Human Anatomy and Physiology Transport and mixing of food in the alimentary tract
Dec 28, 2015
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)