08-02-23 - Spleen, hepatic portal vein and large vessels Flashcards
Learning outcomes
- Describe the anatomy (position, function, relations, neurovascular supply) of the spleen
- Describe the anatomy (topography, position, function, relations) of the portal vein and its major tributaries
- Describe the anatomy (topography, position, function, relations) of the aorta and its major branches
- Describe the anatomy (topography, position, function, relations) of the inferior vena cava (IVC) and its major tributaries
- Explain the anatomical bases of the clinical conditions affecting the spleen, portal vein, aorta and inferior vena cava
What is the spleen?
How is it similar to a lymph node?
What are 4 functions of the spleen?
- The spleen is the largest lymphoid organ (part of the immune system)
- The spleen is like a large lymph node, but filters blood instead of lymph
- 4 functions of the spleen:
1) Removal of blood-borne antigens
2) Removal and destruction of aged or defective blood cells
* Iron recycled
* Iron stored as ferritin
3) Hematopoiesis in the fetus (up until 5 months IU until bone marrow develops and takes over)
4) Storing blood platelets and RBC
Where is the spleen located?
Where is it located on its long axis?
- In the adult, the spleen lies just posterior to the stomach, against the diaphragm & between ribs 8(9)-11 on the left side
- It is one of the most posterior intraperitoneal structures
- Its long axis is along the 10th rib
What does the spleen develop from?
What parts of the spleen are intraperitoneal?
What is the spleen surrounded by?
Where is the spleen notched?
What can this allow you to do?
What does the spleen parenchyma consist of?
What 3 structures is the spleen related to?
- The spleen develops within the dorsal mesentery/mesogastrium, meaning it develops from mesoderm/mesenchyme
- The spleen is an intraperitoneal structure, except for the hilum where structures enter and exit
- The spleen is surrounded by a fibroelastic capsule from which trabeculae extend inward
- The superior border of the spleen is notched, which can allow you to differentiate the spleen from other masses
- The spleen parenchyma (functional organ tissue) consists of red (involved in immune function) and white pulp surrounded by stroma
- 3 structures the spleen is related to:
1) Colon (left colic flexure)
2) Stomach
3) Left kidney
How is the spleen connected to the stomach?
What 3 structures does the gastrosplenic (gastrolienal) ligament contain?
How is the spleen connected to the posterior abdominal wall?
What 2 structures does the splenorenal (lienorenal) ligament contain?
What are the gastrosplenic and splenorenal ligaments remnants of?
- The spleen is connected to the stomach through the gastrosplenic (gastrolienal) ligament
- 3 structures the gastrosplenic (gastrolienal) ligament contain:
1) Left gastroepiploic artery (branch of splenic artery)
2) Short gastric vessels
3) May contain accessory spleen - The spleen is connected to the posterior abdominal wall by the splenorenal (lienorenal) ligament, which also attaches the spleen to the kidney (retroperitoneal)
- 2 structures the splenorenal (lienorenal) ligament contains:
1) Splenic vessels (arteries and veins)
2) Tail of the pancreas - The gastrosplenic and splenorenal ligaments are remnants of dorsal mesentery
What is the arterial supply of the spleen?
Where can the splenic artery be found?
What is it the largest branch of?
What is the venous drainage of the spleen?
What 3 veins does the splenic vein receive blood from?
How is the hepatic portal vein formed?
- The splenic artery is the arterial supply of the spleen
- The splenic artery runs along the upper border of the pancreas and can be found in the splenorenal ligament
- It is the largest branch of the coeliac trunk, as endocrine organs naturally require a lot of blood
- The splenic vein is the venous drainage of the spleen
- 3 veins the splenic vein receives blood from:
1) Short gastric vein
2) Left gastro-epiploic vein
3) Inferior mesenteric veins - Behind the pancreas, the splenic vein joins the superior mesenteric vein to form the hepatic portal vein
Describe the pattern of lymph node drainage in organs of the abdomen.
Describe the sequence of lymph drainage in the spleen (3 steps).
What does the nerve supply of the spleen accompany?
What is the sympathetic and parasympathetic supply of the spleen?
What is the role of sympathetics on tone of the smooth muscle?
How does this aid in the functioning of the spleen?
Why is this important in cases of haemorrhage?
How will nerves that supply to the spleen reach the spleen?
- In organs in the abdomen, lymph drains into lymph nodes in the meso, then to lymph nodes surrounding their arterial supply, then to lymph nodes around the origin of their arterial supply
- Sequence of lymph drainage in the spleen - Splenic hilar lymph nodes to pancreatico-splenic nodes to coeliac nodes
- The nerves of the spleen accompany the splenic artery
- Sympathetics from T5-9 go to the coeliac plexus to supply the spleen
- Parasympathetics from Vagus
- The sympathetic fibres cause the vessels to contract, resulting in vasoconstriction
- This mechanism helps to push RBCs stored in the spleen out into the systemic circulation – why haematocrit (ratio of the volume of red blood cells to the total volume of blood) goes up 1-2% after haemorrhage
- The nerves that supply the spleen reach the spleen rapped around the the arteries that supply it (splenic artery)
Why can trauma/infection cause the spleen to rupture?
What can this lead to?
What is the preferred management for splenic injuries?
What structures must be avoided during splenectomy?
How can someone life a healthy life without a spleen?
What does this make them more susceptible to?
- Because the capsule of the spleen is relatively thin, physical injury (Rib fractures, trauma) or a serious infection may cause the spleen to rupture
- This can lead to considerable intraperitoneal haemorrhage
- Splenectomy used to be the expected management but nowadays angiography & embolisation may be the preferred management along with observation & masterly inactivity
- During splenectomy great care must be taken to avoid injuring the tail of the pancreas when ligating the splenic vessels
- A person can live a relatively healthy life without a spleen, because macrophages in the bone marrow and liver can take over most of the spleen’s functions.
- Such a person will be more susceptible to infections
Is the abdominal aorta intraperitoneal or retroperitoneal?
Where does the abdominal aorta begin?
What structure does it sit on?
Where does it descend to?
What does the abdominal bifurcate into?
- The abdominal aorta is primary retroperitoneal – it develops behind and stays behind the peritoneum
- The abdominal aorta begins at the aortic hiatus of the diaphragm at T12 (in the midline)
- It lies on vertebral column and descends to the level of L4
- The abdominal aorta bifurcates into common iliac arteries (slightly left of the midline)
What are the 6 visceral branches of the abdominal aorta?
What are 3 parietal branches of the abdominal aorta?
Which 4 branches are in the midline?
- for midline vessels
- 6 visceral branches of the abdominal aorta (supply the organs):
1) Coeliac trunk* (T12 / L1)
2) Middle suprarenal arteries
3) Superior mesenteric artery* (L1)
4) Renal arteries (L1/2 disk)
5) Testicular or ovarian arteries (L2)
6) Inferior mesenteric artery* (L3) - 3 parietal branches of the abdominal aorta (supply the walls of the abdominal cavity):
1) Inferior phrenic arteries (can be visceral, or parietal, or both)
2) 4x Lumbar arteries
3) Median sacral artery*
Where does the hepatic portal venous system drain blood from?
Where does the systemic venous system drain blood from?
- The hepatic portal venous system drains venous blood from absorptive parts of the GI tract & associated organs to the liver (mainly involved in absorption)
- The systemic venous system drains venous blood from all other organs and tissues into the superior or inferior vena cava
Is the IVC intraperitoneal or retroperitoneal?
What is the role of the IVC?
What is the IVC formed by?
What level does it occur at?
Where does the IVC ascend and pierce the diaphragm?
- The IVC is primary retroperitoneal
- The role of the IVC is to convey blood from the body below the diaphragm to the right atrium of the heart
- The IVC is formed by the union of the common iliac veins behind the right common iliac artery at the level of L5
- The IVC ascends on the right side of the aorta, piercing the central tendon of the diaphragm at T8 (caval opening)
What are tributaries of the IVC?
What are 6 tributaries of the IVC?
What is unique about the 1st and 2nd lumbar veins?
- Tributaries of the IVC are veins that drain into the IVC
- 6 tributaries of the IVC:
1) Hepatic veins
2) Right inferior phrenic vein
3) Right suprarenal vein (left vein drains into the left renal vein or left inferior phrenic vein)
4) Both renal veins
5) Right gonadal vein (left vein drains into the left renal vein)
6) Lumbar veins - 1st-2nd lumbar veins are unique as they drain into both the inferior vena cava and the ascending lumbar veins, which drain azygos and hemiazygos, which drains into the SVC
- This means the 1st and 2nd lumbar veins drain into the IVC and indirectly into the SVC (collateral circulation between SVC and IVC)
What % of blood carried to the liver is from the hepatic portal system?
What 4 places does the hepatic portal system drain venous blood from?
Where is the portal vein formed?
What is it formed by?
Describe 3 steps in the route of the Hepatic portal vein after it forms?
Does the hepatic portal vein have valves?
- The hepatic portal system carries 70% of the blood to the liver
- 4 places does the hepatic portal system drain venous blood from:
1) Between the lower third of the oesophagus and distal half of the anal canal as well
2) Spleen
3) Pancreas
4) Gallbladder (3 accessory organs) - The portal vein is Formed posterior to the neck of the pancreas by the union of the splenic & superior mesenteric veins
- 3 steps in the route of the Hepatic portal vein after it forms:
1) Crosses the 1st (superior) part of the duodenum and enters the lesser omentum
2) Runs cranially in the hepatoduodenal ligament towards the porta hepatis
3) Divides into right & left terminal branches
- Neither hepatic portal vein nor its tributaries have valves inside
What do liver lobules consist of?
What can be found at the corners of lobules?
What does the portal vein supply when it reaches the liver?
What mixes together in the sinusoids of the liver?
How many hepatic veins are there?
- Liver lobules consist of hepatocytes arrange in a hexagon
- At the corners of liver lobules, there are portal triads, which consist of a branch of the portal vein, the hepatic artery proper, and the bile duct
- When the portal vein enters the liver, its branches enter portal triads and supply the sinusoids from which blood passes into the central veins, then the hepatic veins, then the inferior vena cava
- In the sinusoids of the liver, the portal venous blood mixes with oxygenated blood from the hepatic artery proper
- There are 3 hepatic veins: right, middle, and left
What is portal hypertension?
What can it lead to?
- Portal hypertension is elevation of blood pressure in the portal system due to the hepatic portal vein being diminished or blocked
- This can lead to the reversal of blood flow due to there being no valves in the portal venous system
- This results in larger volume of blood flows to anastomotic (collateral) areas, which results in blood going from the hepatic portal system to systemic circulation
- This causes veins to be dilated at sites of porto-systemic anastomosis
Describe the portosystemic anastomosis at the lower third of oesophagus.
What structures will appear if there is portal hypertension here?
- The portosystemic anastomosis at the lower third of the oesophagus:
- The oesophageal branches of the left gastric vein (portal vein) drain the lower third of the oesophagus
- Oesophageal veins draining the middle third of the oesophagus (which drains to the azygos veins, which drains to superior vena cava)
- If there is portal hypertension in this area, oesophageal varices will form
Describe the portosystemic anastomosis half-way down the anal canal.
What structures will appear if there is portal hypertension here?
- The portosystemic anastomosis half-way down the anal canal:
- The superior rectal vein draining the upper half of the anal canal (portal vein)
- The middle & inferior rectal veins (internal iliac & internal pudendal veins, which drain to the inferior vena cava)
- If there is portal hypertension in this area, it will lead to haemorrhoids
Describe the portosystemic anastomosis around the umbilicus.
What structures will appear if there is portal hypertension here?
- The portosystemic anastomosis around the umbilicus:
- Para-umbilical veins (left branch of the portal vein) on the anterior abdominal wall
- Epigastric veins (femoral, external iliac, internal thoracic and axillary veins, which drain into the IVC and SVC)
- If there is portal hypertension in this area, it will lead to caput medusae
Describe the portosystemic anastomosis around the umbilicus.
What structures will appear if there is portal hypertension here?
- The portosystemic anastomosis around the umbilicus:
- Para-umbilical veins (left branch of the portal vein) on the anterior abdominal wall
- Epigastric veins (femoral, external iliac, internal thoracic and axillary veins, which drain into the IVC and SVC)
- If there is portal hypertension in this area, it will lead to caput medusae
Describe the portosystemic anastomosis on the posterior abdominal wall.
- The portosystemic anastomosis on the posterior abdominal wall:
- Veins of secondarily retroperitoneal organs (incl. bare area of liver) (portal vein)
- Veins of body wall (systemic veins)
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