Human Anatomy and Physiology

Transport and mixing of food in the alimentary tract

Food reception

Mastication Teeth

Incisors, canines (55 lb, cutting and tearing) Premolars and molars (200 lb, grinding)

Grind and breakdown food Stimulate saliva production Mix food with saliva

Process of deglutition

Esophagus Upper sphincter

Ensures breathing commences Lower sphincter

Prevents acid reflux (heartburn)

Food passage takes about 9 seconds

Stomach Anatomy

Cardiac sphincter

Stomach

Motor functions Receptive relaxation Food storage (1.5 L) Gastric peristalsis Slow emptying

Gastric motility Slow waves and spike potentials

Regulation of gastric motility

1. Stomach i. Volume of chyme

Smooth muscle excitability ii. Presence of protein

Gastrin release from antral mucosa

Regulation of gastric motility

2. Duodenum i. Distention of the duodenum ( ) ii. Acidity of duodenal chyme ( ) iii. Presence of protein, sugars and fats cause

hormones to be released from duodenal mucosa (gastric inhibitory peptide GIP, secretin)

Small intestine Mixing and propulsive contractions

combined (segmentation)

Control of motility in small intestine

Neural: slow waves Hormonal

Up-regulatory: gastrin, CCK, secretin, insulin Down-regulatory: glucagon

Ileocecal valve

Function Prevent backward flow

Operation Opens upon pressure

differences

Large Intestine

Motility Rhythmical: every 30 minutes Mass movement: coincides with ileum

contraction (follows a meal)

Large Intestine anatomy Tenia coli Haustra alter their location

Defecation Contraction of abdominal wall musculature and lowering of

diaphragm places pressure on colon wall. External and internal sphincters open (nervous system)