The Digestive System Presents:

 Digestion begins with your imagination!  As soon as you see, smell, or even imagine food, our salivary glands begin to prepare by producing saliva.  Physical or mechanical digestion begins in the mouth.

 In the mouth, two types of digestion occur:  Physical or mechanical digestion  Teeth shred, tear, and grind food  Food is formed into a bolus (Greek for “ball”) by the tongue  Chemical digestion  Saliva contains the enzyme salivary amylase

 The first step in the digestion of food  There are 32 teeth in a normal adult (from front to back) EACH OF TOP, BOTTOM, LEFT, RIGHT incisors canine (cuspid) pre-molars (bicuspids) molars Flat, blade- like Long, sharpWide, flatWider, flat 2123 Biting/cutting Shredding/ tearing GrindingCrushing 2 incisorsx 4 = 8 1 caninex 4 = 4 2 pre-molarsx 4 = 8 3 molarsx 4 = 12 (includes 4 wisdom teeth) = 32

 Parts of a tooth  Crown – the visible part of the tooth  Root – the anchor of the tooth that extends into the jaw bone  Enamel – the tough, white, shiny outer surface  Dentin – hard but porous tissue; harder than bone  Pulp – soft centre of tooth; nourishes dentin  Cementum – layer of tough, yellowish, bone-like tissue covering root of tooth; helps to hold tooth in socket  Nerves and blood vessels – transmit signals to and from the brain (hot, cold, pain, etc)

 Begins chemical digestion with the enzyme salivary amylase  Amylase starts to break down carbohydrates, starches, and sugars  Saliva also lubricates food so it does not scratch the mucous membranes of the alimentary canal  It also dissolves food particles and activates your taste buds

 Saliva is produced by 3 salivary glands:  Parotid gland  This is the largest salivary gland and is located in front of and below the ears  Submandibular gland  Located at the floor of the mouth near the rear of the cheeks  Sublingual gland  Located at the floor of the mouth underneath the tongue

 After the food has been torn, shredded, ground, and moistened by the teeth and saliva, it is formed into a ball-like mass called a bolus  To swallow, the tongue is elevated against the top of the palate and propels the food down the throat  During swallowing, a flap of cartilage called the epiglottis folds back to cover the entrance to the larynx to prevent food and drink from entering the windpipe, and food continues it’s trip to the anus.

 This is a long, thin tube tube with muscular walls  Muscles contract rhythmically in a movement called peristalsis which move the bolus and fluids along the digestive tract  This contraction is involuntary and independent of gravity

 Also called the esophageal sphincter  When it’s contracted, it closes the opening to the stomach  When it’s relaxed, food is allowed to enter  Gets its name from being close to the heart  It’s also helpful in preventing reflux or heartburn

 Caused by a physiological process by a sudden jerk in the diaphragm that causes you to breathe in  The hiccup sounds are made by the vocal cords (glottis)  Eating too fast  Air to stomach  Movement of stomach acid into the esophagus  Metabolic disorder (renal failure)