9.spleen

Anatomy of Spleen

1. Dr.Arun Naragund Asst.Prof. Dept. of Shareera Rachana Shri J.G.C.H.S. Ayurvedic Medical College, Ghataprabha -591321 spleen

2. The spleen consists of a large encapsulated mass of vascular and lymphoid tissue It is situated in the upper left quadrant of the abdominal cavity between the fundus of the stomach and the diaphragm. Its shape varies from a slightly curved wedge to a ‘domed' tetrahedron. Its long axis lies approximately in the plane of the tenth rib . (45 ˚ with horizontal plane ) Its posterior border is approximately 4 cm from the mid-dorsal line at the level of T 10 Its anterior border usually reaches the mid-axillary line .

3. The size and weight of the spleen vary with age and sex . In the adult it is usually 12 cm long, 7 cm broad, and 3–4 cm wide. It is comparatively largest in the young child Its average adult weight is about 150 g , although the normal range is wide, between 80 g and 300 g, reflecting the amount of blood it contains. the spleen has to be at least three times its normal size before it can be palpated.

4. EXTERNAL FEATURES TWO ENDS : Anterior (EXTRE MITIES/POLES) Posterior THREE BORDERS : Superior Inferior Intermediate TWO SURFACES : Diaphragmatic Visceral

5. The posterior extremity, or superior pole, usually faces the rounded vertebral column. Rests on upper pole of left kidney. The anterior extremity, or inferior pole, is larger, expanded & more like a border . The superior border have one or two notches that have persisted from the lobulated form of the spleen in early fetal life The inferior border is more blunt and rounded than the superior border and corresponds in position to the lower margin of the eleventh rib The intermediate border is rounded & directed to right.

6. The diaphragmatic surface is convex and smooth and faces mostly superiorly and laterally . The diaphragmatic surface is related to left dome of the diaphragm which separates it from the basal pleura, the lower lobe of the left lung and the 9-11 left ribs The visceral surface faces inferomedially with impressions . The gastric impression is broad ,concave It is separated from the stomach by a peritoneal recess. The renal impression is slightly concave by the left kidney & left suprarenal gland . The colic impression lies at the inferior pole ,and is usually flat. The pancreatic impression is often small The hilum of the spleen is a long fissure pierced by splenic artery and vein ,nerves and lymphatics enter and leave the spleen.

7. SPLEEN: PERITONEAL RELATIONS The spleen is almost entirely covered by peritoneum that adheres firmly to its capsule, and is separated from the stomach and left kidney by recesses of the greater sac The splenorenal ( lienorenal ) ligament is formed from two layers of peritoneum. The anterior layer & The posterio layer. The splenic vessels lie between the layers of the splenorenal ligament: T he tail of the pancreas is usually present in its lower portion.

8. The gastrosplenic ligament also has two layers. The posterior layer is at the splenic hilum and over the posterior aspect of the stomach. The anterior layer reaches the greater curvature of the stomach anteriorly. The short gastric and left gastroepiploic branches of the splenic artery pass between its layers. The phrenicocolic ligament extends from the splenic flexure to the diaphragm at the level of the eleventh rib. It is continuous with the peritoneum of the lateral end of the transverse mesocolon

9. VASCULAR SUPPLY The spleen is supplied exclusively from the splenic artery. This is the largest branch of the coeliac axis and its course is among the most tortuous in the body, above the superior border of the pancreas and descend to lie behind the gland . The splenic artery runs in the splenorenal ligament posterior to the tail of the pancreas . It divides into two or three main branches before entering the hilum of the spleen. As these branches enter the hilum they divide further into four or five segmental arteries that each supply a segment of the splenic tissue. The splenic artery gives off various branches to the pancreas in its course and gives off short gastric arteries to the stomach just prior to dividing or from its terminal branches.

10. SPLENIC VEIN The splenic vein is formed within the splenorenal ligament, close to the tip of the tail of the pancreas, by five or six tributaries that emerge from the hilum of the spleen. The tributaries are thin walled and often spread over several centimetres because the hilum is long and thin The splenic vein runs in the splenorenal ligament below the splenic artery. It receives numerous short tributaries from the pancreas. It ends behind the neck of the pancreas, where it joins the superior mesenteric vein to form the portal vein. The short gastric and left gastro- epiploic veins drain into it.

11. INNERVATION The spleen is innervated by the splenic plexus , which consists of branches of the coeliac plexus , left coeliac ganglion and right vagus that accompany the splenic artery. S ympathetic activity causes an increase in the ‘fast' circulation of the spleen as opposed to slow filtration. Referred pain The sensation of pain arising from the pulp of the spleen is poorly localized and referred to the central epigastrium, as is the case for other structures derived from the foregut. Distension of the splenic capsule stretches the parietal layers of the peritoneum and produces pain that is localized to the posterior left upper quadrant.

12. MICROSTRUCTURE The spleen is essentially concerned with phagocytosis and immunity . In the fetus it is also an important site of haemopoiesis . In spleenectomy functions are assumed by the liver and by other lymphoid tissues .

13. Microscopically, the parenchymal tissue of the spleen consists of two major components, white pulp and red pulp. The white pulp is composed of lymphoid tissue in which B and T lymphocytes mature and proliferate under antigenic stimulation. The red pulp is a unique filtration device that enables the spleen to clear particulate material from the blood as it perfuses the spleen. It is composed of a complex system of interconnected spaces populated by large numbers of phagocytic macrophages that remove effete red blood cells, microorganisms, cellular debris and other particulate matter from the circulation.

14. S pleenic Artery Spleenic vein White Pulp RED PULP Venous sinus Splenic cord Central Artery TRABECULA CAPSULE

15. Fibrous framework of the spleen

16. Splenic microcirculation The segmental splenic arteries enter the hilum and ramify in the trabeculae throughout the organ. The splenic veins are similar in number to the arterial branches. Small arteries tapering to arterioles pass through the white pulp then turn abruptly to form penicillar branches which, after a course of approximately 0.5 mm, pass out of the white pulp into the marginal zone and red pulp. The passage of blood through the vascular compartments between the arterioles and splenic veins is referred to collectively as the intermediate circulation of the spleen. Ultimately , blood is passed to the venous sinusoids from which it enters venules leading to small veins that run within trabeculae , and thence into larger veins that drain the spleen at its hilum Open and closed splenic circulations

17. THANK YOU