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BIOL 103 Chapter Notes -Ford Power Stroke Engine, Chitin, Plasmolysis

Course Code
BIOL 103
Peter T Boag

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Biology 103 Readings
Page 899 Ruminants
- Herbivores do not have cellulase to digest cellulose
- Rely on microbes living within their digestive tracts to digest the cellulose
- Microbes break down the cellulose into monosaccharides that can be absorbed along with
other by-produce of digestion
- Ruminants have complex stomachs consisting of several chambers, beginning with three
outpouchings of the lower esophagus collectively referred to the forestomach
- Forestomach composed of rumen, reticulum, and omasum
- Rumen and reticulum contain microbes
- Omasum absorbs some of the water and salts released from the chewed and partially
digested food
- Tough, partially digested food (the cud) is occasionally regurgitated, rechewed, and
swallowed again
- Partially digested food, microbes, and the by-products of microbinal digestion reach the
true stomach, the abomasum
- Abomasum contains the acid and proteolytic enzymes typical of other vertebrate
- After the abomasum, materials pass intestine to complete digestion and absorption
- Some microbes remain in the rumen and quickly multiply to replenish their population
Page 899-900 Absorption
- Mostly occurs in the small intestine
- Digestion products get absorbed across the epithelial cells and enter the blood
- Vitamins and minerals are absorbed too
- Water is absorbed by osmosis
- Infoldings and specializations along the small intestine help it carry out absorption and
- Villi: finger-like projections extending from the liminal surface into the lumen of the small
intestine; they aid digestion and absorption
- Microvilli: small projections in the surface membranes of epithelial cells in the small
- Brush Border: the combination of villi and microvilli in the small intestine, which
increase the surface area about 600-fold over that of flat-surfaced tube having the same
length and diameter
- Likelihood of ingested food particle encountering a digestive enzyme and being absorbed
across the epithelium is very high; therefore, digestion and absorption proceed rapidly
- Lacteal: a vessel in the centre of each intestinal villus; lipids are absorbed by the lacteals,
which eventually empty into circulatory system
- Fat absorbed in the small intestine exists as bulky protein-bound particles that cannot
enter capillaries too large
- Absorbed fat enters larger, wider lacteals, that are part of lymphatic system
- Materials absorbed by lacteals empty into the circulatory system
- Other nutrients are absorbed directly into the capillaries then veins
- Three major parts of small intestine: duodenum, jejunum, and ileum
Figure 6.12 Osmosis
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