Anatomy 5 - Bleeding in the GI tract Flashcards
what are the functions of the large intestine?
Defence (commensal bacteria)Absorption (H2O and electrolytes)Excretion
How is the caecum related to the peritoneum?
Intraperitoneal (quite mobile)
How is the ascending colon related to the peritoneum?
Secondarily retroperitoneal
What does secondarily retroperitoneal mean?
It originally was originally intraperitoneal (embryology)
What is the transverse colon in relation to the peritoneum?
intraperitoneal - highly mobile (has own mesentery)
Descending colon in relation to the peritoneum?
Secondarily retroperitoneal
What is the sigmoid colon in relation to the peritoneum?
Intraperiotneal - quite mobile as it has its own mesentery
Where are the 2 paracolic gutters?
Between the lateral edge of the ascending and descending colon and abdominal wall (called left and right paracolic gutters)
What are the paracolic gutters part of?
The greater sac of the peritoneal cavity
Where do the teniae coli run from and to?
From the caecum to the distal end of the sigmoid colon
What are the haustra?
Small pouches in the colon formed from the tonically contracted teniae coli
What causes darker blobs on a plain AXR?
Air
What does faeces appear like in the rectum on a plain AXR?
“Mottled” - mixture of air and faeces
In what part of the abdomen do the caecum and appendix lie?
The right iliac fossa
What is the opening of the ileum into the caecum called?
The ileocaecal orifice
What is the opening of the appendix into the caecum called?
Appendiceal orifice
How is the appendix most often located in comparison to the caecum?
Retrocaecal (64%)Position can vary causing a variation in the symptoms people present with e.g. men can present with testicular pain due to extending down to the pelvis and irritating structures
On what part of the caecum is the appendiceal orifice mostly always on?What does this correspond to?
The posteromedial wallMcBurney’s point (1/3 of the way between right Anterior Superior Iliac Spine and the umbilicus)Usually the point of maximum tenderness in appendicitis
In what part of the abdomen does the sigmoid colon lie?
left iliac fossa
What is the mesentery of the sigmoid colon called
Sigmoid mesocolon (gives it a considerable degree of movement)
Volvolus?
Abnormal twisting of a part of the GI tract
What is it called when the sigmoid colon twists around itself?What does this result in?What is the bowel at risk of if it is left untreated?
Sigmoid volvulusBowel obstructionInfarction
Where does the abdominal aorta lie in relation to the IVC?
Left of the IVC
What are the 3 midline branches of the abdominal aorta and what does each supply?
Celiac trunk (foregut organs)Superior mesenteric artery (midgut organs)Inferior mesenteric artery (hindgut organs)
What do the lateral branches of the abdominal aorta supply? (3)
Body wall (posterolateral)Kidneys/ adrenal glandsGonads (ovaries/ testicles)
What does the abdominal aorta bifurcate into?What does this further bifurcate into?
Common iliacsInternal and external iliacs
See diagrams on superior mesenteric artery and inferior mesenteric artery
…
What is the predominant artery which anastomoses between the branches of the SMA and IMA?
Marginal artery of Drummond
What do arterial anastomoses between the SMA and IMA help to do?
Prevent intestinal ischaemia by providing a collateral route by which blood can travel
Where does the hindgut extend to?
The proximal half of the nail canal (the pectinate line)
What is the name of the line that divides the 2 half of the anal canal?
The pectinate line
What is the remainder of the GI tract (from the pectinate line) supplied arterially by?
The internal iliac artery (middle and inferior rectal arteries branch from this) - there is a degree of anastomoses between these vessels
What are oesophageal varies
Abnormal dilated veins with thin walls which therefore have the potential to rupture
What often leads to the formation of varcies?
Pathology affecting the portal venous system
What 2 vessels does the systemic venous system drain blood into?
Superior or inferior vena cava
What does the inferior vena drain blood from in terms of the liver
Hepatic veins
What are the 3 vessels that drain blood into the hepatic portal vein
Splenic vein (foregut)Superior mesenteric vein (midgut)Inferior mesenteric vein (hindgut)
Are there any valves in the collateral veins of the portal systemic anastomoses
No - blood can flow either way
Where are the 3 portal systemic anastomoses?
Skin around umbilicusDistal end of oesophagusRectum/ anal canal
At the portal systemic anastomoses at the distal end of the oesophagus, where does the most inferior part and the most superior part drain
Superior = azygousInferior = hepatic portal veinAnastomoses form between these
At the portal systemic anastomoses at the rectum/ anal canal, where does the most inferior part and the most superior part drain
Rectum and superior anal canal drains to inferior mesenteric veinMost inferior part of the GI tract drains to the internal iliac veinsAnastomoses form between these
Portal-systemic anastomoses - skin around umbilicus?
normally the ligamentum teres remains closed throughout adult life and blood flows from the skin around the umbilicus via inferior epigastric veins to the IVC
Where does the superior rectal vein branch from?
Inferior mesenteric vein
Where does the middle rectal vein branch from?
The internal iliac vein
Where does the inferior rectal vein branch from?
The internal iliac vein
Name for increased blood pressure in the portal veins?What is this caused by?
Portal hypertensionLiver pathology e.g. cirrhosis
What happens during portal hypertension to cause varicose?
Blood is 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 so dilate becoming varicose
Clinical presentation of portal hypertension? (3)
Oesophageal varicesCaput medusaeRectal varcies
