How do we process food prior to delivering it to the stomach? 4/20 What organs make up the digestive system? How does the tongue help with digestion? What is mastication and how does dentition process food in the oral cavity? How does saliva help process food in the oral cavity? What is deglutination and why is GERD such a problem today? What are the anatomical features of the stomach? How is information delivered to the stomach and leave the stomach?

The digestive system consists of several organs that break up food, swallow, enzymatically digest nutrients in chyme, propel these materials from the mouth to the anus, and absorb nutrients into the blood. Overview:

Digestion starts with food ingestion, gustation, and mastication in the oral (buccal) cavity. It all starts with taste! 4 types of tongue taste bud: front-back/Left-right Unami is the fifth “taste” Sweet-energy Salt-sodium Sour-acidic Bitter-alkaline/poison Palatability and ingestion: Flavor-Aroma-Texture As we age we become less able to taste and smell! Importance for hypertension and anorexia in elderly?

Mastication: We use teeth, tongue, lips and cheeks to begin the mechanical aspects of the digestive process. Mechanical function of tongue lingual muscles, lips and cheeks: The Parts of a Tooth: Enamel Dentin Pulp Cavity Root Canal Alveolar Bone Occlusion: Occlusal Surface: Cusps:

We will normally have 20 deciduous ‘milk’ teeth. After the age of 6, these are replaced by 32 (4X8)permanent teeth that provide for us in adulthood. Adults: 32 Permanent Teeth Each Quadrant has 8 teeth: 2 incisors-cut 1 canine-hold 2 premolars-sheer 2 molars-grind 1 ‘Wisdom’ tooth The last to erupt! Bones: Maxilla or Mandible 4X Quadrants= 32 teeth Infants: 20 Deciduous Teeth As the permanent teeth erupt, they push the deciduous teeth out of their sockets! “Teething”

How does a lack of oral health hamper good nutrition and digestion? Dentition determines if you eat, grind, digest, talk, and even sleep efficiently! Who is susceptible to problems? Why? Plaque: –Calculus or Tartar –Flossing and brushing Caries: –Digestive enzymes and acids –Grinding Out and Fillings as a solution Root Canal Therapy: –Pulp replacement –Infection removed Gingivitis can lead to Peridontal Disease? How is tooth loss related to our diet in the USA, Third World, and in Prehistoric Peoples?

We produce saliva (1.5 L/day) for 3 reasons: 1) Lubrication/moisture of food during mastication 2) Mix enzymes for digesting bacteria, starch and lipids 3) Addition of NaCO 3 - for control of acidity/tooth decay Parotid (20%): Serous Sublingual (5%): Mucous Submandibular(70%): Mixed Minor glands (5%) Saliva Contents: Water: Main Content! Electrolytes:K+, Cl-, NaCO 3 - Proteins: Mucin and IgA Enzymes active only at pH 7: Lingual amylase Lysozyme Lingual Lipase  active in stomach Bites often bring infection! WHY?

Deglutination: the tongue presses a food bolus against the palate, through the fauces, into the pharynx, past the epiglottis and into the esophagus. Then peristaltic waves of smooth muscle squeeze it into the stomach as the cardiac sphincter relaxes. Activity coordinated by swallowing center of medulla:22 muscles Three Stages to Swallowing: 1) Buccal > 2) Pharyngeal > 3) Esophageal Entry into esophagus (skeletal then smooth muscle) creates a peristaltic wave in the muscularis externa that generates propulsion by shortening and narrowing the tube right-behind the bolus! Enteric Nervous System allows for conduction of depolarization along smooth muscle cells resulting in a wave of contraction! Finally: Lower esophageal sphincter must relax (dilate) before bolus can pass through the cardiac orifice into the stomach!

Gastro Esophogeal Reflux Disease (GERD)is a huge problem for many people! Have you seen adds for the “Purple Pill called Prilosec”?

Stomach: Provides for Mixing, Acidification and Sterilization

There are several important anatomical structures on the stomach that you should be aware of. Why are these clinically significant? Location inferior to the diaphragm and left lung Esophageal sphincter and diaphragm Pyloric sphincter Pyloric Canal Fundic, Cardiac and Pyloric Regions and the “Body” Greater and Lesser Curvatures Converting ingested material into Chyme: Gas and the cause of indigestion:

The layers of the stomach are all responsible for specific functions,,,what are these layers? Serosa: (formerly called adventitial layer on esophagus) Muscularis Externa: three smooth muscle layers –Longitudinal –Circular –Oblique –Provide mixing across three different orientations Submucosa: Contains blood vessels and nerves Mucularis mucosa: tiny muscle layer under mucosa Mucosa: Contains arterioles, venules, capillaries, lymphatics, gastric pits/ducts, stomach does huge amount of work here! (ATP production required!) Epithelial layer  protection!

It is also important to remember that a layer of protective glycocalyx coats and protects all underlying simple columnar epithelial cells from acids!

How do we bring information, oxygen, nutrients, and blood into or out of the stomach? Blood: Enters via gastric branch of celiac trunk artery Exits via hepatic portal vein for cleaning of blood toxins in liver Information: Enters via two nerves: –Vagus Nerve: parasympathtic info to stomach –Vagus Nerve also carries sensory info from stomach to brain –Sympathetic fibers of celiac ganglion Hormones: Gastrin: output hormone to blood CCK, GIP and Secretin: Input hormones from blood Lymphatics are also very important for fluid drainage/inflammation!

What digestive materials are secreted by the stomach and how do we protect ourselves against them? Stomach makes acids, pepsin and huge amounts of mucus Importance of mucus: PROTECTION OF EPITHELIUM! Importance of stomach acid: Antibacterial Digestion Nutrient availability Problem with stomach acids: Potential self digestion: stomach, esophagus, duodemum Potential enzyme de-activation due to pH Importance of Pepsin: Break up proteins and Deactivate potential hazards Potential to autodigest your own body Solution: activation only in acidic pH What happens to pepsin activity if “Tums” are taken?