Structures of The Digestive System

  1. Oral Cavity (mouth) - Storage place for food while itmouthis being chewed. Place where saliva is mixed with food.
  2. Lips - Hold food in oral cavity and help direct food onto teeth.
  3. Teeth - Physical Digestion (breaks food into smaller pieces to create more surface area for enzymes to work on)
  4. Salivary Glands - Produce saliva for moistening and chemically digesting food. Saliva contain the enzyme salivary amylase which begins the chemical digestion of starch to maltose.
  5. Tongue - Directs food onto teeth and pushes chewed food to the pharynx.
  6. Pharynx - Back of the throat where oral and nasal cavities join. This is where swallowing occurs.
  7. Epiglottis - Flap of tissue, which closes off the trachea keeping food from entering the air passage.
  8. Esophagus - Tube leading from the pharynx to the stomach. Food is transported through this tube from the mouth to the stomach by peristalsis.

Swallowing - A reflex action - Usually performedperistalsisautomatically. Food enters the esophagus because the air passages are blocked. The opening to the nose is covered by the soft palate. The glottis (opening to the larynx and windpipe) is covered by the epiglottis. No breathing occurs. If it does, choking may occur. 

Peristalsis - Rhythmical contraction of the esophageal wall, pushing food along. Smooth muscle cause the contraction. Peristalsis also occurs all along the intestinal tract.

Swallowing Animation

Structures of Digestive System con't


  1. Cardiac Sphincter (esophageal sphincter) - Band of muscle which closes off the top part of the stomach to prevent food from being regurgitate into the esophagous.
  2. Stomach - J-shaped organ which stores and churns food. The churning helps physically digest food, which creates more surface area and results in a mushy liquid called acid chyme. The chemical digestion of proteins beings here.

    (Especially after eating a protein-rich meal)

    Gastrin - Is a hormone produced by the lower part of the stomach which enters the blood stream and later stimulate the upper part of the stomach to stimulate gastric glands to produce Pepsinogen and HCl. HCl and pepsinogen react with each other to produce Pepsin.

    Pepsin chemically digests proteins to peptides.

    HCL can burn the gut lining so a mucous layer is produced to prevent this from happening. If a portion of the gut is burned it is called an ulcer.