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Excretory Anatomy
Rectal Gland (Sharks)
Glandula rectalis
A finger-like salt-excreting gland unique to sharks, rays, and chimaeras - the primary mechanism for maintaining osmotic balance in seawater.
Region: Trunk Unique to: cartilaginous
📖 Overview
Cartilaginous fish live in seawater with blood salinity below the ocean\'s. To prevent salt accumulation, they excrete concentrated sodium chloride solution via a specialised rectal gland that drains into the cloaca.
🧬 Structure
Elongated finger-shaped organ opening into the terminal intestine or cloaca. Composed of specialised salt-secreting cells rich in Na+/K+ ATPase.
⚙️ Function
Actively transports sodium and chloride ions out of the blood into a concentrated saline solution that is voided.
✨ Fun Fact
The rectal gland of sharks was the primary model system for understanding chloride transport in vertebrates - foundational research that informed cystic fibrosis biology in humans.
🔗 Related Excretory Structures