The jejunum is the midsection of the small intestine, connecting the duodenum to the ileum. It is about 2.5 m long, and contains the plicae circulares, and villi that increase its surface area. Products of digestion (sugars, amino acids, and fatty acids) are absorbed into the bloodstream here.
Not to be confused with the cells of the islets of Langerhans, found in the pancreas, or Langhans giant cell.
Melanin= provides some protection against the damaging effects of ultraviolet light. Langerhans cells= found in the epidermis, they alert the immune system to the presence of potentially harmful microbial invaders. Macrophages= found in the dermis, they phagocytize bacteria and viruses that manage to bypass the Langerhans cells of the epidermis.