Page 146 - untitled

AAAC65 21/5/05 11:01 AM Page 145
The ‘foundation’ for the upper part of the neck consists of the superior
and middle constrictors of the pharynx and on these lie the internal and
This is the region below the mandible and extending upwards deep to
external carotid arteries, the internal jugular vein and the last four cra-
the mandible as far as the attachment of the mylohyoid muscle to the
nial nerves (Fig. 65.1). The submandibular region
mylohyoid line of the mandible. The contents of the submandibular
• The glossopharyngeal runs forwards, across the internal carotid region include:
artery but deep to the external carotid (p. 131).
• The vagus, which is joined by the cranial root of the accessory, runs Muscles
straight down, between the internal carotid and the internal jugular and • Mylohyoid: from the hyoid to the mylohyoid line on the mand-
within the carotid sheath (p. 131). ible (Fig. 55.2). On its surface lies the anterior belly of the digastric
• The spinal root of the accessory runs backwards, crossing the inter- muscle, and the two have the same nerve supply (the mylohyoid nerve).
nal jugular vein and the transverse process of the atlas to supply ster- • The posterior belly of the digastric runs back to a groove medial to
nomastoid and trapezius (p. 131). the mastoid process and the intermediate tendon is attached to the hyoid
• The hypoglossal, having left the cranial cavity by means of the bone.
hypoglossal canal, is joined by the anterior ramus of the 1st cervical • Hyoglossus: from the greater horn of the hyoid up to the side of the
nerve, winds round the vagus and then runs downwards and forwards, tongue. Is partly deep to mylohyoid.
superficial to both carotids, giving off the descendens hypoglossi in the • The middle constrictor of the pharynx: behind and partly deep to
process. The branches and distribution of these nerves have already the hyoglossus.
been described (p. 131).
Nerves and vessels (Fig. 65.3)
The infratemporal region • The lingual artery: leaves the external carotid with an upward loop
This is the region deep to the ramus of the mandible. and then runs forwards deep to the hyoglossus. It supplies the tongue.
• The lingual nerve: enters the region by passing just behind the third
Contents molar tooth, directly in contact with the mandible, and then loops for-
• The stem of the mandibular division of the trigeminal nerve wards on the hyoglossus to enter the tongue. Suspended from it is the
which enters through the foramen ovale and immediately breaks up submandibular ganglion, in which parasympathetic fibres from the
into branches (Chapter 57). chorda tympani synapse before supplying the submandibular and sub-
• The otic ganglion, which lies medial to the nerve (Chapter 57). lingual glands. The lingual nerve carries sensory fibres from the anter-
• The medial and lateral pterygoid muscles: the medial pterygoid is ior two-thirds of the tongue as well as taste fibres which are carried in
inserted into the inner surface of the ramus and thus separates the the chorda tympani.
region from the structures lying on the superior constrictor, described • The hypoglossal nerve: crosses the loop of the lingual artery and
above. The lateral pterygoid runs backwards from the lateral pterygoid then runs forwards on the hyoglossus, below the lingual nerve, to enter
plate to the neck of the mandible and the intra-articular disc. the tongue and supply its intrinsic and extrinsic muscles.
• The maxillary artery: enters the region by passing forwards deep to
the neck of the mandible, and its branches correspond to those of the Salivary glands
nerve with the addition of the middle meningeal artery which ascends • The submandibular gland: lies on the mylohyoid and the anterior
to pass through the foramen spinosum. The maxillary artery leaves by belly of the digastric, extending up as far as the mylohyoid line. It also
entering the pterygopalatine fossa. extends back onto the hyoglossus and has a deep process which passes
• The temporomandibular joint (Fig. 65.2): this is a synovial joint forwards, deep to the mylohyoid. From this the submandibular
with an intra-articular disc but, unlike most other synovial joints, the (Wharton’s) duct travels forwards to enter the mouth at the sublingual
articular cartilage and the disc are composed of fibrocartilage or even papilla near the midline. The duct is crossed by the lingual nerve which
fibrous tissue. The lateral pterygoid muscle can pull the disc and the then passes deep to the nerve to enter the tongue. The facial artery is
head of the mandible forwards onto the articular eminence. This occurs embedded in the posterior part of the gland before turning down,
when the mouth is opened so that the joint is not a simple hinge joint. between the gland and the mandible, and then passing over the lower
The axis of rotation is through the mandibular foramen so that the in- border of the mandible to supply the face.
ferior alveolar nerve and vessels are not stretched when the mouth is • The sublingual gland: lies deep to the mylohyoid near to the mid-
opened. The mouth is opened by gravity and the suprahyoid muscles line. Its upper surface is covered by the mucous membrane of the
such as mylohyoid and geniohyoid and closed by the masseter, tem- mouth and its numerous ducts open onto a ridge in the floor of the
poralis and medial pterygoid. When the mouth is open and the head of mouth extending back from the sublingual papilla.
the mandible is on the articular eminence the joint is unstable so that a
blow on the chin may cause dislocation.

The upper part of the neck and the submandibular region 145