What we didn't know about male anatomy | Diane Kelly

1,220,380 views ・ 2012-06-05

TED


Please double-click on the English subtitles below to play the video.

00:00
Translator: Timothy Covell Reviewer: Morton Bast
0
0
7000
00:15
When I go to parties,
1
15260
1575
00:16
it doesn't usually take very long
2
16835
1784
00:18
for people to find out
3
18619
1040
00:19
that I'm a scientist and I study sex.
4
19659
3108
00:22
And then I get asked questions.
5
22767
4901
00:27
And the questions usually have a very particular format.
6
27668
3167
00:30
They start with the phrase,
7
30835
1232
00:32
"A friend told me,"
8
32067
1901
00:33
and then they end with the phrase,
9
33968
1900
00:35
"Is this true?"
10
35868
1917
00:37
And most of the time
11
37785
1386
00:39
I'm glad to say that I can answer them,
12
39171
2119
00:41
but sometimes I have to say,
13
41290
1847
00:43
"I'm really sorry,
14
43137
1133
00:44
but I don't know
15
44270
1184
00:45
because I'm not that kind of a doctor."
16
45454
3084
00:48
That is, I'm not a clinician,
17
48538
1916
00:50
I'm a comparative biologist who studies anatomy.
18
50454
3191
00:53
And my job is to look at lots of different species of animals
19
53645
2933
00:56
and try to figure out how their tissues and organs work
20
56578
3317
00:59
when everything's going right,
21
59895
1501
01:01
rather than trying to figure out
22
61396
1618
01:03
how to fix things when they go wrong,
23
63014
1583
01:04
like so many of you.
24
64597
1201
01:05
And what I do is I look for similarities and differences
25
65798
2399
01:08
in the solutions that they've evolved
26
68197
2267
01:10
for fundamental biological problems.
27
70464
1584
01:12
So today I'm here to argue
28
72048
1849
01:13
that this is not at all
29
73897
3866
01:17
an esoteric Ivory Tower activity
30
77763
1901
01:19
that we find at our universities,
31
79664
1317
01:20
but that broad study
32
80981
1983
01:22
across species, tissue types and organ systems
33
82964
2952
01:25
can produce insights
34
85916
1635
01:27
that have direct implications for human health.
35
87551
3384
01:30
And this is true both of my recent project
36
90935
2498
01:33
on sex differences in the brain,
37
93433
1724
01:35
and my more mature work
38
95157
1919
01:37
on the anatomy and function of penises.
39
97076
2834
01:39
And now you know why I'm fun at parties.
40
99910
2630
01:42
(Laughter)
41
102540
968
01:43
So today I'm going to give you an example
42
103508
2283
01:45
drawn from my penis study
43
105791
1717
01:47
to show you how knowledge
44
107508
1617
01:49
drawn from studies of one organ system
45
109125
1767
01:50
provided insights into a very different one.
46
110892
2981
01:53
Now I'm sure as everyone in the audience already knows --
47
113873
3018
01:56
I did have to explain it to my nine-year-old late last week --
48
116891
3516
02:00
penises are structures that transfer sperm
49
120407
3751
02:04
from one individual to another.
50
124158
1300
02:05
And the slide behind me
51
125458
1500
02:06
barely scratches the surface
52
126958
1733
02:08
of how widespread they are in animals.
53
128691
1965
02:10
There's an enormous amount of anatomical variation.
54
130656
1985
02:12
You find muscular tubes, modified legs, modified fins,
55
132641
3874
02:16
as well as the mammalian fleshy, inflatable cylinder
56
136515
3846
02:20
that we're all familiar with --
57
140361
1635
02:21
or at least half of you are.
58
141996
2282
02:24
(Laughter)
59
144278
2401
02:26
And I think we see this tremendous variation
60
146679
2738
02:29
because it's a really effective solution
61
149417
3151
02:32
to a very basic biological problem,
62
152568
2166
02:34
and that is getting sperm in a position
63
154734
2483
02:37
to meet up with eggs and form zygotes.
64
157217
2552
02:39
Now the penis isn't actually required for internal fertiliztion,
65
159769
3949
02:43
but when internal fertilization evolves,
66
163718
2466
02:46
penises often follow.
67
166184
2000
02:48
And the question I get when I start talking about this most often is,
68
168184
4417
02:52
"What made you interested in this subject?"
69
172601
2916
02:55
And the answer is skeletons.
70
175517
3950
02:59
You wouldn't think that skeletons and penises
71
179467
2567
03:02
have very much to do with one another.
72
182034
1851
03:03
And that's because we tend to think of skeletons
73
183885
2132
03:06
as stiff lever systems
74
186017
1650
03:07
that produce speed or power.
75
187667
1683
03:09
And my first forays into biological research,
76
189350
3567
03:12
doing dinosaur paleontology as an undergraduate,
77
192917
2818
03:15
were really squarely in that realm.
78
195735
1551
03:17
But when I went to graduate school to study biomechanics,
79
197286
3117
03:20
I really wanted to find a dissertation project
80
200403
2465
03:22
that would expand our knowledge of skeletal function.
81
202868
2899
03:25
I tried a bunch of different stuff.
82
205767
1802
03:27
A lot of it didn't pan out.
83
207569
1648
03:29
But then one day I started thinking
84
209217
1834
03:31
about the mammalian penis.
85
211051
1782
03:32
And it's really an odd sort of structure.
86
212833
4018
03:36
Before it can be used for internal fertilization,
87
216851
2817
03:39
its mechanical behavior has to change
88
219668
1483
03:41
in a really dramatic fashion.
89
221151
1717
03:42
Most of the time it's a flexible organ.
90
222868
2598
03:45
It's easy to bend.
91
225466
1284
03:46
But before it's brought into use
92
226750
1994
03:48
during copulation
93
228744
1218
03:49
it has to become rigid,
94
229962
1758
03:51
it has to become difficult to bend.
95
231720
2015
03:53
And moreover, it has to work.
96
233735
2017
03:55
A reproductive system that fails to function
97
235752
2750
03:58
produces an individual that has no offspring,
98
238502
3315
04:01
and that individual is then kicked out of the gene pool.
99
241817
3171
04:04
And so I thought, "Here's a problem
100
244988
2461
04:07
that just cries out for a skeletal system --
101
247449
3248
04:10
not one like this one,
102
250697
3212
04:13
but one like this one --
103
253909
3057
04:16
because, functionally,
104
256966
2417
04:19
a skeleton is any system
105
259383
1567
04:20
that supports tissue and transmits forces.
106
260950
3032
04:23
And I already knew that animals like this earthworm,
107
263982
2350
04:26
indeed most animals,
108
266332
1446
04:27
don't support their tissues
109
267778
1293
04:29
by draping them over bones.
110
269071
1794
04:30
Instead they're more like reinforced water balloons.
111
270865
2833
04:33
They use a skeleton that we call a hydrostatic skeleton.
112
273698
3867
04:37
And a hydrostatic skeleton
113
277565
2066
04:39
uses two elements.
114
279631
1918
04:41
The skeletal support comes from an interaction
115
281549
2150
04:43
between a pressurized fluid
116
283699
1774
04:45
and a surrounding wall of tissue
117
285473
1606
04:47
that's held in tension and reinforced with fibrous proteins.
118
287079
4471
04:51
And the interaction is crucial.
119
291550
2248
04:53
Without both elements you have no support.
120
293798
3368
04:57
If you have fluid
121
297166
1282
04:58
with no wall to surround it
122
298448
2034
05:00
and keep pressure up,
123
300482
1434
05:01
you have a puddle.
124
301916
1904
05:03
And if you have just the wall
125
303820
2100
05:05
with no fluid inside of it to put the wall in tension,
126
305920
1734
05:07
you've got a little wet rag.
127
307654
1950
05:09
When you look at a penis in cross section,
128
309604
2632
05:12
it has a lot of the hallmarks
129
312236
2433
05:14
of a hydrostatic skeleton.
130
314669
2050
05:16
It has a central space
131
316719
1509
05:18
of spongy erectile tissue
132
318228
1520
05:19
that fills with fluid -- in this case blood --
133
319748
2578
05:22
surrounded by a wall of tissue
134
322326
2399
05:24
that's rich in a stiff structural protein called collagen.
135
324725
3851
05:28
But at the time when I started this project,
136
328576
2500
05:31
the best explanation I could find for penal erection
137
331076
3201
05:34
was that the wall surrounded these spongy tissues,
138
334277
4284
05:38
and the spongy tissues filled with blood
139
338561
1699
05:40
and pressure rose and voila! it became erect.
140
340260
3268
05:43
And that explained to me expansion --
141
343528
3965
05:47
made sense: more fluid, you get tissues that expand --
142
347493
3567
05:51
but it didn't actually explain erection.
143
351060
3017
05:54
Because there was no mechanism in this explanation
144
354077
3891
05:57
for making this structure hard to bend.
145
357968
2967
06:00
And no one had systematically looked at the wall tissue.
146
360935
2716
06:03
So I thought, wall tissue's important in skeletons.
147
363651
2602
06:06
It has to be part of the explanation.
148
366253
2366
06:08
And this was the point
149
368619
2535
06:11
at which my graduate adviser said,
150
371154
2597
06:13
"Whoa! Hold on. Slow down."
151
373751
3383
06:17
Because after about six months of me talking about this,
152
377134
3368
06:20
I think he finally figured out
153
380502
1316
06:21
that I was really serious about the penis thing.
154
381818
3049
06:24
(Laughter)
155
384867
3047
06:27
So he sat me down, and he warned me.
156
387914
2049
06:29
He was like, "Be careful going down this path.
157
389963
2176
06:32
I'm not sure this project's going to pan out."
158
392139
2767
06:34
Because he was afraid I was walking into a trap.
159
394906
2532
06:37
I was taking on a socially embarrassing question
160
397438
4817
06:42
with an answer that he thought
161
402255
2335
06:44
might not be particularly interesting.
162
404590
2382
06:46
And that was because
163
406972
1533
06:48
every hydrostatic skeleton
164
408505
1518
06:50
that we had found in nature up to that point
165
410023
2068
06:52
had the same basic elements.
166
412091
1797
06:53
It had the central fluid,
167
413888
1217
06:55
it had the surrounding wall,
168
415105
1800
06:56
and the reinforcing fibers in the wall
169
416905
3136
07:00
were arranged in crossed helices
170
420041
2418
07:02
around the long axis of the skeleton.
171
422459
2057
07:04
So the image behind me
172
424516
1321
07:05
shows a piece of tissue
173
425837
1629
07:07
in one of these cross helical skeletons
174
427466
2025
07:09
cut so that you're looking at the surface of the wall.
175
429491
2533
07:12
The arrow shows you the long axis.
176
432024
1718
07:13
And you can see two layers of fibers,
177
433742
1850
07:15
one in blue and one in yellow,
178
435592
1701
07:17
arranged in left-handed and right-handed angles.
179
437293
2798
07:20
And if you weren't just looking at a little section of the fibers,
180
440091
2249
07:22
those fibers would be going in helices
181
442340
2701
07:25
around the long axis of the skeleton --
182
445041
1750
07:26
something like a Chinese finger trap,
183
446791
2133
07:28
where you stick your fingers in and they get stuck.
184
448924
1901
07:30
And these skeletons have a particular set of behaviors,
185
450825
3083
07:33
which I'm going to demonstrate in a film.
186
453908
2032
07:35
It's a model skeleton
187
455940
1151
07:37
that I made out of a piece of cloth
188
457091
2183
07:39
that I wrapped around an inflated balloon.
189
459274
2553
07:41
The cloth's cut on the bias.
190
461827
1698
07:43
So you can see that the fibers wrap in helices,
191
463525
2749
07:46
and those fibers can reorient as the skeleton moves,
192
466274
4312
07:50
which means the skeleton's flexible.
193
470586
1429
07:52
It lengthens, shortens and bends really easily
194
472015
2473
07:54
in response to internal or external forces.
195
474488
3547
07:58
Now my adviser's concern
196
478035
1296
07:59
was what if the penile wall tissue
197
479331
2366
08:01
is just the same as any other hydrostatic skeleton.
198
481697
1674
08:03
What are you going to contribute?
199
483371
1927
08:05
What new thing are you contributing
200
485298
1467
08:06
to our knowledge of biology?
201
486765
1648
08:08
And I thought, "Yeah, he does have a really good point here."
202
488413
3418
08:11
So I spent a long, long time thinking about it.
203
491831
1750
08:13
And one thing kept bothering me,
204
493581
2134
08:15
and that's, when they're functioning,
205
495715
2450
08:18
penises don't wiggle.
206
498165
1933
08:20
(Laughter)
207
500098
2339
08:22
So something interesting had to be going on.
208
502437
2901
08:25
So I went ahead, collected wall tissue,
209
505338
3301
08:28
prepared it so it was erect,
210
508639
1599
08:30
sectioned it, put it on slides
211
510238
2199
08:32
and then stuck it under the microscope to have a look,
212
512437
2652
08:35
fully expecting to see crossed helices of collagen of some variety.
213
515089
5036
08:40
But instead I saw this.
214
520125
2398
08:42
There's an outer layer and an inner layer.
215
522523
3001
08:45
The arrow shows you the long axis of the skeleton.
216
525524
2550
08:48
I was really surprised at this.
217
528074
2569
08:50
Everyone I showed it
218
530643
945
08:51
was really surprised at this.
219
531588
1200
08:52
Why was everyone surprised at this?
220
532788
1537
08:54
That's because we knew theoretically
221
534325
2984
08:57
that there was another way
222
537309
2815
09:00
of arranging fibers in a hydrostatic skeleton,
223
540124
3034
09:03
and that was with fibers at zero degrees
224
543158
2271
09:05
and 90 degrees to the long axis of the structure.
225
545429
3866
09:09
The thing is, no one had ever seen it before in nature.
226
549295
3562
09:12
And now I was looking at one.
227
552857
2700
09:15
Those fibers in that particular orientation
228
555557
2734
09:18
give the skeleton a very, very different behavior.
229
558291
3215
09:21
I'm going to show a model
230
561506
1185
09:22
made out of exactly the same materials.
231
562691
1945
09:24
So it'll be made of the same cotton cloth,
232
564636
2058
09:26
same balloon, same internal pressure.
233
566694
3289
09:29
But the only difference
234
569983
2467
09:32
is that the fibers are arranged differently.
235
572450
2382
09:34
And you'll see that, unlike the cross helical model,
236
574832
2651
09:37
this model resists extension and contraction
237
577483
2950
09:40
and resists bending.
238
580433
1451
09:41
Now what that tells us
239
581884
1034
09:42
is that wall tissues are doing so much more
240
582918
2096
09:45
than just covering the vascular tissues.
241
585014
2503
09:47
They're an integral part of the penile skeleton.
242
587517
3494
09:51
If the wall around the erectile tissue wasn't there,
243
591011
2537
09:53
if it wasn't reinforced in this way,
244
593548
2165
09:55
the shape would change,
245
595713
1152
09:56
but the inflated penis would not resist bending,
246
596865
2384
09:59
and erection simply wouldn't work.
247
599249
2047
10:01
It's an observation with obvious medical applications
248
601296
2601
10:03
in humans as well,
249
603897
1782
10:05
but it's also relevant in a broad sense, I think,
250
605679
2935
10:08
to the design of prosthetics, soft robots,
251
608614
2432
10:11
basically anything
252
611046
1067
10:12
where changes of shape and stiffness are important.
253
612113
3318
10:15
So to sum up:
254
615431
1748
10:17
Twenty years ago,
255
617179
1217
10:18
I had a college adviser tell me,
256
618396
1750
10:20
when I went to the college and said,
257
620146
2051
10:22
"I'm kind of interested in anatomy,"
258
622197
1149
10:23
they said, "Anatomy's a dead science."
259
623346
1884
10:25
He couldn't have been more wrong.
260
625230
2617
10:27
I really believe that we still have a lot to learn
261
627847
2733
10:30
about the normal structure and function of our bodies.
262
630580
3133
10:33
Not just about its genetics and molecular biology,
263
633713
2814
10:36
but up here in the meat end of the scale.
264
636527
3399
10:39
We've got limits on our time.
265
639926
1435
10:41
We often focus on one disease,
266
641361
2265
10:43
one model, one problem,
267
643626
1184
10:44
but my experience suggests
268
644810
1574
10:46
that we should take the time
269
646384
1778
10:48
to apply ideas broadly between systems
270
648162
2565
10:50
and just see where it takes us.
271
650727
1874
10:52
After all, if ideas about invertebrate skeletons
272
652601
3600
10:56
can give us insights
273
656201
1466
10:57
about mammalian reproductive systems,
274
657667
2085
10:59
there could be lots of other wild and productive connections
275
659752
4049
11:03
lurking out there just waiting to be found.
276
663801
2449
11:06
Thank you.
277
666250
1852
11:08
(Applause)
278
668102
3388
About this website

This site will introduce you to YouTube videos that are useful for learning English. You will see English lessons taught by top-notch teachers from around the world. Double-click on the English subtitles displayed on each video page to play the video from there. The subtitles scroll in sync with the video playback. If you have any comments or requests, please contact us using this contact form.

https://forms.gle/WvT1wiN1qDtmnspy7