What is the lymphatic system, write down its structure and function?
LYMPHATIC SYSTEM:
Definition:
(That system which consists of tissue fluid its transport and regulates the substances in body)
This system is responsible for the transport and returning of materials from the tissues of the body to the blood.
The system comprises of:
- Lymph capillaries,
- Lymph vessels,
- Lymph nodes, and
- Lymphoid masses,
- Lymph-the fluid which flows in the system.
(1) Lymph Capillaries:
Lymph capillaries end blindly in the body tissues, whore pressure from the accumulation of interstitial fluid or extracellular fluid forces the fluid into the lymph capillaries.
(2) Lymph and Lymph Vessels:
When this fluid enters the lymph capillaries, it is called lymph.
The lymph vessels empty in veins;
So lymph is a fluid in transit between interstitial fluid and the blood.
The intercellular spaces in the walls of lymph vessels are larger than those of the capillaries of blood vascular system.
So large molecules, from the interstitial fluid cal also enter the lymph capillaries.
Thoracic Lymph Vessel and Subclavin Vein:
Lymph capillaries join to form larger and larger lymph vessels; and ultimately from thoracic lymph duct-which opens into subclavian vein.
Direction of Flow:
The flow of lymph is always towards the thoracic duct.
Lacteals:
In the intestine, the branches of lymph capillaries, within villi, are called lacteals.
(i) Activity of skeletal muscles,
(ii) Movement of viscera (internal organs)
(iii) Breathing movements.
(iv) Valves, which prevent back flow of lymph.
(3) Lymph Nodes:
Along the pathway, the lymph vessels, have, at certain points, masses of connective tissue where lymphocytes are present, these are lymph nodes. Several afferent lymph vessels enter a lymph node, which is drained by a single, efferent lymph vessel.
Location:
Lymph nodes are present in the:
(i) Neck Region.
(ii) Axilla (armpit) and.
(iii) Groin (genitalia) of humans.
(4) Lymphoid Masses:
In addition, several lymphoid masses are present in the:
(i) Walls of the digestive tract,
(ii) In the Mucosa and Sub-mucosa
The larger masses are:
(i) Spleen
(ii) Thymus
(iii) Tonsils (tissue mass in mouth) and
(iv) Adenoids (throat tissue) are all lymphoid masses.
These produce lymphocytes.
(5) Functions:
These are several functions performed by the lymphatic system.
(i) Regulation of Blood Volume:
In an average person, about three litres more fluid leaves the blood capillaries than is reabsorbed by them each day.
It returns this excess fluid and its dissolved proteins and other substances to the blood.
(ii) Absorption of Lipids:
The lacteals of villi absorb large fat globules, which are released by interstitial cells after the products of digestion of fats are absorbed.
(iii) Defence Mechanism:
The lymphatic system helps defend the body against foreign invaders.
Lymph nodes have lymphocytes and macrophages that destroy the bacteria and viruses.
The painful swelling of lymph nodes in certain diseases (mumps is an extreme example) is largely a result of the accumulation of dead lymphocytes and macrophages.
(iv) Filtering Blood Destroyed aged RBC and Invaders:
Just as the lymph nodes filter lymph, the spleen filters blood, exposing it to macrophages and lymphocytes that destroy foreign particles and aged red blood cells.
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