The Digestive System

The Digestive System: Function Preparation of food for absorption and use by the millions of body cells Alimentary canal - tube through your body that performs the above function.

The Mouth Structure Lips: outer boundary Cheeks: mucous membrane lateral boundary Hard/soft palate - uvula extends from Tongue

Tongue Places food during chewing Papillae contain taste buds Multiple blood vessels under tongue = high absorption of soluble drugs into circulation Ex. Nitroglycerin pills for heart attack, Vitamins

Salivary Glands Parotid = largest Submandibular Sublingual = smallest Located in front of and below ear Produces watery substance with enzymes Submandibular Located below mandibular angle Produces enzymes and mucus Sublingual = smallest Under floor of mouth Produces mucous type of saliva

Salivary Glands: Function Begins the break down of food through hydrolysis. Carbohydrate digestion begins in the mouth with aid of saliva.

Teeth Crown - exposed covered with enamel Neck - surrounded by gums (gingiva) Root - fits into socket

Teeth Coverings Enamel - Hardest substance in body Dentin - tissues, nerves, blood vessels Cementum - covers dentin

Dentition Deciduous Teeth 20 total Baby teeth Primary teeth 8 incisors 4 cuspids 8 molars

Dentition Permanent Teeth 32 Total Adult teeth Secondary teeth 32 Total 3rd set of molars come in after age 17 (wisdom teeth)

Other Organ Components Pharynx Receives bolus (rounded mass of food) Carries bolus to esophagus Esophagus Collapsible tube that enters the stomach Posterior to trachea and heart Protected by a thick layer of mucus

Esophagus Continued Food (Bolus) moves through the esophagus and the rest of the alimentary canal by peristalsis - involuntary muscle contractions.

Stomach Located below diaphragm and liver Enlarges after meals then collapses Size of large sausage

Stomach Divisions Fundus - large portion at end of esophagus Body - central portion Pylorus - lower portion near small intestine

Sphincter Muscles Guard openings to stomach Cardiac - esophagus to stomach Pyloric - lower portion of stomach to small intestine. Pylorospasm - muscle will not relax to allow passage of bolus = vomiting

Stomach Function Food storage Secretion of gastric juices Churning of food and breakdown into chyme - liquid food. Absorption = water, alcohol, and drugs Glands of stomach Gastric - secret gastric juice Mucus - contains enzymes and hydrochloric acid.

Small Intestines 20 feet long Divisions Duodenum = uppermost area, attaches to stomach. Jejunum = middle area Ileum = end portion, leads to large intestine. All set in place by mesentery (membrane)

Small Intestines Continued This is where most digestion occurs. Absorption of digestive products. Inside surface of small intestines covered with tiny projections called villi. 1mm projections Increase surface area by 160x

Large Intestines 5-6 feet long Divisions Ascending colon - right side of abdomen Transverse colon - horizontally across abdomen and under liver Descending colon - left side of abdomen Rectum - last 7-8 inches Anus - contains many arteries and veins Hemorrhoids - enlargement of veins in anal canal.

Large Intestines Continued Water/electrolyte absorption Forms/stores feces

Large Intestines Continued Appendix Located just behind cecum No functional importance in digestion. Appendicitis = inflammation of the appendix

Accessory Organs Liver structure Liver function Largest gland in body Under diaphragm Able to regenerate Liver function Detoxifies many substances Makes and secretes bile Metabolizes proteins, fats, and carbs

Accessory Organs Gall bladder Stores bile, increases its concentration Bile breaks down fat. During digestion, empties bile into small intestines

Accessory Organs Pancreas Secretes digestive enzymes Secretes insulin Secretes glucagon (raises blood glucose levels)