Digestive System

Question 1

Who releases Gastrin?

Answer 1

Gastrin is released by G cells in the stomach.

Question 2

Who releases leptin?

Answer 2

Leptin is secreted by adipocytes, or fat cells.

Question 3

Who releases Cholecystokinin?

Answer 3

Cholecystokinin is secreted by cells in the duodenum. It stimulates the pancreatic release of digestive enzymes and the release of bile from the gallbladder.

Question 4

Who releases secretin?

Answer 4

S cells in the duodenum release secretin, which acts on the pancreas to stimulate release of bicarbonate.

Question 5

What does secretin do?

Answer 5

Acts on the pancreas to stimulate release of bicarbonate.

Question 6

True or False: Digestion takes place only in the stomach

Answer 6

False, it can also take place in the small intestine

Question 7

True or false: Carbohydrate digestion takes place in the mouth, stomach, and small intestine.

Answer 7

This statement is false. Carbohydrates are digested in the mouth and small intestine only. Of the three main macronutrients (carbohydrates, proteins, and lipids), only proteins are digested in the stomach. Carbohydrate digestion begins in the oral cavity, where salivary amylase hydrolyzes starches into smaller components called oligosaccharides and disaccharides. Once these molecules make their way into the small intestine, they are further broken down into monosaccharides by pancreatic enzymes and brush border disaccharidases. Once in their simplest form, they can be absorbed by enterocytes.

Question 8

True or False: only proteins are digested in the stomach

Answer 8

TRUUUUUE

Question 9

Pepsinogen

Answer 9

Pepsinogen is a zymogen, or inactive enzyme, produced by specialized cells in the stomach. Stomach acid converts pepsinogen into pepsin, its active form. Pepsin functions in protein digestion. RECALL: protein digestion occurs in the STOMACH so it would make sense that pepsin is in the STOMACH!!

Question 10

Where are brush border peptidases produced?

Answer 10

brush border enzymes like peptidases and disaccharidases are produced by enterocytes in the small intestine.

Question 11

True or False: The colorectal sphincter is located between the colon and rectum

Answer 11

The colorectal sphincter is not one of the sphincters present in the digestive system. The name implies that it would be located between the colon and the rectum of the large bowel, but there is actually no sphincter in that anatomical region.

Question 12

True/false: The duodenum is a highly acidic environment that receives chyme from the stomach via the pyloric sphincter.

Answer 12

This statement is false. The duodenum, which is the first section of the small intestine, is maintained at a near-neutral pH of 6-7. Although chyme entering the duodenum from the stomach is extremely acidic, the pancreas secretes bicarbonate to neutralize it. This ensures that pancreatic digestive enzymes can operate at maximum efficiency in the duodenum.

Question 13

Sphincter at base of esophagus

Answer 13

Lower esophageal sphincter/ gastrointestinal sphincter/ cardiac sphincter

Question 14

Sphincter at base of stomach

Answer 14

pyloric sphincter

Question 15

Describe how glucose is taken in by enterocytes

Answer 15

Enterocytes in the small intestine take up monosaccharides like glucose from the lumen through secondary active transport. This transport mechanism is a two-step process. First, a sodium-potassium ATPase generates a sodium gradient across the enterocyte’s membrane. This gradient powers the transport of glucose across the cell membrane through a sodium-glucose symporter. Galactose, which is another monosaccharide, is also taken up through secondary active transport. Other monosaccharides like fructose enter enterocytes via facilitated diffusion.

Question 16

True or False: Fatty acids enter the enterocyte via secondary active transport

Answer 16

False: Because fatty acids are hydrophobic, they enter enterocytes by passively diffusing through the cell membrane. This transport process is much simpler than secondary active transport and does not require energy.

Question 17

True or False: Both glucose and amino acids enter enterocytes via secondary active transport

Answer 17

true

Question 18

Place the following in the order in which they would act on carbs entering the body:
Pancreatic amylase
Salivary Amylase
disaccharidase

Answer 18

The correct order is salivary amylase, followed by pancreatic amylase, and then disaccharidase. Salivary amylase breaks down starches (polysaccharides) in the mouth, producing oligosaccharides and disaccharides. The pancreas releases pancreatic amylase into the duodenum, which breaks down oligosaccharides into disaccharides. Disaccharidases on the brush border of the small intestine cleave these disaccharides to produce monosaccharides like glucose, which are small enough to be taken up by intestinal epithelial cells.

Question 19

Where are disaccharidases produced/used?

Answer 19

Brush border of small intestine

Question 20

True or False: AA, Lipids, and carbs are absorbed by the stomach

Answer 20

False

Question 21

What differentiates essential vitamins from minerals?

Answer 21

Vitamins function as coenzymes in physiological processes. Coenzymes are a special type of cofactor with a complex organic structure. Because minerals are metal ions, they are not coenzymes.

Question 22

Bile

Answer 22

Bile is a mixture of bile salts, pigments, and cholesterol that helps emulsify, or dissolve, dietary fats. Amphipathic bile salts associate with lipids to break up larger fat globules into small micelles that mainly consist of triglycerides. This increases the surface area for chemical digestion of these triglycerides.

Question 23

True or false: Protein digestion is limited to the stomach and small intestine.

Answer 23

This statement is true. Protein digestion begins in the stomach, where pepsin cleaves large proteins into peptides. These peptides are further digested into smaller peptides and individual amino acids by pancreatic enzymes and brush border peptidases in the small intestine.

Question 24

Describe the process of digestion and absorption of fats?

Answer 24

Lipid digestion begins in the mouth, where lingual lipase hydrolyzes small amounts of triglycerides. Once lipids reach the duodenum, the pancreas releases bile. Bile emulsifies larger fat globules, generating small micelles. These micelles have more surface area available for pancreatic lipases, which hydrolyze triglycerides into fatty acids and monoglycerides. Micelles can diffuse easily through enterocyte membranes. Once inside cells, they are packed into chylomicrons, which are lipoproteins that transport dietary lipids to other parts of the body. Chylomicrons enter circulation through lacteals, which are small vessels that connect to the lymphatic system.

Question 25

Laxatives speed up the movement of chyme through the large intestine. The large intestine’s primary function is to reabsorb water from the chyme, concentrating it to form feces. If laxatives speed up the movement of chyme through the large intestine, most of this water will be excreted rather than reabsorbed. This would explain why patients see temporary weight loss after laxative abuse.

Answer 25

How do laxatives work?

Question 26

What branch of the nervous system is the enteric nervous system a part of?

Answer 26

Its part of the autonomic ns

Question 27

true or false: the enteric NS is subject to sym and parsympathetic innervation

Answer 27

TRUE: Because the enteric nervous system is part of the autonomic nervous system, it responds to both sympathetic and parasympathetic input. “Fight or flight” scenarios activate the sympathetic nervous system, which constricts blood vessels supplying the GI tract. This diverts blood flow away from digestion into peripheral tissues like skeletal muscle which need it more during periods of stress.

Question 28

True or false: Enteropeptidase is a zymogen released by the pancreas that converts trypsinogen into trypsin.

Answer 28

This statement is false. Enteropeptidase is a fully functional enzyme, not a zymogen. Zymogens are inactive enzymes that must be activated by another enzyme before they become functional. Other than this detail, the rest of the statement is correct.

Question 29

True or False: digestion of carbs and fats begin in the oral cavity

Answer 29

TRUE: Salivary amylase breaks down starches (a type of carbohydrate) into smaller glucose units called oligosaccharides and disaccharides. This enzyme is found in saliva, which is produced by glands in the mouth.
Lingual lipase catalyzes the first steps in fat digestion. Similarly to salivary amylase, lingual lipase is found in saliva.

Question 30

True or false: Food moves from the mouth into the stomach by peristalsis, which refers to the wave-like contractions of skeletal muscle lining the entire length of the esophagus.

Answer 30

This statement is false. Although food certainly does move through the esophagus via peristalsis, the majority of the esophagus is lined with smooth muscle rather than skeletal muscle. The distinction between smooth and skeletal muscle is important because smooth muscle is not under voluntary control. Once you swallow something, the smooth muscle cells lining your esophagus will automatically move it into the stomach without any conscious effort from you.

Question 31

What is the stomachs role in vitamin b12 absorption?

Answer 31

In addition to pepsin, the stomach produces intrinsic factor, which facilitates vitamin B12 absorption.

Question 32

What do I secrete: chief cells

Answer 32

Chief cells secrete pepsinogen, which is the inactive precursor of pepsin. Pepsin is an enzyme that breaks down proteins in the stomach.

Question 33

What do I secrete: parietal cells

Answer 33

Parietal cells secrete gastric acid, which is a solution composed of HCl and salts.

Question 34

What do i secrete: mucous epithelial cells

Answer 34

Mucous epithelial cells, which are a special type of epithelial cell, secrete bicarbonate-rich mucus that coats the stomach. This mucus neutralizes stomach acid to prevent it from degrading the stomach lining.

Question 35

Helicobacter pylori is a bacterium that has evolved to thrive in the harsh acidic environment of the human stomach. H. pylori infections are asymptomatic in 80% of cases, but can sometimes cause serious conditions like gastritis, gastric ulcers, and stomach cancer. What makes this microorganism so dangerous?

Answer 35

H. pylori can burrow under the protective mucous layer that coats the stomach lining to reach endothelial cells. Once there, these bacteria can irritate stomach tissue, giving rise to a variety of gastric disorders.

Question 36

True or False: the stomach absorbs at least one of the key macronutrients (proteins, carbohydrates, fats, and nucleic acids)

Answer 36

This statement is false. The stomach produces gastric acid and several key enzymes involved in nutrient digestion, but it does not directly absorb any of the major macronutrients (proteins, carbohydrates, fats, and nucleic acids).

Question 37

What role in immunity does the digestive tract play?

Answer 37

Saliva contains lysozyme, which catalyzes the destruction of bacterial cell walls.The stomach typically has a pH in the range of 1.5 to 3, which kills many microorganisms on contact. One notable exception is H. pylori, which has evolved to survive in this acidic environment. However, the question says “many pathogens,” not “ALL pathogens”.

Question 38

How does the small intestine have the surface area of a tennis court?

Answer 38

Enterocytes are the epithelial cells that make up the small intestine. Because villi are tiny folds of the small intestine’s epithelial surface, each villus is composed of hundreds of enterocytes. Microvilli are microscopic hair-like extensions of each enterocyte’s cell membrane.

Question 39

What path does chyme take when exiting the stomach?

Answer 39

The correct order is the duodenum, followed by the jejunum, followed by the ileum. Chyme enters the duodenum from the stomach via the pyloric sphincter, triggering the release of digestive enzymes. From there, it heads into the jejunum, which is the longest section of the small intestine and the major site of nutrient absorption. Lastly, the bolus encounters the ileum, which drops it into the cecum of the large intestine through the ileocecal valve.

Question 40

True or False: enterocytes absorb disacharides

Answer 40

False. Enterocytes secrete enzymes called disaccharidases that cleave disaccharides, generating monosaccharides, which are much easier to absorb.

Question 41

Which of the following do enterocytes absorb? 
Monosaccharides
Disaccharides 
Amino Acids
Proteins
Fatty Acids

Answer 41

Monosaccahrides, Amino acids, fatty acids

Question 42

What does CKK do?

Answer 42

Cholecystokinin (CKK) is a hormone that acts on the duodenum. It has several different roles, one of which is to stimulate the release of bile from the gallbladder. CKK tells the pancreas to release digestive enzymes, including pancreatic amylase, pancreatic lipase, and proteases, which break down large macromolecules in chyme entering the duodenum.
Summary:
-stimulates bile release
-Stimulates pancreatic release of amylase, lipase, and protease

Question 43

What does secretin do?

Answer 43

Secretin is a hormone that acts in the duodenum. It stimulates the release of bicarbonate from the pancreas.

Question 44

True or false: feces forming in the large intestine mainly consists of water, toxins, and excess nutrients

Answer 44

Feces are largely composed of water, metabolic waste products, and indigestible material, which is mostly cellulose or dietary fiber. Excess nutrients are rarely excreted. The body absorbs all the nutrients it can get from a meal, storing anything it doesn’t immediately need as glycogen and fat.

Question 45

True or false: Bile salts are amphipathic molecules that associate with lipids in the aqueous environment of the duodenum. By preventing the exposure of lipid surface area, they facilitate the action of water-soluble lipases.

Answer 45

This statement is false. While the first sentence is correct, the second sentence is not. Bile salts actually generate more lipid surface area through a process called emulsification. This makes fat globules more accessible to water-soluble lipases, which chemically digest lipids.

Question 46

True or False: liver can take over bile storage when the gallbladder is not functioning properly or in cases where the gallbladder has been surgically removed.

Answer 46

Bile is normally stored by the gallbladder. However, the liver can take over bile storage when the gallbladder is not functioning properly or in cases where the gallbladder has been surgically removed.

Question 47

Pancreatic enzymes function optimally in a pH range of…

Answer 47

6-7. Pancreatic enzymes, including pancreatic amylase, lipase, and proteases operate best in a neutral pH range. Recall that the pancreas releases bicarbonate ions into the duodenum to neutralize chyme, which is initially very acidic (pH 1.5-3.5) because it contains lots of gastric acid produced in the stomach. Once the bicarbonate influx elevates the pH into the 6-7 range, pancreatic enzymes are released to break down larger macromolecules.

Question 48

Somatostatin

Answer 48

Somatostatin is the main hormone that inhibits digestion. Since gastrin, CCK, and secretin all promote digestive processes, it should make sense that somatostatin inhibits their release.
Somatostatin blocks stomach emptying into the duodenum, which is an important transitory process in digestion.
Somatostatin prevents the secretion of insulin and glucagon, which promote digestive processes associated with satiety and hunger.

Question 49

True or False: somatostatin prevents the secretion of insulin and glucagon

Answer 49

TRUE. Somatostatin prevents the secretion of insulin and glucagon, which promote digestive processes associated with satiety and hunger.

Question 50

True or False: somatostatin blocks stomach emptying

Answer 50

Somatostatin blocks stomach emptying into the duodenum, which is an important transitory process in digestion.

Question 51

What secretes gastrin?

Answer 51

STOMACH:
G cells of the stomach secrete gastrin, which tells parietal cells to secrete gastric acid. This allows stomach acid levels to be moderated so they do not remain unnecessarily high when there is no food in the stomach.

Question 52

What secretes secretin?

Answer 52

SMALL INTESTINE:

S cells in the duodenum of the small intestine release secretin, which stimulates bicarbonate release from the pancreas.

Question 53

What secretes CCK?

Answer 53

SMALL INTESTINE:

CCK is produced in the small (not the large) intestine and stimulates the release of pancreatic enzymes and bile.

Question 54

What secretes ghrelin?

Answer 54

SMALL INTESTINE AND PANCREAS:

Ghrelin is released from specialized cells in the upper stomach and pancreas when the stomach is empty.

Question 55

What secretes leptin?

Answer 55

ADIPOCYTES:

Leptin is synthesized in adipocytes to promote satiety after a meal.

Question 56

Which hormone promotes pancreatic release of bicarbonate into the duodenum of the small intestine?

Answer 56

Secretin

Question 57

Fatty acids absorbed by enterocytes enter circulation after being packaged into…

Answer 57

Chylomicrons

Question 58

lipoproteins particles made of triglycerides, phospholipids, cholesterol, and proteins. They are synthesized in enterocytes and diffuse into lacteals, which empty into venous circulation. Once in the bloodstream, they can deliver the dietary lipids they carry to cells throughout the body.

Answer 58

Chylomicrons

Question 59

True/false: Dietary fatty acids enter the bloodstream immediately after absorption in the small intestine.

Answer 59

This statement is false. Fatty acids do not immediately enter circulation after absorption. After they are absorbed by enterocytes, they are packaged into chylomicrons and shunted into lacteals. Lacteals are small lymphatic vessels that drain into larger lymphatic vessels, which eventually empty into the bloodstream.

Question 60

True or False: Triglycerides diffuse passively into enterocytes

Answer 60

False: Triglycerides must be cleaved into fatty acids and glycerol before they can be taken up by enterocytes.

Question 61

What are the lipid soluble vitamins?

Answer 61

ADEK

Question 62

What are the water soluble vitamins?

Answer 62

BC

Question 63

This vitamin is essential for vision

Answer 63

Vitamin A facilitates vision. It interacts with opsin to form a protein called rhodopsin, which is present in the rods of the retina and is used for low-light vision.

Question 64

This vitamin is essential for the synthesis of collagen

Answer 64

Vitamin C is essential for the proper synthesis of collagen, an important structural protein used in connective tissues. A deficiency in vitamin C gives rise to scurvy.

Question 65

This vitamin is essential for the absoprtion of magnesium, calcium, and phosphate

Answer 65

Vitamin D increases intestinal absorption of magnesium, calcium, and phosphate when the body needs more of these minerals. It also ensures that levels of calcium and phosphate in the bloodstream do not get too high or too low.

Question 66

This vitamin is essential for blood coagulation

Answer 66

vitamin K completes the synthesis of various proteins involved in the blood coagulation cascade. In the absence of vitamin K, uncontrolled bleeding can occur.

Question 67

True or false: vitamin C often travels in the body bound to a protein

Answer 67

False; Because vitamin C is water-soluble, it can travel unprotected in the bloodstream. Plasma proteins are required for the vascular transport of nonpolar molecules.

Question 68

Which hormones play a role in appetite?

Answer 68

Ghrelin, Leptin, CCK.
Cholecystokinin functions in both digestion and appetite maintenance. High levels of cholecystokinin inhibit appetite after a meal. As a digestive hormone, it stimulates the secretion of digestive enzymes from the pancreas and bile from the gallbladder.

Question 69

True or False: secretin stimulates bile release

Answer 69

False: Cholecystokinin, not secretin, stimulates the release of bile.

Question 70

Which of the essential vitamins can be eliminated through the urinary system?

Answer 70

B and C

Question 71

Gut flora refers to the complex community of microorganisms that reside in the gastrointestinal tracts of many animal species. Emerging research suggests that the exact composition of this microbiome is essential to your health. Bacterial imbalances, overgrowths, and deficits can give rise to a variety of metabolic, gastrointestinal, and even psychiatric disorders. Which digestive organ hosts the largest community of bacteria in the human body?

Answer 71

Large Intestine:
The large intestine is colonized by an incredible diversity of microorganisms, including bacteria. Somewhere between 300 and 1000 different species of bacteria reside here. Some of these bacteria are pathogenic, but the vast majority are either harmless or helpful. For example, certain key species synthesize essential vitamins that are absorbed directly in the large intestine.

Question 72

What tissue type is the small intestine made of?

Answer 72

Smmothe muscle

Question 73

True or False: The appendix is continuous with the colon

Answer 73

True,
In appendicitis: The appendix is continuous with the colon so that bacteria can move between these two structures; a ruptured appendix would allow E. coli into the abdominal cavity, which is not normal.