Lesson 1 Transport and Defense Chapter 7 Lesson 1 Transport and Defense

Body’s Organization Groups of organs work together in an Organ system The organs systems work together to maintain homeostasis Homeostasis- maintaining constant internal conditions when external conditions change

Digestion The body needs nutrients and substances from food Digestion is the process that breaks down food into small molecules so they can be absorbed and moved into the blood. Two types of Digestion Mechanical Chemical

Mechanical Digestion Food is chewed, churned, mixed, grinded etc. Major organs that use mechanical digestion are the teeth, mouth, and stomach

Chemical digestion Chemical reactions occur that break down large molecules of food into smaller molecules There are several enzymes that help digestion An enzyme is a special protein that speeds up a chemical reaction but does not get used up or changed in the reaction Ex- amylase in saliva

Organs of Digestion Digestive Tract Mouth Esophagus Stomach Small intestine Large intestine Rectum Anus Accessory organs Tongue Teeth Salivary glands Liver Gall bladder Pancreas

Mouth Both mechanical and chemical digestion Food is chewed, grinded, and made into smaller pieces with the help of the tongue (mechanical) Saliva mixes with the food to moisten it and to start the breakdown of carbohydrates (amylase and chemical) Saliva is produced by three sets of glands

Esophagus The tongue has pushed the food into the back of the mouth The epiglottis covers the trachea or windpipe so food does not pass into the lungs. The esophagus is a muscular tube that pushes the food into the stomach by wave like contractions called peristalsis Mucus lines the esophagus to keep the food moist No Digestion

Stomach Both Mechanical and chemical digestion Muscular bag that churns and mixes the food (mechanical) Mixed with enzymes and hydrochloric acid Hydrochloric acid works with an enzyme, pepsin, to break down proteins The acid also kills bacteria Stomach also produces mucus which protects the stomach from the acid and makes the food slippery

Chyme Thin, watery liquid mixture of food, acid, and enzymes

Small intestine Only chemical digestion About 30 feet in length Small diameter compared to the large intestine Most digestion occurs in the upper portion called the duodenum. Greenish chemical, bile from the liver, is mixed here Bile emulsifies fat Sodium bicarbonate ( baking soda) is added to neutralize the stomach acid

Small intestine The pancreas makes the sodium bicarbonate and also produces insulin important in the regulation of the amount of glucose in your body Absorption of nutrients occurs here Villi- small finger- like projections increase the surface area for absorption of nutrients

Large intestine It is important for the absorption of water Peristalsis slows down so water can be absorbed The material becomes more solid and remains here until it is released from rectum and anus

Accessory organs Teeth- chewing Tongue- moving food to the back of the throat Salivary glands- produce saliva Liver- produces bile Gall bladder- storage for bile until needed Pancreas- makes enzymes, sodium bicarbonate, and insulin for glucose regulation