The best thing about exploring is to find something unexpected while poking around on the land.
As an ear, nose, and throat surgeon it was exciting for me to come upon the bony remains of a whale including the vertebral column and the skull. It was on a terrace above the beach at Dundas Harbour. Whales are air breathing mammals that live mostly under the water. Whales breathe through a hole, the blowhole in the top of the skull. The hole is homologous to the nostrils in other mammals. During evolution the nostrils in whales have moved to the top of the head.
As the whale surfaces to breathe they initially exhale forcibly pushing air from the lungs out through the blow hole in the top of the head. This can be seen as a sheet of mist or can look like a geyser.
This exhalation of fluid from high to lower pressure produces condensed water vapor known as the blow. This also includes water sitting on top of the blow hole. The blowhole is covered by a muscular nasal plug which allows the hole to open and close and is closed tight during a dive. The inhaled air goes through the blowhole directly into the trachea and the lungs. There is no opening from the blowhole into the oral cavity so whales cannot breathe through their mouth.
This is of great importance practically. Balleen whales can safely take in hundreds of gallons of sea water into their mouth which is filtered through keratinous plates attached to their upper jaws called balleen. The filtered sea water which contains the whale's food source, krill and plankton, is pushed by the tongue to the back of the mouth and swallowed. Bowhead whales can swallow as much as 2 tons of plankton each day. The remaining sea water is expelled back into the sea. At no time is it physically possible for the whale to aspirate sea water into the lungs because the air and food passages are anatomically separated.
What a thrill to examine a whale skull and see where the blowhole opens.
The other interesting aspect of the whale skull is the cochlea on the inner surface of the jaw. The hearing apparatus in whales is adapted for underwater hearing. Whales do have ear canals but they are narrow, plugged with debris and wax, and are not attached to the ear drum. Sound is conducted to the middle and inner ears through soft tissue channels and bone.There is an air filled middle ear inside their jaw where they have mammalian ossicles - the maleus, incus and stapes bones.
The cochlea is hypertrophied. In addition whales have a significantly increased number of auditory nerve fibers. The whales are thus wired for more complex signal processing than most mammals.
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