ADVICE TO THE DISSECTORS
At the very outset, it may be pointed out that the “dissection” is a fine art and for which a dissector requires honest labor, skill, patience and perseverance to make it a success. To many it might be disgusting to deal with the obnoxious dead bodies, but it is the strength of mind and the earnest inquisitiveness to know the beauties of creation that are hidden inside our body, will really count towards one's progress. So, it is desired that the dissectors should be conscious of their responsibilities to learn the subject of Anatomy by means of dissection as advised below:
- Acquire some theoretical knowledge for the attachments of muscles and ligaments in relation to the particular bones before you start the dissection.
- Procure a set of “dissecting instruments” in a case at least with the followings:
- Two knives—One for rough use and the other for delicate works.
- Two pairs of dissecting forceps—One with broad and the other with fine points.
- One seeker (prove) with curved end—for exploring the vessels and nerves from the areolar tissue and fat.
- A pair of scissors.
- A pair of hooks with chains.
- Cut your nails short and wear a long apron.
- Do not use gloves unless otherwise badly necessary.
- Be steady at dissection; remember that an unsteady dissector cannot be a good surgeon in future.
- Put stress to find out all the main and important structures and identify them correctly.
- Do not waste time to search for the unimportant and very minute structures specially at the time of examination.
- Note the structural peculiarities (if any) found in course of dissection.
- While in confusion, better submit to your teacher or examiner than committing a gross error.
- Try to make the whole area of dissection very impressive by its neat and clean appearance.
- Prepare answers for, all the possible cross questions of the findings in each individual part.
- Make thorough review of the whole thing at the end of dissection.
- Pay due respect to the dead body or any of its part.
STEPS OF DISSECTION
Skin
First clean and fix the region of the body you want to dissect. Then give clear incisions to the skin according to the direction given under the individual part and reflect the skin in flaps without any injury to it. No subcutaneous fat should be taken away with the skin.
Fascia
- Superficial fascia—The cutaneous vessels and nerves which are found ramifying in this layer on their way to and from the skin should be carefully searched out and separated first from the fascia; then it is reflected as far as possible intact like the skin leaving the important cutaneous structures lying over the deep fascia.In the lower part of the abdomen, perineum and upper part of the thigh where this fascia consists of two layers—fatty (superficial) and fibrous (deep), it should be reflected separately.
Muscles
Clean the muscles and look for their attachments and relative position with other structures and while doing so, carefully preserve their arteries and nerves of supply. Do not cut any muscle if not badly required for the exposure of deeper structures. Lastly, study the character, origin, insertion, nerve supply and action of the skeletal muscles which are exposed in the dissected region.
- Voluntary or skeletal muscle—Found in the limbs head, neck and trunk.
- Involuntary or plain muscle—Found in the walls of viscera, ducts of glands and blood vessels.
- Cardiac muscle—Found in the walls of the heart. They are involuntary in action.
It is commonly known that a “muscle” is supplied by a motor nerve but in reality it is supplied by a mixed nerve, which contains about three-fifths motor and two-fifths sensory fibers together with some sympathetic nerve filaments.
Shape or Form of the Muscles
(1) Longitudinal or strap-like, (2) longitudinal with tendinous intersections, (3) triangular, (4) quadrangular, (5) fusiform, (6) digastric, (7) bicipital, (8) tricipital, (9) unipennate, (10) bipennate, (11) multipennate, (12) radial, (13) spiral and (14) cruciate.
Muscle fibers—Two types:
- Red fiber
- White fiber.
Aponeurosis: A flat fibrous sheet of connective tissue that serves to attach muscle to bone or other tissues. Sometimes serves as a fascia.
Deep Vessels and Nerves
Thoroughly clean the main arteries and their important branches. Keep only the big Venous trunks and remove all other clumsy smaller veins (which rather create much disturbances if preserved). Trace all the nerves to their destination and leave them uninjured.
Identification
- Arteries—It can be easily detected as thick-walled reddish tubes in comparison to the bluish veins.
- Veins—These are rather thin-walled and collapsible.
- Nerves—These will be found as white rounded cord-like structures but without lumen.
Study the course, relation and branches of the main arteries, veins and nerves.
Lymph Nodes
These are solid rounded bodies of different sizes connected with very fine lymph vessels. A few nodes may be preserved at a convenient place, wherever found in course of dissection.
Synovial Sheaths and Bursa
These are found at the frictional points of the body, as between the bones and tendons or between the bones and muscles. They prevent destruction and facilitate free movement of the parts. Generally, they remain discrete, but sometimes found communicated with the neighbouring joint cavity.
Bursa
It is a closed fibrous sac lined with synovial membrane containing a lubricating fluid, egg-white in nature, called “synovia”.7
Types of bursa
- Subtendinous—Between the tendon and bone or ligament or between the two rendons, e.g. biceps bursa.
- Submuscular—Between the muscle and bone, tendon or ligament.
- Subfascial—Beneath a fascia or aponeurotic sheet.
- Interligamentous—Between two ligaments.
- Subcutaneous—Between the skin and a bony prominence, e.g. prepatellar bursa.
- Articular—Acts as a joint cavity, e.g. the bursa between the dens of the axis and transverse ligament of the atlas.
Synovial Sheaths (Mucous sheaths)
They are similar in structure and function to the bursa but are found to ensheath the long tendons as in the hands and feet.
Study the modes of distribution of the sheaths which may be incised to display the tendons and vincula.
Ligaments
These are strong bands of white fibrous tissue formed by localized thickening of the fibrous capsule connecting the bones at joints. They are named according to their mode of attachments to the ends of bones concerned for a particular joint.
All the ligaments are very tough but flexible and exert unyielding tension to the abnormal movements of joint. While dissecting, learn their attachments and relations thoroughly.
Tendons
The tendons are the collection of collagen fibers by which the voluntary muscles are attached to a bone and they run parallel to the muscle fibers.