Tham khảo tài liệu 'sat ii biology episode 2 part 1', ngoại ngữ, ngữ pháp tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | ANIMALS STRUCTURE AND FUNCTION Kidney The metabolism of proteins for example produces toxic substances harmful to body tissues and must be gotten rid of. It is important to distinguish between the elimination that is achieved in the digestive system and the excretion done in this system. Material that passes entirely through the system is finally eliminated from the body as a passive act. What ends up in the lower large intestine is material that is left over after all the other nutrients have been acted on. It is not gathered and deposited there as an active process of excretion performed on materials such as proteins and carbohydrates it just happens to end up there. On the other hand excretion is a homeostatic event with several systems working in concert to actively gather the substances necessary to maintain homeostasis and excrete those harmful substances from the body. The metabolism of proteins produces nitrogen wastes most predominantly ammonia. This is coupled with carbon dioxide in the liver and is neutralized or made less harmful in the form of urea. Nephron Transported to the kidneys blood is filtered out in units called nephrons that house the main filtering structure Bowman s capsule and tubules. In the nephrons substances needed by the body are reabsorbed into the vascular system. Substances not needed by the Peterson s SAT II Success Biology E M 7 CHAPTER 7 body are excreted. Mediated by hormones and other chemical factors the resulting mix that has been selectively separated is passed to the bladder through the ureters where it is stored until it will be excreted from the body through the urethra. Comparative Unicellular organisms simply pass their nitrogenous wastes through their plasma membrane by diffusion and maintain water balance by osmosis. Annelids filter and collect these wastes in nephridia that connect to the outside environment. Arthropods collect nitrogenous wastes in structures called Malpighian tubules and then .
