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Posts Tagged ‘what the HELL is that?’

An epiphysean Sispyhean task today: solve this mystery that has been bothering me for >15 years. It’s about bird knees. Read on.

Stomach-Churning Rating: 1/10- bones and brief words. Nothing to worry about.

Here is an ostrich. I was interviewing undergrads the other day and looked up to see it, then thought something like: “Oh yeah, that little bit of bone really bothers me. I cannot figure it out.” What little bit of bone?

Right leg, side view, ostrich…

This little bit of bone. Zooming in on that ostrich’s knee:

Who am I? (femur above; tibiotarsus below; “PTE” is the crest of bone with the white arrow on it)

The little bit of bone is not talked about much in the scientific literature on bird knees. But we know it’s there and it is part of the composite bone called the tibiotarsus (ancestral tibia, this bit of bone, and the proximal tarsal [ankle] bones on the other end; the astragalus and calcaneum of earlier dinosaurs).

What is it? We call it something like the proximal tibial epiphysis (PTE for short, here). An epiphysis is an end of a bone that fuses up with the shaft during growth, around the time of skeletal maturity; ultimately ending longitudinal (length-wise) growth of that bone. Mammals almost ubiquitously have them. So do lizards and tuataras. And some fossil relatives. Not much else– except birds, in this particular region (the two ends of the tibiotarsus; also in the foot region; the tarsometatarsus; which also has its share of mysteries such as the hypotarsus; I won’t go there today). You can see the PTE in mostly cartilaginous form if you take apart a chicken drumstick.

This PTE, like other well-behaving epiphyses, fuses with the tibiotarsus in mature birds, forming one bone. But the young ostrich’s knee above shows the PTE nicely; and other living birds show more or less the same thing.

It begs for explanations. I’ve talked about it in a few of my papers. But I’ve always punted on what it really means– does it have anything to do with the patella (they appear at similar times in evolution; we know that much, roughly)? Where does it come from, developmentally? (we sort of know that but more work is needed in different species and in high resolution) When did it evolve? What does it tell us? Why is it there in living birds and almost no other extinct birds/other dinosaurs? Does it have anything to do with why birds, during their evolution, seem to gradually increase the fusion of skeletal elements or ossify new ones (tendons, kneecaps, etc)? Why here and not in the femur or several other long bones of birds? How much do these PTEs vary between (or within) bird species?

This is the challenge in the post’s title. I present to you: solve this puzzle. Developmentally, biomechanically, evolutionarily, genetically, whatever– why does this PTE happen? There are hints– e.g. this paper proposes why growth rates of long bones favour the formation of “secondary centres of ossification” like this. But I’m unable to satisfy myself with any solutions I can find. Maybe you can complete The Bird Knee Challenge?

Have a go at it in the Comments below! There are plenty of papers or even a grant or something involved in sorting out this single mystery; one of the many basic mysteries about animal anatomy.

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Putting my morphologist hat back on today, I had an opportunity to dissect an Elegant-crested tinamou (Eudromia elegans) for the second time in my life. The last time was during my PhD work ~20 years ago. In today’s dissection I was struck by another reminder of how studying anatomy is a lifelong learning experience and sometimes it’s really fun and amazing even when it’s stinky.

Tinamou foot. I did know that tinamous don’t have a hallux; big “perching toe” (1st/”big toe” in us); true of ratites/palaeognaths more generally. Unlike a chicken or many other birds. Just the three main toes (2, 3 and 4) are here.

Stomach-Churning Rating: 7/10; you gotta have guts to learn about intestine-churning stuff.

Tinamous are neat little partridge-like ground birds but they are not close cousins of partridges or guineafowl at all. Their closest cousins are other ratites/palaeognaths such as ostriches and kiwis. And hence they are found in South America, especially Patagonia in Argentina. I’ve seen them there, much to my enjoyment.

Said tinamou.

What struck me today was that, as I delved into the digestive system of this bird, I saw features that were unfamiliar to me even after having dissected many species of birds from many lineages. The intestinal region was very lumpy, with little bud-like pockets full of dense droppings. Furthermore, on separating the tubes of the small and large intestines I realized that most of the intestinal volume itself was caecum (normally a modest side-pocket near the juncture of the small and large intestines). Indeed, that caecum was caeca (plural): it had two massive horns; it was a double-caecum, feeding back into the short rectum and cloaca. Birds have variable caeca and it is typical to see subdivision into two parts, but I’d never seen it to this degree.

Oh why not, here’s the gizzard/stomach showing its grinding pebbles and bits of food, plus the strong outer muscle layers (pink) for driving that grinding. Small intestine heads toward the bottom of the image. Yes, we do need a better dissection light…

I had to question my anatomical knowledge at this point, wondering if I was identifying things incorrectly—did I really screw up somehow and these were other organs, like giant ovaries? But no, they were clearly full of faecal matter; they were digestive organs. I finished the dissection, still puzzled, and hit the literature. Right away, Google-Scholaring for “tinamou caecum” I found the answer, here (free pdf link):

“at least one species (Elegant Crested Tinamou, [Eudromia elegans]), the ceca contain multiple sacculations, resulting in structures that look much like two bunches of fused grapes.”

The caeca in question.

OK buddy, those are the little lumpy buds I saw. Bunches of grapes—exactly.

And later:

“The paired ceca of the Elegant Crested Tinamou are extraordinary and probably unique within Aves (Fig. 3): long and wide (12.5-13.0 X 2.2- 2.5 cm; Wetmore 1926) and internally honeycombed by many small diverticula. These outpocketings gradually diminish in size and organization from the base to the tip of the organ, apically showing a more spiral form of internal ridges like ratite ceca. Externally, the basal diverticula protrude from the ceca as pointed lobes, gradually becoming flatter but still clearly apparent toward the organ’ s tip.”

Whoa! I never knew that! So I happened to be dissecting a bird, fairly common in its homeland, that has a really bizarre and singular form of caeca/ceca! That hit my morphologist sweet-spot so I was very pleased and decided to share with you. It is one of those many examples of times when you quickly go from confusion to illumination as a scientist, emerging with a neat fact about animal biology. And journal articles help you get there!

The bare “brood patch” on the back end of the tinamou’s belly; a nicely hotspot for keeping eggs warm. Perhaps for brooding bad puns, too.

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I hinted at another post in last round, and here I deliver. (The “amazeballs” in the title is a running joke with our Xmas guests here in England, but it applies to the subject of these images, too… which will be the subject of a future blog post involving a dissection of the subject!)

This will end the 2014 round of Mystery Anatomy. What 2015 will bring, I am not sure, but here we have 15 images for my 15th mystery CT post and 2015 around the corner.

I do have a new, fun regular anatomy post idea planned for 2015 but I’ll explain that later.

Stomach-Churning Rating: 2/10; digital images; the cadaver is gutted but I am chuffed.

Mystery Anatomy 2014same rules as before.

Identify (1) the animal shown in the 15 slices, to species level (max. 5 pts), and then the major features (anatomical regions) evident in as many of the 15 slices as you can; details help (max. 5 pts for thoroughness and accuracy). 

Difficulty: No scale, sort of. Otherwise, pretty easy.

Answers will come on New Year’s Day, to ease your hangovers (or encourage vomiting).

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MysteryCT15(15)

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Onward!

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It has been a long time since we had some Mystery Anatomy fun here, so I am cutting loose with a double-barrelled blast of images– dive for cover!

I’m also giving out a Crimbo present as a bigger post, on a special day coming soon, count on that. This is just an advent snack.

Stomach-Churning Rating: 2/10 and 7/10: digital body and glistening, snotty.

Mystery Anatomy 2014same rules as before; remember that the scoreboard has been reset.

Identify (1) the animal shown in the four-panel top images (CT scan/reconstruction), and (2) the DIFFERENT animal (and/or the main central, pink structure) shown in the big, gooey bottom image (Dissection). No special rules. Potential for double points!

And someone will get these, I am sure. This might be the final round of 2014’s Mystery Anatomy game.

Difficulty: Plenty.

Mystery CT 14

Mystery CT 14

Mystery Anatomy 15

Mystery Anatomy 15

Go forth!

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MysteryCT12
Here’s an image that struck me as cool and possibly perplexing. And so we have another Mystery Anatomy post! Brought to you by some free time on my current trip to Gondwanaland.

Stomach-Churning Rating: 1/10; simple CT scan slice… of something.

Mystery Anatomy 2014same rules as before; remember that the scoreboard has been reset.

Identify the animal in the CT slice shown above, as specifically as you can. No special rules.

Difficulty: Plenty.

Begin!

 

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Short and sweet post here; it’s sunny outside and I want to be there BBQing!

I had a buried folder of CT files labelled as a species of fish, but on digging them out and segmenting them I realize it is not what I expected (inner fish or not!), as you will see.

Stomach-Churning Rating: 2/10; simple CT scan of a body.

Mystery Anatomy 2014same rules as before; remember that the scoreboard has been reset.

Identify the animal in the CT scout/pilot image below, as specifically as you can. But… (READ THE SENTENCE BELOW FIRST BEFORE ANSWERING!)

Today’s special rule: Summertime is coming and that means superhero films! Your answer must be in the form of a dialogue between a superhero(ine) and a supervillain(ess)! 

Difficulty: Even I am not 100% sure what this is but I have a decent idea. Not super hard, but not a super good segmentation.

Pow! Bam! Biff! Go forth and conquer! Then invite the Human Torch to your BBQ.

 

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I Can’t Remember Freezermas…
Can’t Tell Dissection from a CT.
Deep down Inside I Feel to Freeze.
These Wonderful Scenes of Anatomy!
Now That the Week Is Through with Me,
I’m Waking up; Ratites I see
And There’s Not Much Left of These:
Nothing remains but bones now

(digested from Metallica’s “One“, in …And Justice For All, the pummeling, slickly produced, huge-sounding, Jason Newsted-bass-playing leviathan of a thematic album (1988). It was all downhill for Metallica after this one, but it was a good year for rock! The song is about a soldier who had traumatic injuries and was left paralyzed, “locked-in” to his own mind. Themes/footage from “Johnny Got His Gun” (1939 book/1971 movie) are interspersed. Did you see this track coming? If so, you’re just as demented as I am; congrats!)

And so another year ends; we’re at the final post of Freezermas 2014: The Concept Album. We had 7 tracks involving leitmotifs of ostriches and cats and 2 vs. 4 legs, and CTs and x-rays, and epic dissections, and disturbing pathologies, and some twisted lyrics that mangled classic albums. There are so many more concept albums I could have touched on- great ones by Rush, Yes, Savatage, Helstar, Mastodon… many more. But I’ll give you a chance to sit in the DJ’s seat in this post!

Stomach-Churning Rating: 6/10. Some internal organs.

Today’s one mystery dissection photo is of two things, and the Mystery Anatomy challenge is to identify both (the 2-part brown thing and the 1-part whitish thing). They are from our friend the ostrich.

Your task is to weave your answer into the lyrics of a song from any concept album (2 lines or more)– you must identify the song, artist and album with your answer so we can figure out the tune. Any genre is OK as long as it is clearly a concept album (music, that is). You have freedom. Use it wisely! As always, bonus points for extra cleverness.

Whazzat?

We’ll let Maytagtallica sing us out:

♫Hold my breath as I wait for points
Oh Please John, blog more?♫

no

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