The Digestive System The mysterious process uncovered!

The Beginning ► ► Oral cavity:   Both physical and chemical digestion takes place in the mouth. ► ► Saliva:   secreted to moisten food,   protect the mouth from abrasions   buffer against acids in food, kill some forms of bacteria   begin carbohydrate digestion with the enzyme SALIVARY AMYLASE. ► ► Tongue:   is used for taste, manipulates food while chewing and   prepares food for swallowing by forming it into a ball called a bolus.

Down the hatchet (or Pharynx and esophagus)! ► ► Pharynx   Commonly called the throat.   Intersection of the glottis and opening to the esophagus is found here.   Epiglottis is a flap that closes the glottis when the act of swallowing occurs. ► ► Esophagus   Connects the pharynx and the stomach.   Peristalsis, wave-like contractions of the smooth muscles push food down toward the stomach.

Into The Stomach ► ► J shaped expandable organ located on the left side of the abdominal cavity. ► ► Stores up to 2 liters of food while mixing and digesting it. ► ► secrete GASTRIC JUICES and HCl making the pH around 2 very acidic ► ► The hormone GASTRIN is secreted by the stomach cells to regulate the production of gastric juices. ► ► Fat Digestion: Bile emulsifies fat. This creates a larger surface area for the enzyme lipase to digest it. ► ► Carbohydrate Digestion: Disaccharide digestion is under the control of the enzymes maltase, lactase, sucrase, all of which are mainly found in saliva.

Stomach Photo

Small Intestine and Villi ► ► It is more than 6 meters in length with smaller diameter than large intestine. ► ► It is divided into 3 sections: duodenum, jejunum, and ileum ► ► Pancreas, Liver, and Gall Bladder:   accessory organs, add digestive enzymes, juices and hormones into the small intestine.   Pancreas-helps digest starch and protein digestion   Gall bladder-storage for bile which helps digest fats   Liver-secretes bile for fat digestion and filters blood of toxins

Absorption ► ► Absorption and distribution of nutrients:   Small intestine is lined with small finger-like projections called Villi   The nutrients except fat are absorbed into the capillaries, while the fat enters the lacteal.   All the contents of the blood enter the liver The liver regulates the contents of the blood.

Pancreas and Villi

Large Intestine ► ► Colon is connected to the small intestine at a T junction called the cecum.   The appendix is found attached to the end of the cecum. ► ► The main function of the colon is to reabsorb water from the small intestinal material. ► ► The bacteria Escherichia coli live in this area of the body. They produce odor, and Vitamin K. ► ► Waste is excreted through the rectum and out through the anus

Now, who’s hungry? ► Digestion Transit Times:   Mouth: ► ► one minute   Esophagus: ► ► two to 3 seconds   Stomach: ► ► 2-4 hours   Small Intestine: ► ► 1-4 hours   Large Intestine: ► ► 10 hours to several days! ► Digestion is now complete, time to eat again! ► Review rubric for digestion t-shirt and digestion creative writing assessment!