Aim: How does digestion take place in humans? A – Mouth B – Esophagus C – Stomach D – (Pancreas) E – Small Intestine F – Large Intestine G – (Gall Bladder) H – (Liver) I - Appendix I

Alimentary Canal – the “tube” digestion takes place in. Gastrointestinal Tract – another name for the digestive system. Gastro = stomach; intestinal = intestines

Four Stages of Food Processing: Ingestion Ingestion – the act of eating or drinking Digestion Digestion – the process of breaking food down into molecules small enough for the body to absorb. Absorption Absorption – cells take up (absorb) the small molecules (Diffusion). Elimination Elimination – (Egestion) undigested material passes out of the body.

Digestion The process by which food products are broken down. Types: MECHANICAL: The physical breakdown of food into smaller pieces (Ex: chewing) CHEMICAL: Enzymes breakdown food into smaller pieces (Ex: amino acids)

Chemical Digestion: Enzymes play a critical role in the digestion (hydrolysis) of nutrients.

Mouth: Intake of food through the mouth! Digestion is both mechanical (teeth and tongue) and chemical (salivary amylase – an enzyme that breaks down starch) digestion occurs. Food mixed with saliva moves to pharynx, and travels down through the esophagus. What keeps the food from going into the trachea (wind pipe)? Epiglottis

Esophagus Process by which muscular contractions move food through the esophagus stomach, small and large intestine Long muscular tube connecting the stomach to the pharynx (upper portion of throat) Peristalsis No Digestion takes place here!

Stomach Both mechanically (churning) and chemically (pepsin) digestion occur. Stomach Glands HCl (Hydrochloric Acid) Acidic pH Kill Bacteria Enzymes Pepsin Digestion of proteins Enzyme specificity Gastric Juice

What is the optimum pH and temperature for pepsin? Optimum pH = 2 Optimum Temp = 40

Small Intestine Responsible for digestion and absorption of nutrients. Most of the Chemical digestion & Absorption of nutrients takes place here.

Small Intestine The enzymes are added to the small intestine are produced by pancreas. Enzymes: Amylase Trypsin Lipase Digests Starch Digests Proteins Digests Lipids These enzymes + a acid neutralizing agent make up the “pancreatic juice”

Absorption The S.I. is ideal for absorption because: -Its very long (about 21 feet) -Many folds/ridges -Has villi (finger like projections)

Villi Blood Vessels Carry Nutrients away from the digestive system to the parts of the body that require them. Nutrients diffuse Into the bloodstream!

Large Intestine Undigested material passes into the L.I No digestion occurs here The major function is to reabsorb water & vitamins. Stores waste (feces) in the rectum. Elimination through the anus. Appendix – vestigial organ.

Accessory Organs Liver Gallbladder Pancreas Make (or store) enzymes, food does not pass through them

Accessory Organs 1.Liver – makes bile 2.Gallbladder – stores and releases bile into S.I. 3.Pancreas – makes and releases (pancreatic juice) amylase, trypsin, and lipase into S.I. along with acid neutralizer.

Bile -Emulsifies fats -Breaks FAT into smaller droplets (mechanical digestion) -Increases surface area of fats

What is the major role of the Digestive System (How doe it help us maintain homeostasis? The digestive system is responsible for breaking down nutrients into smaller components so they can enter our bloodstream & be delivered to our cells & can diffuse across the cell membrane. Polysaccharides Proteins Lipids Monosaccharides Amino Acids Fatty Acids & Glycerlol Cell Diffusion

It's a Gas Scientists estimate that the average adult releases between 12 and 122 cubic inches of intestinal gas each day. Most of that gas is made up of hydrogen and methane produced by the bacteria as they ferment the fiber that was not digested in the stomach or small intestine. Many fruits and vegetables, especially beans, contain these polysaccharides, which cannot be broken down by the enzymes in the stomach or small intestine. As the bacteria decompose these complex sugars, gas is released. Most of the gas is passed without notice. Common wisdom tells us that beans give us a lot of gas— more than could pass without notice. Ever questing for eternal answers, scientists in one study measured the intestinal gas produced by people who ate a control diet and compared them to those who ate a meal that was half pork and beans. The folks in the control group released.9 cubic inches per hour of flatus (intestinal gas) while the pork and beans group released a whopping 10.7 cubic inches.

Weird Science Fact Alexis St. Martin, a French Canadian, was accidentally wounded by a short gun blast in Fortunately, Dr. William Beaumont, an army surgeon, was nearby and began treatment of the wound immediately. St. Martin’s recuperation lasted nearly three years, and the enormous wound healed except for a small opening leading into his stomach. A fold of flesh covered this opening; when this was pushed aside the interior of the stomach was exposed to view. Dr. Beaumont began a series of experiments and observations that formed the basis of our modern knowledge of digestion.