Which of the following glandular secretions involved in digestion ...
Which of the following glandular secretions involved in digestion ...
Which of the following glandular secretions involved in digestion ...
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<strong>Which</strong> <strong>of</strong> <strong>the</strong> <strong>follow<strong>in</strong>g</strong> <strong>glandular</strong> <strong>secretions</strong><br />
<strong><strong>in</strong>volved</strong> <strong>in</strong> <strong>digestion</strong> would be most likely<br />
to be released <strong>in</strong>itially as <strong>in</strong>active<br />
precursors?<br />
– A. carbohydrate-digest<strong>in</strong>g enzymes<br />
– B. fat-solubiliz<strong>in</strong>g bile salts<br />
– C. acid-neutraliz<strong>in</strong>g bicarbonate<br />
– D. prote<strong>in</strong>-digest<strong>in</strong>g enzymes<br />
– E. hormones such as gastr<strong>in</strong>
LE 41-22<br />
Liver<br />
Key<br />
Stimulation<br />
CCK<br />
Enterogastrone<br />
Gallbladder<br />
Stomach<br />
Inhibition<br />
Gastr<strong>in</strong><br />
Pancreas<br />
Duodenum<br />
Secret<strong>in</strong><br />
CCK
Absorption <strong>of</strong> Nutrients<br />
• The small <strong>in</strong>test<strong>in</strong>e has a huge surface<br />
area, due to villi and microvilli that are<br />
exposed to <strong>the</strong> <strong>in</strong>test<strong>in</strong>al lumen<br />
• The enormous microvillar surface<br />
greatly <strong>in</strong>creases <strong>the</strong> rate <strong>of</strong> nutrient<br />
absorption
LE 41-23<br />
Ve<strong>in</strong> carry<strong>in</strong>g blood<br />
to hepatic portal<br />
vessel<br />
Key<br />
Nutrient<br />
absorption<br />
Microvilli<br />
(brush border)<br />
Blood<br />
capillaries<br />
Muscle layers<br />
Villi<br />
Epi<strong>the</strong>lial<br />
cells<br />
Large<br />
circular<br />
folds<br />
Lacteal<br />
Epi<strong>the</strong>lial cells<br />
Intest<strong>in</strong>al wall<br />
Villi<br />
Lymph<br />
vessel
• Each villus conta<strong>in</strong>s a network <strong>of</strong> blood vessels and a<br />
small lymphatic vessel called a lacteal
• Am<strong>in</strong>o acids and sugars pass through <strong>the</strong> epi<strong>the</strong>lium <strong>of</strong> <strong>the</strong><br />
small <strong>in</strong>test<strong>in</strong>e and enter <strong>the</strong> bloodstream<br />
• After glycerol and fatty acids are absorbed by epi<strong>the</strong>lial<br />
cells, <strong>the</strong>y are recomb<strong>in</strong>ed <strong>in</strong>to fats with<strong>in</strong> <strong>the</strong>se cells<br />
• These fats are mixed with cholesterol and coated with<br />
prote<strong>in</strong>, form<strong>in</strong>g molecules called chylomicrons, which are<br />
transported <strong>in</strong>to lacteals
LE 41-24<br />
Fat globule<br />
Bile salts<br />
Fat droplets<br />
coated with<br />
bile salts<br />
Micelles made<br />
up <strong>of</strong> fatty acids,<br />
monoglycerides,<br />
and bile salts<br />
Epi<strong>the</strong>lium<br />
<strong>of</strong> small<br />
<strong>in</strong>test<strong>in</strong>e<br />
Epi<strong>the</strong>lium<br />
<strong>of</strong> lacteal<br />
Lacteal
The Large Intest<strong>in</strong>e<br />
• The large <strong>in</strong>test<strong>in</strong>e, or colon, is connected to<br />
<strong>the</strong> small <strong>in</strong>test<strong>in</strong>e<br />
• Its major function is to recover water that<br />
has entered <strong>the</strong> alimentary canal<br />
• Wastes <strong>of</strong> <strong>the</strong> digestive tract, <strong>the</strong> feces,<br />
become more solid as <strong>the</strong>y move through<br />
<strong>the</strong> colon<br />
• Feces pass through <strong>the</strong> rectum and exit via<br />
<strong>the</strong> anus
• The colon houses stra<strong>in</strong>s <strong>of</strong> <strong>the</strong> bacterium<br />
Escherichia coli, some <strong>of</strong> which produce vitam<strong>in</strong>s
After a meal <strong>of</strong> greasy french fries, which<br />
enzymes would you expect to be most<br />
active?<br />
– A. lipase, lactase, maltase<br />
– B. salivary and pancreatic amylase,<br />
disaccharidases, lipase<br />
– C. peps<strong>in</strong>, tryps<strong>in</strong>, chymotryps<strong>in</strong>, dipeptidases<br />
– D. gastric juice, bile, bicarbonate<br />
– E. sucrase, lipase, bile
Concept 41.5: Evolutionary<br />
adaptations <strong>of</strong> vertebrate digestive<br />
systems are <strong>of</strong>ten associated with<br />
diet<br />
• Digestive systems <strong>of</strong> vertebrates are<br />
variations on a common plan<br />
• However, <strong>the</strong>re are <strong>in</strong>trigu<strong>in</strong>g<br />
adaptations, <strong>of</strong>ten related to diet
Some Dental Adaptations<br />
• Dentition, an animal’s assortment <strong>of</strong> teeth, is one<br />
example <strong>of</strong> structural variation reflect<strong>in</strong>g diet<br />
• Mammals have specialized dentition that best<br />
enables <strong>the</strong>m to <strong>in</strong>gest <strong>the</strong>ir usual diet
LE 41-26<br />
Incisors<br />
Can<strong>in</strong>es<br />
Carnivore<br />
Premolars<br />
Molars<br />
Herbivore<br />
Omnivore
Stomach and Intest<strong>in</strong>al<br />
Adaptations<br />
• Herbivores generally have longer alimentary canals<br />
than carnivores, reflect<strong>in</strong>g <strong>the</strong> longer time needed to<br />
digest vegetation
LE 41-27<br />
Small <strong>in</strong>test<strong>in</strong>e<br />
Small<br />
<strong>in</strong>test<strong>in</strong>e<br />
Stomach<br />
Cecum<br />
Colon<br />
(large<br />
<strong>in</strong>test<strong>in</strong>e)<br />
Carnivore<br />
Herbivore
Symbiotic Adaptations<br />
• Many herbivores have fermentation<br />
chambers, where symbiotic microorganisms<br />
digest cellulose<br />
• The most elaborate adaptations for an<br />
herbivorous diet have evolved <strong>in</strong> <strong>the</strong> animals<br />
called rum<strong>in</strong>ants
LE 41-28<br />
Intest<strong>in</strong>e<br />
Rumen<br />
Reticulum<br />
Abomasum<br />
Esophagus<br />
Omasum
LE 41-23<br />
Ve<strong>in</strong> carry<strong>in</strong>g blood<br />
to hepatic portal<br />
vessel<br />
Key<br />
Nutrient<br />
absorption<br />
Microvilli<br />
(brush border)<br />
Blood<br />
capillaries<br />
Muscle layers<br />
Villi<br />
Epi<strong>the</strong>lial<br />
cells<br />
Large<br />
circular<br />
folds<br />
Lacteal<br />
Epi<strong>the</strong>lial cells<br />
Intest<strong>in</strong>al wall<br />
Villi<br />
Lymph<br />
vessel
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