Aterial Supply, Venous Drainage And Nervous Innervaton Of The GI Tract Flashcards
What does the GIT develop into in the embryo?
Three sections
Foregut
Midgut
Hindgut
What branches from the abdominal aortic the supply to GI tract?
3 large unpaired arteries
What supplies the foregut as a branch of the abdominal aorta?
Coeliac trunk/axis
What supplies the midgut as a branch of the abdominal aorta?
Superior mesenteric artery
What supplies the hindgut as a branch of the abdominal aorta?
Inferior mesenteric artery
What supplies the spleen?
The splenic artery
Where does the inferior mesenteric artery supply?
The distal 3rd of the transverse colon and down the descending and sigmoid colon and the upper part of the rectum
What supplies the rectum?
Superior rectal artery which is terminal branch from the inferior mesenteric artery
Middle and inferior rectal artery from internal iliacs
Where is the pancreas derived from?
The foregut from the dorsal and ventral bud
What is the pancreas supplied by?
Coeliac trunk and small branch from SMA
Which organs are derived for the foregut/supplied by the coeliac trunk?
Oesophagus
Stomach
Proximal 1 1/2 parts of the duodenum
Accessory organs - liver, gallbladder, superior portion of the pancreas, spleen
What s derived from the midgut/supplied by the superior mesenteric artey?
Distal 2 1/2 parts of duodenum Jejunum Ileum Caecum Ascending colon Proximal 2/3 transverse colon
What is derived from the hindgut/supplied by the inferior mesenteric artery?
Distal 1/ of transverse colon
Descending colon
Sigmoid colon
Rectum
Where does the celiac artery arise?
Almost straight after aortic hiatus in diaphragm around T12
How many branches does the celiac artery branch into?
3
What is the smallest/first branch of the celiac artery?
Left gastric artery
Where does left gastric artery supply?
Runs up left of oesophagus and passes back and runs own lesser curvature of stomach giving off branches
What is the biggest terminal branch of the celiac artery?
Splenic artery
Where does the splenic artery run?
From the celiac trunk, behind the stomach along the superior border of the pancreas, towards the hilum of the spleen, giving off the short gastric branches to the fundus of the stomach and the gastroepiploic branches
Where does the left gastroepiploic artery run?
Along the greater curvature of the stomach where it anastomoses wth the right gastroepiploic artey
What is the lesser curvature supplied by?
Gastric arteries
What is the greater curvature of the stomach supplied by?
Gastroepiploic arteries
What are the 3 branches of the celiac artery?
Left gastric artery
Splenic artery
Hepatic artery / common hepatic artery
What does the common hepatic artery run into?
The hepatic proper
Where does the hepatic artery run to?
Runs up and branches to the left and right lobes of the liver
What does the hepatic artery run alongside?
The portal vein
Where does the hepatic artery run?
The free edge of the lesser omentum with the hepatoduodenal ligaments on the edge of it along with the bile duct
What branches off the hepatic artery?
Right gastric artery which passes up the lesser curvature to anastomose with the left
Gastroduodenal artery which give off the right gastroepiploic artery
Superior pancreaticoduodenal artery which supplies bits of head of the pancreas and bits of the duodenum
Why is it okay if there is a blockage in the left gastric artery?
Thee is still a blood supply to the lesser curvature of the stomach from the right gastric artery
What gives off the right gastroepiploic artery?
Gastroduodenal artery
Where do the left and right gastroepiploic arteries meet?
The greater curvature of the stomach
Explain how the right gastroepiploic artery is derived from the celiac artery initially
The right gastroepiploic artery is derived from the gastroduodenal artery which s derived from the hepatic artery which is derived from the celiac artery
What branch supplies the pancreas from the superior mesenteric artery?
The inferior pancreaticoduodenal artery
At what vertebral level does the superior mesenteric artery branch off the abdominal aorta?
L1
What does the inferior pancreaticoduodenal artery anastomose with at the head of the pancreas?
Superior pancreaticoduodenal artery
Where does the midgut start/what does the SMA supply?
Hepatoduodenal papillae (distal 2 1/2 parts of the duodenum) and runs all the way along the jejunum, the ileum, the caecum, the appendix, up the ascending colon and to proximal 2/3 of the transverse colon just before the left splenic flexure
What is the right colic artery a branch of?
The SMA
What does right colic artery supply?
Right side of colon so supplied caecum and ascending colon
What artery runs along the mesentery?
Ileocolic artery
What branches off the ileocolic artery?
Anterior and posterior cecal artery
Appendicular artery
What artery runs in the appendicular mesentery towards the appendix?
Appendicular artery
Which arteries run in between the sheets of the mesentery?
Jejunal arteries and illegal arteries
What artery supplies most of the transverse colon?
Middle colic artery
What branches from the superior mesenteric artery?
Ileocolic artery
Middle colic artery
Right colic artery
Where does the left colic artery supply?
Left part of colon, descending colon and distal 1/3rd of transverse colon
What branches from the inferior mesenteric artery?
Left colic artery
Sigmoid arteries
Superior rectal artery (termination)
What is the big anastomoses around the colon described as?
The marginal artery - connection between right middle and left colic artery form one line
What does venous blood from the greater part of the GI tract and accessory organs drain to the liver by?
Portal Venous System
What is the portal vein formed by?
The union of the superior mesenteric and splenic veins behind the neck of the pancreas
When the portal vein enters the liver, what happens?
It breaks up not sinusoids, from which blood passes into the hepatic veins that join the inferior vena cava
What are sinusoids?
Modified capillaries with really large pores
What does not form the portal vein but still drains into the portal system?
Inferior mesenteric vein - usually drains into splenic vein
What is the first pass effect?
Drugs absorbed through the GIT are metabolised by the liver before reaching the systemic circulation so only a small amount of active drug reaches the circulation
Where do small communications between the portal and systemic systems exist?
Oesophageal (lower third of oesophagus)
Rectal (branches from rectal veins)
Paraumbilical
Retroperitoneal (colic)
Where does the superior rectal vein come from?
Inferior mesenteric vein
Where do middle and inferior rectal veins come from?
Internal iliac
What is oesophageal varices?
Portal hypertension, commonly caused by cirrhosis
Dilated veins in lower third of oesophagus
Can lead to life threatening haemorrhaging
What nerves have a craniosacral outflow?
Parasympathetic nerves
What nerves have thoracolumbar outflow?
Sympathetic trunk
What is the GI’s nervous system?
Enteric nervous system which works with the autonomic (para/sympathetic) nervous system
What is the rest & digest nervous system?
Parasympathetic
What is the sympathetic ns?
Inhibits activity of GIT
Fight or flight response