Formation of the Interstitial Fluid
When blood flows from arteries into capillaries, there is higher hydrostatic pressure at the arterial end of the capillaries. This high pressure forces some fluid out through the capillary walls into the intercellular spaces between the cells. Once the fluid leaves the capillary walls, it is called interstitial or tissue fluid. Interstitial fluid is similar in composition to blood plasma but it has no erythrocytes, platelets or large protein molecules as these are too large to pass through the capillary walls.
Importance of the Interstitial Fluid
Interstitial fluid is important because it forms the internal environment of the body. It bathes the cells and supplies them with their requirements. Oxygen and nutrients diffuse from the blood through the interstitial fluid and into the cells. Excretory waste products, such as carbon dioxide and urea, diffuse out of the cells into the interstitial fluid. The internal environment of the body is kept within a normal range by homeostatic processes.
Fate of the Interstitial Fluid
Approximately 90% of the interstitial fluid flows back into the venous end of the capillary system where the hydrostatic pressure is low. The remaining 10% of the interstitial fluid enters the lymphatic capillaries and is called lymph. If excess interstitial fluid is unable to return to the blood circulatory system, it will accumulate and cause tissue swelling. This condition is called oedema.
Structure of the Lymphatic System
Lymph is the colourless fluid found in the lymphatic vessels. Lymph is similar in composition to blood plasma but has no erythrocytes, platelets or large protein molecules. Lymph contains a higher number of lymphocytes than blood. Lymph travels through the lymphatic vessels by the contraction of the surrounding skeletal muscles. The lymph flows in one direction. One end of the vessels is closed and back flow is prevented by valves present in the larger vessels. The smaller lymphatic vessels join form larger vessels.
When blood flows from arteries into capillaries, there is higher hydrostatic pressure at the arterial end of the capillaries. This high pressure forces some fluid out through the capillary walls into the intercellular spaces between the cells. Once the fluid leaves the capillary walls, it is called interstitial or tissue fluid. Interstitial fluid is similar in composition to blood plasma but it has no erythrocytes, platelets or large protein molecules as these are too large to pass through the capillary walls.
Importance of the Interstitial Fluid
Interstitial fluid is important because it forms the internal environment of the body. It bathes the cells and supplies them with their requirements. Oxygen and nutrients diffuse from the blood through the interstitial fluid and into the cells. Excretory waste products, such as carbon dioxide and urea, diffuse out of the cells into the interstitial fluid. The internal environment of the body is kept within a normal range by homeostatic processes.
Fate of the Interstitial Fluid
Approximately 90% of the interstitial fluid flows back into the venous end of the capillary system where the hydrostatic pressure is low. The remaining 10% of the interstitial fluid enters the lymphatic capillaries and is called lymph. If excess interstitial fluid is unable to return to the blood circulatory system, it will accumulate and cause tissue swelling. This condition is called oedema.
Structure of the Lymphatic System
Lymph is the colourless fluid found in the lymphatic vessels. Lymph is similar in composition to blood plasma but has no erythrocytes, platelets or large protein molecules. Lymph contains a higher number of lymphocytes than blood. Lymph travels through the lymphatic vessels by the contraction of the surrounding skeletal muscles. The lymph flows in one direction. One end of the vessels is closed and back flow is prevented by valves present in the larger vessels. The smaller lymphatic vessels join form larger vessels.
The vessels from the left side of the body, the alimentary canal and the right side of the lower part of the body flow into the thoracic duct. The thoracic duct is the largest lymphatic vessel in the body. It carries lymph to the left subclavian vein and back into the bloodstream. The right lymphatic duct transports lymph from the right side of the head and chest into the right subclavian vein. Lymph nodes are mainly found in the neck, armpits and the groin. The lymphatic system consists of a network of lymphatic capillaries, lymphatic vessels, lymph nodes and certain organs such as the thymus gland, spleen and tonsils.
Role of the Lymphatic System in Transport
The lymphatic system collects the interstitial fluid and returns it to the circulatory system. Lacteals are lymphatic capillaries in the villi of the ileum. They absorb fats and fat-soluble vitamins and transport them to the blood circulatory system. The lymph nodes filter out bacteria and other foreign particles. Phagocytes present in the nodes engulf and destroy these foreign particles. Lymphocytes in the lymphatic tissues produce antibodies which aid in the destruction of pathogens and the neutralisation of toxins.
Role of the Lymphatic System in Transport
The lymphatic system collects the interstitial fluid and returns it to the circulatory system. Lacteals are lymphatic capillaries in the villi of the ileum. They absorb fats and fat-soluble vitamins and transport them to the blood circulatory system. The lymph nodes filter out bacteria and other foreign particles. Phagocytes present in the nodes engulf and destroy these foreign particles. Lymphocytes in the lymphatic tissues produce antibodies which aid in the destruction of pathogens and the neutralisation of toxins.
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