Now let's move to the humerus.
This long bone
that sits within the arm of the upper limb.
It attaches proximally via the head
of the humerus to the scapula and articulates
distally at the elbow joint with the ulna
and the radius. So here we can see both an anterior
and posterior view on the slide. Let's look
at this in more detail. So this is the
anterior view of a right
humerus. So here we have got the head of the
humerus that will be articulating with the
glenoid cavity. So the scapula will be positioned
here and this is the lateral aspect of the
humerus. We can see down here we have a structure
called the lateral epicondyle. We will come
back to that later on. I just really want
to concentrate on this proximal region of
the humerus up here towards the head of the
humerus. And we can see that we have got this
head here that is going to articulate within
the glenoid cavity to form the glenohumeral
joint. And you will see that the glenohumeral
joint is a really mobile joint. We will come
back to this when we look at the joint itself
and the ligaments that help to hold in more
detail later on. But we can see that the glenoid
cavity is very shallow. It is not a cup like
which has the head sitting into it. The glenoid
cavity is very shallow and the head of the
humerus sits alongside it. And due to this shallow
glenoid cavity, the upper limb is very mobile.
So we can all move our arm way above our head
and that holds that movement, it holds itself
to the articulation between the head of the
humerus and the glenoid cavity.
The humerus has a neck, in fact it has two
necks. One neck is known as the anatomical
neck and the anatomical neck sits just behind
the head of the humerus. It is an important
attachment site for the joint capsule of the
glenohumeral joint. We can see the head here
and then this dotted line is indicating the anatomical
neck. The anatomical neck is positioned between
these two important bulges of bone, these
are known as tubercles. And the tubercles sit
distal to the anatomical neck. So the anatomical
neck is positioned between the head and these
two tubercles. The second neck I want
to talk about is the
surgical neck and that runs around the humerus,
below or inferior to these two tubercles.
Let's concentrate on the tubercles for a moment.
We have the greater and the lesser tubercles.
And these are important in offering
sites for muscles to attach. So importantly
the rotator cuff muscles attach to the greater
and the lesser tubercles. And these two tubercles
are separated by a groove which we can see
here and this is known as the intertubercular
sulcus or the intertubercular groove and it
runs between the two tubercles and later on
we'll appreciate the various muscles attach
in this groove or this sulcus and it also
contains the tendon of the long head of biceps
brachii that runs up in this direction here.
We'll come back to that later on. Now let's move
down on this anterior surface to the shaft
of the humerus. We can continue down here
with the lesser tubercle as the crest of the
lesser tubercle and another crest coming down
from the great tubercle here. And we can see
this in more detail if we look at specifically
the shaft of the humerus. We have these two
crusts coming from the greater and lesser
tubercles still forming this intertubercle
sulcus down onto the shaft of the humerus.
And we can see that on this more distal aspect
of the humerus. We can see as it tapers away
moves distally towards the elbow joint,
we have what are known as medial and lateral
supracondylar ridges. These medial and lateral
supracondylar ridges are ridges formed as
the humerus begins to dilate distally.
So as the humerus passes towards the elbow
joint, it begins to dilate. And these ridges
are forming that dilation which eventually
leads on to the lateral and medial epicondyles.
So we can see the medial and the lateral
supracondylar ridges here.
We can also see, we have on the lateral aspect
again we have got the head here so this is
the medial aspect. On the lateral aspect
we have a groove here and that is known as
the deltoid tuberosity and that's the attachment
site for the deltoid muscle. So deltoid muscle
attaches to the deltoid tuberosity we can
see here. Most distally the humerus dilates
into two condyles of the humerus and these
form the articular surfaces that articulate
with the radius and ulna and these articulations
form the elbow joint. There is two articular
surfaces. We have the trochlea we can see here
medially and we have the capitulum laterally.
And these are important for articulating with the
radius. So the radius is going to articulate
with the capitulam and the ulna is going to
articulate with the trochlea of the humerus.
So these form two important articulation sites.
We can also see just before these condyles
we have these little depressions called the
radial fossae and the coronoid fossa.
And these little depressions allow these radius and
ulna bones to sit in these little depressions
when we fully flex our elbow so they can accommodate,
as we'll see when we cover the elbow joint. They
can cover the bony structures on the ulna
and radius. We will come back to them.
If we look at the posterior view of the humerus
then there is not as much detail here.
Once again we can see this is a right humerus.
We are now looking at the posterior surface
so here again is the medial aspect and here
we can see we have got the lateral aspect.
The head of the humerus pointing medially
to articulate with the glenoid cavity.
We can just see now the greater tubercle, we
can't see the lesser tubercle, that's more
on the anterior aspect and we can’t see the
intertubercular sulcus. But we make out
the position of the anatomical neck between
the head of the humerus and greater tubercle
and distal to the greater tubercle we can
see the surgical neck.
We will come back to the surgical neck cause it has
some important structures running around it,
and therefore fracture of the surgical neck
can lead to some important functional
deficits. An important structure that we can
see on this posterior aspect is the radial
groove that is passing down this posterior
surface. We can see the radial groove.
And the radial groove is important, it allows
the radial nerve and the profunda brachii artery
to run alongside as they supply the
posterior compartment of the arm.
So we can see the radial groove here is on
the shaft of the humerus on its posterior
aspect. We can also again see the medial supracondylar
ridge. We can see the lateral supracondylar
ridge and they have given rise to the medial
epicondyle and the lateral epicondyle. We can
see here. So the radial groove medial and
lateral supracondylar ridges giving way to
the medial epicondyle and the lateral epicondyle.
Same features we can see on the anterior surface.
If we look at the posterior surface of the
distal humerus we can then see that we have the
olecranon fossa and this is an important shallow
depression for the olecranon which is a bony
structure on the ulna and we look at that
next as we look at the ulna.