1- bleeding in GI tract + anatomy of blood vessels in anatomy Flashcards
what organs are part of the foregut?
oesophagus to mid-duodenum, liver, gallbladder, spleen and 1/2 pancreas
what organs are part of midgut?
mid duodenum to proximal 2/3 of transverse, 1/2 of pancreas
what organs are part of hindgut?
distal 1/3 of transverse colon to 1/2 of anal canal
what do all organs in each region (foregut, midgut and hindgut) have in common?
organs in each region share the same arterial supply, venous drainage, lymphatic drainage
what is the main supply to abdominal region?
abdominal aorta - they’re branches give off to regions
what are 3 main midline branches?
- coeliac trunk
- superior mesenteric artery
- inferior mesenteric artery
*the mesenteric arteries pass through mesentery
what branch of abdominal aorta supplies foregut organs?
coeliac trunk
what branch of abdominal aorta supplies midgut organs?
superior mesenteric artery
what branch of abdominal aorta supplies hindgut organs?
inferior mesenteric artery
what do lateral branches of abdominal aorta supply?
- kidneys/adrenal glands
- Gonads (ovaries / testes)
- body wall (posterolateral)
where does coeliac trunk arise from?
it’s retroperitoneal and arises around T12 vertebral level (does have some variation but usually around there) then supplies area around foregut (oesophagus to mid duodenum, liver, gallbladder, spleen and 1/2 of pancreas)
what are branches of coeliac trunk?
trifurcates into 3 branches:
- Splenic artery
- Hepatic artery
- Left gastric artery
each of these give rise to further branches (gastroduodenal and superior pancreaticoduodenal)
what does abdominal aorta bifurcate into?
common iliacs
what is course of splenic artery?
has very curly, bumpy course →runs along superior border of pancreas
what is location of spleen?
Intraperitoneal organ within left hypochondrium
has diaphragm posteriorly, stomach anteriorly, splenic flexure inferiorly, left kidney medially
what is an attempt to protect spleen?
soft organs so ‘Protected’ by ribs 9-11 →however rib fracture could pierce the soft , delicate spleen = substantial internal bleeding
what is function of spleen?
breaks down red blood cells and produces bilirubin (cover more later)
can you palpate spleen?
- generally not palpable unless enlarged but anatomy point of view should know that spleen and liver are closely related of diaphragm so have to time with breathing
- breathing in = moves down = more space in thorax and negative pressure for air →means that abdominal organs moved down so you can try and feel them
what is blood supply to stomach?
r+l gastric arteries run along lesser curve and anastomose together
r+l gastro-omental arteries runa long greater curve and anastomose together
where is
a) right and left gastric arteries arise from
b) right and left gastro-omental arteries arise from?
a) right from hepatic and left from coeliac trunk
a) right from gastroduodenal (from hepatic) and left from splenic
what gives blood supply to liver?
Hepatic artery→Branches into Right and Left hepatic arteries
= but that only accounts for 20-25% of blood received by liver, rest is from hepatic portal vein
where does superior mesenteric artery arise from?
abdominal aorta at level of L1 = supplies midgut organs
what are branches of superior mesenteric artery?
- inferior pancreaticoduodenal
- middle colic
- right colic
- ileocolic
- appendicular
- jejunal and ileal
what are branches of inferior mesenteric artery?
- left colic
- sigmoid colic
- superior rectal
what is significant anastomosis of superior and inferior mesenteric arteries?
= this anastomoses are predominantly one artery called the marginal artery of Drummond
→clinically important as blood can still get round if blocked by using the collateral supply
what blood supplies rectum?
internal iliac supplies the last bit of GI tract after hingut
what blood supply supplies the hindgut organs?
inferior mesenteric artery
what is pectinate line?
theoretical line along half of anal canal
what is hepatic portal system?
drains venous blood from absorptive parts of GI tract + associated organs to liver for “cleaning”
where does inferior vena cava drain?
runs behind liver (retroperitoneal)
- drains cleaned blood from the hepatic veins into the right atrium
what is systemic venous system?
drains venous blood from all other organs and tissues into superior or inferior vena cava
what does hepatic portal vein drain?
drains blood from foregut, midgut and hindgut structures to the liver for first pass metabolism - forms once 2 join together
what does splenic vein drain?
drains blood from foregut structures to hepatic portal vein
what does superior mesenteric vein drain?
drains blood from midgut structures to hepatic portal vein (which drains to liver for 1st pass metabolism)
what does inferior mesenteric vein drain?
drains blood from hindgut structures to splenic vein
what are the 3 main sites of anastamoses betwen hepatic portal venous system and systemic venous system?
- end of oesophagus (distal end) - superior part drains to systemic by azygous, inferior part drains into hepatic by left gastric (but lots of variation)
- skin around umbillicus (belly button) - drain back into common iliacs + inferior epigastric veins and then IVC
- rectum/anal canal - rectum and superior anal canal drain to inferior mesenteric vein, inferior part of GI drains into internal iliac veins
= at these sites, presence of small collaterals means blood can flow both ways either into systemic or hepatic venous systems (no valves)
what is portal hypertension and what happens?
- clinical term given to increased blood pressure within the portal veins
- can occur as a result of liver pathology, e.g. cirrhosis
- In the event of portal hypertension, blood will be diverted through the collateral veins back to the systemic venous system
- These collateral veins consequently have a much larger volume of blood through them than they are used to become varicose
a) what is rectul varices?
b) what are hemorrhoids
a) occurs because of portal hypertension
b) due to general increased pressure
*people often say interchangeably but not the same thing!
