Blood Pressure

The force that blood exerts against the wall of the vessel is called blood pressure.

Blood pressure is of two types.

(i) Systolic blood pressure

(ii) Diastolic blood pressure

Blood pressure is measured with an instrument called sphygmomanometer. High blood pressure is also called hypertension and is caused by constriction of arterioles which results in increased resistance to blood flow. It can lead to rupture of an artery and internal bleeding.

1.0Heart Beat 

• The heart shows regular contraction and relaxation. The rhythmic contraction followed by expansion constitutes a heartbeat. 

• In a child, the heartbeat varies from 90 to 100 times per minute. In an adult, heartbeat varies from 70-72 times per minute. When we do some physical activity like exercise, running, jogging, our heart beat increases.

• The instrument used to listen to the heartbeat is known as a stethoscope.

2.0Lymphatic System

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 tissues to heart. Lymph is also called white vascular connective tissue.

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 a transparent fluid which contains blood plasma except blood proteins, RBC and platelets.

Lymph enters into lymph capillaries which join together to form large lymph vessels. The lymph vessels finally drains lymph into large veins.

The lymphatic nodes occur at intervals in the course of lymphatic vessels. It contains lymphocytes, plasma cells and macrophages. The lymph/tissue fluid filters through the lymphatic nodes. The macrophages remove microorganisms, cellular debris and foreign particles.

Note :

• Lymphocyte is a type of WBC which fights infection and disease-causing organisms.
• Macrophages are specialized cells which are involved in detection, phagocytosis and destruction of harmful organisms.

Functions of Lymph

(i) It takes up excess fluid that has diffused out from the blood capillaries and puts it into blood.

(ii) It has lymphocytes which fight against germs and bacteria and produce antibodies to fight against infections.

(iii) It absorbs and carries digested fats from the intestine serving as a middle man between blood and body.

3.0Also Read