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PHGY 216 Mod 6 > Section 4 > Flashcards

Section 4 Flashcards

1
Q

What are pancreatic secretions and biliary secretions, and why are they essential for digestion?

A

Pancreatic Secretions: These are secretions from the pancreas, including enzymes and bicarbonate, crucial for digestion. Enzymes aid in breaking down carbohydrates, proteins, and fats, while bicarbonate helps neutralize the acidic chyme from the stomach.

Biliary Secretions: Biliary secretions encompass secretions from the liver, gallbladder, and associated ducts. They mainly consist of bile, which emulsifies fats, aiding in their digestion and absorption.

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2
Q

What is the major physiological role of the pancreas besides its endocrine functions (insulin and glucagon), and what is the composition of pancreatic juice?

A

The pancreas secretes pancreatic juice, a mixture of pancreatic enzymes and an aqueous alkaline secretion.

Pancreatic enzymes are vital for digestion and can almost completely digest food even in the absence of gastric secretions.

The aqueous alkaline secretion, rich in NaHCO3, neutralizes the acidic chyme from the stomach, creating a neutral or slightly alkaline environment ideal for the function of pancreatic enzymes.

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3
Q

What are the three main types of pancreatic enzymes secreted by pancreatic acinar cells?

A

Proteolytic enzymes
Pancreatic amylase
Pancreatic lipase

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4
Q

How are proteolytic enzymes activated in the pancreas?

A

Proteolytic enzymes, including trypsinogen, chymotrypsinogen, and procarboxypeptidase, are activated as follows:

  • Trypsinogen is converted to active trypsin by enterokinase in the duodenal mucosa.
  • Chymotripsinogen is converted to chymotrypsin by trypsin.
  • Procarboxypeptidase is converted to carboxypeptidase, also by trypsin.
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4
Q

What is the function of pancreatic amylase?

A

Pancreatic amylase converts polysaccharides into maltose, functioning similarly to salivary amylase in carbohydrate digestion.

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5
Q

What is the role of pancreatic lipase?

A

Pancreatic lipase is the only enzyme capable of digesting fats. It breaks down triglycerides into monoglycerides and free fatty acids, facilitating fat absorption in the small intestine.

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6
Q

What triggers the release of secretin and cholecystokinin (CCK) in the duodenum?

A

The presence of chyme in the duodenum triggers the release of secretin and CCK.

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7
Q

What is the role of secretin in pancreatic exocrine secretion?

A

Secretin stimulates the duct cells of the pancreas to increase their secretion of a sodium bicarbonate (NaHCO3)-rich fluid, which helps neutralize the acidic chyme entering the duodenum.

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8
Q

How does cholecystokinin (CCK) affect pancreatic exocrine secretion? What is it stimulated by?

A

CCK, primarily stimulated by the presence of fats in the duodenum (and to a lesser extent by protein), stimulates pancreatic acinar cells to increase their secretion of digestive enzymes.

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9
Q

Which types of nutrients stimulate the release of cholecystokinin (CCK) from the duodenal mucosa?

A

Cholecystokinin (CCK) is primarily released in response to the presence of fats in the duodenum, and to a lesser extent, protein. Carbohydrates do not stimulate the release of CCK.

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10
Q

The amount of secretin release is proportional to the amount of ___________ that enters teh duodenum

A

acid

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11
Q

A proteolytic enzyme converted to its active form by enterokinase

A

Trypsinogen

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12
Q

It converts polysaccharides into the disaccharide maltose

A

Pancreatic Amylase

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13
Q

It hydrolyzes triglycerides into monoglycerides and free fatty acids

A

Pancreatic Lipase

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14
Q

Increases secretion of aqueous NaHCO3 solution into duodenal lumen

A

Secretin

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15
Q

Increases secretion of pancreatic digestive enzymes into duodenal lumen

A

CCK

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16
Q

Besides the production of bile salts, what are some other functions of the liver?

A
  • Metabolic processing of fats, carbohydrates, and proteins after absorption.
  • Detoxification and degradation of body wastes, hormones, drugs, and foreign compounds.
  • Synthesis of plasma proteins.
  • Storage of glycogen, fats, iron, copper, and vitamins.
  • Involvement in the activation of vitamin D.
  • Removal of old red blood cells and bacteria.
  • Excretion of cholesterol and bilirubin.
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17
Q

What is the liver’s role in the metabolism of nutrients after they have been absorbed?

A

The liver is responsible for metabolically processing fats, carbohydrates, and proteins after they have been absorbed into the bloodstream.

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18
Q

Name one function of the liver related to the synthesis of essential nutrients or compounds.

A

The liver synthesizes plasma proteins, which are essential for various physiological functions in the body.

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19
Q

What important role does the liver play in fat digestion and absorption?

A

The liver produces bile salts, which are crucial for fat digestion and absorption in the small intestine.

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20
Q

What are the two main sources of blood that reach the hepatocytes in the liver?

A
  1. Venous blood from the digestive system via the hepatic portal vein.
  2. Arterial blood supplied by the hepatic artery.
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21
Q

What is the function of venous blood from the digestive system in the liver?

A

Venous blood from the digestive system carries absorbed nutrients and other substances to the liver via the hepatic portal vein.

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22
Q

How much venous blood flows from the digestive system to the liver every minute?

A

Approximately 1 liter of venous blood flows from the digestive system to the liver every minute through the hepatic portal vein.

23
Q

What is the role of the hepatic artery in liver blood flow?

A

The hepatic artery supplies about 350 ml of arterial blood to the liver every minute, delivering oxygen and blood-borne metabolites to the hepatocytes.

24
Q

Describe the structure of a lobule in the liver.

A

A lobule in the liver is arranged in a hexagonal shape surrounding a central vein. At each of the six outer corners of the lobule, there is a branch of the hepatic artery, a branch of the hepatic portal vein, and a bile duct.

25
Q

What structures are found at each of the six outer corners of a liver lobule?

A

At each of the six outer corners of a liver lobule, there is:

A branch of the hepatic artery.
A branch of the hepatic portal vein.
A bile duct.

26
Q

What is the function of the common bile duct in the liver?

A

The common bile duct transports bile from the liver to the duodenum, where it aids in the digestion and absorption of fats.

27
Q

What structures carry blood from the periphery of the liver lobule towards the central vein?

A

Blood from both the hepatic artery and portal vein flows through capillary-like structures called sinusoids towards the central vein.

28
Q

What cells line the sinusoids in the liver lobule, and what is their function?

A

Kupfer cells, which are macrophages, line the sinusoids in the liver lobule. Their function is to remove old blood cells and bacteria.

29
Q

What is the function of the hepatic vein in the liver lobule?

A

The hepatic vein carries blood away from the liver by converging the central veins of all liver lobules.

30
Q

What are bile canaliculi, and what is their role in the liver lobule?

A

Bile canaliculi are thin bile-carrying channels located between hepatic cells in the liver lobule. They carry bile secreted by hepatocytes from the center of the lobule to the periphery and into the bile duct.

31
Q

What guards the opening of the bile duct into the duodenum, and what is its function?

A

The sphincter of Oddi guards the opening of the bile duct into the duodenum. It remains closed until bile is needed for digestion, diverting secreted bile back up the common bile duct and into the gallbladder for storage.

32
Q

Name the main components of bile and describe its composition.

A

Bile is mainly composed of salts, cholesterol, lecithin, and bilirubin, suspended in an aqueous fluid similar to pancreatic Na HCO3 secretion. Bile salts, derivatives of cholesterol, are particularly important for fat digestion.

33
Q

What is the process called that involves the recycling of bile salts between the small intestine and the liver?

A

The process is called the enterohepatic circulation of bile.

34
Q

What percentage of secreted bile salts are comprised of old, recycled salts, and how much are newly synthesized?

A

Secreted bile salts consist of 95% old, recycled bile salts and 5% newly synthesized bile salts.

35
Q

Where are approximately 95% of bile salts reabsorbed, and what happens to the remaining 5%?

A

About 95% of bile salts are reabsorbed by the terminal ileum, while the remaining 5% are lost in feces.

36
Q

What effect do bile salts have on fats in the chyme?

A

Bile salts have a detergent-like effect on fats, converting large fat globules in the chyme into a lipid emulsion of numerous small fat droplets.

37
Q

How do bile salts increase the surface area of luminal fats, and what is the significance of this?

A

Bile salts decrease the surface tension of lipid droplets, effectively increasing the surface area of luminal fats. This increased surface area facilitates the action of pancreatic lipase, aiding in fat digestion.

38
Q

Describe the structure of bile salts and explain how it allows them to interact with fat droplets.

A

Bile salts have a lipid-soluble part that interacts with the surface of fat droplets, and a water-soluble, negatively charged end. This structure enables bile salts to decrease the surface tension of lipid droplets, breaking them down into smaller droplets.

39
Q

How do bile salts contribute to fat digestion and absorption? (2 points)

A

Bile salts have polar ends that repel each other, preventing small lipid droplets from coalescing and forming an emulsification. This increases the surface area of lipids for digestion by lipase. Additionally, bile salts bind to lipase and colipase, holding lipase at its site of action to break down triglycerides.

40
Q

What are micelles, and how are they formed?

A

Micelles are structures formed by lipid-soluble compounds surrounded by water-soluble bile salts. Bile salts, along with lecithin and cholesterol, cluster together with an outer lipophobic shell and a lipophilic core. This core contains cholesterol, digested fats, and other lipid-soluble compounds. Micelles facilitate the transport of lipid-soluble substances within the chyme to their site of absorption.

41
Q

Explain the role of colipase in fat digestion.

A

Colipase is secreted by the pancreas along with lipase. It binds to both lipase and bile salts, anchoring lipase at the surface of lipid droplets.

This allows lipase to effectively break down triglycerides into absorbable fatty acids and monoglycerides within the micelles.

42
Q

What is the primary source of bilirubin in the body?

A

Bilirubin primarily comes from the degradation of hemoglobin in old red blood cells.

43
Q

How does the color of bilirubin change throughout its journey in the body?

A

Initially, bilirubin is yellowish in color. However, bacterial enzymes, mainly in the large intestine, modify its color to the brown hue associated with feces.

Without bile secretion, feces would appear greyish-white. Most bilirubin is excreted in feces, but some is reabsorbed in the small intestine and eventually excreted in urine, giving urine its yellow color.

44
Q

What role does bilirubin play in the body’s appearance?

A

While bilirubin itself is not involved in digestion, its presence in bile gives feces its characteristic brown color. Moreover, bilirubin contributes to the yellow coloration of urine, as some bilirubin is reabsorbed in the small intestine and excreted in urine.

45
Q

What are the three main regulatory mechanisms involved in the secretion of bile?

A

The secretion of bile is regulated by chemical, hormonal, and neural mechanisms.

46
Q

How do bile salts contribute to the regulation of bile secretion?

A

Bile salts act as a potent chemical signal for the regulation of bile secretion. When bile salts are reabsorbed and return to the liver via the enterohepatic circulation, they stimulate the further release of bile.

47
Q

Which hormone stimulates the secretion of the aqueous alkaline component of bile?

A

Secretin stimulates the secretion of the aqueous alkaline component of bile but does not stimulate the release of bile salts.

48
Q

Describe the neural mechanism involved in the regulation of bile secretion during the cephalic phase.

A

During the cephalic phase, vagal stimulation of the liver promotes the release of bile before food reaches the stomach or intestine.

49
Q

What is the function of the gallbladder regarding bile storage?

A

The gallbladder stores bile that is secreted by the liver but cannot enter the duodenum due to the closed sphincter of Oddi. Bile is concentrated in the gallbladder through active transport of salt, followed by osmotic movement of water, resulting in bile being concentrated 5 to 10 times.

50
Q

What triggers the release of bile from the gallbladder into the duodenum during digestion?

A

The presence of fat in the duodenum triggers the release of bile from the gallbladder into the duodenum.

This release is mediated by the hormone cholecystokinin (CCK), which causes both gallbladder contraction and relaxation of the sphincter of Oddi, allowing bile to flow into the duodenum.

51
Q

What is a morbidity associated with the gallbladder?

A

One morbidity associated with the gallbladder is the formation of gallstones. Because the gallbladder concentrates bile, bile salts can precipitate and form gallstones.

However, the gallbladder can be removed without negative effects on digestion, as bile continues to be produced, and excess bile is stored in the common bile duct, which dilates.

52
Q

Composition of bile includes mainly ___ , ___ , ___, and ___.

A

Composition of bile includes mainly bile salts, cholesterol, lecithin, and bilirubin.

53
Q

Bile salts are derivatives of ___ and are crucial for fat digestion and absorption.

A

Bile salts are derivatives of cholesterol and are crucial for fat digestion and absorption.

54
Q

Bile salts effectively increase the surface area of the luminal fats for the action of ___ .

A

Bile salts effectively increase the surface area of the luminal fats for the action of pancreatic lipase.

55
Q

Secretin stimulates the secretion of the aqueous alkaline component of bile but does not stimulate the release of ___ .

A

Secretin stimulates the secretion of the aqueous alkaline component of bile but does not stimulate the release of bile salts.

56
Q

Bile that cannot enter the duodenum due to the closed sphincter of ______ backs up into the ___ for storage.

A

Bile that cannot enter the duodenum due to the closed sphincter of Oddi backs up into the gallbladder for storage.

PHGY 216 Mod 6 (7 decks)

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