MCQ on Structure and Function of Human Organ Systems

🟢 Easy (1–20)

1. Which organ pumps blood throughout the body?
   A. Lungs
   B. Liver
   C. Kidney
   D. Heart ✅
   Explanation: The heart is the main organ that circulates blood via the cardiovascular system.
2. Which organ system is responsible for breathing?
   A. Circulatory system
   B. Digestive system
   C. Nervous system
   D. Respiratory system ✅
   Explanation: The respiratory system includes the lungs and airways, responsible for gas exchange.
3. Which organ filters blood and produces urine?
   A. Liver
   B. Spleen
   C. Kidney ✅
   D. Pancreas
   Explanation: Kidneys filter waste from blood and regulate fluid balance through urine formation.
4. Which part of the brain controls balance and coordination?
   A. Cerebrum
   B. Medulla
   C. Cerebellum ✅
   D. Thalamus
   Explanation: The cerebellum regulates voluntary motor movements, balance, and coordination.
5. What is the main function of the small intestine?
   A. Water absorption
   B. Food storage
   C. Protein synthesis
   D. Nutrient absorption ✅
   Explanation: Most nutrient absorption takes place in the small intestine.
6. Which organ is part of both the digestive and endocrine systems?
   A. Liver
   B. Pancreas ✅
   C. Gallbladder
   D. Kidney
   Explanation: The pancreas produces digestive enzymes and hormones like insulin.
7. Which type of blood vessel carries blood away from the heart?
   A. Vein
   B. Capillary
   C. Artery ✅
   D. Venule
   Explanation: Arteries carry oxygenated blood away from the heart.
8. Where does gas exchange occur in the lungs?
   A. Bronchi
   B. Trachea
   C. Alveoli ✅
   D. Bronchioles
   Explanation: Alveoli are tiny sacs where oxygen and carbon dioxide are exchanged.
9. Which organ produces bile?
   A. Pancreas
   B. Gallbladder
   C. Liver ✅
   D. Stomach
   Explanation: The liver produces bile, which helps in fat digestion.
10. The largest organ in the human body is the:
    A. Liver
    B. Brain
    C. Skin ✅
    D. Heart
    Explanation: Skin is the body’s largest organ and provides protection and regulation.
11. Which organ system includes bones and joints?
    A. Nervous system
    B. Muscular system
    C. Skeletal system ✅
    D. Endocrine system
    Explanation: The skeletal system provides structure and support.
12. The heart is divided into how many chambers?
    A. 2
    B. 3
    C. 4 ✅
    D. 5
    Explanation: The heart has two atria and two ventricles.
13. Which system controls body activities with hormones?
    A. Nervous system
    B. Circulatory system
    C. Excretory system
    D. Endocrine system ✅
    Explanation: The endocrine system uses hormones to regulate body functions.
14. Which blood cells help in clotting?
    A. Red blood cells
    B. White blood cells
    C. Platelets ✅
    D. Plasma
    Explanation: Platelets play a key role in the blood clotting process.
15. Which part of the digestive system stores bile?
    A. Liver
    B. Stomach
    C. Gallbladder ✅
    D. Intestine
    Explanation: The gallbladder stores bile produced by the liver.
16. Which type of muscle is found in the heart?
    A. Skeletal
    B. Smooth
    C. Cardiac ✅
    D. Voluntary
    Explanation: Cardiac muscle is specialized for the heart’s continuous activity.
17. Which organ system is responsible for removing waste from the body?
    A. Digestive system
    B. Respiratory system
    C. Excretory system ✅
    D. Nervous system
    Explanation: The excretory system eliminates metabolic wastes (e.g., through urine).
18. The main function of red blood cells is to:
    A. Fight infections
    B. Help in clotting
    C. Carry oxygen ✅
    D. Produce hormones
    Explanation: Hemoglobin in red blood cells binds oxygen for transport.
19. Which organ connects the mouth to the stomach?
    A. Trachea
    B. Esophagus ✅
    C. Pharynx
    D. Duodenum
    Explanation: The esophagus is a muscular tube that transports food to the stomach.
20. Which structure protects the lungs and heart?
    A. Skull
    B. Spine
    C. Pelvis
    D. Rib cage ✅
    Explanation: The rib cage encases and protects thoracic organs.

🟡 Moderate (21–40)

21. Which part of the nervous system controls involuntary actions?
    A. Cerebrum
    B. Somatic nervous system
    C. Autonomic nervous system ✅
    D. Spinal cord
    Explanation: The autonomic system manages involuntary functions like heart rate and digestion.
22. The functional unit of the kidney is called:
    A. Neuron
    B. Nephron ✅
    C. Alveolus
    D. Axon
    Explanation: Nephrons filter blood and form urine.
23. Which hormone regulates the sleep-wake cycle?
    A. Insulin
    B. Melatonin ✅
    C. Adrenaline
    D. Glucagon
    Explanation: Melatonin, secreted by the pineal gland, controls circadian rhythms.
24. Which valve prevents blood from flowing back into the left atrium?
    A. Tricuspid
    B. Pulmonary
    C. Aortic
    D. Mitral ✅
    Explanation: The mitral valve ensures one-way blood flow from the atrium to ventricle.
25. Which cells are responsible for transmitting nerve impulses?
    A. Glial cells
    B. Epithelial cells
    C. Neurons ✅
    D. Platelets
    Explanation: Neurons are specialized to carry electrical signals.
26. What connects muscles to bones?
    A. Ligaments
    B. Cartilage
    C. Tendons ✅
    D. Discs
    Explanation: Tendons attach muscles to bones to enable movement.
27. The thyroid gland is located in the:
    A. Brain
    B. Chest
    C. Neck ✅
    D. Abdomen
    Explanation: The thyroid lies in the neck and regulates metabolism.
28. Which blood vessel has the thinnest walls?
    A. Artery
    B. Vein
    C. Capillary ✅
    D. Arteriole
    Explanation: Capillaries are one cell thick to allow diffusion of gases and nutrients.
29. What is the main function of the large intestine?
    A. Nutrient absorption
    B. Digestion of proteins
    C. Water absorption ✅
    D. Bile production
    Explanation: The large intestine absorbs water and forms feces.
30. Which organ controls body temperature regulation?
    A. Pituitary
    B. Cerebrum
    C. Hypothalamus ✅
    D. Thalamus
    Explanation: The hypothalamus maintains homeostasis, including temperature control.
31. Which part of the brain controls breathing and heart rate?
    A. Cerebrum
    B. Cerebellum
    C. Medulla oblongata ✅
    D. Corpus callosum
    Explanation: The medulla regulates autonomic vital functions.
32. Which blood component helps in fighting infections?
    A. Platelets
    B. Red blood cells
    C. White blood cells ✅
    D. Plasma
    Explanation: WBCs are part of the immune system and fight pathogens.
33. Insulin is secreted by the:
    A. Liver
    B. Gallbladder
    C. Pituitary gland
    D. Pancreas ✅
    Explanation: Pancreatic beta cells produce insulin to regulate blood sugar.
34. Which organ stores vitamins and detoxifies chemicals?
    A. Spleen
    B. Kidney
    C. Liver ✅
    D. Pancreas
    Explanation: The liver stores nutrients and detoxifies harmful substances.
35. Which part of the eye controls the amount of light entering?
    A. Cornea
    B. Lens
    C. Retina
    D. Iris ✅
    Explanation: The iris adjusts the size of the pupil to control light intake.
36. Which chamber of the heart receives oxygenated blood from lungs?
    A. Right atrium
    B. Left atrium ✅
    C. Right ventricle
    D. Left ventricle
    Explanation: Oxygenated blood returns via pulmonary veins to the left atrium.
37. Which hormone increases blood sugar levels?
    A. Insulin
    B. Estrogen
    C. Glucagon ✅
    D. Oxytocin
    Explanation: Glucagon stimulates liver to release glucose into blood.
38. Which system includes glands that secrete hormones?
    A. Nervous system
    B. Endocrine system ✅
    C. Circulatory system
    D. Skeletal system
    Explanation: Endocrine glands regulate bodily functions via hormone secretion.
39. The diaphragm plays a key role in:
    A. Digestion
    B. Circulation
    C. Breathing ✅
    D. Excretion
    Explanation: The diaphragm contracts and relaxes to aid in respiration.
40. The trachea connects the larynx to the:
    A. Esophagus
    B. Lungs
    C. Pharynx
    D. Bronchi ✅
    Explanation: The trachea divides into bronchi, directing air into each lung.

🔴 Hard (41–50)

41. Which structure increases surface area in the small intestine?
    A. Villi ✅
    B. Cilia
    C. Rugae
    D. Alveoli
    Explanation: Villi are finger-like projections that increase surface area for absorption.
42. Which part of the nephron is responsible for reabsorption?
    A. Glomerulus
    B. Loop of Henle ✅
    C. Collecting duct
    D. Bowman’s capsule
    Explanation: The loop of Henle reabsorbs water and salts from filtrate.
43. Which brain lobe processes visual information?
    A. Frontal
    B. Parietal
    C. Temporal
    D. Occipital ✅
    Explanation: The occipital lobe interprets signals from the eyes.
44. Which immune cells produce antibodies?
    A. T cells
    B. Macrophages
    C. B cells ✅
    D. Neutrophils
    Explanation: B lymphocytes differentiate into plasma cells to produce antibodies.
45. Which molecule carries oxygen in blood?
    A. Myosin
    B. Hemoglobin ✅
    C. Actin
    D. Insulin
    Explanation: Hemoglobin in RBCs binds and transports oxygen.
46. Which gland regulates calcium levels in blood?
    A. Pituitary
    B. Adrenal
    C. Thyroid
    D. Parathyroid ✅
    Explanation: Parathyroid hormone increases blood calcium levels.
47. Which part of the ear helps with balance?
    A. Cochlea
    B. Eustachian tube
    C. Semicircular canals ✅
    D. Tympanic membrane
    Explanation: Semicircular canals detect head movements and maintain balance.
48. Which muscle is involuntary and non-striated?
    A. Skeletal
    B. Cardiac
    C. Smooth ✅
    D. Voluntary
    Explanation: Smooth muscles control internal organ movement without conscious effort.
49. The primary function of lymph nodes is to:
    A. Store fat
    B. Filter lymph ✅
    C. Produce enzymes
    D. Regulate blood pressure
    Explanation: Lymph nodes filter pathogens and house immune cells.
50. Which structure prevents food from entering the trachea?
    A. Larynx
    B. Pharynx
    C. Epiglottis ✅
    D. Uvula
    Explanation: The epiglottis covers the trachea during swallowing to prevent choking.