Which of the following skin changes is most commonly associated with aging?

A. Thickening of the epidermis:Aging typically leads to thinning of the epidermis rather than thickening, making skin more fragile.
B. Decreased collagen production:Decreased collagen synthesis and fragmentation of existing collagen in the dermis result in thinning, decreased elasticity, and wrinkling with age.
C. Increased sebaceous gland activity:Sebaceous gland activity generally declines with age, often causing drier skin rather than increased oiliness.
D. Increased number of melanocytes:The number of melanocytes tends to decrease with age, though remaining melanocytes can become more irregular and form age spots.

A. Radial groove: The radial (spiral) groove runs along the mid-shaft of the humerus and houses the radial nerve — injury here commonly causes wrist drop and sensory loss on the posterior forearm/hand.
B. Greater tubercle: The greater tubercle is on the proximal humerus and is the site for rotator cuff muscle attachments; it’s not the landmark for mid-shaft nerve injury.
C. Coracoid process: Part of the scapula (anterior shoulder), important for muscle/ligament attachment, not adjacent to the humeral mid-shaft or the radial nerve.
D. Medial epicondyle: A distal humeral landmark near the elbow where the ulnar nerve passes (cubital tunnel) — relevant to elbow/ulnar nerve injury, not mid-shaft radial nerve injury.