Digestive System [Day 1] Note: can do the crackers etc demo

Main Ideas Mouth  stomach

1. Mouth Starting point! Saliva – lubricates food & esophagus; moistens food Mechanical Digestion – when teeth cut & grind food into smaller pieces Chemical Digestion – salivary amalase begins to breakdown starch into maltose

1. Mouth

Swallowing Tongue rolls food into ball (“bolus”) – moves to back of pharynx Soft palate closes off nasopharynx; epiglottis covers opening to trachea My Swallow Study(1).mp4 Swallowing (deglutition) from Anatomy _ Physiology Online.mp4

2. Esophagus Once food enters, peristalsis begins Muscle contractions, move bolus to stomach “do the wave” 

3. Stomach Esophagus  cardiac sphincter  stomach Sphincter = muscular ring; valve Prevents back flow! Esophagus Cardiac Sphincter Duodenum Stomach Pyloric Sphincter

3. Stomach

3. Stomach Bolus mixes with gastric juices  “chyme” Lining of stomach has gastric pits Secrete gastric juices Has pepsin, HCl, mucus Pepsin: enzyme to breakdown proteins HCl: kill pathogens; convert pepsinogen to pepsin Mucus: protect stomach lining from chem. digestion Pepsin = chemical digestion HCl – kills bacteria/pathogens; converts pepsinogen to pepsin Mucus – protects walls from acid and pepsin

3. Stomach Gastrin Hormone Stimulates secretion of HCl Triggered by high protein meals

Ulcers Helicobacter pylori – helix shaped; literally screw itself into stomach lining to colonize Infects mucosal linings – prevents mucus production No mucus – hole! REALLY common! [2/3 population has colony?]; only when populations increase enough do you have symptoms may be asymptomatic for long time becoming antibiotic resistance [b/c common treatment] Spicy foods often increase uclers  reduces lining b/c more acidic  make H. pylori’s job easier

Ulcers Mucus normally is replaced every few days Helicobacter pylori Bacteria, infects mucus lining of stomach Thrives in highly acidic environment! If no/low mucus  acid & pepsin start to break down stomach!

To Do’s Questions [next slide] Provincial questions!! #5, 9, 17, 19, 20, 23, 25, 27, 28, 30, 44 Dictionary Mechanical digestion; chemical digestion; bolus; chyme; peristalsis; sphincter; gastric juices; ulcer Q’s?

Questions Why is saliva important? Why do the epiglotis and nasopharynx need to close before swallowing? Why are sphincters important? Why is it important the esophagus is soft and flexible, unlike the trachea? Where do we find bolus? Chyme? How are they different?