Digestive Tract Flashcards
The most common microorganisms
in the human stomach and, because it is the next residence available to organisms moving with
ingesta, the duodenum, are
Lactobacilli, Streptococci and yeasts.
Small pH differences along the
small intestine favor
Lactobacilli, Enterobacteriaceae, Streptococci, Bacteroides, Bifidobacteria
and Fusobacteria in the human jejunum and ileum.
The most common microorganisms in the human colon are
Bifidobacteria,
Lactobacilli, Streptococci, Bacteroides, Fusobacteria, Enterobacteriaceae, Pseudomonas,
Clostridia, Proteus species, yeasts and protozoa.
The most beneficial individual species for the human gastrointestinal tract are
Bifidobacterium
bifidus (bifidum), Bifidobacterium infantis, Lactobacillus acidophilus, Lactobacillus
bulgaricus, Lactobacillus brevis, Lactobacillus casei, Lactobacillus cellobiosus,
Lactobacillus fermenti, Lactobacillus leichmannii, Lactobacillus plantarum, Lactobacillus
rhamnosus, Lactobacillus salivarius, Lactobacillus sporogenes, Saccharomyces boulardii,
Enterococcus faecium, and Streptococcus thermophilus.
The ______ are the most common microorganisms in the healthy human digestive tract
and are the predominant microbes in human breast milk
Bifidobacteria
comprise about 50% of all intestinal microflora and ferment dietary fiber
carbohydrates to short chain fatty acids.
Oral
supplementation with ______ has been found to reduce the severity and
duration of childhood rotaviral diarrhea.
Saccharomyces boulardii
Lactobacilli
Lactobacilli (especially Lactobacillus acidophilus, L. brevis, L. bulgaricus, L. casei, and L.
rhamnosus) comprise about 25% of all intestinal microflora. Lactobacilli ferment dietary fiber
carbohydrates to lactic acid and short chain fatty acids, contributing to the slightly acidic colonic
pH. Lactobacolli also enhance epithelial barrier integrity by reducing pathogenic load and
reduce risk for developing colon cancer by binding heterocyclic mutagens, deconjugating bile
acids and binding and metabolizing cholesterol. Lactobacilli also ameliorate symptoms of
lactose intolerance in individuals with inadequate lactase production by secretion of betagalactosidase
(lactose →glucose + galactose). Lactobacilli suppress growth of pathogenic
species by a variety of mechanisms, including maintaining a slightly acidic colonic pH, binding to
adhesion proteins on pathogens (“competitive exclusion”), secretion of adhesion-inhibiting
proteins, competing for adhesion sites on enterocytes, secretion of species-specific antibiotics
(such as acidolin, acidophilin, lactobacilin, and lactocidin), secretion of hydrogen peroxide,
stimulation of GALT production and secretion of secretory IgA (sIgA), inhibition of bacterial
enzymes (including glucuronidase, beta-glucuronidase and nitroreductase) and stimulation of
colonic peristalsis (reducing time for colonocyte- pathogen interactions).
al fermentation
of fermentable dietary fibers results in the production of
Microbishort chain fatty acids (SCFA’s;
acetate, propionate, butyrate),
Butyrate is metabolized to
_______ within colonocytes.
acetyl CoA
Acetyl CoA is the primary energy source for colonocytes and is
required for the formation and maintenance of intercellular “tight junctions.”
The ______ contains about 50% to 60% of the total number of immune cells in
the body, scattered throughout the intestinal tract. As the “first line of defense” against
environmental assault, ______ provides both cell-mediated immunity and humoral immunity
via secretory IgA.
The GALT
