Digestive System

• Digestion Phases

  1. Ingestion
  2. Mechanical & Chemical Digestion
  3. Absorption
  4. Elimination or Egestion
• Digestive System: a continuous tube that begins at the mouth and ends at the anus
• Digestive System: about 30 feet long in the average adult
• Digestive System: known as the alimentary canal or gastrointestinal tract
• Functions of the Digestive system:

  1. The digestion of food into nutrients
  2. The absorption of nutrients into the bloodstream
  3. The elimination of solid waste
• Mouth: The opening of the digestive system where food is chewed and mixed with saliva.
• Teeth: mechanically breakdown food into small pieces
• Tongue: mixes food with saliva and swallows it.
• Amylase: helps breakdown starch, or carbs
• Saliva: a liquid that helps breakdown starch and carbs. Located in the mouth
• Epiglottis: a flap-like structure at the back of the throat that closes over the trachea preventing food from entering it, located in the pharynx
• Teeth: used for chewing the food
• Mastication: another word for chewing
• Bolus: A ball of food that is swallowed into the mouth and then chewed.
• Tongue: a muscle covered with a mucous membrane
• Tongue: has a rear portion called the root, the tip, and the central body
• Tongue: covered with taste buds and raised elevations called papillae
• Papillae: raised elevation inside the tastebuds.
• Salivary Glands: three pairs of glands open into the oral cavity, producing saliva
• Salivary glands:

  1. parotid glands
  2. Sublingual glands
  3. Submandibular glands
• Types of Digestion:

  1. Mechanical or Physical
  2. Chemical
• Chemical Digestion: enzymatic reactions that improve the digestion of macromolecule
• Enzymes: are catalysts in speeding up a chemical reaction
• Gastrointestinal Tract: tube within a tube
• Esophagus: the food is moved down the esophagus toward the stomach by peristalsis
• Peristalsis: wave-like contractions of the muscles of the esophagus
• Lower Esophageal Sphincter: muscle valve that permits the passage of food and controls the opening and closing of the esophagus
• Chyme: The partially digested food that is in the stomach.
• Esophagus: approximately 20cm long
• Stomach: a muscular, expandable organ
• Fundus: upper portion of stomach
• Antrum: lower portion of the stomach
• Hydrochloric acid and other gastric juices: covert the food to a semiliquid state.
• Chyme: semi-liquid state of food in the stomach
• Hydrochloric Acid: kills bacteria in the stomach
• Lipase: breakdown fats into fatty acids
• Pyloric Sphincter Valve: where chyme passes through to get into the small intestine
• Pepsin: a digestive enzyme that is secreted as an inactive protein
• Pepsinogen: inactive protein state of pepsin and is converted back to pepsin in the increased presence of hydrochloric acid
• small intestine: roughly 7 meters long