Science Chapter 14: Digestive System

• Food - a nourishing substance that we take into our body through eating or drinking 
• Nutrients - provides energy, promote growth, and sustain life.
• 6 Types of nutrients that our body needs: Carbohydrates, lipids (fats), proteins, vitamins, minerals and water
• Digestive system - mainly responsible for the digestion and absorption of food
• First Stage of Digestion - Ingestion
• Mouth - where Ingestion happens
• Absorption - 2nd Digestive Process
• Small intestine - where Absorption happens
• Assimilation - 3rd Digestive Process
• Metabolism - process on how the cells use the energy that they obtained from food during digestion
• The Digestion Process - complex process that begins with breaking the food into smaller pieces. Smaller substance that cells absorb and use to produce energy
• 2 types of Digestion - Mechanical Digestion and Chemical Digestion
• Mechanical Digestion - Food is physically broken down into smaller pieces by chewing, biting, churning
• Chemical Digestion - Food are chemically decomposed. The process is made possible by enzymes
• Bolus - chewed food inside the mouth, a ball like mixture of food particles and saliva
• Oral Cavity (mouth) - site of ingestion
• Pharynx (Throat) - muscular tube that serves as a common passageway for both food and air
• Epiglottis - this is a flap of tissue that automatically shuts the entrance to the larynx when swallowing food to prevent food from entering the respiratory tract
• Esophagus - a 25cm long tube that runs from the end of the pharynx down to the stomach
• Peristalsis - series of wavelike muscular contractions, which propels the bolus down to the stomach
• Mucus - a slimy substance that lubricates the passage of the bolus
• Stomach - 30cm long, J shaped expandable organ that receives the bolus from the esophagus
• Rugae - folds in the stomach that increase the surface area of the stomach
• Lower Esophageal sphincter - a muscular ring which acts as a value that prevents the backflow of bolus and gastric juice
• Gastric Juice - composed hydrochloric acid and pepsin and lipases
• Hydrochloric Acid - highly acidic, with a pH between 1 to 2, which softens fibrous food and kills most micro-organism
• Pepsin - breaks down protein
• Lipase - breaks down fats
• Small intestine - 6 to 7 meters long, 2-4cm wide. Longest part of the digestive tract
• 3 parts of Small Intestine - duodenum, Jejunum and ileum
• Pyloric Sphincter - a valve that prevents the backflow of chyme from the small intestine to the stomach
• Chyme -partially digested boluses mix with gastric juice, a semiliquid mass with a pH of 2 to 4
• Large Intestine - does not digest food, it only absorbs water and salts
• Rectum - expandable storage organ of undigested food
• Anal Sphincter - controls the releasing or holding of the stool for a short period
• Elimination - 4th Digestion Process
• Rectum - where the Elimination happens
• Defecation - a process wherein undigested food passes the anal canal and is excreted from the body
• Accessory Digestive Organs - Liver, Gallbladder and Pancreas
• Liver - largest organ of the body , largest gland. It produces Bile