The Lymphatic System: A
Comprehensive Overview
Lymphatic System
Functions of the Lymphatic System
The lymphatic system consists of lymphatic vessels, lymphoid tissues, and
lymphoid organs. It serves the following key functions:
Transports fluids that have escaped from the blood vascular system
back to the blood.
Transports absorbed fats from the intestines to the blood.
Houses phagocytic cells and lymphocytes that contribute to the body's
defense and resistance against diseases.
Formation of Lymph
Blood pressure in the arterial end of blood capillaries pushes fluid
(water, small molecules like sugars, salts, oxygen, urea) through the
capillary wall, forming the interstitial fluid.
Blood cells and proteins are too large to pass through the capillary
wall, remaining in the capillaries and causing an increase in blood
osmolarity.
The resulting osmotic gradient pulls water into the blood capillary by
osmosis near the venous end.
Approximately 85% of the fluid that leaves the blood at the arterial end
re-enters the blood at the venous end, while the remaining 15% enters
the lymphatic capillary, forming the lymph.
Comparison of the composition of blood, interstitial fluid, and lymph:
| Component | Blood | Interstitial Fluid | Lymph | | --- | --- | --- | --- | | Red
blood cells | Present | Absent | Absent | | White blood cells | Present | Absent
| Present | | Protein | Present | Absent | Absent | | Lipid | Present | Absent |
Present |
Lymphatic Pathway
Lymphatic vessels form a one-way system, with lymph flowing towards
the heart.
Lymph is transported from lymph capillaries → larger lymphatic vessels
→ lymphatic ducts → blood vessels near the heart.
There are two main lymphatic ducts:
Right lymphatic duct: Drains lymph from the right arm and right side of
the head and thorax into the right subclavian vein.
Thoracic duct: Drains lymph from the rest of the body into the left
subclavian vein.
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