Digestion and Absorption

Anatomy of the Digestive Tract
Gastrointestinal tract: flexible, muscular tubing for the mouth to the anus
● Include sphincters, not just organs
Upper esophageal sphincter (UES): upper end of the esophagus
Lower esophageal sphincter (LES): lower end of the esophagus
AKA cardiac sphincter
Pyloric sphincter: separates stomach to the small intestine and regulates flow of partially
digested food

Bolus: the portion of food swallowed at one time

Passage of Food:
● Teeth
● Tongue
● Pharynx
● Epiglottis
● Esophagus

when we swallow, the upper esophageal sphincter opens
● Bolus slides down esophagus through the diaphragm into the stomach, where the lower
esophageal sphincter closes behind it to prevent backflow
● The stomach adds gastric juices that grinds the bolus into semi-liquid mass called
CHYME.

Small Intestine
Chyme then passes through the pyloric sphincter into the small intestine

Chyme passes the opening to the common bile duct, where fluids enter from the gallbladder and
the pancreas

Chyme then passes through the duodenum, jejunum and ileum.
● Digestion is completed here in the small intestine

Large Intestine (Colon)
Chyme passes through ileocecal valve into the colon
The colon withdraws, water, and electrolytes from the chyme
Waste travels to the rectum

Mechanical Digestion
1. Chewing: teeth and tongue
2. Gastric-intestinal motility
a. Peristalsis: begins in esophagus, where propelling and pushing begins
b. Segmentation: mixes and squeezes, forcing contents back a few inches to mix
with digestive juices