Liver Anatomy & Physiology Quiz

Liver Anatomy & Physiology

• The liver is a large, essential organ located in the upper right quadrant of the abdomen.
• It has a right and left lobe.
• The liver weighs approximately 1.4-1.8 kg in adults and slightly less in women.
• A key feature of the liver is its remarkable ability to regenerate if a portion is lost or removed surgically.
• It's considered the body's "chemical factory" performing multiple crucial functions.

Liver Objectives

• Analyze the liver's vascular, parenchymal, and biliary anatomy.
• Detail the structure and function of the hepatic lobule, stellate, and Kupffer cells.
• Describe the steps involved in bilirubin metabolism.
• Discuss the liver's role in metabolism, synthesis, detoxification, immunity, and digestion.

Liver Overview

• The liver has a dual blood supply, receiving oxygenated blood from the hepatic artery and deoxygenated blood from the hepatic portal vein containing nutrients from the digestive tract.
• Venous blood exits the liver through the hepatic veins.
• The liver is not vascularized with a capillary network like most other organs. Instead, blood flows through sinusoids surrounding the hepatic cells.

Liver Anatomy

• The liver has three distinct compartments: vascular, parenchymal (histological), and biliary.
• The liver is divided into anatomically distinct segments (Couinaud's segments).
• Each segment has its own hepatic artery, portal vein, hepatic vein and biliary branches.

Liver - Vascular Anatomy

• The hepatic artery delivers oxygen-rich blood.
• The hepatic portal vein brings deoxygenated blood, rich in nutrients absorbed from the digestive tract.
• These two sources mix within the sinusoids.
• Blood exits the liver via the hepatic vein.

Hepatic Blood Flow

• Hepatic vein
• Sinusoids
• Segmental hepatic artery and portal vein
• Hepatic artery and portal vein
• Lobular hepatic arteriole and hepatic venule

Hepatic Lobule - Anatomy

• Hepatic lobules are the fundamental functional units of the liver tissue.
• Arranged in a hexagonal shape.
• Each lobule contains a portal triad (hepatic artery, portal vein, bile duct) at each corner.
• Hepatocytes are arranged in cords between sinusoids and a central vein.
• Hepatic acinus is a functional unit within a lobule. It has distinct zones related to blood access.

Hepatocytes

• Hepatocytes are the dominant cell type (about 80%) in the liver.
• Round in shape, containing a nucleus, endoplasmic reticulum, Golgi apparatus, and numerous mitochondria.
• Responsible for various metabolic functions.
• Some hepatocytes are near the sinusoidal walls (which are formed by endothelia) separated by the space of Disse.

Supporting Cells: Kupffer Cells

• Kupffer cells are mononuclear phagocytic cells located in the hepatic sinusoids.
• Play a crucial role in breaking down red blood cells and removing bacteria.
• Part of the liver's innate immune response.

Supporting Cells: Stellate Cells

• Stellate cells are located in the perisinusoidal space (Space of Disse).
• Responsible for vitamin A storage and metabolism.
• When activated by injury/inflammation, they transform into collagen-producing myofibroblasts contributing to hepatic fibrosis.

Liver Components

• Hepatocytes form cords between a highly specialized capillary network and the central vein.
• Supporting cells, like Kupffer cells and stellate cells, live within and around the sinusoids and space of Disse.

Biliary System

• Bile is produced by hepatocytes and released into bile canaliculi.
• Bile canaliculi merge to form larger bile ducts, eventually leading to the common bile duct.
• Bile salts are crucial for fat digestion and absorption.
• Enterohepatic circulation explains the continuous recycling of bile salts.

Gall Bladder

• Stores and concentrates bile.
• Releases stored bile into the small intestine when needed for fat digestion.
• Controlled by hormones like cholecystokinin.

Bilirubin Metabolism

• Bilirubin is a yellowish pigment made as a byproduct of the breakdown of red blood cells.
• This breakdown process occurs in mononuclear phagocytes.
• Bilirubin is initially insoluble, transported by albumin, then conjugated within hepatocytes.
• Conjugated bilirubin is excreted into bile, processed in the gut, then eliminated in feces.

Physiologic Neonatal Jaundice

• Jaundice is a condition where bilirubin levels can accumulate, leading to a yellowish hue in the skin or eyes.
• In newborns indirect bilirubin is a typical problem and usually mild and transient. The neonatal liver has reduced capacity to conjugate bilirubin.

Liver Functions: Metabolism and Synthesis

• The liver plays a vital role in glucose homeostasis (glycogenesis, gluconeogenesis).
• It also regulates fat metabolism (lipogenesis, lipolysis), synthesizes cholesterol, and plays a role in amino acid metabolism.
• The liver synthesizes essential plasma proteins like albumin and clotting factors.

Liver Functions: Detoxification and Immunity

• The liver detoxifies various endogenous and exogenous substances.
• Ammonia, a toxic byproduct of protein metabolism, is converted to urea by the liver and excreted.
• The liver is populated by immune cells monitoring antigens (like from food) to maintain tolerance within the body.

Liver Functions: Digestion

• The liver produces bile, which is transported to the small intestine.
• Bile salts aid in fat and fat-soluble vitamin absorption.
• Enterohepatic circulation cycles bile salts for continuous recycling and use.

Test your knowledge on the anatomy and physiology of the liver. This quiz covers key aspects such as liver structure, functions, and its role in metabolism and detoxification. Dive into details about the hepatic lobule and bilirubin metabolism for a comprehensive understanding of this vital organ.