When a water-soluble nutrient molecule has been absorbed and has crossed into the cell of a villus, it enters the bloodstream and is guided to the liver.
Villi are the finger like projections specialized for absorption in the small intestine. They are connected to the blood vessels so that the nutrients are carried by the circulating blood. The water soluble nutrients from the villi reach the bloodstream and liver is the primary organ for receiving the nutrients from the GI tract. The portal vein carries the nutrients to the liver before being transported to the cells of the body. The nutrients are checked by the liver for the presence of toxins and filters the blood before reaching the cells. Thus, liver acts as a first line of defence to prevents the toxins entering the cells of the body.
The huge surface area of the small intestine helps in absorption of nutrients. The water-soluble nutrients and small fats enter the bloodstream directly. The inner surface of the small intestine comprises hundreds of folds of compositions known as villi. Within the villi, there are numerous microscopic projections known as microvilli.
The microvilli substantially enhance the surface area of the small intestine that upsurges the rate of absorption of nutrients. Upon entering the bloodstream the water-soluble nutrients are directed towards the liver prior to being transported to the cells.
Just 5% to 10% of the sunlight they receive gets converted into energy. So if humans are going to photosynthesize, we'd better get good at it. We would probably evolve to become a lot bigger to absorb enough light to feed and grow.
