BLOOD and CIRCULATION

Blood By the end of the lesson you should be able to: State the composition of Blood State the function of red blood cells and plasma Explain the function of haemoglobin in the transport of oxygen State the function of white blood cell

Blood the average human has 5 litres of blood it is a transporting fluid it carries vital substances to all parts of the body Blood is thicker than water and has a bit of a salty taste.

The components of the blood and their jobs

centrifuge

Blood Composition Plasma: Serum and Fibrin Buffy Coat: White Blood Cells Red Blood Cells

What is blood made up of? Red blood cells White blood cells Platelets Plasma Breakdown products of digestion, such as glucose, fatty acids and amino acids Dissolved mineral salts Carbon dioxide Urea hormones

Blood cells are created in the bone marrow, which is the sponge-like material in the center of bones.

Plasma

Plasma is the liquid part of the blood Plasma transports – blood cells, soluble food molecules, waste products, hormones, antibodies, clotting proteins Plasma is a straw-yellow coloured liquid It makes about 55% of total blood volume if everything in plasma was removed, plasma would look like this:

Red Blood Cells (RBCs / erythrocytes)

Red blood cells specialisations 1) biconcave shape 2) no nucleus  extra space inside 3) contain haemoglobin  the oxygen carrying molecule  250million molecules / cell 4) It is the most abundant cell in the blood (40-45% total blood vol. 5) Survives an average of 120 days increases the surface area so more oxygen can be carried

Haemoglobin gives red blood cells their colour can carry up to 4 molecules of O2 associates and dissociates with O2 contains iron

Function of Haemoglobin When there is a high concentration of oxygen e.g in the alveoli haemoglobin combines with oxygen to form oxyhaemoglobin. When the blood reaches the tissue which have a low concentration of oxygen the haemoglobin dissociates with the oxygen and the oxygen is released into body tissues

White blood cells (WBC’s /Leukocytes)

Cells of the immune system involved in defending the body against both infectious disease and foreign agents –Body’s Defence mechanism Much larger than the RBC’s Fewer in number Nucleus present 4000 – 13000 per mm3 Two types – Phagocytes and Lymphocytes

Platelets/Thrombocytes

What do platelets do? if you get cut:- platelets produce tiny fibrin threads these form a web-like mesh that traps blood cells. These harden forming a clot, or "scab." This is useful for stopping bleeding, and for preventing germs from entering the body through the cut. 150,000 to 400,000 per mm3