Chapter 10 - Protection Against Invaders

Question 1

What are communicable of infectious diseases? (Also known as transmissible diseases?)

Answer 1

Diseases caused by foreign organisms invading the body and multiplying there. Such disease causing organisms are called pathogens.

Question 2

What is non-pathogenic bacteria?

Answer 2

Bacteria that is harmless to humans.

Question 3

What is the role of the bacteria that is essential to life? What are two examples of this bacteria (food related)

Answer 3

The decomposition of organic material and the cycling of the elements.
Lactobacilli is used to make yogurt and sauerkraut.
The flavour of cheese depends on the type of bacteria used in their production.

Question 4

In the armpit of an adult male, there are more than two million bacteria per square centimetre of the skin surface.

Answer 4

Funky fact

Question 5

Describe the structure of bacteria.

Answer 5

All bacteria consist of a single cell and can only be seen with a microscope. Under a microscope all that can be seen is their cell shape which is used to classify bacteria.

Question 6

Label a diagram of a bacteria cell.

Answer 6

Slime layer - around the outside of some bacteria.
Cell wall - composition varies but often made of peptidoglycan, a combined carbohydrate.
Cell membrane - similar to that of other cells.
Flagella - for movement, may be one or many but not found on all bacteria.
Cytoplasm - appears granular due to the presence of ribosomes. Bacteria do not have membrane-bound organelles such as mitochondria or Golgi apparatus.
DNA - there is no nuclear membrane so the DNA forms a tangle inside the cell. Some of the DNA is in the form of loops called plasmids that can be exchanged during reproduction.
Capsule - formed of complex carbohydrates by some bacteria for protection.

Question 7

What are the four main types of bacteria?

Answer 7

Cocci - spherical cells that may occur singly, in pairs, in clusters or in chains. (Singular ‘coccus’, pairs ‘diplococci’, clusters ‘staphylococci’, chains ‘streptococci’).

Bacilli - rod(tampon) shaped cells that have flagella for movement. (Singular ‘bacillus’).

Spirilla - twisted cells (singular ‘spirillum’)

Vibrio - curved rods and are often shaped like commas.

Question 8

When did scientists start using an electron microscope?

Answer 8

1938

Question 9

Describe the structure of viruses.

Answer 9

Viruses have distinctive structures and differing sizes. All viruses contain genetic material in the form of a molecule of either DNA or RNA but never both. The molecule of DNA or RNA is surrounded by a coat of protein.

Question 10

Explain what happens when a virus infects a living cell.

Answer 10

The viruses DNA or RNA induces the cell to manufacture more virus particles. The new virus particles are then able to leave the host cell to infect others.

Question 11

What are bacteriophages?

Answer 11

Viruses that multiply in bacterial cells, causing the death of the bacterium.

Question 12

What are 5 examples of bacteria and viruses, and 3 examples of fungi and animal parasites.

Answer 12

Bacteria - Scarlet fever, Gonorrhoea, Pneumonia, whooping cough and tuberculosis.

Viruses - HIV/AIDS, chicken pox, Ebola, measles and influenza.

Fungi - Ringworm, thrush, tinea.

Animal parasites - protozoans ; malaria, Arthropods ; lice and scabies.

Question 13

Describe the process of viral replication illustrated by HIV.

Answer 13

HIV >
HIV binds to the receptor site on T-lymphocytes >
Uncoated RNA from the virus enters the lymphocytes >
The virus contains an enzyme that enables it to make a DNA copy of its RNA >
Host cells DNA in nucleus >
DNA copy of HIV RNA intergrates with host cell DNA >
New viral RNA is produced >
Budding of new virus particle from lymphocyte >
New HIV able to infect other cells.

Question 14

What are the 6 main ways pathogens can be spread from one person to another?

Answer 14

• Transmission by contact
• Transfer of body fluids
• Infection by droplets
• Ingestion
• Airborne transmission
• Transmission by vectors

Question 15

What is the difference between non-specific defences and specific defences?

Answer 15

Non-specific defences - work against all pathogens. They are the body’s first line of defence.

Specific defences - directed towards a particular pathogen ; specific resistance

Question 16

What are the 8 main external non specific defences of the body?

Answer 16

• The skin ; huge numbers of bacteria live on the skin all the time. An oily secretion called sebum is produced by oil glands in the skin which kills some pathogenic bacteria. Sweat contains salts and fatty acids that prevent the growth of many micro-organisms.
• Mucous membranes ; secrete mucous which inhibits the entry of microorganisms. The whole of the digestive, urinary and reproductive tracts are protected this way.
• Hairs ; traps 90% of particles inhaled when breathing
• Cilia ; throat, nose cavity etc.
• Acids ; stomach juices are incredibly acidic, as well as the vagina and sweat from the skin is slightly acidic.
• Lysozymes ; an enzyme that kills bacteria. Found in saliva, sweat, secretions of the nose and tissue fluid.
• Cerumen ; ear wax which is lightly acidic and contains lysozymes.
• Flushing

Question 17

What are the 4 main types of protective reflexes?

Answer 17

1. Sneezing
2. Coughing
3. Vomiting
4. Diarrhoea

Question 18

What are the 3 main internal non-specific defences?

Answer 18

Phagocytes - cells that can engulf and digest micro-organisms and cell debris. This is called the process of phagocytosis.

Leucocytes - white blood cells. They are able to leave blood capillaries and migrate through the tissues to places of infection or injury. Some leucocytes secrete substances that destroy bacteria before engulfing, whereas others engulf live bacteria and digest them.

Macrophages - large phagocytise cells that develop from some leucocytes. Some move through tissues looking for pathogens and destroying them. Others are fixed in one place and deal with the pathogens that come to them.

Question 19

What is inflammation? And what are it’s purposes?

Answer 19

Inflammation is a response to any damage to tissues. The purposes of inflammation are to ;

• reduce the spread of any pathogens, to destroy them and prevent the entry of additional pathogens.
• remove damaged tissue and cell debris
• begin repair of the damaged tissue

Question 20

What is the significance of words ending in -itis?

Answer 20

Words ending in -itis indicate inflammation of specific organs or tissues. For example, tonsillitis is the inflammation of the tonsils, meningitis is inflammation of the meninges.
Inflammatory responses to external scratches or mosquito bites are easily observable.

Question 21

What are the four signs of inflammation?

Answer 21

Redness, swelling, heat and pain.

Question 22

Describe the 7 steps of the inflammatory response.

Answer 22

1. When stimulated by mechanical damage or by local chemical changes, mast cells release histamine, heparin and other substances into the tissue fluid.
2. Histamine increases blood flow through the area and causes the walls of the blood capillaries to become more permeable so that fluid is filtered from the blood. It is the increased blood flow that causes heat, redness and swelling.
3. Heparin prevents clotting so the release of heparin from the mast cells prevents clotting in the immediate area of the injury.
4. The chemicals released by the mast cells attract phagocytes. Meanwhile macrophages and leucocytes actively consume micro-organisms and debris by phagocytosis.
5. The abnormal conditions in the tissue stimulate pain receptors.
6. The phagocytes, filled with bacteria, debris and dead cells begins to die. The dead phagocytes and tissue form a yellow liquid called pus.
7. New cells are produced and mitosis and repair of the damaged tissue takes place.

Question 23

What are mast cells?

Answer 23

Mast cells are special cells that are present in most tissues and stimulate and coordinate inflammation by releasing chemicals.

Question 24

What is Fever?

Answer 24

Fever is a rapid increase in body temperature due to the resetting of the body’s thermostat to a higher level. It is beneficial, up to a point, high body temperature is believed to inhibit the growth of some bacteria and viruses and speed up the rate of chemical reactions.

Question 25

What are pyrogens?

Answer 25

Pyrogens are substances that reset the body’s thermostat and are released by white blood cells during the inflammatory response.

Question 26

What does the lymphatic system consist of?

Answer 26

• a network of lymph capillaries joined to larger lymph vessels.
• lymph nodes, which are located along the length of some vessels.

Question 27

What is the main function of the lymphatic system?

Answer 27

To collect some of the fluid that escapes from the blood capillaries and return it to the circulatory system. It also plays an important role in the body’s internal defence against pathogenic organisms.

Question 28

What are lymph vessels and lymph nodes (glands)?

Answer 28

What are lymph vessels
fluid that is returned to the capillaries is called a lymph. These lymph capillaries are generally slightly larger than blood vessels and are more permeable. The lymph vessels join up to form two lymphatic ducts that empty the lymph into large veins in the upper chest.

What are lymph nodes(glands)
most numerous is the neck, armpit, groin and around the alimentary canal. Masses of lymphoid tissue that contain lymphocytes, macrophages and plasma cells. The lymph passes through several nodes before entering the circulatory system.

Question 29

What is the role of the lymphatic system in defence against disease?

Answer 29

Some lymphs that enter nodes contain cell debris, foreign particles and micro-organisms that may cause infection and therefore need to be destroyed.
Larger particles such as bacteria, are trapped in a mesh work of fibres as the lymph flows into the nodes. The bacteria is then destroyed by large phagotic cells called macrophages.

When infections occur, the formation of lymphocytes increase and the lymph nodes become swollen and sore.

Question 30

What can help the body’s non specific defences?

Answer 30

Good hygiene!
Wash your hands before preparing or eating food, after using the toilet, after handling blood or bodily fluids.
Cover your mouth when you cough or sneeze
Wipe surfaces with disinfectant if they have been contaminated with blood or other body fluids. Etc

Question 31

What are some examples of mechanical barriers?

Answer 31

• Wearing masks
• scrubbing up before surgery
• protective clothing
• protective glasses
• condoms