Dissection Basics | Removing Superficial Layers
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Dissection Basics | Removing Superficial Layers


Hi I’m Cristina Prall. In this video I’ll show you some basic skinning
techniques that will be helpful in lab. The goal of skinning is to remove the superficial
most layer of skin in order to see what lies deep to it. One of the most intimidating aspects of dissecting
for beginners can be estimating just how deep to make that first incision. Although the cutaneous and subcutaneous layers
of tissue will be removed throughout the dissection- important structures such as cutaneous nerves
and superficial veins do exist within these layers. So if you are trying to maintain any superficial
layers you will want to only remove the skin. So when we are ready to skin we will take
the tip of the scalpel blade and make a very shallow incision like so to insure that we
don’t go too deep. And then we will immediately check our work
to see how deep we went and distinguish the clear difference between the skin and the
subcutaneous tissue. As seen here. So when we are thinking about skinning its
important to remember that there are two layers of skin. The first and most superficial is the epidermis
which acts as a barrier to infection and also regulates trans-epidermal water loss. The second layer which is tightly adhered
to the epidermis is the dermis and it cushions the skin from stress and strain. So when we say the skin, it is a term that
combines both the epidermis and dermis as one unit. You cannot distinguish the difference between
the two layers of skin in lab with the naked eye. Deep to the dermis you will find the subcutaneous
tissue also known as the hypodermis which functions in fat storage. So in order to preserve any superficial vessels
or cutaneous nerves we are going to leave the hypodermis behind as we only remove the
epidermis and dermis. To do that we are going to use the forceps
to pick up the skin and angle our blade parallel to the skin in order to use a blade to separate
the skin from the subcutaneous tissue. A good indicator that you are only removing
the skin is that you look on the deep side of the dermis and you can see some dermal
pitting which is the dermal papillae projecting up into the epidermis giving the appearance
of little pits. And then you can simply continue skinning
until you have removed the appropriate amount of skin for your dissection. If you do not wish to preserve any superficial
structures in the subcutaneous tissue then you can go ahead and remove the subcutaneous
tissue. However we are still going to make a very
superficial incision with the tip of our scalpel blade just to see where we are at. We can see we have our layer of epidermis
and dermis here but we can kind of keep incising and checking to see how deep we are going
little by little until we start to see some muscular fibers which I can see here. I am going to make the incision a little bit
wider so I can grab the full thickness of the skin including all three of the layers
and then again I will angle my blade parallel to that of the skin and run my blade along
the plain of the muscular fascia which we are going to stay just superficial to. As you might notice in the donor the subcutaneous
tissue can sometimes take on the same color as muscle tissue which can make things confusing. Just remember to analyze the texture and look
for muscle fibers to distinguish between fat and muscle tissue. You may have a little bit of subcutaneous
tissue left behind on top of the muscle but thats okay you can come back again later and
clean that up. And you will just continue removing the skin
until you have removed the amount you are looking for. If you find that the skin you are working
with is getting to be a large flap, a helpful tip is to incise a loophole in the skin to
fit your finger through and pull back and this makes the skin taught for the dissector
and just helps the skinning process to go a little bit more smoothly as you are working. Like so. It is helpful to keep in mind that the inferior-lateral
back, abdomen, arm and thigh will have a significantly thicker layer of subcutaneous tissue than
other areas of the body such as the dorsum of the hand or scalp. So keep this in mind when your estimating
just how deep to make that first incision. Remember that the depth of skinning will depend
on the goal of each dissection and the structures you are trying to identify. And as a reminder- scalpels should primarily
be used for skinning purposes only. In our next video I’ll show you how to retract
and reflect muscles as well as how to clean neurovasculature.

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