1. Blood Chapter 14

2. Composition • Blood consists of plasma, red cells and white cells • Plasma • Liquid component of blood • Contains proteins e.g. antibodies • Contains soluble food e.g. amino acids, glucose • - these are carried by the plasma into capillaries near cells • Also contains carbon dioxide and wastes • Carbon dioxide is carried as bicarbonate • - this stops dissolved CO2 decreasing the blood pH

3. composition • Red Blood Cells • -Very small and numerous (5.5 million/ml of blood) • Have a biconcave shape • - provides a larger surface area • Small and flexible • - can easily squeeze through narrow capillaries • Cytoplasm is rich in haemoglobin • Cell has no nucleus (not a proper cell)

4. haemoglobin • A respiratory pigment that combines with oxygen • Vastly increases the oxygen carrying capacity of the blood • Haemoglobin has a high affinity for oxygen when oxygen concentration is high • - the oxygen will readily associate with the haemoglobin • Haemoglobin has a low affinity for oxygen when oxygen levels concentration is low • oxygen will readily dissociate from the haemoglobin • Haemoglobin combined with oxygen is called oxyhaemoglobin • Oxygen concentration is also called oxygen tension - measured in kilopascals (kPa) • An oxygen dissociation curve shows the relationship between haemoglobin and oxygen

5. White blood cells • Less numerous (4000-13,000 per ml of blood) • Defend the body from infection by microbes • Contain nuclei & can change shape • 2 types: monocytes & lymphocytes • Defend the body in two ways: • Phagocytosis • Specific Immune Response (antibodies)

6. phagocytosis • Where bacteria are engulfed and destroyed by phagocytic cells (white blood cells) • A non-specific response – only gives general protection • Carried out by monocytes/macrophages • - these are found throughout the connective tissue in the body • - and in the liver, spleen, and lymph nodes • Phagocytes detect chemicals given off by bacteria • Phagocytes move towards the bacteria along a concentration gradient • The phagocyte adheres to the bacteria and engulfs it • - the cell membrane folds in to form a vacuolearound the bacteria • organelles called lysosomes fuse with the vacuole • these release digestive enzymes into the vacuole • bacterium gets digested • Large numbers of phagocytes flood towards an infected area • Dead phagocytes & bacteria accumulate to form pus

7. Immune response • Immunity – ability to resist infectious disease • Specific Immune Response • Antigens - complex molecules recognised by the body as being alien/foreign • When they arrive in the bloodstream, lymphocytes (white blood cells) produce antibodies • These proteins have a Y-shape structure • Each arm has a receptor specific to each antigen • When the antibody locks on it makes the antigen harmless • Immunological Memory • When infected for the first time, the body produces antibodies • This is the primary response • Often it is slow, and the person will usually suffer from the disease • Memory cells (lymphocytes) will remember the infection • If re-exposed, the secondary response will start • Specific memory cells will release a flood of antibody-producing lymphocytes • More antibodies produced • Antibodies produced for longer • Response is much faster