Shark anatomy 101

​Sharks are one of the ocean’s most famous and intriguing creatures. They easily dominate portrayals of marine life in pop culture from their iconic dorsal fins to their reputations as bloodthirsty predators. Read below about the internal and external anatomy of sharks to learn about what the purpose of each of their fins are, how they hunt their prey and how some of their organ functions differ from humans.

External anatomy:
A.External Nares: Near the tip of the shark’s nose, or its rostrum, these are two openings, one on each side, used for sensory activities. Water is taken up through the smaller opening, passes by a sensory membrane and then released through the larger opening. This helps sharks detect blood of prey and determine water quality.

B.Dorsal fin: This iconic fin keeps the shark upright and prevents it from turning over in the water. This fin is necessary for sharks to maintain stability, however, they are often sought after in the illegal practice of “finning.” Finning involves removing a shark’s dorsal fin for human use such as making shark fin soup or using it as a home decoration.

C.Pectoral fin: This fin helps the shark steer. It acts similar to wings on an airplane.

D.Caudal fin: The largest and most powerful fin on the shark’s body, the caudal fin helps keep the shark from floating up without using much energy.

E.Ampullae of Lorenzini: This part of the shark uses electroreception. It senses electrical impulses in the water, such as the heartbeat of its prey in the sand, and also allows the shark to read changes in temperature, salinity and water pressure.

Internal anatomy:
F.Liver: Taking up roughly 80% of the shark’s internal body cavity, the liver is the largest of sharks’ organs. The liver stores energy as dense oil which helps the shark with buoyancy, its ability to float. It also works as a part of the digestive system and helps filter toxins out of the shark’s blood.

G.Spleen: A shark’s spleen’s purpose is to create red blood cells. In humans, red blood cells are created in bone marrow, however, sharks have no bones or bone marrow. A shark’s spleen is the main part of its immune system.

H.Rectal gland: The rectal gland plays a vital role in osmoregulation, regulating the shark’s salt balance. This helps sharks stay hydrated by excreting high amounts of concentrated salt.

I.Heart: Sharks have an S-shaped heart, and it pumps deoxygenated blood through its arteries to the gills where it is oxygenated and distributed through the rest of the body.

J.Stomach: Shark stomachs are shaped like a J and are covered with rugae, wrinkles that increase its size digestion and nutrient absorption.