Anatomy of Bleeding in the GI Tract

Question 1

large intestine components

Answer 1

colon
rectum
anal canal
anus

Question 2

colon components

Answer 2

caecum 
appendix 
ascending colon 
transverse colon
descending colon 
sigmoid colon

Question 3

functions of the large intestine

Answer 3

defence- commensal bacteria
absorption- H20 and electrolytes
excretion- of formed stool

Question 4

paracolic gutters locations

Answer 4

left and right

between lateral edge of ascending and descending colon and abdominal wall

Question 5

what are the paracolic gutters part of?

Answer 5

peritoneal cavity

Question 6

importance of parabolic gutters

Answer 6

potential sites for pus collection

Question 7

distinguishing features of colon

Answer 7

omental appendices
tenure coli
haustra

Question 8

omental appendices

Answer 8

small, fatty projections

Question 9

teniae coli

Answer 9

3 distinct longitudinal bands of thickened smooth muscle, running from caecum to distal end of sigmoid colon
come together at the appendix

Question 10

haustra

Answer 10

formed by tonic contraction of the teniae coli

Question 11

caecum and appendix location

Answer 11

both lie in the right iliac fossa but location of the appendix is variable (most often retrocaecal)

Question 12

what does the variation of the position of the appendix account for?

Answer 12

the different ways in which patients can present with appendicitis

Question 13

where is the appendiceal orifice?

Answer 13

on posteromedial wall of caecum

Question 14

what does the appendiceal orifice correspond to?

Answer 14

McBurney’s point (1/3 of the way between ASIS to umbilicus)

Question 15

where does the sigmoid colon lie?

Answer 15

in the left iliac fossa

Question 16

sigmoid colon

Answer 16

has a long mesentery which gives it a considerable degree of movement but also means it is at risk of twisting around itself

Question 17

sigmoid volvulus

Answer 17

when the sigmoid colon twists round on itself resulting in bile obstruction
bowel at risk of infarction if left untreated

Question 18

location of abdominal aorta

Answer 18

midline, retroperitoneal structure

lies anterior to vertebral bodies and to left of IVC

Question 19

3 midline branches of abdominal aorta

Answer 19

celiac trunk
superior mesenteric artery
inferior mesenteric artery

Question 20

what supplies the foregut organs?

Answer 20

celiac trunk

Question 21

what supplies the midgut organs?

Answer 21

superior mesenteric artery

Question 22

what supplies the inferior mesenteric artery?

Answer 22

hindgut organs

Question 23

what do the lateral branches of the abdominal aorta supply?

Answer 23

kidneys/ adrenal glands 
gonads (testes/ovaries) 
body wall (posterolateral)

Question 24

what does the abdominal aorta bifurcate into?

Answer 24

common iliacs

Question 25

what do the common iliacs further bifurcate into?

Answer 25

internal and external iliacs

Question 26

branches of the superior mesenteric artery

Answer 26

``` appendicular ileocolic branches right colic artery middle colic artery inferior pancreaticoduodenal ```

Question 27

jejunal arteries

Answer 27

longer vasa rectae | larger and fewer arcades

Question 28

ileal arteries

Answer 28

shorter vasa rectae | smaller and many arcades

Question 29

branches of the inferior mesenteric artery

Answer 29

left colic artery sigmoid arteries superior rectal artery

Question 30

marginal artery of Drummond

Answer 30

arterial anastomoses between the branches of the SMA and the IMA depending on the health of these and the speed at which obstruction occurs, these could help prevent intestinal ischaemia by providing an alternative (collateral) route by which blood can travel

Question 31

blood supply to rectum and anal canal

Answer 31

``` superior rectal artery, a branch of IMA internal iliac artery middle rectal artery inferior rectal artery there is an anastomoses between these vessels ```

Question 32

where does the hindgut extend to?

Answer 32

the proximal half of the anal canal (the pectinate line)

Question 33

hepatic portal venous system

Answer 33

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

Question 34

systemic venous system

Answer 34

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

Question 35

inferior vena cava (retroperitoneal)

Answer 35

drains cleaned blood from the hepatic veins into the right atrium

Question 36

hepatic portal vein

Answer 36

drains blood from the foregut, midgut and hindgut structures to the liver for first pass metabolism

Question 37

splenic vein

Answer 37

drains blood from foregut structures to hepatic portal vein

Question 38

superior mesenteric vein

Answer 38

drains blood from midgut structures to hepatic portal vein

Question 39

inferior mesenteric vein

Answer 39

drains blood from hindgut structures to splenic vein

Question 40

portal-systemic anastamosis

Answer 40

at these sites, the presence of small collateral veins means blood can flow both ways no valves normally little blood flow

Question 41

three sites of portal-systemic anastomoses

Answer 41

skin around umbilicus distal end of oesophagus rectum/ anal canal

Question 42

skin around umbilicus

Answer 42

connection between para-umbilical veins and small epigastric veins para-umbilical veins to hepatic portal vein along the round ligament of liver epigastric veins drain to caval system

Question 43

distal end of oesophagus

Answer 43

inferior part drains to the hepatic portal vein | superior part drains to the azygous vein

Question 44

rectum/anal canal

Answer 44

rectum and superior anal canal drains to inferior mesenteric vein inferior part of GI tract drains to the internal iliac veins

Question 45

portal hypertension

Answer 45

elevation of blood pressure in the portal system

Question 46

what can cause portal hypertension?

Answer 46

``` liver pathology (cirrhosis) tumour compressing HPV ```

Question 47

what does portal hypertension lead to?

Answer 47

reversal of blood flow | larger volume of blood flow to these anastomotic areas causes them to become varicosed

Question 48

clinical presentation of portal hypertension

Answer 48

oesophageal varices caput medusae rectal varices

Question 49

causes of haematemesis

Answer 49

bleeding from oesophageal varices | peptic ulcer in wall of stomach or duodenum