Spleen, Portal Vein, Aorta, and IVC

Question 1

What is the largest lymphoid organ in the body ?

Answer 1

Spleen

Question 2

Describe the anatomical location of the spleen in the adult ?

Answer 2

In the adult, the spleen is located just posterior to the stomach, agains the diaphragm, between ribs 8 (9) and 11 on the left side. Its long axis is along the 10th rib.

Intraperitoneal except hilum (latter not covered by peritoneum)

Question 3

What are the main functions of the spleen ?

Answer 3

• Removal and destruction of aged or defective blood cells
• Haematopoiesis in the fetus (until 5 months IU)
• Storage of platelets
• Removal of bloodborne antigens

Question 4

Describe any covering of the spleen. What it the clinical significance of this covering ?

Answer 4

The spleen is surrounded by a fibrous capsule from which trabeculae extend inwards.
Capsule is very weak, so if trauma, heavy bleeding

Question 5

Which organs is the spleen related to ?

Answer 5

The spleen is related to the colon (L colic flexure), stomach, and left kidney

Question 6

What is special about the superficial border of the spleen ?

Answer 6

The superficial border of the spleen is notched.

Question 7

Identify any ligaments connected to the spleen, and explain what they link the spleen to. What structures does each of these contain ?

Answer 7

1) Connected to the stomach by the gastrosplenic (gastrolienal) ligament
→ Contains L gastroepiploic and short gastric vessels
→ May also contain accessory spleen

2) Connected to the posterior abdominal wall by the splenorenal (lienorenal) ligament
→ Contains splenic vessels and tail of pancreas

Question 8

Describe the arterial supply of the spleen.

Answer 8

The splenic artery runs along the upper border of the pancreas, then divides into its branches that enter the spleen at its hilum.

Question 9

Describe the veinous and lymphatic drainage of the spleen.

Answer 9

1) Veinous drainage of spleen: splenic vein runs along the tail and body of the pancreas. It receives the short gastric and left gastroepiploic veins, then joins the superior mesenteric vein behind the neck of the pancreas to form hepatic portal vein.
2) Lymphatic drainage of spleen: Splenic hilar lymph nodes → pancreatico-splenic nodes → celiac nodes

Question 10

Describe the nervous supply of the spleen.

Answer 10

The nerves accompany the splenic artery.
Sympathetics: from the celiac plexus (greater splanchnic nerve, T5-T9)
Parasympathetics: from vagus

Question 11

Identify possibly injuries which could damage the spleen.

Answer 11

Because the capsule of the spleen is relatively thin, physical injury (rib fractures, trauma) or a serious infection can cause the spleen to rupture, causing considerable intraperitoneal haemorrhage.

Question 12

What is the management for ruptured spleen causing intraperitoneal haemorrhage ?

Answer 12

Splenectomy used to be expected management

Nowadays, angiography and embolisation may be preferred management along with observation and masterly inactivity.

Question 13

What structure is at risk in a splenectomy ?

Answer 13

In a splenectomy, great care must be taken to avoid damaging the tail of the pancreas while ligating the splenic vessels.

Question 14

Why is it possible to live without a spleen ?

Answer 14

A person without a spleen can live a relatively healthy life because macrophages in the liver and bone marrow can take over most of the spleen’s functions BUT such a person will be more susceptible to infections.

Question 15

What proportion of blood to the liver is provided by the hepatic arteries ? By the hepatic portal vein ?

Answer 15

Hepatic arteries: 30%

Hepatic portal vein: 70%

Question 16

What structures does the hepatic portal vein drain ?

Answer 16

Hepatic portal vein drains venous blood between the lower third of the esophagus and distal half of the anal canal as well as spleen, pancreas, and gall bladder.

Question 17

Describe the anatomical path of the hepatic portal vein.

Answer 17

Hepatic portal vein is formed posterior to the neck of the pancreas by the union of splenic and superior mesenteric veins. It then crosses the first (superior) part of the duodenum and enters the lesser omentum. It runs cranially in the hepatoduodenal ligament towards the porta hepatis. Finally, “immediately before reaching the liver”, it divides into R and L terminal branches.

Question 18

What is the structural specificity of the hepatic portal vein/its tributaries ?

Answer 18

Neither the hepatic portal vein, nor its tributaries, have valves inside

Question 19

Describe the function/actions of the portal vein inside the liver.

Answer 19

• The portal vein enters the liver and its branches supply the sinusoids from which blood passes into the central veins “(veins at center of hepatic lobules), which return to the blood into the circulation via hepatic veins that drain into the IVC”
• In the sinusoids, the portal veinous blood mixes with oxygenated blood from the hepatic artery proper.

Question 20

Define porto-systemic anastomoses, and identify the main ones.

Answer 20

Tributaries of the portal vein establish a connection with the tributaries of the systemic veins (SVC and IVC).

1) At the lower third of the esophagus
- esophageal branches of the L gastric vein (drain into portal vein)
- esophageal veins draining the middle third of the esophagus (drain into the azygos vein → SVC)

2) Halfway down anal canal
- superior rectal vein draining the upper half of the anal canal (drains into portal vein)
- middle and inferior rectal veins (drain into internal iliac and internal pudendal veins → IVC)

3) Around the umbilicus
- Para-umbilical veins (drain into L branch of portal vein)
- Epigastric veins (drain into femoral, external iliac, internal thoracic, and axillary veins → IVC and SVC)

4) Posterior abdominal wall
- Veins of secondary retroperitoneal organs (including bare area of liver) (drain into portal vein)
- Veins of body wall (drain into systemic veins)

5) Very rarely ductus arteriosus can re- canalize (Vein of Retzius)

Question 21

What are potential clinical problems with porto-systemic anastomoses ?

Answer 21

If the blood flow in the hepatic portal vein is diminished or blocked, blood will be shunted to the systemic veins via collateral veins (i.e. in the anastomoses). Hence, veins will be dilated at sites of porto-systemic anastomosis, i.e. PORTAL HYPERTENSION

1) esophageal varices (anastomosis at the lower third of the oesophagus, from L gastric to esophageal veins)
2) hemorrhoids (piles, anastomosis halfway down the anal canal, from superior rectal veins to middle and inferior rectal veins)
3) caput medusae can also result (anastomosis around umbilicus, from paraumbilical veins into superior and inferior epigastric veins).”

Question 22

Define portal hypertension. What are potential causes of portal hypertension ?

Answer 22

Increase in the blood pressure within portal venous system. Due to:

1) Pre-hepatic causes
- Portal vein thrombosis
- Splenic vein thrombosis

2) Hepatic causes
- Hepatic tumours (benign, malignant or metastatic)
- Cirrhosis (alcohol abuse, hepatitis, etc)
- Parasitic infestations (Eg. Schistosomiasis)

3) Post-hepatic causes
-Cardiac disease (severe tricuspid stenosis, restrictive cardiomyopathy, constrictive
pericarditis)
-Hepatic vein thrombosis
-Inferior vena cava thrombosis

Question 23

What is the location of the abdominal aorta relative to the peritoneum ?

Answer 23

Abdominal aorta is retroperitoneal

Question 24

Describe the path of the abdominal aorta.

Answer 24

• Begins at the aortic hiatus of the diaphragm at T12 (in the midline)
• Lies on vertebral column and descends to level of T4
• Bifurcates into common iliac arteries (slightly left of midline)

Question 25

Identify the main branches of the abdominal aorta.

Answer 25

1) Visceral branches
− Coeliac trunk (L1)
− Middle suprarenal arteries
− Superior mesenteric artery(L1) 
− Renal arteries (L1/2disk)
− Testicular or ovarian arteries (L2) 
− Inferior mesenteric artery (L3)

2) Parietal branches
− Inferior phrenic arteries
− 4x Lumbar arteries
− Median sacral artery

Question 26

What is the location of the IVC relative to the peritoneum ?

Answer 26

Retroperitoneal

Question 27

What is the function of the IVC ?

Answer 27

Conveys blood from the body below the diaphragm to the right atrium of the heart (not ALL though, because 1st and 2nd lumbar veins drain both into inferior vena cava, and into the ascending lumbar vein, which then become azyos and hemiazygos)

Question 28

Describe the anatomical path of the IVC.

Answer 28

Formed by the union of the common iliac veins behind the right common iliac artery at the level of L5

Ascends on the right side of the aorta piercing the central tendon of the diaphragm at T8

Question 29

Which veins does the IVC receive ?

Answer 29

− Hepatic veins
− Right inferior phrenic vein
− Right suprarenal vein (left vein drains into the left renal vein or left inferior phrenic vein)
− Both renal veins
− Right gonadal vein (left vein drains
into the left renal vein)
− Lumbar veins (3rd, 4th, and 5th, but only part of 1st and 2nd lumbar veins since those two also drain into ascending lumbar vein)

Question 30

What are the veins of origin of the IVC ?

Answer 30

2 common iliac veins and median sacral vein