Chapter 22 Study guide answers 1. •The digestive system takes in food, breaks it down into nutrient molecules, absorbs these molecules into the bloodstream, and then rids the body of the indigestible remains. •Digestive system organs fall into two main groups: the alimentary canal and the accessory organs. oThe alimentary canal, or gastrointestinal (GI) tract, is the continuous muscular digestive tube that winds through the body digesting and absorbing foodstuff; its organs include: the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. oAccessory digestive organs aid digestion physically and produce secretions that break down foodstuff in the GI tract; the organs involved are the teeth, tongue, gallbladder, salivary glands, liver, and pancreas. 2. 1. Ingestion - food into mouth 2. Propulsion - moves food through canal; peristalsis 3. Mechanical Digestion - chewing, mixing, churning, segmentation of small intestine 4. Chemical Digestion - food molecules are broken down by enzymes 5. Absorption - passage of digestion products from the lumen of GI into blood or lymph 6. Defecation - elimination of substances from the body 3. •Mucosa is the innermost, moist, epithelial membrane that lines the entire digestive tract. It secretes mucus, digestive enzymes, and hormones; absorbs digestive end products into the blood; and protects against infectious disease. •Submucosa is a moderately dense connective tissue layer containing blood and lymphatic vessels, lymphoid follicles, and nerve fibers. •Muscularis externa typically consists of smooth muscle and is responsible for peristalsis and segmentation. •Serosa, the protective outer layer of the intraperitoneal organs, is the visceral peritoneum. 4. •Mouth is a stratified squamous epithelial mucosa-lined cavity with boundaries of the lips, cheeks, palate, and tongue oThe lips and cheeks have a core of skeletal muscle covered externally by skin that helps to keep food between the teeth when we chew and plays a small role in speech.
oThe palate forms the roof of the mouth and has two parts: the hard palate anteriorly and the soft palate posteriorly. oThe tongue is made of interlacing bundles of skeletal muscle and is used to reposition food when chewing, mix food with saliva, initiate swallowing, and help form consonants for speech. oSalivary glands produce saliva, which cleanses the mouth, dissolves food chemicals for taste, moistens food, and contains chemicals that begin the breakdown of starches.
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