05.2 Liver and pancreas anatomy and function

Liver and Pancreas Anatomy and Function

• The liver and pancreas are vital for metabolism, digestion, and detoxification.
• The liver's unique blood supply, lobular zonation, bile synthesis, and glucose regulation are crucial.
• The pancreas's exocrine function in enzyme secretion and bicarbonate release is essential for digestion.
• Liver steatosis, toxic injury, and diabetes-related metabolic changes are important clinical considerations.

Learning Objectives

• Objective 1: Describe the liver's position and functional anatomy.
• Objective 2: Outline major liver functions (storage, synthesis, biotransformation).
• Objective 3: Explain venous drainage pathways from the digestive tract to the hepatic portal vein.
• Objective 4: Describe the pancreas's position and functional anatomy.
• Objective 5: Discuss pancreas's exocrine functions (enzyme and bicarbonate production).

Key Concepts and Definitions

• Liver Anatomy: Located in the RUQ, largely intraperitoneal, with four lobes (right, left, caudate, quadrate), connected by the falciform ligament.
• Portal Venous System: Major blood supply (60-70%): carries blood from the spleen and superior mesenteric veins to the liver from the GI tract.
• Hepatocytes: Principal liver cells (80% of liver mass), responsible for CHO, fatty acid, and protein metabolism, detoxification, and albumin production.
• Pancreas Anatomy: Located in the C-shaped curve of the duodenum, mostly exocrine (85%), with essential endocrine roles (insulin, glucagon).
• Liver Zonation: Hepatic lobules have three zones with varying oxygenation and metabolic function; Zone 1 (oxygen-rich, prone to toxin exposure), Zone 3 (susceptible to ischemic injury).

Clinical Applications

• Case Study: Pediatric steatosic liver disease often shows Zone 1 injury, contrasting with Zone 3 injury in adults.
• Diagnostic Approach: Recognizing zonal injury patterns (toxic injury, ischemic injury) helps diagnose liver pathologies.
• Treatment Options: Lifestyle modifications (e.g., dietary adjustments) are critical for managing fatty liver disease.
• Complications/Management: Steatosis and insulin resistance can lead to type 2 diabetes, requiring careful monitoring of metabolic functions and liver health.

Pathophysiology

• Liver Zonation and Injury: Blood flow in hepatic lobules creates zones specialized in metabolism and injury susceptibility (Zone 1 is more vulnerable to toxins, Zone 3 to ischemia).
• Hepatic Fatty Acid Metabolism: Fatty acids enter the liver from diet, chylomicron remnants, or system, managed via de novo lipogenesis (DNL) or oxidation/storage in VLDL, impacting systemic lipid levels.

Pharmacology

• VLDL Synthesis and Metabolism: Increased by insulin resistance, excess calories, and lack of physical activity; impacts cardiovascular risk.
• Bile Acid Synthesis: Two pathways exist: classical (CYP7A1-dependent) and alternative (<10% contribution).

Differential Diagnosis

• Non-Alcoholic Fatty Liver Disease (NAFLD): Hepatic fat accumulation without significant alcohol, linked to metabolic syndrome and insulin resistance.
• Pancreatic Exocrine Insufficiency (PEI): Results from decreased pancreatic enzyme secretion (e.g., chronic pancreatitis or cystic fibrosis), causing malabsorption.
• Liver Cirrhosis: Advanced liver disease with fibrosis, disruptive hepatic architecture and portal hypertension; distinguishable from fatty liver by histological findings.

Investigations

• Liver Function Tests (LFTs): Measure hepatic enzyme levels (ALT, AST), bilirubin for liver cell/biliary function assessment.
• Abdominal Imaging (e.g., Ultrasound, MRI): Evaluate liver fat content, size, and anatomical anomalies (e.g., hepatomegaly).
• Serum Lipid Profile: Monitor VLDL, LDL, HDL for insights into systemic lipid metabolism and cardiovascular risk.

Summary and Key Takeaways

• Liver structure, zones, and metabolic functions are key to health.
• Fatty acid metabolism is affected by diet, insulin sensitivity, and physical activity, influencing systemic lipid levels.
• Pancreatic exocrine function is vital for digestion.

Further Reading/References

• Chiang JY (2013), Mehta & Shapiro (2022), Frayn KN (2010)

This quiz explores the anatomy and functions of the liver and pancreas, highlighting their roles in metabolism and digestion. You will learn about the unique blood supply of the liver, its major functions, and the pancreas's exocrine roles. Additionally, clinical considerations related to liver health and metabolic changes will be discussed.