The large amount of digestion occurs here.
Food passes into small intestines from stomach by the “pyloric sphincter“.
The diameter of the small intestines is smaller then large intestines – hence the name
However the small intestines is almost 5 times longer then the large intestines
- Duodenum – on average – 10 inches long
- Jejunum – on average – 8 feet long
- Ileum – on average – 11.5 feet long
- The function of muscles to cause a wave-like contraction in order for food to move in a certain direction
- The inner walls of the small intestines is lined with rugae or plicae circulares.
- These are wrinkles that allow a greater surface area and absorption occurs.
- Secreation of enzymes and other molecules allow for nutrients to pass from the intestines into the blood stream.
- The Jejunum allows for the larges extent of absorption.
The following are absorbed else where:
- Iron [Duodenum]
- Water [Everywhere]
- Lipids [Everywhere]
- Vitamin B12 [Terminal Ileum]
- Bile Salts [Terminal Ileum]
- Sodium [Active transport]
- Glucose [Co-transport]
- Amino Acid [Co-transport]