of Overview Digestion
FCS 2472C M. Burns, PhD, RD
Review
CPH vs. famine Solutions to world hunger Cause of food insecurity in U.S. Nutrition transistion
Digestive System
Two functions digestion and absorption Other names GI tract, alimentary canal, gut Mouth Anus Figure 33, pg. 69
Mouth
Entry point for food Saliva salivary amylase lubricates mouth and moistens the food forms the bolus (moistened mass of food)
Pharynx
Responsible for swallowing the bolus During swallowing Epiglottis blocks airway and the bolus enters the esophagus Dysfunction results in choking
Esophagus
Connects the pharynx to the stomach Peristalsis wavelike contractions that propel the mass through the gut Lower esophageal sphincter
Functions of the stomach
Temporary storage site Bolus is mixed with gastric juices to form chyme Gastrin, a hormone, triggers the release of hydrochloric acid (HCl)
Hydrochloric acid (HCl)
Stops CHO digestion Kills most bacteria in the food Activates the enzyme pepsinogen for protein digestion Mucus protects the stomach from the acid Gastric ulcers
Food for thought
macronutrient Which is digested first?
Emptying times of stomach
Chyme normally leaves stomach in 26 hours depends on size and macronutrient composition of meal Phyloric sphincter
3 Sections of small intestine
Duodenum some digestion continues Jejunum absorptive functions Ileum
What happens here?
Acidic chyme mixes with pancreatic juices controlled by two hormones: secretin and cholecystokinin Bile aids in fat digestion Bicarbonate neutralizes the acidic chyme Pancreatic enzymes
Structure of small intestine
Villus microvilli or brush border blood capillaries absorbs watersoluble nutrients to liver lacteals absorbs fatsoluble nutr...