Lesson 06: Digestive System Part II

A low or high pH will inhibit gastrin release? Why does that make sense?

A low pH will inhibit the secretion of gastrin. This is an example of a negative-feedback loop aimed at avoiding a stomach pH that is too acidic. Without this inhibition, gastrin would continue stimulating the parietal cells to release HCl, which could damage the stomach.

Cholera is a disease in which the absorption of water in the large intestine is inihibited. For those who die due to this terrible disease, what is the cause of death?

Because cholera results in the loss of large amounts of water, the main cause of death is dehydration. By drinking lots of water, someone who suffers from this disease may be able to wash the bacteria out with their stool.

*CRB* There are many other Pancreatic Enzymes that are secreted in inactive forms, like Procarboxypeptidase and Procollagenase. Would these more resemble steroid or protein hormone synthesis, and why?

Because these enzymes are first produced as a pro-enzyme, these would more resemble Protein Hormones, which are produced as Pre-Pro-Hormones, and will eventually be stored in vesicles waiting for release as Pro-Hormones.

Bile contains pigments and bile salts. What is the role of each?

Bile pigments simply give bile its color. Bile salts are responsible for emulsifying fat, allowing them to be digested and absorbed in the small intestine.

Diabetes results in a blood glucose level that is too high or too low? Why?

Diabetes results in a blood glucose level that is too high because insulin is unable to properly perform its function.

Diarrhea results when the large intestine absorbs too much or too little water? Constipation results when the large intestine absorbs too much or too little water?

Diarrhea results when the large intestine absorbs too little water, leaving too much in the stool. Constipation results when the large intestine absorbs too much water, leaving too little in the stool.

Lesson 6: Digestive System Part II

Lesson 6: Digestive System Part II

What happens to bile salts after assisting in the digestion and absorption of fats?

The bile salts will be absorbed by the ileum and carried back to the liver, where they will be recycled and used again.

Describe the structure of the hepatic lobule.

The hepatic lobule is a hexagon with one portal triad at each corner and many hepatocytes in the center. There is a central vein in which blood will collect and transport blood to the hepatic vein.

The exocrine pancreas releases many enzymes to aid in digestion. Match the following enzymes to their function. (1) Amylase (2) Lipase (3) Trypsin/chymotrypsin (A) Break down triglycerides into free fatty acids/ monoglycerides/ diglycerides/ glycerol (B) Break down starches into smaller carbohydrates (C) Break down protein into amino acids

(1) Amylase -> (B) Break down starches into smaller carbohydrates (2) Lipase -> (A) Break down triglycerides into free fatty acids/ monoglycerides/ diglycerides/ glycerol (3) Trypsin/chymotrypsin -> (C) Break down protein into amino acids

There are vessels that enter and leave the liver carrying specific items. Match the vessels with what they're carrying. (1) Portal Vein (2) Proper Hepatic Artery (3) Common Hepatic Duct (4) Hepatic Vein (A) carries oxygen-rich blood to the liver (B) carries nutrient-rich blood to the liver (C) carries nutrient-poor and oxygen-poor blood out of the liver (D) carries bile out of liver

(1) Portal Vein -> (B) carries nutrient-rich blood to the liver (2) Proper Hepatic Artery -> (A) carries oxygen-rich blood to the liver (3) Common Hepatic Duct -> (D) carries bile out of liver (4) Hepatic Vein -> (C) carries nutrient-poor and oxygen-poor blood out of the liver

The appendix is attached to which section of the large intestine? (A) Cecum (B) Transverse Colon (C) Ascending Colon (D) Sigmoid Colon

(A) Cecum The appendix is attached to the cecum.

Which hormone tells the gall bladder to contract, causing the ejection of bile from the gall bladder? (A) Cholecystokinin (B) Angiotensin (C) Betatropin (D) Ghrelin

(A) Cholecystokinin Cholecystokinin (CCK) will cause the contraction of the gall bladder, causing the ejection of bile from the gall bladder

What is the final duct of the biliary tree, the last duct before bile reaches the GI tract? (A) Common bile duct (B) Common hepatic duct (C) Cystic duct (D) Hepatic duct

(A) Common bile duct The flow of bile from the liver is as follows: Liver > common hepatic duct > cystic duct > gall bladder > cystic duct > common bile duct > GI tract

*CRB* Recall that there are both fat- and water-soluble vitamins. Where are each of them absorbed? (A) Fat soluble vitamins are absorbed as chylomicrons in the small intestine, whereas water-soluble vitamins are absorbed directly in the small intestine. (B) Fat soluble vitamins are absorbed as chylomicrons in the large intestine, whereas water-soluble vitamins are absorbed directly in the small intestine. (C) Fat soluble vitamins are absorbed as chylomicrons in the small intestine, whereas water-soluble vitamins are absorbed directly in the large intestine. (D) Fat soluble vitamins are absorbed as chylomicrons in the large intestine, whereas water-soluble vitamins are absorbed directly in the large intestine.

(A) Fat soluble vitamins are absorbed as chylomicrons in the small intestine, whereas water-soluble vitamins are absorbed directly in the small intestine.

Put the sections of the large intestine in order from first to last: I. Cecum II. Transverse Colon III. Ascending Colon IV. Sigmoid Colon V. Descending Colon (A) I > III > II > V > IV (B) I > III > V > II > IV (C) I > V > II > III > IV (D) I > IV > III > II > V

(A) I > III > II > V > IV The following are the sections of the large intestine in order from first to last: I. Cecum III. Ascending Colon II. Transverse Colon V. Descending Colon IV. Sigmoid Colon

*CRB* Which of the following is the main pigment in bile, and if it is not secreted properly, can lead to jaundice? (Hint: this is a byproduct of the breakdown of hemoglobin.) (A) Cholesterol (B) Bilirubin (C) Cholecystokinin (D) Albumin

(B) Bilirubin Bilirubin is the main pigment in bile, and if it is not secreted properly, can lead to jaundice.

What duct does bile travel through as it leaves the liver? (A) Common bile duct (B) Common hepatic duct (C) Cystic duct (D) Hepatic duct

(B) Common hepatic duct Bile travels down the common hepatic duct as it leaves the liver.

Which of the following enzymes plays an important part in the detoxification process? (A) Cytochrome P400 (B) Cytochrome P450 (C) Cytochrome P500 (D) Cytochrome P550

(B) Cytochrome P450

*CRB* There are many ways that the liver can develop Cirrhosis, including chronic alcohol consumption (from the continuous detoxifying). Which of the following is NOT a common symptom of cirrhosis. (A) Hepatocellular Carcinoma (B) Decreased resistance in the Portal Vein (Portal Hypotension) (C) A backup of fluid in the digestive system, including blood. (D) Hematemesis (vomiting blood)

(B) Decreased resistance in the Portal Vein (Portal Hypotension) Cirrhosis can actually increase resistance, causing Portal Hypertension.

*CRB* The liver has over 200 known functions, including synthesizing many important molecules. Which of the following are produced by the liver? I. Albumin II. Clotting Factors III. T-cells (A) II only (B) I and II only (C) I and III only (D) I, II and III

(B) I and II only Albumin and Clotting Factors are produced in the liver. T-cells are produced in the bone marrow.

*CRB* Where do these Pancreatic Juices pass through to enter the Duodenum? I. Major Duodenal Papillae II. Minor Duodenal Papillae III. Duodenal Duct (A) III only (B) I and II only (C) II and III only (D) I, II and III

(B) I and II only Pancreatic Juices can enter the Dudoenum through either the Major or Minor Duodenal Papillae.

Which of the following form the portal triad? I. Portal Vein II. Proper Hepatic Artery III. Hepatic Vein IV. Common Hepatic Duct (A) I, II, and III only (B) I, II, and IV only (C) II, III, and IV only (D) I, III, and IV only

(B) I, II, and IV only The portal triad is formed by the portal vein, proper hepatic artery, and the common hepatic duct.

The anus has two sphincters. The internal anal sphincter is composed of ____________ muscle. The external anal sphincter is composed of ____________ muscle. (A) smooth, smooth (B) smooth, skeletal (C) skeletal, skeletal (D) skeletal, smooth

(B) smooth, skeletal The anus has two sphincters. The internal anal sphincter is composed of smooth muscle. The external anal sphincter is composed of skeletal muscle.

What duct does bile travel through as it enters and exits the gall bladder? (A) Common bile duct (B) Common hepatic duct (C) Cystic duct (D) Hepatic duct

(C) Cystic duct Once the bile leaves the liver via the common hepatic duct, it enters the cystic duct which empties into the gall bladder. Bile also travels out this duct as it exits the gall bladder.

What is also known as "eye nerve kidney disease" due to the serious damage it can cause to these areas of the body? (A) Cystic Fibrosis (B) Arthritis (C) Diabetes (D) Lou Gehrig's Disease

(C) Diabetes Diabetes is also known as "eye nerve kidney disease" due to the serious damage it can cause to these areas of the body

Where does bile first empty into as it enters the GI tract? (A) Ileum (B) Jejunum (C) Duodenum (D) Large Intestine

(C) Duodenum Bile empties into the first part of the small intestine, the duodenum.

The large intestine is home to bacteria that assist in the digestion of fiber and other carbohydrates that the body's enzymes are unable to break down. The breakdown of these carbohydrates results in the production of gases. Which gas is responsible for the terrible smell of flatulence (farting)? (A) CH4 (B) CO2 (C) H2S (D) N2

(C) H2S Sulfur is an odorous element, and H2S is the gas that is responsible for the terrible smell of flatulence.

*CRB* Which of the following molecules are secreted in response to Gastrin, causing the acid release associated with Gastrin? (A) Ranitidine (B) Cimetidine (C) Histamine (D) Acetylcholine

(C) Histamine Histamine is secreted in response to Gastrin, and can stimulate the release of acid from Parietal Cells.

The absorption of the majority of fats that were emulsified takes place in which parts of the GI tract? I. Ileum II. Jejunum III. Duodenum (A) I only (B) II only (C) I and II only (D) II and III only

(C) I and II only The absorption of the majority of fats that were emulsified takes place in the Ileum and Jejunum at similar rates. Note that the Khan Academy video says this occurs in the Ileum. The Ileum is most known for absorbing vitamin B12 and bile acids, and whatever nutrients have yet to be absorbed.

When chyme enters the duodenum, the production of which of the following hormones is triggered? I. Ghrelin II. Secretin III. Cholecystokinen (A) I Only (B) I and III Only (C) II and III Only (D) I, II, and III

(C) II and III Only When chyme enters the duodenum, the production of secretin and cholecystokinen is triggered.

Correctly finish the sentences describing alpha and beta islet cells. __-islet cells release glucagon which ____ the blood glucose level. __-islet cells release insulin which ____ the blood glucose level. (A) alpha; increases; beta; increases (B) alpha; decreases; beta; decreases (C) alpha; increases; beta; decreases (D) alpha; decreases; beta; increases

(C) alpha; increases; beta; decreases Alpha-islet cells release glucagon which increases the blood glucose level. Beta-islet cells release insulin which decreases the blood glucose level.

What valve marks the transition between the small and large intestines? Why is it named that? (A) jejuno-cecal valve (B) jejuno-rectal valve (C) ileo-cecal valve (D) ileo-rectal valve

(C) ileo-cecal valve The ileo-cecal valve separates the small and large intestines. It is called this due to the fact that it separates the last section of the small intestines, the ileum, and the first section of the large intestines, the cecum.

Bile is needed for the absorption of fats from our food. Bile is made in the _______ and stored in the ________. (A) liver, liver (B) gall bladder, liver (C) liver, gall bladder (D) gall bladder, gall bladder

(C) liver, gall bladder Bile is made in the liver and stored in the gall bladder.

*CRB* Which hormone is produced by the gastric cells of an empty stomach to stimulate appetite? (A) Cholecystokinin (B) Angiotensin (C) Betatropin (D) Ghrelin

(D) Ghrelin Ghrelin is produced by the gastric cells of an empty stomach to stimulate appetite.

The duodenum is receiving a lot of chyme from the stomach that is being digested by gastric juice/hydrochloric acid. To neutralize all that acid, the exocrine pancreas secretes which of the following? (A) H2O (B) H2SO4- (C) Cl- (D) HCO3-

(D) HCO3- The exocrine pancreas releases bicarbonate, a base, to neutralize the gastric acid.

Which type of islet cells release somatostatin? What is the role of this hormone? (A) alpha (B) beta (C) gamma (D) delta

(D) delta Delta-islet cells release somatostatin whose job is to downregulate all other active hormones. Alpha-islet cells release glucagon, and beta-islet cells release insulin.

The digestive system is so important that it has its very own nervous system known as the ___________ nervous system, which is a branch of the _____________ nervous system. (A) gastric, motor (B) gastric, autonomic (C) enteric, motor (D) enteric, autonomic

(D) enteric, autonomic The digestive system is so important that it has its very own nervous system known as the enteric nervous system, which is a branch of the autonomic nervous system.

The large intestine's primary responsibility is to absorb: (A) nutrients (B) proteins (C) fatty acids (D) water

(D) water The large intestine's primary responsibility is to absorb water.

What effect, if any, does gastrin have on the following cells? - Parietal Cells - Mucous Cells - Gastric Cells - Chief Cells

- Parietal Cells - stimulates the secretion of HCl. - Mucous Cells - N/A - Gastric Cells - N/A - Chief Cells- stimulates the secretion of pepsinogen.

For each of the following, state whether it is acted on by secretin, cholecystokinen, or both: - Stomach - Pancreas - Gall Bladder

- Stomach - both - Pancreas - both - Gall Bladder - cholecystokinen

Describe cholecystokinen's effect on the pancreas versus the gallbladder versus the stomach.

Cholecystokinen stimulates the pancreas to release its digestive enzymes into the duodenum. It also stimulates the gall bladder to contract and release bile. Lastly, it inhibits stomach motility.

What enzyme converts trypsinogen into trypsin? What enzyme converts chymotrypsinogen into chymotrypsin.

Enteropeptidase converts trypsinogen into trypsin. Trypsin can then convert chymotrypsinogen into chymotrypsin and/or trypsinogen into trypsin.

True or False? Without your large intestines, you would most likely die due to dehydration.

False. In some cases, the large intestine needs to be completely removed. In such cases, the kidney will compensate by increasing its reabsorption of water and ions.

*CRB* True or false? The Pancreas also has δ cells that can secrete Somatostatin, which will further activate the digestive process.

False. The Pancreas also has δ cells that can secrete Somatostatin, which will inhibit the digestive process.

True or False? When food reaches your stomach, it causes the Gastrocolic reflex, which causes the food to enter the duodenum.

False. The gastrocolic reflex stimulates peristaltic movements in the large intestine, moving the food into the rectum. This is why you will often have the urge to defecate immediately after eating a meal.

Gastrin will also increase or decrease stomach motility? What does that mean?

Gastrin increases stomach motility, which increases the churning of food by the stomach.

What stimulates the secretion of gastrin? Where does gastrin exert its effects?

Gastrin is secreted in response to the presence of food in the stomach. It is produced by the G-cells of the stomach, enters the blood stream, and then acts on other cells of the stomach, promoting digestion.

*CRB* Classify each of the following cell types in the Pancreas as either being exocrine or endocrine. I. Acinar Cells II. α-Cells III. β-Cells

I. Acinar Cells - Exocrine II. α-Cells - Endocrine III. β-Cells - Endocrine

Why would it be an issue if both the internal and external anal sphincter were composed of smooth muscle?

If both anal sphincters were composed of smooth muscle, we would not be able to control the timing of our bowel movements. We'd be wearing diapers our entire lives! :P

Why would it be a serious problem if trypsinogen was converted into trypsin while it was still in the pancreas?

If trypsinogen was converted into trypsin while it was still in the pancreas, it would activate all the other trypsinogen and chymotrypsinogen enzymes before reaching the duodenum, and they would begin digesting the pancreas and the surrounding tissues!

Compare what is malfunctioning in people with type I versus type II diabetes.

No insulin is produced in people with type I diabetes. Normal insulin is produced but the insulin receptors are broken in people with type II diabetes.

*CRB* The Gall bladder is known to store and concentrate bile. Explain why Stone formation is more common in the Gall Bladder than the Liver, using Ksp.

Recall that Ksp refers to how soluble partially-soluble salts are in a solution, and at a concentration above Ksp, that salt will precipitate out. Because the Gall bladder is concentrating the bile, it can reach concentrations above Ksp, which will trigger precipitation/stone formation. That concentration does not occur in the liver, so it is not an issue there.

Describe secretin's effect on the pancreas versus the stomach.

Secretin stimulates the pancreas to release bicarbonate (HCO3-), a base, into the duodenum, increasing the pH of the chyme that recently entered. Secretin also inhibits the actions of gastrin (HCl release, pepsinogen release, and increase in stomach motility).

What is it in the chyme that triggers the secretion of secretin? What is it in the chyme that triggers the secretion of cholecystokinen?

Secretion of secretin is triggered by the presence of H+ in the chyme. Secretion of cholecystokinen is triggered by the presence of fats in the chyme.

A patient takes medicine X orally, but it has no effect. The doctor believes that this is all the liver's fault. Why do you suppose the liver might be the culprit in this case?

The liver is responsible for detoxifying substances (whether they are illicit drugs or medicine). Before nutrients and macromolecules get transported throughout the body, they are first transported to the liver.

Compare the main role of the exocrine pancreas versus the endocrine pancreas.

The main function of the exocrine pancreas is to secrete salts and enzymes into the duodenum to assist with digestion. The main function of the endocrine pancreas is to secrete hormones into the bloodstream that regulate blood sugar levels.

What is the primary role of secretin versus cholecystokinen?

The primary role of secretin is to increase the pH of the chyme as it enters the duodenum. The primary role of cholecystokinen is to promote digestion in the duodenum.

What is the role of the rectum versus the anus?

The purpose of the rectum is to strore stool until we have time to use the toilet. The purpose of the anus is to expel the stool into the toilet.

*CRB* True or false? The Acinar Cells in the pancreas make up the majority of the pancreas, and produce the Pancreatic Juices.

True. The Acinar Cells in the pancreas make up the majority of the pancreas, and produce the Pancreatic Juices.

True or False? The Enteric Nervous System does not have to send neuronal information to the spinal cord or brain to control the GI tract. It can operate independently.

True. The Enteric Nervous System does not have to send neuronal information to the spinal cord or brain to control the GI tract. It can operate independently.

*CRB* True or false? Water can be absorbed both Transcellularly (moving through the cell) and Paracellularly (squeezing between cells) in the intestines.

True. Water can be absorbed both Transcellularly (moving through the cell) and Paracellularly (squeezing between cells) in the intestines.