Layers of the Small Intestine

Layers of the Small Intestine


In this video we’ll be talking about
the major layers of the small intestine As well as the modifications the GI
tract that allow for optimal absorption of nutrients.
Covering most portions on the GI tract is a connective tissue of visceral
peritoneum referred to as the serosa. The serosa provides a route for
blood vessels and nerves well encasing the small intestine
and allowing it to stay stationary but also slide along other surfaces
without creating much friction as it secretes serous fluid that
lubricates its own surfaces. Serosa is not found throughout the entire
GI tract however. Instead there is dense connective tissue found in areas such as the esophagus and
rectum. The next layer deep to the serosa is the muscularis externa which is
comprised mainly of smooth muscle. There are two layers of this muscle
within the small intestine: an inner circular layer and an outer longitudinal
layer The coordination of the contraction of
these layers is very important in the movement of
food throughout the tract or peristalsis as well as the processing and mixing of food with enzymes within the
tract which is known as segmentation. Beneath the muscular layer is the
submucosa this layer is mainly made up of dense
connective tissue and contains large blood vessels, lymphatic vessels as well as the
submucosal nerve plexus which is important in the regulation
of muscular contraction of the small intestine. The mucosa is made up of epithelial cells and
is crucial for the absorption of nutrients. If we look more closely at the mucosa we will see that there are some
modifications that increase the ability of an individual to absorb nutrients. First off, the small intestine has many
circular folds which allow for an increased surface area.
This is important as an increased surface area for
absorption means more nutrients will get into our bloodstream. Furthermore, along these folds are villi which are small, finger-like
structures that project into the lumen of the small intestine. These increase our ability to absorb even more. If this wasn’t enough, there are
also microvilli carpeting the surface of each villis which increase the surface area to and even
greater extent. These microvilli form what is known as
the brush border and also secrete enzymes to break down
any exposed foods. The epithelial cells may than absorb the
nutrients.

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