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Digestion The breaking down of food molecules for use by body cells – Types: Mechanical— physically breaking down large food particles into smaller food.

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Presentation on theme: "Digestion The breaking down of food molecules for use by body cells – Types: Mechanical— physically breaking down large food particles into smaller food."— Presentation transcript:

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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

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7 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

8 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

9 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

10 Teeth

11 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 Teeth

12 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

13 Digestion in Mouth Mechanical: mastication – AKA chewing Chemical: salivary amylase – Breaks down starch

14 Pharynx Common pathway for food and air Skeletal muscle lined by mucous membrane

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

16 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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