Human Digestive System To be used with Digestive System Guided Notes Gaccione/Bakka Belleville High School

Nutrition Nutrition: process by which organisms obtain and utilize their food Utilizing nutrition - 2 Parts: 1. ingestion- taking in of food 2. digestion- mechanical and chemical breakdown of food so that it can be absorbed and used by the body cells

Types of Feeders Autotrophs- self feeders-make their own food. Example: green plants Heterotrophs- consumers. Depend upon other organisms for their food. Example: Giraffe

Types of Nutrients Nutrients- substances in food that organisms can use –2 types - micro & macronutrients –Micronutrients - nutrients needed in small amounts by an organism examples: vitamins (used as coenzymes to help enzymes) and minerals

Types of Nutrients –macronutrients- nutrients needed in large amounts by an organism Large molecules like carbohydrates, fats, and proteins that require digestion.

Carbohydrates Used for: Energy or energy storage Should constitute 50% of the energy for the body. Found in fresh fruits and vegetables as well as whole grains, pasta & rice. Provide a source of nondigestible materials (roughage or fiber) –stimulates the muscles of the alimentary canal or food tube(esophagus, stomach & intestines)

Fats Used for: –Energy storage –Protection –Insulation –Part of cell membranes Fats contain more potential energy per each unit of their mass then any other major nutrient.

Proteins Used for: –Energy –Growth and repair –Cell membranes –Muscle –Blood (hemoglobin) –enzymes

Other Molecules Water, vitamins, and minerals are small molecules that can be absorbed without digestion

Nutritional requirement Calorie: used to measure the energy in foods –Varies on different types of food Nutritional requirements (amount of calories needed) vary with the human: –1.) body weight –2.) age –3.) activity level –4.) your sex - male or female –5.) natural body efficiency

Chemical Digestion Hydrolysis: the splitting of large, insoluble molecules into small, soluble molecules with the addition of water Regulated by digestive enzymes: –Maltose + water  simple sugars (glucose) –Starch + water  simple sugars –Proteins + water  amino acids –Lipids + water  3 fatty acids + glycerol

Human Digestive Tract Human digestive tract aka Alimentary Canal –consists of a continuous one way food tube Gastrointestinal Tract (GI) –Upper GI - mouth, esophagus & stomach –Lower GI - small & large intestine & anus Peristalsis:Peristalsis -- constriction of the esophagus

Mouth and Teeth Mouth: ingests food 1minute Oral cavity: contains the tongue, teeth, and salivary gland openings Teeth: mechanically breakdown foodTeeth –increases the surface area of the food improves enzyme action

Saliva and Tongue Salivary glands: secretes digestive fluid - saliva –2 Roles of Saliva: 1. Provides lubrication for the chewed food 2. Contains the digestive enzyme amylase that begins the digestion of starch. –Secretion of saliva is stimulated automatically. Tongue: acts as a plunger to push food back into the throat (pharynx)

Esophagus and Stomach Esophagus: 1 minute –10 inch long muscular tube –its muscular walls move food from the mouth to the stomach by peristalsis Stomach: 2 to 4 hoursStomach –muscular J-shaped sac, size of your fist –Protein(pepsin) begins its digestion here –mixes the partially chewed food with gastric juice

Inside the Stomach Gastric juice:Gastric juice –Contains the following: 1. Water: solvent 2. Mucus: lubrication 3. Hydrochloric acid (HCl) pH=2: makes food acidic –Allows the enzyme pepsin to function 4. Pepsin: gastric protease –Begins the digestion of protein in the stomach Acid Reflux Disease: Pepcid AC

From the stomach to the SI Pyloric sphincter: muscular valve between the stomach and the small intestine –regulating the passage of the partially digested mass Food is held 2-4 hours in the stomach. Gastric bypass

Small Intestine - 12 hours –a foot long twisted tube of small diameter (about 1 inch) –lined with enzyme secreting intestinal glands does most of the chemical digestion –chemical digestion of carbohydrates, fats(lipids) & proteins are digested in SI –accessory structures, the liver, gall bladder and the pancreas, empty their secretions into the SI

Accessory Structures of SI Liver: largest body organ –digestive function is to make bile –also produces insulin that breaks down glucose –Disorder: Hepatitis - Hepatitis  inflammation of the liver  transmitted by food or blood

Accessory Structures of SI Gall bladder: small sac beneath the liver that stores bile –Bile emulsifies fats(lipids): breaks down fats into smaller particles. Bile duct: carries bile from the gall bladder to the S.I.

Accessory Structures of SI Pancreas: located near the small intestine –pancreatic juice is carried to the SI by the pancreatic duct –Pancreatic juice secretes 3 enzymes that digests carbs, fats & proteins.

Liver, Gallbladder, and Pancreas not part of the alimentary canal all secrete into the small intestine

Digestion and Absorption of SI Intestinal glands: line the small intestine –secrete intestinal juice –Nearly all digestion occurs in the small intestine & all digestion is completed in the SI. –intestinal juice contains enzymes to breakdown proteins, fats, and carbohydrates

Absorption in the SI Absorption in the SI: –Absorption occurs directly through the wall into blood vessels, without the need for special adaptations. Villi: microscopic fingerlike projections on the SI wall –increase the surface area for nutrient absorption –contain a capillary and a lymph vessel

Villi - a closer look

Absorption in the LI - 5 hours Large Intestine: –Averages 6 feet in length & 2.5 inches in diameter –Sometimes called the colon –No digestion in the LI –Appears as an inverted U surrounding the SI –Undigested food and water enter the large intestine where water is absorbed. Appendix: vestigial organ not needed in human digestion at the beginning of the LI

Removal of Undigested Food Strong peristaltic action forces feces out through the rectum and the anus. Defecation: the removal of fecesDefecation

anus - epiglottis - large intestine - stomach - small intestine mouth - pancreas - appendix - esophagus - gallbladder - liver mouth epiglottis esophagus liver gallbladder large intestine appendix anus stomach pancreas small intestine

Digestive Homeostasis Disorders Ulcers: open sores in the lining of the stomach or the small intestine. Mucus normally prevents ulcers. associated with some kind of irritant or bacterial infection

Digestive Homeostasis Disorders Appendicitis: infection and inflammation of the appendix

Digestive Homeostasis Disorders Gallstones: small hard particles made of cholesterol which form and collect in the gall bladder –may block the bile duct causing pain and discomfort –treated by lasers or surgical removal of the gall bladder

Digestive Homeostasis Disorders Constipation: the feces are evacuated infrequently and with difficulty –Caused by sluggish peristalsis that allows excess water to be removed from the feces (fecal material hardens) –may result from insufficient roughage in the diet

Constipation, cont. Treatment for Constipation:

Digestive Homeostasis Disorders Diarrhea: opposite of constipation - water is not absorbed by the body –caused by infections or stress –prolonged diarrhea = severe dehydration