Platelets (Thrombocytes) Blood Plasma (55%) Platelets (Thrombocytes) Blood cells

90% water, 10% chemicals, slightly alkaline What is blood plasma? 90% water, 10% chemicals, slightly alkaline pH 7.4. Transports chemicals and heat around the body What sort of chemicals? Important molecules such as glucose Waste products Mineral salts Hormones Plasma proteins Respiratory gases

Blood cells

Red and white blood cells

Red Blood cells: Erythrocytes They have no organelles including a nucleus to leave more room for haemoglobin. Large surface area due their bi-concave disc shape. This allows O2 to diffuse quickly into and out of the cell They have an elastic membrane which allows them to squeeze through small blood capillaries, then spring back into normal shape when they re-enter veins

White Blood Cells: Leucocytes These are larger than red blood cells but there are fewer of them in the blood. They are responsible for fighting disease. There are three different white blood cells for you to remember.

phagocytes: Monocytes & Neutrophils These white blood cells engulf pathogens and microorganisms and digest them (phagocytosis ). A non specific process which occurs whatever the infection. They have an elongated nucleus and a flowing cytoplasm – this enables them to squeeze through gaps between cells to move to the site of infection in body tissues Their cytoplasm contains many lysosomes to aid digestion Monocytes =Agranulocyte (non granular cytoplasm. Neutrophil = Granulocyte (granular cytoplasm)

Lymphocytes (Agranulocytes) Act against microorganisms, with some lymphocytes secreting antibodies (a range of glycoproteins) that between them immobilise and kill microorganisms and make them ready for phagocytes to engulf. Large nucleus. These white blood cells are specific. Each type of lymphocyte acts against one particular pathogen. They provide long term immunity to future infections.