FASCIAE OF THE HEAD
The epicranial aponeurosis covering the dome of the skull (as pointed out above, see Fig. 143) becomes very thin on the lateral parts of the dome to become a loosely fibrous lamina, under which is a strong temporal fascia (fascia temporalis) shining like a tendon that covers the temporal muscle and arises above from the temporal line. Below the temporal line it attaches to the zygomatic arch and separates into two layers: a superficial layer, which fuses with the external surface of the arch, and a deep layer, which fuses with the internal surface of the arch. The space between the two layers is filled with fatty tissue. The temporal fascia closes the cranial fossa temporalis in the osteo-fibrous receptacle that lodges the temporal muscle with fatty tissue. The masseter muscle is covered by the masseteric fascia (fascia masseterica), which invests the muscle and attaches to the zygomatic arch above, to the mandibular border below, and to the mandibular ramus posteriorly and anteriorly. Posteriorly and partly externally, this fascia is connected with the parotid fascia (fascia parotidea), which forms a capsule around the gland. Fasciae do not exist on the face because the muscles of the facial expression lie directly under the skin. The only exception is the buccinator muscle; its posterior section is covered with the thick buccopharyngeal fascia (fascia buccopharyngea), which becomes loose anteriorly and blends with the fatty tissue of the cheek, fuses posteriorly with the pterygomandibular raphe, and is continuous with the connective-tissue covering of the pharyngeal muscles.
THE MUSCLES OF THE UPPER LIMB
The hand, as the organ of labour, performs certain necessary movements with the help of the muscles of the upper limb. The musculature of the shoulder girdle attaches it to the skeleton of the trunk thus forming muscular joining of bones, synsarcosis (Gk sarx, sarcos flesh), and moves the bones of the girdle, mainly the scapula and the whole upper limb. The muscles of the shoulder girdle run from the head, back, and chest toward the bones like to a centre from all directions. The muscles differ in origin: (1) derivatives of the ventral trunk musculature, which acquired points of attachment on the bones of the girdle, i.e. trunco-fugal muscles (rhomboideus, levator scapulae, serratus anterior, subclavius, omohyoideus); (2) derivatives of the visceral arches (trapezius); and (3) trun-copetal muscles (pectoralis major and pectoralis minor). The position and action of these muscles are discussed above in the section dealing with the muscles of the back, chest, and neck. The remaining muscles of the upper limb are derived from the ventral part of the myotomes and can be classified into the muscles of the shoulder joint, the muscles of the upper arm, the forearm, and the hand. They are innervated by branches of the brachial plexus, plexus brachialis.
THE MUSCLES OF THE UPPER LIMB
The hand, as the organ of labour, performs certain necessary movements with the help of the muscles of the upper limb. The musculature of the shoulder girdle attaches it to the skeleton of the trunk thus forming muscular joining of bones, synsarcosis (Gk sarx, sarcos flesh), and moves the bones of the girdle, mainly the scapula and the whole upper limb. The muscles of the shoulder girdle run from the head, back, and chest toward the bones like to a centre from all directions. The muscles differ in origin: (1) derivatives of the ventral trunk musculature, which acquired points of attachment on the bones of the girdle, i.e. trunco-fugal muscles (rhomboideus, levator scapulae, serratus anterior, subclavius, omohyoideus); (2) derivatives of the visceral arches (trapezius); and (3) trun-copetal muscles (pectoralis major and pectoralis minor). The position and action of these muscles are discussed above in the section dealing with the muscles of the back, chest, and neck. The remaining muscles of the upper limb are derived from the ventral part of the myotomes and can be classified into the muscles of the shoulder joint, the muscles of the upper arm, the forearm, and the hand. They are innervated by branches of the brachial plexus, plexus brachialis.