Urea Production Site in Mammalian Physiology

Steps:

• Recall urea forms via the urea cycle to detoxify ammonia from protein breakdown.
• Note the urea cycle enzymes are exclusively in liver hepatocytes.
• Examine diagram labels to locate the liver structure.
• Select the label pointing to the liver.

Why D is correct:

• Urea synthesis occurs in the liver through the ornithine-urea cycle, converting toxic ammonia to excretable urea.

Why the others are wrong:

• A likely labels the kidney, site of urea filtration but not production.
• B probably indicates the bladder, for urine storage only.
• C may point to the ureter, involved in urine transport, not synthesis.

Final answer: D