The DIGESTIVE System

Digestive System Functions Digestion-breaking down of food by both mechanical and chemical means Absorption-passage of digested food into the blood stream Defecation (excretion)-elimination of indigestible substances Ingestion-taking food into the body (eating) Movement (propulsion)-passage of food along the alimentary canal

Chemical vs Mechanical Digestion Chemical: Enzymes break down food to smaller molecules for absorption Mechanical: broken down into smaller parts--MASTICATION and MACERATION

Alimentary canal Tube food passes through Begins at mouth - ends with anus Food is chewed Bolus created Bolus swallowed

Pharynx Bolus moves into pharynx Medical term for throat Has three parts Nasopharynx Oropharynx Laryngopharynx

Esophagus 8-12 inches long Smooth muscle contractions called: peristalsis Cardiac (aka Gastroesophageal) sphincter Has no mucous membrane to protect from HCl from stomach

Stomach J-shaped 3 sets of muscle in different directions HCl= chemical breakdown Pepsin begins protein digestion Contain rugae to increase surface area Change bolus into chyme Mucus protects stomach lining

Small intestine 3 parts Duodenum--most chemical digestion takes place here Jejunum-absorption continues Ileum absorption continues 15-22 ft long Absorbs some of the water in food & what you drink Nutrients are absorbed through structures called villi

Large intestine Called the colon Main function is water absorption + Vit K absorption Begins with cecum-contains lymphatic organ called appendix

Large intestine Ascending colon Transverse colon-makes hunger sounds Descending colon Sigmoid colon Rectum Anal canal Anus

Accessory organs CONTRIBUTE to digestion process NOT part of the canal or tube Food DOES NOT pass through them

Tongue and teeth Teeth break food down into smaller pieces Tongue moves food to the back of throat

Parts of a tooth Crown = exposed portion above gum line Neck = between crown & root Gingivae = gums Root = one to three-- embedded in mandible & maxillae

Parts of a tooth Enamel = outermost part, protects from wear & tear the hardest substance in the body Dentin = calcified connective tissue Gives tooth it’s basic shape & rigidity

Parts of a tooth Pulp Cavity = large cavity enclosed by dentin--filled with pulp Cementum = bone-like substance covers dentin of roots

Parts of a tooth Periodontal Ligament an area of dense fibrous connective tissue anchors teeth in position serves as a shock absorber when chewing

Salivary glands 6 total--3 pair parotid submandibular sublingual

Salivary glands Saliva is mostly water Enzymes that digest carbs—Amylase—breaks starch into maltose Softens and moistens food

Liver and Gall Bladder Liver makes bile Bile is stored in gall bladder (sac) Bile breaks down fats--emulsification Secreted as it is needed Eliminated through intestines

Pancreas Located posterior to stomach Secretes enzymes to chemically breakdown fats, carbs, and proteins Increases pH of chyme Pancreatic juice—thru pancreatic duct—thru heptopancreatic sphincter

Mastication Chewing--makes bolus Teeth mechanically break down food Food is mixed with saliva

Deglutition Swallowing Tongue pushes food to back of throat Oropharynx--second part of throat Smooth Muscles contract causing peristalsis Voluntary

Peristalsis General term for wave-like contractions in esophagus and intestines Rhythmic smooth muscle contractions

Maceration Stomach contracts and bolus mixed with gastric juices and HCl until it is liquid-like Bolus is changed to chyme Empties through pyloric sphincter

Segmental contraction Each segment of small intestine contracts Helps mix bile and pancreatic juices with chyme Smooth muscle contractions peristalsis in each segment

Absorption Nutrients absorbed in jejunum and illeum Some nutrients & water absorbed thru stomach Some water absorbed through small intestine Most water absorbed through large intestine

Haustral churning Each segment in large intestine is called a haustra Smooth muscle contractions move contents along (type of peristalsis) Water is absorbed in large intestine

Defecation Elimination of material that is undigestible Plant fiber--necessary for health of the intestines Formation of feces and elimination of feces

Nutrients are broken down in different places in digestive system Carbohydrates Begin digestion in mouth with enzyme AMYLASE from salivary glands Amylase breakdown continues in stomach Finish breakdown in duodenum (pancreatic juice)

Fats Fats begin mixing with gastric juices in stomach Bile from gall bladder goes into small intestine to break them down Pancreas secretes enzymes (lipase) to finish chemical breakdown

Proteins Begin mixing with pepsin in stomach Finish with secretions from pancreas into duodenum

Digestive System End

Digestive System Diseases and Disorders

Appendicitis Inflammation of the appendix Caused by an obstruction by fecal material, a foreign body, stenosis, kinking of the organ, or carcinoma https://www.youtube.com/watch?v=-nlx9mhwafM

Cirrhosis of the Liver Scarred liver tissue due to chronic inflammation Caused by hepatitis, chemical exposure, parasites, and alcoholism Symptoms include: jaundice, bleeding, edema, and increased sensitivity to drugs and chemicals

Tumors of the Digestive System Can occur in all areas of the digestive system Can be malignant or benign Colorectal cancer 3rd most common cause of cancer for both males and females Overall mortality rate is over 60% Factors contributing to colorectal cancer include genetic predisposition, diet high in fat, protein, insufficient dietary fiber, and low calcium and selenium in the diet

Gall Stones Crystallization of bile in the gallbladder Can block the bile duct causing intense pain Usually treated with gall stone dissolving drugs, lithotripsy, or surgery

Hepatitis Inflammation of the liver Can be caused by viruses, drugs, and certain chemicals including steroids and alcohol Many different types of Hepatitis including: Hepatitis A (Infectious Hepatitis) Hepatitis B (Serum Hepatitis)

Hepatitis A Infectious hepatitis caused by hepatitis A virus Spread by fecal contamination of food, clothing, toys, eating utensils, etc. Mild disease of children and young adults Characterized by anorexia, malaise, jaundice, nausea, diarrhea, fever, and chills

Hepatitis B Serum hepatitis Caused by the Hepatitis B virus--cause is often unknown or may be: Transmitted by sexual contact, contaminated syringes, transfusion equipment, saliva, tears, and puncture wounds in the skin Can produce cirrhosis and possibly cancer of the liver

Obesity Excess body fat--20% for men, 30% for women Currently over 50% of U.S. population is clinically classified as obese 14% of all male cancers linked to obesity 20% of all female cancers linked to obesity

Peptic Ulcers Crater like lesions that develop in the gastrointestinal tract Most commonly caused by a bacterial infection or chronic use of aspirin, ibuprofen or naproxen