Lesson 1 Science

• Digestion


  1. Food is broken down into smaller molecules that the body cells can utilize

  2. Food is changed physically and chemically

  3. Food is changed into smaller sizes by chewing or mastication

  4. Food is softened and lubricated by digestive juices

  5. Food is liquefied by the churning action of the stomach and wave-like contraction of digestive organs

  6. Physical changes are done to enable food to be acted upon efficiently by digestive enzymes

  7. Digestive enzymes chemically change food into smaller molecules for the body to use as energy
• Digestive system


  Tube-like structure with an anterior opening (mouth) where food enters and a posterior opening (anus) where undigested residue exits
• Organs of the alimentary tract

  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
• Accessory organs of digestion


  • Liver
  • Pancreas
• Mouth/buccal cavity


  Ingests food, adapted to break down food mechanically and chemically
• Structures in the mouth

  • Teeth
  • Tongue
  • Salivary glands
• Saliva


  Contains salivary amylase ptyalin that breaks down carbohydrate-rich foods
• Bolus


  Ball-shaped mass of chewed and lubricated food
• Swallowing


  1. Pushes the bolus into the pharynx

  2. Swallow reflex raises the epiglottis to cover the trachea opening
• Esophagus


  Muscular tube that conveys food from the pharynx to the stomach, uses peristalsis to move the bolus
• Stomach


  Pear-shaped organ connected to the esophagus, contains gastric glands that secrete hydrochloric acid, pepsinogen, and mucus
• Gastric juice


  Secretions of the gastric glands, including hydrochloric acid and pepsin
• Stomach churning


  Changes the bolus into a semi-fluid consistency called chyme
• Small intestine


  Long, coiled tube consisting of the duodenum, jejunum, and ileum, where final digestion and absorption occurs
• Large intestine/colon


  Temporarily stores undigested residue or feces, consists of the ascending, transverse, and descending colon
• Rectum


  Serves as a warehouse for undigested residue or feces, ends at the anal canal/anus which is the exit point for fecal materials
• Liver


  Largest organ in the body, secretes bile which neutralizes acidity of chyme and emulsifies fats
• Pancreas


  Gland that secretes digestive enzymes (amylopsin, trypsin, steapsin) directly into the duodenum
• Teeth are used to break down food into smaller pieces.
• The liver produces bile, which is essential for the digestion and absorption of fats in the small intestine.
• The mouth is the first organ involved in digestion.
• The tongue helps mix food with saliva and push it towards the throat.
• Salivary glands produce saliva, which contains enzymes that begin breaking down carbohydrates.
• Saliva contains amylase, an enzyme that breaks down carbohydrates.
• Salivary glands produce saliva, which contains amylase, an enzyme that breaks down carbohydrates.