hello all this is dr alsup and welcome to station number two where we are gonna focus on the humerus
and hopefully you recall that this is the bone of the arm we will only have one bone in the arm
as opposed to what we have in the forearm with the paired the paired bones so you can see
we have a fairly prominent proximal end and a fairly prominent distal end the proximal end will
be associated with the shoulder the distal end will be associated with the elbow so let's start
with the proximal and we're looking at a more posterior view here and you can see one of the
the most prominent things that's associated with the proximal end will be the head of the humerus
and the head of the humerus is always going to be facing medially it has got to head towards that
glenoid fossa or glenoid cavity of the scapula so that will always help in terms of getting
your bearings on some of the other structures particularly for me even when i'm looking at
the distal end and trying to tell if i'm looking at a medial epicondyle or a lateral epicondyle
there are two necks associated with the humerus you will have the anatomical neck
which is going to be just distal to the head kind of before you really get to the tubercle regions
this is what's kind of referred to as a true neck so it's always just distal to the head
and it's where it's a real relatively a little bit thinner of a bone then you will have the
surgical neck and you don't have a surgical neck at all bones that have a head but we do
in the humerus it's going to be just distal to both the tubercles and it's kind of away
from this complex of the head and the tubercles and it is here on the surgical neck that you're
going to have some important neurovasculature that's going to wrap around the surgical neck
and specifically that axillary nerve that is going to innervate the deltoid and the teres minor
is going to wrap around here and the reason that we have a separate named neck is because
this particular area of bone is one of the more commonly um one of the more common areas to have
fracture of the humerus so that is why it has a separate named area just because of the frequency
with which clinicians had to focus on this area so if you have a fracture to the surgical neck
this could directly affect the axillary nerve and directly affect the actions of the deltoid muscle
okay now moving to the tubercle portion so here again we've kind of flipped the
humerus so now we're looking at an anterior view and i know that because i can see
the lesser tubercle here and the lesser tubercle is always anteriorly facing um
if you recall the lesser tubercle is going to be the attachment site for the subscapularis muscle
opposite the head you will have the larger greater tubercle and it's larger as its name would suggest
it as i mentioned is always going to be lateral and this will always be medial because there is
the head of the humerus the greater tubercle is going to have the other three of the four
rotator cuff muscles attaching here so that's why it is larger than the lesser which only has one
and between these two structures you have the inter-tubercular sulcus
sometimes referred to as the bicipital groove so right between the two tubercles this you're going
to have muscles attaching here specifically your latissimus dorsi muscle is going to be
attaching on the floor of the inter-tubercular sulcus you'll have some others kind of
attaching along the lips but really this sulcus
serves as a protected passage for the tendon of the long head of the biceps and there'll be
a ligament that kind of runs across this area that keeps that tendon down and doesn't allow
bow stringing to occur during certain movements so really protecting that long head tendon okay
now we're moving to the distal end of the bone and i did put up a picture of the full humerus
just so we can remember where that head is because if you remember where the head is you can always
remember what's medial and what's lateral and that helps me when i'm looking at a more distal portion
so the lateral epicondyle epicondyle means it's just going to be a little bit above kind of of
the condyle and in most cases it will be just superior to the condyles the lateral epicondyle
is going to be this smaller one whereas the medial epicondyle is almost always considerably larger
than what you have on the lateral side and it should be on the same side as the head of
the humerus so recall those common tendons are going to attach here so you'll have the common
extensor tendon for the lateral epicondyle and the common flexor tendon for the medial epicondyle
now looking at the actual condyles you have two separate ones you'll have the capitulum
which means little head it is where we have the articulation of the head of the humerus and if you
recall that head of the humerus looks very kind of button shape so it'll fit pretty well right here
and then you have the trochlea which is very spool shape this kind of means this means pulley
and this allows for that articulation of the trochlear notch of the ulna
so that kind of semilunar size notch will move around the trochlea of the humerus
now if you look at a posterior view of the same structure this is an anterior view right here
and so you can really see the condyles well if you switch to the other side and look at
a posterior view you can't see them quite as well you can see a little bit of the trochlea
you can see the medial epicondyle being larger than the lateral epicondyle
but really the dominant thing on the distal portion of a posterior view is going to be
the olecranon fossa and it's quite large it's quite prominent and something i think that's
pretty hard to mix up with another structure and this allows for the accommodation of the olecranon
of the ulna during full extension of the elbow joint so if you kind of just feel your own
olecranon or the back of your elbow and you fully extend you can kind of see and feel where that's
fitting in a little bit better and projecting less than when you have full flexion of the elbow
all right so those were a lot of structures there's a lot of important things going on
in terms of the humerus both in terms of articulation as well as muscle attachment
so review these make sure to ask me if you have any questions early and often
and i thank you for your time and attention and i'll see you at station 3.