digestive system (anaphy)

• the digestive system is also called gastrointestinal (GI) system
• the digestive system consists of a digestive tube called the GI tract, or alimentary canal, and several accessory organs
• primary function of the digestive system is to break down food, prepare it for absorption, and eliminate waste
• parts of the GI tract:

  • mouth
  • pharynx (throat)
  • esophagus
  • stomach
  • small intestine
  • large intestine
  • rectum
  • anus
• food passing along the GI tract is mixed with digestive enzymes and broken down into nutrient molecules, which are absorbed in the bloodstream
• undigested waste materials that cannot be absorbed in the blood are then eliminated from the body through defecation
• the accessory organs of digestion:

  • liver
  • gall bladder
  • pancreas
• the process of digestion begins in the mouth
• the mouth is also known as the oral cavity or buccal cavity
• mouth is a receptacle for food
• the mouth is formed by the:

  • cheeks (bucca)
  • lips
  • teeth
  • tongue
  • hard & soft palates
• salivary glands are three pairs of glands located in the oral cavity, which secretes saliva
• saliva contains important digestive enzymes that help begin the chemical breakdown of food
• in the mouth, food is broken down mechanically (by the teeth) and chemically (by saliva), and then formed into a bolus
• bolus is the food that has been chewed and formed into a round mass of substance inside the mouth, about to be swallowed
• the teeth play a role in initial stages of digestion by mechanically breaking down food (mastication) into smaller pieces as it mixes it with saliva
• mastication is the process of chewing food; crushing into smaller pieces by teeth mixed with saliva
• teeth are covered by a hard enamel, giving them a smooth, white appearance
• the dentin is the main structure of the tooth; beneath the enamel
• the pulp is the innermost part of the tooth, which contains nerves and blood vessels
• gums, also known as gingiva, is a pink fleshy tissue where the teeth are embedded
• tongue assists in this mechanical digestion process by manipulating the bolus of food during chewing and moving it to the back of the mouth for swallowing (deglutition)
• deglutition is the process of swallowing
• tongue also aids in speech production and taste
• papillae is the rough projections on the surface of the tongue that contain taste buds
• four basic taste sensations:

  • sweet
  • sour
  • salty
  • bitter
• all other taste perceptions are combinations of the four basic flavors
• sense of taste is intricately linked with sense of smell, making taste perception very complex
• two structures forming the roof of the mouth are the hard palate (anterior portion) and the soft palate (posterior portion)
• the soft palate, which forms a partition between the mouth and the nasopharynx, is continuous with the hard palate
• the entire oral cavity is lined with mucous membranes
• pharynx (throat) is the funnel-shaped passage-way to the respiratory and GI tracts
• pharynx also provides a resonating chamber for speech sounds
• as the bolus is pushed by the tongue into the pharynx (throat), it is guided by the soft, fleshy, V-shaped structure called the uvula
• the lowest portion of the pharynx divides into two tubes: trachea (one that leads to the lungs) and esophagus (one that leads to the stomach)
• trachea is the tube that leads to the lungs, while esophagus is the tube that leads to the stomach
• epiglottis is a small flap of cartilage that folds back to cover the trachea during swallowing, forcing food to enter the esophagus
• at all other times, the epiglottis remains upright, allowing air to freely pass through the respiratory structures
• stomach is a saclike structure located in the left upper quadrant (LUQ) of the abdominal cavity
• stomach serves as a food reservoir that continues mechanical and chemical digestion