The Digestive System! :D Zane Smith

Homeostasis and Interdependence The Digestive System is necessary for maintaining homeostasis because it breaks food down into means of energy that can be used by cells. The nutrients provided from food is transported to cells all around the body.

Forms of Digestion Mechanical Digestion Chemical Digestion Physical breakdown of food due to movement of organ Ex. Chewing and Stomach movement Chemical Digestion Breakdown of food facilitated by enzymes Ex. Stomach acids

Evolution of the Digestive System Incomplete Digestive Tract No specialized organs/parts. Only a single orifice for food intake and food waste. Ex. Planarians – Digestive cavity takes up majority of internal volume. Cells receive nutrition through Diffusion Complete Digestive Tract Contains specialized organs/parts. Has a mouth for food consumption and an anus for food waste. Ex. Annelids

Evolutionary Adaptations with Diet Dentition (Teeth) Different types of teeth are attributed to diet Carnivores – Pointed and jagged teeth for tearing/cutting/scraping food Herbivores – Sharp anterior teeth for clipping, flat posterior teeth for chewing/crushing food Omnivores – Combination of the two; flat posterior teeth, sharp and pointed anterior teeth

The System 1. Mouth 2. Esophagus 3. Stomach 4. Small Intestine 5. Large Intestine 6.Anus 7. Uhhhh… 8. Pancreas 9. This guy can’t count 10. Liver http://www.youtube.com/watch?v=sCn5uvvc3WE

Organs of the Digestive System Mouth/Oral Cavity Beginning of the digestive tract Saliva Amylase breaks down starch into maltose When food (bolus) is swallowed, the soft palate of the mouth closes off the nasopharynx (The opening of the nasal cavity) The epiglottis covers the opening of the Tracheal passage.

Organs of the Digestive System Pharynx – Where the Tracheal and Esophageal passages separate. Esophagus – Tubular structure that transports food into the stomach by way of Peristalsis. Food passes the Gastroesophageal sphincter Stomach – Thick-muscled organ that breaks down food into Chyme. It contracts vigorously and excretes enzymes and acids. Pepsin – Excreted by the stomach with Hydrochloric acid to convert protien into peptides.

Organs of the Digestive System Small Intestine – A long tubular organ that facilitates the absorption of nutrients and the breakdown of fats. Juices from the liver and pancreas are mixed into the small intestine. Maltase – Produced by the small intestine which breaks down maltose into glucose. Peptidase - Breaks down peptides into amino acids

Organs of the Digestive System Small Intestine (continued) The intestine has a large surface area which is increased by Villi. Nutrients are absorbed through villi. The Outer layer is composed of columnar epithelial cells. Each cell is covered in microvilli and contains intestinal enzymes. Sugars and amino acids enter the blood stream within the villi. Glycerol and fatty acids are absorbed into a lymphatic capillary after being converted into lipoprotein droplets

Organs of the Digestive System Large Intestine – Long, tubular organ similar to the small intestine. It absorbs water from what’s left over of the food to create waste, which is stored until it can be removed through the anus. No digestion happens here.

Accessory Organs to Digestion Pancreas – Regulates glucose in the blood and creates enzymes necessary to digestion. Pancreatic Amylase - digests starch into maltose in the small intestine Trypsin - digests protein into peptides in the small intestine Lipase – digests fat from fat droplets, that were emulsified in the small intestine, into glycerol and fatty acids.

Accessory Organs to Digestion Liver – Large gland that filters blood, stores iron and vitamins, helps maintain glucose in the blood, and creates bile for digestion in the small intestine. Bile – Emulsifies fat and breaks down proteins. Appendix – Small organ attached to the large intestine. May serve to fight infection, but is generally seen as a vestigial organ Gallbladder Stores bile produced by the liver

Diseases of the Digestive System Appendicitis Infection of the appendix. Can cause nausea, vomiting, fever, swelling, and even death if untreated. Can be easily treated and removed through surgery. Irritable Bowel Syndrome Digestive distress caused by stress or an irregular diet. Can cause pain and discomfort, but doesn’t worsen Barrett’s Esophagus Damaged esophageal cells (caused by excessive acid damage or infection) mutate into columnar cells. This causes strictures in the esophagus that have to be removed through surgery