7. Axilla & Upper Limb- Dallar

Explanation
The biceps brachii muscle is a muscle in the upper arm that acts on three joints: the shoulder joint, the elbow joint, and the radio-ulnar joint. This means that the muscle is involved in movements at all three of these joints, allowing for flexion at the shoulder and elbow joints, as well as supination at the radio-ulnar joint. Therefore, the statement that the biceps brachii muscle acts on three joints is true.

Explanation
The skin on the palmar surfaces of lateral 3 ½ fingers is not innervated by the ulnar nerve.

Explanation
The brachioradialis muscle does not flex the wrist. It is actually responsible for flexing the forearm at the elbow joint. It is innervated by the radial nerve, not the median nerve. Therefore, the statement is false.

Explanation
The ulnar nerve is not a component of the cubital fossa. The cubital fossa is a triangular depression on the anterior aspect of the elbow, and it contains various structures such as the brachial artery, median nerve, and biceps tendon. The ulnar nerve, however, does not pass through or innervate the cubital fossa. It travels posterior to the medial epicondyle of the humerus and continues down the forearm. Therefore, the statement is true.

Explanation
The radial nerve is responsible for providing sensory information to the hand, such as touch, temperature, and pain. However, it does not have any motor functions, meaning it does not control any muscles in the hand. Therefore, the statement is true.

Explanation
The statement is true because the median nerve is responsible for innervating the three thenar muscles. The thenar muscles are located in the palm of the hand and are responsible for controlling movements of the thumb. The median nerve runs through the forearm and into the hand, supplying motor and sensory function to various muscles and areas of the hand. Therefore, it is correct to say that the median nerve innervates the three thenar muscles.

Explanation
The statement is false because the cephalic vein actually arises from the lateral side of the dorsal venous arch on the back of the hand.

Explanation
The pronator quadratus is indeed the main pronator muscle. It is located in the forearm and plays a crucial role in pronation, which is the movement that turns the palm of the hand downward. This muscle works in conjunction with other muscles to rotate the radius bone in the forearm, allowing for the pronation motion. Therefore, the statement that the pronator quadratus is the main pronator muscle is correct.