College of Life Sciences
www.lifesci.dundee.ac.uk
Introduction
By the end of the fourth week of foetal life, the upper limb starts to develop from limb buds via an activated group of mesenchymal cells in the lateral mesoderm. In lower animals the upper limb is an organ of locomotion, but in humans it functions as a grasping, and sensational organ. Sensory control of the upper limb is achieved via different cutaneous branches, each of which supplies a specific limited area of skin. For maximal performance, motor control is achieved via separate innervation to each single muscle fibre.
The upper limb is freely moving and delicate movements of the hand are achieved by the high level of motor innervation which is controlled by a large area of the brain. The bones of the upper limb provide support and a site for muscle attachment, while the joints facilitate accurate movements and the carrying of objects at a specific “carrying angle”. The upper limb is arranged into six segments, the shoulder joint, the arm, the elbow joint, the forearm, the wrist joint and the hand. The shoulder joint is considered to be the first segment and connects the upper limb to the trunk. The arm extends from the shoulder joint to the elbow joint. The forearm extends from the elbow joint to the wrist joint. Finally, the hand extends from the wrist joint to the tips of the fingers.
The cadaver
The cadaver is preserved by the Thiel embalming technique. This technique results in preservation of the organs and tissue in an excellent condition and colour, consistency and flexibility are preserved just like the living body. The preserved body can be used for approximately a year without any deterioration. The peritoneal cavity can also be inflated and the lungs ventilated. This embalming technique is based on keeping the body at a low temperature after infusion and its submergence in different chemical solutions. These chemicals include 4-chloro-3-methylenphenol, boric acid, and ethylene glycol; formaldehyde is kept to a minimum concentration. In addition to the excellent preservation of body tissues and organs, this technique has other advantages including flexible mobile joints, inflated peritoneal cavity, ventilated lungs, the absence of blood coagulation in the large vessels, inhibition of microbial or fungal growth, and minimal toxicity to the environment. In most cases, normal variations in the anatomical structures - which are unrelated to the age of the cadaver – can be observed. However, age related differences between bodies from young and old individuals may be observed (for example, the lack of teeth in older bodies).
The dissection instruments
Instruments (including the scalpel, scissors, and forceps) are essential to perform a dissection. The scalpel should be sharp and the blades changed regularly. Different types of forceps should be used including the broad and the fine serrated jaws types. Toothed forceps are also important in some steps, for example, skin reflection. Occasionally, instruments like the frame saw, the amputation saw, and bone cutting forceps are required. Most good quality dissection kits are made of stainless steel.