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Chapter 16: Digestive system > 16.5 Pancreatic and Biliary secretions > Flashcards

16.5 Pancreatic and Biliary secretions Flashcards

1
Q

Where are the exocrine pancreas and biliary secretions released?

A

into the duodenum

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2
Q

Describe the pancreas

A

It is an elongated gland that lies behind and below the stomach, above the first loop of the duodenum. It is composed of exocrine and endocrine tissue.

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3
Q

Which tissue is more predominant in the pancreas?

A

Exocrine

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4
Q

Explain what the exocrine tissue of the pancreas is made up of?

A

it consists of grape-like clusters of secretory cells that form sacs known as acini, which connect to ducts that eventually empty into the duodenum.

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5
Q

Explain what the endocrine tissue of the pancreas is made up of?

A

It consists of isolated islands of endocrine tissue, the islets of Langerhans, which are dispersed throughout the pancreas.

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6
Q

What are the 2 most important hormones that the islet of Langerhans secretes?

A

insulin and glucagon

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7
Q

What two components make up pancreatic juice?

A
  1. Pancreatic enzymes: secreted by the acinar cells that form the acini
  2. An aqueous alkaline solution: actively secreted by the duct cells that line the pancreatic ducts. The aqueous alkaline solution is rich is sodium bicarbonate
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7
Q

Like pepsinogen, pancreatic enzymes are stored within………….

A

zymogen granules after being produced and released by exocytosis when needed.

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8
Q

The exocrine pancreas secretes ?

A

a pancreatic juice

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8
Q

What are the three types of pancreatic enzymes that the acinar cells secrete that are capable of digesting the three foodstuffs?

A
  1. Proteolytic enzymes which digest proteins
  2. Pancreatic amylase which digests carbohydrates
  3. Pancreatic lipase which is the only enzyme that digests fats
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9
Q

What are the three major pancreatic proteolytic enzymes?

A

Trypsinogen, chymotrypsinogen, and procarboxypeptidase

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10
Q

What enzyme activates trypsinogen into its active form trypsin when it enters the duodenal lumen?

A

Enteropeptidase (formerly known as enterokinase)

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11
Q

Where is enteropeptidase located?

A

in the luminal membrane of the cells that line the duodenal mucosa.

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12
Q

What is the purpose of trypsin inhibitor which is also produced by the pancreas

A

It blocks trypsin’s action if trypsinogen spontaneously gets activated in the pancreas.

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13
Q

What enzyme activates chymotrypsinogen and procarboxypeptidase into chymotrypsin and carboxypeptidase in the duodenal lumen?

A

trypsin

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14
Q

Each of the three pancreatic proteolytic enzymes tackle different _________linkages resulting in amino acids and a few small peptides (absorbable units of proteins)

A

peptide

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15
Q

What is the purpose of the intestinal mucus?

A

It protects the small intestine wall against self digestion caused by the activated proteolytic enzymes

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16
Q

What is the
disaccharide and branched polysaccharide that pancreatic amylase breaks amylopectin and amylose into?

A

maltose and a-limit dextrins

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17
Q

Why is pancreatic amylase secreted in its active form?

A

Because it does not endanger the secretory cells since they do not contain polysaccharides but are made up for proteins

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18
Q

What are the names of the very small amount of lipase released by the saliva and stomach?

A

lingual lipase and gastric lipase

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19
Q

What is the action of pancreatic lipase?

A

it hydrolyses dietary fats (triglycerides) into absorbable fat
units being monoglycerides and free fatty acids

20
Q

What is the main condition that arises from the deficiency of pancreatic enzymes?

A

steatorrhea: this is caused by excessive undigested fat which causes the feces to contain high amounts of fat. Leading to the stool being bulky, plae, and foul smelling and may float in water.

20
Q

What two processes in the pancreas are necessary for the secretion of sodium bicarbonate?

A
  1. Bicarbonate generation within pancreatic cells
  2. Bicarbonate uptake from plasma
20
Q

Why is pancreatic lipase also released in its active form?

A

because there is no risk of the pancreas self-digesting itself due to lipase, the pancreas is made up of proteins and not fats

20
Q

Why is it that Carbohydrate and protein digestion is not impaired to such a great extent as fat digestion when there is pancreatic enzyme deficiency?

A

This is because there are so many enzymes that digest carbs and proteins whereas for fats, pancreatic lipase is the only enzyme that digests it.

20
Q

In what kind of environment do pancreatic enzymes operate optimally?

A

Alkaline

21
Q

What are the two mechanisms by which bicarbonate is secreted into the duct lumen?

A
  1. Cl- -HCO3- antiporter
  2. CFTR channel
22
Q

What two enterogastrones regulate pancreatic exocrine secretion the most (in the intestinal phase of digestion when chyme enters the duodenum)?

A

secretin and CCk

23
Q

What is the influence of secretin on pancreatic secretion?

A

Its release from the duodenal mucosa into the bloodstream is stimulated by the presence of acid in the duodenum. It then travels to the pancreas where it stimulates the duct cells to increase the secretion of sodium bicarbonate which neutralises the acid in the duodenum.

24
Q

What is the influence of cholecystokinin on pancreatic secretion?

A

Its release from the duodenal mucosa and into the bloodstream is stimulated by the presence of fat digestion and protein digestion products in the duodenum. It then travels to the pancreas to stimulate the acinar cells to secrete pancreatic enzymes for digestion, particularly pancreatic lipase and pancreatic proteolytic enzymes

25
Q

It is important to note that all the pancreatic enzymes are released at ……………..proportions and not according to the meal that is eaten

A

fixed

26
Q

What does trophic mean?

A

growth-promoting effects.

27
Q

Besides pancreatic juice, what other secretion is released into the duodenal lumen?

A

bile

28
Q

what three things is the biliary system made up of?

A

Liver, gallbladder and associated ducts

29
Q

What is the largest and most important metabolic organ in the body?

A

The liver

30
Q

What are the ten functions of the liver?

A
  1. Bile salt secretion (the liver’s only direct role in digestion)
  2. Metabolic processing
  3. Detoxification
  4. Plasma protein synthesis
  5. Storage
  6. Vitamin D activation
  7. Hormone secretion
  8. Acute phase protein production
  9. Cholesterol and bilirubin excretion
  10. Immune function
31
Q

What are hepatocytes?

A

These are the main functional cells of the liver that perform a broad range of metabolic and secretory tasks. However, they are unspecialised

32
Q

What are kupffer cells?

A

These are specialised liver cells which specialise in phagocytosis helping to remove bacteria and worn RBCs.

33
Q

True or false: The liver has dual blood flow

A

true

34
Q

What are the two sources that the liver receives blood from?

A

Arterial blood: Delivered by the hepatic artery to supply oxygen and metabolites to the hepatocytes.
Venous blood: Delivered via the hepatic portal vein which carries nutrient-rich blood from the digestive tract directly to the liver for processing. This unique vascular connection is known as the hepatic portal system. This system ensures that nutrients, toxins, and other substances absorbed from the DT are processed by the liver before entering the general circulation.

35
Q

What is the name of the network of capillaries that the hepatic portal vein branches into within the liver

A

liver sinusoids

35
Q

What is the purpose of liver sinusoids?

A

they allow for efficient exchange between blood and hepatocytes.

35
Q

What occurs after the liver has processed the blood from the digestive tract?

A

The blood then drains into the hepatic vein which then joins the inferior vena cava returning the blood to the heart.

36
Q

True or false: The hepatic portal vein and hepatic vein are the same thing

A

false

36
Q

The liver is organized into functional units called……….

A

lobules

37
Q

What are lobules?

A

they are hexagonal columns of tissue centred around a central vein.

37
Q

Explain the structure of the liver lobules

A

Each lobule is made up of two rows of hepatocytes arranged in plates that are two cells thick. These plates are organised around a central vein which is the vcore of the lobule. At all six corners of the lobule, there are three key components.

38
Q

What cells produce bile

A

Hepatocytes

38
Q

DIDNT FINISH ALL FLASH CARDS

A
38
Q

What are the three key structures of each of the 6 corners of the lobule?

A
  1. A branch for the hepatic artery
  2. A branch for the hepatic portal vein
  3. A bile duct
39
Q
A
40
Q
A

Chapter 16: Digestive system (6 decks)

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