Transcript Digestive System

Digestive System
[Day 2]
Main Ideas
4. Small Intestine
• Stomach  pyloric sphincter  small intestine
• First section of intestine = duodenum
• Chemical digestion!!
• Pancreas & liver deposit enzymes
• Digestion Works Video
4. Small Intestine
• First section of intestine = duodenum
• Duodenal cells produce hormones
• Secretin – stimulated by acid in chime
• CCK (cholecystokinin) – stimulated by
partially digested protein & fat
•  both target pancreas & liver – protome
increased secretions
4. Small Intestine
• Slightly basic (pH = 8.5)
• Bile
• From liver; emulsifies fat [into small droplets]
• Pancreatic fluid:
• has NaHCO3 [Neutralize stomach chime!]
• Amylase [starch + H2 O → maltose]
• Trypsin [protein + H2 O → peptides]
• Lipase [fat + H2 O → glycerol + fatty acids]
• Nuclease [DNA/RNA +H2 O → nucleotides]
4. Small intestine
• Smaller diameter,
larger length! [6
m!]
• Villi & microvilli
• Folds to increase
surface area
• Absorbs nutrients
across intestinal
wall, into blood
vessels
Villi
Microvilli
Capillaries (aa and
glucose enters)
Villi
Lacteal (fat and glycerol enters)
Lymph drains lacteal
4. Small Intestine
• Mucosa of villi also secrete enzymes
• Peptidase [𝑝𝑒𝑝𝑡𝑖𝑑𝑒𝑠 + 𝐻2 𝑂 → 𝑎𝑚𝑖𝑛𝑜 𝑎𝑐𝑖𝑑𝑠]
• Maltase [𝑚𝑎𝑙𝑡𝑜𝑠𝑒 + 𝐻2 𝑂 → 𝑔𝑙𝑢𝑐𝑜𝑠𝑒]
• Nucleosidase [𝑛𝑢𝑐𝑙𝑒𝑜𝑡𝑖𝑑𝑒𝑠 → 𝑠𝑢𝑔𝑎𝑟 +
𝑝ℎ𝑜𝑠𝑝ℎ𝑎𝑡𝑒 𝑔𝑟𝑜𝑢𝑝 + 𝑛𝑖𝑡𝑟𝑜𝑔𝑒𝑛𝑜𝑢𝑠 𝑏𝑎𝑠𝑒]
5. Large Intestine
• Finishes absorbing water &
salts
• Bacteria (E. coli) –
produce vitamins, finish
breakdown of cellulose
• Prepares feces for
elimination
Transverse Colon
Ascending
Colon
Descending
Colon
Cecum (blind
end of intestine)
Appendix (no function;
may help infection, subject to
inflammation; appendicitis)
Rectum
Sigmoid
Colon
Interesting Fact
• contains bacteria (including E.coli.) that live
on unabsorbed and undigested nutrients
• the bacteria ferment any remaining
carbohydrates and release H+, CO2, and
methane gas.
(flatus (flatulence)
• by-products of the bacterial digestion account
for the color and the smell of the feces.
6. Anal Sphincter
• External anal sphincter is under voluntary control
Elephant Guts
Elephant guts online
stop after 1:42
Continue on to elephant guts 2
Videos
• Scrubs Song
• Why do I have Gas
• Constipation
To Do’s
• Q’s [next slide]
• Provincial Questions # 2, 6, 10, 11, 13, 15?, 21, 29,
32-34, 36, 39, 40, 41, 45, 46, 47, 50-52, 55
• Dictionary
• Duodenum; villi
Questions
1. Which organs are important for absorbing
nutrients? Water?
2. What is the duodenum? Why do we care?
3. How do villi help in absorption?
4. What is the role of bacteria in the large
intestine?
5. Does mechanical digestion occur anywhere in
the stomach  anus? Why/Why not?