Blood, transport and infections

1. Blood, transport and infections By Tibor Cemicky

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

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

4. 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

5. 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

6. 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

7. 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

8. 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.

9. 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