Page 93 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

10. Circulation and Excretion

Chapter in a Nutshell

v All living organisms need oxygen, food and water for survival. These also need to be
transported to different parts of the body. Waste also needs to be expelled.
v The circulatory system is responsible for the transportation of oxygen, food, water and

waste in and outside the human body.
v The circulatory system is made up of the heart & blood vessels that carry blood to different

parts of the body.
v The main parts of the circulatory system are blood, blood vessels and heart.

v Blood is the red fluid which flows in our body through the blood vessels. It has several vital
functions.

v Blood carries oxygen & digested food to all body parts, transports hormones, waste material
to the kidneys which is then expelled as urine. It also helps in blood clothing which prevents
excessive blood loss. It also helps in regulating the body temperature. WBCs in the blood

protects the body from diseases.
v Blood consists of–Red blood cells (RBCs), white blood cells (WBCs), platelets and plasma.

v RBSs carry oxygen from lungs to all body parts. They contain a red-coloured pigment that
imparts red colour to the blood.
v RBCs are also known as erythrocytes. They are made in the inside part of bones called the

bone marrow.
v WBCs are the soldiers of the body as they help fight against diseases. They are also called

leucocytes.
v Some of the WBCs are constantly formed in the bone marrow and some in other parts of

the body.
v Platelets are also called thrombocytes that help in blood clotting. These are also made by

the bone marrow.
v Plasma is the pale or straw-coloured fluid which contains 90% water, proteins & inorganic
salts.

v Blood vessels are tube-like structures which transport blood throughout our body. Blood
vessels are of three types–arteries, veins and capillaries.

v Arteries carry oxygenated blood away from the heart to all the parts of the body.
v Aorta is the main artery. Pulmonary artery carries carbon dioxide-rich blood from the heart

to the lungs.

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