ANAT20006

[ChickenCh0wM1en]

LOOOOL man the mst was fried dude. Like I'm never sure what detail we had to go into. Cause even though the lecturers said stuff like "I don't expect you to know this", it still somehow popped up in the answer choices...

[ChickenCh0wM1en]

Doing some necromastery here before the exam.

Just wondering if anyone knows whether soleus/gastrocnemius is a 2 joint muscle?
And also, does anyone know what the whole concept about dermatome overlap is? I can understand the concept that adjacent dermatomes would have some area of overlap so if you injured say C7, the adjacent dermatomes C6 and C8 may be able to partially compensate but is there anything else to it?

What does it mean when they say that dermatomes do not cross at the midline? Is it in a literal anatomical term (assuming that if there was an injury to the right spinal segment T8, only the right side dermatome would be affected and left would be fine - based on this assumption?)

Thanks!

[alondouek]

Doing some necromastery here before the exam.

Just wondering if anyone knows whether soleus/gastrocnemius is a 2 joint muscle?

Gastrocnemius definitely is, not sure about soleus but I'd hazard a guess at 'no'.

[REBORN]

Gastrocnemius definitely is, not sure about soleus but I'd hazard a guess at 'no'.

yeah soleus is no.

[pi]

Just wondering if anyone knows whether soleus/gastrocnemius is a 2 joint muscle?

Gastrocnemius is, soleus isn't. I'd recommend "Thieme Atlas of Anatomy General Anatomy and Musculoskeletal System 1st - Schuenke, Schulte and Schumaker", really great atlas for MSK anatomy, one of the best for learning and visualising.

And also, does anyone know what the whole concept about dermatome overlap is? I can understand the concept that adjacent dermatomes would have some area of overlap so if you injured say C7, the adjacent dermatomes C6 and C8 may be able to partially compensate but is there anything else to it?

Not much else to it, there is a lot of overlap between dermatomes which is why there are so many different types of dermatome maps out there and why many people experience a "reduction" in sensation (for example) rather than a complete loss.

What does it mean when they say that dermatomes do not cross at the midline? Is it in a literal anatomical term (assuming that if there was an injury to the right spinal segment T8, only the right side dermatome would be affected and left would be fine - based on this assumption?)

Well injuries to the spinal cord in the fashion you describe (sounds like trauma) are usually bilateral. But it depends on the injury/pathology!

I think a good way to visualise what you're saying is to take the example of herpes zoster (ie. shingles) which lives in the dorsal root ganglion post-chicken pox. Here when someone gets shingles (being immunocompromised etc) it only stays on one side as it only supplies that one side. That's because the dorsal root ganglion are for the afferent tracts (eg. spinothalamic tract) and each half of a dermatome will be supplied by a tract that "passes through" each dorsal ganglion contralaterally (ie. the tracts decussate before the dorsal root ganglion, such a the spinothalamic which usually decussates a couple of levels above the the dermatome it supplies) to where it originated from. Hence the virus only effects one side of the dermatome!

Been a while since I touched this stuff but hope that makes sense!

[ChickenCh0wM1en]

Gastrocnemius definitely is, not sure about soleus but I'd hazard a guess at 'no'.

yeah soleus is no.

Gastrocnemius is, soleus isn't. I'd recommend "Thieme Atlas of Anatomy General Anatomy and Musculoskeletal System 1st - Schuenke, Schulte and Schumaker", really great atlas for MSK anatomy, one of the best for learning and visualising.

Not much else to it, there is a lot of overlap between dermatomes which is why there are so many different types of dermatome maps out there and why many people experience a "reduction" in sensation (for example) rather than a complete loss.

Well injuries to the spinal cord in the fashion you describe (sounds like trauma) are usually bilateral. But it depends on the injury/pathology!

I think a good way to visualise what you're saying is to take the example of herpes zoster (ie. shingles) which lives in the dorsal root ganglion post-chicken pox. Here when someone gets shingles (being immunocompromised etc) it only stays on one side as it only supplies that one side. That's because the dorsal root ganglion are for the afferent tracts (eg. spinothalamic tract) and each half of a dermatome will be supplied by a tract that "passes through" each dorsal ganglion contralaterally (ie. the tracts decussate before the dorsal root ganglion, such a the spinothalamic which usually decussates a couple of levels above the the dermatome it supplies) to where it originated from. Hence the virus only effects one side of the dermatome!

Been a while since I touched this stuff but hope that makes sense!

Thanks so much guys! It's just a bit confusing when the lecture notes said that soleus/gastrocnemius was a 2 joint muscle!


@pi If we use the example of shingles which lives in the DRG and see how the infection is only on one side and does not cross the midline, does that mean that the virus is infecting the DRG in a unilateral fashion? (because if it was bilateral it would spread to both sides/cross midline along that dermatome?) Or am I going on a tangent?

Thanks again

[pi]

Yes shingles is usually unilateral (unless it is unluckily reactivated and present in both dorsal root ganglion)

[ChickenCh0wM1en]

Yes shingles is usually unilateral (unless it is unluckily reactivated and present in both dorsal root ganglion)

Awesome, thanks so much pi