iliac vein
what is portal hypertension and what is it caused by + leads to
Elevation of blood pressure in the portal system
Can be caused by;
Liver pathology (cirrhosis)
Tumour compressing HPV
Leads to reversal of blood flow
Larger volume of blood flow to these anastomotic (collateral) areas causes them to become varicosed
clinical presentation of portal hypertension
Oesophageal varices
Caput medusae
Rectal varices
causes of haematemesis
peptic ulcer in wall of stomach or duodenum
erodes through the mucosa
stomach or duodenum fills with blood
Bleeding from oesophageal varices
Abnormal dilated veins
Thin walled, therefore have potential to rupture
Filling oesophagus with blood
Formation often due to pathology affecting the portal venous system
