The small intestine is the part of the gastrointestinal tract where the absorption of nutrients and minerals occurs. Because of that, surface of the small intestine needs to be increased. The inner wall (mucosa) is lined with epithelial tissue and covered with folds called plicae circulares. From the plicae circulares extend finger-like pieces of tissue called villi. The individual epithelial cells of mucosa also contain finger-like extensions-microvilli. Thus, plicae circulares, villi and microvilli are structures that improve absorption by increasing the surface of small intestine.
Muscle fatigue is a common complaint in clinical practice. In humans, muscle fatigue can be defined as exercise-induced decrease in the ability to produce force.
It's because the main photosynthesis component (Chlorophyll) mostly absorbs red and blue portions. It reflects the green portions which is why most plants are green
