The formation of blackheads on the skin is a result of blockage of which of the following types of gland?

A. The number of hair follicles does not increase with age. In fact, there is a gradual decrease in the number of hair follicles as one ages.

B. Decreased sebum production is a common skin change associated with aging. Sebum helps keep the skin moisturized, and as its production decreases with age, the skin tends to become drier.

C. Skin elasticity actually decreases with age due to the breakdown of collagen and elastin fibers, leading to wrinkles and sagging.

D. Epidermal permeability tends to increase with age, as the skin becomes thinner and more fragile, making it easier for substances to pass through.

A. Flexion refers to a bending movement that decreases the angle between two body parts, such as bending the knee or elbow, but it does not involve lateral movement away from the body's midline.

B. Adduction is the movement of a body part toward the midline of the body, opposite of what the question describes.

C. Extension refers to a straightening movement that increases the angle between two body parts, such as straightening the arm or leg, but again does not involve lateral movement.

D. Abduction is the correct term for moving a limb or body part away from the midline of the body. In this case, it refers to the lateral movement of the leg away from the body's midline.