Anatomy & Physiology

Anatomy & Physiology Study Guide • The division rate of epithelial stem cells declines. The digestive epithelium becomes more susceptible to damage by abrasion, acids, or enzymes. • Smooth muscle tone decreases. General motility decreases, and peristaltic contractions are weaker as a result of a decrease in smooth muscle tone. • The cumulative effects of damage to the body begin to become more apparent, for example, loss of teeth due to poor dental hygiene. • Cancer rates increase. Colon and stomach cancer tend to rise due to age whereas oral, esophageal, and pharyngeal cancers are particularly common among elderly smokers. • Dehydration is common among the elderly. Because osmoreceptor sensitivity declines with age, dehydration is common among the elderly. • Changes in other systems have direct or indirect effects on the digestive system. 23.16 Chapter Twenty-Three Review The digestive system has overlapping functions for the usage of food: • The digestive system is made up of the muscular gastrointestinal tract and various accessory organs. • Double sheets of peritoneal membrane, called mesenteries, suspend the digestive tract. The greater omentum lies anterior to the abdominal viscera. Its adipose tissue provides padding, protection, insulation, and an energy reserve. • The lamina propria and epithelium form the mucosa (mucous membrane) of the digestive tract. Proceeding outward is the submucosa, the muscularis externa, and a layer of areolar tissue called the adventitia. Within the peritoneal cavity, the muscularis externa is covered by a serous membrane called the serosa. • The muscularis externa propels materials through the digestive tract by the contractions of peristalsis. Segmentation movements in the small intestine churn digestive materials. • Neural reflexes, hormones, and local mechanisms control digestive tract activities. The oral cavity contains the tongue, salivary glands, and teeth, and each has a designated function: • The oral cavity's (buccal cavity) function is for sensory analysis of foods; mechanical processing by the teeth, tongue, and palatal surfaces; lubrication, by mixing with mucus and salivary gland secretions; and limited digestion of carbohydrates and lipids. • Oral mucosa lines the oral cavity. The roof of the oral cavity is formed by the hard and soft palates, and the floor is formed from the tongue. • Hypoglossal nerves control the intrinsic and extrinsic tongue muscles. • The parotid, sublingual, and submandibular salivary glands discharge their secretions into the oral cavity. • Contact of the occlusal (opposing) surfaces of the teeth creates mastication (chewing) of the bolus. The periodontal ligament anchors each tooth in an alveolus, or bony socket. The basic structure of the tooth is formed by dentin, enamel coats the crown, and the cementum coats the root. Achieve Page 325 of 368 ©2018