Final answer:
The true statement is c. The biceps brachii flexes the elbow and supinates the forearm. The masseter, not the buccinator, is the main chewing muscle and the deltoid is an abductor.
Muscles on the anterior joint generally cause flexion, not extension.
Step-by-step explanation:
The question asks which of the following statements is true:
- a. The chewing muscle covering the ramus of the mandible is the buccinator. This statement is incorrect; the masseter muscle is the main muscle for chewing, not the buccinator.
- b. The prime mover of the arm that acts in adduction would be the deltoid muscle. This is incorrect as the deltoid is the major abductor of the arm, not the prime mover in adduction.
- c. The biceps brachii flexes the elbow and supinates the forearm. This statement is true. The biceps brachii is the prime mover for flexing the elbow and it also supinates the forearm.
- d. During inspiration, the first rib is fixed in place by the splenius muscle. This is incorrect as the scalene muscles, not the splenius, are involved in fixing the first rib during inspiration.
- e. For the upper limb, a muscle that crosses on the anterior side of the joint produces extension. This is incorrect; generally, muscles that cross the anterior aspect of a joint produce flexion, not extension.
Therefore, the correct statement is c. The biceps brachii flexes the elbow and supinates the forearm.