Anatomy & Physiology

Anatomy & Physiology

Blue whale anatomy image by Uko Gorter.

Cetacean body structure is similar to most other mammals with tails, except for the missing hind limbs. Ribs are not attached to the vertebrae; only the first pair connect to the sternum. Openings for nostrils, their blowholes, are on the top of the head. Baleen whales have two blowholes, toothed whales have one blowhole.

Their spine moves mainly up and down like other mammals, pressing their tail flukes against the water so they can move forward. However, they can move sideways; one local biologist has even seen a whale scratch the side of its head with the tip of one its flukes.

Relative weight of skeletal components of cetaceans = 45% head and ribs, 45% vertebral column, 10% limbs.

They have a four-chambered heart that is set fully forward in the rib cage. Their lungs are closer to the vertebrae than to the sternum.

They have lobed kidneys, rather than smooth kidneys.

Cetacean muscle contains lots of myoglobin, an oxygen carrying protein similar to hemoglobin. This stores oxygen needed by cetaceans when they dive for long periods of time. This makes their muscle look very dark.

They can hold their breath for extended periods of time. Their muscle stores a great deal of oxygen, their rib cage collapses, the body cuts through the water, their powerful tails push their streamlined bodies through the water efficiently, their lungs exchange old air for new much better than human lungs, they tolerate high levels of carbon dioxide and are able to replace it with oxygen during their visits to the surface. The nitrogen in their blood stream stays at an overall steady state.

Odontocete life spans range from 24 years (e.g. harbor porpoise) to 70+ years (sperm whale)
Mysticete life spans often mirror human life spans, 60+ years, with some, like the bowhead, living well past 100.

Mysticete females on average are 5% larger than males
Sperm whale males are significantly larger than females
Longest whale ever caught was a female blue whale caught in 1926 in the Southern Ocean that measured 109 feet (33.26m).

Heaviest whale ever caught was a female blue whale caught in the Southern Ocean January 1948 that weighed 300,710 pounds (136.4 metric tons).
* These two animals are from confirmed reports. There are unconfirmed reports for one or two longer whales and heavier whales.