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]

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. :rolleyes:

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'. :rolleyes:

 

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

... 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]

:rolleyes: 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]

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]

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. :hihi:

 

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]

That's a much better question. :hihi:

 

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]

Coyote teaching, eh? :D

 

'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...). :D

 

Here's a couple links that should help you.

 

Wing Anatomy

Wing Anatomy

 

Does that help? :D

[Dracontes]

From a preliminary Google search, "trochoid joint" amphibian (second hit), it seems that only a few mammals have it but most amphibians and reptiles do, probably for their low slung mode of locomotion requiring extra elbow joint mobility.

 

I found some good support for birds though.

 

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.

 

Actually, no. Birds and their dinosaur ancestors could not pronate or supinate their hands being only able to move the distal arm from the elbow pretty close to a single plane, which is not parallel to the humerus. This is probably due to the fact that crocodile and birds' last common ancestor had its distal arm articulations locked so fingers faced forward when the hand was on the ground when walking about (don't quote me on this phrase, though). What birds have is a very mobile shoulder joint allowing them to overcome this handicap.

 

'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.

 

Erm...! The lower leg bones are the tibia and the fibula.

[freeztar]

From a preliminary Google search, "trochoid joint" amphibian (second hit), it seems that only a few mammals have it but most amphibians and reptiles do, probably for their low slung mode of locomotion requiring extra elbow joint mobility.

 

I'm very dubious about your claim, how about giving a link to that source.

 

Actually, no. Birds and their dinosaur ancestors could not pronate or supinate their hands being only able to move the distal arm from the elbow pretty close to a single plane, which is not parallel to the humerus. This is probably due to the fact that crocodile and birds' last common ancestor had its distal arm articulations locked so fingers faced forward when the hand was on the ground when walking about (don't quote me on this phrase, though). What birds have is a very mobile shoulder joint allowing them to overcome this handicap.

 

Again, do you have a source for this info?

What type of joint do you suppose allows an owl to spin its head around?

 

Erm...! The lower leg bones are the tibia and the fibula.

 

??

[Dracontes]

I'm very dubious about your claim, how about giving a link to that source.

 

I'm quite dubious myself. I did, but here it is again: "trochoid joint" amphibian (actually third hit :hihi:). The third hit I'm mentioning is a paper I can't access of whose abstract I can see snippets on the Google results page:

 

... articulations allow for axial rotation, corresponding to a trochoid joint. .... structure typically found in amphibians, reptiles, and some mammals. ...

It is disjointed, yes, but since the paper is:

 

Keir A.B. Fowler MD and Christine B. Chung MD, "Normal MR Imaging Anatomy of the Elbow",

Magnetic Resonance Imaging Clinics of North America

2004;12:191–206.

 

I'm willing to bet on the connection, or maybe I'm just plain wrong :hihi:

 

If you had noticed, you'd know I couldn't post a direct link besides wiki and google tags because I was under the 10 post threshold to post links on these here forums.

 

Again, do you have a source for this info?

 

Again the whole "no hotlinking" thing... Try the Archives of the DINOSAUR Mailing List and do a search on theropod hand orientation, 'raptor hands, and hand pronation in dinosaurs and the like. But here's a pertinent quote if you don't feel like it (which is probably what I should have done first):

 

Senter, P., & J. H. Robins. 2005. Range of motion in the forelimb of the

theropod dinosaur Acrocanthosaurus atokensis, and implications for predatory

behaviour. Journal of Zoology 266(3): 307-318.

 

"Casts of forelimb elements of the Cretaceous theropod dinosaur Acrocanthosaurus atokensis were manually manipulated to determine range of motion and infer function. It was found that the humerus can swing posteriorly into a horizontal position but can neither swing laterally to glenoid height nor anteriorly much beyond the glenoid. The forearm can approach but not achieve full extension and right-angle flexion.

Pronation and supination are precluded by immobility of the radius relative to the ulna.

Motion also seems to be restricted at the wrist. The palm faces medially, and digital movement is subtransverse. All three digits are capable of extreme hyper-extension. Digits I and II converge during flexion. Only digit III can be abducted or adducted. The limited anterior range of brachial motion infers that Acrocanthosaurus first apprehended prey orally, using the forelimb afterwards to secure its grip or deliver fatal blows. Acrocanthosaurus could only manually grasp prey that was beneath its chest, towards which it may have used its mouth to move prey. Struggling prey would have impaled itself further upon the permanently and strongly flexed first ungual. The range of motion in the forelimb of Acrocanthosaurus resembles that of Herrerasaurus and Dilophosaurus, and exceeds that of Tyrannosaurus. Acrocanthosaurus exhibits a greater manual range of motion than ornithomimid and deinonychosaurian coelurosaurs, but less at the shoulder and elbow. Coelurosaurian theropods exhibit reduced digital flexion and hyper-extension, which suggests a change in the use of the manus in coelurosaurs."

 

What type of joint do you suppose allows an owl to spin its head around?

 

Man, I'm talking about bird elbows here; birds can do whatever they wish with their cervical pivot joints ;)

 

??

 

Just enlightening a flagrant oversight in that person's anatomical knowledge :)

[freeztar]

I'm quite dubious myself. I did, but here it is again: "trochoid joint" amphibian (actually third hit :hihi:). The third hit I'm mentioning is a paper I can't access of whose abstract I can see snippets on the Google results page:

 

It is disjointed, yes, but since the paper is:

 

I'm willing to bet on the connection, or maybe I'm just plain wrong :hihi:

I'm not a betting man myself. :)

If you had noticed, you'd know I couldn't post a direct link besides wiki and google tags because I was under the 10 post threshold to post links on these here forums.

I noticed.

 

Again the whole "no hotlinking" thing... Try the Archives of the DINOSAUR Mailing List and do a search on theropod hand orientation, 'raptor hands, and hand pronation in dinosaurs and the like. But here's a pertinent quote if you don't feel like it (which is probably what I should have done first):

Good info (quoted text). Unfortunately it only discusses one type of dinosaur. It's also important to note that MANY anatomical changes occurred between dinosaurs and modern day birds.

 

Man, I'm talking about bird elbows here; birds can do whatever they wish with their cervical pivot joints ;)

Take a look at this link I posted before:

Wing Anatomy

Take note that the word "elbow" is in quotes.

I'll try to look for a better link later on.

 

The plot thickens...

[tmaromine]

With the bones thing, I said that it was just one bone so Dracontes corrected me. :hihi:

 

With your two links freeztar, I found that bird's wings have the two bones we do: radius and ulna. I noticed the "elbow", but don't know quite what to make of it. If what Dracontes was saying, and that which you're both dubious about, is correct, then birds have the same bones as us, but not the same movementability at the "elbow".

From the second one, I got that a bat's wing is similar to the human hand and arm, with some major elongations... :hihi:

[freeztar]

With the bones thing, I said that it was just one bone so Dracontes corrected me. :)

 

Ah, ok, I see now.

With your two links freeztar, I found that bird's wings have the two bones we do: radius and ulna. I noticed the "elbow", but don't know quite what to make of it. If what Dracontes was saying, and that which you're both dubious about, is correct, then birds have the same bones as us, but not the same movementability at the "elbow".

 

I am dubious about Dracontes claim that only a few mammals have elbows with pivot joints. It may very well be the case, but neither of us have been able to find a good supporting link yet.

 

Pivotal "elbow" joints in birds are still up in the air right now. (excuse the pun :hihi: )

From the second one, I got that a bat's wing is similar to the human hand and arm, with some major elongations... :hihi:

 

Correct.

[freeztar]

Here's a link to an abstract of a study that examined proximal radio-ulnar articulation in dogs:

http://www.cababstractsplus.org/google/abstract.asp?AcNo=20053083403

 

Here's a link that shows that horses have the connection, but lack movement (which is making me think that my assessment of the dog link above is innaccurate):

Anatomy of the Horse: An Illustrated ... - Google Book Search

 

Cats apparently have the joint, but no mention of movement in this link:

Anatomy of the Cat - Google Book Search

 

But there is mention of pronation at this link:

Cat Muscles 13

 

The more I think about it...

Any animal that can turn it's paw/foot inward would have to have a pivot joint. Yes/no?

 

-squirrels

-raccoons

-bears

-etc...