BLOOD CHAPTER 14 COMPOSITION Blood consists of plasma

BLOOD CHAPTER 14

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 CO 2 decreasing the blood p. H

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)

HAEMOGLOBIN • A respiratory pigment that combines with oxygen • 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 (k. Pa) • An oxygen dissociation curve shows the relationship between haemoglobin and oxygen

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)

PHAGOCYTOSIS • Bacteria are engulfed and destroyed by phagocytic cells • Non-specific response – only gives general protection • Carried out by monocytes/macrophages • - found in the liver, spleen, and lymph nodes • They detect chemicals given off by bacteria • They move towards the bacteria along a concentration gradient • The phagocyte engulfs the bacteria • - the cell membrane folds to form a vacuole (phagosome) around the bacteria • - 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

IMMUNE RESPONSE • Immunity – ability to resist infectious disease • Specific Immune Response - Antigens - molecules recognised by the body as foreign - When they arrive in the blood, 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 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 - memory cells will release a flood of antibody-producing lymphocytes - More antibodies produced - Antibodies produced for longer - Response is much faster