Secretions of the intestine, liver, gall bladder and pancreas

Question 1

What is the primary function of the Small Intestine?

Answer 1

The Small Intestine governs the majority of chemical digestion and absorption of nutrients, electrolytes, and water.

Question 2

What are the primary secretions in the Small Intestine?

Answer 2

The primary secretions in the Small Intestine are intestinal juice (mucus/HCO3-), pancreatic juice (digestive enzymes), and bile (bile salts).

Question 3

Which key endocrine hormones are involved in regulating bile and pancreatic secretions in the Small Intestine?

Answer 3

The key endocrine hormones involved in regulating bile and pancreatic secretions in the Small Intestine are secretin, cholecystokinin (CCK), and glucose-dependent insulinotropic peptide (GIP).

Question 4

What is GIP?

Answer 4

GIP, also known as gastric inhibitory peptide, is an endocrine hormone that regulates bile and pancreatic secretions in the Small Intestine.

Question 5

What is the primary role of the Small Intestine?

Answer 5

The Small Intestine governs the majority of chemical digestion and absorption of nutrients, electrolytes, and water.

Question 6

What are the primary secretions in the Small Intestine?

Answer 6

The primary secretions in the Small Intestine include intestinal juice (mucus/HCO3-), pancreatic juice (digestive enzymes), and bile (bile salts).

Question 7

Which hormones regulate bile and pancreatic secretions in the Small Intestine?

Answer 7

The key endocrine hormones secretin, cholecystokinin (CCK), and glucose-dependent insulinotropic peptide (GIP) regulate bile and pancreatic secretions in the Small Intestine.

Question 8

What is the full name of GIP, and what is its function?

Answer 8

GIP, also known as gastric inhibitory peptide, is an endocrine hormone that regulates bile and pancreatic secretions in the Small Intestine.

Question 9

What is the renewal rate of epithelial cells through stem cell renewal?

Answer 9

Epithelial cells have a rapid regeneration rate of approximately 3-6 days through stem cell renewal.

Question 10

Why are epithelial cells vulnerable to radiation and chemotherapy?

Answer 10

The rapid regeneration rate of epithelial cells makes them vulnerable to radiation and chemotherapy treatments.

Question 11

What are the components of intestinal juice in the Small Intestine?

Answer 11

Intestinal juice in the Small Intestine contains electrolytes and water (secretory enterocytes), lysozyme (Paneth cells), mucus (goblet cells), and alkaline mucus-containing fluid (submucosal duodenal Brunner’s glands).

Question 12

Which key endocrine hormones are secreted into the vasculature by specific cells in the Small Intestine?

Answer 12

CCK (I cells) stimulates pancreatic and gallbladder secretion, secretin (S cells) stimulates pancreatic and biliary bicarbonate secretion, and Gastric Inhibitory Polypeptide (GIP) (K cells) may inhibit acid secretion and stimulate insulin release.

Question 13

What is the primary function of bile in the Small Intestine?

Answer 13

Bile in the Small Intestine contains bile salts that aid in the emulsification (mixing) of lipids.

Question 14

What are the components of exocrine pancreatic juice in the Small Intestine?

Answer 14

Exocrine pancreatic juice in the Small Intestine contains bicarbonate and digestive enzymes.

Question 15

How is the pancreas regulated?

Answer 15

The pancreas is regulated by both hormonal and neural mechanisms, including the subdivision of cranial nerve X (vagus).

Question 16

What does the exocrine pancreas secrete?

Answer 16

The exocrine pancreas secretes pancreatic juice, which contains a bicarbonate-rich secretion with a pH of approximately 8, and digestive enzymes essential for normal digestion and absorption.

Question 17

What is the name of the sphincter that controls the flow of pancreatic secretions into the small intestine?

Answer 17

The hepatopancreatic sphincter regulates the release of pancreatic secretions into the small intestine.

Question 18

What is the composition of the pancreas?

Answer 18

The pancreas consists of glandular epithelial clusters.

Question 19

What percentage of the pancreas is composed of exocrine acinar clusters, and what do they secrete?

Answer 19

Approximately 99% of the pancreas is composed of exocrine acinar clusters that secrete pancreatic juice, which contains water, electrolytes, sodium bicarbonate, and pro-enzymes.

Question 20

What percentage of the pancreas is composed of endocrine pancreatic islets, and what are the types of secreting cells found in them?

Answer 20

Approximately 1% of the pancreas is composed of endocrine pancreatic islets, also known as Islets of Langerhans. They contain four types of secreting cells: alpha cells (secreting glucagon), beta cells (secreting insulin), delta cells (secreting somatostatin), and F cells or pancreatic polypeptide cells (secreting pancreatic polypeptide).

Question 21

What are the components of pancreatic acinar and ductular secretions?

Answer 21

Pancreatic acinar and ductular secretions contain enzymes, NaCl, fluid, NaHCO3, and fluid.

Question 22

How is the production of acinar enzymes regulated?

Answer 22

Acinar enzyme production is regulated by acetylcholine, which is released via parasympathetic cranial nerve X (vagus) stimulation.

Question 23

What triggers the release of CCK (pancreozymin), and what is its effect on pancreatic secretion?

Answer 23

CCK is triggered by chyme containing fat and protein products. It stimulates the production of lower volume, enzyme-rich pancreatic juice.

Question 24

How is the production of ductal bicarbonate and water regulated?

Answer 24

The production of ductal bicarbonate and water is regulated by secretin, which is triggered by the presence of high levels of H+ in acidic chyme. It stimulates the production of plentiful, HCO3- rich, low enzyme pancreatic juice.

Question 25

What is the function of pancreatic proteolytic enzymes?

Answer 25

: Pancreatic proteolytic enzymes are responsible for converting proteins into peptides.

Question 26

What is the function of amylase in pancreatic secretion?

Answer 26

Amylase hydrolyzes starch, glycogen, and other carbohydrates to form di- and trisaccharides.

Question 27

What is the role of lipases in pancreatic secretion?

Answer 27

Lipases hydrolyze fats into fatty acids and monoglycerides.

Question 28

What is the function of nucleases in pancreatic secretion?

Answer 28

Nucleases digest RNA and DNA to nucleic acids.

Question 29

: What is the role of trypsin inhibitor in pancreatic secretion?

Answer 29

Trypsin inhibitor prevents the activation of trypsin, which helps prevent excessive pancreatic digestion.

Question 30

In what form are proteolytic enzymes produced in the pancreas?

Answer 30

Proteolytic enzymes are produced as inactive precursors called zymogens.

Question 31

What enzyme in the small intestine activates trypsinogen to form active trypsin?

Answer 31

Small intestinal brush border enterokinase cleaves a hexapeptide to convert trypsinogen into its active form, trypsin.

Question 32

What is the role of trypsin in the activation of other proteolytic enzymes?

Answer 32

Trypsin cleaves and activates other proteolytic enzymes in the digestive process.

Question 33

What is the purpose of preventing autodigestion in the pancreas?

Answer 33

Preventing autodigestion, which is the process of pancreatic enzymes destroying its own tissues, helps to avoid an inflammatory response.

Question 34

What stimulates the secretion of high-volume, bicarbonate-rich pancreatic juice from the ducts?

Answer 34

Secretin stimulates the secretion of high-volume, bicarbonate-rich pancreatic juice from the ducts.

Question 35

How is bicarbonate (HCO3−) secreted into the duct lumen?

Answer 35

Bicarbonate (HCO3−) secretion out of the cell into the duct lumen occurs via Cl−/HCO3− exchange at the apical cell membrane.

Question 36

How is Cl− recycled out of the cell in duct secretion?

Answer 36

Cl− is recycled out of the cell via the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel under the stimulation of secretin, mediated by cAMP.

Question 37

How is Na+ secreted into the duct lumen in duct secretion?

Answer 37

Na+ is secreted transcellularly into the duct lumen following HCO3− secretion, driven by an electrochemical gradient. Water follows by osmosis.

Question 38

What are the regulatory factors that control pancreatic juice secretion?

Answer 38

Pancreatic juice secretion is regulated by ACh (vago-vagal gastro-pancreatic reflex), gastrin, secretin, cholecystokinin (also known as pancreozymin), and VIP (vasoactive intestinal peptide).

Question 39

What is the dysfunction associated with the CFTR Cl− channel in the pancreatic ducts?

Answer 39

Patients with cystic fibrosis lack a functional CFTR Cl− channel in the luminal membrane, which leads to defective ductal fluid secretion.

Question 40

What are the consequences of CFTR Cl− channel dysfunction in the pancreas?

Answer 40

The blocked CFTR Cl− channel results in the accumulation of precipitated enzymes and mucus, leading to blocked ducts and pancreatic fibrosis. This impairs the secretion of necessary pancreatic enzymes for digestion and results in malabsorption.

Question 41

How is malabsorption in cystic fibrosis treated?

Answer 41

The treatment for malabsorption in cystic fibrosis involves oral pancreatic enzyme supplements that are taken with each meal to provide the necessary enzymes for digestion.

Question 42

What is pancreatitis?

Answer 42

Pancreatitis is an inflammatory disease characterized by the activation of pancreatic enzymes within the pancreas and surrounding tissues, leading to autodigestion of the tissues.

Question 43

What are the most common causes of pancreatitis?

Answer 43

The most common causes of pancreatitis include gallstones and alcohol abuse/misuse/dependence. These conditions can lead to the obstruction of the pancreatic duct.

Question 44

How does obstruction of the pancreatic duct contribute to pancreatitis?

Answer 44

Obstruction of the pancreatic duct can lead to the accumulation and activation of pancreatic enzymes within the pancreas, causing inflammation and tissue damage.

Question 45

What is the role of bile in digestion?

Answer 45

Bile plays a key role in the digestion and absorption of fats from the small intestine.

Question 46

How do bile salts contribute to fat digestion?

Answer 46

Bile salts emulsify fats, breaking them down into smaller droplets, which enhances their digestion by pancreatic lipase. Bile salts also solubilize fat digestion products into aggregations called micelles, which aid in their absorption across the mucosa.

Question 47

What waste products are eliminated through bile?

Answer 47

Bile eliminates waste products such as bile pigment bilirubin, which is a breakdown product of haem in red blood cell degradation. The breakdown product stercobilin gives feces its brown color.

Question 48

What other substances are eliminated through bile?

Answer 48

Bile also eliminates cholesterol and certain drugs from the body.

Question 49

Where is bile synthesized in the liver?

Answer 49

Bile is constantly synthesized by hepatocytes, which are the functional cells lining the sinusoidal blood vessels in the liver acinus.

Question 50

What is the primary cell type responsible for bile synthesis?

Answer 50

Hepatocytes are the key functional cells of the liver and are responsible for forming approximately 80% of the liver mass.

Question 51

How does bile drain within the liver?

Answer 51

Bile drains into blind-ended canaliculi, which are small bile ductules formed by the hepatocytes. From there, it flows into the left and right hepatic bile ducts within the liver.

Question 52

Where is bile stored?

Answer 52

Bile is stored in the gall bladder.

Question 53

What triggers the release of CCK?

Answer 53

CCK is released in response to the fat content of the duodenum.

Question 54

: What are the effects of CCK on bile secretion and regulation?

Answer 54

CCK stimulates gall bladder contraction and relaxes the sphincter of the hepatopancreatic ampulla (also known as the Sphincter of Oddi), facilitating the release of bile into the duodenum.

Question 55

What triggers the release of secretin?

Answer 55

Secretin is released in response to acidic chyme in the duodenum.

Question 56

What is the role of secretin in bile secretion?

Answer 56

Secretin stimulates the liver to secrete bicarbonate (HCO3−) and water into the bile, helping to neutralize the acidic chyme.

Question 57

What is the role of vagal stimulation in bile flow?

Answer 57

Vagal stimulation plays a minor role in bile flow regulation.

Question 58

What are the effects of gall bladder contraction on bile flow?

Answer 58

Gall bladder contraction promotes the release of stored bile into the common bile duct, facilitating its flow into the duodenum.

Question 59

What is the enterohepatic circulation of bile salts?

Answer 59

Bile salts are continuously recycled through active reabsorption within the ileum. Approximately 94% of bile salts return to the liver via the portal vein to drive bile synthesis.

Question 60

: How does enterohepatic circulation affect the elimination of hydrophobic drugs?

Answer 60

Many hydrophobic drugs are deactivated by the liver and excreted into bile. Enterohepatic recycling occurs, where the drugs are reabsorbed in the intestine, slowing down the rate of drug elimination.

Question 61

What are the different forms of gall bladder disease?

Answer 61

Gall bladder disease can manifest in several forms, ranging from asymptomatic cholelithiasis (gallstones) to biliary colic (blockage of the cystic duct). These disorders can affect different areas of the biliary tract.

Question 62

What are the common causes of gallstones?

Answer 62

Gallstones are commonly caused by excessive water and bile salt reabsorption from bile (leading to supersaturation of bile), excessive cholesterol in bile causing precipitation (often associated with a high-fat diet), and inflammation of the epithelium (low-grade chronic infection).