Biology - Topic 4

Blood and Circulation

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Your heart

Your heart is a hollow sac of muscle, if you are at rest your heart beats about 60-80 times per minute, forcing blood through a network of blood vessels.

Blood vessels carry blood to and from your blood cells.

Blood :-

Blood tissue is made out of sevreal different types of cells floating in a clear liquid called PLASMA.

The plasma carries many dissolved chemicals around your body.

Blood group - these are determine by your genes.

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Blood

System for moving molecules : -

All living things need a way of moving - small organism can rely on diffusion.

eg. Single cells Amoeba - it is small enough for diffusion to transport subtances in and out of the cell.

Diffusion is a slow process so larger organisms need special transport systems, in most animals this is a circulatory system.

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The Human circulatory system : -

Human have about 5 and 7 litres of blood circulating around your body. It contains cells floating in a pale yellow fluid called plasma.

Plasma is mainly water, carries a wide range of dissolved materials including food molecules, hormones, and waste products from cells, also helps to distrubute heat around the body.

Three types of cells floating in the plasma : -

- red blood cells - to transport oxygen

- white blood cells - to fight infection

- platets - which play an important role in blood clotting at an injury site.

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Red blood cells

RBC are packed with the protein haemoglobin, it binds oxygen as blood passes through the lungs, the oxygen is released from haemoglobin as blood circulates through the tissue of the body.

RBC have no nucleas - more space

The biconcave shape - more surface area

- means that oxygen can diffuse in and out of cells more rapidly, gives flexiability to squeeze through capileries, which are one cells wide.

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White Blood cells

WBC - they protect your body from infection by disease causing microogransims.

- produce antibodies - englulf & digest micro-organisms by phagocyctis.

Platets -

- fragments of cells made from cytoplasm of large cell, when blood vessels are damaged - send out chemicals which trigger a series of reaction that form clot at the cut site, helps the loss of blood.

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The ABO blood types

Every cell carries markers on the outside.

- called Antigens

Antigens are WBC use to detect foreign cells, if detected they produce antibodies to destroy it.

RBC can carry two different antigens - A and B - determines your ABO blood type.

-Just A antigens - Blood type A

-Just B antigens - Blood type B

- both A and B antigens - Blood type AB

- neither type of antigen - Blood type O

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