ScienceAges 13-15

Human body systems & organs

Connect major human organs and systems to digestion, circulation, respiration and coordination. Review suitability for your learners before teaching.

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Worksheet StudioPractice pack · Ages 13-15

Human body systems & organs

Take your time. Show your thinking.

1. Why does the human stomach produce hydrochloric acid: to kill harmful bacteria and provide the acidic pH for pepsin (protease) enzymes, or to digest bones into gold?
Heart · Lungs · Digestive Tract
2. Which component of human blood contains haemoglobin and transports oxygen from the lungs to body tissues: red blood cells or platelets?
Heart · Lungs · Digestive Tract
3. Which nutrient group serves as the body’s primary fuel for cellular respiration (found in rice, bread, pasta and fruit): carbohydrates or minerals?
Heart · Lungs · Digestive Tract
4. What is the main function of the large intestine (colon): to absorb remaining water from undigested food waste, or to pump blood?
Heart · Lungs · Digestive Tract
5. Which component of blood defends the body against pathogens by engulfing microbes or producing antibodies: white blood cells or red blood cells?
Heart · Lungs · Digestive Tract
6. Which blood vessels carry blood BACK toward the heart and contain valves to prevent backflow: veins or arteries?
Heart · Lungs · Digestive Tract
7. Where does digestion begin in the human body through chewing and the action of salivary amylase: in the mouth or in the large intestine?
Heart · Lungs · Digestive Tract
8. Which microscopic blood vessels have walls only one cell thick to allow rapid exchange of oxygen, nutrients and waste with body tissues: capillaries or arteries?
Heart · Lungs · Digestive Tract
9. Which organ produces bile (stored in the gallbladder) to neutralise stomach acid and emulsify fats into tiny droplets: the liver or the lungs?
Heart · Lungs · Digestive Tract
10. Which tiny cell fragments in blood help form clots at a wound to stop bleeding: platelets or red blood cells?
Heart · Lungs · Digestive Tract
11. In which long, folded organ of the digestive system are most digested nutrients absorbed into the bloodstream through tiny finger-like villi: the small intestine or the oesophagus?
Heart · Lungs · Digestive Tract
12. Which dome-shaped muscle beneath the lungs contracts and flattens when you inhale, increasing chest volume and drawing air in: the diaphragm or the bicep?
Heart · Lungs · Digestive Tract

12 questions · Seed 104732 · Age guidance, not curriculum certification

View the answer key

Worksheet StudioAnswer key · Ages 13-15

Human body systems & organs

Answers and reasoning. Review before teaching.

1. Why does the human stomach produce hydrochloric acid: to kill harmful bacteria and provide the acidic pH for pepsin (protease) enzymes, or to digest bones into gold?
To kill harmful bacteria and provide the acidic pH for pepsin (protease) enzymes
Stomach acid (pH ≈ 1.5–2) destroys pathogens and activates protease enzymes.
2. Which component of human blood contains haemoglobin and transports oxygen from the lungs to body tissues: red blood cells or platelets?
Red blood cells
Red blood cells (erythrocytes) are packed with haemoglobin and lack a nucleus to maximise oxygen transport.
3. Which nutrient group serves as the body’s primary fuel for cellular respiration (found in rice, bread, pasta and fruit): carbohydrates or minerals?
Carbohydrates
Carbohydrates are broken down into glucose, the main fuel for cellular respiration.
4. What is the main function of the large intestine (colon): to absorb remaining water from undigested food waste, or to pump blood?
To absorb remaining water from undigested food waste
The large intestine reabsorbs water and electrolytes, leaving semi-solid faeces.
5. Which component of blood defends the body against pathogens by engulfing microbes or producing antibodies: white blood cells or red blood cells?
White blood cells
White blood cells (leukocytes) are key cells of the immune system.
6. Which blood vessels carry blood BACK toward the heart and contain valves to prevent backflow: veins or arteries?
Veins
Veins operate at lower pressure and use one-way valves to keep blood flowing toward the heart.
7. Where does digestion begin in the human body through chewing and the action of salivary amylase: in the mouth or in the large intestine?
In the mouth
Teeth mechanically break down food while saliva begins digesting starch into maltose.
8. Which microscopic blood vessels have walls only one cell thick to allow rapid exchange of oxygen, nutrients and waste with body tissues: capillaries or arteries?
Capillaries
Thin capillary walls provide a short diffusion pathway between blood and cells.
9. Which organ produces bile (stored in the gallbladder) to neutralise stomach acid and emulsify fats into tiny droplets: the liver or the lungs?
Liver
The liver secretes alkaline bile, which emulsifies lipids to increase surface area for lipase enzymes.
10. Which tiny cell fragments in blood help form clots at a wound to stop bleeding: platelets or red blood cells?
Platelets
Platelets trigger blood clotting to seal damaged vessels.
11. In which long, folded organ of the digestive system are most digested nutrients absorbed into the bloodstream through tiny finger-like villi: the small intestine or the oesophagus?
Small intestine
Villi and microvilli in the small intestine provide a huge surface area for nutrient absorption.
12. Which dome-shaped muscle beneath the lungs contracts and flattens when you inhale, increasing chest volume and drawing air in: the diaphragm or the bicep?
Diaphragm
Contraction of the diaphragm and intercostal muscles expands the thorax, lowering pressure so air flows into the lungs.

12 questions · Seed 104732 · Age guidance, not curriculum certification

Worksheet StudioPractice pack · Ages 13-15

Human body systems & organs

Take your time. Show your thinking.

1. Why does the human stomach produce hydrochloric acid: to kill harmful bacteria and provide the acidic pH for pepsin (protease) enzymes, or to digest bones into gold?
Heart · Lungs · Digestive Tract
2. Which component of human blood contains haemoglobin and transports oxygen from the lungs to body tissues: red blood cells or platelets?
Heart · Lungs · Digestive Tract
3. Which nutrient group serves as the body’s primary fuel for cellular respiration (found in rice, bread, pasta and fruit): carbohydrates or minerals?
Heart · Lungs · Digestive Tract
4. What is the main function of the large intestine (colon): to absorb remaining water from undigested food waste, or to pump blood?
Heart · Lungs · Digestive Tract
5. Which component of blood defends the body against pathogens by engulfing microbes or producing antibodies: white blood cells or red blood cells?
Heart · Lungs · Digestive Tract
6. Which blood vessels carry blood BACK toward the heart and contain valves to prevent backflow: veins or arteries?
Heart · Lungs · Digestive Tract
7. Where does digestion begin in the human body through chewing and the action of salivary amylase: in the mouth or in the large intestine?
Heart · Lungs · Digestive Tract
8. Which microscopic blood vessels have walls only one cell thick to allow rapid exchange of oxygen, nutrients and waste with body tissues: capillaries or arteries?
Heart · Lungs · Digestive Tract
9. Which organ produces bile (stored in the gallbladder) to neutralise stomach acid and emulsify fats into tiny droplets: the liver or the lungs?
Heart · Lungs · Digestive Tract
10. Which tiny cell fragments in blood help form clots at a wound to stop bleeding: platelets or red blood cells?
Heart · Lungs · Digestive Tract
11. In which long, folded organ of the digestive system are most digested nutrients absorbed into the bloodstream through tiny finger-like villi: the small intestine or the oesophagus?
Heart · Lungs · Digestive Tract
12. Which dome-shaped muscle beneath the lungs contracts and flattens when you inhale, increasing chest volume and drawing air in: the diaphragm or the bicep?
Heart · Lungs · Digestive Tract

12 questions · Seed 104732 · Age guidance, not curriculum certification

Worksheet StudioAnswer key · Ages 13-15

Human body systems & organs

Answers and reasoning. Review before teaching.

1. Why does the human stomach produce hydrochloric acid: to kill harmful bacteria and provide the acidic pH for pepsin (protease) enzymes, or to digest bones into gold?
To kill harmful bacteria and provide the acidic pH for pepsin (protease) enzymes
Stomach acid (pH ≈ 1.5–2) destroys pathogens and activates protease enzymes.
2. Which component of human blood contains haemoglobin and transports oxygen from the lungs to body tissues: red blood cells or platelets?
Red blood cells
Red blood cells (erythrocytes) are packed with haemoglobin and lack a nucleus to maximise oxygen transport.
3. Which nutrient group serves as the body’s primary fuel for cellular respiration (found in rice, bread, pasta and fruit): carbohydrates or minerals?
Carbohydrates
Carbohydrates are broken down into glucose, the main fuel for cellular respiration.
4. What is the main function of the large intestine (colon): to absorb remaining water from undigested food waste, or to pump blood?
To absorb remaining water from undigested food waste
The large intestine reabsorbs water and electrolytes, leaving semi-solid faeces.
5. Which component of blood defends the body against pathogens by engulfing microbes or producing antibodies: white blood cells or red blood cells?
White blood cells
White blood cells (leukocytes) are key cells of the immune system.
6. Which blood vessels carry blood BACK toward the heart and contain valves to prevent backflow: veins or arteries?
Veins
Veins operate at lower pressure and use one-way valves to keep blood flowing toward the heart.
7. Where does digestion begin in the human body through chewing and the action of salivary amylase: in the mouth or in the large intestine?
In the mouth
Teeth mechanically break down food while saliva begins digesting starch into maltose.
8. Which microscopic blood vessels have walls only one cell thick to allow rapid exchange of oxygen, nutrients and waste with body tissues: capillaries or arteries?
Capillaries
Thin capillary walls provide a short diffusion pathway between blood and cells.
9. Which organ produces bile (stored in the gallbladder) to neutralise stomach acid and emulsify fats into tiny droplets: the liver or the lungs?
Liver
The liver secretes alkaline bile, which emulsifies lipids to increase surface area for lipase enzymes.
10. Which tiny cell fragments in blood help form clots at a wound to stop bleeding: platelets or red blood cells?
Platelets
Platelets trigger blood clotting to seal damaged vessels.
11. In which long, folded organ of the digestive system are most digested nutrients absorbed into the bloodstream through tiny finger-like villi: the small intestine or the oesophagus?
Small intestine
Villi and microvilli in the small intestine provide a huge surface area for nutrient absorption.
12. Which dome-shaped muscle beneath the lungs contracts and flattens when you inhale, increasing chest volume and drawing air in: the diaphragm or the bicep?
Diaphragm
Contraction of the diaphragm and intercostal muscles expands the thorax, lowering pressure so air flows into the lungs.

12 questions · Seed 104732 · Age guidance, not curriculum certification