1
00:00:00,766 --> 00:00:02,592
- [Voiceover] We've been
talking about all these bones,

2
00:00:02,592 --> 00:00:04,146
but we need to talk about joints.

3
00:00:04,146 --> 00:00:06,940
How do the bones come together?

4
00:00:06,940 --> 00:00:08,326
Now there's gonna be a total of

5
00:00:08,326 --> 00:00:11,826
three different classifications of joints.

6
00:00:12,807 --> 00:00:15,158
Now these joints, or articulations,

7
00:00:15,158 --> 00:00:18,519
are classified based
on degree of movement,

8
00:00:18,519 --> 00:00:20,631
based on what they're made of.

9
00:00:20,631 --> 00:00:23,714
So first off, we have fibrous joints.

10
00:00:24,661 --> 00:00:27,796
Like the name implies,
they're made of fiber.

11
00:00:27,796 --> 00:00:29,379
They're immovable, they're not meant

12
00:00:29,379 --> 00:00:31,764
to move around or do anything.

13
00:00:31,764 --> 00:00:35,044
Fontanels, those are
those baby soft spots,

14
00:00:35,044 --> 00:00:37,932
that's how the bones
are being held together.

15
00:00:37,932 --> 00:00:41,182
Those are an example of fibrous joints.

16
00:00:42,921 --> 00:00:45,281
Cartilaginous joints.

17
00:00:45,281 --> 00:00:48,003
Now these have a little bit of movement,

18
00:00:48,003 --> 00:00:49,975
but they're not really meant to move much.

19
00:00:49,975 --> 00:00:51,617
I mean, a little bit of a shimmer here,

20
00:00:51,617 --> 00:00:53,367
a little shade there,

21
00:00:54,676 --> 00:00:58,843
but all this movement can add
up to quite a large amount.

22
00:01:00,767 --> 00:01:04,360
Where the cartilage is
joining the vertebrae

23
00:01:04,360 --> 00:01:08,531
of the vertebral column, each
one can move a little bit

24
00:01:08,531 --> 00:01:11,745
because of a cartilaginous joint,

25
00:01:11,745 --> 00:01:13,916
but add all of those together,

26
00:01:13,916 --> 00:01:16,583
creates quite a bit of movement.

27
00:01:18,093 --> 00:01:19,343
Synovial joint.

28
00:01:20,248 --> 00:01:22,301
Well, synovial joints are by far

29
00:01:22,301 --> 00:01:24,388
the most common in the body.

30
00:01:24,388 --> 00:01:25,781
They're freely movable.

31
00:01:25,781 --> 00:01:28,781
They can move on any plane, any direction.

32
00:01:28,781 --> 00:01:32,443
The only limiting factor is going to be

33
00:01:32,443 --> 00:01:37,301
the flexibility in the joint,
and how the bones are aligned.

34
00:01:37,301 --> 00:01:40,181
So for example, a synovial joint

35
00:01:40,181 --> 00:01:43,490
could be your shoulder joint,
could be your hip joint,

36
00:01:43,490 --> 00:01:46,740
your elbow, the joints in your fingers.

37
00:01:47,683 --> 00:01:51,266
So lots of things could
be synovial joints.

38
00:01:53,487 --> 00:01:55,762
On the left, we have a little deeper view.

39
00:01:55,762 --> 00:01:58,085
On the right, we have a
little more superficial view,

40
00:01:58,085 --> 00:02:00,189
more towards the top.

41
00:02:00,189 --> 00:02:02,447
You see on the left how
they have the patella

42
00:02:02,447 --> 00:02:04,824
actually pulled off.

43
00:02:04,824 --> 00:02:09,489
The ligament is intact,
going from bone, patella,

44
00:02:09,489 --> 00:02:10,739
to bone, tibia.

45
00:02:12,113 --> 00:02:16,280
What is being cut and
reflected back is the tendon,

46
00:02:17,589 --> 00:02:19,256
from bone to muscle.

47
00:02:21,605 --> 00:02:24,821
So now in this case you can
see how all those ligaments

48
00:02:24,821 --> 00:02:29,564
are helping to anchor and
keep the knee in place.

49
00:02:29,564 --> 00:02:31,872
There's ligaments on both
the right and left side.

50
00:02:31,872 --> 00:02:34,975
We have ligaments inside,
for a total of four,

51
00:02:34,975 --> 00:02:37,142
helping to anchor it down.

52
00:02:38,040 --> 00:02:41,888
So we have the left hand
side, all ligaments,

53
00:02:41,888 --> 00:02:44,280
right hand side, you can see the muscle.

54
00:02:44,280 --> 00:02:46,248
You can see where the tendon is,

55
00:02:46,248 --> 00:02:49,248
you can still some of the ligaments,

56
00:02:49,248 --> 00:02:52,715
but if you notice that
kind of purplish haze,

57
00:02:52,715 --> 00:02:56,520
that purplish haze is the joint capsule.

58
00:02:56,520 --> 00:02:58,552
It's what keeps all
the fluid in the joint,

59
00:02:58,552 --> 00:03:02,865
what keeps it healthy,
keeps it functional.

60
00:03:02,865 --> 00:03:05,792
So here's that joint
capsule, what it's made of.

61
00:03:05,792 --> 00:03:09,189
Joint capsule is made
of the synovial membrane

62
00:03:09,189 --> 00:03:13,356
and the hyaline cartilage
found at the end of long bones.

63
00:03:15,340 --> 00:03:17,514
The purpose of the synovial membrane

64
00:03:17,514 --> 00:03:20,514
is to secrete the synovial fluid.

65
00:03:20,514 --> 00:03:24,252
Synovial fluid can act as a lubricant.

66
00:03:24,252 --> 00:03:27,328
It can also help to nourish a little bit.

67
00:03:27,328 --> 00:03:31,527
We know that hyaline cartilage
is meant for insulation,

68
00:03:31,527 --> 00:03:36,020
and cushioning, for those
nice shock absorbers.

69
00:03:36,020 --> 00:03:39,384
The bones come together, it
helps to cushion the blow

70
00:03:39,384 --> 00:03:42,634
of both bones smacking into each other.

71
00:03:44,715 --> 00:03:48,255
Now, we have a couple different
types of synovial joints.

72
00:03:48,255 --> 00:03:51,612
First to point out is the hinge joint.

73
00:03:51,612 --> 00:03:54,112
Second, ball and socket joint.

74
00:03:55,298 --> 00:03:56,318
Well, the names are kind of helping

75
00:03:56,318 --> 00:03:59,304
to hopefully imply a little bit.

76
00:03:59,304 --> 00:04:00,637
Ball and socket.

77
00:04:01,846 --> 00:04:04,197
Well, that's your shoulder
joint, for instance.

78
00:04:04,197 --> 00:04:06,067
Your hip joint.

79
00:04:06,067 --> 00:04:10,937
You have a round end on
the bone. That's the ball.

80
00:04:10,937 --> 00:04:14,356
The socket is where it goes into.

81
00:04:14,356 --> 00:04:18,437
So in the case of the hip,
there's that indent on the coxal.

82
00:04:18,437 --> 00:04:19,837
Case of the shoulder,

83
00:04:19,837 --> 00:04:23,781
there's a very shallow
indent on the shoulder.

84
00:04:23,781 --> 00:04:27,061
So that's the ball and socket.

85
00:04:27,061 --> 00:04:28,942
Hinge, just think of a door.

86
00:04:28,942 --> 00:04:31,717
That's the equivalent of a hinge joint.

87
00:04:31,717 --> 00:04:35,119
Tendons, well we know
ligaments are bone to bone,

88
00:04:35,119 --> 00:04:37,369
tendons are muscle to bone.

89
00:04:38,613 --> 00:04:42,788
So put all these joints and bones to work,

90
00:04:42,788 --> 00:04:44,854
we have to see how they interact.

91
00:04:44,854 --> 00:04:47,559
Now what do you muscle
to cause the interaction?

92
00:04:47,559 --> 00:04:50,357
Muscle pull against the bone.

93
00:04:50,357 --> 00:04:53,690
We have the term abduction, a-b-duction.

94
00:04:55,193 --> 00:04:57,443
And adduction, a-d-duction.

95
00:05:01,010 --> 00:05:03,674
So look at the figure on
the left, you see that,

96
00:05:03,674 --> 00:05:05,995
sorry, the left arm, I should say.

97
00:05:05,995 --> 00:05:10,162
The abduction is moving
the arm away from midline,

98
00:05:11,672 --> 00:05:15,755
while adduction, a-d-duction,
is bringing it back

99
00:05:16,705 --> 00:05:19,126
towards the midline.

100
00:05:19,126 --> 00:05:21,489
So we're showing that abduction,

101
00:05:21,489 --> 00:05:25,045
doesn't matter if it's the
arm, the leg, the wrist,

102
00:05:25,045 --> 00:05:29,831
abduction, a-b-duction
is always carrying things

103
00:05:29,831 --> 00:05:31,664
away from the midline,

104
00:05:33,093 --> 00:05:35,010
while adduction, a-d-d,

105
00:05:37,800 --> 00:05:42,562
seems to always be adding
things to the midline.

106
00:05:42,562 --> 00:05:45,530
So you're a-d-d, you're adding it.

107
00:05:45,530 --> 00:05:49,697
Adding, or adduction, is
bringing the arm back to midline,

108
00:05:50,749 --> 00:05:52,807
bringing the leg back to midline,

109
00:05:52,807 --> 00:05:57,286
even bringing the wrist
back towards the midline.

110
00:05:57,286 --> 00:06:00,369
So the terms abduction and adduction.

111
00:06:03,873 --> 00:06:05,443
Now we have the difference between

112
00:06:05,443 --> 00:06:07,693
circumduction and rotation.

113
00:06:09,332 --> 00:06:12,582
The entire arm can go through rotation.

114
00:06:13,548 --> 00:06:16,241
Now it's not the twisting at the elbow,

115
00:06:16,241 --> 00:06:20,408
but the entire arm at the
shoulder can twist in place.

116
00:06:21,251 --> 00:06:23,242
It's not gonna do a full 180,

117
00:06:23,242 --> 00:06:25,483
but should totally be 20-30 degrees.

118
00:06:25,483 --> 00:06:27,561
Depends on the person.

119
00:06:27,561 --> 00:06:31,478
But still, it's rotating
around a central axis.

120
00:06:35,002 --> 00:06:39,169
Now, the term circumduction,
the actual limb isn't rotating,

121
00:06:41,232 --> 00:06:46,229
what's happening is, the
limb is working in a circle,

122
00:06:46,229 --> 00:06:49,226
it's creating this kind of cone shape.

123
00:06:49,226 --> 00:06:51,535
You can do it with your arm and your leg.

124
00:06:51,535 --> 00:06:54,201
Imagine your arm is facing forward,

125
00:06:54,201 --> 00:06:56,250
you have your palm facing forward.

126
00:06:56,250 --> 00:06:58,624
Then just keep the palm forward,

127
00:06:58,624 --> 00:07:02,890
and you can actually bring
the arm into small circles.

128
00:07:02,890 --> 00:07:05,339
That's circumduction,

129
00:07:05,339 --> 00:07:09,172
moving the actual arm in small circles,

130
00:07:09,172 --> 00:07:12,770
allowing for movement of
arm and the leg together,

131
00:07:12,770 --> 00:07:14,437
or make it separate.

132
00:07:16,956 --> 00:07:18,789
Flexion and extension.

133
00:07:19,923 --> 00:07:21,692
Those are the two common ones,

134
00:07:21,692 --> 00:07:23,296
but you gotta also remember
that there's something

135
00:07:23,296 --> 00:07:25,879
that's called a hyperextension.

136
00:07:26,773 --> 00:07:29,903
So let's start off with the
first term, flexion, top left.

137
00:07:29,903 --> 00:07:34,070
Flexion is meant to decrease
the angle of a joint.

138
00:07:36,010 --> 00:07:37,885
So look at your elbow.

139
00:07:37,885 --> 00:07:41,936
If you start to bring your arm
in, like bend at the elbow,

140
00:07:41,936 --> 00:07:43,950
so bring it close to your body,

141
00:07:43,950 --> 00:07:47,132
what's happening to the
angle within that joint?

142
00:07:47,132 --> 00:07:49,882
It's getting smaller and smaller.

143
00:07:51,548 --> 00:07:54,215
Well, extension is the opposite.

144
00:07:55,254 --> 00:07:58,765
In extension, you're
increasing the joint angle

145
00:07:58,765 --> 00:08:00,265
back to normality.

146
00:08:03,293 --> 00:08:07,931
But one slight difference
now is hyperextension.

147
00:08:07,931 --> 00:08:12,098
In the case of hyperextension,
hyper means too far.

148
00:08:14,126 --> 00:08:16,319
So in a hyperextension,

149
00:08:16,319 --> 00:08:20,486
sometimes it can become very
problematic, very dangerous,

150
00:08:21,666 --> 00:08:25,498
because you might not
even realize it's injured.

151
00:08:25,498 --> 00:08:28,825
But more often than not,
majority of hyperextensions,

152
00:08:28,825 --> 00:08:30,903
you're gonna know there's a problem.

153
00:08:30,903 --> 00:08:34,520
The bones just won't align,
muscles won't work properly,

154
00:08:34,520 --> 00:08:37,437
it's been pulled or pushed too far.

155
00:08:38,412 --> 00:08:42,579
So hyperextension, beyond
normal point of extension.

156
00:08:45,706 --> 00:08:48,010
Supination, pronation.

157
00:08:48,010 --> 00:08:49,514
Tried to describe this
a little bit earlier

158
00:08:49,514 --> 00:08:52,723
how the forearms don't
actually twist in place

159
00:08:52,723 --> 00:08:54,730
'cause there's two bones.

160
00:08:54,730 --> 00:08:58,897
So instead you have what's
called supination and pronation.

161
00:09:00,084 --> 00:09:04,183
Supination is the movement
that causes the hand

162
00:09:04,183 --> 00:09:07,538
to be facing the front,
or facing anterior.

163
00:09:07,538 --> 00:09:10,871
Supination is the opposite of pronation.

164
00:09:11,868 --> 00:09:15,868
Pronation is going to
have the palm facing back,

165
00:09:17,407 --> 00:09:19,574
the palm facing posterior.

166
00:09:21,713 --> 00:09:24,333
So we have supination and pronation,

167
00:09:24,333 --> 00:09:28,384
the two bones of the arm,
the radius and the ulna,

168
00:09:28,384 --> 00:09:32,767
actually will overlap,
or cross over each other.

169
00:09:32,767 --> 00:09:34,925
That crossing over is what creates

170
00:09:34,925 --> 00:09:37,342
the movement in your forearm.