Functions of the Digestive System

1. Functions of the Digestive System • Ingestion (bring food in) • Occurs when materials enter digestive tract via the mouth • Mechanical processing (Crushing and shearing) • Makes materials easier to propel along digestive tract • Digestion • The chemical breakdown of food into nutrients • Absorption • Movement of nutrients through digestive tract wall into the bloodstream. • All materials that sustain and build your body come from your nutrition • Excretion • Removal of waste products from body fluids

2. Accessory Organs Figure 16-1

3. Oral Cavity • Food first enters the digestive system through the mouth. • In the mouth the teeth break apart the food and saliva mixes with the food. • Saliva: fluid secreted from salivary glands that contains enzymes to break apart food, saliva is about 99% water. • Once the food is swallowed it moves downthe esophagus. • Hollow tube that moves food toward the stomach. • Swallowing causes the epiglottis to close, protecting the airway. • Tissue flap that blocks food from entering larynx

5. The Stomach • Once in the stomach the food mixes with stomach acid. • Stomach: organ that stores food- mechanical and chemical digestion. • Chyme: food mixed with stomach acid. • The chyme that leaves the stomach moves into the small intestine. • Small intestine: main function is nutrient absorption. • Chyme moving into the small intestine mixes with fluid from the pancreas, liver and gall bladder.

6. Accessory Organs • Pancreas: is an organ that releases digestive enzymes, that break down food into nutrients. • Remember also releases insulin • Liver: organ that makes bile. • Bile is a fluid that is made to break apart fatty foods. • Gall bladder: organ that stores bile made by the liver. • Once the chyme, mixes together with enzymes from the pancreas, and bile from the liver and gall bladder it moves through the small intestine. • What allows for the nutrients to be absorbed is intestinal villi.

7. Small Intestine • Intestinal villi: increase surface area inside the intestines which increases nutrient absorption.

8. Large Intestine • Processed food leaves the small intestine and moves through the large intestine. • Large Intestine: organ where water reabsorption occurs. • Once all the nutrients and water have been removed waste product leaves through the rectum and anus. • Anus: external opening where waste product is removed. Animation

9. Disorders • Appendicitis: inflammation of the appendix. • Gall bladder removal: when the gall bladder does not work properly it can be removed. • The liver will then just make and release bile when needed.

10. Part 2 Excretory system

11. Main Function Excretory • Main function of the excretory system is the removal of water and wastes. • While the digestive system removes solid waste the kidneys remove water wastes from the blood (salts, ions, etc.) • Main organs: Kidneys • Kidneys: filter the blood and remove waste or drugs in the blood. • Regulate ion concentration, pH, and blood pressure by controlling how much water is removed and how many solutes are left in the blood. • Filtration: the process of removing unwanted products from the blood. • The functional units that filter the blood are called nephrons.

13. Excretory System • The fluid that is filtered from the blood leaves the kidneys and then goes through the ureters. • Ureters: tubes that move urine from the kidneys to the bladder. • Bladder: hollow organs that stores urine. • Can house up to 2 cups of urine. • The urine then leaves the bladder through the urethra.

14. Dialysis • If the kidneys are not working properly the process of dialysis can be done to work as a “fake kidney”. • Dialysis: • Removes waste, salt and extra water. • Keeps safe levels of certain chemicals in your blood. • Helps to control blood pressure.