In the kidney, where are the mechanisms found that are responsible for increasing urine concentration?

Acne vulgaris is a common skin condition characterized by various types of lesions, including comedones, papules, and pustules, primarily affecting areas with a high density of sebaceous glands, such as the face, neck, chest, and upper back. Here's why option C is the correct choice:

A) Small, skin-colored, pedunculated papules in areas of skin folds and on other areas as skin tags:

This description is more characteristic of acrochordons or skin tags, which are benign skin growths commonly found in areas of friction or skin folds. Skin tags are not typically associated with acne vulgaris.

B) Hyperpigmented areas that vary in form and color and are slightly elevated from the skin:

This description suggests post-inflammatory hyperpigmentation, which can occur after resolution of inflammatory lesions in acne vulgaris. However, it does not capture the primary pathological findings observed in active acne lesions.

C) Hyperactive sebaceous areas forming comedones, papules, pustules on the face, neck, and upper back:

Correct. Acne vulgaris is characterized by the formation of various lesions, including comedones (open and closed), papules, and pustules, resulting from the obstruction of hair follicles and overactivity of sebaceous glands. These lesions typically appear on areas with a high density of sebaceous glands, such as the face, neck, chest, and upper back.

D) Sharply demarcated silvery scaling plaques with underlying redness on the elbows and knees:

This description is more indicative of psoriasis, a chronic autoimmune skin condition characterized by sharply demarcated, raised, silvery scaling plaques commonly affecting extensor surfaces such as the elbows and knees. Psoriasis lesions are distinct from those seen in acne vulgaris.

Hemodialysis is a renal replacement therapy used to remove waste products and excess fluid from the blood when the kidneys are unable to perform this function adequately. The physiological processes involved in hemodialysis include:

A) Solute movement toward a solution with a higher concentration:

While solute movement occurs during hemodialysis, it is typically from a solution with a higher concentration to one with a lower concentration, rather than the opposite. This movement facilitates the removal of waste products and excess solutes from the bloodstream.

B) Water movement toward a solution with a lower solute concentration:

Correct. Osmosis is the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. In hemodialysis, water moves out of the bloodstream, across the semipermeable membrane of the dialyzer, and into the dialysate solution, which has a lower solute concentration. This process helps remove excess fluid from the body.

C) Blood cells and protein movement through the semipermeable membrane:

Blood cells and proteins are too large to pass through the pores of the semipermeable membrane in the dialyzer during hemodialysis. Therefore, the primary exchange occurs between smaller molecules such as urea, creatinine, electrolytes, and water.

D) Osmosis of water movement and diffusion of solute movement:

Correct. Hemodialysis involves both osmosis and diffusion. Osmosis refers to the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. Diffusion is the movement of solutes from an area of higher concentration to an area of lower concentration. Together, these processes facilitate the removal of waste products and excess fluid from the bloodstream during hemodialysis.