Unit 4 Digestion
62. How are bile salts able to emulsify lipid molecules (Hint: think about the structure of bile salts)
Lipids are hydrophobic. I need to emulsify the fat. The nonpolar sides of the bile salts with align themselves with the lipid, the polar parts face the water. so this makes my lipids slightly more soluble in water Pancreatic lipase and colipase will help digest the triglyceride and break into mono and two free fatty acids As the bile salts are surrounding the lipids and making them smaller through emulsification, I now have a tiny lipid droplet that contains triglycerides and PL and colipase=a micelle
55. What are the two types of diarrhea? a. What is the physiological mechanism (what causes) for each?
Osmotic: -getting diarrhea from the things you have eaten. Due to osmolarity of the lumen based upon the content of chyme from diet. Secretory: -about solutes. The columnar epithelium secreted anions (mainly Cl- ions) into the lumen as a defense mechanism against pathogens. These cells cause increase in osmolarity of the contents in lumen=attracts more water. more osmolarity=more water comes in=more distension=the faster it moves. Happens due to illness, parasite. Giardia will give you secretory diarrhea several days later. that's why you secrete Cl- to protect yourself
56. Name the enzymes involved in lipid digestion and in what region of the digestive tract do they primarily function.
Pancreatic lipase and colipase, they are in the lumen of the small intestine
12. Understand the structural arrangement of the small intestine from the plicae circularis to the microvilli of the columnar cells.
Plicae circularis are covered by villi, and the epithelial cells on top of the folds are covered by microvilli on their apical side=HUGE increase in SA Simple columnar epithelium
27. How do Prilosec/Nexium and Tagament/Zantac/Pepsid AC work - Be specific
Prilosec and Nexium: PPI blockers, Prevents the k+ from attaching to h/k antiporter. If the pump can't work, I can't put protons into the gastric pit, which increases pH in stomach. Zantac and Tagamet and pepsid AC : h2 blockers. I can also control the h+ that are pumped out of the cell by taking an H2 blocker to block the histamine H2 receptor on the parietal cell. If histamine can't attach to receptor, the parietal cell isn't stimulated as much. Level of proton production goes down, pH of stomach increases
2. What is the difference (structurally - be detailed - and functionally) between rugae and plicae?
Rugae are characteristic features of the stomach. These longitudinal folds (or ridges) enable the stomach to distend as it fills with food. Plicae circulares are circular folds in the mucosa in the small intestine that increase the surface area for nutrient absorption.
???39. How are the enterogastric, gastroenteric and gastroileal reflexes different?
The enterogastric reflex releases acid in the duodenum or in the stomach, and suppresses the release of digestive proteins. The gastroileal reflex works with the gastrocolic reflex to stimulate the urge to defecate. It does so by opening the ileocecal valve and moving the digested contents from the ileum of the small intestine into the colon for compaction.
22. What role in digestion do G-cells have? a. For each of the above, what is the stimulus for each? b. For each of the above, what is their function? c. For each of the above, what organs do they come from and interact with?
When the vagus nerve (parasympathetic NS) stimulates the submucosal plexus, it releases Ach that lands on its receptors on the G cell surface in stomach. •In response, G cell produces gastrin hormone that goes through circulation. •G cells are also stimulated by caffeine, alc, A.A. which leads to gastrin --> acid produced in stomach
21. What terms describe: a. The movement of material through the digestive system? b. The mixing and churning of material in small intestine?i. Which specific muscle group is responsible both a and b?
a. Peristalsis b. segmentation c. muscularis externa
44. Explain why a person who is severely lactose intolerant would experience material moving faster through the digestive tract and what would be the condition of fecal material when leaving the body?
because you can't digest lactose, it remains in the lumen of the SI as a solute since water follows solutes, water will remain in the lumen as well water creates distension and stretch, activating the reflex so peristalsis occurs quicker and materials move faster and don't have time to absorb therefore the condition of the fecal material is watery and it moves through your system very fast
48. Why is bile needed, what is its function?
bile salt coat the fat droplets, they help emulsify and break down the fat into small fatty acids
47. Describe the structure of bile salts - why are they considered to be amphipathic? a. Which side binds with water vs. lipids?
bile salts have both polar and nonpolar ends=amphipathic structure The nonpolar sides of the bile salts with align themselves with the lipid The polar parts align with the water
????50. How are lipids absorbed into intestinal cells?
by diffusion
5. Where in the stomach would you locate the more liquidity and the more solid material (chyme)?
chyme at beginning of stomach-fundus liquid at end of stomach-pylorus
13. What is the function of the pancreas? a. Did you name the buffer, the 3 different enzymes and the different hormones
creates Buffers-sodium bicarbonate, enzymes and hormones 1) Pancreatic lipase 2) Pancreatic alpha-amylase 3) Proteolytic enzymes All come from acini cells Hormones are insulin and glucagon, secreted by isles of Langerhan
37. Explain why water leaves the digestive tract?
due to osmosis: water will go into the blood because it is more hypertonic in the blood. The more solutes I absorb, the more water will follow. depends upon the osmotic value of the chyme
32. Which reflex is triggered by chyme entering the duodenum?
enterogastric reflex so that I can have time to absorb the nutrients
33. What is the function of the enterogastric reflex?
enterogastric reflex: stimulated by the presence of acid levels in the duodenum or in the stomach. It releases acids and controls the release of stomach proteins such as gastrin.
6. How is the muscularis externa of the various areas (regions) of the digestive system different?
esophagus: 1st third is pure skeletal muscle tissue (I can control when I swallow), once it gets past epiglottis, then 2nd third is combo of skeletal and smooth, 3rd third is pure smooth muscle. stomach: has an extra oblique layer under circular layer. SI: regular muscularis externa LI: no longitudinal muscle tissue at ends. They are gathered into taenia coli belts.
31. Which reflex is triggered by the distension of the stomach?
gastroenteric reflex
23. How do parietal cells generate H+?
h2o within the parietal cell is split into a H+ ion and hydroxide ion. h+ is pumped into the lumen of the gastric gland by an h+/k+ pump •H+ proton will start to build up in parietal cell so I need to pump the proton out into the lumen. Antiporter called a proton pump (requires ATP) that pumps h+ out and pumping k+ in. also leaky channel for k+ to leak back out. So now I have both H+ and Cl- ions in the gastric pit to make HCL.
14. What is the function of hepatocytes and Kupffer cells?
hepatocyte: makes bile and dumps it into the bile canaliculi which ends up in the gallbladder to be stored Kupffer cells: liver macrophages and play a critical role in maintaining liver functions. Under physiological conditions, they are the first innate immune cells and protect the liver from bacterial infections.
??41. Where does most of the absorption take place in the intestinal tract?
jejenum, 90% of absorption and ascending colon
64. Outline the steps of lipid digestion starting with lipids in the chyme to lipids entering the lacteal of the small intestine. This question really is all of the above combined :O)
look at lipid digestion above
38. Why is fiber important in the diet?
more volume of chyme/water in the lumen. this leads to more stretch/distension, higher rate of peristalsis
36. How would the volume of material in the lumen affect the rate that material passes through the colon?
more volume of chyme/water in the lumen. this leads to more stretch/distension, higher rate of peristalsis so it passes passes.
51. Do bile salts (bile) enter the intestinal cells? a. If so, how and If not what happens to them? 52. What happens to the monoglycerides and fatty acids after they enter the intestinal cell? -Be specific
no, they are recycled They combine with cholesterol and proteins to form chylomicrons
Do bile salts enter the cells of the small intestine? Explain your answer
no, they can't endocytose into the cell. instead, they are recycled to emulsify fat again
??57. What are Lipids (triglycerides) are composed of (made up of)?
one monoglyceride and three free fatty acids
3. How is the mucosal layer different in the oral cavity, stomach, duodenum, jejunum and colon and anus? Did you think about epithelium type, layers and "structural arrangement" of the mucosa?
oral: Submandibular salivary gland Makes 70% of saliva. mucins provides lubrication so food goes down esophagus, buffers & salivary amylase Epithelium - two types •Keratinized stratified squamous •Nonkeratinized and less stratified regions stomach: has an extra oblique layer under circular layer. made up of simple columnar epithelium, mucus folds in rugae shapes for maximum SA and expansion. contains gastric pits jejunum: HUGE SURFACE AREA, contains Circular folds "Plicae Circularis". on top of PC is Intestinal Villi, then Simple columnar epithelium with microvilli on top duodenum: Brunner's glands to produce mucus to protect epithelial cells, not much SA for absorption colon: •Simple columnar epithelium, a lot more goblet cells to produce mucus. No rugae folds, very flat surface. Less SA, not good at absorption •Muscularis externa- no longitudinal muscle tissue at ends. They are gathered into taenia coli belts. anus: anal canal: columnar epithelium anus: keratinized stratified squamous
30. What is the pH of the stomach vs. early part of duodenum vs. early part of the jejunum and what causes the pH to have that value?
pH of stomach is 1-1.5 duodenum: jejunum:
26. What are PPI's?
proton pump inhibitor medication. Prevents the k+ from attaching to h/k antiporter. If the pump can't work, I can't put protons into the gastric pit, which eventually ends up in the lumen of the stomach.
17. What is the function of the submucosal plexus/plexus of Meissner? (What does it stimulate/innervate?)
releases Ach and activates the chief cells, parietal cells, G cells of the stomach
Which layer of the serous membranes is responsible for organs being retroperitoneal, and which organs are retroperitoneal?
retroperitoneal: uterus, pancreas, bladder, duodenum, rectum. a portion of esophagus they are all under/covered by the parietal peritoneum
59. What do we need to do to the large lipid molecules found in the chyme, and why? How does this happen?
see lipid digestion
60. Do whole lipids (triglycerides) enter the cell of the small intestine? If so, how is this done. If not, what happens to them, what are they broken down into?
see lipid digestion
40. Lipids are not absorbed in the same way as other nutrients are, so how are they different?
small lipids can have simple diffusion into bloodstream Pancreatic lipase and colipase will help digest the triglyceride and break into mono and two free fatty acids. it will travel through the cell and merge with cholesterol and protein and become a chylomicron. it will be released into the lacteal. lacteals merge into lymphatic vessels, and the LV get dumped into veins.
63. What role does the smooth endoplasmic reticulum (SER) and golgi apparatus have with lipid digestion?
the SER: helps to make lipids. reassemble and make triglyceride Golgi: creates secretory vesicles for chylomicrons to exocytose
34. What would cause a greater osmotic draw of water into the lumen of the small intestine - someone who had a meal high in indigestible plant matter or someone who had a large steak meal? Explain your reason.
the large steak meal bc you can't break down fibers as much as you can break down proteins. so i will have fewer solute particles from the veggie meal compared to the steak meal (bc steak can be protein down into billions of AA, but you can't break down cellulose from celery)
20. Why is a low pH needed in the stomach and what is that pH value? a. Besides aiding in activation of enzymes what are other benefits of the low pH in the stomach?
the low pH of 1-1.5 is useful for unraveling proteins making them easier to digest (chemical digestion) and killing bacteria and other pathogens.
61. What role do bile salts have with lipid digestion?
they coat the fat droplets to emulsify the fats and break them down. they form a micelle coating the fat droplets on the outside
9. What is the function of Brunner's glands and where are they specifically located? Which aspect of the autonomic nervous system will affect these glands and how are they affected?
they produce mucus to protect epithelium cells from low pH. Begins in cephalic phase to protect myself from the acidity of food that will show up many hours later
11. What are the different functions of various regions of the small intestine?
•Duodenum: -control the rate of gastric emptying and motility •Jejunum: -90% Majority of chemical digestion/absorption is done here. LOTS of SA •Ileum: -some absorption of final nutrients that weren't absorbed by D and J
What role in digestion do parietal cells have? a. For each of the above, what is the stimulus for each? b. For each of the above, what is their function? c. For each of the above, what organs do they come from and interact with?
•When the vagus nerve (parasympathetic NS) stimulates the submucosal plexus, it releases Ach that lands on its receptors on the G cell surface. •In response, G cell produces gastrin hormone that goes through circulation. When gastrin lands on parietal cells, they produce HCL Ach and H2 (histamine) receptors will also stimulate parietal cell activity
4. How does the muscular externa seen in the esophagus change as it progresses from the oral cavity to the stomach?
-By 1/3rds. 1st third is pure skeletal muscle tissue (I can control when I swallow), once it gets past epiglottis, then 2nd third is combo of skeletal and smooth, 3rd third is pure smooth muscle.
What role in digestion do secretin, somatostatin? a. For each of the above, what is the stimulus for each?b. For each of the above, what is their function?c. For each of the above, what organs do they come from and interact with?
-Low pH triggers Secretin release, which causes - decrease in Gastric secretions and motility - increase in pancreas release of HCO3- - increase Liver release of bile Somatostatin -When there is low pH/high HCL=stronger the neg fb. -To G cell --> decrease in gastrin produce --> less parietal cells --> less production of HCL --> pH increases.
19. What is the function of salivary amylase, lingual lipase? a. How does the stomach environment affect the function of salivary amylase and lingual lipase?
-Salivary amylase: begins chemical digestion of carb -Lingual lipase: begins chemical digestion of lipids. Both enzymes prefer slightly alkaline pH
53. What is a chylomicron? a. Where did it come from? What is it transporting? Where it is headed to ultimately?
-it is fat that is combined with cholesterol and proteins -it is transporting lipids -it heads to lacteal
49. Describe the structure of a triglyceride and what effect do lipases have on them? What is a micelle?
-one monoglyceride and three free fatty acids -Pancreatic lipase and colipase will help digest the triglyceride and break into its constituent parts -a micelle is a tiny lipid droplet that contains triglycerides and PL and colipase
42. In a normal healthy person approximately how much liquid enters the digestive system and how much remains in feces?
1500 mL, by the time for feces: 150-200 mL
45. In response to the local reflexes for defecation how do the internal and external sphincters of the anus respond?
Baroreceptors are stimulated by distension of LI wall. Stretch Send message up reflex-unipolar somatic sensory neuron up to spinal cord (unipolar, dorsal root ganglion) monosynaptic connection to a motor neuron in the anterior grey horn. Parasympathetic nervous system causes smooth muscles of internal anal sphincter to relax. I constrict the externals at the same time. Then I have to give conscious permission to relax the externals by: The anterior grey horn sends a message to somatic motor, nerve impulse all the way down.
15. What is the function of the gallbladder and of bile salts? a. What route does bile take from the hepatocytes to the duodenum or gall bladder?
Bile salts help with the digestion of fats in our bodies the gallbladder stores bile Each hepatocyte makes bile and dumps it into the bile canaliculi, travels to the bile duct. Opposite the flow of the vein and artery. Bile duct merges into R and L hepatic ducts, the eventually to the duodenum
10. What is the function of the stomach?
Body and fundus (origin of ghrelin) •Mixing and storage •Gastric glands, under gastric pit (chief and parietal cells) Pylorus contains •Mucus glands •Enteroendocrine cells (G cells & D cells) •Pyloric sphincter -Empties into the duodenum
??What role in digestion do histamine and CCK (cholecystokinin) have?a. For each of the above, what is the stimulus for each?b. For each of the above, what is their function?c. For each of the above, what organs do they come from and interact with?
CCK responds to lipids and digested proteins to -decrease Gastric secretions and motility - Pancreatic enzymes released, Acini cells will receive CCK signal to digest... » Pancreatic alpha-amylase. carbs » Pancreatic lipases. lipids » Proteolytic enzymes. Proteins Contract gallbladder - Relax hepatopancreatic sphincter Histamine:
16. What are the 3 phases of digestion?
Cephalic, Gastric, Intestinal
What role in digestion do chief cells and D-cells have? a. For each of the above, what is the stimulus for each? b. For each of the above, what is their function? c. For each of the above, what organs do they come from and interact with?
Chief cells; stimulated also by gastrin and Ach. They make inactive pepsinogen that when it is exposed to HCL at pH 1.5-2, it actives pepsinogen to pepsin. THEY DON'T SECRETE PEPSIN, ONLY PEPSINOGEN!!!!!!!! D-cells: Release somatostatin hormone in response to HCL, works as neg fb The more HCL lands on d cell receptors, the more somatostatin hormone is released --> stronger the neg fb. To G cell --> decrease in gastrin produce --> less parietal cells --> less production of HCL --> pH increases.
18. What is the function of the myenteric plexus? (What does it stimulate/innervate?)
Contracts and relaxes circular and longitudinal layers
??What role in digestion do mucus cells and ECL cells have? a. For each of the above, what is the stimulus for each? b. For each of the above, what is their function? c. For each of the above, what organs do they come from and interact with?
ECL found in epithelium of stomach, they release histamine which lands on H2 receptors. Gastrin and NT tells ECL cells to release histamine Mucus cells produce mucus to protect epithelium cells from low pH.
7. In a gastric pit and gastric gland explain the different cell types and their various functions and how they interact in digestion.
G cells: stimulated by caffeine, alc, A.A. which leads to gastrin --> acid produced in stomach parietal cells: HCL and makes intrinsic factor Chief cells; stimulated also by gastrin and Ach. They make inactive pepsinogen that when it is exposed to HCL at pH 1.5-2, it actives pepsinogen to pepsin. enterendocrine: makes hormones D cells: The more HCL lands on d cell receptors, the more somatostatin hormone is released --> stronger the neg fb. To G cell --> decrease in gastrin produce --> less parietal cells --> less production of HCL --> pH increases.
8. In which region/s of the stomach would you find G-cells, parietal cells, chief cells, "D" cells and mucus cells?
G-cells: found in pylorus parietal cells: they are the epithelial cells, located in gastric glands found in lining of fundus and stomach. chief cells: found in body and fundus "D" cells: found in pylorus mucus cells: found in the gastric pit
What role in digestion do gastrin and GIP have? a. For each of the above, what is the stimulus for each?b. For each of the above, what is their function?c. For each of the above, what organs do they come from and interact with?
GIP -Lipids, carbohydrates (glucose) triggers it to release • GIP (gastric inhibitory peptide). GIP will... - decrease Gastric secretions and motility - increase Insulin from pancreas (main job is to triggers insulin from pancreas due to the glucose in chyme). Which cells will receive GIP hormone? Endocrine cells from Isles of Langerhans - increase Lipid synthesis in adipose Gastrin -Higher levels of protein triggers • G-cell activity in duodenum, G-cells make gastrin
???46. Name the two different glucose transporters found in the epithelium of the small intestine. a. Which transporter is found on the apical side and which on the basal side?
GLU transporter-on basal side Na+/GLU transporter-on apical side
25. What bacterium causes gastric ulcerations?
H. pylori
35. Who would have more water remain in lumen of the jejunum region and entering the ileum portion of the small intestine - someone who had a meal high in indigestible plant matter or someone who had a large steak meal? Explain your reason.
High fiber meal leads to more solutes that are not absorbed. Since fewer solutes are being absorbed, fewer water molecules will follow So more water remains in the chyme in the lumen of the jejunum
29. What are H2 inhibitors in terms of the physiology of the digestive process?
I can also control the h+ that are pumped out of the cell by taking an H2 blocker to block the histamine H2 receptor on the parietal cell. If histamine can't attach to receptor, the parietal cell isn't stimulated as much. Level of proton production goes down, pH of stomach increases
24. What is and what causes the alkaline tide?
If histamine can't attach to receptor, the parietal cell isn't stimulated as much. Level of proton production goes down, pH of stomach increases. due to the more bicarbonates that go out to the blood, pH will increase
43. What is the function of the large intestine and rectum?
LI: absorbing water, absorbing vitamins, and forming and propelling feces toward the rectum for elimination rectum: