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The contents of these triangles are mostly structures that are continu-
The neck consists essentially of five blocks of tissue running longitudin-
ally (Figs 61.1 and 61.2). These are as follows:
convenient to describe them individually in other chapters.
1 The cervical vertebrae surrounded by a number of muscles and
enclosed in a dense layer of prevertebral fascia. ous, without interruption, from one triangle to another so that it is more
2 The pharynx and larynx, partially enclosed in a thin layer of pre- The posterior triangle (Fig. 61.3)
tracheal fascia. Below the level of C6 these give way to the oesophagus The posterior triangle is bounded by:
and trachea. • The posterior border of sternomastoid.
3 & 4 Two vascular packets consisting of the common and internal • The anterior border of trapezius.
carotid arteries, the internal jugular vein and the vagus nerve, all • The middle part of the clavicle.
enclosed in the fascial carotid sheath. Stretching between the two muscles is the investing layer of deep
5 An outer enclosing sheath consisting of the sternomastoid and fascia which splits to enclose them and continues to the anterior tri-
trapezius and the investing layer of deep fascia of the neck. angle. Embedded in the deep fascia is the spinal part of the accessory
nerve which leaves the sternomastoid about halfway down its posterior
The anterior triangle border and passes into trapezius two fingerbreadths above the clavicle.
The anterior triangle (Fig. 61.4) is bounded by: It supplies both muscles. Four cutaneous nerves (transverse cervical,
• The lower border of the mandible and its backward continuation. supraclavicular, greater auricular and lesser occipital) also emerge
• The anterior border of sternomastoid. near the accessory nerve and supply the skin of the neck and the upper
• The midline of the neck. part of the chest. The external jugular vein begins near the upper end of
The anterior triangle is subdivided into: sternomastoid and runs down obliquely across this muscle to enter the
(a) The digastric triangle, bounded by: subclavian vein. It is joined by the anterior jugular and other small
• The lower border of the mandible. veins at its lower end. The inferior belly of the omohyoid muscle
• The two bellies of the digastric. crosses the lower part of the triangle.
(b) The carotid triangle, bounded by: The floor of the posterior triangle is the prevertebral fascia, deep
• The superior belly of the omohyoid. to which lie, from below upwards: scalenus anterior, scalenus medius
• The posterior belly of the digastric. and posterior, levator scapulae, and splenius capitis.
• The anterior border of sternomastoid.
(c) The muscular triangle, bounded by: Structures deep to the prevertebral fascia
• The superior belly of the omohyoid. • The upper, middle and lower trunks of the brachial plexus which
• The anterior border of sternomastoid. emerge between the scalenus anterior and the scalenus medius, the
• The midline of the neck. lower trunk resting on the 1st rib.
• The supraclavicular branches of the brachial plexus (p. 73).

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