The Big Job of the Small Intestine

Previously, we left our hypothetical meal in a semi-digested state, just ready to leave the stomach for the small intestine. That image may seem unappealing to our brains, but to our bodies, this is just perfect.

The intestine is made up of two components: the small intestine, which starts at the stomach, and connects to the large intestine, which ends at the anus. The small intestine is broken up into main sections. The first section is the duodenum, which completes the job of breaking down food by combining the stomach's contents with enzymes secreted by the pancreas and the gallbladder. The second section has two parts: the jejunum and the ilium, and they are used to absorb the nutrients and fats left from food digestion.

Because each section has different roles, they have slightly different makeups. The entire intestine has a sheath of smooth muscle which is lined by a mucosal layer. The mucosal layer is the site of nutrient absorption, so it needs as much surface area as possible. As a result, the interior layer is highly textured, almost like ruffled fabric and the entire surface is covered in tiny projections called villi. The villi act like little toll-booths, bringing the nutrients from the interitor intestinal space into the bloodstream.



Word Nerd fact: the word "duodenum" references it's length. The term comes from the Latin word "duodecim", which means "12" (duo = two, decim = 10). This was used because the breadth of twelve fingers is the approximate length of the duodenum, which is 25 cm. They must have used a big guy for that measurement: I needed 3 extra fingers to get the same length.