Regions of the Head and Neck
The head is the superior part of the body that is attached to the trunk by the neck. It is the control and communication centre as well as the “loading dock” for the body. It houses the brain and therefore is the site of our consciousness: ideas, creativity, imagination, responses, decision making and memory. It includes special sensory receivers (eyes, ears, mouth and nose), broadcast devices for voice and expression, and portals for the intake of fuel (food), water and oxygen and the exhaust of carbon dioxide.
The neck attaches the head to the trunk. It is therefore the transitional part of the body between the cranium superiorly and the clavicles inferiorly that joins the head to the trunk and limbs. It serves as a major conduit for structures passing between them. Like the head, the neck also houses several vital organs and structures such as the larynx, thyroid and parathyroid glands, trachea and oesophagus.
To allow clear and precise communications regarding the location of structures, injuries, or pathologies, the head and neck are each divided into regions. The large number of regions into which these body parts are divided is a reflection of both their functional complexity and importance.
The head is divided into 14 regions, 8 of which belong to the face. These regions are:
- Frontal region
- Parietal region
- Occipital region
- Temporal region
- Auricular region
- Mastoid region
- Orbital region
- Infraorbital region
- Buccal region – comprising of the cheek
- Parotid region – housing he parotid gland, the largest of three paired salivary glands
- Zygomatic region
- Nasal region
- Oral region
- Mental region – named after the mental protuberance (chin)
All of these 14 regions can be grouped into either a neurocranial portion or viscerocranial portion.
With the exception of the auricular region, which includes the external ear, the names of the regions of the neurocranial portion of the head corresponds to the underlying bones or bony features, and they are the frontal, parietal, occipital, temporal and mastoid regions. The remaining eight regions of the head belong to the face and are grouped as viscerocranial.
This portion includes the facial region, which is divided into 5 bilateral and 3 median regions, and are named according to related superficial features (oral and buccal regions), deep soft tissue formations (parotid region), and skeletal features (orbital, infraorbital, nasal, zygomatic, and mental regions). The five bilateral regions are:
- Orbital region
- Infraorbital region
- Buccal region
- Parotid region
- Zygomatic region
While the three median regions are named according to features or structures lying along the midline of the body, and are the:
- Nasal region
- Oral region
- Mental region.
The following is a brief description of some of these head regions:
This is a bilateral region named according to the bonny cavity, orbit. It includes its bony cavity and soft tissues and organs like the eyeball, extraocular muscles, eyelids, glabella, eyebrow, lacrimal glands, bulbar conjunctiva etc.
This is a region of the neurocranial portion of the head and includes the temporal and infratemporal fossae, superior and inferior to the zygomatic arch, respectively.
This is a median region of the face or viscerocranial portion of the head, and includes the oral cavity, teeth, gingivae, tongue, palate, and the region of the palatine tonsils.
The nasal region is a median region named after the nose, and thus includes this part of the respiratory tract which is also an olfactory organ. Hence the nasal region contains structures that are important for smelling and breathing.
As mentiond earlier, this is the only region of the neurocranial portion that is not named after the cranial bone. It includes the external ear which is composed of the shell-like auricle or pinna and the external acoustic meatus or canal, both of which function to collect and conduct sound, respectively, to the tympanic membrane.
The neck is divided into 4 regions to which some sub-rgions or triangles belong. This division is based on the usually visible and /or palpable borders of the large and relatively superficial sternocleidomastoid and trapezius muscles which are contained within the outermost (investing) layer of deep cervical fascia. The four regions and their sub-triangles or sub-regions are:
- Anterior Cervical Region (or Anterior Triangle of the Neck)
- Submandibular or digastrics triangle
- Carotid triangle
- Muscular or Omotracheal triangle
- Submental triangle
- Sternocleidomastoid Region
- Lesser supraclavicular fossa
- Lateral Cervical Region (or Posterior Triangle of Neck)
- Omoclavicular or Subclavian triangle
- Occipital triangle
- Posterior Cervical Region
- Suboccipital region or triangle
The sternocleidomastoid muscle is a key muscular landmark in the neck because it visibly divides each side of the neck into the anterior and lateral cervical regions (figure). The region between these triangular regions, corresponding to the area of this broad, strap-like muscle, is the sternocleidomastoid region of the neck. The sternocleidomastoid muscle (SCM) has two heads: the rounded tendon of the sternal head which attaches to the manubrium, and the thick fleshy clavicular head which attaches to the superior surface of the medial third of the clavicle. These two heads are separated inferiorly by a space, visible superficially as a small triangular depression, the lesser supraclavicular fossa.
Posterior Cervical Region
The region posterior to the anterior borders of (i.e., corresponding to the area of) the trapezius is the posterior cervical region. Its main content is the trapezius muscle which runs down to the posterolateral aspect of the trunk. The sub-occipital triangle or region lies deep to the posterior cervical region.
Lateral Cervical Region
The lateral cervical region constitutes the posterior triangle of the neck, and it is bounded by the posterior border of the SCM anteriorly, anterior border of the trapezius posteriorly, inferiorly by the middle third of the clavicle between the trapezius and the SCM, superiorly by an apex where the SCM and trapezius meet on the superior nuchal line of the occipital bone. It is also bounded by a roof formed by the investing layer of deep cervical fascia, and by a floor formed by muscles covered by the prevertebral layer of deep cervical fascia. This region contains the platysma which is a superficial muscle, amongst other structures and muscles.
For a more precise localization of structures, the posterior triangle of the neck is divided into a larger occipital triangle superiorly and a small omoclavicular triangle inferiorly by the inferior belly of the Omohyoid muscle.
The occipital triangle s so called because the occipital artery appears in its apex. The most important nerve crossing this triangle is the spinal accessory nerve (CN XI).
The omoclavicular or subclavian triangle is indicated on the surface of the neck by the supraclavicular fossa. The inferior part of the external jugular vein crosses this triangle superficially, while the subclavian artery lies deep in it. These vessels are separated by the investing layer of deep cervical fascia. Because the third part of the subclavian artery is located in this region, the omoclavicular triangle is often called the subclavian triangle.
Anterior Cervical Region
The anterior cervical region or anterior triangle of the neck has an anterior boundary, formed by the median line of the neck, a posterior boundary, formed by the anterior border of the SCM, a superior boundary, formed by the inferior border of the mandible, an apex, located at the jugular notch in the manubrium, a roof formed by subcutaneous tissue containing the platysma muscle, and a floor, formed by the pharynx, larynx and the thyroid gland. For a more precise localization of structures, the anterior cervical region is subdivided into four smaller triangles (the unpaired submental triangle and three small paired triangles: submandibular, carotid, and muscular) by the digastrics and Omohyoid muscles.
The submental triangle, inferior to the chin, is an unpaired suprahyoid area bounded inferiorly by the body of the hyoid and laterally by the right and left anterior bellies of the digastrics muscles. It has a floor which is formed by the two myolohyoid muscles which meet in a median fibrous raphe. The apex of the submental triangle is at the mandibular symphysis, the site of union of the halves of the mandible during infancy. Its base is formed by the hyoid, and the triangle contains several small submental lymph nodes and small veins that unite to form the anterior jugular vein.
The submandibular triangle is a glandular area between the inferior border of the mandible and the anterior and posterior bellies of the digastric muscle. The floor of his triangle is formed by the mylohyoid and hypoglossus muscles and the middle constrictor muscle of the pharynx. The submandibular gland nearly fills this triangle.
The carotid triangle is a vascular area bounded by the superior belly of the Omohyoid, the posterior belly of the digastrics, and the anterior border of the SCM. This triangle is important because the common carotid artery ascends into it. Its pulse can be auscultated or palpated by compressing it lightly against the transverse processes of the cervical vertebrae. At the level of the superior border of the thyroid cartilage, the common carotid artery divides into the internal and external carotid arteries. Also located within the carotid triangle are the carotid sinus and carotid body.
The muscular triangle is bounded by the superior belly of the Omohyoid muscle, the anterior border of the SCM, and the median plane of the neck. This triangle contains the infrahyoid muscles and viscera, for example, the thyroid and parathyroid glands.
Surgical Dissection of the Carotid Triangle
The carotid triangle provides an important surgical approach to the carotid system of arteries. It also provides access to the internal jugular vein (IJV), the vagus and hypoglossal nerves, and the cervical sympathetic trunk. Damage or compression of the vagus and/or recurrent laryngeal nerves during surgical dissection of the carotid triangle may produce an alteration in the voice because these nerves supply the laryngeal muscles.