BioBit – The small intestine, digestion and absorption all in one.

Your small intestine is a long coiled tube located just below your stomach. It is the longest part of your digestive tract, totalling around 6.9 metres (22 feet) in length. This tremendous amount of tissue is needed to digest and absorb the nutrients from you food. Your small intestine is made up of 3 parts:

  1. Duodenum: first 25cm of your small intestine. Shaped like a ‘C’, it receives the digestive juices from your pancreas and bile from you gall bladder. This is where the majority of digestion occurs.
  2. Jejunum: midsection of your intestine is about 2.5m long and is important in the absorption of the nutrients from your food.
  3. Ileum: final segment of your small intestine that is important in absorbing vitamin B12 and nutrients that may have gotten past the Jejunum.

Your small intestine is lined with over 3,000,000 small finger like projections called Villi (see below) that act to increase the surface area available for digestion and absorption of nutrients. Each of these villi is also covered in around 600 smaller projections called microvilli which further increase the surface area. In fact, the surface area of your small intestine is equivalent to that of a tennis court!


BBC Bitesize. The Intestines – Higher Tier

Chyme (Food + Acid) is moved through your small intestine by rhythmic contractions of smooth muscle that circles the tubes. This motion is called peristalsis and is the same movement that occurs in your esophagus when you swallow food. The pancreatic juices that are secreted into the Duodenum also contain bicarbonate (baking soda) which acts to neutralize the stomach acid. This protects the intestine from damage but also makes sure the enzymes in the pancreatic juices are turned on.

Your small intestine also plays a role in harbouring beneficial bacteria that aid in educating your immune system.

One thought on “BioBit – The small intestine, digestion and absorption all in one.

  1. Pingback: BioBit – The large intestine is your waste treatment plant. | Science Translation

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