The lymphatic system or Lymphoid System Anatomy and physiology; is a network of tissues, vessels and organs that work together to move a colorless, watery fluid called lymph back into your circulatory system (our bloodstream). It is a part of immune system and complementary to the circulatory system.  Around 20 liters of plasma flow through your body's arteries and smaller arteriole blood vessels and capillaries per day.

Lymphoid System Anatomy and Physiology

Lymphoid system anatomy and physiology; A channel of network of vessels, ducts & trunks that removes the interstitial fluid from the body tissues and return it the blood. It drains fluid ,called lymph. The main roles of the lymphatic system is managing the fluid levels in the body.

lymphatic system

Lymphoid system consists of :

1. Lymph
2. Lymphatic vessels: Lymphatic ducts and capillaries
3. Lymph nodes
4. Lymphatic organs :

• Spleen
• Thymus gland
• Appendix
• Tonsils

LYMPH (CHYLE)

Lymph is consider a part of the interstitial fluid, which lies in the interstices of all body cells and tissues. This fluid becomes lymph when it enters in  lymph capillaries, then travels to at least one lymph node before emptying into the right or left subclavian vein, where it mixed back with blood.
Lymph returns proteins and excess interstitial fluid back to the circulatory system. Lymph brings the bacteria to the lymph nodes to be destroyed. It removes dead cells and helps in immunity. It also helps in absorption of fat in intestine.

Key points :

1. Lymph or chyle is derived from plasma and becomes colorless fluid which contains mainly blood cells except RBCs.
2. The main function of the lymph is to maintain interstitial fluid volume.
3. It also helps in absorption of fat in intestine.
4. Lymph is the most common route of cancer cell spread (metastasis).
5. It also removes dead cells and helps in immunity.

The main function of the lymph is to maintain interstitial fluid volume. 

LYMPHATIC VESSELS

Lymphatic capillaries are blind ended capillaries which drain interstitial fluid. They form lymphatic ducts which finally empty lymph into the veins. Lymphatic vessels contain valves to prevent backflow. There are two main lymphatic ducts:

1. Thoracic duct (45 cm long)

• It begins at the Cisterna chyli in the abdominal cavity.
• Cisterna chyli is a small bag like structure present near the abdominal aorta.
• It drains into the left subclavian vein.

2. Right lymphatic duct (1cm long)

• It drains from right side of the head, neck, chest and right upper limb.
• It drains into the right subclavian vein.

LYMPH NODES

A lymph node is a mini ball-shaped organ of the immune system which is widely distributed throughout the body & linked by lymphatic vessels.
Lymph nodes also have clinical significance. When infection triggers, it becomes enlarged in various conditions, such as a throat infections to life-threatening such as cancers.

Structure of lymph node :

• Fibrous capsule: outermost
• Outer cortex: contains B lymphocytes
• Inner medulla: contains T lymphocytes

Function of lymph node :
 Lymph node consists of T-lymphocyte and B-lymphocyte which fight against infections and protect our body.

LYMPHOID ORGANS

1. Spleen

• Weight: 200 gm. It lies left to the stomach.

• It is the largest lymphatic organ.

• Spleen is commonly injured during road traffic accidents.

• It is also called the 'Blood bank of the body' and 'Graveyard of RBC'.

Functions of spleen

• Phagocytosis and filtration of old, abnormal RBC.

• Formation of RBC in the foetal life.

• Storage of blood, so it is also called " BLOOD BANK"

• Splenectomy is the surgical removal of the spleen.

2. Thymus gland

• It is present in front of heart.

• It secretes hormone Thymosin which is responsible for maturation of T lymphocytes.

• Size of thymus increases till puberty then decreases afterwards.

• Thymus gland in bird is related to migration.

3. Tonsils

1. They are lymphoid tissues around the pharynx. Three types of tonsils are found:

• a. Palatine tonsil
• b. Pharyngeal tonsil
• c. Lingual tonsil
• d. Tubal tonsil

Types of tonsils

2. These tonsils form a ring called Waldeyer's ring.
3. Pharyngeal tonsils are called adenoids.
4. Tonsillectomy is done if these tonsils are enlarged.

4. Peyer's patches

• Aggregate of lymphatic tissue present in ileum

• Affected in Typhoid.

5. Appendix

• It is a part of large intestine. It is a vestigial organ but it also has aggregate of lymphatic tissue that helps in immunity.

• It is about 10 cm long and 7-8 mm in diameter.

• Commonest position of appendix in retrocaecal.

• Inflammation of appendix is called Appendicitis which is a medical emergency that requires immediate treatments.

DISEASES OF LYMPHATIC SYSTEM

1. Lymphangitis: Inflammation of lymphatic vessels
2. Lymphadenopathy: any disease process affecting lymph nodes
3. Lymphadenitis: inflammation of lymph nodes
4. Splenomegaly: Enlargement of spleen (e.g. Kala-azar, Malaria, Typhoid etc.)
5. Splenectomy: Removal of spleen
6. Lymphagiovarix: Dilatation of lymph vessels
7. Lymphorragea: Rupture of lymph vessels
8. Chyluria: Presence of chyle (lymph) in urine

Lymphoid System

Elephantiasis (Filariasis)              Filariasis in details...click here

• It is caused by Wucheria bancrofti, a nematode.

• It is transmitted by the bite of female Culex fatigans, a mosquito.

• In this disease the adult worm obstruct the lymphatic vessels and cause leg swelling, scrotal swelling etc.

• Treatment: the drugs used are DEC (Diethyl carbamazine), Albendazole and Ivermectin.

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