BIOL 404-Exam 4-GI 20
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bile pigments are mostly made up of what?
Why is bile yellow?
Mostly made of billirubin
What is billirubin formed from?
Heme portion of hemoglobin when damaged RBC’s are digested in spleen and liver
What is formed from the Heme portion of hemoglobin when damaged RBC’s are digested in spleen and liver?
What gives feces a brown color?
Acidified billirubin by bacterial enzymes in the colon
What give urine its yellow color?
bile salts are synthesized and secreted bywhat?
What is the action of bile salts?
What are the four main purposes of bile salts?
- Neutralizes HCl
- Emulsify fats
- Cholesterol excretion
- Aids excretion of metabolic end products
What are components of bile?
- Metabolic waste
What role does Bile play in Cholesterol secretion?
Cholesterol is extracted from the blood and excreted in the bile
Approximately what percent of bile salts that enter the small intestine are returned to the liver?
How are bile salts returned to the liver?
- Sodium-coupled transporters in the ileum
- Then, returned via the hepatic portal vein
What is enterohepatic circulation?
the cycling of bile salts
What percent of bile salts are newly synthesized (uncirculated)
What hormone controls the flow of bile into the small inetstine?
Gastric emptying is inhibited by what?
fat in the small intestine
What is the size of the small intestine?
- 1.5 inches diameter
- 9 ft long
What are the parts of the small intestine?
What is the initial short segment of the small intestine called?
What is the second 40% of the small intestine called?
What is the last 60% of the small intestine called?
What do Small intestine secretions mainly contain?
Salt, water, and mucus
What is the purpose of salt, water and mucus secretions of the small inetstine?
- maintain fluidity
- solubilize materials in chyme
- lubricate and protect mucosa
What is the purpose of motility in the small intestine?
- Brings contents into contact with epithelial cell membrane enzymes and transporters
- moves undigested material to large intestine
What three places does digestion of nutrient occur in the small intestine?
- Epithelial membrane
- inside epithelial cells (peptidases)
What three types of absorption mechanisms exist in the small intestine?
- Receptor mediated active and passive transport
- Chylomicron formation
How much water is secreted by the small intestine per day?
Where is water and salt secreted from in the small intestine?
The base of the villi
What stimuli control the secretion of water into the small intestine?
- Secretion of electrolytes
- Presence of hypertonic chyme
What are segmentation contractions of the small intestine?
Contractions that mix chyme moving it both up and down the GI
What is the purpose of segmentation contraction?
- Mix chyme with digestion juices
- Bring chyme in contact with intestinal wall
What causes Segmentation contractions?
- Food intake
- Presence of chyme
In the absence of segmentation contractions, what does the small intestine look like?
In the presence of segmentation contractions, what does the small intestine look like?
Do segmentation contractions travel?
No they occur at the same locations
What is the frequency of segmentation contractions?
- 12 per minute in the duodenum
- decreasing to 9 per minute in the ileum
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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