Flashcards in L9. Nerves and Vessels of the Abdomen Deck (33):
Where does anterior supply of the blood to the abdomen come from? Describe the path of this vessel
It begins at the midline at T12/L1 (where it crosses the diaphragm) and ends anterior to L4 by dividing into a right and left common ileac artery (external for lower limb and internal for pelvis)
Describe the major classes of branches coming off the abdominal aorta (3) and generally what they supply
There are three unpaired sets of branches as it descends: supply gastrointestinal viscera and the derivatives [shown in green]
Three paired branches coming of the lateral edges of the abdominal aorta for the paired structures: kidneys, adrenals, and the gonads (ovaries and testes - because they develop in the lumbar region and descend)
A series of paired posterior branches which supply the walls of the abdominal cavity (diaphragm and lumbar vessels: phrenic and lumbar)
What are the three major layers of the primitive gut tube
Foregut, Midgut and Proximal gut
What are the three unpaired anterior branches off the abdominal aorta that supply the abdominal contents?
1. Celiac trunk
2. Superior Mesenteric Artery: SMA and
3. Inferior Mesenteric Artery: IMA
What is the relationship between the three abdominal layers of the primitive gut tube and the unpaired anterior branches
Celiac trunk supplies the foregut
Superior mesenteric artery supplies the midgut
Inferior mesentery artery supplies the proximal gut tube
What does the foregut tube give rise to?
Makes up the solid viscera from the gut tube: liver, gall bladder, pancreas, spleen, plus the first part of the GIT abdominal oesphagus, stomach and duodenum down to the major duodenal papilla
What does the midgut tube give rise to?
Rest of duodenum, Jejunum and ilium, cecum and ascending colon, transverse colon (just proximal to the splenic flexure
What does the proximal gut tube rise to?
Everything beyond that point (rest of transverse colon) of the splenic flexure, descending, sigmoid, rectum and first part of the anal canal
What is the first branch off the front of the aorta? Describe it and where it comes off
Celiac Trunk is the first branch off the front of the aorta. It is short wide trunk before breaks down into terminal branches. Usually arises at the superior border of the pancreas (T12) and immediately breaks into 3 branches
What are the three branches of the celiac trunk?
Left gastric Artery
Common Hepatic Artery
Describe the course of the left gastric artery and what it supplies
It arches upwards and to the left to lesser curvature of the stomach giving supply into the stomach. It gives oesophageal branches and then turns and runs along the lesser curvature
Describe the course of the splenic artery and what it supplies
It runs along the superior border of the pancreas towards the hilum of the spleen (very torturous course with lots of twists & turns). It also supplies the major part of the body and tail of the pancreas as it runs with it. As it also runs behind the stomach it sends short gastric vessels to the fundus of the stomach and gives the LEFT GASTRO-EPIPLOIC ARTERY which runs along the greater curvature of the stomach.
Describe the course of the common hepatic artery and what it supplies
It turns right to the free edge of the lesser omentum where gives rise to PROPER HEPATIC ARTERY which ascends in the free edge of the omentum to the porta hepatis.
Typically the CYSTIC ARTERY branches off the right hepatic artery (but variability in where it arises occurs) to supply the gall bladder.
It also gives off a branch called the GASTRODUODENAL ARTERY, which turns down and runs behind the first part of the duodenum. It gives rise to the right gastroepiploic running along the greater curvature and meets the left gastroepiploic from the spleen.
The gastroduodenal artery also gives off the SUPERIOR PANCREATICODUODENAL ARTERY (top half of duodenum and head of pancreas associated with it). The RIGHT GASTRIC ARTERY comes off the proper hepatic artery as it has already turned up in the free edge of the lesser omentum.
When and how does the Superior Mesenteric Artery Arise?
Comes of front of the abdominal aortic artery under the celiac trunk about the level of L1
The artery that supplies the midgut structures
What is the first branch of the SMA? What is its course and what does it supply?
The INFERIOR PANCREATICODUODENAL ARTERY, which is given off straight away and goes up to supply the inferior part of the head of the pancreas and distal part of the duodenum
How does the superior mesenteric artery descend down the abdominal cavity? What is important to know as it does this?
The SMA ‘walks’ along posterior abdominal wall in the oblique root of The mesentery from DJF, crossing front of vessels, psoas major muscle towards the right lower quadrant.
As it descends.. brancesh on the left = small intestine and branches on the right = large intestine
Describe the arterial supply to the small vs. large intestine via the superior mesenteric artery
LEFT: Jejunal and iliac arteries which feed into vascular arcades and then to vasa recta
RIGHT: Colic arteries (that are variable) off the right side of the superior mesenteric artery: ILIOCOLIC ARTERY, right and middle COLIC BRANCHES supplying parts of the midgut colons.
Describe the colic and marginal artery organisation of supply to the intestine
COLIC ARTERIES (superior or inferior) feed into MARGINAL ARTERIES which run along the edge of the mucosal tube of the large intestines all the way around (parallel vessel) and intermittently giving off short, straight arteries into the mucosal tube.
Where and when does the inferior mesenteric artery arise from the abdominal aorta?
At the inferior border of the third part of the duodenum (At the level of L3)
Describe the path of the inferior mesenteric artery
Heads diagonally into the left lower quadrant, inferior laterally and gives off a series of colic branches:
These supply the terminal transverse colon, descending and sigmoid colon
After this it changes its name into the SUPERIOR RECTAL ARTERY and heads down into the pelvis
Where do all gastrointestinal tract and derivative organs drain their venous blood into? What is the exception?
All through the portal system of veins
All except the liver
Describe the venous drainage of the gastrointestinal contents
Venous systems of the various parts of the tube and the derivative organs (except liver) unite into a single PORTAL VEIN, which takes the portal blood to the liver via the porta hepatis.
Why does venous drainage from the gut go through the liver?
What happens to the blood after it has passed through the liver?
At the porta hepatis it splits into left and right and into the liver to into the lobes of the liver through hepatic sinusoids for cleansing of the blood it collects
After, the blood recollects into hepatic veins and into the IVC just before it passes through the diaphragmatic hiatus.
Where do the retroperitoneal structures: adrenal, renal, gonadic, phrenic and lumbar veins drain into?
Directly into the IVC
How does portal hypertension arise?
Portal vein perfuses liver at a relatively low pressure. If liver sinusoids becomes fibrosed (Eg. repeated inflammation, cirrhosis - alcohol damage) there is no pressure gradient for portal flow: difficult venous return into liver.
What is a major characteristic of the portal veins that allows for a compensatory mechanism for portal hypertension?
The portal venous system is valveless, it allows a reversal of flow and portal venous system looks for an alternative way of getting blood into the IVC.
What kind of sites does the venous blood tend to shunt into the systemic blood?
This occurs at sites where there is an overlap of venous drainage into the portal system and into systemic system = porto-systemic anastomosis (tributaries portal vein is next to tributaries vein of IVC)
What are the 5 major or alternative routes for deoxygenated blood to leave the gastrointestinal area?
- Lower end of the oesophagus (because the middle oesophagus goes into azygous)
- The anal canal: because the middle and inferior veins drain into the IVC thus when the superior rectal vein gets engorged blood is forced here
- The veins of the anterior abdominal wall (the umbilical vein, now ligamental teres - in desperate times can open and recanalise allowing blood flow through veins in the anterior abdominal wall)
- Enteric: When abdominal blood meant for the portal system sits in the abdomen: retroperitoneal space behind ascending/descending colon and another top of the liver where it sits against the diaphragm
What branch of the nervous system is the abdominal viscera innervated by?
Describe the sympathetic and parasympathetic innervation of the abdominal viscera
- Sympathetic ganglion cluster around the unpaired branches of aorta and the renal arteries. The Preganglionic sympathetic fibres are derived from T6-L2
- The Parasympathetic innervation is from VAGUS to foregut and midgut but PELVIC SPLANCHNICS for hindgut
How do the sympathetic post-ganglionic fibres pass from the sympathetic ganglia to their respective viscera?
From where to the nerves arise for the three different segments?
Postganglionic fibres pass to viscera with blood vessels in the mesentery:
- foregut T6-9
- midgut T8-12
- hindgut T12-L2
Describe the visceral AFFERENTS
Visceral afferents pass to same spinal cord segment involved in
sympathetic innervation up for all segments and organs up to the mid sigmoid colon.
Beyond that they run with parasympathetics