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Digestive System

Digestive System. Oral Cavity to Stomach. Oral Cavity (Mouth). Mechanical (Physical) Digestion: Crushing, Grinding, Shearing, Moistening Mouth – where digestion begins – receives the food Teeth – Mechanically breaks down food 32 Adult teeth

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Digestive System

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  1. Digestive System Oral Cavity to Stomach

  2. Oral Cavity (Mouth) • Mechanical (Physical) Digestion: • Crushing, Grinding, Shearing, Moistening • Mouth – where digestion begins – receives the food • Teeth – Mechanically breaks down food • 32 Adult teeth • Tongue – taste buds initiate nerve impulses; manipulates food to form a mass called a bolus

  3. Oral Cavity • Salivary Glands – Secrete saliva (containing salivary amalyase) to break down starch • There are 3 pairs of salivary glands: • Parotid - One below the ears • Sublingual – below the tongue • Submandibular (under lower jaw)

  4. Salivary Glands • When you chew food, you moisten and lubricate it with saliva. • Saliva contains water, mucus and salivary amylase • Starch Maltose (disaccharide) salivary amylase Optimal pH of salivary amylase = 7 • Digestion begins in the mouth even before the food is swallowed • Once food has been chewed, it is called a bolus

  5. Pharynx • A common passage way (throat) for both food intake and air movement • Between the mouth and esophagus • This is where swallowing takes place – it is a reflex action • During swallowing, the nasal air passage is usually blocked off by the soft palate and uvula • The trachea moves under the epiglottis to cover the opening to the windpipe • It is impossible to breathe and swallow at the same time

  6. Esophagus Trachea (windpipe)

  7. Esophagus • Long muscular tube that extends from the pharynx to the stomach • Inner surface is lined with a mucus membrane attached by connective tissue to a layer of smooth muscle (circular and longitudinal muscle) • Peristalsis moves food down the esophagus • Rhythmical contractions of the esophageal muscles • If peristalsis occurs when there is no food in your esophagus, you will feel that there is a “lump” in your throat • No chemical digestion occurs in the esophagus

  8. Cardiac Sphincter • At the end of the esophagus, the bolus arrives at the cardiac sphincter which connects to the stomach • Sphincters function like valves (made of muscle) • Sphincter opens when the muscle is relaxed • Sphincter closes when the muscle is contracted • Usually prevents food from moving out of the stomach • When vomiting occurs, a reverse peristaltic wave causes the sphincter to relax and the contents of the stomach are propelled outward

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