Would killing germs cure a disease caused only by missing nutrients?

No. The missing nutrients must be supplied; germs did not cause this disease.

Where does the malaria parasite reproduce sexually?

Inside a female Anopheles mosquito. Its life cycle includes essential stages outside humans.

Which built-in chemical defence meets swallowed germs in the stomach?

Stomach acid. Innate protection includes chemical barriers as well as skin.

What allows a faster response when the same antigen returns?

Memory cells. Acquired immunity retains cells prepared for that antigen.

After foreign germs disappear, what can an autoimmune attack in a joint still target?

The joint's own tissues. Removing foreign germs does not remove the tissues targeted by autoimmunity.

Does sharing a meal transmit HIV?

No. Ordinary shared meals do not provide a route for HIV transmission.

A tumour has stayed in one organ. What doesn't this prove about its type?

That it is benign. A malignant tumour may not have spread to distant organs.

What effect of dependence can make stopping substance use need medical care?

Withdrawal. Physical effects can require treatment beyond a decision to stop.

Teach Human Health and Disease in eight steps.

For each idea: show it, ask before you tell, then say one line.

Gather a drinking-water container, cup and unused dressing.

Common misconceptions & worked visual for this chapter · 15 practice questions with answers

Why it matters

Safe drinking water reduces infections carried by contaminated water.
Vaccines prepare immune defences before an infection arrives.
Mosquito nets reduce bites that can transmit malaria.

What to teach

How to teach it

Health and infections

Covered steel drinking-water container beside a clean cup.

1. Health and common diseases in humans

Health includes physical, mental and social well-being.

Show: Inspect your water container and cup. Trace the water from its supply through storage to serving.
Ask: If this container stayed uncovered, how could its water become contaminated before serving?
Say: Dust or insects could carry germs into water while the container stays uncovered.
Used in: Good nutrition supplies essential nutrients, helping prevent deficiency diseases.

If your child says…“Every disease comes from germs.”

Ask: How would killing germs replace a missing nutrient?
What’s true: Genes, nutrition and surroundings also affect health; illness may begin before visible symptoms.

Malaria parasite routes between a mosquito, human liver and red blood cells.

2. Malaria

A parasite passes between humans and infected female mosquitoes.

Show: Find the liver, red blood cells and female Anopheles mosquito in the diagram. Follow the arrows between them.
Ask: Which transfer would sleeping under a mosquito net reduce?
Say: Nets reduce bites, so they reduce parasite transfer both to humans and to mosquitoes. The parasite reaches the liver, then red blood cells.
Used in: Preventing mosquito breeding reduces the insects available to transmit malaria.

If your child says…“The parasite completes its whole life inside us.”

Ask: Where does the parasite reproduce sexually?
What’s true: The parasite needs both hosts and reproduces sexually inside female Anopheles mosquitoes.

Immune defences

Intact skin on one hand beside an unused dressing with its protective pad exposed.

3. Innate immunity

Built-in defences act broadly without remembering particular germs.

Show: Look at intact skin on a hand. Inspect an unused dressing's protective pad.
Ask: What becomes easier for germs when skin is cut?
Say: Entry becomes easier for germs when skin is cut; intact skin reduces entry.
Used in: Mucus traps microbes in airways, helping protect the lungs.

If your child says…“Skin is our only built-in defence.”

Ask: What protects against germs that reach the stomach?
What’s true: Stomach acid kills many swallowed germs, while mucus and protective cells also provide built-in defence.

Active immunity produces antibodies and memory cells; passive immunity supplies temporary antibodies.

4. Acquired immunity, active and passive immunity

Specific defences can remember; borrowed antibodies provide temporary protection.

Show: Follow the diagram's B-cell branches to plasma cells and memory cells. Find the separate antibody route.
Ask: Which route could protect immediately without creating memory?
Say: Transferred antibodies act promptly without creating memory.
Used in: Ready-made antibodies provide rapid, temporary protection.

If your child says…“Vaccines just supply antibodies.”

Ask: Which route leaves cells ready to respond when that antigen returns?
What’s true: Plasma cells formed from B cells produce antibodies; transferred antibodies create no immune memory.

Pollen triggers histamine release on the left; immune cells attack own tissue on the right.

5. Allergies and auto immunity

Defences can overreact to harmless substances or attack our tissues.

Show: In the diagram, follow pollen to IgE already attached to the mast cell, then released histamine. On the right, follow the immune cells' attack arrows towards their own tissue.
Ask: How could either response shown cause illness without a harmful germ?
Say: Normally harmless pollen can trigger histamine release from sensitised mast cells, causing allergy symptoms. In autoimmunity, immune cells attack your own tissues.
Used in: Identifying an allergy trigger helps reduce exposure and symptoms.

If your child says…“Pollen causes allergies, so it must be a germ.”

Ask: Does a strong defence reaction prove that its trigger causes infection?
What’s true: An allergy can be an excessive response to a normally harmless substance.

HIV replication inside a helper T cell, with declining cell numbers weakening defence.

6. AIDS

Advanced HIV infection can severely weaken immune defences.

Show: Follow HIV into the diagram's helper T cell. Trace viral RNA to viral DNA, into host DNA, then towards new viruses. Below, follow fewer T cells towards weaker defence.
Ask: How could this virus make someone vulnerable to many other infections?
Say: HIV uses helper T cells to make new viruses. Over time, losing these cells weakens defence against many infections.
Used in: Testing donated blood for HIV reduces transmission through transfusions.

If your child says…“Sharing lunch spreads HIV.”

Ask: Which of those transmission routes occurs simply through eating together?
What’s true: HIV can pass through infected blood, sexual contact or mother-to-child transmission, not ordinary shared meals.

Cancer and dependence

Cancer cells cross a tissue boundary and travel through blood to a distant tumour.

7. Cancer

Cells escape growth controls and invade nearby tissue.

Show: In the diagram, find the orderly layer, then the cluster crossing a tissue boundary. Locate the nearby blood vessel. After predicting, trace the route through the vessel to the distant cluster.
Ask: Which cluster could spread through that vessel?
Say: The crowded cluster could spread through that vessel. Cancer cells can invade nearby tissue and sometimes establish growths elsewhere.
Used in: Examining biopsy tissue helps doctors identify cancer and plan treatment.

If your child says…“Every tumour is cancer that spreads.”

Ask: Does a local growth automatically show invasion or spread?
What’s true: Benign tumours remain local; malignant tumours invade and may spread.

Equal doses produce different effects; a separate pathway links physical dependence and withdrawal.

8. Drugs and alcohol abuse

Repeated substance use can change responsiveness and cause dependence.

Show: Compare identical doses and effect bars in the diagram. Follow dependence through stopping use to withdrawal.
Ask: Why might stopping cause distress even when the same dose has less effect?
Say: Tolerance reduces the same dose's effect as the body adapts. Physical dependence can cause withdrawal when use stops.
Used in: Counselling supports recovery by helping people manage substance-use urges.

If your child says…“Ending addiction only takes willpower.”

Ask: What could determination alone leave untreated if stopping causes withdrawal?
What’s true: Dependence can cause withdrawal, so recovery may need medical care and support.

A real problem

Vaccination helped contain smallpox outbreaks in India.

Smallpox spread easily, and no cure was known.

Health workers vaccinated contacts of people with smallpox to contain outbreaks.

India's final smallpox case was found in May 1975.

WHO University of Michigan Library

Closed vaccine carrier on an Indian village lane.

Concept Lab · Common misconception

The tempting mistake in Human Health and Disease

Open standalone misconception page →

Does receiving antibodies build long-term immune memory?

Wrong

Ready-made antibodies give lasting immunity because the body now has the antibodies it needs.

Why it feels right. I confuse protection by antibodies with the process that creates memory cells.

Right

Passive immunity supplies antibodies. Active immunity activates the recipient's own immune response and can build memory.

Worked example

Passive protection

Antibodies supplied→Rapid protection→Wanes as antibodies clear

Active response

Vaccination→Immune response→Memory supports faster later response

Ready-made antibodies can act quickly and wane. An effective vaccine response can establish immune memory.

A dose of ready-made antibodies can provide protection quickly and then wane as the antibodies are cleared.
After an effective vaccine response, memory cells can support a faster response to a later exposure.

Ask your child eight quick questions.

One per step. The answer and the reason are given.

Would killing germs cure a disease caused only by missing nutrients?

No. The missing nutrients must be supplied; germs did not cause this disease.
Where does the malaria parasite reproduce sexually?

Inside a female Anopheles mosquito. Its life cycle includes essential stages outside humans.
Which built-in chemical defence meets swallowed germs in the stomach?

Stomach acid. Innate protection includes chemical barriers as well as skin.
What allows a faster response when the same antigen returns?

Memory cells. Acquired immunity retains cells prepared for that antigen.
After foreign germs disappear, what can an autoimmune attack in a joint still target?

The joint's own tissues. Removing foreign germs does not remove the tissues targeted by autoimmunity.
Does sharing a meal transmit HIV?

No. Ordinary shared meals do not provide a route for HIV transmission.
A tumour has stayed in one organ. What doesn't this prove about its type?

That it is benign. A malignant tumour may not have spread to distant organs.
What effect of dependence can make stopping substance use need medical care?

Withdrawal. Physical effects can require treatment beyond a decision to stop.

15 more questions with answers

Teach Human Health and Disease in eight steps.

Why it matters