The Digestive System

Nutrition  Nutrition-study of how food affects the function of living organisms.  If cells don’t get nutrients, they don’t function correctly.  Poor diet = poor cells.  There are six general categories of nutrients.

Six Nutrient Categories Organic Macromolecules  Carbohydrates-- energy  Lipids (fats)-- energy storage  Proteins Nutrients  Water  Vitamins  Minerals

3 Factors leading to Nutritional Problems 1) Too little physical activity (sedentary lifestyle) 2) Over consumption of food Leads to obesity 3) Malnutrition/undernutrition

The Digestive System  Responsible for breaking down food so that it can be absorbed by the bloodstream.  Digestion = breakdown Mechanical-large chunks into small chunks by grinding, ripping and crushing by teeth Chemical-larger molecules broken into smaller molecules by enzymes and acid.  The “ALIMENTARY CANAL” is the pathway which food travels through the digestive system.

The Alimentary Canal OORDER OF TRAVEL THROUGH THE CANAL: MMouth EEsophagus SStomach SSmall intestine LLarge intestine RRectum AAnus * The liver, pancreas, and gallbladder are parts of the digestive system but are not parts of the alimentary canal. 26 foot long!!!

The Mouth  Mechanical (chewing) and chemical (saliva) digestion occur in the mouth.  Salivary glands produce saliva, which lubricates food.  Saliva contains enzyme amylase  ***Starch digestion starts here. SUGARS CARBS LIKE STARCH AMYLASE

Esophagus9.8 in  Muscular tube that leads from back of throat (pharynx) to the stomach.  Opening to trachea and esophagus are right next to each other.  Epiglottis prevents food from going down the wrong tube.  Muscular contractions (peristalsis) pushes food down the esophagus, not gravity.

Stomach4 hours  Responsible for protein digestion.  Mechanical digestion—stomach churns  Chemical digestion-hydrochloric acid and pepsin (enzyme) break down proteins into amino acids. (pH )  Sphincter muscles (cardiac and pyloric) control what enters and leaves the stomach.  Stomach lining contains mucus that protects stomach from acid.  Ulcers

Small Intestine  20 ft. long.  Remaining carbs and proteins are broken down.  ***ALL lipids are digested in S.I.  Gall bladder is attached (stores bile from the liver & delivers to the S.I.)

Small Intestine (cont.)  **After nutrients are digested from food, they are absorbed into the blood here.  S.I. contains lots of capillaries for this.  Mesentery—web-like group of capillaries.

Large Intestine  All proteins, carbs, and lipids have been removed from food by the time it gets here.  Water and vitamins in food is absorbed into the blood.  Whatever undigested food is left is “feces” and passes out of the anus.

Liver and Pancreas Secrete Digestive Enzymes LIVER JOBS  Detoxifies drugs and alcohol  Makes and secretes bile, which breaks down lipids.  Bile is stored in the gall bladder. PANCREAS JOBS  Regulates blood sugar.  Releases digestive enzymes into the S.I and neutralizes stomach acid before it enters S.I.

Excretory System  Kidney Cleans the blood, removing waste. Vital role in maintaining homeostasis Regulate amount of water in blood ~1 Liter of urine produced each day.

Kidney Disorders & Treatment  ~ 13 million people suffer from kidney disorders in the US. Kidney stones-uric or oxalic acid, calcium salts, etc. collect outside of kidneys Hemodialysis-  Filtering of blood.  Receive 2x’s a week