How many phalanges are there in the hallux?

Correct Answer: B

Rationale: The hallux (big toe) has 2 phalanges (proximal and distal), like the thumb, unlike the other toes, which have 3 (proximal, middle, distal), due to its structural role.

Correct Answer: B

Rationale: The sliding filament theory describes how muscle contraction occurs when actin and myosin filaments slide past each other, shortening the muscle. This process happens within the sarcomere, the functional unit of contraction between Z-lines in a myofibril. While myofibrils contain sarcomeres and myosin heads facilitate the sliding, the theory specifically applies to the sarcomere level, making 'Sarcomeres' the correct answer.

Correct Answer: C

Rationale: Irregular bones, like the vertebrae, have complex shapes and primarily function to protect internal organs. The vertebrae form the vertebral column, which encases and protects the spinal cord, a critical nervous system component. While some bones produce blood cells, protection is the primary role here, making 'Protecting internal organs' the correct answer.

Correct Answer: B

Rationale: Compact bone, also called cortical bone, is the dense, hard outer layer of bone tissue that provides strength and structural support. Spongy bone (with trabeculae) is lighter and found inside, often in the epiphysis, but 'compact bone' specifically denotes the dense type, making 'Dense and hard' the correct answer.

Correct Answer: D

Rationale: The neuromuscular junction is the synapse where a motor neuron contacts a muscle fiber, releasing acetylcholine to initiate contraction. Sarcoplasm is muscle cytoplasm, myofibrils are contractile components, and sarcomeres are within myofibrils, making 'Neuromuscular junction' the correct answer.