Chapter 9 - Protection Against Invaders

Question 0

Are Bacteria harmful?

Answer 0

Nope, most of them are non-pathogenic.

Question 1

What are Pathogens?

Answer 1

Disease-causing organisms.

Eg. Bacteria and viruses

Question 2

What is a Bacteria?

Answer 2

Bacteria consist of a single cell and can be seen only with a microscope.

Question 3

What are Viruses?

Answer 3

They are too small to be seen with an ordinary microscope, they have distinctive structures and differing sizes. Found to contain genetic material.

Question 4

How do Viruses spread?

Answer 4

When the viruses infects a living cell, it’s 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 5

What are Bacteriophages?

Answer 5

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

Question 6

What are Parasites?

Answer 6

Organisms that live on or in another living thing, the host, and gain food and shelter from it. They may cause the host little or much harm, depending on the nature of the relationship.

Question 7

What’s the difference between non-specific and specific defences?

Answer 7

Non-specific defences are defences that work against ALL pathogens (skin), and Specific Defences are directed at a particular pathogen.

Question 8

What is Sebum?

Answer 8

It is secreted by oil glands in the skin, contains substances that kill some pathogenic bacteria.

Question 9

List some protective reflexes.

Answer 9

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

Question 10

What is the purpose of Blood Clotting?

Answer 10

Helps to minimize blood loss from the broken vessels and prevent the entry of infecting microorganisms.

Question 11

How does Blood Clotting work?

Answer 11

• Constriction occurs immediately after injury to reduce blood flow.
• The internal walls of blood vessels are normally very smooth, but any damage creates a rough surface to which the platelets stick.
• The platelets release substances that act as vasoconstrictors which enhance and prolong the constriction of the damaged vessels.

Question 12

What is Fibrin?

Answer 12

An insoluble protein formed from the complex series of reactions results in the formation of threads. The fibrin threads form a mesh work that traps blood cells platelets and plasma = clot.

Question 13

Explain Clot Reaction.

Answer 13

A slow process which occurs after the formation of the blood clot. The network of threads contracts, becoming denser and stronger and pulling the edges of damaged blood vessels together. Serum is squeezed out.

Question 14

What does a Phagocyte do?

Answer 14

A phagocyte is an internal non-specific defence that attack organisms that penetrate our external defence.

Cells that can engulf and digest micro-organisms and cell debris.

Question 15

What role does the Leucocytes play?

Answer 15

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

Question 16

What are Macrophages?

Answer 16

They are large phagocytic cells that develop from some leucocytes. Some are “wandering” cells that move through the tissues looking for pathogens to come to them while some are fixed in one place.

Question 17

What is the purpose of Inflammation?

Answer 17

Inflammation is a response to any damage to the tissues.

• Reduce the spread of any pathogens, to destroy them and prevent the entry of additional pathogens.
• Remove damaged tissue and cell debris.
• Begin the repair of the damaged tissues.

Question 18

What are 4 signs of inflammation?

Answer 18

1. Redness
2. Swelling
3. Heat
4. Pain

Question 19

Explain the Inflammatory Response.

Answer 19

1. When the skin is broken, a non-specific inflammatory response is triggered.
2. Most cells release histamine and heparin. Histamine diffuses into capillaries, causing them to dilate and become leaky. The area becomes red and swells. Heparin prevents clotting in the immediate area.
3. Complement proteins are activated and attract phagocytes to the area, which engulf and digest dead cells and bacteria.
4. The tissue heals when histamine and complement protein signaling finish and phagocytes are no longer attracted to the area.

Question 20

What is a Histamine?

Answer 20

A substance which 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 the heat and redness associated with inflammation and the escape of sulks from the blood causes the swelling.

Question 21

What is the role of the Heparin?

Answer 21

Prevents clotting so the release of heparin from the most cells prevents clotting in the immediate area if the injury. A cloth of the fluid around the damaged area does form and this slows the spread of the pathogen into healthy tissues.

Question 22

What does the Lymphatic System consist of?

Answer 22

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

Question 23

What is the main function of the Lymphatic System?

Answer 23

To collect some of the fluid that escapes from the blood capillaries and return it to the circulatory system.

Question 24

Explain Lymph Vessels.

Answer 24

Excess fluid returns to the blood by the lymphatic system. =Lymph

Lymph does not circulate, the lymphatic system is a one-way system carrying fluid away from the tissues.

Question 25

Characteristics of a Lymph Capillary.

Answer 25

• Usually slightly larger than blood capillaries.

* More permeable than most blood capillaries.

Question 26

Explain Lymph Nodes.

Answer 26

Occurs at intervals along the lymphatic vessels.

Structure: Each node is surrounded by a capsule of connective tissue that extends into the node, forming a framework which consist of masses of lymphoid tissue, containing cells known as lymphocytes, macrophages and plasma cell.

Question 27

What is the role of Mechanical barriers?

Answer 27

Provides an obstacle to invading pathogens and therefore reduce the risk of getting a disease

• Surgical masks
• Protective clothing

Question 28

Explain the process of Sneezing.

Answer 28

The stimulus for sneezing is irritation of the walls of the nasal cavity. The irritation may be caused by noxious flames or dust particles and irritating gases out through the nose and mouth.

Question 29

Explain the process of Coughing.

Answer 29

For coughing, the stimulus irritation in the lower respiratory tract the bronchi and bronchioles. In a manner similar to sneezing air is forced from the lungs to try to remove the irritant. The air drives mucus and foreign matter up the trachea towards the throat and mouth.

Question 30

The process of Vomiting.

Answer 30

Psychological stimuli, excessive stretching of the stomach and bacterial toxins can all induce vomiting. It is not contraction of the stomach but contraction of the muscles or the abdomen and the diaphragm that expel the stomach contents.

Question 31

Explain the process of Diarrhea.

Answer 31

Irritation of the small and large intestines by bacteria, viruses or protozoans can cause diarrhea. The irritation causes increased contractions of the muscles of the wall of the intestines so that the irritant is removed as quickly as possible. Material does not stay in the large intestine long enough for water to be absorbed so the farces are very watery.