During digestion, what is the major site of nutrient absorption?

A. Tubuloglomerular feedback involves the macula densa sensing changes in sodium chloride concentration and adjusting the glomerular filtration rate (GFR) via the juxtaglomerular apparatus.

B. Renal autoregulation includes mechanisms like the myogenic mechanism and tubuloglomerular feedback that maintain stable GFR despite blood pressure changes. This option is too broad and not specific to the mechanism described.

C. The myogenic mechanism refers to the smooth muscle's tendency to contract when stretched, helping to stabilize GFR by adjusting the diameter of the afferent arterioles. This is the correct answer.

D. Sympathetic control influences renal blood flow and GFR through hormonal and nervous system regulation, but it is not the specific mechanism described in the question.

A. Small intestine is the primary site of nutrient absorption. The majority of digestion and absorption of nutrients such as carbohydrates, proteins, and fats occurs in the small intestine, particularly in the duodenum and jejunum.

B. Pancreas secretes digestive enzymes into the small intestine but does not absorb nutrients itself.

C. Stomach plays a role in the digestion of proteins and the mechanical breakdown of food, but it absorbs very few nutrients, primarily alcohol and some drugs.

D. Large intestine absorbs water and electrolytes, but it is not the major site of nutrient absorption. Most nutrients are absorbed before food reaches the large intestine.