The cardiovascular system includes the heart, blood vessels and blood. All these are involved in essential functions of the body such as circulation of oxygen, nutrients, hormones, fluids and ions to the cells. It also removes the metabolic wastes and oxygen from the cells. Major loss of blood, called hemorrhage, is life-threatening.

The cardiovascular system helps in the transport of the oxygen from the alveoli in the lungs to the heart as it is carried in the blood. The heart then pumps the oxygenated blood to respiring cells around the body. In exchange, carbon dioxide moves from the body to the alveoli for removal via blood. This transport is done by the hemoglobin present in the red blood cells.

The nutrients are absorbed in the blood circulation from the small intestine. They are transported to different cells of the body for use in the production of the energy and other necessary molecules.

Hormones are released from the endocrine glands into the blood, and they move in the blood to reach their target cells, tissues or organs. For example, insulin is released from the pancreas and is moved around the body affecting all cells.

Fluids, ions and waste travel in the blood and reach the kidney. They help to regulate the amount of material and water excreted in the urine. For example, the waste product urea moves through the blood to reach the kidney for excretion in the urine.

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Key Points

• The blood in the circulatory system helps in the transport of oxygen and carbon dioxide between the lungs (alveoli) and the cells of the body.

• The blood transports the nutrients absorbed from the digested food in the small intestine to the cells of the body.

• The hormones released from the endocrine glands reach the target sites via blood.

• The metabolic waste, ions and fluid move to the kidney via blood.

Key Terms

hemorrhage: major loss of blood

alveoli: air-filled, minute sacs in the lungs

urea: a waste metabolite primarily composed of nitrogen that is disposed of in the kidneys

insulin: a hormone released from the pancreas to control sugar levels

hormones: chemical messengers carried by the blood

cardiovascular system: the collective term for all the organs such as the heart, blood vessels and blood

hemoglobin: an iron centred protein in the blood that binds oxygen