Digestive System Notes Alimentary Canal (Gastrointestinal Tract) The continuous tube through which food passes, allowing digestion and absorption of nutrients. Organs Included: 1. Mouth: • Entry point for food. • Mechanical digestion via chewing (teeth). • Chemical digestion begins with saliva containing amylase. 2. Pharynx: • Passageway for food, fluids, and air. 3. Esophagus: • Propels food to the stomach using peristalsis. 4. Stomach: • Function: Temporary storage tank for food. • Mixes food with gastric juices for breakdown into chyme. • Secretes pepsin (breaks down proteins). 5. Small Intestine: • Divisions: • Duodenum. • Jejunum. • Ileum. • Primary site of nutrient absorption. • Receives bile (from liver) and pancreatic juices (from pancreas) to aid digestion. 6. Large Intestine: • Divisions: • Cecum, appendix, colon (ascending, transverse, descending, sigmoid), rectum, anal canal. • Functions: • Absorbs water. • Houses bacterial flora for vitamin synthesis. • Forms and eliminates feces. 7. Rectum and Anal Canal: • Stores feces for elimination. Accessory Digestive Organs These organs assist the alimentary canal by producing or storing substances necessary for digestion. Organs Included: 1. Teeth: • Primary Teeth: 20 deciduous teeth erupt between 6 and 24 months. • Permanent Teeth: 32 permanent teeth appear between 6 and 12 years. • Classifications: • Incisors: For cutting and nipping. • Canines: Fang-like for tearing and piercing. • Premolars (Bicuspids) and Molars: Broad crowns for grinding and crushing. 2. Tongue: • Mostly skeletal muscle. • Functions: • Contains taste buds to analyze nutrient content of food. • Mixes food with saliva to form a bolus. • Aids in swallowing. 3. Salivary Glands: • Function: Produce and secrete saliva (water-based liquid containing amylase) for chemical digestion. • Types: • Parotid glands. • Submandibular glands. • Sublingual glands. • Fun Fact: Mumps infect the parotid glands. 4. Liver: • Secretion: Produces bile, a greenish liquid (pH 7.6–8.6) essential for fat digestion. • Functions of Hepatocytes: • Produce bile. • Process nutrients from blood. • Store fat-soluble vitamins. • Detoxify harmful substances. 5. Gallbladder: • Thin-walled muscular sac on the liver’s ventral surface. • Functions: • Stores and concentrates bile. • Releases bile into the duodenum to emulsify fats. • Disorders: • Gallstones causing blockages and pain. • Extreme cases can result in gallbladder rupture. 6. Pancreas: • Exocrine Function: • Produces pancreatic juice containing enzymes for digesting carbohydrates, proteins, and lipids. • Endocrine Function: • Secretes insulin to regulate blood glucose levels. • Disorders: Malfunction can cause diabetes. Important Notes About Digestive System Processes 1. Ingestion: Intake of food through the mouth. 2. Propulsion: • Swallowing. • Peristalsis (waves of muscle contractions moving food through the tract). 3. Mechanical Digestion: • Chewing (mouth). • Churning (stomach). • Segmentation (small intestine). 4. Chemical Digestion: • Breakdown of food molecules by enzymes. 5. Absorption: • Movement of nutrients into blood or lymph via small intestine. 6. Defecation: • Elimination of indigestible substances and waste products as feces.