- Arteries and veins are the main blood vessels.
- Have thick walls to withstand the pressure of the blood and a small lumen
- Carry blood from heart to different organs.
- Do not have valves
- Carry oxygenated blood to the whole body except pulmonary artery.
- Situated deeper in the tissues
- Have thinner walls and a large lumen.
- Carry blood from organs towards the heart.
- Have valves to prevent the back flow of blood.
- Carry deoxygenated blood to the lungs except pulmonary vein.
- Situated superficially.
Capillaries: Have extremely thin walled and very narrow lumen. They do not have valves Blood flows with low pressure. Allow exchange of gases food materials and waste. Capillaries join together to form venules then they join to form veins.
Lymphatic system is an open circulatory system. It consists of lymphatic capillaries Lymphatic vessels, lymph nodes and lymphatic organs. Lymph flows in one direction only i.e. from tissue to heart.
Capillaries have very fine pores through which blood plasma filters out and starts flowing into the inter cellular spaces. This fluid is called extracellular fluid. A part of this fluid enters into the lymph capillaries. The fluid inside the lymph capillaries is called lymph. Lymph is yellow fluid which contains blood plasma minus blood proteins.
Lymph enters into lymph capillaries which join together to form large lymph vessels The lymph vessels finally drains lymph into large veins.
Functions of lymph
- It takes up excess fluid that has diffused out from the blood capillaries and puts it into blood.
- It has lymphocytes which fight against germs and bacteria and produce antibodies to fight against infections.
- It absorbs and carries digested fats from the intestine.