Anatomy of bleeding in the GI tract

Question 1

describe the components of the large intestine, from proximal to distal.

Answer 1

- Colon 
= caecum
= appendix
= ascending colon
= transverse colon
= descending colon
= sigmoidal colon 

• rectum
• anal canal
• anus

Question 2

what are 3 functions of the large intestine?

Answer 2

1) defence
= commensal bacteria

2) absorption
= H20 and electrolytes

3) excretion
= of formed stool

Question 3

describe the colons anatomical position.

Answer 3

= intra-peritoneal (quite mobile)
= secondarily retro-peritoneal
= intra-peritoneal (highly mobile as it has its own mesentery)
= secondarily retro-peritoneal
= intra-peritoneal (quite mobile as it has its own mesentery)

• inferior to liver
• inferior to spleen

Question 4

what are paracolic gutters?

Answer 4

= spaces between the colon and the abdominal wall

Question 5

how many paracolic gutters are there?

Answer 5

= 2; right and left

- located between lateral edges of ascending and descending colon and abdominal wall

Question 6

what are the paracolic gutters part of?

Answer 6

= greater sac of peritoneal cavity

Question 7

what re paracolic gutters potential sites for?

Answer 7

= pus collection

• similar to sub-phrenic or hepatorenal recesses

Question 8

what are 3 distinguishing features of the colon?

Answer 8

1) omental appendices
2) teniae coli
3) haustra

Question 9

describe the teniae coli.

Answer 9

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

Question 10

True or False.

Splenic flexure, usually, lies more superior that hepatic flexure.

Answer 10

True

Question 11

what are omental appendices?

Answer 11

= small, fatty, projections

Question 12

how are haustra formed?

Answer 12

= by tonic contractions of tenaie coli

Question 13

what is used as a contrast in radiology and how is it administered?

Answer 13

= barium
- administered via an enema
(enema = procedure in which liquid is injected via the rectum)

Question 14

where do the caecum and appendix lie?

Answer 14

= in the right iliac fossa

Question 15

describe the position of the appendix?

Answer 15

= variable (accounts for why patients have differences when presenting with appendicitis)
= often retro-caecal

Question 16

where is the appendiceal orrifice?

Answer 16

= on postero-medial wall of caecum

Question 17

where does the appendiceal orrifce correspond with?

Answer 17

• corresponds to McBurney’s point on the anterior abdominal wall
• 1/3 of the way between right ASIS to umbilicus
• maximum tenderness in case of appendicitis

Question 18

where does the sigmoidal colon lie?

Answer 18

= in left iliac fossa

Question 19

describe the mesentery fo the sigmoidal colon?

Answer 19

= long mesentery (sigmoid mesocolon)

- giving it a considerable degree of movement

Question 20

what is a negative side to the long mesentery possessed by sigmoidal colon?

Answer 20

= the sigmoidal colon is at risk of twisting around itself

sigmoidal volvulus

Question 21

what is sigmoid volvulus and what does it result in?

Answer 21

= when the sigmoidal colon twists round itself
= resulting in bowel obstruction
- bowel at risk of infarction if left untreated

Question 22

describe where the abdominal aorta lies?

Answer 22

= midline, retroperitoneal structure

- lying anterior to vertebral bodies and to left of IVC

Question 23

how many midline branches does the abdominal aorta have?

Answer 23

= 3 midline branches

• ceoliac trunk (foregut organs)
• superior mesenteric artery (midgut organs)
• inferior mesentery artery (hindgut organs)

Question 24

what do the lateral branches of the abdominal aorta supply?

Answer 24

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

Question 25

what does the abdominal aorta bifurcate into?

Answer 25

= common iliac (L4) | - further bifurcates to internal and external iliac

Question 26

Name 6 branches of the superior mesenteric artery.

Answer 26

- jejunal and ileal arterries - appendicular - ileocolic branches - right colic artery - middle colic artery - inferior pancreaticoduodenal look at the image of the superior mesenteric artery, slide 10.

Question 27

describe the difference between the jejunal and ileal arteries?

Answer 27

Jejunum = longer vasa rectae = larger and fewer arcades Ileum = shorter vasa rectae = smaller and many arcades

Question 28

Name 3 branches of inferior mesenteric artery.

Answer 28

- left colic artery - sigmoidal artery - superior rectal artery look at the image of the superior mesenteric artery, slide 12.

Question 29

what is the marginal artery of drummond?

Answer 29

= arterial anastomoses between the branches of the superior mesenteric artery and inferior mesenteric artery

Question 30

what could these anastomoses help prevent?

Answer 30

= they could help prevent intestinal ischaemia by providing an alternative (collateral) route by which blood can travel

Question 31

what does the superior rectal artery, a bunch of inferior mesenteric artery, supply?

Answer 31

= hindugtt extends too proximal half of the anal canal (the pectinate linen)

Question 32

what is the remainder of the GI tract supplied by?

Answer 32

= the internal iliac artery | - there is an anastomoses between these vessels

Question 33

what are the bodies 2 main venous systems and what do they drain?

Answer 33

1) hepatic portal system = drains venous blood from absorptive part of GI tract & associated organs to liver for 'cleaning' 2) systemic venous system = drains venous blood from all other organs and tissues into the superior or inferior vena cava

Question 34

what does the inferior vena cava (retro-peritoneal) drain?

Answer 34

drains cleaned blood from the hepatic vein into the right atrium

Question 35

what does the hepatic portal vein and splenic vein drain?

Answer 35

Hepatic portal vein = drains blood from foregut, midgut and hindgut structures to the liver for first pass metabolism. Splenic vein = drains blood from foregut structures to hepatic portal vein

Question 36

what does the superior mesenteric and inferior mesenteric vein drain?

Answer 36

Superoir mesenteric vein = drains blood from midgut structures to hepatic portal vein Inferior mesenteric vein = drains blood from hindgut structures to splenic vein

Question 37

describe the 3 clinically important sites of venous anastomosis between the systemic and portal venous system?

Answer 37

= at these sites, the presence of small collateral veins means blood can flow both ways; - either into systemic or portal venous system - there are no valves in these veins - normally there is very little blood flow within these collateral veins

Question 38

what are the 3 parts to the portal-system anastomoses?

Answer 38

1) distal end of oesophagus 2) skin around umbilicus 3) rectum/anal canal

Question 39

describe what the inferior and superior part of the distal end of the oesophagus drains?

Answer 39

inferior part = drains into hepatic portal vein Superior part = drains into azygous vein

Question 40

describe the skin around umbilicus.

Answer 40

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

Question 41

describe the rectum/anal canal?

Answer 41

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

Question 42

what is portal hypertension and what can cause it?

Answer 42

= elevation of blood pressure in the portal system Can be caused by; - liver pathology (cirrhosis) - tumour compressing HPV

Question 43

what does portal hypertension lead to?

Answer 43

= reversal of blood flow

Question 44

what does a larger volume of blood flow to these anastomotic (collateral) areas cause?

Answer 44

= them to become varicosed

Question 45

what are 2 clinical features of portal hypertension?

Answer 45

1) oesophageal varices - dilated sub-mucosal collateral veins 2) caput medusae - dilated para-umbilical and dilated epigastric veins

Question 46

what is haematemesis?

Answer 46

= vomiting up blood

Question 47

what are the options for the causes of haematemesis?

Answer 47

1) peptic ulcer in wall of stomach or duodenum - erodes through the mucosa - stomach or duodenum fills with blood 2) bleeding from oesophageal varives - abnormal dilated veins - thin walls, therefore the potential to rupture = filling oeosphagus with blood - formation often due to pathology affecting portal venous system