anatomy of bleeding in the GI tract and abdominal vasculature

Question 1

what makes up the large intestine ?

Answer 1

> the colon - caecum, ascending, hepatic flexure, transverse, splenic flexure, descending, sigmoid
the rectum
the anal canal
the anus

Question 2

what are the function of the large intestine ?

Answer 2

• immune defence(via commensal bacteria)
• absorption (of water and electrolytes)
• excretion of formed stool

Question 3

sigmoid colon anatomical features

Answer 3

• lies in the left iliac fossa
• has a long mesentery (sigmoid mesocolon) so therefore is highly mobile > making it more at risk of volvulus (twisting around itself resulting in bowel obstruction)

Question 4

intraperitoneal parts of the colon

Answer 4

caecum
appendix
transverse colon
sigmoid colon

Question 5

retroperitoneal parts of the colon

Answer 5

ascending colon

descending

Question 6

what is the splenic flexure inferior to ?

Answer 6

the spleen

Question 7

what is the hepatic flexure inferior to ?

Answer 7

the liver

Question 8

anatomical features of the paracolic gutters

Answer 8

• there are two paracolic gutters
• they can be found at the lateral edge of ascending and descending colon and abdominal wall
• they are part of the greater sac of peritoneal cavity
• they are potential sites for pus collection

Question 9

what are the taeniae coli ?

Answer 9

3 distinct longitudinal bands of thickened smooth muscle

> haustra are formed by tonic contraction of the taeniae coli

Question 10

anatomical features of the caecum and appendix

Answer 10

• both lie in the right iliac fossa
• appendix is often retrocaecal
• the appendiceal orifice lies on the posteromedial wall of the caecum - corresponds to McBurney’s point (anterior abdominal wall, 1/3 between ASIS to umbilicus)

Question 11

what are the three midline branches that break off the abdominal aorta and what do they supply ?

Answer 11

• celiac trunk (foregut organs)
• SMA (midgut organs)
• IMA (hindgut organs)

Question 12

what do the lateral branches of the abdominal aorta supply ?

Answer 12

kidneys, adrenal glands, gonads, body wall

Question 13

what does the abdominal aorta bifurcate into ?

Answer 13

common iliac arteries

Question 14

what parts of the colon does the SMA supply ?

Answer 14

MIDGUT ORGANS

appendicular,
ileocolic,
right colic,
middle colic,
inferior pancreaticoduodenal,
and the SMA also contains the jejunal and ileal arteries

Question 15

what does the IMA supply ?

Answer 15

HINDGUT ORGANS

left colic,
sigmoid colic,
superior rectal

Question 16

what is the Drummond artery ?

Answer 16

a marginal artery that is an arterial anastomoses between the branches of the SMA and IMA

Question 17

what supplies the rectum and the anal canal ?

Answer 17

• IMA for organs above the pectinate line

- internal iliac artery supplies the rest

Question 18

how might haematemesis occur ?

Answer 18

> peptic ulcer of the stomach or duodenum erodes through the mucosa and so it starts to fill with blood

or

> bleeding from oesophageal varices due to abnormal dilated veins

Question 19

what are the two main venous systems of the body ?

Answer 19

hepatic portal venous

and

systemic venous system

Question 20

what does the hepatic portal venous system drain do ?

Answer 20

drains venous blood from absorptive parts of the GI tract and associated organs to the liver

Question 21

what does the systemic venous system drain do ?

Answer 21

drains venous blood from all other organs and tissues into the superior or inferior vena cava

Question 22

what are the venous systems of the GI tract ?

Answer 22

inferior vena cava, hepatic portal vein, splenic vein, SMV and IMV

Question 23

what does the IVC drain ?

Answer 23

cleaned blood from the hepatic veins to the RA

Question 24

what does the hepatic portal vein drain ?

Answer 24

drains blood form foregut, midgut and handout structures to the liver for first pass metabolism

Question 25

what does the splenic vein drain ?

Answer 25

drains blood from foregut structures to hepatic portal vein

Question 26

what does SMV drain ?

Answer 26

drains midgut structures to hepatic vein

Question 27

what does IMV drain ?

Answer 27

drains hindgut to splenic vein

Question 28

where would you find the portal systemic anastomoses ?

Answer 28

> distal end of the oesophagus
rectum / anal canal
skin around the umbilicus

Question 29

how is blood drained from the rectum and anal canal ?

Answer 29

• via the superior rectal vein (to the inferior mesenteric vein), the middle rectal vein and the inferior rectal vein (to the internal iliac vein)

Question 30

how does portal hypertension occur ?

Answer 30

when blood is diverted through collateral veins back to the systemic venous system when BP in the portal venous system is raised

Question 31

what are the clinical presentations of portal HPT ?

Answer 31

oesophageal varices,

caput medusae, rectal varices (not to be confused with piles_