We have all heard of crocodile tears, and we know that the crocodile may not weep in sincerity. But not many understand the crocodile heart.
Of course if you had the time to read my book, “The Sixth Season, Gudjewg,” you would learn much about crocodiles and much about the six seasons of what we know today as Arnhem Land.
But this is about “hearts” right? It is about the crocodile heart.
You know that crocodiles are reptiles. And you may, or may not know, that reptiles are not like humans in that they have a 3 chambered heart while mammals have a four chambered heart.
The strange thing is that these “prehistoric” monsters are the exception to the reptile breed and they do have a crocodile heart rather like ours. Yes, they have the four chambered heart that we have come to know and love so much.
Crocodile heart and some anatomical knowledge
“The enormous crocodile — owner of nature’s most complex heart.
Unlike us, however, they have two aortas — the blood vessel in humans that carries blood from the heart to the rest of the body. They have a right aorta that comes out of the left ventricle and a left aorta from the right ventricle”.
British Heart Foundation – Link to Article
But what about the foramen of panizza? The crocodile heart has one, but we mere humans do not!
This little valve controls the flow of blood and the clever beasts can shunt blood where and when they want.
The really clever bit is that crocodiles can take the best of the best and send that oxygenated blood to the brain. The poorly oxygenated blood can be sent to the tail where the best of the blood is not desperately required.
Let’s get a bit more scientific about the crocodile heart.
“The heart of a crocodile is different to other reptiles in that it has four chambers just like birds and mammals. Blood is sent to the lungs for gas exchange from the right, and from the left ventricle it is pumped to the body. Thus the two types of blood do not mix in the heart. However, what is interesting is that blood is mixed as soon as it leaves the heart via a valve (foramen of panizza) placed in between the right and left aorta.”
The record for a human holding their breath under water is around 12 minutes. Elephant seals can get up to around 2 hours, and a Cuvier’s beaked whale once clocked a dive of over 137 minutes. But the longest recorded dive for a crocodile is 387 minutes, and Professor Franklin believes they can manage up to 8 hours in colder waters before resurfacing for air.
Can you see that the crocodile is a well-engineered beast?
Now I know that you are keen and you want more on the valve and how it works.
The valve in question.
Adding to the anatomical complexity is a valve found at the top of the right ventricle that looks like a pair of cog-teeth, which the animals can actively control to redirect the flow of blood. This set-up effectively allows crocodiles to stop blood flowing from the heart to the lungs, and instead just cycle it continually around the body with each beat.
In humans, every heartbeat circulates blood to both the lungs and the body. This means the lungs are emptied of oxygen very quickly. However, Professor Franklin’s research suggests that the nifty little ‘cog-teeth valve’ in crocodile hearts can be actively opened and closed to let a small amount of blood flow to the lungs. This allows the animals to occasionally dip into the store of oxygen in their lungs, just to top up the cells that need it most.
When the croc prepares for a long dive, it fills its lungs, dives and then slows its heartbeat down to between 7–10 beats per minute. It then uses the valve to close off the lungs and, with just one half of the heart now working, the blood is also channelled to a few vital organs. This all helps the crocodiles to use less energy, and only send blood to the lungs to pick up oxygen when it is absolutely necessary.
Primitive?
We think them primitive, but they have many facets that leave us for dead.
Here I am not referring to their capacity to attack and kill humans. I will come to that on another day, but here it was merely used as a figure of speech.
But, when it comes to crocodiles, there some other significant issues.
- The power and strength of the beast – coming.
- The biting power of those mighty jaws – to be discussed.
- Those marvellous eyes.
- Sounds and hearing? A teaser?
Vibrations within his muscle walls send sound waves rippling out into the swamp, powerful enough to make the water dance. Part of his roar radiates at such low frequency that human ears can’t hear it. But these subsonic calls have astounding penetration, travelling four times faster, and further, under the water.
more coming…………………
5. The massive killing teeth and the ability to replace lost teeth.
6. The ability to stay at length, virtually undetected, underwater.
Read my book to find out just how the crocodile can be detected.
And much more.
Conclusion:
I have listed numerous attacks and I am still working on this aspect of the website. But please note that even though I have been busy on other things I have been working in the background to develop my little website.
I don’t want people to think my website is just about crocodile attacks.
It is meant to be about Crocodiles, but other things, too:
- The Northern Territory and Darwin.In this, I want to focus particularly on the way it was for us, we few Darwin boys and girls, growing up in Darwin in the sixties.
- The seasons – the smell of the earth and the grass, the sounds of a tropical storm. The heavy rain and flooding all so different from seasons in the South: Summer? Winter?
- The birds. Waking early in the pre-dawn to the sound of millions of birds. A bucket list item for sure.
- The animals. There is a world of cities and skyscrapers and people in suits with ties hanging around their necks. Yet there is another parallel universe where creatures are seen in shorts and thongs. And all kinds of creatures abound. I will tell you some of it and I will say, “You will never, never know, if you never never go” or words to that effect. If you have never been, you should go and see it, and feel it.
Well, I do have a lot of work to do.
By the way
By the way, in my novel, “The Sixth Season, Gudjewg” my crocodile uses his unique heart and circulation system to escape from the hero of the story. It has been said that the book is both educational and entertaining.
If you prefer your education and enlightenment with a spice of adventure and drama, you should read the book about Joe and that crocodile.
Cheers for now.
Leighton