From the Mouth to the Stomach

I. Mouth parts – last class… Pharynx A. common passageway for food & air B. muscles that push bolus toward esophagus) ( longitudinal/ circular peristalsis) Peristalsis! C. initiates swallowing = deglutition D. part of swallowing is a reflex ; uvula stimulated by bolus and epiglottis covers glottis so food doesn’t go “down the wrong tube” III. Esophagus A. hollow muscular tube- 25 cm long and 2 cm in diameter B. carries food/ liquid to stomach C. Acid Reflux = back flow of acids in esophagus $$ industry!

IV. Stomach (J shaped) A. mechanical and chemical digestion B. soupy mixture of food is now called chyme C. Draw Fig. 15.11 pg. 411. Label the following parts 1. cardiac sphincter a.k.a. (lower esophageal) - circular muscle near heart 2. fundus 3. body 4. pyloric sphincter- circular muscle near belly button D. ruggae = “wrinkles” that permit expansion and Increase surface area.

Stomach!

More about the stomach! In the stomach E. longitudinal, circular and oblique muscles to assist in churning chyme F. Gastric glands and pits with specialized cells that produce HCl ( hydrochloric acid) 1. pH of HCl = 1.5 – 2.0 2. has to be produced in separate ions b/c otherwise it is too strong! 3. functions of low pH a. kills bacteria in food b. denatures proteins c. breaks down connective tissue in meats d. activates pepsin which digests proteins! 4. peptic ulcer = HCl erodes stomach lining

G. Gastric Activity 1. triggered by… sight, smell, taste, anger, hostility 2. decreased by… anxiety, stress, fear 3. 1 hr. after eating contractions are like a washing machine 4. “churning” decreases as pH increases due to buffers being added 5. meals with alcohol, caffeine, and little protein leave stomach quickly 6. 1-2 hrs. after a meal, pepsin digests proteins, amylase  carbs, and lipase  lipids 7. food is broken down in stomach, but no absorption b/c cells are not permeable to water 8. alcohol can be absorbed in the stomach 9. prolonged aspirin use can lead to bleeding in the lining of the stomach