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Digestive Anatomy
Fish Liver
Hepar
The largest internal organ in most fish - handling metabolism, detoxification, and (uniquely in sharks) providing buoyancy through massive oil stores.
Region: Trunk Universal in fish Unique to: all
📖 Overview
The fish liver is metabolically central. It filters blood, stores glycogen, produces bile, and detoxifies contaminants. In sharks and other cartilaginous fish, the liver takes on an additional role - buoyancy. Shark livers can constitute 25% of total body weight, filled with squalene and other low-density oils that give the fish neutral or near-neutral buoyancy despite lacking a swim bladder. Cod liver oil - a source of vitamin D and omega-3s - has been a major human food and medicine for centuries.
🧬 Structure
Large, dark-brown organ occupying much of the anterior body cavity. Divided into two or more lobes. Contains bile-producing hepatocytes, blood-filtering sinusoids, and Kupffer cells (immune).
⚙️ Function
Metabolism (protein, carbohydrate, lipid), glycogen storage, bile production, detoxification, plasma protein synthesis. In sharks: oil-based buoyancy control via squalene and diacylglycerol ethers.
🐠 Variations Across Species
Shark livers: massive, oil-rich. Cod livers: yield the classic vitamin D-rich cod liver oil. Deep-sea fish: often enlarged with wax esters for buoyancy.
🩺 Related Diseases
Hepatic lipidosis (fatty liver, from overfeeding), granulomatous hepatitis, tumours (linked to pollutant exposure - one of the earliest bio-indicators used in ecotoxicology).
✨ Fun Fact
A basking shark liver can weigh over half a ton - more than the average family car engine. It was historically rendered for lamp oil throughout Ireland and Scotland.
🔗 Related Digestive Structures