Digestive System

There are 400 species of bacteria in the human colon. On average a person passes gas 14 times a day. Constipation is caused when too much water is absorbed in the large intestine and poops become dry. * The small intestine (pronounced in-test-in) is a long tube about 1 and a half to 2 inches around, and about 22 feet long * The large intestine is fatter (3 to 4 inches around), and is about 5 feet long Food stays in your stomach for 2 to 3 hours

Organs of the Digestive System Mouth Pharynx Esophagus Stomach Small intestine Large intestine Anus

Accessory Digestive Organs Salivary glands Teeth Pancreas Liver & gallbladder

Mouth (oral cavity) Incisors Canines Premolars Molars Lips, cheeks, hard/soft palate, uvula, tongue, teeth Food enters mixes with saliva Masticate Incisors Canines Premolars Molars Bolus: chewed & moistened food

Pharynx & Esophagus Pharynx Open area that begins at the back of the mouth Esophagus Runs from pharynx to stomach

Physiology of Mouth, Pharynx, Esophagus Food enters in mouth Physically broken down Mixed with saliva Chemical digestion of starch begins Swallow Voluntary; bolus Peristalsis- rhythmic muscular contractions & relaxations

Stomach Cardiac sphincter Muscle between the esophagus & stomach. Closes to prevent food from reentering the esophagus Pyloric sphincter Between the stomach & small intestine.

Stomach Food breakdown Gastric juice Chemical digestion in the stomach Chyme- food mixed with gastric juice. 30mL Ulcer- Food Propulsion Peristalsis Pyloric sphincter: barely opens & squirts ~3mL of chyme

Stomach Problems Heartburn Cardiac sphincter doesn’t close completely. Ulcers-stomach lining breaks down

Small Intestine Major digestive organ-longest section (~21 ft) Duodenum Jejunum Ileum Structure Villi- fingerlike projections Microvilli- extensions on the villi

Small Intestine Food breakdown & absorption (3-6 hrs) Chemical digestion Brush border enzymes Pancreatic juice Complete starch digestion Half of protein digestion Fat digestion Bile- breaks down large fat globules

Large Intestine Colon Ascending Transverse Descending sigmoid Rectum Anal canal

Large Intestine Contains few nutrients “resident bacteria” Metabolize remaining nutrients Make vitamin K and B vitamins Release gases (500 mL per day) Methane & hydrogen sulfide Feces Undigested food residue, mucus, millions of bacteria, water

Large Intestine Propulsion Mass movements Long, slow-moving, powerful contractile waves (3-4 times a day) Fiber-strengthens contractions Defecation Defecation reflex Anal sphincters

Large intestine problems Diverticulitis-inflammation of diverticula Diarrhea Rushes food before it absorbs water Dehydration & electrolyte imbalance Constipation Stool hard & difficult to pass Lack of fiber; poor bowel habits; laxative abuse