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Before you begin to dissect, it is essential that you read these instructions:
Reflection of skin
You are given the exact position of every skin incision you have to make. Cut through the skin, remembering that it is rarely more than 2mm thick. A decrease in resistance as you cut will tell you when you reach the subcutaneous tissue. To detach the skin from the subcutaneous tissue, use stout forceps to grip the angle where two incisions meet, and cut with your scalpel between the skin and the underlying subcutaneous tissue or fascia. As you lift the skin away (this is called reflecting the skin) pull on it, and continue cutting close to, and parallel with its under-surface, keeping the flap tense as you reflect it away. Most of your reflections will be made so that the flap you lift is left attached by one edge. The skin can then be replaced, between periods of dissection, over the part you are studying.
Reflection of fascia
The subcutaneous tissue between the skin and whatever structure it overlies (usually muscle) consists of fatty connective tissue known as superficial fascia, and a deeper layer of non-fatty membranous fascia called the deep fascia. The cutaneous nerves and vessels ramify in the superficial fascia, having pierced the deep fascia. Using a scalpel and forceps, the superficial fascia is then reflected from one of the edges of the area laid open by the reflection of skin.
Cleaning muscles, nerves and arteries
By cleaning a muscle, a nerve or a vessel, one means completely removing the connective tissue and fat or fascia by which it is ensheathed. This is done with forceps and scalpel, where necessary piecemeal. When you dissect, do not hesitate to remove small veins. When you are asked to define a nerve or artery, or a muscle, you are meant to carry on with the process of cleaning until the whole structure is clearly and cleanly exposed. The same is implied in the word following a nerve or artery. Any tissue that is removed from the body should be put into a receptacle so that it can eventually be buried. Most of your dissection will be made with a sharp scalpel and forceps. Blunt dissection means the process of isolating a structure without using the blade of a knife. Blunt dissection often involves pulling a nerve or artery to one side, so it must be carried out with care. One can, for example, separate a vessel which is bound by connective tissue to a nerve by pushing the points of closed forceps or scissors between them, and then gently opening the blades, or one can separate them by pushing gently with the handle of a scalpel. Do not be rough, but never be afraid to use your fingers to feel the structures which you have to clean and isolate. If, for example, it is necessary to cut through a muscle, be quite certain that you can define its edges, and if possible first insinuate a finger between it and the structures on which it is lying. As a preliminary to inserting your finger, it may be necessary to push gently with the handle of a scalpel. You may sometimes find that some of the muscles you are dissecting are unexpectedly friable and that they tear. All you can do to overcome this shortcoming is to examine the muscle or part concerned on somebody else’s dissection. Never regard your examination of a particular part or region as completed until you really have exposed the structures described in the text.
Bones
You will find it useful to have at hand the bones of the particular part on which you are working. The bones of the limbs help you to understand the action of the muscles that rise from and become inserted into them, while those of the pelvis and skull help you to understand the position of different soft structures, and the points of emergence of vessels and nerves.
Care of the dissection
After each period of study, it is essential that any individual part that is being dissected should be wrapped up in order to prevent loss of moisture and hardening of the specimen. Also, from time to time, moisten the parts that you are dissecting.
Structures that cannot be adequately dissected
You will have no difficulty in dissecting the muscles, the visceral organs, and the main vessels and nerves of the body. Some anatomical structures that are important functionally cannot, however, be studied adequately by the straightforward methods of dissection which you will be using. The main one is the lymphathic system. This consists of a network of minute channels and associated nodes that are found in most parts of the body. All you will see, and then only in some of your dissections, are well-defined solid lumps of matted tissue of varying shape, usually embedded in fascia. These are lymph nodes. When you dissect the thorax, you will also come across the main collecting duct of the whole lymphatic tree. But this is about all you will see of the system. Your dissection will also fail to reveal some of the more detailed parts of the nervous system of the body. The brain and spinal cord, which comprise the central nervous system, are dealt with in neuroscience courses. Another major part of the nervous system, the autonomic nervous system, cannot be adequately dissected
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