Circulatory System Intro

• ​Explain why humans need a transport system

• List substances that are transported around the human body.

• List the components of blood

​Transport systems are important to move substances around the bodies of organisms.

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In humans there is a constant exchange of substances with their environment and this is done by the cardiovascular system and lymphatic system.

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​These systems are of importance as:

• Simple diffusion is not adequate as most of the body is too far from the surface for substances to move through.

• Humans have a small surface area to volume ratio. Diffusion through the body surface is not adequate to supply all the body cells with the necessary requirements and remove waste.

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​Some of the substances transported around the body include:

• Useful substances: oxygen, water, digested food materials like glucose and amino acids, hormones and antibodies

• Waste substances: carbon dioxide and nitrogenous waste e.g urea

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​The cardiovascular system (circulatory system) is made up of:

• Blood (medium used to transport substances around the body)

• Blood vessels (tubes through which blood flows to and from all parts of the body)

• The Heart (pumps the blood through the blood vessels)

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Blood is pumped around the cardiovascular system by the heart exchanging substances with the surrounding tissues. Blood is the only liquid tissue.

Blood is composed of three types of cells suspended in a fluid called plasma. These three cells are:

Red Blood Cells, White Blood Cells and Platelets.