Free Human Skeleton MCQs with Answers

21. When a muscle fibre is stimulated, the calcium ions needed for contraction are released from the

• A. mitochondria
• B. Golgi apparatus
• C. nucleus
• D. sarcoplasmic reticulum

Explanation: The sarcoplasmic reticulum stores calcium and floods the fibre with it when an impulse arrives along the T tubules. Mitochondria supply the ATP for contraction but not the calcium that triggers it.

22. A single motor neuron together with all the muscle fibres it supplies is called

• A. a sarcomere
• B. a motor unit
• C. a reflex arc
• D. a myofibril

Explanation: All fibres of one motor unit contract together when the neuron fires, and fine muscles like those of the eye have tiny units for precise control. A sarcomere is a contractile segment inside a fibre, a different level of organisation.

23. The immediate reserve that regenerates ATP at the very start of vigorous muscle contraction is

• A. creatine phosphate
• B. glycogen only
• C. lactic acid
• D. haemoglobin

Explanation: Creatine phosphate donates its phosphate to ADP in a single step, replenishing ATP within seconds before glycogen breakdown catches up. Lactic acid is a product of anaerobic glycolysis, not a fuel reserve.

24. The joints between the bones of the skull are

• A. freely movable synovial joints
• B. slightly movable cartilaginous joints
• C. immovable fibrous joints called sutures
• D. ball and socket joints

Explanation: Sutures interlock the skull bones with fibrous tissue, locking the case that protects the brain. Free movement here would be dangerous, which is why the only movable skull bone is the mandible.

25. The joints between the bodies of adjacent vertebrae are best described as

• A. freely movable
• B. immovable
• C. synovial
• D. slightly movable

Explanation: Cartilage discs between vertebrae allow limited movement, and the many small movements add up to the flexibility of the whole column. True free movement belongs to synovial joints such as the shoulder.

26. The elbow joint is an example of

• A. a hinge joint
• B. a pivot joint
• C. a ball and socket joint
• D. a gliding joint

Explanation: The elbow swings in one plane, flexing and extending the forearm like a door hinge. The shoulder and hip are ball and socket, while the atlas axis pair forms the pivot joint of the neck.

27. A pivot joint permits

• A. movement in all planes
• B. rotation around a single axis
• C. gliding only
• D. no movement at all

Explanation: In a pivot joint one bone rotates within a ring formed by another, as when the atlas turns on the dens of the axis to shake the head from side to side. All plane movement needs a ball and socket joint instead.

28. A gliding joint, in which nearly flat bone surfaces slide over one another, is found

• A. at the hip
• B. at the elbow
• C. between the carpal bones of the wrist
• D. between the bones of the skull

Explanation: The small bones of the wrist and ankle glide against each other, giving limited but versatile movement. The skull bones are fused and immobile, and the hip and elbow are shaped for much larger movements.

29. Arthritis is the general term for diseases that cause

• A. weakening of the muscles
• B. degeneration of the nerves
• C. inflammation of tendons only
• D. inflammation, pain and stiffness of the joints

Explanation: Whatever the cause, arthritis means an inflamed joint that is painful and stiff. The main types differ in mechanism: osteoarthritis wears cartilage away, rheumatoid arthritis is autoimmune, and gout deposits urate crystals.

30. Which of the following is a common risk factor for osteoarthritis?

• A. Increasing age
• B. A viral infection
• C. Low blood pressure
• D. Excess vitamin D

Explanation: Years of use thin the cartilage and stiffen the joints, so osteoarthritis is commonest after middle age, with obesity and joint injury adding to the risk. It is a wear and tear disease, not an infection.