11 de febrero de 2026

Overview of Liver Anatomy and Biliary Tract

Introduction to the Digestive System

• The digestive system is referred to as the gastrointestinal tract, with a focus on liver anatomy and the biliary region.

Embryological Origin of the Liver

• The liver originates from mesenchyme derived from the endoderm formed in the anterior mesogastrium. This embryological background is crucial for understanding liver development.

Segmentation of the Liver

• Liver segmentation is determined by the branching of the portal vein rather than anatomical structures like ligaments. The portal vein divides into right and left branches, further subdividing into four segments each.

• Venous drainage follows a similar pattern through hepatic veins, reinforcing that division should be based on vascular structure rather than superficial anatomy.

Visualizing Liver Division

• An illustration shows how an imaginary line divides the liver into left and right sections, passing through key structures such as the gallbladder and hilum where major vessels enter. Understanding this division aids in identifying liver segments more clearly.

Coinout Method for Segment Identification

• The Coinout method identifies eight segments within the liver, which can be memorized using visual aids or diagrams to facilitate learning about their locations and relationships to surrounding structures like ligaments and vessels.

Understanding Segment Locations

Drawing Techniques for Segment Visualization

• A drawing technique helps visualize segment locations:

• The liver resembles a square shape.

• Key landmarks include gallbladder positioning relative to segments four and five.

• Lines are drawn to delineate medial (left/right) and lateral (left/right) sectors, leading to identification of eight distinct segments.

Importance of Specific Segments

• Segments four (quadrate) and five are particularly significant due to their surgical relevance; they are often encountered during laparoscopic procedures because they lie adjacent to critical structures like the gallbladder. Understanding their location is essential for clinical practice.

Hepatic Segmentation and Anatomy

Understanding Hepatic Segments

• The speaker illustrates the hepatic segments, specifically segment four (paramedial left) and segment five (paramedial right), emphasizing their anatomical positions relative to each other.

• Segment four is further divided into 4A (superior) and 4B (inferior), highlighting the importance of these subdivisions in surgical contexts.

Identifying Hepatic Sectors

• The speaker explains how to identify sectors based on segments: medial left includes segments one and four; medial right includes segments five and eight; lateral left includes segments two and three; lateral right includes segments six and seven.

• Proper identification of these sectors is crucial for surgical procedures, as it aids in understanding liver anatomy during operations.

Surgical Relevance of Liver Anatomy

• The anterior segments, particularly four and five, are noted as more accessible during surgeries compared to posterior ones like segment seven or two due to their locations.

• The caudate lobe (segment one) has a close relationship with the vena cava, which is important for surgical navigation around this area.

Biliary System Overview

• Anatomically, bile drains from the gallbladder through the cystic duct into the common hepatic duct formed by the right and left hepatic ducts before joining with the cystic duct to form the common bile duct.

• The journey of bile culminates at the major duodenal papilla where it enters the small intestine, underscoring its significance in digestion.

Gallbladder Structure and Function

• The gallbladder consists of several parts: fundus, body, infundibulum/bacinete, leading into the cystic duct. This structure can be prone to obstruction by gallstones.

• Histologically, it shares layers with gastrointestinal tract structures but features unique elements such as Rockitansky sinuses that serve secretory functions related to bile storage.

Importance of Calot's Triangle

• Blood supply to the gallbladder comes from the cystic artery—a branch of the right hepatic artery—highlighting its anatomical relevance in surgeries involving this organ.

• Calot's triangle is defined by key structures: cystic artery, common hepatic duct, and cystic duct. It’s critical for avoiding biliary injuries during laparoscopic surgery.

• A larger anatomical concept known as hepatocystic triangle incorporates liver tissue as a boundary instead of just focusing on Calot's triangle. This distinction is vital for safe dissection practices in surgery.

Understanding the Hepatocystic Triangle

Anatomy of the Hepatocystic Triangle

• The hepatocystic triangle, also known as Calot's triangle, is a critical anatomical area that includes important structures such as the cystic artery.

• Proper dissection of this area is essential to identify all structures and prevent common viability injuries during surgical procedures.

• This segment concludes a review of gastrointestinal tract anatomy, integrating knowledge from embryology for a comprehensive understanding of basic sciences related to liver and biliary anatomy.