Abdominal neurovasculature week 2

Question 1

Aortic supply to the abdominal viscera is:

a. intraperitoneal
b. retroperitoneal
c. secondarily retropertioneal

Answer 1

Aortic supply to abdominal viscera is retroperitoneal.

Question 2

What are the main arterial branches of the aorta that supply the abdominal viscera?

Answer 2

Aortic arterial supply to the abdominal viscera is retroperitoneal.
• 3 unpaired (celiac trunk, superior and inferior mesenteric) arterial trunks.
• Numerous paired somatic, segmental branches for the abdominal walls. Note that the paired lumbar arteries reappear in btwn the transversus abdominis and internal oblique
• Several paired visceral branches for retroperitoneal organs (in GU Block)

Question 3

What is the primary arterial supply to the abdominal wall?

What muscle does it run deep to? What artery does it join?

What other aa contribute to the blood supply of the abdominal wall?

Answer 3

Arterial supply:
• An interconnected system of arteries and veins supply the abdominal wall.
• The primary arterial supply is the superior epigastric artery.
• runs deep to the rectus abdominus.
• joins the inferior epigastric, a branch of the external iliac artery.
• Also contributing to the blood supply are the:
• lower posterior thoracic intercostal arteries; lumbar arteries; branches of the femoral artery (do not try to find these but know they exist.)

Question 4

What organs does the hepatic portal system drain?

What 2 veins come together to form the hepatic portal vein?

What ligament does the hepatic portal vein run in?

Answer 4

• Veins draining the abdominal wall generally follow the arterial pathways.
• The Hepatic Portal System drains the lower esophagus, stomach, small intestine, large intestine, and upper half of the anal canal. It also drains accessory digestive organs: gallbladder, spleen, and pancreas.
• The superior mesenteric vein and the splenic vein join to form the hepatic portal vein. Note that the inferior mesenteric vein drains into the splenic vein.
• The hepatic portal vein is in the hepatodudoendal ligament. This vein can be felt when putting your hand in the epiploic foramen of winslow.

Question 5

What is the caval system?

What drains deep abdominal viscera? Into what vein?

Answer 5

The caval system is sytemic drainage of organs into the SVC and IVC. Most of the venous blood drained goes to the caval system. It is unique for organs of the GI tract to drain into the hepatic portal system.

Paired veins drain deep abdominal viscera (e.g. kidneys, etc.) directly into the inferior vena cava.

Question 6

What 3 arteries are subject to ulcerations in the GI tract? Where are they located?

Answer 6

1. The splenic artery may be subject to erosion by a penetrating ulcer of the posterior wall of the stomach into the lesser sac.
2. The left gastric artery may be subject to erosion by a penetrating ulcer of the lesser curvature of the stomach.
3. The gastroduodenal artery may be subject to erosion by a penetrating ulcer of the posterior wall of the first part of the duodenum.

Question 7

What is an abdominal aortic aneurysm?

What is the most common site for an abdominal aneurysm?

What are signs/symptoms of an abdominal aneurysm?

What is the most common site of atherosclerotic plaques?

What are risk factors for an abdominal aneursym?

Answer 7

An abdominal aortic aneurysm is a dilatation of the aorta (in excess of 4 cm in diameter) can occur anywhere. Without surgical or endovascular intervention, the dilated artery usually continues to enlarge and may subsequently rupture.

The most common site for an abdominal aneurysm is in the area between the renal arteries and the bifurcation of the abdominal aorta (into the common iliac arteries). Signs include decreased circulation to the lower limbs and pain radiating down the back of the lower limbs. The most common site of atherosclerotic plaques is at the bifurcation of the abdominal aorta.

Abdominal aortic aneurysm risk factors include:
• Age - most often in people > 65
• Tobacco use
• Atherosclerosis
• Being male
• Family history

Question 8

The portal system is an extensive network fo veins that receives blood fro the GI tract. How does portal HTN affect this system? How can venous drainage of the GI tract still occur when blood flow to the liver is reduced?

What 3 conditions may reduce blood flow to the liver?

Answer 8

Portal Hypertension impacts the connections between the portal and caval venous drainage systems.

• Anastomoses between the portal and caval systems can be utilized when portal vein blood flow into the liver is reduced.

Esophageal varices, hemorrhoids, and caput medusa reduce blood flow to the liver.

Question 9

What are esophageal varices?

Answer 9

Abnormally engorged veins of the lower esophagus.

Question 10

caput medusa

Answer 10

Engorgement of periumbilical veins that are normally fused shut but can become engorged with blood with the appropriate pressure. Is seen with portal HTN which forces blood into collateral venous channels.

Question 11

What nerves supply innervation to the abdominal wall?

What is an important neural landmark on the abdomen?

Answer 11

• innervation from the thoracic intercostal nerves T7-T12 and L1.
• an important neural landmark is the umbilicus which marks the 10th thoracic spinal level.

Question 12

Question 13

Innervation of abdominal viscera is controlled by the ______ nervous system.

Answer 13

autonomic

Question 14

Explain the pathway splanchnic nerves travel to synapse on abdominal viscera.

Answer 14

1. Recall that the Autonomic Nervous System is a 2 neuron chain nervous system.
2. Recall that autonomic supply to blood vessels, sweat glands and smooth muscle in the body walls and extremities involves a synapse in the sympathetic (paravertebral) chain ganglia followed by a postsynaptic route to the target.
3. Recall that the autonomic supply to the viscera involves a splanchnic nerve (preganglionic) that passes through a sympathetic chain ganglion to reach a Prevertebral Ganglion. It synapses here and the postganglionic fibers then travel to the target.

Question 15

What are the two nerves by which abdominal viscera receive parasympathetic innervation?

Answer 15

vagus nerve (CN X)

pelvic splanchnic nerves

Question 16

What does the vagus nerve enter the abdomen as? Where does it synapse?

What abdominal viscera does it supply parasympathetic innervation to?

Answer 16

Vagus Nerve (CN X):
• enters abdomen as the anterior and posterior vagal trunks; passes through without synapsing in the prevertebral ganglia to synapse in terminal ganglia found in the wall of its target organ.
• supplies parasympathetic innervation to all abdominal viscera except the descending colon, sigmoid colon and rectum.

Question 17

Where do the neuron cell bodies of pelvic splanchnic nerves lie?

Where do their preganlionic neurons terminate?

In what nerves do these fibers ascend in?

Answer 17

Pelvic Splanchnic Nerves:
• arise from neuron cell bodies found in the 2nd, 3rd, and 4th sacral spinal cord segments.
• convey preganglionic parasympathetic fibers which synapse on postganglionic neurons in terminal ganglia in the descending colon, sigmoid colon, and rectum.
• these fibers ascend in the hypogastric nerves and the superior hypogastric plexus to reach the parts of the colon they will innervate.

Pelvic splanchnic nerves are parasympathetic. Splanchnic is a generic term for going through viscera. If a splanchnic neves comes from other parts of the spinal cord (thoracic, for ex), it is sympathetic. Remember pelvic is parasympathetic as PP

Question 18

Preganglionic sympathetic innervation for abdominal viscera is conveyed via _____ nerves.

Answer 18

splanchnic

Question 19

What levels of the spinal cord do sympathetic splanchnic nerves (that synapse on abdomina viscera) come from?

Where do they synapse?

Answer 19

• These splanchnic nerves come from thoracic levels (e.g. Greater, Lesser, and Least Splanchnics) or Lumbar levels (lumbar splanchnics) and travel to prevertebral ganglia.
• Postganglionic sympathetic neurons are located in prevertebral ganglia where splanchnic nerves synapse (Examples of prevertebral ganglia include the celiac, aorticorenal, superior and inferior mesenteric.)

Question 20

How do postganglionic sympathetic fibers reach their target organs?

Answer 20

Postganglionic sympathetic fibers exit prevertebral ganglia and travel to target organs via autonomic plexuses which follow branches of blood vessels. (These autonomic plexuses are mixed meaning they contain both sympathetic and parasympathetic fibers as well as afferent fibers from the organs, a.k.a. GVA fibers.)

Question 21

In relation to the abdominal aorta, where do pre-aortic nodes lie?

What are these nodes organized around?

What organs do they drain lymph from?

What are pre-aortic lymph nodes called collectively?

Answer 21

Pre-aortic nodes:
• lie anterior to the abdominal aorta.
• these nodes are organized around the 3 unpaired branches of the abdominal aorta.
• they drain lymph from the organs they supply with arterial blood.
• Thus, lymph from the stomach, small intestine, colon, spleen, pancreas, gallbladder and liver drains into the pre-aortic nodes (celiac, superior mesenteric and inferior mesenteric lymph nodes.)
• Pre-aortic nodes form the intestinal trunk.

Question 22

In relation to the abdominal aorta, where do para-aortic nodes lie?

What organs do they drain lymph from?

What are para-aortic lymph nodes form?

Answer 22

Para-aortic nodes:
• Right and left lateral aortic or lumbar nodes (a.k.a. para aortic nodes) lie on either side of the aorta.
• receive lymph from the abdominal body wall, kidneys, suprarenal glands and testes/ovaries.)
• form the right and left lumbar trunks.

Question 23

The right and left lumbar trunks and the intestinal trunk eventually coalesce to form what?

Answer 23

The right and left lumbar trunks and intestinal trunk eventually coalesce to form the cisterna chyli which empties is the beginning of the thoracic duct.