44 + 45. Histology - Microanatomy of the Liver, Gallbladder & Pancreas

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Questions and Answers

What characterizes interlobular ducts in the pancreas?

They have no role in exocrine secretion.

They collect product from intercalated ducts. (correct)

They are lined with stratified squamous epithelium.

They are located within acinar cells.

Which substance stimulates acinar cells in the pancreas to secrete proenzymes?

Gastrin from the stomach.

Cholecystokinin (CCK) from the duodenum. (correct)

Insulin from the pancreas.

Somatostatin from the hypothalamus.

What role does secretin play in the pancreatic function?

It stimulates enzyme production in acinar cells.

It increases bicarbonate release by duct cells. (correct)

It activates pancreatic acini directly.

It inhibits ductal secretion.

Which statement regarding the control of exocrine pancreas is true?

Both hormonal and neural signals influence pancreatic function. Signup and view all the answers

Which of the following statements about the intercalated ducts is correct?

They merge to form interlobular ducts. Signup and view all the answers

What type of tissue primarily forms the internal structure of the liver parenchyma?

A specialized arrangement of hepatocytes Signup and view all the answers

Which of the following is a function of the liver that is primarily endocrine in nature?

Synthesis and release of plasma proteins Signup and view all the answers

Which of the following describes the structure of the gallbladder wall?

Has multiple layers, including an epithelial layer Signup and view all the answers

What distinguishes the gallbladder from the small intestine?

Presence of bile storage Signup and view all the answers

Which of these is NOT a function of the liver?

Emulsification of fats Signup and view all the answers

What feature characterizes hepatic sinusoids in the liver?

They are discontinuous capillaries allowing for blood filtration Signup and view all the answers

Which component of the pancreas is responsible for the exocrine functions?

Pancreatic acini Signup and view all the answers

What is the primary method by which bile flows from the liver to the gallbladder?

Along the bile ducts Signup and view all the answers

What type of epithelium lines the intrahepatic bile ducts?

Columnar epithelium Signup and view all the answers

Which layer is NOT part of the wall of the common hepatic duct?

Endothelium Signup and view all the answers

Where does lymph from the space of Disse first drain?

Periportal space of Mall Signup and view all the answers

What structure does the gallbladder connect to via the cystic duct?

Common bile duct Signup and view all the answers

What is a feature of the connective tissue surrounding the intrahepatic bile ducts as they approach the hilus?

Increasing presence of smooth muscle Signup and view all the answers

Which of the following describes the lymphatic vessels within portal canals?

They parallel the bile passageways Signup and view all the answers

What is the final destination of lymph leaving the liver?

The hilus Signup and view all the answers

What characterizes the gallbladder as described?

Distensible and bag-like Signup and view all the answers

What is one role of the fibroelastic connective tissue surrounding the intrahepatic bile ducts?

Provide structural support Signup and view all the answers

What indicates the beginning of bile flow towards the common hepatic duct?

Drainage from intrahepatic bile ducts Signup and view all the answers

What does the alcohol dehydrogenase (ADH) pathway primarily produce during alcohol metabolism?

Acetaldehyde Signup and view all the answers

What activates the microsomal ethanol-oxidizing system (MEOS) in chronic alcohol consumption?

Chronic alcohol intake Signup and view all the answers

Which compound is produced through the conjugation of unconjugated bilirubin in the liver?

Bilirubin glucuronide Signup and view all the answers

What is the role of UDP glucuronosyl-transferase in bilirubin metabolism?

Catalyzes the conjugation of bilirubin Signup and view all the answers

Which type of bilirubin is described as water-soluble following conjugation in the liver?

Conjugated bilirubin Signup and view all the answers

What is the consequence of reactive oxygen species produced by the MEOS during alcohol metabolism?

Damaged hepatocyte plasma membranes Signup and view all the answers

Where does the glucuronide conjugation of bilirubin occur within the liver?

Smooth endoplasmic reticulum (SER) Signup and view all the answers

Which cells are specifically mentioned as part of the reticuloendothelial system involved in hemoglobin degradation?

Macrophages and Kupffer cells Signup and view all the answers

What type of bilirubin is often referred to as 'indirect bilirubin'?

Unconjugated bilirubin Signup and view all the answers

What does chronic alcohol consumption lead to in terms of liver function?

Activation of MEOS and oxidative stress Signup and view all the answers

What type of epithelium is found in intercalated ducts?

Simple cuboidal epithelium Signup and view all the answers

What is the primary role of intercalated ducts in the pancreas?

To drain acini Signup and view all the answers

What do centroacinar cells primarily produce?

Bicarbonate-rich secretion Signup and view all the answers

Where are small intercalated ducts located within the pancreas?

Within the lobule Signup and view all the answers

What term is used to refer to large intercalated ducts in some texts?

Intralobular collecting ducts Signup and view all the answers

What cellular structure do intercalated ducts extend into the acini as?

Centroacinar cells Signup and view all the answers

Which of the following statements is NOT true regarding intercalated ducts?

They drain the main pancreatic duct. Signup and view all the answers

How do centroacinar cells appear in histological sections?

As lightly stained cells Signup and view all the answers

What distinguishes intercalated ducts from striated ducts in pancreatic structure?

Intercalated ducts lack striated ducts entirely. Signup and view all the answers

What is the histological feature of intercalated ducts in relation to their size?

They are consistently small. Signup and view all the answers

Study Notes

Liver Basic Concepts

Liver is part of digestive system, acting as an extramural organ.
Contains both endocrine and exocrine functions.
Endocrine function: Synthesis and release of products into blood, like plasma proteins.
Exocrine function: Production of bile.
Other functions include detoxification of blood, storage of iron, and metabolism of vitamins A, D, and E.

Liver Structure

Largest gland in the body.
Divided into four lobes, though not completely.
Parenchyma: Organized plates of hepatocytes, main liver cell type, separated by sinusoids, discontinuous capillaries.
Stroma: Dense irregular connective tissue surrounding the parenchyma.

### Hepatocytes

Main cell type of the liver.
Arranged in plates, forming functional units called hepatic lobules.
Metabolically active, participate in functions related to carbohydrates, proteins, lipids, and hormones.
Synthesis of plasma proteins, including albumin, globulins, and clotting factors.
Detoxification of drugs and toxins, using enzymes like cytochrome P450.
Production and secretion of bile, contains bile acids for fat digestion and bilirubin for removal.

Hepatic Sinusoids

Discontinuous capillaries located between hepatocyte plates.
Fenestrated endothelial lining allows for exchange of blood components with hepatocytes.
Contain Kupffer cells, phagocytic cells that remove particulate matter and old red blood cells from blood.
Contain space of Disse, a perisinusoidal space between sinusoids and hepatocytes.
Space of Disse is essential for material exchange between hepatocytes and blood.

Bile Flow

Bile produced by hepatocytes flows from the bile canaliculi (small channels between hepatocytes) into bile ductules.
Bile ductules merge into larger intrahepatic bile ducts, lined by columnar epithelium.
Right and left hepatic ducts collect bile from different liver lobes.
Common hepatic duct is formed at the hilum (porta) and carries bile to the gallbladder or duodenum.

Lymphatic Flow

Most lymph originates from the space of Disse.
Drains from the space of Disse to the periportal space of Mall between the portal connective tissue and hepatocytes.
Lymph then flows to lymphatic vessels within portal canals and exits the liver at the hilum.

Gallbladder

Distensible bag connected to the common bile duct via the cystic duct.
Function: Store and concentrate bile produced by the liver.
Contains three layers:
- Mucosa: Innermost layer, made up of simple columnar epithelium with microvilli and a lamina propria.
- Muscularis: Smooth muscle layer, helps in the expulsion of bile.
- Serosa: Outermost layer, made up of epithelial and connective tissue.

### Gallbladder Distinguishing Features

Presence of mucosal folds: Increase surface area to facilitate storage of bile.
Abundant smooth muscle: Powerful contractions for bile expulsion.
Absence of villi: Unlike the small intestine.

### Pancreas

Dual function: Exocrine (production of digestive enzymes) and endocrine (hormonal secretion).
Exocrine pancreas: Composed of acini, clusters of cells responsible for enzyme production.
Endocrine pancreas: Contains islets of Langerhans, cell clusters responsible for hormone secretion (like insulin and glucagon).

Exocrine Pancreas Anatomy

Acini: Clusters of cells that produce and secrete digestive enzymes in the form of zymogen granules.
Centroacinar Cells: Modified duct cells found in the center of acini, contribute to the pancreatic juice.
Duct System: Network of ducts that collect and transport the pancreatic juice.
Intercalated ducts: Smallest ducts, drain the acini, lined by simple cuboidal epithelium, contribute bicarbonate-rich watery secretion.
Interlobular ducts: Larger ducts located in connective tissue septae, gather fluid from smaller intercalated ducts.
Main duct: Major duct that carries the pancreatic juice to the duodenum.

Pancreas Endocrine Function

Islets of Langerhans: Clusters of endocrine cells embedded within the exocrine tissue.
Alpha cells: Secrete glucagon, raising blood glucose levels.
Beta cells: Secrete insulin, lowering blood glucose levels.
Delta cells: Secrete somatostatin, regulating hormone release from other cells.

Pancreatic Enzyme Secretion

Acinar cells: Secrete proenzymes (inactive digestive enzymes) that are activated by proteases in the duodenum.
Cholecystokinin (CCK): Hormone secreted from enteroendocrine cells in duodenum, stimulates acinar cell enzyme secretion.
Acetylcholine: Neurotransmitter released from parasympathetic nerves, stimulates acinar cell secretion.
Secretin: Hormone secreted from enteroendocrine cells in duodenum, stimulates duct cells to release bicarbonate-rich secretion.

Biliary System and Enterohepatic Circulation

Biliary system: Network of ducts transporting bile from the liver to the gallbladder and subsequently to the duodenum.
Enterohepatic circulation: Recycling of bile acids from the intestines back to the liver, enhancing fat digestion.

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Description

This quiz covers the basic concepts and structure of the liver, highlighting its vital roles in the digestive system. Learn about the liver's endocrine and exocrine functions, the organization of hepatocytes, and the key metabolic activities of liver cells. Test your knowledge on this essential organ!