The diagram shows a high-magnification schematic representation of a liver sinusoid and its associated structures.
Which of the following rows correctly identifies one of the labelled structures and describes its role in excretion or homeostatic control?
Structure: P (Bile canaliculus)
Role: Transports bile containing excretory products, such as bilirubin, away from the sinusoid to eventually be eliminated via the digestive tract.
Structure: Q (Sinusoid lumen)
Role: Transports oxygenated blood directly from the renal artery to supply hepatocytes for high-rate aerobic respiration.
Structure: R (Podocyte)
Role: Performs selective reabsorption of glucose and amino acids using secondary active transport with sodium ions.
Structure: S (Kupffer cell)
Role: Undergoes deamination of excess amino acids to form toxic ammonia, which is then converted into urea via the ornithine cycle.