Lymphatic System

10.7

Human Lymphatic System

The Formation of Tissue Fluid

Blood that reaches the arterial end of the blood capillary has a high pressure due to the small diameter of capillaries and the pumping force of the heart.
This pressure allows the blood plasma to diffuse continuously from the blood capillaries to the intercellular space.
Blood plasma that occupies the intercellular space and constantly bathes cells is called tissue fluid.
The tissue fluid does not contain any erythrocyte, platelet and plasma protein because these are too large to diffuse out of the blood capillaries.
Tissue fluid allows the exchange of materials in the blood and cells to occur.
Nutrients and oxygen diffuse from tissue fluid to body cells.
Simultaneously, excretory products and carbon dioxide diffuse from body cells to blood capillaries through the tissue fluid.

Lymph Formation and Components of The Lymphatic System

At the venule end of the blood capillary, blood plasma is hypertonic compared to the tissue fluid surrounding it.
Blood pressure is also lower.
As a result, the reabsorption of water, mineral salts and waste takes place in the venule capillary.
However, only 85% of the fluid that leaves the blood at the arteriole end of blood capillary diffuses back into the venule end.
The remaining 15% of the fluids forms about 4 litres of fluid that is lost from capillaries each day.
This lost fluid is collected and returned to the blood through the lymphatic capillary, which is the smallesr vessel in the lymphatic system.
This fluid is known as lymph and is pale yellow in colour.
The lymphatic capillary wall consists of one layer of cells only.
The lymphatic capillary differs from blood capillary because one of its end is blocked or closed while the other end is connected to the lymphatic vessel.
Lymphatic capillaries found in intercellular spaces merge to form a larger lymphatic vessel.
Along the lymphatic vessel, there are lymph nodes at certain distances.
The lymphatic system consists of organs such as lymph nodes, spleen, thymus gland, bone marrow, tonsils and appendix.
The lymphatic system does not have its own pump to circulate the lymph along the lymphatic vessel.
The flow of lymph is aided by heartbeat pulse, contraction of skeletal muscles, peristalsis in the digestive tract and changes in pressure during inhalation and exhalation of breath.
In the lymphatic vessel, one-way valves ensure the lymph flows continuously to the heart. These valves also prevent the lymph from flowing back.

Relationship between The Blood Circulatory System and The Lymphatic System

All lymphatic vessels will eventually join with one of the two main lymphatic vessels which are the thoracic duct dan right lymphatic duct.
The right lymphatic duct receives lymph from the right hand, chest and right side of the head and neck.
The thoracic duct receives lymph from the left side of the head, neck and chest, and all the body parts below the ribs.
The thoracic duct will deliver its contents into the left subclavian vein while the right lymphatic duct will transport lymph into the right subclavian vein.
So the lymph collected from the whole body will flow back into the blood circulatory system.

The Necessity of The Lymphatic System

Body Defence

Lymph nodes produce and store lymphocytes that are involved in the production of antibodies.

Complements The Blood Circulatory System

The lymphatic system returns the excess tissue fluid in the intercellular space into the blood flow.
The composition, pressure and volume of blood are maintained at a normal range.

Transportation of Fat-Soluble Substances

Fats and fat-soluble substances diffuse into the lacteal in the villus of the small intestine.
Lacteals are lymphatic capillaries.
Lipid droplets are transported to the thoracic duct and blood circulatory system through the left subclavian vein.

Lymphatic System

10.7

Human Lymphatic System

The Formation of Tissue Fluid

Blood that reaches the arterial end of the blood capillary has a high pressure due to the small diameter of capillaries and the pumping force of the heart.
This pressure allows the blood plasma to diffuse continuously from the blood capillaries to the intercellular space.
Blood plasma that occupies the intercellular space and constantly bathes cells is called tissue fluid.
The tissue fluid does not contain any erythrocyte, platelet and plasma protein because these are too large to diffuse out of the blood capillaries.
Tissue fluid allows the exchange of materials in the blood and cells to occur.
Nutrients and oxygen diffuse from tissue fluid to body cells.
Simultaneously, excretory products and carbon dioxide diffuse from body cells to blood capillaries through the tissue fluid.

Lymph Formation and Components of The Lymphatic System

At the venule end of the blood capillary, blood plasma is hypertonic compared to the tissue fluid surrounding it.
Blood pressure is also lower.
As a result, the reabsorption of water, mineral salts and waste takes place in the venule capillary.
However, only 85% of the fluid that leaves the blood at the arteriole end of blood capillary diffuses back into the venule end.
The remaining 15% of the fluids forms about 4 litres of fluid that is lost from capillaries each day.
This lost fluid is collected and returned to the blood through the lymphatic capillary, which is the smallesr vessel in the lymphatic system.
This fluid is known as lymph and is pale yellow in colour.
The lymphatic capillary wall consists of one layer of cells only.
The lymphatic capillary differs from blood capillary because one of its end is blocked or closed while the other end is connected to the lymphatic vessel.
Lymphatic capillaries found in intercellular spaces merge to form a larger lymphatic vessel.
Along the lymphatic vessel, there are lymph nodes at certain distances.
The lymphatic system consists of organs such as lymph nodes, spleen, thymus gland, bone marrow, tonsils and appendix.
The lymphatic system does not have its own pump to circulate the lymph along the lymphatic vessel.
The flow of lymph is aided by heartbeat pulse, contraction of skeletal muscles, peristalsis in the digestive tract and changes in pressure during inhalation and exhalation of breath.
In the lymphatic vessel, one-way valves ensure the lymph flows continuously to the heart. These valves also prevent the lymph from flowing back.

Relationship between The Blood Circulatory System and The Lymphatic System

All lymphatic vessels will eventually join with one of the two main lymphatic vessels which are the thoracic duct dan right lymphatic duct.
The right lymphatic duct receives lymph from the right hand, chest and right side of the head and neck.
The thoracic duct receives lymph from the left side of the head, neck and chest, and all the body parts below the ribs.
The thoracic duct will deliver its contents into the left subclavian vein while the right lymphatic duct will transport lymph into the right subclavian vein.
So the lymph collected from the whole body will flow back into the blood circulatory system.

The Necessity of The Lymphatic System

Body Defence

Lymph nodes produce and store lymphocytes that are involved in the production of antibodies.

Complements The Blood Circulatory System

The lymphatic system returns the excess tissue fluid in the intercellular space into the blood flow.
The composition, pressure and volume of blood are maintained at a normal range.

Transportation of Fat-Soluble Substances

Fats and fat-soluble substances diffuse into the lacteal in the villus of the small intestine.
Lacteals are lymphatic capillaries.
Lipid droplets are transported to the thoracic duct and blood circulatory system through the left subclavian vein.

Lymphatic System

Lymphatic System

Chapter : Transportation in Humans and Animals

Topic : Lymphatic System of Humans

Related notes