Importance of Spleen

 What is spleen and what is importance of Spleen?

Spleen

The oval spleen is the largest single mass of lymphatic tissue in

the body, measuring about 12 cm (5 in.) in length .It is located in the left hypochondriac region between the stomach and diaphragm. The superior surface of the spleen is smooth and

convex and conforms to the concave surface of the diaphragm.

Neighboring organs make indentations in the visceral surface of

the spleen—the gastric impression (stomach), the renal impres-

sion (left kidney), and the colic impression (left colic flexure of

large intestine). Like lymph nodes, the spleen has a hilum.

Through it pass the splenic artery, splenic vein, and efferent lymphatic vessels.

 A capsule of dense connective tissue surrounds the spleen and

is covered in turn by a serous membrane, the visceral peritoneum.

Trabeculae extend inward from the capsule. The capsule plus tra-

beculae, reticular fibers, and fibroblasts constitute the stroma of

the spleen; the parenchyma of the spleen consists of two different

kinds of tissue called white pulp and red pulp .

White pulp is lymphatic tissue, consisting mostly of lymphocytes

and macrophages arranged around branches of the splenic artery

called central arteries. The red pulp consists of blood-filled

venous sinuses and cords of splenic tissue called splenic cords or

Billroth’s cords. Splenic cords consist of red blood cells, macro-

phages, lymphocytes, plasma cells, and granulocytes. Veins are

closely associated with the red pulp.

 Blood flowing into the spleen through the splenic artery enters

the central arteries of the white pulp. Within the white pulp, B

cells and T cells carry out immune functions, similar to lymph

nodes, while spleen macrophages destroy blood-borne pathogens

by phagocytosis. Within the red pulp, the spleen performs three

functions related to blood cells: (1) removal by macrophages of  

ruptured, worn out, or defective blood cells and platelets; (2) stor-

age of platelets, up to one-third of the body’s supply; and (3) pro-

duction of blood cells (hemopoiesis) during fetal life.

The spleen is the organ most often damaged in cases of abdominal trauma. Severe blows over the inferior left chest or superior abdomen can fracture the protecting ribs. Such crushing injury may result in a ruptured spleen, which causes significant hemorrhage and shock. Prompt removal of the spleen, called a splenectomy (sple¯-NEK-to¯-me¯), is needed to prevent death due tol bleeding. Other structures, particularly red bone marrow and the liver, can take over some functions normally carried out by the

spleen. Immune functions, however, decrease in the absence of a

spleen. The spleen’s absence also places the patient at higher risk for

sepsis (a blood infection) due to loss of the filtering and phagocytic

functions of the spleen. To reduce the risk of sepsis, patients who

have undergone a splenectomy take prophylactic (preventive) anti-

biotics before any invasive procedures. 

Lymphatic Nodules

Lymphatic nodules (follicles) are egg-shaped masses of lym-

phatic tissue that are not surrounded by a capsule. Because they

are scattered throughout the lamina propria (connective tissue) of

mucous membranes lining the gastrointestinal, urinary, and repro-

ductive tracts and the respiratory airways, lymphatic nodules in

these areas are also referred to as mucosa-associated lymphatic

tissue (MALT).

 Although many lymphatic nodules are small and solitary,

some occur in multiple large aggregations in specific parts of

the body. Among these are the tonsils in the pharyngeal region

and the aggregated lymphatic follicles (Peyer’s patches) in the

ileum of the small intestine. Aggregations of lymphatic nodules

also occur in the appendix. Usually there are five tonsils, which

form a ring at the junction of the oral cavity and oropharynx

and at the junction of the nasal cavity and nasopharynx  The tonsils are strategically positioned to participate

destroy others by immune responses. The filtered lymph then

leaves the other end of the lymph node. Since there are many

 afferent lymphatic vessels that bring lymph into a lymph node

and only one or two efferent lymphatic vessels that transport

lymph out of a lymph node, the slow flow of lymph within the

lymph nodes allows additional time for lymph to be filtered. Addi-

tionally, all lymph flows through multiple lymph nodes on its path

through the lymph vessels. This exposes the lymph to multiple

filtering events before returning to the blood.

Spleen

The oval spleen is the largest single mass of lymphatic tissue in

the body, measuring about 12 cm (5 in.) in length .

It is located in the left hypochondriac region between the stomach

and diaphragm. The superior surface of the spleen is smooth and

convex and conforms to the concave surface of the diaphragm.

Neighboring organs make indentations in the visceral surface of

the spleen—the gastric impression (stomach), the renal impres-

sion (left kidney), and the colic impression (left colic flexure of

large intestine). Like lymph nodes, the spleen has a hilum.

Through it pass the splenic artery, splenic vein, and efferent lym-

phatic vessels.

 A capsule of dense connective tissue surrounds the spleen and

is covered in turn by a serous membrane, the visceral peritoneum.

Trabeculae extend inward from the capsule. The capsule plus tra-

beculae, reticular fibers, and fibroblasts constitute the stroma of

the spleen; the parenchyma of the spleen consists of two different

kinds of tissue called white pulp and red pulp .

White pulp is lymphatic tissue, consisting mostly of lymphocytes

and macrophages arranged around branches of the splenic artery

called central arteries. The red pulp consists of blood-filled

venous sinuses and cords of splenic tissue called splenic cords or

Billroth’s cords. Splenic cords consist of red blood cells, macro-

phages, lymphocytes, plasma cells, and granulocytes. Veins are

closely associated with the red pulp.

 Blood flowing into the spleen through the splenic artery enters

the central arteries of the white pulp. Within the white pulp, B

cells and T cells carry out immune functions, similar to lymph

nodes, while spleen macrophages destroy blood-borne pathogens

by phagocytosis. Within the red pulp, the spleen performs three

functions related to blood cells: (1) removal by macrophages of

Metastasis (me-TAS-ta-sis; meta- -

 beyond; -stasis -

 to

stand), the spread of a disease from one part of the body to

another, can occur via lymphatic vessels. All malignant tumors even-

tually metastasize. Cancer cells may travel in the blood or lymph and

establish new tumors where they lodge. When metastasis occurs via

lymphatic vessels, secondary tumor sites can be predicted according

to the direction of lymph flow from the primary tumor site. Cancerous

lymph nodes feel enlarged, firm, nontender, and fixed to underlying

structures. By contrast, most lymph nodes that are enlarged due to

an infection are softer, tender, and movable. 

Metastasis through

Lymphatic Vessels

The spleen is the organ most often damaged in cases of ab-

dominal trauma. Severe blows over the inferior left chest or

superior abdomen can fracture the protecting ribs. Such

crushing injury may result in a ruptured spleen, which causes sig-

nificant hemorrhage and shock. Prompt removal of the spleen, called

a splenectomy (sple¯-NEK-to¯-me¯), is needed to prevent death due to

bleeding. Other structures, particularly red bone marrow and the

liver, can take over some functions normally carried out by the

spleen. Immune functions, however, decrease in the absence of a

spleen. The spleen’s absence also places the patient at higher risk for

sepsis (a blood infection) due to loss of the filtering and phagocytic

functions of the spleen. To reduce the risk of sepsis, patients who

have undergone a splenectomy take prophylactic (preventive) anti-

biotics before any invasive procedures. 

  Ruptured Spleen

Tonsillitis is an infection or inflammation of the tonsils. Most

often, it is caused by a virus, but it may also be caused by the

same bacteria that cause strep throat. The principal symptom

of tonsillitis is a sore throat. Additionally, fever, swollen lymph nodes,

nasal congestion, difficulty in swallowing, and headache may also

occur. Tonsillitis of viral origin usually resolves on its own. Bacterial

tonsillitis is typically treated with antibiotics. 

Tonsillectomy (ton-si-

LEK-to¯-me¯; ectomy -

 incision), the removal of a tonsil, may be indi-

cated for individuals who do not respond to other treatments. Such

individuals usually have tonsillitis lasting for more than 3 months

(despite medication), obstructed air pathways, and difficulty in swal-

lowing and talking. It appears that tonsillectomy does not interfere

with a person’s response to subsequent infections.