Nutrition and Digestion

The importance of microflora in digestion:

The Gastrointestinal tract or GI:  GI tract contains many organs involved in digestion

Purpose of Digestion  To breakdown food so it may be absorbed by the body for energy  Digestion begins in the mouth  Bolus- a mass of chewed up substance  Passes to the back of the throat the pharynx down the esophagus and into the stomach

The oral cavity  Lips protect the mouth  Mechanical digestion-tongue and teeth  Chemical digestion-salivary glands  Taste buds-determine if foods are sweet, sour salty or bitter  Teeth-incisors (for tearing), canines (for grasping and tearing) and molars (grinding)  Salivary glands- contain saliva which contains the enzyme amylase (breaks down starch)  The name of the starch that is broken down by amylase is?

The Tooth  Enamel- hardest substance in the body  Dentin- under the enamel  Pulp cavity- center of the tooth  Contains nerves and blood vessels

Esophagus and Stomach:  The bolus is squeezed through the digestive tract by rhythmic muscular contractions called peristalsis.  A sphincter muscle keeps food from going back into the esophagus from the stomach.  Mechanical churning of the food and chemical digestion of enzymes and acids

The stomach:  Hydrocholoric Acid (HCl) is produced in the stomach  HCl activates pepsin an enzyme that breaks down proteins  Food being chemically digested is call chyme

The small intestine  Where most digestion and absorption of food occurs  Enzymes come from the intestine, pancreas and liver  The inside folds over 7 meters of the intestine of little finger-like projections called-Villi  Villi increase the surface area for absorption by the capillaries (micrograph on the right are the villi of the small intestine)

Digestive accessory organs:  The liver is a large brownish organ the lies above the stomach and below the diaphragm in the abdomen  The liver produces bile (emulsifies fats)  Bile is secreted through the bile duct into the small intestine  Bile is stored in the gallbladder  Gallbladder- saclike organ

Pancreas  Under the stomach  Produces hormones, starch, and enzymes that are secreted into the small intestine  Insulin  Glucagon  lipase

Large Intestine  When food leaves the small intestine it passes to the large intestine or Colon (highlighted)  The main purpose of the colon is to remove water from indigestible waste and produce feces  The colon also has bacteria that helps digest and produce vitamins like vitamin K

Digestive Enzymes Small intestine Amylase Maltase Lactase Sucrase Lipase Stomach Pepsin Pancreas Amylase Lipase Trypsine Chymotripsine Carboxypeptidase