Blood, transport and infections By Tibor Cemicky

The Composition Of Blood Composed of: – Plasma – Erythrocytes (red blood cells) – Leukocytes (white blood cells) – Platelets

Plasma It‘s role is to transport the following throughout the body: – Nutrients – Carbon Dioxide – Hormones – Antibodies – Urea Plasma forms 55% of out blood

Blood Cells Red Blood Cells – transport oxygen throughout the body Platelets – seal damaged blood vessels after injury to stop bleeding White Blood Cells – cells of immune system, defend body against infections – Phagocytes – Lymphocyte

Types of White Blood Cells Phagocytes – identify pathogens (disease- producing agents) and ingest them using endocytosis. Lymphocytes: release antibodies which destroy pathogens that cannot be killed by phagocytes

Functions of Blood Main Functions: – Transport medium (plasma, red blood cells) – Defence against infectious diseases (white blood cells) It also transports heat throughout the body

Antibodies Antibodies – proteins that recognize and bind to antigens Antigens – Foreign substances that stimulate production of antibodies – e.g cell walls of pathogenic bacteria, protein coats of viruses... Antibodies bind to antigens on surface of pathogens to destroy them

Barriers to Infection Skin and mucous membranes form a barrier protecting the body. Sebaceous glands in the skin secrete acids to make skin acidic. Mucous membranes (e.g in the nose) produce mucous containing lysozyme. Lysozyme kills bacteria and other pathogens.

Antibiotics Antibiotics – chemicals produced by microorganisms to kill or control growth of other microorganism E.g Penicillium fungus produces penicillin to kill bacteria Human and bacterial cells are very different therefore antibiotics can block a process in bacterial cells without harmin human cells Viruses rely on human cells to carry processes for them, therefore viruses cannot be treated with antibiotics