digestive system

• Digestion


  The breakdown foods, mechanically or chemically, into small water-soluble molecules that can be absorbed into the bloodstream (nutrients becomes part of the plasma)
• Mastication


  Mechanical Digestion; "Chewing"
• Alimentary Canal


  Canal through which food travels on it's way from themouth(pharynx, esophagus, stomach, small intestine, large intestine)to the anus.

  
• Gastrointestinal Tract (GI Tract)


  The passageway from the stomach to anus... excluding the mouth and esophagus (everything superior to stomach)

  
• "Gastro"


  Stomach
• "intestinal"


  Intestines
• Lumen


  The inside cavity of any tube in the body; the hollowed out portion
• 4 Layers of tissue of the Alimentary Canal (Esp. Esophagus)

  (Outside) -Serosa, attached to mesentery;Muscularis;Submucosa;Mucosa(Lumen; inside)

  
• General flow of food through the Alimentary Canal

  mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus

  
• 3 Parts of Pharynx

  Empty place behind tongue (& sinuses):

  (Top --> Bottom)

  Nasopharynx(behind the nasal passage)

  Oropharynx(Behind mouth)

  Laryngopharynx(by the larynx)

  
• Trachea


  Not part of Digestive System

  Hyaline Cartilage that allows air to pass to and from lungs
• Larynx


  Not part of Digestive System

  Anterior end of the trachea: A cartilaginous structure at the top of the trachea...

  Contains "voice box"

  
• Tongue


  Muscle that moves food around in mouth- has taste sensation
• T/F: The duodenum comes right before stomach

  False
• Process of Swallowing


  1) Salivation (Chem. Digestion; enzymes begin to break down sugars)

  2) Mastication

  3) Tongue forms bolus

  4) Tongue rises to push bolus down; uvula comes up

  5) Larynx pushes up

  6) Epiglottis covers trachea

  7) Deglutition occurs (swallowing)

  
  

  ~~

  8) Peristalsis push food down esophagus

  9) Food enters stomach
• Mouth


  Buccal Chamber where mechanical digestion and some chemical digestion begins
• Soft Pallate


  Back of the roof of the mouth
• Uvula


  Separates the nasopharynx from the oropharynx when swallowing.

  Upper extension of the soft palate; As the tongue rises to push bolus down the uvula comes up

  
• Epiglottis


  A cartilage (tissue) that prevents food from entering the trachea, or windpipe, during swallowing

  
• 3 Main Regions of Stomach

  Fundus

  Body- holding the food

  Pylorus- region before sphincter and after body...

  Pyloric Sphincter- Muscle (drawstring) that controls the outflow of food from the stomach to the small intestine

  
• Layers of stomach (also small intestine)

  Serosa- thin slick outer layer

  Muscularis- longitudinal (in s. intestine it gives it the ability to push chyme through), circular, and oblique

  Submucosa- layer of connective tissue that contains blood vessels

  Mucosa- In stomach: Contains temporary folds called rugae and gastric pits

  In Small intestine: lined with "rings"/circular folds or ridges that have villi; then microvilli to increase surface area!

  
• Gastric pits


  Help stomach perform secretion; increases surface area for absorption

  
• Functions of the Stomach

  • Temporary food storage

  • Churns food; mechanical digestion

  • Secretes "intrinsic factor" - allows the absorption of vitamin B12

  • Secretes gastric juices (HCl; hydrochloric acid)

  • Destroys pathogenic bacteria (protection)
• pH of Gastric Juices

  pH 1-3; acidic
• Chyme


  Broken down food mixture (Liquid)
• Bolus


  = Mastication + Saliva

  Chewed up food formed into a ball
• Deglutition


  Act of swallowing

  3 Stages:

  1) Voluntary Oral Stage

  2) Pharyngeal Stage (involuntary)

  3) Esophageal Stage (involuntary)

  
• Parystalsis


  After swallowing, the Alimentary Canal takes over with a "snake" like motion executed by the muscles of the esophagus to push food down to the stomach
• Teeth in Children


  DeciduousTeeth (20 in total)
• Teeth in Adults


  32 in total

  Per jaw 16 (Maxillary : Mandible)

  Incisors: 4

  Canine: 2

  Premolar: 4

  Molars: 6
• 3 Regions of Small Intestine

  1) Duodenum (12"; shortest) - Circles around the pancreas; where the pancreas secrete digestive enzymes and bile from the liver is injected into the chyme

  2) Jejunum (8 ft.) - where most of the food is absorbed

  3) Ileum (~12 ft.) - The food is now a mixture / chime is watery (most of absorption is done)

  Also, reabsorption of bile/acid.. and Vit. B12

  
• Functions of Small Intestine

  Completes process of chemical digestion; absorption of digestive end products into blood and lymph; absorption of vitamin B12 (in ileum) and other vitamins, salts, and water; secretion of hormones that regulate digestive process
• 2 Ways of describing the Large Intestine

  Ascending, Transverse, Descending Colon

  or

  3 parts:

  1) Secum - 2-3"... below junction of the small and large intestine

  2) Colon - 5'... (majority) where carbohydrates are broken down (Stercobilincause brown pigment; pungent)

  3) Rectum - 8" - "S" curve - where feces is formed & STORED

  Anus - aids in formation of defecation (ridges) and escretion of feces

  
• Sphincter muscles in Anus


  Internal Sphincter Muscle - Involuntary

  External Sphincter Muscle - Voluntary (skeletal) - controllable
• Bilirubin


  Excreted in bile and urine (caused by the body's clearance of aged red blood cells) caused by the body's clearance of aged red blood cells...

  
  

  Causes the brown pigment of feces... and ... yellow pigment of skin (jaundice)
• Large Intestine


  • Water reabsorption

  • Formation of feces

  • Biome for bacteria - symbiotic (bacteria produce vit K, biotin (Ba), folic acid)...
• How much bacteria?


  100 Trillion = 3 lbs.
• Vermiform


  Appendix (Structure)"vermiform" = in the shape of a "worm"

  3-4 inches long...

  
• Vermiform


  Appendix (Function)1) "Reads" pathogens in alimentary tract & builds defences

  2) Contains "biofilm" that is the breeding ground for good bacteria, lymphocytes etc.

  Can replemish lost biofilm
• Accessory organs


  liver, gallbladder, pancreas