Which organ is responsible for excreting urine and is located high in the back of the abdominal cavity?

The kidney is the organ responsible for excreting urine, and its position in the body is indeed high in the back of the abdominal cavity, specifically located towards the posterior side of the abdominal cavity against the muscles of the back. Each kidney has a renal pelvis where urine collects before it moves down into the ureters and eventually into the bladder for storage. The primary function of the kidneys involves filtering blood to remove waste products and excess substances, thereby producing urine.

Other organs listed do not fulfill this particular function. The bladder is a storage site for urine, not an organ that produces or excretes it. The liver is primarily involved in metabolic processes and detoxification, and while it does produce bile, it is not directly involved in the excretion of urine. The spleen plays a role in the immune response and the recycling of red blood cells but has no function related to urine formation or excretion. Thus, the kidney is the correct answer, highlighting its crucial role in the urinary system.