Dissection 22 – Gross Anatomy
1. A patient complains that she has a hard time raising her hands above her head (moving
her upper limbs into a fully abducted position). Try to proceed through this question
without using the tables in the coursebook; they would make it almost trivial.
If her problem is at the sternoclavicular joint, what muscles might be involved?
What is their innervation? About what axis does the movement in question take
place?
If her problem is at the glenohumeral joint, what muscles might be involved?
What is their innervation? About what axis does the movement in question take
place?
A little confused, you ask the patient if she has any idea of what’s going on. She
responds by saying, “you’re the doctor – you should tell me,” a phrase she
accompanies by a vigorous shoulder shrug – both upwards and downwards,
showing no signs of weakness. What muscle can you now rule out?
You look at her chart – something you should have done earlier – and find that
she is recovering from a fractured humerus. Such fractures can put several nerves
at risk, depending on the location of the fracture. The chart doesn’t indicate
where the fracture occurred, so you consider the possibilities – the surgical neck,
shaft, and medial epicondyle. For each possibility, identify the nerve (and
possibly vessels) that are at risk. Given her complaint, where do you suppose the
fracture occurred?
What other movements will be weakened as a result of this fracture? About
which axes do these movements occur?
2. Patients with lateral cerebellar dysfunction exhibit dysdiadochokinesia (an inability to
perform rapidly alternating movements) and therefore have a hard time pronating and
supinating rapidly. What nerves are involved in carrying efferent signals to the muscles
responsible for these movements? What is the axis for pronation and supination?
3. A patient complains of difficulty with protraction at the sternoclavicular joint. He had
been watching “Waiting for Guffman” and, inspired, decided to try the dance Corky
performs during “Stool Boom.” His attempt was unsuccessful, however, as he wasn’t
able to protract as vigorously as Corky does.
What muscles/nerves aren’t functioning properly? About which axis does this
movement take place?
Which other movement of the sternoclavicular joint is certainly weakened?
You ask the patient to abduct his arms over his head and find that he has NO
difficulty in doing so. Which muscle/nerve is deficient in this case?
4. An avid armwrestler presents at the clinic and tells you that he’s losing all of his
matches lately. He can’t figure out exactly why, but he knows that it has to do with a
nerve lesion.
Trusting that he’s correct – his weakness does indeed stem from a nerve lesion –
what muscles/nerves are possibly affected?
After his most recent loss, your patient tells you that he got a little frustrated and
started flailing his arms all over the place. You ask him if his glenohumeral joint
dislocated and he responds by saying that it didn’t. What muscle can you now
rule out?
The patient goes on to tell you that, after his tantrum, the police were called and
he was handcuffed and thrown in jail for the night. Knowing he’s a pretty
compliant guy, you ask him if he had a hard time positioning himself for the
handcuffs and he responds by saying that he didn’t. What nerve(s) is(are)
lesioned in this case?
The patient then has an epiphany and determines that the nerve(s) damaged is(are)
anterior division nerve(s). What is responsible for his weakness?