What increases within the sinusoids when the portal vein carries blood into the liver?

When the portal vein carries blood into the liver, one of the primary functions is the transport of nutrients absorbed from the digestive tract. These nutrients are delivered to the liver where they can be processed, stored, or converted into forms that the body can use effectively.

The sinusoids, which are specialized capillaries in the liver, become enriched with various nutrients as blood flows through them. These nutrients include glucose, amino acids, and other substances that originate from food intake. The liver plays a vital role in metabolizing these nutrients, including the regulation of glucose levels and the synthesis of proteins.

While oxygen is also present in the blood, the portal vein is not a significant source of oxygen as it primarily carries nutrient-rich blood rather than oxygen-rich blood from the lungs. Likewise, carbon dioxide levels are generally not influenced by the blood entering the liver via the portal vein, as carbon dioxide is a metabolic waste product rather than a nutrient. The increase in glucose is a part of the overall increase in nutrients, but glucose specifically is only one type of nutrient sourced from the portal vein.

In summary, the correct answer emphasizes that a variety of nutrients, collectively, increase in the sinusoids, facilitating the liver's essential metabolic functions.