Concept:The skin serves as an accessory excretory organ, with the sweat gland responsible for removing metabolic wastes.
Explanation:Metabolic wastes are harmful by-products formed inside body cells during processes like respiration and protein breakdown.
These wastes include excess water, salts, and nitrogenous compounds such as urea.
The sweat gland is a coiled tubular structure found in the dermis of mammalian skin.
It filters waste materials from the blood and secretes them as sweat.
Sweat contains water, sodium salts, and small amounts of urea.
The sweat passes through the sweat duct and reaches the skin surface through pores.
This process removes nitrogenous waste from the body, making the skin an excretory pathway.
Sweating also assists in temperature regulation by cooling the body through evaporation.
The horny layer is the outermost protective layer of dead cells; it plays no role in excretion.
The Malpighian layer is the germinative layer that produces new skin cells.
The sebaceous gland secretes sebum, an oily substance that keeps the skin and hair lubricated.
Thus, only the sweat gland excretes metabolic waste products.
Answer:A. sweat gland