SPLEEN -

INTRODUCTION –

• It is a hemi-lymph organ and belongs to

reticuli – endothelial system .

• 2^nd lymphoid organ
• Pleural cavity seperates spleen and diaphragm from

the ribs.

Largest single mass of lymphoid tissue .

Located in the left hypochondrium , deep to 9,10 & 11 ribs.

It is seprated from the ribs by the diaphragm and the

costodiaphragmatic recess ( space in pleural cavity .)

• The spleen is a small organ inside your left rib cage, just above the stomach. It’s part of the lymphatic system (which is part of the immune system). The spleen stores and filters blood and makes white blood cells that protect you from infection. Many diseases and conditions can affect how the spleen works. A ruptured (torn) spleen can be fatal.
• The spleen is part of lymphatic system (which is part of your immune system). It does several important jobs to keep your body healthy.�Many different conditions, diseases, disorders and injuries affect how your spleen works. Providers usually treat the condition or illness that’s causing problems with the spleen. If necessary, healthcare providers can remove your spleen during a procedure called a splenectomy.

FUNCTION -

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• Spleen forms part of reticuloendothelial system.
• Main function is hematopoesis in fetal life and in adults with reutilizatio

of iron from hemoglobin of destroyed red blood cells .

• It has red snd the white pulp which are sepeated by the marginal sinus.
• No.of nodules develop which soon fuse to form a lobulated spleen.
• Notching of superior border of adult spleen is evidence of its multiple origin.�These nodules which fail to fuse, form accessory spleens.

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Phagocytosis : The spleen is an important component Of the reticuloendothelial system.

• The splenic Phagocytes include:
• The reticular cells and free macrophages of the redPUIP.
• Modified reticular cells of the ellipsoids
• Free macrophages and endothelial cells of theVenous sinusoids
• Surface reticular cells of the lymphatic follicle. ThePhagocytes present in the organ remove cell debrisAnd old and effete RBCs, other blood cells andMicroorganisms, and thus filter the blood
• Phagocytosis of circulating antigens initiatesHumoral and cellular immune responses.

Haemopoesis

Immune response

Storage of RBC

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DEVELOPMENT

Develops from mesenchymal cells in the dorsal

mesogastrium during the fifth week of gestation.

•Red pulp composed sinuses, splenic cord and

marginal zone and main function to filter red blood

cells and reserve monocytes.�•White pulp is composed of malpighian corpuscles

and help in active immune response

Axis of spleen is directed downwards, forwards and laterally.�Axis lies along the 10^th rib.

ACCESSORY SPLEENS/ SPLENUNCULI

These may be found in :-�In derivatives of dorsal mesogastrium.�In broad ligament of uterus.�In the spermatic cord.

Splenunculi, also known as supernumerary spleens, accessory spleens, or splenules, are small nodules of spleen that are separate from the rest of the organ.

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EXTERNAL FEATURES

THE SPLEEN HAS-

• Two ends�Three borders�Two surfaces�Two angles�Hilum

RELATIONS

• Anteriorly : Stomach, tail of pancreas, left colic flexure & left kidney�Posteriorly : Diaphragm, that separates it from the left pleura (left costo- diaphragmatic recess), left lung & 9, 10 & 11 ribs.Left colic flexure.�Medially : Left kidney.
• Inferiorly : Right colic flexure.

MEASUREMENT OF SPLEEN

• Length-12 cm(5 inch)�• Breadth-7cm(3 inch)�• Thickness-3cm (1inch)�• Weight-150gm (7 oz)�• HARRIR’S DICTUM OF ODD NUMBERS ON SPLEEN:1,3,5,7,9,11�• 1inches in thikness,3 inches in breadth, 5 inches in length, 7oz in weight, 9-11 ribs of left side against which spleen rest.

• The spleen, in healthy adult humans, is approximately 7 to 14 centimetres (3 to 5+1⁄2 in) in length.�An easy way to remember the anatomy of the spleen is the 1×3×5×7×9×10×11 rule. The spleen is 1 by 3 by 5 inches (3 by 8 by 13 cm), weighs approximately 7 oz (200 g), and lies between the 9^th and 11^th ribs on the left-hand side and along the axis of the 10^th rib. The weight varies between 1 oz (28 g) and 8 oz (230 g) (standard reference range)

POSITION OF SPLEEN

• The anterior or lateral end :- it is expanded or more like a border.

it is directed downwards forwards and reaches mid axillary line.

• The posterior or medial end :- it is rounded and directed

upwards backwards, medially, and rest on upper pole of left kidney.

• VISCERAL SURFACE :- It is concave and

irregular.

• IT IS RELATED TO:-�FUNDUS OF STOMACH�ANTERIOR SURFACE OF LEFT KIDNEY�THE SPLENIC FLEXURE OF COLON�TAIL OF PANCREAS

SURFACES

• DIAPHRAGMATIC :- This surface is convex and smooth.�IT IS RELATED TO:-�A) Diaphragm�B) Lt lung & Its pleura�C) Costodiaphragmatic recess�d) 9^th, 10^th & 11^th ribs of left side.

BORDERS

The superior border is characteristically notched near the�anterior end.�The inferior border is rounded.�The intermediate border is also rounded and is directed�to the right.

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ANGLES

ANTEROBASAL ANGLE :It is the junction of superior border�with lateral or anterior end. It is the most forward�projecting part of spleen. When spleen is enlarged, this is felt first, so this is called as “clinical angle of spleen.

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POSTETOBASAL ANGLE : Junction of inferior border with�lateral or anterior end of spleen.

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IMPRESSIONS ON VISCERAL SURFACE�

Gastric impression�Renal impression�Colic impression�Pancreatic impression (Tail)

LIGAMENTS

• Gastro –splenic
• Lieno –renal
• Lieno – Phrenic
• Phrenico - colic

Function of ligaments

• Lieno- phrenic : Suspensory ligament of spleen.
• Phrenico –colic :Sustentaculum lienis (supports the spleen from below).�Peritoneal fold extending from It colic flexure to diaphragm
• Gastro-splenic: Connects fundus of stomach to anterior lip of hilum of spleen�Contains short gastric & It gastro-epiploic vessels.�Lieno-renal : Connects ant surface of It kidney with posterior lip of hilum of spleen�Contains tail of pancrease, splenic vessels & nerve.

BLOOD SUPPLY

The tortuous splenic artery arises from the coeliac trunk and runs along the upper border of the body and tail of the pancreas, to which it gives small branches.��The short gastric and left gastroepiploic branches pass between the layers of the gastrosplenic ligament.

�The main splenic artery generally divides into superior and inferior branches, which, in turn, subdivide into several segmental branches.

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The liver receives 20% of its blood supply through the hepatic artery, and 80% through the portal vein

Before entering the liver, both the hepatic artery and the portal vein divide into right and left branches.

Within the liver, they redivide to form segmental vessels which further divide to form interlobular vessels which run in the portal canals. Further ramifications of the interlobular branches open into the hepatic sinusoids.

Thus the hepatic arterial blood mixes with the portal venous blood in the sinusoids. There are no anastomoses between adjoining hepatic arterial territories and hence each branch is an end artery.

ARTERIAL SUPPLY

SPLENIC ARTERY�Largest branch of the celiac artery�Runs a tortuous course along the upper border of the pancreas�Passes within the lienorenal ligament�Divides into 4-5 terminal branches, which enter the spleen at the hilus.

The lack of anastomosis of these arterial vessels within the spleen results in the formation of vascular segments of the spleen with relatively avascular planes between them, enabling subtotal splenectomy.

The spleen is supplied by the splenic artery which is the largest branch of the coeliac

trunk. The artery is tortuous in its course to allow for movements of the spleen. It passes through the lienorenal ligament

,Within the spleen it divides repeatedly to form successfully the straight vessels called penicilli, which further divide into ellipsoids and arterial capillaries. Further course of the blood is controversial.

According to closed theory of splenic circulation, the capillaries are continuous with the venous sinusoids that lie in the red pulp; the sinusoids join together to form veins. However, according to open theory of splenic circulation, the capillaries end by opening into the red pulp from where the blood enters the sinusoids their walls.

Still others believe in a compromise theory, where the circulation is open in distended spleen and closed in contracted spleen. The splenic circulation is adapted for the mechanism of separation and storage of the red blood cells.

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NERVE SUPPLY

• It is predominentaly supplied by the sympathetics from coeliac plexus. The fibers supply the blood vessels and smooth muscle of trabecule. �Sympathetic fibres are derived from the coeliac plexus.�They are vasomotor in nature. They also supply some smooth muscle present in the capsule.
• The spleen is innervated by the splenic plexus, which connects a branch of the celiac ganglia to the vagus nerve.�The underlying central nervous processes coordinating the spleen’s function seem to be embedded into the Hypothalamic-pituitary-adrenal-axis, and the brainstem, especially the subfornical organ.

HISTOLOGY

��Liver is covered by Glisson’s capsule. In the pig there are hexagonal lobules with portal radicles at 3-5 corners. Each radicle contains bile ductule, branch each of portal vein and hepatic artery. Central vein lies in the centre and all around the central vein are the hepatocytes in form of laminae. On one side of the lamina is the sinusoid and on the other side is a bile canaliculus.��Portal lobule seen in human is triangular in shape with three central veins at the sides and portal tract in the centre.

LYMPHATIC DRAINAGE

The splenic lymph nodes lie at the hilum and receive lymph via perivascular and subcapsular lymphatic vessels. It is then drained to the superior pancreatic (pancreaticosplenic) lymph nodes found at the superior surface of the pancreas. From there, the lymph is drained to the celiac lymph nodes.

VENOUS DRAINAGE

The hepatic veins are arranged in two groups, upper and lower. The upper group consists of three large veins right, left and middle, which emerge through the upper part of the groove for the inferior vena cava, and open directly into the vena cava. These veins keep the liver suspended. The lower group consists of a variable number of small veins from the right lobe and the caudate lobe which emerge through the lower part of the caval groove and open into the vena cava. Microscopically the tributaries of hepatic veins, i.e. central veins are seen as separate channels from those of the portal radicles.

CLINICAL IMPORTANCE

Spleen is undercover of thoracic cage and is not palpable�Splenomegaly: enlarged spleen due to cancer, specifically blood-based leukemia.�Asplenia: where the spleen is not present.�• Hyposplenia: reduce splenic functions..

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CLINICAL ANATOMY

• Palpation of spleen
• Splenomegaly
• Splenectomy
• Solenic puncture
• Splenic infraction
• Reffered pain
• Partial splenectomy

Citation

An enlarged spleen is a frequent and important clinical sign. It may be a presenting or dominant feature of a number of primary blood diseases as well as other clinical disorders of different etiology. The splenic structure consisting of the white pulp, the red pulp and intermediate marginal zone together with a complicated splenic blood flow enable the spleen to fulfill its functions: filtration (phagocytosis), immunological function, reservoir of blood and its corpuscules and extramedullary hematopoiesis in certain diseases. Enlargement of the spleen may occur as a result of various pathological conditions. This article is based on the history, physical examination and laboratory routine test results as proposed approach to the differential diagnosis of splenomegaly. Progress and changes in management of blood diseases resulted in reappraisal of indications for splenectomy. Progress in surgery has made it possible to perform splenectomy under videolaparoscopic control avoiding laparotomy.

Brendolan, A., Rosado, M. M., Carsetti, R., Selleri, L., & Dear, T. N. (2007). Development and function of the mammalian spleen. Bioessays, 29(2), 166-177.Dear, T.N., 2007

Abstract-