Spleen and the Portal and Venous System Flashcards
What is the largest lymphoid organ in the body?
The spleen
Where is the spleen located in adults?
- Just posterior to stomach
- Against diaphragm
- Between ribs 8(9)-11 on the left side
What are the functions of the spleen?
- Removal of blood-borne antigens
- Removal and destruction of aged or defective blood cells
- Storing blood platelets and RBC
- Haematopoiesis in the fetus (-> 5 months in utero)
What makes the spleen similar to a lymph node but also different in its function?
- Lymph nodes filter the lymph
- Spleen filters the blood
The area over Labbe’s triangle becomes dull on percussion as a result of what?
Splenomegaly
What is the spleen derived from?
Mesoderm
How is the spleen related to the peritoneal cavity?
Intraperitoneal except hilum
What is the spleen related to?
- Colon (left colic flexure)
- Stomach
- Left kidney
What is the spleen surrounded by?
Fibrous capsule from which trabeculae extend inward
What is the superior surface of the spleen like?
Serrated (if you can feel notches likely to be enlarged spleen)
What are the 2 main areas of the spleen?
- Where venous sinuses are
- Pulp
What is the diameter of the average erythrocyte?
8 microns
How large is the distal end of the trabecular meshwork?
3 microns (eryhtrocytes can squezze through it)
What are the 2 sections of the pulp in the spleen?
- White pulp (purple areas) contain WBCs
- Red pulp (surround white pulp and store erythrocytes and removes old ones)
When are the stored RBCs of the spleen released into the bloodstream?
During exercise
What does sympathetic innervation of the spleen result in?
- Causes trabecular meshwork and spleen to contract expelling RBCs into venous sinuses and systemic circulation
What is the end product of perforin?
Bilirubin
What is the spleen connected to the stomach by?
Gastroplenic (gastrolienal) ligament
What does the gastrosplenic ligament contain?
- Left gastroepiploic and short gastric vessels
- May contain accessory spleen
What is the is the spleen connected to the posterior abdominal wall by?
Splenorenal ligament
What does the splenorenal ligament contain?
Splenic vessels and tail of the pancreas
What is the anterior border of the epiploic foramen?
Hepatoduodenal ligament
What is the gastrosplenic ligament a remnant of?
Dorsal mesentary
Where does the splenic artery run from?
Along the upper border of the pancreas
What does the splenic artery divide into?
Branches that enter the spleen at the hilum
What is the venous drainage of the spleen?
- Splenic vein runs along the tail and body of pancreas
- Receives short gastric and left gastro-epiploic veins
- Behind the neck of the pancreas, joins the superior mesenteric vein to form the hepatic portal vein
What is the lymphatic drainage of the spleen?
- Splenic hilar lymph nodes ->pancreatico-splenic nodes -> coeliac nodes
What is the nerve supply of the spleen?
- The nerves accompany the splenic artery
- Sympathetics from T5-9 -> coeliac plexus
- Para from vagus
What 3 veins make up the hepatic portal system?
- Supeior mesenteric
- Splenic
- Inferior mesenteric
What does the hepatic portal vein drain?
- Lower 1/3 of oesophagus
- Distal half of anal canal as well as spleen, pancreas + gallbladder
Where is the hepatic portal vein formed?
- Posterior to the neck of the pancreas
- Crosses the 1st superior part of the duodenum and enters the lesser omentum
What does the hepatic portal vein divide into?
Right and left terminal branches
Do the hepatic portal veins have valves?
No, nor do its tributaries
What percent of blood to the liver is carried by the portal vein?
70%, 30% is arterial
What lobe does blood from the superior mesenteric vein primarily go to?
- Right lobe
- Blood from inferior mesenteric and splenic vein go primarily to left caudate and quadrate lobes
What are hepatic lobules?
Building block of the liver tissue, consisting of a portal triad, hepatocytes arranged in linear cords between a capillary network, and a central vein
What is the portal triad?
- Component of hepatic lobule
- Found in 6 corners of hepatic lobules
- Branch of portal vein
- Branch of hepatic artery proper
- Bile canaliculi
Where does blood drain from hepatocytes?
- Central veins
- > Hepatic veins
- > Inferior Vena Cava
What can porto-systemic anastomoses also be known as?
Porto-caval anstomoses
Where can porto-systemic anastomoses be found?
- Lower 1/3 of oesophagus
- Halfway down anal canal
- Around umbilicus - Para-umbilical veins + epigastric veins
- Post. abdominal wall - behind ascending and descending colon - secondary retroperitoneal organs - not as large
What can increased flow through porto-systemic anastomoses cause?`
- Oesophageal varices
- Haemorrhoids (piles)
- Caput medusae
What parts of the colon are scondarily retroperitoneal?
- Ascending and descending colons have mesentaries
What can the prehaptic causes of portal hypertension be?
- Portal vein thrombosis
- Splenic vein thrombosis
What can the hepatic causes of portal hypertension be?
- Hepatic tumours (benign, malignant or metstatic)
- Cirrhosis (alcohol abuse, hepatitis, etc.)
- Parasitic infestations (e.g schistosomiasis)
What can the posthepatic causes of portal hypertension be?
- Cardiac disease (severe tricuspid stenosis, restrictive cardiomyopathy, constrictive pericarditis)
- Hepatic vein thrombosis
- Inferior vena cava thrombosis
What can haemorrhoids be due to?
- Portal hypertension
- Obesity
- Pregnancy
- Sedentary life
Where is the abdominal aorta located, where does it runs from?
- Retroperitoneal
- Begins in aortic hiatus of the diaphragm at T12 (in the midline)
- Lies on the vertebral column and descends to the level of L4
- Bifurcates into common iliac arteries (slightly left of the midline)
What are the visceral branches of the abdominal aorta?
- Coeliac trunk (T12/L1)
- Middle suprarenal arteries
- Superior mesenteric artery (L1)
- Renal arteries (L1/2)
- Testicular or ovarian arteries (L2)
- Inferior mesenteric arteries (L3)
What are the parietal branches of the abdominal aorta?
- Inferior phrenic arteries
- 4x Lumbar arteries
- Median sacral artery
Where is the Inferior Vena Cava located in relation to the peritoneum?
Retroperitoneal
What is the Inferior vena cava formed by and where?
- Union of the common iliac veins
- Behind right common iliac artery
- At the level of L5
What veins drain into the Inferior Vena Cava?
- Hepatic veins
- Right inferior phrenic vein
- Right suprarenal vein (left vein drains into the left renal vein or left inf. phrenic vein)
- Both renal veins
- Right gonadal vein (left vein drains into left renal vein)
- Lumbar veins
Veins of origin: 2 common iliacs and median sacral vein
What do the 1st and 2nd lumbar veins drain into?
- IVC
- + Ascending lumbar veins -> azygos and hemiazygos
