Chapter 25 Intestines Small Intestines 3 parts duoudenum 25 cm or 10 in jejunum 1 0 1 7 m ileum 1 6 1 7 m has a large circular folds or pilace most of abdominal cavity Absorption Of Nutrients In The Small Intestine It is inside the small intestine that we absorb most of the nutrients in our food Although the small intestine has a relatively small diameter the intestinal walls are covered in wrinkles called rugae which are themselves covered in millions of finger like projections called villi which are themselves studded with millions of smaller projections called microvilli This provides a surface area of about the size of a tennis court for nutrient absorption Inside each villus is a series of lymph vessels lacteals and blood vessels capillaries The lacteal lymph vessel absorbs digested fat into the lymphatic system which eventually drains into thebloodstream The blood vessels receive other nutrients and transport them via the hepatic portal vein to the liver Here the blood is filtered toxins are removed and the nutrients are processed An important task performed by the liver in this context is the regulation of blood glucose levels to provide sufficient energy for the body Excess glucose is converted in the liver to glycogen in response to the hormone insulin and stored Then when blood glucose levels begin to drop eg between meals the glycogen is re converted to glucose in response to messages conveyed by the hormone glucagon Digestive Function Of The Duodenum The duodenum continues the process of food breakdown Its name stems from the Latin duodenum digitorum meaning twelve fingers or inches It is roughly horse shoe shaped Anatomically it is is sub divided into four segments the superior descending horizontal and ascending duodenum Inside the duodenal tube chyme is mixed with fluids from the gallbladder bile and pancreas pancreatic juice Bile breaks down fat particles into smaller droplets while pancreatic juice contains enzymes that convert fats into fatty acids and glycerol plus sodium bicarbonate to neutralize stomach acid Note during gastric bypass to reduce severe obesity the duodenum is bypassed to reduce the amount of nutrients and calories that can be absorbed Digestive Function Of The Jejunum Roughly 4 7 feet in length the jejunum is where chemical breakdown of the food chyme is completed Pancreatic enzymes along with enzymes produced by the jejunum wall finalize the food digestion process The term jejunum stems from the Latin jejunus meaning empty Note in some gastric bypass operations part of the jejunum is also bypassed to reduce calorie intake Digestive Function Of The Ileum Roughly 7 5 feet in length the ileum is the final section of the small intestine linked to the large intestine by the ileocecal valve The main function of the ileum is to absorb nutrients Bile is also absorbed here and returns to the liver through blood vessels in the intestinal walls The unabsorbed watery remains of the food chyme now pass into the large intestine for water removal and final processing before being expelled from the body