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bile pigments are mostly made up of what?
Mostly bilirubin
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Why is bile yellow?
Mostly made of billirubin
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What is billirubin formed from?
Heme portion of hemoglobin when damaged RBC’s are digested in spleen and liver
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What is formed from the Heme portion of hemoglobin when damaged RBC’s are digested in spleen and liver?
Bilirubin
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What gives feces a brown color?
Acidified billirubin by bacterial enzymes in the colon
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What give urine its yellow color?
bilirubin
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bile salts are synthesized and secreted bywhat?
hepatocytes
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What is the action of bile salts?
emulsify fats
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What are the four main purposes of bile salts?
- Neutralizes HCl
- Emulsify fats
- Cholesterol excretion
- Aids excretion of metabolic end products
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What are components of bile?
- bicarbonate
- lecithin
- cholesterol
- Metabolic waste
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What role does Bile play in Cholesterol secretion?
Cholesterol is extracted from the blood and excreted in the bile
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Approximately what percent of bile salts that enter the small intestine are returned to the liver?
95%
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How are bile salts returned to the liver?
- Sodium-coupled transporters in the ileum
- Then, returned via the hepatic portal vein
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What is enterohepatic circulation?
the cycling of bile salts
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What percent of bile salts are newly synthesized (uncirculated)
5%
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What hormone controls the flow of bile into the small inetstine?
CCK
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Gastric emptying is inhibited by what?
fat in the small intestine
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What is the size of the small intestine?
- 1.5 inches diameter
- 9 ft long
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What are the parts of the small intestine?
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What is the initial short segment of the small intestine called?
Duodenum
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What is the second 40% of the small intestine called?
Jejunum
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What is the last 60% of the small intestine called?
ileum
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What do Small intestine secretions mainly contain?
Salt, water, and mucus
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What is the purpose of salt, water and mucus secretions of the small inetstine?
- maintain fluidity
- solubilize materials in chyme
- lubricate and protect mucosa
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What is the purpose of motility in the small intestine?
- mixes
- Brings contents into contact with epithelial cell membrane enzymes and transporters
- moves undigested material to large intestine
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What three places does digestion of nutrient occur in the small intestine?
- Lumen
- Epithelial membrane
- inside epithelial cells (peptidases)
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What three types of absorption mechanisms exist in the small intestine?
- Diffusion
- Receptor mediated active and passive transport
- Chylomicron formation
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How much water is secreted by the small intestine per day?
1500mL
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Where is water and salt secreted from in the small intestine?
The base of the villi
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What stimuli control the secretion of water into the small intestine?
- Secretion of electrolytes
- Presence of hypertonic chyme
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What are segmentation contractions of the small intestine?
Contractions that mix chyme moving it both up and down the GI
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What is the purpose of segmentation contraction?
- Mix chyme with digestion juices
- Bring chyme in contact with intestinal wall
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What causes Segmentation contractions?
- Food intake
- Presence of chyme
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In the absence of segmentation contractions, what does the small intestine look like?
A tube
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In the presence of segmentation contractions, what does the small intestine look like?
Ovoid segments
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Do segmentation contractions travel?
No they occur at the same locations
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What is the frequency of segmentation contractions?
- 12 per minute in the duodenum
- decreasing to 9 per minute in the ileum
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How are segmentation contractions are initiated?
- By slow wave electrical activity generated by pacemaker cells in or associated with the circular smooth muscle layer and is conducted via gap junctions
- Excitatory neurotransmitters and hormones can enhance this
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