DIGESTIVE SYSTEM

Chapter 3

• Digestion is the mechanical and chemical breaking down of food into smaller components, to a form that can be absorbed, for instance, into a blood stream. Digestion is a form of catabolism; a break-down of macro food molecules to smaller ones.

• Responsible for the intake, digestion of food, absorption of nutrients, and elimination of solid waste.

• Alimentary Canal (GI tract)• Aliment/o - to nourish

Anatomy/Physiology

Accessory Digestive Organs

• Teeth• tongue• salivary glands• liver• gallbladder• pancreas

Oral Cavity

• Mouth (bucca, tongue)– papillae

• Teeth• Mastication– dentin– pulp– gingiva

Teeth• Maxillary arch (upper)• Mandibular arch (lower)

– anterior teeth for biting and tearing– posterior teeth for chewing and grinding

• dent/i - teeth• decidu/o - shedding• Primary - 20 teeth• Permanent - 32 teeth

Oral Cavity

• Palate, hard and soft– bolus

• Pharynx• Uvula• Esophagus• Epiglottis

Esophagus

• Gullet• chyme• cardiac, or lower

esophageal or gastroesophageal sphincter

Stomach

• Body, fundus• pylorus• rugae• pyloric sphincter

Fundus

Body

Small Intestine

• small bowel• enter/o - small intestine• villi• Parts– duodenum– jejunum– ileum

• ileocecal valve

Large Intestine

• Large Bowel• col/o or colon/o• cecum• vermiform appendix

• Colon– ascending– hepatic flexure– transverse– splenic flexure– descending

• Sigmoid• Rectum• Anus

• Functions– production of bile– glucose - glycogen– storage of vitamins, B12, A, D, E, K– erythrocytolysis (pigment released eliminated in bile called

bilirubin)– bilirubin gives stool its characteristic dark color– removes toxins from blood– manufactures blood proteins

Liver - hepat/o

Pancreas

• internal - endocrine function– insulin– glucogon

• external - exocrine function– amylase - carbohydrates– trypsin, chymotrypsin - proteins– lipase - fats

• enzymes inactive until reach duodenum

Gallbladder

• pear-shaped sac under the liver• chol/e means bile or gall• cyst/o means cyst or sac• gallbladder contracts forcing bile out cystic

duct into common bile duct.

Bile• bile is a digestive juice- emulsifier acts on fat

in a way that lipid enzymes can digest fat• travels via hepatic duct to cystic duct to gall

bladder, where stored• bile consists of water, bile salts, cholesterol,

and bilirubin (a colored substance resulting from breakdown of hemoglobin)

• bilirubin gives bile yellow or orange color

Stomach during Digestion

• Gastric juices– HCL - activates

enzymes– protease– pepsin– lipase

• Chyme

Small Intestine during Digestion

• digestion completed in small intestine

• chyme mixed with bile and pancreatic juices

• emulsification• absorption

Large Intestine

• receive fluid waste products and store until released from body.

• excess water absorbed• feces, stools• defecation, or bowel

movement