The Lymphatic System Flashcards
What is the lymphatic system?
It is a one-way system of dead-ending vessels. It is a secondary circulatory system
What do lymph vessels do?
Collect the fluid that surrounds each cell in the body and returns it to the blood
What are lymph nodes?
They are swellings in the lymph vessels. Lymph nodes help fight infection in the body. They contain large numbers of white blood cells [lymphocytes] with many channels though which lymph flows.
Formation of lymph
Blood in the arteries are under high pressure than blood in the veins. This causes some of the fluid and small proteins to be forced out of blood plasma in capillaries at the arteriole side. This fluid is called tissue fluid, it surrounds all the cells of the body.
What is tissue fluid?
The solution surrounding cells. It is similar to plasma except it does not have red blood cells or platelets and has small amounts of white blood cells and proteins. It acts as an exchange medium whereby materials entering or leaving cells just pass through it
Is tissue fluid continuously being formed
Yes, about one litre and hour is produced.
What must happen to the tissue fluid to prevent swelling
It must be removed and returned to the blood. This prevents swelling from developing in the tissues
What is swelling known as?
Oedema
Tissue fluid is drained away by two routes
90% of it is drawn back into plasma in the capillaries near the veins. This occurs by osmosis and is helped by the reduced blood pressure in the veins
10% of the fluid enters dead-ending tubes called lymph vessels [or lymphatics]. The fluid is now called lymph. Lymph contains large amounts of white blood cells, proteins and fats
Where are lymph vessels found?
Throughout the body.
How does lymph move?
Contraction of skeletal muscles squeeze the lymph vessels and push lymph along.
Semi-lunar valves stop the back flow of lymph
Gravity causes lymph to flow downwards
How are the two main vessels formed? [ducts]
Smaller lymph vessels join together to form two main vessels : the thoracic duct on the left side of the body, and the right lymphatic duct at the right shoulder
What do the ducts do?
They empty lymph into the bloodstream at the subclavian veins located near the collar bones at the shoulders
Where would you find lymph nodes?
Tonsils, spleen, neck, grown and armpits
What are the functions of the lymphatic system?
Drains excess tissue fluid and returns it to blood
Transports fats [lipids] and fat-soluble vitamins [these are absorbed into lacteals in the small intestine]
Defends the body against disease
Part of the immune system. Lymph nodes filter bacteria.
