Digestive System Part 2
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How long is the small intestine?
5.5-6m
What is the physical digestion of the small intestine?
Segmentation (back and forth movement as peristalsis moves forward)
3 regions of small intestine
Duodenum Jejunum Ileum
Is duodenum the most important site of chemical digestion?
Yes
What happens when chyme enters duodenum?
Releases hormone secretin which tells pancreas to release bicarbonate (acid neutralizer
What is villi that covers the surface of the small intestine?
Projections (finger shaped) that line the small intestine
What is villi covered with
Microvilli
What is villi called?
Brush border
What does chemical digestion in small intestine use?
Carbohydrates to digest disaccharides (sucrose, Maltase and lactase are the carbohydrases)
What is lactose intolerance?
Inability to produce lactase/last of lactase
What does the pancreas include?
Pancreatic fluid
What does Pancreatic fluid contain?
Bicarbonate Trypsin and Chymotrypsin (proteases that digest small polypeptides into dipeptides) Erepsin Pancreatic amylase Lipase
What does the liver do?
Receives chemical signal from duodenum called CCK (cholecystokinin) which tells liver to secret bile
What happens with a blockage of bile?
Leads to Jaundis
What do Bile salts do?
Help emulsify fats (physical digestion) by breaking larger fats into smaller fats
What does liver also store?
Glycogen (extra sugar)
What is Jaundis?
Build up of a waste protein in blood due to lack of bile
What does the gallbladder do?
Stores extra bile from liver and injects it into the duodenum when fats are present
What does carbohydrase include?
Salivary amylase, pancreatic amylase, sucrose, maltase, and lactase
Proteases
Pepsin, trypsin, erepsin, chymotrypsin, and peptidases
Fat digestion and absorption
Bile (emulsifies) and lipases (digests) Lipids absorb into lymph system (lacteals run parallel to circulatory system)
Look at answer (Nucleic acid digestion and absorption)
• Dna digested in small intestine by nucleuses from pancreas yields nucleotides (monomers of Dna) • Nucleosidases hydrolyze nucleotides into bases, sugars, and phosphates which are absorbed by active transport into cells make DNA
Look at answer (macromolecule digestion and absorption)
• All 4 macromolecules hydrolyzed through use of enzymes • All are absorbed into bloodstream through active transport in the small intestine Lipids = absorbed into lymph system which transports them to the circulatory system All nutrients travel through hepatic portal vein leading to liver for detoxification
Large intestine
Wider than small intestine but 1.5 m long