Human Digestion

  1. Oral Cavity
    • 1.      Salivary glands
    • a.      Mammals have three major sets of salivary glands
    •                                                                                                                                       i.      Parotid
    • 1.      Under ear
    •                                                                                                                                     ii.      Sublingual
    • 1.      Under tongue
    •                                                                                                                                   iii.      Submandibular
    • 1.      Around mandible
    • b.      Saliva and salivary amylase
    •                                                                                                                                       i.      Salivary amylase is the enzyme that begins digestion of carbohydrates
  2. After the Oral Cavity
    • Pharynx
    • Esophagus
  3. Stomach
    • J-shaped 
    • 1.      Main part is the fundus
    • 2.      Narrow part is the pylorus, where the pyloric sphincter is
    • 3.      Flattened mucosa has holes, openings into gastric glands, called gastric pits (beneath lumen)
    • a.      Contain chief cells, which secrete pepsinogen
    • b.      Contain parietal cells, which secrete hydrocholoric acid
    • c.       Contains cells that release the hormone, gastrin
    • d.      Secretes mucus
  4. Chief cells
    • a.      secrete pepsinogen
    •                                                                                                                                       i.      Pepsinogen generally is called a Zymogen
    • 1.      Inactive form of an enzyme
    • a.      Not active; won’t digest anything 
  5. parietal cells
    • a.      secrete hydrocholoric acid
    •                                                                                                                                       i.      HCl is needed to activate pepsinogen to pepsin which is a protein-splitting enzyme that begins the digestion of protein
    •                                                                                                                                     ii.      Because of acidity, chyme has an acidity of 2
    • Needs to be acidic to activate pepsinogen
  6. gastrin and mucus
    •                                                                                                                                       i.      Hormone that increases gastric motility (enhances churning and peristalsis) and also increases gastric juice release
    • 1.      Gastrin and parasympathetic do the same thing and work at the same time

  7. Small Intestine
    • 1.      All of the enzymes present in the small intestine come from the small intestinal gland, pancreas, have bile
    • a.      They won’t function in acidic environment
    •                                                                                                                                       i.      Acid chyme has to be neutralized
    • 1.      It’s the sodium bicarbonate salts from the pancreas that neutralize the acid chyme when it comes in the small intestines 
  8. Small Intestine Villi
    • 1.      The small intestine projects the villi and sends a small part below the villus
    • a.      The portion of the mucosa that dips below the luminal surface are the intestinal glands
    •                                                                                                                                       i.      Called Krypts of Lieberkuhn 
  9. Small Intestine Krypts
    • 1.      Name of small intestinal glands
    • 2.      Secrete lots of enzymes
    • a.      Lipases, nucleases, peptidases
    • 3.      Also secretes some hormones
    • a.      One is secretin
    •                                                                                                                                                                                                               i.      An intestinal hormone which is released when acid chyme enters the small intestines
    •                                                                                                                                                                                                             ii.      Goes out and affects pancreas, causing pancreas to secrete sodium bicarbonate salts
    •                                                                                                                                                                                                           iii.      Secretin controls sodium bicarbonate salt release (acts when acid chyme enters the small intestine) 
  10. Small Intestine structure
    •                                                               i.      Duodenum is a C-shaped structure
    •                                                             ii.      Jejunum and Ileum
    • 1.      Highly coiled region of the small intestine
    • 2.      Loose
    •                                                           iii.      Ileocolic (ileocecal sphincter)
  11. Small Intestine and Associated Glands
    • a.      All of digestion is completed in the small intestines, which is the reason why the accessory glands, the pancreas and liver, have to send juices in there
    • 1.      Not all of the enzymes that work with the small intestine come from the small intestines, or juices
    • a.      Additions Enzymes from  pancreas
    • b.      Juices from pancreas and liver (sodium bicarbonate and bile, respectively)
  12. One function of the small iintestine
    • a.      Most absorption in small intestine
    •                                                               i.      All the nutrients are absorbed
    •                                                             ii.      Lots of water is absorbed
    • b.      Anything not absorbed is moved to the colon 
  13. Small Intestine Modifications
    •                                                               i.      Plicae: circular or pleated folds that distend when chyme starts entering
    •                                                             ii.      Villi: Simple columnar has undulating waves within the wall
    • 1.      Villi: fingerlike projections of the lumen
    • a.      Goes below into submucosa; doesn’t stop at mucosal region
    •                                                                                                                                       i.      Portion that goes below forms the glands of the small intestine, called the Krypts of Lieberkuhn
    •                                                           iii.      Microvilli
    • 1.      Each simple columnar cell, on apical (free) border, have microvilli
    • b.      All increase surface area in the small intestine 
  14. Small Intestine Krypts of Lieberkuhn and hormones
    - reaction to chyme entering
    •                                                               i.      Where you have the intestinal glands
    •                                                             ii.      Produce a variety of enzymes
    •                                                           iii.      Releases hormones
    • 1.      Chyme entersà distension of small intestineà causes parasympathetic to stimulate release of digestive juicesàenterokinase
  15. Small intestine and enterokinase
    • 1.      Enterokinase—hormone like substance
    • a.      Function: to activate trypsinogen that is released by the pancreas
    • b.      Comes from small intestine
    • c.       Once there is chyme in the small intestine, pancreas and glands release their material
    •                                                                                                                                       i.      Trypsinogen (protein-splitting enzyme in inactive form active by enterokinase and forms trypsin)
    •                                                                                                                                     ii.      Two other zymogens released by pancreas
    • 1.      Procarboxypeptidase
    • 2.      Chymotrypsin
    •                                                                                                                                   iii.      Both are activated by trypsin
  16. CKP
    • 1.      Cholecystokininpancreozymin (CSK or CKP)
    • a.      Controls release of bile from the gallbladder and pancreatic enzymes (trypsinogen, chymotrypsinogen) from those structures into the duodenum
    •                                                                                                                                       i.      Produced by small intestine when chyme enters
    • 1.      Distension causes parasympathetic stimulation
  17.                                                               i.      No enzymes in small intestine function under __ conditions
    1.      Requires __
    a.      Done by __, secreted by __
    • acidic
    • neutralization
    • secretin
    • Krypts
  18. Secretin
    •                                                                                                                                       i.      Hormone released by glands of small intestine; travels to pancreasà causes pancreass to release sodium bicarbonate salts, which are going to travel through pancreatic duct and into duodenum and neutralize the chyme
    •                                                                                                                                     ii.      Due to reaction of acidic chyme coming in (control)
    •                                                             ii.      Only when chyme enters does the hormones be released; secretin is released in response to acidity
  19. beauty of invagination of the submucosa
    •                                                               i.      Design brings the submucosa up into the core of each villus
    • 1.      Brings capillaries of those two systems close to the area where absorption will occur because absorption is going to go through the simple comlumnar cells into the core            
    • a.      They’ll be picked up by either the lymphatic or blood vascular system
    •                                                             ii.      Each villus has a core of submucosa, whose function is to bring blood capillaries and nerves in close proximity to the systems 
  20. Core of the Villus
    •                                                               i.      Core of the villus
    • 1.      Connective tissue containing BV and LV and nerves
    • a.      In that core, we bring the capillaries close to the area where absorption is going to take place
    • b.      Facilitates absorption
    • 2.      If it were empty, we’d have to somehow transport it down the submucosal layer
    • b.      We’re bringing the mucosa up and filling the submucosa in there
  21. Colon
    • a.      Functions:      
    •                                                               i.      Absorption of some necessary water, drugs, some vitamins, and formation of the feces
    • b.      NO DIGESTION
  22. parts of the Small Intestine
    •                                                               i.      cecum- blind pouch
    • 1.      In man, off blind pouch is the appendix
    • 2.      No function; place where undigested seeds and junk can get caughtà appendicitis
    •                                                             ii.      Ascending colon:
    • 1.      Goes up right side of body until it gets to liver and turns
    •                                                           iii.      Transverse: straight (across abdominal)
    • 1.      Hits spleen
    •                                                           iv.      Descending
    • 1.      Down left
    •                                                             v.      When it hits the lower lumbar vertebrae, it makes an S-shaped curveà sigmoid colon
    •                                                           vi.      Rectum
    •                                                         vii.      Anus 
Card Set
Human Digestion
Nutrition/ Digestion