A patient presents with a red, swollen area on the forearm. Which of the following layers of skin is most likely affected if the inflammation is superficial?

A. Secretion of sebum:Sebaceous glands secrete sebum, an oily substance that lubricates and helps waterproof the skin and hair.
B. Production of melanin:Melanin is produced by melanocytes in the epidermis rather than by sebaceous glands.
C. Protection against UV radiation:Protection from UV radiation is mainly provided by melanin produced by epidermal melanocytes, not by sebaceous gland secretions.
D. Temperature regulation:Temperature regulation is achieved primarily through eccrine sweat glands and cutaneous blood flow, not by sebaceous gland activity.

A. Pivot joint:Pivot joints permit rotational movement around a single axis (for example the atlantoaxial joint) but have limited overall range compared with multiaxial joints.
B. Saddle joint:Saddle joints allow biaxial movement (for example the thumb carpometacarpal joint) and provide greater motion than a hinge but less than multiaxial joints.
C. Ball-and-socket joint:Ball-and-socket joints (such as the shoulder and hip) allow multiaxial movement including flexion/extension, abduction/adduction, and rotation, providing the greatest range of motion.
D. Hinge joint:Hinge joints permit movement primarily in one plane (flexion and extension), giving a more limited range compared with ball-and-socket joints.