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• Anabolism


  Build up of nutrients
• Catabolism


  Breakdown of nutrients
• Digestive Tract


  • Oral cavity
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
• Accessory Organs


  • Salivary glands
  • Liver
  • Gallbladder
  • Pancreas
• The digestive system consists of the digestive tract and accessory organs
• Functions of the Digestive System

  • Ingestion
  • Propulsion
  • Mechanical Digestion
  • Chemical Digestion
  • Absorption
  • Defecation
• Bolus


  Chewed food
• Carbohydrate digestion


  Polysaccharides -> disaccharides -> monosaccharides
• Proteins


  Broken down into amino acids
• Lipids


  Broken down into glycerol and fatty acids
• Intake of food leads to mastication (chewing) and mechanical digestion
• Peristalsis is the movement of food through the digestive tract
• Chyme is the food that has been broken down in the stomach
• Chemical digestion breaks down food into monomers that can be absorbed
• Digested food is used as energy, while undigested food and wastes are eliminated as feces
• Mouth


  • Ingestion of food
  • Chewing and mixing of food
  • Begins chemical breakdown of carbohydrates and lipids
  • Moves food into the pharynx
  • Moistens and dissolves food, allowing taste
  • Cleans and lubricates the teeth and oral cavity
  • Has some antimicrobial activity
• Pharynx


  • Propels food from the oral cavity to the esophagus
  • Lubricates food and passageways
• Esophagus


  • Propels food to the stomach
  • Lubricates food and passageways

  
• Stomach


  • Mixes and churns food with gastric juices to form chyme
  • Begins chemical breakdown of proteins
  • Releases food into the duodenum as chyme
  • Absorbs some fat-soluble substances
  • Possesses antimicrobial functions
  • Stimulates protein-digesting enzymes
  • Secretes intrinsic factor required for vitamin B12 absorption
• Small Intestine


  • Mixes chyme with digestive juices
  • Propels food at a rate slow enough for digestion and absorption
  • Absorbs breakdown products of carbohydrates, proteins, lipids, and nucleic acids, along with vitamins, minerals, and water
  • Performs physical digestion via segmentation
  • Provides optimal medium for enzymatic activity

  
• Accessory Organs


  • Liver: produces bile salts that emulsify lipids

  Gallbladder: stores, concentrates, and releases bile

  Pancreas: produces digestive enzymes (amylase, protease, lipase) and bicarbonate-rich juices to neutralize acidic chyme
• Large Intestine


  • Further breaks down food residues
  • Absorbs most residual water, electrolytes, and vitamins produced by enteric bacteria
  • Propels feces toward rectum
  • Eliminates feces
  • Concentrates and temporarily stores food residue prior to defecation
  • Mucus eases passage of feces through colon

  
• Oral Cavity


  • Mouth
  • Teeth
  • Tongue
  • Salivary glands
• Teeth


  Important in mastication and assist in speech
• Permanent Teeth


  • 32
• Deciduous Teeth


  • 20
• Tongue


  Manipulates food for chewing and swallowing
• Salivary Glands


  • Produce saliva

  Help keep the oral cavity moist

  Prevent bacterial infection

  Begin the process of digestion
• Pharynx


  Involved in both digestion and respiration

  Consists of three parts: oropharynx, nasopharynx, laryngopharynx

  Only oropharynx and laryngopharynx normally used for digestion

  Passageway of the food from the mouth to the esophagus

  
• Esophagus

  • Extends between the pharynx and the stomach

  Upper esophageal sphincter allows bolus to move from pharynx to esophagus

  Peristalsis propels the bolus through the esophagus

  Lower esophageal sphincter allows bolus to move from esophagus into stomach and prevents chyme from entering the esophagus

  Mucus secretion lubricates the esophagus
• Stomach


  • Gastroesophageal opening (cardiac opening) is the opening from the esophagus into the stomach

  Lower esophageal sphincter (cardiac sphincter) surrounds the cardiac opening

  Fundus is the left part of the stomach, superior to the cardiac opening

  Body is the largest part of the stomach, with greater and lesser curvatures

  Pylorus is the funnel-shaped part of the stomach, with a wider pyloric antrum and narrower pyloric canal

  Pyloric sphincter surrounds the pyloric orifice and regulates movement of gastric contents into the small intestine

  Main function is to store and mix the chyme

  Secretes mucus, intrinsic factor, and hydrochloric acid

  
• Gastroesophageal opening (cardiac opening)


  Opening from the esophagus into the stomach
• Lower esophageal sphincter (cardiac sphincter)

  Surrounds the cardiac opening

  
• Fundus

  On the left part of the stomach; superior to the cardiac opening
• Body


  Largest part of the stomach, which turns to the right, creating a greater curvature and lesser curvature

  
• Pylorus


  Funnel-shaped part of the stomach

  
• Pyloric antrum


  Wider part toward the body of the stomach
• Pyloric canal


  Narrow part of the funnel
• Pyloric orifice


  Opening of the pyloric canal to the small intestine
• Pyloric sphincter


  Surrounds the pyloric orifice and helps regulate the movement of gastric contents into the small intestine