Sean Munroe5/3/15Period 7Chapter 15 Objectives (1-14)

1. The main function of the digestive system is digestion. There are two types of digestion, mechanical and chemical. Mechanical digestion is the process of breaking large pieces of food into smaller ones(doesnt alter chemical composition). Chemical digestion breaks food into simpler chemicals.2. The digestive system consists of the alimentary canal which consists of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus. The accessory organs include the salivary glands, liver, gallbladder, and pancreas.3. The alimentary canal wall consists of four distinct layers. The innermost layer is the mucosa, then the submucosa, muscular layer, and serosa.4. The contents of the alimentary canal mix when smooth muscles in small segments of the tube contract rhythmically. Propelling movements include a wavelike motion called peristalsis. When peristalsis occurs, a ring of contraction appears in the wall of the tube. Simultaneously, the muscular wall just ahead of the ring relaxes. As the peristaltic wave moves along, it pushes the tubular contents ahead of it. 5. In your mouth you have cheeks, lips, a tongue, a palate, and teeth. Your cheeks contain muscles associated with expression and chewing. Your lips contain skeletal muscle and and sensory receptors useful in judging temperature and texture of food. The body of your tongue is mostly skeletal muscle. These muscles mix food particles with saliva during chewing and moves food toward the pharynx during swallowing as well as underneath the teeth for chewing. There are also taste buds within the papillae of the tongue which provide friction to handle food. Your palate helps you in swallowing because swallowing draws the soft palate and uvula upward in order to close the opening between the nasal cavity and pharynx. Your teeth begin the process of mechanical digestion which increases the surface area of the food particles causing enzymes to be able to work more efficiently. 6. There are different types of teeth which are thus designed for different functions. Your incisors have sharp edges that bite off large pieces of food. Your cuspid(canine) teeth grasp and tear food. Your bicuspid(premolar) teeth grind food particles. Your molars also grind food particles.7. There are many parts of the teeth. There are two main portions, your crown which projects beyond the gum, and your root which is anchored to the alveolar process of the jaw. Glossy, white enamel, which is made of calcium salts is the hardest substance in the body. Underneath the enamel is dentin. Dentin encloses the pulp, which contains a combination of blood vessels, nerves, and connective tissues8. Serous cells produce a watery fluid that contains the digestive enzyme amylase. Amylase splits starch and glycogen molecules into disaccharides--the first step in the chemical digestion of carbohydrates. Mucous cells secrete a thick liquid called mucus which binds food particles and lubricates during swallowing.9. When a person sees, smells, tastes, or even thinks about pleasant food, parasympathetic nerve impulses elicit the secretion of a large volume of watery saliva;Vice-Versa(This also explains number ten).10. See number 9.11. Gastric enzymes break down proteins, but the stomach wall is not well adapted to absorbing digestive products. The stomach absorbs only small volumes of water and certain salts as well as alcohol and some lipid soluble drugs.12. A person can usually initiate a defecation reflex by holding a deep breath and contracting the abdominal wall muscles. This action increases internal abdominal pressure and forces feces into the rectum.13. Carbohydrates are ingested in a variety of forms including starches from grains and vegetables; glycogen from meats; disaccharides from cane sugar, beet sugar and molasses; and monosaccharides from honey and fruits. Lipids are found in meats, eggs, milk, lard, palm oil, and coconut oil. As well as seeds, nuts, and plant oils. Proteins are found in meats, fish, poultry, cheese, nuts, milk, eggs, and cereal. Legume, including beans and peas , contain lesser amounts. 14. Carbohydrates are utilized to catalyze the formation of glucose from fructose and galactose. Lipids are utilized primarily to supply energy. Proteins are utilized to supply essential amino acids.