LYMPHATIC SYSTEM

The part of plasma which filters into the spaces among the tissues and flows in vessels similar to arteries and veins constitute the lymphatic system.

The lymph is clear colourless tissue fluid. The vessels that convey lymph are called lymphatic vessels. Lymph is very much like the plasma of the blood but it lacks the plasma protein whose molecules are too large to pass through the capillary walls. The lymph is different from the blood by the absence of the red blood cells that are also too large and are not amoeboid to be able to squeeze themselves through the capillary walls. The lymph is fluid plasma with dissolved mineral salts, nutrients and white blood cells. The lymph can also coagulate but very slowly. The vessels in which the lymph flows are called lymphatic vessels. The lymphatic vessels also divided and subdivided to form lymphatic capillaries like those of the blood vessels. The lymph is rich in oxygen, nutrients and other useful substances. It fills all the spaces between the cells as tissue fluid. When cells have removed all the oxygen and food substances and discharge carbon (IV) oxide and nitrogenous waste into it, it now moves toward the heart through lymphatic capillaries to the major lymphatic vessels.

The lymphatic vessels contain valves like those of the blood vessels. The lymphatic vessels have some swellings along their courses which are called lymph nodes or lymph glands. They produce lymphocytes (white blood cells) which are phagocytes. During infection, lymph nodes filter out bacteria from tissue fluid and pass them on to the lymphocytes which engulf and digest them. The lymph which contains plasma plus waste, lymphocytes and fats picked up from the villi of the small intestine flows into the large lymphatic vessels towards the heart. The lymph flows very slowly and is assisted by muscular contraction and the valves which prevent backward flow. These major lymphatic vessels empty into the left and right subclavian veins which finally take blood into the right atrium.

 

Return of lymph to the blood circulation

The lymph of the head, neck and right arm drain into a large vessel called right lymphatic duct which opens into a large blood called right subclavian vein.The lymph from the right lymphatic duct is therefore emptied into right subclavian vein. The lymphatic vessels (lymphatics) from other parts of the body empty their lymph into the thoracic duct. The thoracic duct in turn empties its lymph into the left subclavian.

The right and left subclavian veins return blood to the right atrium.

 

Functions of the lymphatic system

1. The lymphatic system collects the fluid which has diffused out from blood capillaries and returns it to the blood stream.
2. It removes excretory products from the cells. If the lymph vessels are unable to drain the body fluid efficiently, water is retained in the body causing swelling of the body (dropsy). Standing on one spot for a long time without movement may result in swollen ankles due to collection of lymph.
3. It removes foreign bodies from the cells.
4. It collects fatty acids from the lacteals in the villi of the small intestine and passes them into the blood.
5. It produces white blood cells which help to fight pathogenic organisms invading the body.
6. The lymph glands filter out bacteria from body fluid thereby stopping the spread of such infection.

 

Tissue fluid

Tissue fluid is produced at the arterial end of the capillaries. The high blood of the artery forces fluid out of thin walls of the capillaries into the spaces between the tissue cells is known as tissue fluid.

This issue fluid contains glucose, amino acids, oxygen and waste products but no fat droplets and protein molecules. Since their molecules are too large to pass through the thin capillary walls. The tissue cells absorb oxygen, glucose and amino acids by diffusion and use them for metabolic activities. Waste products resulting from metabolic activities are passed into the tissue fluid.

At the venous and of the capillaries, some fluid containing carbon (IV) oxide and waste products enter the venous capillaries and are taken into the main blood stream.

The remaining fluid filters into lymph capillaries to become lymph.

 

Pulse

The heart contracts to pump blood into arteries for circulation to all parts of the body. The force with which the blood is pushed into arteries causes the arteries to expand in order to accommodate the volume of the blood rushing through. This expansion of the arteries is called the pulse. The pulse can be felt by feeling the artery over a bone in the wrist. The pulse corresponds with the contraction of the heart. The pulse is felt in successions and the rate at which one follows the other is measured and expressed as pulse rate. Pulse rate can be normal, rapid or slow. Pulse rate varies among individuals of different ages, sizes of the body and state of health.

 

Different pulse rates

Fast pulse rate

A very rapid pulse rate may be caused by:

1. Fear.
2. Rigorous muscular activities.
3. Fever.
4. Heart disease.
5. Over secretion from the thyroid gland.
6. Over weight in very fat individuals.

 

Low pulse rate

A very low pulse rate may be caused by:

1. Heart disease.
2. Injuries or diseases of the brain.
3. Old age.

 

Blood pressure

The heart contracts to force blood into the arteries.Theforce is considerably high enough to make the walls of the arteries fully stretched all the time. This force exerted by the blood against the arterial wall is called blood pressure. The resistance put on by the arterial walls by exerting a similar pressure on the blood propels the blood forwards towards the capillaries. The pressure however gets reduced proportionately with distance from the heart and so considerably less or low in the venules and veins.

Blood pressure is maintained by the force of the heart’s contraction and the elasticity of the arterial walls. It is this pressure that makes blood to flow in jets or spurts when an artery is cut in a wound. The diminished pressure in the capillaries and veins makes blood to ooze or flow gently when a vein is cut in a wound.

 

High blood pressure

Blood pressure is measured by an instrument called sphygmomanometer. Average values have been worked out by medical scientists. A persistent deviation from the average value to the high side is diagnosed as high blood pressure, popularly called high BP.

 

Causes

1. Diseases of the kidneys.
2. Nervous trouble.
3. Disease of the walls of the blood vessels.

 

Anaemia

Anaemia is not shortage of blood or lack of blood as it is commonly believed. It is the shortage of red blood cells or in some forms lack of haemoglobin in the red blood cells so that the red blood cells are not able to carry sufficient oxygen to the cells for respiration.

 

Causes

1. Severe bleeding leading to loss of large volume of blood (involving numerous red blood cells).
2. Infection by malaria parasites (Plasmodium) blood fluke (Schistosoma) and Trypanosoma resulting in the attacking and destroying of large number of red blood cells.
3. Malnutrition – low intake of food containing essential nutrients such as iron and proteins leading to poor quality of protoplasm and haemoglobin.
4. Injuries or damages done to the bone marrow where red blood cells are manufactured reduce the number of the red blood cells in the blood.

 

Remedies

1. Give balanced diet which will supply enough proteins for normal growth and iron for the formation of haemoglobin.
2. Include green leafy vegetables in most meals.
3. Give a lot of fruit juices which supply mineral salts and vitamins for healthy growth and rich blood.
4. Treat all diseases causing loss of blood.