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. What are the tiny air sacs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses out: alveoli or villi?
Heart · Lungs · Digestive Tract
2. Which vitamin found in citrus fruits and fresh vegetables prevents scurvy and supports healthy connective tissue: Vitamin C or Vitamin D?
Heart · Lungs · Digestive Tract
3. Which tiny cell fragments in blood help form clots at a wound to stop bleeding: platelets or red blood cells?
Heart · Lungs · Digestive Tract
4. 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
5. 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
6. Why is dietary fibre (roughage from vegetables, fruits and whole grains) important even though humans cannot digest it: it keeps food moving smoothly through the intestines, or it turns into bone?
Heart · Lungs · Digestive Tract
7. 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
8. Which muscular tube carries swallowed food from the mouth down to the stomach by wave-like contractions (peristalsis): the oesophagus (gullet) or the trachea (windpipe)?
Heart · Lungs · Digestive Tract
9. 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
10. Which blood vessels carry blood BACK toward the heart and contain valves to prevent backflow: veins or arteries?
Heart · Lungs · Digestive Tract
11. 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
12. Which class of digestive enzymes breaks down proteins into amino acids: proteases or amylases?
Heart · Lungs · Digestive Tract

12 questions · Seed 104735 · 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. What are the tiny air sacs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses out: alveoli or villi?
Alveoli
Millions of alveoli in the lungs provide a large moist surface area surrounded by capillaries for gas exchange.
2. Which vitamin found in citrus fruits and fresh vegetables prevents scurvy and supports healthy connective tissue: Vitamin C or Vitamin D?
Vitamin C
Vitamin C (ascorbic acid) is essential for collagen synthesis and immune health.
3. 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.
4. 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.
5. 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.
6. Why is dietary fibre (roughage from vegetables, fruits and whole grains) important even though humans cannot digest it: it keeps food moving smoothly through the intestines, or it turns into bone?
It keeps food moving smoothly through the intestines
Fibre adds bulk to aid peristalsis and prevent constipation.
7. 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.
8. Which muscular tube carries swallowed food from the mouth down to the stomach by wave-like contractions (peristalsis): the oesophagus (gullet) or the trachea (windpipe)?
Oesophagus (gullet)
Peristalsis in the oesophagus pushes the food bolus into the stomach.
9. 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.
10. 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.
11. 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.
12. Which class of digestive enzymes breaks down proteins into amino acids: proteases or amylases?
Proteases
Proteases (such as pepsin and trypsin) hydrolyse proteins into amino acids.

12 questions · Seed 104735 · Age guidance, not curriculum certification

Worksheet StudioPractice pack · Ages 13-15

Human body systems & organs

Take your time. Show your thinking.

1. What are the tiny air sacs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses out: alveoli or villi?
Heart · Lungs · Digestive Tract
2. Which vitamin found in citrus fruits and fresh vegetables prevents scurvy and supports healthy connective tissue: Vitamin C or Vitamin D?
Heart · Lungs · Digestive Tract
3. Which tiny cell fragments in blood help form clots at a wound to stop bleeding: platelets or red blood cells?
Heart · Lungs · Digestive Tract
4. 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
5. 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
6. Why is dietary fibre (roughage from vegetables, fruits and whole grains) important even though humans cannot digest it: it keeps food moving smoothly through the intestines, or it turns into bone?
Heart · Lungs · Digestive Tract
7. 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
8. Which muscular tube carries swallowed food from the mouth down to the stomach by wave-like contractions (peristalsis): the oesophagus (gullet) or the trachea (windpipe)?
Heart · Lungs · Digestive Tract
9. 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
10. Which blood vessels carry blood BACK toward the heart and contain valves to prevent backflow: veins or arteries?
Heart · Lungs · Digestive Tract
11. 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
12. Which class of digestive enzymes breaks down proteins into amino acids: proteases or amylases?
Heart · Lungs · Digestive Tract

12 questions · Seed 104735 · Age guidance, not curriculum certification

Worksheet StudioAnswer key · Ages 13-15

Human body systems & organs

Answers and reasoning. Review before teaching.

1. What are the tiny air sacs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses out: alveoli or villi?
Alveoli
Millions of alveoli in the lungs provide a large moist surface area surrounded by capillaries for gas exchange.
2. Which vitamin found in citrus fruits and fresh vegetables prevents scurvy and supports healthy connective tissue: Vitamin C or Vitamin D?
Vitamin C
Vitamin C (ascorbic acid) is essential for collagen synthesis and immune health.
3. 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.
4. 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.
5. 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.
6. Why is dietary fibre (roughage from vegetables, fruits and whole grains) important even though humans cannot digest it: it keeps food moving smoothly through the intestines, or it turns into bone?
It keeps food moving smoothly through the intestines
Fibre adds bulk to aid peristalsis and prevent constipation.
7. 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.
8. Which muscular tube carries swallowed food from the mouth down to the stomach by wave-like contractions (peristalsis): the oesophagus (gullet) or the trachea (windpipe)?
Oesophagus (gullet)
Peristalsis in the oesophagus pushes the food bolus into the stomach.
9. 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.
10. 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.
11. 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.
12. Which class of digestive enzymes breaks down proteins into amino acids: proteases or amylases?
Proteases
Proteases (such as pepsin and trypsin) hydrolyse proteins into amino acids.

12 questions · Seed 104735 · Age guidance, not curriculum certification