REVIEW SHEET DIGESTION


These review sheets are presented as outlines of the material covered in class.  They do not provide details, but try to highlight the important areas and concepts covered.  You should use these as a general guide to be sure that you fully understand all the major topics covered during these lectures.  This is NOT an exhaustive list, but an OVERVIEW.  You are responsible for the material covered in class, whether or not it appears on this general outline.

Digestive Systems

A.  Evolution
    1.  Flatworms (Planaria)
        a.  gastrovascular cavity
        b.  single opening
        c.  specialization of cells
    2.  Annelids
        a.  unidirectional system
        b.  crop - allows food storage
        c.  gizzard - allows larger food particles
        d.  increase surface area in intestine
        e.  specialization in organs and cells to increase efficiency
B.  Vertebrates
    1.  Secretions
        a.  Enzymatic
            i.  salivary amylase, pepsin, pancreatic amylase, trypsin, chymotrypsin, carboxypeptidase
        b.  Non-enzymatic
            i.  mucus, HCl, bicarbonate (HCO3), bile, hormones
    2.  Structure
        a.  Layers of digestive tract walls
           i.  mucosal
                A.  villus (epithelial cells, microvilli)
                B.  blood vessels
                C.  lacteals
            ii.  submucosal
                A.  submucosal nerve plexus
            iii.  muscularis
                A.  circular muscle
                B.  myenteric nerve plexus
                C.  longitundinal muscle
            iv.  serosa
                A.  connective tissue
    3.  Breakdown of Macromolecules
        a.  Carbohydrates
            i.  salivary amylase, pancreatic amylase form disaccharides
            ii. sucrase, maltase, lactase form monosaccharides (glucose, fructose, galactose)
            iii. absorption of monosaccharides by the epithelial cells (into capillaries) by active or facilitated transport
        b.  Proteins
            i.  pepsin, trypsin, chymotrypsin (all endopeptidases)
            ii. aminopeptidase, carboxypeptidase (exopeptidases)
            iii.  activation of enzymes
                A.  acid (pepsinogen to pepsin)
                B.  enterokinase (trypsinogen to trypsin)
            iv.  absorption of amino acids by the epithelial cells (into capillaries) by active or facilitated transport
        c.  Fats
            i. lipase forms monoglyceride and fatty acids
            ii. emulsification with bile salts (form micelles)
            iii.  absorption of monoglycerides and fatty acids by epithelial cells by passive diffusion
            iv.  synthesis of triglycerides, packaged into chylomicrons within epithelial cells
            v.  exocytosis if chylomicron for diffusion into lacteals
    4.  Function of liver
        a.  receives blood from digestive tract first
        b.  detoxifies substances in blood
        c.  synthesizes bile salts and bile pigments
            i.  bilirubin formed from RBC breakdown, transformed to bile pigment
            ii. jaundice
        d.  bile stored in gall bladder
            i.  gallstones (excess cholesterol)

C.  Control of Digestion
    1.  Neural
        a.  ANS
        b.  enteric nervous system
    2.  Hormonal
        a.  gastrin, CCK, secretin
    3.  Phases of Digestion
        a.  cephalic
        b.  gastric
        c.  intestinal
    4.  Reflexes
        a.  ex. gastroileal reflex

D.  Path of digestion
    1.  Mouth
        a.  mastication
        b.  saliva
        c.  stimulation of gastrin release
    2.  Esophagus
        a.  perstaltic waves
        b.  sphincters
    3.  Stomach
        a.  anatomy (fundus, body, antrum)
        b.  pyloric sphincter
        c.  motility
            i.  myogenic smooth muscle (BER)
            ii. stretch
            iii. acid
            iv. gastrin
            v. parasympathetic nervous system
        d.  acid release
            i.  regulation (ANS, gastrin, stretch, calcium, etc.)
    4.  Duodenum
        a.  release of secretin and CCK
            i.  release of pancreatic enzymes and bicarbonate
            ii.  inhibition of stomach
            iii. stimulation of gallbladder contraction
            iv. sphincter of Oddi
        b.  motility
            i.  BER duodenum vs ileum
            ii. segmentation
            iii. rapid peristalsis
    5.  Jejunum and Ileum
        a.  absorption
        b.  motility
    6.  Large Intestine
        a.  decrease in mucosal layer, villi
        b.  bacteria
            i.  vitamin synthesis and absorption
        c.  ion and water reabsorption
            i.  Cholera
    7.  Defecation

E.  Ruminants
    1.  symbiotic digestion
    2.  anatomy
        i.  rumen
        ii. reticulum
        iii. omasum
        iv. abomasum
        v.  intestine
    3.  bacteria and protozoans
        i. amino acid synthesis from urea
        ii.  carbohydrate and cellulase digestion to organic acids
        iii. synthesize vitamin B

F.  Rodents
    1.  coprophagy
    2.  caecum
        i.  formation of special pellets with proteins and B vitamins
 
 

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Last udpated November 2004