The spleen is an organ situated in the upper part of the abdomen. It plays an important role in immunity and removes damaged and old red blood cells from circulation.

What Is The Embryological Development Of Spleen?

Development of the spleen starts during the fifth week. Spleen develops from mesenchymal cells present between the layers of the dorsal mesogastrium. The mesenchymal cells differentiate and form the following structures:

• Capsule

• Connective tissue of the spleen

• Parenchyma of spleen

In a fetus, the spleen has lobules but before birth, these lobules fuse and disappear. Notches in the superior border of the spleen are the remains of grooves separating these lobules.

What Is The Anatomy Of Spleen?

Location Of Spleen: Spleen Anatomy

Spleen is located in the upper left region of the abdomen (left hypochondrium) behind and to the left of the stomach. It is present under the diaphragm. Medially it is related to the left kidney and tail of the pancreas.

Spleen is protected against external force through the rib cage.

Size Of Spleen: Spleen Anatomy

The size of the spleen is approximately the size of a clenched fist.

The normal dimensions of the spleen are:

• Approximate length is 12 cm

• Thickness is 5 cm

• Width is approximately 7 cm

Structure Of Spleen: Spleen Anatomy

The spleen is an oval-shaped organ surrounded by a thick connective tissue capsule. The capsule divides the organ into lobules by inward extension. Spleen consists of the following structures:

• White pulp (lymphatic tissue)

• Red pulp

White Pulp:

It consists of:

• Lymphoid sheaths containing T-lymphocytes and macrophages.

• Marginal zone separating it from the red pulp. This region is rich in lymphocytes.

• Lymphoid follicles (lymphocytes mainly B-lymphocytes and lymphatic nodules).

Red Pulp:

It consists of:

• Splenic cords (contain macrophages)

• Venous sinuses

Surfaces Of Spleen: Spleen Anatomy

There are two surfaces of the spleen ie: the visceral surface and the diaphragmatic surface.

Visceral surface:

The visceral surface is a concave surface. It is irregular and has impressions for the viscera. Some important impressions are:

• Gastric impression for the greater fundus of the stomach.

• Renal impression for the left kidney.

• Pancreatic impression for the pancreas.

• Colic impression for left colic flexure.

Diaphragmatic surface: Spleen Anatomy

The diaphragmatic surface is smooth and convex. This surface is in contact with the diaphragm and ribs.

Borders Of Spleen: Spleen Anatomy

There are three borders of the spleen. These are:

• Superior border

• Inferior border

• Anterior border

There is a notch at the anterior end of the superior border of the spleen due to its embryological development from the lobule. This notch is used for palpating enlarged spleen by health physicians.

The inferior border of the spleen is rounded.

Poles Of The Spleen: Spleen Anatomy

There are two poles of the spleen. These are:

• Anterior pole

• Posterior pole

Hilum Of The Spleen:

The hilum is the area on the visceral surface of the spleen. The gastrosplenic ligament (attachment between stomach and spleen) attaches to this area. The splenic artery and splenic vein also pass through this area.

Connections And Relations Of Spleen: Spleen Anatomy

Greater omentum:

Greater omentum connects spleen with stomach and kidney.

Gastrosplenic ligament:

A gastrosplenic ligament connects the spleen with the greater curvature of the stomach.

Splenorenal ligament:

A splenorenal ligament connects the spleen with the kidney.

Following are the relations of the spleen with other organs:

Anterior:

The stomach lies anteriorly to the spleen.

Posterior:

Diaphragm left kidney, and rib 9-11 lie posteriorly to the spleen.

Medial:

The left kidney, the tail of the pancreas lie medially to the spleen.

Inferior:

Inferiorly spleen is related to splenic flexure.

Superior:

Superiorly spleen is related to the diaphragm.

What Is The Blood Supply OF Spleen? Spleen Anatomy

A celiac artery has three branches. These are:

• Left gastric artery

• Common hepatic artery

• Splenic artery

The splenic artery (the largest branch of the celiac trunk) mainly supplies blood to the spleen.

What Is The Nerve Supply Of Spleen? Spleen Anatomy

1. Celiac plexus (sympathetic supply)
2. Tenth cranial nerve ie: Vagus nerve (parasympathetic supply)

What Is The Venous Drainage Of Spleen? Spleen Anatomy

The splenic vein is responsible for the venous drainage of the spleen. The splenic vein also receives the drainage of an inferior mesenteric vein. It then combines with the superior mesenteric vein behind the head of the pancreas and forms the hepatic portal vein which then drains into the inferior vena cava.

What Is The Lymphatic Drainage Of Spleen?

Splenic lymph nodes at the hilum are responsible for the lymphatic drainage of the spleen. These nodes drain into celiac lymph nodes which in return drains into cisterna chyli. Cisterna chyli later becomes thoracic duct.

What Are The Major Functions?

The spleen mainly filters blood. Some of the important functions of the spleen are:

• Spleen acts as a site for hematopoiesis (formation of blood cells) until the fifth month of gestation.

• Helps in immunity against infections by activating B and T-lymphocytes and producing IgM and IgG antibodies.

• Plays important role in an immune response against some encapsulated bacterias like Streptococcus pneumonia, Haemophilus influenza, and Neisseria meningitidis.

• Spleen plays important role in the removal of damaged, dead, and old red blood cells by phagocytosis.

• Involved in phagocytosis of bacteria with the help of macrophages.

• Spleen is also responsible for the sequestration of platelets leading to spleen crisis (increased spleen size due to accumulation of blood in spleen and diminished blood count).

• Blood storage is also an important function of the spleen.

• Involved in maintaining the level of body fluids.

What Is Accessory Spleen?

 Accessory spleens are the presence of one or more nodules (splenic masses) away from the main body of the spleen. This condition is benign and does not cause serious complications.

The accessory spleen is also called splenules, splenunculus, or supernumerary spleen.

Accessory spleens may be present in the following areas:

• In peritoneal folds

• Near the hilum of the spleen

• In the gastrosplenic ligament

• In the tail of the pancreas

Cause:

Due to the failure of fusion of splenic lobules during the embryonic period.

Diagnosis:

Scintigraphy (use of radioactive tracer and production of images of organs) is used for the diagnosis of accessory spleen.

What Is Polysplenia?

Polysplenia is the presence of a large number of small accessory spleens without the main body of the spleen rather than one normal spleen.

What Is Asplenia?

Asplenia is the absence of a normal functioning spleen. It may be:

• Congenital

• Acquired

How To Assess The Spleen?

The function and anatomy of the spleen are assessed by these methods:

• Palpation

• Percussion (Castell’s method and Nixon’s method).

Is Normal Spleen Palpable?

In normal daily life, the spleen is not palpable except in young and slender adults. However, in certain medical conditions and diseases spleen becomes enlarged and swollen. In such cases spleen is palpable.

What Are The  Methods To Palpate Spleen?

Classical method:

Palpate the spleen from the right iliac fossa to the left hypochondriac region while the patient is in a supine position. You may feel the notch of spleen on deep inspiration.

Bimanual method:

In this method, the patient is in the right lateral position. The examiner or medical practitioner keeps one hand on the lower chest and palpates the spleen with the other hand.

Hooking method:

In this method, the patient lies down in the right lateral position while the examiner stands on the left side of the patient. Spleen is palpated by hooking fingers over the left costal margin.

Dipping method:

This method is used in the case of ascites. The patient lies down in a supine position. Spleen is palpated like in the classical method while the examiner dips his/her fingers into the abdomen of the patient to displace the fluid.

The manoeuvre of bock us:

If the spleen is not palpable by the above-mentioned methods then this manoeuvre is used. The patient is asked to jump a few times and lie down in a recumbent position and then the spleen is palpated.

What Is Castell’s Sign?

Castell’s sign is a finding used for the assessment of enlarged spleen (splenomegaly). The patient lies down in a supine position and the percussion is done. If the spleen is enlarged, there is dullness to percussion on full inspiration and the dullness disappears on expiration.

What Is The Clinical Significance ?

Spleen is clinically significant because of its important role in immunity against infections. If the function of the spleen is not normal it increases the chances of infectious diseases and reduced immunity.

Splenic rupture:

The rupture of the spleen is a medical emergency requiring immediate treatment otherwise it may lead to serious complications.

Causes:

Following are some common causes of splenic rupture.

• Injury to the left side of the body
• Enlarged spleen
• Trauma (blunt or penetrating)
• Fractured ribs

Symptoms:

Symptoms of the splenic rupture include:

• Pain in abdomen
• Tenderness
• Pain in the left shoulder
• Confusion
• Dizziness
• Lightheadedness

Splenomegaly:

Enlargement of the spleen is called splenomegaly.

Causes:

Some important causes are:

• Viral infections like mononucleosis
• Bacterial infections like endocarditis
• Parasitic infections like malaria
• Leukaemia
• Gaucher disease
• Niemann-Pick’s disease
• Hemolytic anaemia
• Liver cirrhosis
• Hodgkin’s lymphoma

What Is Splenectomy?

Splenectomy is the surgical procedure used to remove the spleen.

Indications:

Important indications of splenectomy include:

• Splenic rupture
• Splenomegaly
• Cancer
• Infections
• Spherocytosis

Complications:

Major complications are:

• Formation of a blood clot
• Pancreatitis
• The collapse of the lungs
• Injury to abdominal organs
• Infection
• Pneumonia