Chapter 7 Set 2

Question 1

Why does the body use external barriers to protect itself? What is an example of some?

Answer 1

To protect itself against the entry of pathogens.
e.g. Skin/Membranes

Question 2

What are some protective reflexes?

Answer 2

Sneezing/Coughing

Question 3

What are some non-specific defences? What does this category mean?

Answer 3

Non-specific defences are responses to a wide range of pathogens.
Examples include the Lymphatic System, Phagocytosis, Inflammation and Fever.

Question 4

What are some specific defences? What does this mean?

Answer 4

Specific defences are responses to specific diseases.
E.g. Antibody-mediated Immunity and Cell-Mediated Immunity.

Question 5

Briefly describe the following external barriers:

• Skin
• Mucous Membranes
• Hairs
• Acids
• Lysozymes
• Cerumen (Ear Wax)

Answer 5

Skin:
Effective barrier covering the outside of the body
Stops entry of microorganisms if unbroken
Good bacteria also prevent the income of bad bacteria
Secretes oily sebum – has substances that kill some bacteria

Mucous Membranes:
Eg in the mouth, nose, conjunctiva, reproductive tract etc
Line body cavities that open to the exterior
Secrete mucus – interferes with micro-organism entry

Hairs:
In nasal cavity, ears, eyelashes
Trap pathogens for processing and removal
Cilia – tiny hairs with beating motion – sweeps mucus and pathogens towards entrance
Trachea
Nasal cavity
Other air passages

Question 6

Briefly describe the following external barriers:

• Acids
• Lysozymes
• Cerumen (Ear Wax)

Answer 6

Acids:
Kill bacteria and other micro-organisms
Eg stomach acid, acidic vaginal secretions, sweat

Lysozyme:
The enzyme that kills bacteria
Contained in tears, saliva, sweat, nasal secretions, tissue fluid

Cerumen:
Ear wax
Slightly acidic, contains lysozyme
Protects ear canal from infection

Question 7

Briefly describe the following Protective Reflexes:

• Sneezing
• Coughing
• Vomiting
• Diarrohea

Answer 7

Sneezing:
Triggered by irritation of nasal cavity
Expels dust, dirt, mucus, and pathogens from mouth

Coughing:
Irritation of lower respiratory tract
Air forced from lungs, taking mucus and pathogens up trachea and out

Vomiting:
Contraction of muscles of abdomen and diaphragm
Expels pathogens from stomach

Diarrhoea:
Irritation of intestinal wall causes fluid to accumulate in intestines, plus explosive contractions of smooth muscle in intestinal wall.

Question 8

What are 3 ways disease can be prevented by assisting the body’s external defences?

Answer 8

• Wearing a mask to prevent the spread of respiratory disease when you are sick
• Wearing condoms to prevent STIs
• Sneezing and COughing in the elbow
• Self-isolating when unwell
• Avoiding contact with infected people
• Mosquito nets to prevent mosquito-born diseases e.g. malaria