The Upper Alimentary System

Layers of the Alimentary Canal Mucosa – Mucous Membrane innermost layer adjacent to lumen Primarily epithelial tissue Secretes mucous and other products to aid in digestion. Submucosa Below mucosa Dense connective tissue Contains blood vessels, lymphatic, vessels, nerves

Layers of the Alimentary Canal Muscularis Externa Two layers of smooth muscle to aid in peristalisis and mechanical digestion Serosa Thin, slippery membranes that minimize friction between organs and cavity wall. Also known as peritoneum visceral Parietal Connected together by the mesentery

THE ALIMENTARY CANAL

Accessory Organs/Structures Alimentary Canal Also known as the gastrointestinal tract (gi tract) The tube that runs through the body from the mouth to the anus. 30 feet long and includes the pharynx, esophagus, stomach, small and large intestines. Accessory Organs/Structures Teeth Liver Salivary glands Pancreas Gallbladder

Upper Alimentary/Organs Oral Cavity Ingestion Mechanical breakdown- mastication (chewing) Chemical breakdown- salivary enzymes Propulsion- pushing food back to throat to swallow Teeth, gingiva, tongue, salivary glands, cheeks and lips all assist

Teeth Responsible for mechanically breaking down food Anatomy of Tooth Crown – visible portion doing the chewing, covered in enamel Root – below the gums and bone; anchored to the jaw via ligaments Pulp- Cavity inside tooth with blood and nerve supply Three tissue layers Enamel- Outer most layer of tooth, mineral calcium phosphate similar to bone but much harder Cementum and dentin are underlying tissues within the tooth Periodontium- tissue surrounding teeth Gingiva (gums)- soft Boney socket for tooth to anchor

Salivary Glands Responsible for chemically breaking down food by secreting saliva into mouth Saliva- moistens food, protects mouth and body from infection Water, enzymes, mucous, antibodies Three pairs of salivary glands Parotid Submandibular Sublingual

Pharynx & esophagus The pathway (within alimentary canal) food takes on its way to the stomach from the mouth Pharynx- the throat Esophagus- muscular food tube to stomach peristalsis begins (wave of muscular contraction to push food through the gi tract *** note we share this space with the respiratory system… so don’t get these structures confused!!

Stomach Responsible for mechanically & chemically breaking down food by secreting gastric juices Anatomy of Stomach Cardioesophageal sphincter

Stomach The stomach is basically a reservoir, a holding tank for food and stretches out to hold 2 liters of contents. Food takes a while to break down and must be broken down before entering the small intestine for nutrient absorption. The stomach does most of the heavy work for digestion Rugae- folds of tissue that allow the stomach to expand when full with food Mechanical digestion Lined with three layers of muscles to churn food, continue chopping after the teeth are done Chemical digestion Inner layer of the stomach Simple columnar epithelium that secretes mucus. Gastric pits that secrete juices Hydrochloric acid (HCl) food + gastric juices = CHYME!