SN3
SHORT NOTE
5M
★ High-yield
Describe the spleen with its relations, blood supply and functions. Add a note on splenomegaly and splenectomy.
General Features
The spleen is the largest lymphoid organ in the body, lying in the left hypochondrium, an intraperitoneal organ.
| Feature | Detail |
|---|---|
| Size | 1 3 5 inches; 7 ounces; ribs 9 to 11 — the "odd numbers" rule |
| Axis | Along the 10th rib |
| Surfaces | Diaphragmatic (convex) and visceral, with gastric, renal, colic and pancreatic impressions |
| Borders | The superior border is notched — a key diagnostic feature |
Peritoneal Attachments
- Gastrosplenic ligament — contains the short gastric and left gastroepiploic vessels
- Lienorenal (splenorenal) ligament — contains the splenic vessels and the tail of the pancreas
- Both are derived from the dorsal mesogastrium
- The spleen develops in the dorsal mesogastrium, which is why it is a foregut-related organ supplied by the coeliac trunk despite being lymphoid
Blood Supply
- Splenic artery — the largest branch of the coeliac trunk; runs a tortuous course along the upper border of the pancreas
- It is an end artery within the spleen, so segmental infarction occurs
- Splenic vein — runs behind the pancreas and joins the superior mesenteric vein to form the portal vein
- The tortuosity of the artery allows the spleen and stomach to expand without traction
Functions
- Filtration — removes aged and abnormal red cells; the "graveyard of red cells"
- Immunological — antibody production; site of opsonisation; removal of encapsulated organisms
- Haemopoiesis — in fetal life, and in adults in myelofibrosis
- Reservoir — stores platelets (about a third of the total) and blood
- Iron reclamation from degraded haemoglobin
Splenomegaly and its Recognition
| Feature distinguishing spleen from kidney on palpation |
|---|
| Enlarges toward the right iliac fossa, along the axis of the 10th rib |
| Has a notch on its medial border |
| Moves well with respiration |
| One cannot get above it |
| Not ballotable and not bimanually palpable |
| Dull to percussion; there is no band of colonic resonance over it |
- The spleen must enlarge to about three times its size before it is palpable, since it lies deep to the ribs
- Causes in India — malaria, kala-azar, enteric fever, portal hypertension, haemolytic anaemias (thalassaemia), leukaemia and lymphoma
Applied Aspects
- Rupture of the spleen is the commonest serious injury in blunt abdominal trauma; it may be delayed for days as a subcapsular haematoma expands. Blood irritates the diaphragm, giving left shoulder tip pain (Kehr sign)
All questions in Abdomen
- Q1Describe the layers of the anterior abdominal wall and the formation of the rectus sheath. Add a note on the inguinal canal. ★
- Q2Describe the stomach under parts, relations, blood supply, lymphatic drainage and nerve supply. Add a note on its applied anatomy. ★
- Q3Describe the liver under surfaces, lobes, ligaments and blood supply. Add a note on the porta hepatis and hepatic segments. ★
- Q4Describe the peritoneum with its folds, the lesser sac and the peritoneal spaces. Add a note on its nerve supply and applied anatomy. ★
- Q5Describe the kidney under position, coverings, relations and blood supply. Add a note on the ureter and its constrictions. ★
- SN1Describe the formation and tributaries of the portal vein. Add a note on portal hypertension and portosystemic anastomoses. ★
- SN2Describe the positions, blood supply and applied anatomy of the vermiform appendix. ★
- SN3Describe the spleen with its relations, blood supply and functions. Add a note on splenomegaly and splenectomy. ★
- SN4Describe the coeliac trunk with its branches and distribution. ★
- SN5Describe the extrahepatic biliary apparatus. Add a note on Calot's triangle and gallstones. ★
- SN6Describe the inguinal canal with its boundaries, contents and the mechanisms preventing herniation. ★
- SN7Describe the regions and planes of the abdomen. Add a note on the transpyloric plane and surface marking.