What are lymph Nodes? What is function of lymph nodes?

There several definations available on Internet Some of them are listed below.
Definitions of Lymph Nodes:
1. small bean-shaped structures scattered along the vessels of the lymphatic system. The lymph nodes filter out or remove waste, bacteria, and cancer cells that may travel through the lymphatic system.

2. Small pearl-like glands that are connected to the lymph system and filter out stray bacteria or cancer cells. They also produce lymphocytes which are one of the types of white blood cells in the body. When bacteria or cancer cells reach these nodes they can become enlarged.

3. Normal, round, raisin to grape-sized collections of lymphocytes (white blood cells) found throughout the body. Lymph nodes are connected to each other by lymphatic vessels. They normally help fight infection, but also are one of the first sites to which cancers spread. In general, the spread of cancer to lymph nodes portends a worse prognosis for the patient. There are exceptions to this.
4. part of the lymphatic system; a thin, clear fluid that circulates through the lymphatic vessels and carries blood cells that fight infection and disease.


There are several places in the body where lymph nodes are strategically located for immunological purposes. These include areas such as the neck, groin, axillae, mediastinum, and abdominal cavities because antigens, or foreign pathogens, are commonly encountered in these places. We are probably most familiar with the lymph nodes located in our neck area. These lymph nodes commonly swell up and are detectable by touch when we have a sore throat. You can feel them under chin as two tender lumps on your neck just below you jaw bone. Or perhaps you have had your tonsils removed these too are lymph nodes.

Functions of Lymph Nodes:

1. Defense functions--filtration and phagocytosis
2. Hematopoiesis

Tonsils
Masses of lymphoid tissue located in a protective ring under mucous membranes in the mouth and back of the throat. It Helps to protect against bacteria that may invade tissues in the area around the openings between the oral and nasal cavities. Palatine tonsils--located on each side of the throat.

Thymus
In an unpaired organ consisting of two pyramid-shaped lobes with delicate and finely lobulated surfaces. Is located in the mediastinum, extending up into the neck as far as the lower edge of the thyroid and inferiorly as far as the fourth intercostal cartilage.

Spleen
Located in the left hypochondrium directly below the diaphragm, above the left kidney and descending colon, and behind the fundus of the stomach.

Functions of the Spleen
Defense :As blood passes through the sinusoids, reticuloendothelial cell (macrophages) lining these venous spaces remove microorganisms from the blood and destroy them by phagocytosis.
Hematopoiesis :Monocytes and lymphocytes complete their development to become activated in the spleen. Before birth, red blood cells are also formed in the spleen.
Red blood cell and platelet destruction. :Macrophages lining the spleen's sinusoids remove worn-out red blood cells and imperfect platelets from the blood and destroy them by phagocytosis.
Also break apart the hemoglobin molecules from the destroyed red blood cells and salvage their iron and globin content by returning them to the blood stream for storage in bone marrow and liver.
Blood reservoir : Pulp of the spleen and its venous sinuses store considerable blood which can be released during hemorrhage.