A lacteal is one of the lymphatic capillaries that help to absorb dietary fats in the small intestine. Lacteals were discovered by Gaspare Aselli, an Italian physician, anatomist and surgeon who worked at the end of the 16th century and at the beginning of the 17th century. When a meal is being digested in the small intestine, the lacteals usually take on a white color due to the accumulation of fat globules in their chyle, or lymph. Lacteals are typically found in the villi of the small intestine.
A lacteal's purpose is to move chyle, a type of lymph, through the intestines. This can help to keep lymph circulating through the small intestine. Lacteals can also help to transfer nutrients from the small intestine into the blood stream.
When food is digested, it's generally broken down in the stomach and passes into the small intestine. There, small nutrient molecules typically pass into the villi, which line the intestinal wall. These tiny projections allow nutrients to pass from the small intestines into the bloodstream, where they can nourish the body.
Not all of the nutrient molecules that pass into the villi may enter the bloodstream. Each villus contains a lacteal, or lymphatic capillary, in its center. Many of the dietary fats in digested food enter these lymphatic capillaries. There, the dietary fats typically mix with lymph to form chyle, a particular type of lymph generally produced by the lacteal.
The lacteals then generally transfer the chyle to lymph vessels in the walls of the small intestine. From there, it typically passes into larger lymph vessels which carry it into the cisterna chyli. The cisterna chyli is a chamber that is generally located at the rear of the abdominal cavity. The intestinal and right lumbar lymph trunks typically lead into the cisterna chyli, transferring their lymph from the pelvic region and the lower body. From there, the chyle usually passes through the thoracic duct into the subclavian vein.
At this point, the chyle has most likely transferred the lymph, and the dietary fats it contains, into the blood, where it can typically be converted into lipoproteins, and used as fuel or stored.