Which of the following is the smallest muscle in the human body?

Question

UnlockIAS · Accepted Answer

Correct — C, Stapedius. The stapedius is the smallest skeletal muscle in the human body, roughly one millimetre long. It lies inside the middle ear, arising from the pyramidal eminence of the tympanic cavity and inserting on the neck of the stapes — the smallest bone in the body. It is the effector of the acoustic (stapedial) reflex: when a very loud sound arrives, the stapedius contracts, stiffens the ossicular chain and damps the vibration passed to the inner ear. It is supplied by the nerve to stapedius, a branch of the facial nerve (cranial nerve VII), which is why a facial-nerve lesion above that branch can cause hyperacusis — ordinary sounds becoming painfully loud.

Why the other options are wrong — (a) The biceps brachii is a large two-headed muscle on the front of the upper arm that flexes the elbow and supinates the forearm — one of the most visible muscles in the body, nowhere near the smallest.  (b) The exact opposite superlative: the sartorius is the LONGEST muscle in the human body, a strap muscle running diagonally across the thigh from the hip bone to the inner side of the knee. Papers pair it with stapedius precisely to catch a half-remembered fact.  (d) The triceps brachii is the three-headed extensor at the back of the upper arm and is bulkier than the biceps — again a large limb muscle, not a candidate for the smallest.

Concept: Sound reaches the inner ear through a chain of three tiny bones in the middle ear — malleus, incus and stapes. Two muscles control that chain: the tensor tympani (supplied by the trigeminal nerve, CN V) and the stapedius (supplied by the facial nerve, CN VII). Both work as a protective damping system for loud sound. Because the whole assembly is built at millimetre scale, the middle ear holds both the body's smallest bone (stapes) and its smallest skeletal muscle (stapedius).

State PCS 2025 Q64 — Science & Technology PYQ with Answer

State PCS 2025 Q64 — Science & Technology PYQ with Answer