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Digestive System

Digestive System. Digestion. The breaking down of food molecules for use by body cells Types: Mechanical — physically breaking down large food particles into smaller food particles Chemical — chemical reactions that break down into usable molecules. Digestive Functions.

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Digestive System

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  1. Digestive System

  2. Digestion • The breaking down of food molecules for use by body cells • Types: • Mechanical— physically breaking down large food particles into smaller food particles • Chemical— chemical reactions that break down into usable molecules

  3. Digestive Functions • Ingestion: taking food into the body • Movement: transportation of food throughout the body • Deglutition: swallowing • Peristalsis: moves material through digestive tract; wave like contractions of smooth muscle • Absorption: bringing usable molecules into the bloodstream • Mixing: combining substances together to form one mass • Churning: to make a substance through agitation • Secretion: lubricate, liquefy, digest • Defecation: elimination of unused substances

  4. Names of Digestive System • Continuous tube from the mouth to anus • Approximately 30 feet long • Known as: • Digestive system • Gastrointestinal (GI) tract • Alimentary canal

  5. Four Layers of Tissues • Mucosa: innermost, mucous membrane • Submucosa: vascular, holds mucosa in place • Muscularis: smooth muscle to move food • Serosa: outermost layer continuous with the mesentery

  6. Mouth • Oral cavity: opening surrounded by hard & soft palate, teeth, cheeks, tongue • Lips: lined with mucous membrane and covered with skin • Labial frenulum— attaches lips to gums • Uvula— prevents food from entering the nasal cavity when swallowing

  7. Mouth • Tongue— skeletal muscle covered with mucous membrane • Shapes chewed food with saliva into a ball— bolus • Lingual frenulum— limits tongue movement • Papillae— cover surface and sides of tongue

  8. Salivary Glands • Parotid: under skin in front of ears • Submandibular: under base of tongue and below mandible • Sublingual: under anterior portion of the tongue • Saliva: 99.5% water, 0.5% other stuff • Salts—to buffer chemicals • Mucin—with forms mucous with matter • Lysozyme—kill bacteria • Amylase—starch digesting enzyme

  9. Teeth

  10. Teeth • Dentin-is a tissue that is calcified and consists of tiny tubules or tubes. It is the second layer of the tooth and is normally covered by enamel and covers the pulp, making up the majority of the tooth's structure. • Enamel - the first layer of tooth that is visible in the mouth, is a porous, calcified substance made from crystalline calcium phosphate. Enamel appears to be a soft beige to white color, yet it is semi-translucent allowing the color of the dentin layer to penetrate through. Enamel is also the hardest substance in the body. • Pulp- the most vital part of the tooth, the pulp originates in the center of the tooth, underneath the enamel layer and dentin layer, in the pulp chamber. The pulp contains blood vessels, connective tissue, and large nerves. The pulp, also commonly referred to as the nerve, branches out and continues down each root through the canals of the tooth and stops just shy of the apex, or tip of the tooth. • Crown- visible portion of tooth • Root- portion of tooth underneath the gum • Periodontal membrane (aka periodontal ligament)- connective tissue deep to the cementum that connects to bones or cartilages, serving to support and strengthen the joint between the tooth and the gum • Cementum- a layer of tough, yellowish, bone-like tissue that covers the root of a tooth. It helps hold the tooth in the socket

  11. Teeth • Ability to chew food—mastication • 2 sets of teeth in lifetime • Deciduous teeth-baby teeth • Permanent teeth-32 adult teeth • Types of teeth • Incisors • Canines • Premolars • Molars

  12. Digestion in Mouth • Mechanical: mastication • AKA chewing • Chemical: salivary amylase • Breaks down starch

  13. Pharynx • Common pathway for food and air • Skeletal muscle lined by mucous membrane

  14. Esophagus • Muscular tube that lies closed behind the trachea • Transports food to stomach • Secretes mucous to lubricate and aid transport

  15. Deglutition (swallowing) • Voluntary stage: tongue pushes bolus into pharynx • Pharyngeal stage: involuntary; soft palate & uvula close off nasal passage, epiglottis seals the larynx; breathing is interrupted • Esophageal stage: food is pushed down by waves of muscular movements called PERISTALSIS

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