Chapter 10: Protection Against Invaders

Question 1

• What are communicable or infectious diseases?
• What happens when a virus infects a living cell?
• Explain the difference between bacteria and bacteriophage
• List 4 differences between bacteria and viruses
• Explain why someone with an infected toe may develop a lump in the groin.
• Describe 6 methods of pathogen transmission

Answer 1

• Diseases passed from one person to another by pathogens invading the body.
• It’s DNA or RNA induces the cell to manufacture more virus particles which are then able to leave the host cell to infect others.
• Bacteria are single cell organisms which cause disease whereas bacteriophages are viruses that infect bacteria.
• Bacteria are living and viruses aren’t; Bacteria are smaller than viruses; Bacteria contain both RNA and DNA and viruses have only DNA or RNA; Bacteria has a cell wall and cell membrane and viruses have a protein coat and lipoprotein envelope
• Pathogens from infected toe enter lymph capillaries that lead to lymph nodes in groin. The pathogens are attacked by macrophages and lymphocytes here causing groin lymph node to become swollen.
  1. Contact: Direct or indirect (touch object touched by infected person).
  2. Body fluids: Infected person’s blood or other body fluids comes into contact with mucous membranes or blood of an uninfected person.
  3. Droplets: Droplets of moisture when sneezing or coughing which may be breathed in by others or settle on food to be later digested.
  4. Ingestion: Ingestion of contaminated food/drinks.
  5. Airborne: Moisture containing pathogens in exhaled droplets may evaporate which can cause infection if inhaled.
  6. Vectors: Hosts of pathogens either directly or indirectly (food/water).

Question 2

-Explain the difference between non-specific defences and specific defences.
-What are the 3 types of non-specific defences?
Describe how the following body’s external defence mechanisms work against pathogens:
-Skin
-Mucous membranes
-Hairs
-Cilia
-Digestive tract
-Respiratory system
-Eye

Answer 2

• Non-specific defences defend body against all pathogens and specific defences defend body against specific pathogens.
• External defences, internal non-specific defences and protective reflexes.
• Skin: A Barrier that secretes sebum (oil) containing substances that kill bacteria and sweat containing salts and fatty acids to prevent growth of bacteria.
• Mucous membranes: lines body cavities secreting mucus which inhibits the entry of micro-organisms of the body.
• Hair: found in nose cavity and ears that trap up to 90% of particles.
• Cilia: Projections with a beating motion in mucous membranes moving mucus with trapped pathogens to throat to be removed.
• Digestive tract: acidic juices kills many micro-organisms.
• Respiratory system: mucous membranes along trachea and bronchi trap micro-organisms and saliva cleans the mouth.
• Eye: cleansed by tears, which also contain chemicals inhibiting bacterial growth.

Question 3

Explain the following external defences that prevent pathogens from invading our tissues:

• Acids in stomach
• Lysozymes
• Cerumen
• Flushing actions
• How do protective reflexes help defend the body from infection by pathogenic organisms?
• Describe how sneezing protects against infection.
• Describe how coughing protects against infection
• Describe how vomiting protects against infection

Answer 3

• Acids: Stomach acids kill bacteria taken in with food or those in mucus swallowed.
• Lysozymes: enzymes that kill bacteria.
• Cerumen (ear wax): protects the outer ear against infection by bacteria. It is slightly acidic and contains lysozyme.
• Flushing actions: urine flow in urethra prevents bacterial growth.
• They occur automatically to defend the body by removing pathogens before it has a chance to cause an infection.
• Stimulated by irritation of nasal cavity walls. Forceful expulsion of air from lungs carries mucus and irritants out through nose and mouth.
• Stimulated by irritation in bronchi and bronchioles. Air is forced from lungs to remove the irritant up the trachea and through the mouth.
• Expulsion of stomach contents through abdomen and diaphragm contractions as a result of bacteria, stretched stomach, or psychological factors.

Question 4

-Describe how diarrhoea protects against infection
Explain the following Internal defences and how they deal with invaders if pathogens get past our external defences:
-Phagocytes
-Macrophages
-What are the 3 purposes of inflammation?
-What are 3 examples of Bacteria?
-What are 3 examples of viruses?
-What are 3 examples of Fungi?
-What are 3 examples of Animal parasites?

Answer 4

• Stimulated by irritation of intestines causing increased contractions to remove irritant asap (water isn’t fully absorbed).
• Protect against disease by engulfing and digesting pathogens.
• A phagocytic cell developed from leucocytes. Some wander and others are fixed to one place to destroy pathogens.
• Reduce spread of pathogens, remove damaged tissue and begin repair of the damaged tissue.
• Chlamydia, gonorrhoea and syphilis
• Chickenpox, measles and ebola.
• Ringworm, thrush and tinea
• Tapeworms, roundworms and threadworms

Question 5

• What are the 4 signs of inflammation?
• Explain how the inflammation response occurs.
• Explain how the lymphatic system works as a internal defence against pathogens.
• What are antibiotics?

Answer 5

• Redness, swelling, heat and pain.
• Mast cells release histamine, heparin and other substances. Heparin prevents blood clotting. Histamine increases capillary permeability to increase blood flow to area causing heat and redness and swelling. The abnormal conditions in tissue stimulate pain receptors. ‘Other chemicals’ released by mast cells attract phagocytes to consume the pathogens. The filled phagocytes die and form pus. Damaged tissue and skin are repaired by new cells from mitosis.
• Lymph nodes contain a network of fibres that trap pathogens as lymph flows through it which are destroyed by Macrophages.
• Chemicals that inhibit the growth of, or kill, micro organisms particularly bacteria.