Pivot Joint

[tmaromine]

My health teacher made an interesting point today: only apes/monkeys – and thus evolutionarily in turn, us – have pivot joints.

I figure it's true, but I just wanted to check.

[freeztar]

Originally Posted by tmaromine

My health teacher made an interesting point today: only apes/monkeys – and thus evolutionarily in turn, us – have pivot joints.

I figure it's true, but I just wanted to check.

Ask your health teacher how a cat is able to turn its head from side to side.
I'm not quite sure that ALL vertebrates have pivot joints, but I can't think of an example of one that does not off the top of my head.

Reference: pivot joint --* Britannica Online Encyclopedia

[tmaromine]

Oh, hm... I was thinking elbow-wise though. Are we the only ones with pivoted elbows ?

[Turtle]

The exoskeleton of insects and other creatures of their type have pivot joints as well. On the hunt for a suitable link.

PS This is interesting, but they don't specifically say the wing join is a 'pivot joint'.

The Physics of. . . Insect Flight | Unusual Organisms | DISCOVER Magazine

Originally Posted by Robert Kunzig

... The first fossils of flying insects date from the Carboniferous Period, roughly 360 million years ago, and they show jointed wings capable of flapping, not rigid ones designed for gliding. ...

[tmaromine]

Oh well ; my teacher mislead me (unless he was talking about another joint). I originally posed this question because I thought it would've been an easy and fast human-evolution display for a friend who thinks/thought that humans are in some mysterious way exempt from it.

Guess I'll just have to find one of the other numerous obviouslies that take some more explaining.

Interesting nonetheless though with insects and perhaps birds !

[freeztar]

Originally Posted by tmaromine

Interesting nonetheless though with insects and perhaps birds !

I'd love to see a link explaining pivot joints in insects, if it exists.

I found some good support for birds though.

Proximal radioulnar articulation - Wikipedia, the free encyclopedia

The proximal radioulnar articulation (superior radioulnar joint) is a trochoid or pivot joint between the circumference of the head of the radius and the ring formed by the radial notch of the ulna and the annular ligament.

The Anatomy of Birds

Like the leg, the bones of the wing are recognisably evolved from a basic plan that can be found in all vertebrates, including mankind. The wing consists of a humerus which at one end is attached to the main thorax via the scapula, and at the other end to both ulna and the radius. Note that like us, birds have two bones in the lower part of the limb. The rest of the wing is composed of modified hand bones.

Although there is no mention of the annular ligament in the second link, it does mention that birds' wings have an ulna and a radius, just like our forearm.

Having seen many birds in flight and the way they are able to pivot their wings as well as flap them gives me the impression that there are at least two, if not more, joints in use. (an eagle swooping down on prey is a good example of the 'pivot' motion)
I haven't found a link explicitly saying that the wings have pivot joints, but I'm convinced they must.

[tmaromine]

What I might've been referring to was this: are primates' elbows special in the sense that only we can pivot our hands without moving our elbow ?

[freeztar]

Originally Posted by tmaromine

What I might've been referring to was this: are primates' elbows special in the sense that only we can pivot our hands without moving our elbow ?

That's a much better question.

I'm going to use some coyote teaching to address the question, hopefully providing you with a much deeper insight than my direct answer would give.

When we hear the word "elbow", we have an immediate connotation with our own bendable elbows. Our elbow is, like all human morphological structures, evolved from an ancestral morphology. For example, the gill slits from our distant ancestors have morphed into some of our orifices such as nose, mouth, and ears.

With that in mind, what is an elbow really? What did it morph from?
(hint: bat anatomy)

[tmaromine]

Originally Posted by freeztar

That's a much better question.

I'm going to use some coyote teaching to address the question, hopefully providing you with a much deeper insight than my direct answer would give.

When we hear the word "elbow", we have an immediate connotation with our own bendable elbows. Our elbow is, like all human morphological structures, evolved from an ancestral morphology. For example, the gill slits from our distant ancestors have morphed into some of our orifices such as nose, mouth, and ears.

With that in mind, what is an elbow really? What did it morph from?
(hint: bat anatomy)

Coyote teaching, eh?

'Really', I'd say the elbow (and knee, though the elbow branches into two bones as opposed to one) is the bendable part of a limb.

What it morphed from is harder for me to answer, because I can only use what seems logical to me, without any real knowledge: over time, a 'single piece' limb became 'doubled', maybe like a leg growing above/below the existing leg. Unless we were water-living first (as you've implied with gill-morphing ?, and which makes sense, considering Earth is waterful), then a hand-like thing formed from its fins, which eventually elongated, which then 'doubled'... The opposite of the whale's case whose link was recently solved, assuming it had 'double-developed legs'.

Though, can I answer my question of whether only primates have this special elbow-thing ? I don't have a degree in evolution, nor the resources or the know for what resources to look for (and Google seems empty on this...).

[freeztar]

Originally Posted by tmaromine

Coyote teaching, eh?

'Really', I'd say the elbow (and knee, though the elbow branches into two bones as opposed to one) is the bendable part of a limb.

What it morphed from is harder for me to answer, because I can only use what seems logical to me, without any real knowledge: over time, a 'single piece' limb became 'doubled', maybe like a leg growing above/below the existing leg. Unless we were water-living first (as you've implied with gill-morphing ?, and which makes sense, considering Earth is waterful), then a hand-like thing formed from its fins, which eventually elongated, which then 'doubled'... The opposite of the whale's case whose link was recently solved, assuming it had 'double-developed legs'.

Though, can I answer my question of whether only primates have this special elbow-thing ? I don't have a degree in evolution, nor the resources or the know for what resources to look for (and Google seems empty on this...).

Here's a couple links that should help you.

Wing Anatomy
Wing Anatomy

Does that help?