Anatomy of GI bleeding Flashcards
What is the function of the large intestine
- Defence againt commensal bacteria
- Absorption - H2O and electrolytes
- Excretion of formed stool
Describe the anatomy of the colon
- Caecum, appendix, Ascending, transverse, Descending, Sigmoid
- Location: inferior to liver and Spleen
- From Caecum to sigmoid: intraperitoneal - Secondarily retroperitoneal - intraperitoneal - secondarily retroperitoneal - intraperitoneal
What are Paracolic gutter
- Spaces between the colon and the abdominal wall
- peritoneal recesses on the posterior abdominal wall lateral to the ascending and descending colon respectively.
Describe the anatomy of the paracolic gutters
- Left and right paracolic gutters
- Between lateral edge of the ascending and descening colon
- Postential sites for pus collection
What are the features of the colon
- Omental appendices
- Teniae coli - 3 longitudinal bands of thick SM
- Runing from the caecum once the come together at the appendix to the distal end of the sigmoid colon
3. Haustra - Sacculations cause by the contractions to teniae coli - Gives rise to the segmented appearance on colon
How does the colon look like one radiological appearance
describe the anatomy of the caecum and the appendix
- location = both in right iliac fossa
- postion of appendix is variable - but most commonly rectrocaecal
- Appendiceal orifice - posteriomedial wall of caecum - Mcbuney’s point on anterior abdominal wall
What is the Mcburney’s point and wheres its location
- Where the appendiceal orifice is found
- 1/3rd of the way between Right Asis to umbilicus
- Maximum tenderness when appendicitis
What is the anatomy of the sigmoid colon
- Location - Left iliac fossa
- Has a long mesentery - Sigmoid mesocolon - significant degree of movement
- Disadvantage of long mesentery - Risk of Twisting around itself - Sigmoid volvulus
- Results in bowel obstruction
- Bowel at risk of infarction
What is the anatomy of the abdominal aorta
- Midline Retroperitoneal structure
- lies to left of IVC
- 3 Midline branches - celiac trunk, SMA and IMA
- Lateral branches- renal, gonads and body wall
- Common illiac bifurcation - internal and external
What are all the levels of the abdominal aorta bifurcation
- SMA - L1
- IMA - L3
- Celiac trunk - T12
- Common illiac bifurcation - L4
What are all the branches of the SMA
- Inferior pancreaticodoudenal
- Middle colic artery
- Right colic artery
- ileocolic artery
- Appendicular
- Jejunal and ileal arteries
Describe the anatomy of Jejunal and ileal arteries
There both have a wasa rectae and arterial arcades
- Jejunum has longer vasa rectae and larger but fewer arcades
- Ileum has a shorter wasa resctae and small and many arcades
What are the branches of the IMA
- Left Colic artery
- Sidmoid arteries
- Superior rectal arteries
what is the marginal artery of drummond
Arterial anatomoses between the Branches of the superior mesenteric artery and inferior mesenteric artery - obstruction in these vessels can help prevent intestinal ischaemia
what do the IMA and SMA look like on imaging
What is the blood supply to the rectum and anal cana;
- Rectum - Superior rectal artery - branch of IMA
- Below pectinate line = internal illiac
Describe the 2 veous system in the body
- Hepatic portal venous system - Drains venous blood from absorptive parts of GI tract into liver for cleaning
- Systemic venous system - Drains all other parts of organs and tissue into SVC or IVC
What is the heptic porta vein made up on
Spleenic vein (foregut) and Superior mesenteric vein (Midgut Structures)
- Inferior mesenteric vein (hindgut) drains into the spleenic vein
Where are the important portal-system anastomosis
- Skin around umbilicus - Connect para-umbilical veins and Epigastric veins
- Rectum/anal canal - Inferior into iliac veins superior into IMV
- Distal end of Eosophagus - inferior part drains into Hepatic portal vein and Superior part drains into azygous vein
Venous drainage from the rectum and anal canal
What is Portal hypertension
- Hypertension of the HPV - due to Cirrhosis or Tumour compressing HPV
- Leads to reversal of blood flow
- Larger volume of blood to these areas can cause them to become varicosed
Clinical presentation of portal hypertension
What can the source of Haematemesis be
- peptic ulcer in wall of stomach
- Oesophageal varices
