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Head anatomy and vasular imaging

Image : “Head anatomy and vasular imaging” by Patrick J. Lynch. License: CC BY-SA 2.0


Anatomy and Function of the Neck

The neck is the connection between the head and torso. The neck contains several organs and pathways and is stabilized by muscles, which form the main part of the neck. As a section of the spine, the cervical vertebrae allow movement of the head and thus expand the range of human perception.

The cranial and caudal boundaries of the neck can be identified using palpable bony protuberances. The cranial border consists of an imaginary line between the mandible ventrally and the mastoid processes and the external occipital protuberance dorsally.

Caudally, the neck is bordered by bony structures of the shoulder girdle and the sternum. The clavicle and the manubrium are the ventral borders of the neck area, while the acromion and the posterior spinous process of vertebra prominens (C7) form the dorsal border.

The laryngeal prominence of the thyroid cartilage, the anterior cartilaginous plate of the larynx, can easily be palpated and is commonly referred to as Adam’s apple. Above it, the hyoid bone can be palpated during swallowing.

Muscles of the neck

The neck contains vessels, organs, structures, fascia, and muscles that help in the communication between the central and peripheral nervous systems. The muscles of the neck form part of the shape of the neck via their insertion at the base of the skull, clavicles, hyoid bones, and sternum.

The muscles of the neck are also responsible for various movements of the neck such as anteroposterior flexion, lateral flexion, hyperextension, and rotation.

These muscles include platysma, sternocleidomastoid, hyoid muscles, and latissimus dorsi. They are organized into various triangles.

movements of the body

Picture: Movements of the Body, Part 1. By philschatz, License: CC BY 4.0,  modified by Lecturio

Fascial Organization of the Neck

Today, the subject of ‘fasciae’ has become fashionable among fitness fans and sports scientists. Hardened fasciae are often claimed to cause joint pain. This boom of the fitness-fasciae-business has produced a cadre of courses dealing with various methods of stabilization of structures related to connective tissue.

In the neck, the cervical fascia is divided into 3 layers, each at a different depth. These layers stabilize the structures and organs that run or lie in the respective segments. In the fitness scene, this area is considered rather ‘unprofitable’. However, it is crucial to understand this part of the human anatomy.

Fasciae are networks of connective tissue that surround the whole body as a continuous tension structure that ensures structural integrity.

The investing fascia is attached to the ligamentum nuchae and the spinous processes of the 7th cervical vertebrae, enveloping different structures and vessels to take the contour of a collar around the neck.

The fascial planes of the neck are divided into 3 layers as follows:

The superficial lamina originates from the mandible, clavicle, and manubrium. It fuses with the pectoral fascia caudally and with the nuchal fascia (neck fascia) dorsally. It is the most superficial of the 3 sheets, covering all the structures of the neck and is a component of the general body fascia. The superficial arteries and veins of the skin branch on its surface. It envelops the trapezius, sternocleidomastoid, and muscles of facial expression.

The pretracheal lamina (middle sheet) lies under the superficial fascia and originates from the hyoid bone, manubrium, and clavicles. It expands from cranial to caudal. Topographically, it is situated—like its name suggests—in front of the trachea. It covers the omohyoid muscles and fuses with the carotid sheath.

The pretracheal lamina covers the following structures: larynx, trachea, thyroid gland, pharynx, esophagus, infrahyoid muscles, and the carotid sheath that contains the common and internal carotid arteries, internal jugular vein, and vagal nerve.

The prevertebral lamina (deep sheet) expands from the base of the skull to the level of the 3rd thoracic vertebra and thus lies directly in front of the spine. It covers the deep neck muscles, sympathetic trunk with the 3 cervical ganglia (superior, middle, and inferior cervical ganglion), brachial plexus, subclavian artery, and phrenic nerve.

The fascia covering sternocleidomastoid also gives off smaller processes that develop into the:

  • Carotid sheath containing the vagus nerve, carotid artery, and internal jugular vein
  • Pretracheal fascia in front of the carotid sheath
  • Prevertebral fascia behind the carotid sheath

The platysma, the most superficial muscle in the neck, lies on top of the superficial lamina. It provides tension in the skin between the face and chest and is responsible for the opening of the jaw muscles (by pulling down the mandible).

Anatomy and Function of the Regions of the Lower Face

Anatomists tend to classify the body into topographic spaces. The individual regions are frequently named after their topographic location or based on the structures running through them; this also aids in understanding the anatomy of the lower face and upper neck.

The lower face and upper (cervical) neck are subdivided into the superficial and deep regions.

Superficial Regions

Temporal Fossa

Fossa Temporalis modified to German

Image: Temporal Fossa modified to German. By Anatomist90, License: CC BY-SA 3.0

The temporal fossa contains the following structures:

Temporalis muscle

The strongest of the chewing muscles is the temporalis muscle. The temporalis is a skeletal muscle that originates from the temporal surface at the lateral aspect of the skull and inserts at the coronoid process of the mandible with a strong tendon. Its function is to close the jaw. It is innervated by the deep temporal nerves of the mandibular nerve (V3 of the trigeminal nerve).

Auriculotemporal nerve

This nerve originates from V3 of the trigeminal nerve and loops around the middle meningeal artery and gives parasympathetic fibers to the parotid gland. This nerve splits into a superior ramus cranially and an inferior ramus. The 2 branches reunite after the inferior branch gives off somato-secretory fibers to the parotid gland. After that, the auriculotemporal nerve contains only sensory fibers, which innervate the temple skin, outer ear, external acoustic meatus, and the outside of the eardrum and the jaw joint. This nerve as it courses posteriorly to the condylar head can be injured during surgery of the temporomandibular joint (TMJ), causing ipsilateral paresthesia of the auricle and skin surrounding the ear. It is the main nerve that supplies the TMJ, along with branches of the masseteric and deep temporal nerves.

Superficial temporal artery

As one of the 2 final branches of the external carotid artery (the other one is the maxillary artery), it is accompanied by the auriculotemporal nerve.

Deep temporal arteries

These arteries originate from the maxillary artery and split into an anterior and a posterior part. Both parts anastomose with the superficial temporal artery and supply the temporal muscle. The posterior maxillary artery anastomoses with the lacrimal artery.

Parotideomasseteric Region and Buccal Region

This region roughly corresponds to the whole cheek. Topographically, it is located under the zygomatic ramus (zygomatic arch) and the infraorbital region.

Buccinator muscle

The buccinator muscle originates from the outer surface of the molar processes of the upper and lower jaw and interweaves with the orbicularis oris muscle. It is situated in the area of the buccal fat pad and is innervated by the buccal rami of the facial nerve (VII cranial nerve).

During muscle traction, the cheeks are pulled together, which makes food move back and forth between the teeth rows.

The buccinator muscle also maintains the tone of the upper and lower lip while whistling or playing a wind instrument. In infancy, it plays an important role in the sucking motions of the infant’s mouth at the breast. Anteriorly, the skin of the cheek is innervated by the buccal nerve and by the zygomatic nerve posteriorly, which are both branches of the facial nerve.

Deep Regions

Infratemporal Fossa

The borders of this region are a popular subject in oral examinations. Knowledge of the topographic location is thus necessary.

Located medial to the zygomatic arch and caudal to the temporal fossa, this region is limited by the maxillary tuberosity ventrally and by the articular tubercle of the temporal bone and spine of the sphenoid bone dorsally.

The greater wings of the sphenoid bone form the cranial anatomical border, the lateral lamina of the pterygoid process forms the medial border, and the zygomatic arch and mandibular ramus form the lateral border.

The following structures are important:

Medial pterygoid muscle

The medial pterygoid muscle originates from the pterygoid fossa and inserts at the pterygoid tuberculum. The innervation occurs via the medial pterygoid nerve of the mandibular nerve. The jaw closes during simultaneous contractions. A unilateral contraction causes protrusion for the crushing of food.

Lateral pterygoid muscle

The lateral pterygoid muscle is the only jaw opener of all chewing muscles. With the masseter muscle, it forms a muscle loop, which can produce more chewing power than the temporal muscle.

Furthermore, the muscle consists of 2 heads. The upper head inserts at the greater wing of the sphenoid bone, while the lower head inserts at the lateral lamina of the condylar process of the mandible. The fibers of the upper head radiate into the articular capsule of the jaw joint and the articular disc. The lateral pterygoid nerve of the mandibular nerve (V3) innervates both heads.

The Temporomandibular Joint

This articulation is a modified hinge type of synovial joint. The articular surfaces are: (1) the head or condyle of the mandible inferiorly and (2) the articular tubercle and the mandibular fossa of the squamous part of the temporal bone.

An oval fibrocartilaginous articular disc divides the joint cavity into superior and inferior compartments. The disc is fused to the articular capsule surrounding the joint.

Three extracapsular ligaments function to strengthen the joint:

  • Lateral ligament that prevents posterior dislocation of the joint is usually a thickening of the joint capsule
  • Sphenomandibular ligament that attaches to the sphenoid bone and mandible
  • Stylomandibular ligament that arises from thickening of the parotid fascia

The articular disc is more firmly bound to the mandible than to the temporal bone. Thus, when the head of the mandible slides anterior on the articular tubercle as the mouth is opened, the articular disc slides anteriorly against the posterior surface of the articular tubercle.

Mouth opening consists of protrusion of the mandibular head (a contraction of the lower head of the lateral pterygoid muscle) and ventral shifting of the disc (contraction of the upper head of the lateral pterygoid muscle). If both heads contract simultaneously, the mandible is protruded. However, in a unilateral contraction, the mandible moves to the opposite side and creates a grinding motion.

Maxillary artery

As 1 of the 2 final branches of the external carotid artery, the ‘jaw artery’ supplies the soft tissue of the face. It originates from the area of the retromandibular fossa, passes the pterygopalatine fossa, and runs close to the pterygopalatine ganglion.

In its course, it is classified into 3 parts: the mandibular, pterygoid, and pterygopalatine parts. In each part, the maxillary artery gives rise to new branches.

In the mandibular part, the branches of the inferior alveolar artery, accessory meningeal artery, middle meningeal artery, anterior tympanic artery, and deep auricular artery can be found.

In the pterygoid part, the maxillary artery branches into the masseteric artery, pterygoid rami, deep temporal artery, and buccal artery.

The pterygopalatine part, located in the pterygopalatine fossa alongside the pterygopalatine ganglion, is frequently tested in exams. Its terminal branches should be noted as the pterygopalatine part splits into the sphenopalatine artery, descending palatine artery, infraorbital artery, posterior superior alveolar artery, pharyngeal artery, and artery of the pterygoid canal.

Pterygoid Venous Plexus

This venous plexus is supplied by the inferior ophthalmic vein, inferior alveolar vein, sphenopalatine vein, deep temporal veins, and middle meningeal veins. Via a connecting piece—the maxillary vein—the venous plexus flows into the retromandibular vein and gains a connection to the cavernous sinus.

Clinical: Cavernous sinus thrombosis. The cause of this disease is a bacterial infection of the face with bacterial transmission.

Otic ganglion

This parasympathetic ganglion is located underneath the oval foramen and contains motor, sympathetic, and parasympathetic fibers. However, only parasympathetic fibers are interconnected, the motor and sympathetic fibers simply run through the ganglion.

Pterygopalatine Fossa

This fossa is bordered and defined in its position by the following structures: the sphenoid bone lies cranially, while the pyramidal process of the palatine bone is the caudal border. Anteriorly, there is the infratemporal surface of the maxilla and posteriorly, there is the greater wing of the sphenoid bone. The medial border is the perpendicular lamina of the palatine bone.

The following structures can be found here: the pterygopalatine ganglion, maxillary arterymaxillary nerve, and beginning of the zygomatic nerve and infraorbital nerve.

The pterygopalatine fossa communicates with surrounding structures via several fissures and foramina.

Retromandibular Fossa

Also referred to as a parotid box, it is important to know the borders of this structure: the external acoustic meatus lies cranially, the mandibular ramus ventrally, the pharynx medially, the sternocleidomastoid muscle dorsally, and the digastric muscle and stylohyoideus muscle caudally.

The following structures are prominent in the retromandibular fossa:

  • The parotid gland, which is one of the 3 major salivary glands. Via the retromandibular vein and the nerve network of the facial nerve, it is divided into a superficial and a deep part. The superficial part (outer lobe) touches the zygomatic arch and crosses the anterior margin of the masseter muscle. The lateral expansion reaches the mandible. The lower part (inner lobe) is significantly bulkier and completely fills the retromandibular fossa.
  • The retromandibular vein merges the maxillary and superficial temporal veins and flows into the internal jugular vein.
  • The parotid plexus, which is the splitting of the facial nerve into its branches for the innervation of the mimic muscles.
  • The parotid duct, the excretory duct of the parotid gland, leads to an opening on the opposite side of the second molar teeth.
  • The external carotid artery splits into its 2 final branches: the maxillary and superficial temporal arteries.

Clinical: Mumps is an inflammation of the parotid gland that causes increased pressure in the retromandibular fossa, which leads to severe nerve irritation and pain.

Peripharyngeal Space

This connective tissue space allows sliding motions in the neck area and surrounds the pharynx laterally and medially. A septum divides this region into 2 parts:

  • an unpaired retropharyngeal space
  • a paired lateropharyngeal space

Triangles of the Neck

The neck is considered to be quadrangular in shape. The shape forms the basis for studying the various components of the neck, their relations, and approaches during surgical procedures. The boundaries of the quadrangular shape include:

  • The mandible superiorly
  • The upper border of the clavicle inferiorly
  • Anteriorly by a line running through the midline
  • Posteriorly by the anterior margin of the trapezius

This quadrangular shape is divided into an anterior and posterior triangle by the sternocleidomastoid as it runs obliquely from the sternum to the mastoid bone. Moreover, the triangles are further subdivided into:

  1. The anterior triangle which can be subdivided by the hyoid bone into the infrahyoid and suprahyoid regions or into smaller triangles:
    1. Digastric triangle
    2. Submental triangle
    3. Carotid triangle
    4. Muscular triangle
  2. The posterior triangle which is further subdivided by the omohyoid muscle into the following smaller triangles:
    1. Occipital triangle
    2. Supraclavicular triangle

1. Submental Triangle With Lymph Nodes

This triangular-shaped region is located in the anterior cervical region. The cranial border is formed by the anterior margin of the mandible, the lateral border by the anterior belly of the digastric muscle, the caudal border by the hyoid bone, while mylohyoid muscle forms the floor.

Structures worth mentioning are the lymph nodes—submental lymphatic nodes out of the tip of the tongue, the lower incisors, and the medial lower lip. Cancer arising from the anterior third of the tongue tends to metastasize to these nodes.

2. Submandibular Triangles

This paired triangular region is also located in the anterior cervical region, lateral to the submental triangle and is bordered by the following structures: cranially by the inferior border of the mandible; the anterior belly of the digastric muscle lies ventrally, the posterior belly of the digastric muscle and the stylohyoideus muscle form the dorsal border, and the hyoid bone forms the caudal border.

The submandibular triangles are divided into superficial, middle, and deep parts.

The platysma, facial vein, and marginal mandibular ramus of the facial nerve belong to the superficial part. The submandibular gland fills the middle part. The deep region comprises the facial artery, mylohyoid nerve, submandibular ganglion, submandibular duct, lingual artery, hypoglossal nerve, mylohyoid muscle, and hyoglossus muscle.

3. Carotid Triangle

Cranially, the carotid triangle is limited by the posterior belly of the digastric muscle. The anterior margin of the sternocleidomastoideus muscle forms the dorsal border, and the omohyoid muscle forms the ventral border.

The most important structures are:

  • internal and external carotid artery
  • superior thyroid artery
  • lingual artery
  • facial artery
  • ascending pharyngeal artery
  • occipital artery
  • anterior, internal, and external jugular veins
  • superior thyroid, facial, and retromandibular veins
  • accessory, vagal, hypoglossal, and glossopharyngeal nerves
  • cervical ansa

The superior root of the cervical ansa is associated with the hypoglossal nerve and innervates the thyrohyoid and geniohyoid muscles.

4. Muscular triangle

Anterior and unpaired, it is located between the superior belly of the omohyoid, lower anterior margin of the sternocleidomastoid, and median line of the neck. Medially it contains the infrahyoid muscles, all depressors of the larynx, and hyoid bone that covers visceral structures of the neck including the thyroid gland, larynx, trachea, and esophagus.

5. Supraclavicular triangle

Boundaries:

  • Inferior boundary: clavicle
  • Superior boundary: inferior belly of omohyoid
  • Anterior boundary: sternocleidomastoid
  • Floor: splenius capitis, levator scapulae, scalenus medius, and a small portion of scalenus anterior
  • Roof: superficial layer of deep investing fascia

Contents: Trunks of the brachial plexus. Subclavian artery and external jugular vein.

6. Occipital Triangle

Boundaries:

  • Posterior boundary: trapezius
  • Anterior boundary: sternocleidomastoid
  • Inferior boundary: omohyoid
  • Floor: splenius capitis, levator scapulae, scalenus medius, and a portion of scalenus anterior
  • Roof: superficial layer of the deep investing fascia
  • Spinal accessory nerve (XI): crosses the upper half of the triangle diagonally and, passing from the deep surface of sternocleidomastoid inferiorly on levator scapulae to reach the deep surface of the trapezius, innervates sternocleidomastoid and trapezius.
  • Superficial cervical cutaneous branches of the cervical plexus: formed from ventral primary rami of spinal nerves C2-C4, which emerge from the posterior border of the sternocleidomastoid
  • Lesser occipital (C2): follows the posterior border of the sternocleidomastoid to innervate the scalp behind and above the ear.
  • Great auricular nerve (C2,3): crosses superficial to the sternocleidomastoid and innervates the skin over the parotid gland, angle of the jaw, and the posterior ear.
  • Transverse cervical cutaneous nerve of the neck (C2,3): crosses the sternocleidomastoid superficially and, is cutaneous for the skin of the front and side of the neck (anterior triangle).
  • Supraclavicular nerves (C3,4): divides into medial, intermediate, and lateral branches, which supply sensation over the shoulder (from the sternoclavicular joint to the acromion process), lateral neck, and anterior upper thoracic wall.

Part of the occipital and parts of the transverse cervical and suprascapular arteries are also found in the occipital triangle.

Anatomy and Function of the Cervical Spine and Head Joints

The human spine consists of 22–24 vertebrae, which are organized in 5 sections: cervical, thoracic, lumbar, sacral, and coccygeal. In the sagittal section, 4 curvatures can be seen, which form a double-sigmoid shape. Curvatures in the dorsal direction are referred to as kyphosis, curvatures in the ventral direction as lordosis.

Note: The cervical and lumbar spine are lordotic in nature.
Cervical Spine

Image: Cervical Spine. By BruceBlaus, License: CC BY 3.0

Generally, each vertebra consists of a vertebral body, a vertebral arch, and the processes of the vertebral arch. Their function is to distribute the weight of the upper body parts to the pelvic ring. With increasing weight, the vertebrae become larger from cranial to caudal.

In mammals, the cervical spine consists of 7 vertebrae (yes, even in a giraffe!). Morphologically, the first 2 vertebrae of the cervical spine (atlas and axis) and the last 4–5 vertebrae of the coccyx differ from the rest of the vertebrae. The transverse foramen, specific to the cervical vertebra, is an opening on each of the transverse processes which gives passage to the vertebral artery and vein and a sympathetic nerve plexus. It only exists in the cervical spine.

With the occipital bone, there are 6 joints (2 at the upper head joint, 4 at the lower head joint). They form a functional unit, which allows great degrees of motion of the head in all 3 spatial dimensions.

Next, to the foramen magnum, the occipital bone has 2 convex, downward-facing joint surfaces.

The first cervical vertebra (atlas, C1) has no spinous process or vertebral body. Unique to the second cervical vertebra (axis, C2) is the odontoid process (dens axis) on the vertebral body, which has 2 articular surfaces (posterior and anterior articular surface). Structurally, its morphology is the same as that of the other vertebrae. The 7th cervical vertebra has the longest and easily palpable spinous process and is thus referred to as vertebra prominens.

In the occipital area, there are 2 true joints, the atlantooccipital and atlantoaxial joints. Intervertebral discs are absent between the 3 parts of the joints (axis, atlas, and occiput).

Atlantoaxial Joint

Image: Atlantoaxial joint. By philschatz, License: CC BY 4.0

The 2 condyles of the occiput articulate with the superior articular surface of the atlas in the atlantooccipital joint.

The atlas is connected to the occipital bone at 2 positions. The atlantooccipital joint allows ventral and dorsal (30° altogether) nodding motions and tilting of the head to the side (10–15°). This joint has 2 degrees of motion, so the head can ‘say yes’ and is called an ellipsoid- or ‘yes-joint’.

The atlantoaxial joint consists of 4 individual joints. Together, they are referred to as a pivot joint and allow rotation of the atlas around the longitudinal axis of the dens axis (45°). This bi-joint consists of the median atlantoaxial joint and the lateral atlantoaxial joint. The rotation of the atlas around the process of the axis makes the person ‘say no’ (‘no-joint’).

Due to the absent intervertebral discs, the mobility of the head joints is most extensive. However, this also makes them less stable than the other sections of the spine. The proximity to vital nervous and capillary structures (e.g., medulla oblongata) thus requires firm protection with ligaments. You should know the following head-joint ligaments:

Ligament Origin Insertion Function
posterior atlantooccipital membrane posterior arch of the atlas foramen magnum inhibition, ventral flexion
anterior atlantooccipital membrane anterior arch of the atlas foramen magnum inhibition, dorsal extension
tectorial membrane posterior surface of the body of the axis clivus of the occipital bone inhibition, ventral flexion
longitudinal fascicles posterior surface of the body of the axis foramen magnum inhibition, ventral flexion
transverse ligament of the atlas between the lateral masses of the atlas between the lateral masses of the atlas inhibition, ventral flexion
alar ligaments dens condyles of the occiput and foramen magnum limitation of rotation in the atlantoaxial joint. inhibition, ventral flexion
apical odontoid ligament dens foramen magnum inhibition, ventral flexion

(source: Duale Reihe Anatomie, 2nd Edition, Thieme Verlag, p. 225)

Examination of the Cervical Spine

  • Palpation: Simple palpation and light touch is the first tool for assessing impairments concerning the muscles or connective tissue.
  • X-ray: With this imaging procedure, the bone and joint anatomy can be visualized in terms of structure, shape, and alignment.
  • MRI: With MRI, the spinal cord and osteoligamentary lesions can be seen.
  • CT: CT allows detailed imaging of bone lesions, via computer-based analysis, consisting of several X-ray images at different angles which are combined to form sectional views.

Anatomy and Function of the Cervical Organs

Pharynx

The pharynx allows the transport of respiratory air, solid food, and fluids from the mouth to their respective destinations. It is connected to the posterior part of the oral cavity (as a connection to the digestive tract) and to the nose (as a connection to the respiratory system). It is a muscular tube that is lined with mucosa.

pharynx of human

Image: Pharynx. By philschatz, License: CC BY 4.0

The pharynx forms a juncture at the base of the skull. The lower part is connected to the larynx and with the esophagus. Within the pharynx, there are pathways for air and food, which are separated from each other at the lower end by the epiglottis.

The walls of the pharyngeal tube consist of striated muscles. The inner layer, the mucosa, keeps the surface moist.

Concerning the structure of the pharynx, one must distinguish between the oropharynx, nasopharynx, and laryngopharynx:

  • The nasopharynx is located in the upper area of the pharynx and does not belong to the neck.
  • The oropharynx is part of the airways. Yet, this is where a part of the swallowing process occurs. The intake of solid food and fluid takes place here. In the oropharynx, there are the paired palatine tonsils. These are like the unpaired pharyngeal tonsil, part of the lymphatic system (Waldeyer’s tonsillar ring) and serves as an immune defense.
  • The laryngopharynx represents the lower part of the pharynx. It between the hyoid bone and the larynx, as well as the beginning of the esophagus. Here, the actual act of swallowing takes place.

Larynx

The larynx allows phonation and separates the airways from the esophagus.

The larynx consists of a tube-shaped cartilage frame. It gains its stability by the connection between the cartilage and muscles and ligaments. The largest cartilage in the larynx is the thyroid cartilage, which gives the whole larynx the shape of a triangle. The epiglottis lies on the upper margin of the thyroid cartilage.

The epiglottis has a crucial function in the swallowing process: it can close the larynx so that food components cannot access the airways.

Below the thyroid cartilage is the cricoid cartilage, the base for the paired arytenoid cartilages. They are responsible for the positioning and tension of the vocal cords (vocal ligament) allowing phonation.

Except for the epiglottis and vocal cords, the whole larynx has a mucosa that moistens the respiratory air and cleans it of small dust particles.

Trachea

structure of the trachea

Image: Trachea. By BruceBlaus, License: CC BY 3.0

The trachea is an 11-cm long, 1.5-cm wide connecting tube between the larynx and bronchial system of the lung. It is stabilized by approx. 20 semicircular hyaline cartilage rings, inferior to the fully circled cricoid cartilage. These cartilage rings are connected to each other via elastic connective tissue.

The inner lining consists of respiratory epithelium (ciliated epithelium and goblet cells). The goblet cells allow for lubrication via the secretion of mucous slime.

Cilia remove tiny foreign bodies from the respiratory system and transport them back to the mouth or nose. The wall of the trachea touches the esophagus dorsally.

Esophagus

This roughly 25-cm long muscular tube connects the pharynx to the stomach and transports solid and fluid food. Topographically, the esophagus is situated between the trachea ventrally and the spine dorsally.

The esophagus starts just distal to the cricoid cartilage located at the level of the 6th cervical vertebra and ends at the cardia of the stomach, which is located at the level of the 11th thoracic vertebra. Thus, the course of the esophagus in the area of the neck is rather short.

The directed transport is reinforced by the peristalsis of the muscular tube.

Grossly, the esophagus has 3 areas of constriction. They form the areas where foreign bodies could be stuck or, more importantly, they are landmarks that guide esophagogastroduodenoscopy. These narrowings are:

  1. At the cricopharyngeal sphincter junction, which is about 15 cm from the upper incisor teeth and corresponds to the 6th cervical vertebra.
  2. Where the arch of the aorta and the left main bronchus cross the esophagus. This narrowing is located 23 cm from the upper incisor teeth.
  3. Where the esophagus crosses the diaphragm, located 40 cm from the upper incisor teeth.

Histologically, the esophagus consists of several layers and its lumen is covered with mucosa.

Thyroid Gland

Situated below the larynx, this organ weighs about 20 grams and has the shape of a butterfly. The 2 lateral lobes lie to the left and right of the paired thyroid cartilage of the larynx. They are connected to each other via a bridge of connective tissue, the isthmus. The follicles of the gland are organized in lobules.

structure ofThyroid Gland and its micrograph

Image: Thyroid Gland. By philschatz, License: CC BY 4.0

The main function of the thyroid gland is the production of the iodine-containing thyroid hormones—thyroxine (T4) and triiodothyronine (T3), and the peptide hormone—calcitonin.

On the posterior side of both lobes are the parathyroid glands—4 small nodules that produce parathyroid hormone. This hormone is involved in calcium and phosphate metabolism.

Parathyroid Glands and micrograph of them

Image: Parathyroid Glands. By philschatz, License: CC BY 4.0

Overview of Head and Neck Tumors

Different types of cancer can be included in the term ‘head and neck tumors’, as they can develop in any part of the head and neck.

For example, these cancers can develop in the oral cavity (carcinoma of the oral cavity), pharynx (pharyngeal carcinoma), larynx (laryngeal carcinoma), nose, paranasal sinuses, and outer neck areas, especially in the thyroid gland.

These tumors mostly begin their malignant degeneration in the superficial cell layers (squamous cell carcinoma). Less often, adenocarcinoma develops from the gland-bearing tissue and sarcomas from soft tissue.

Information from the Robert-Koch Institute states that laryngeal cancer is the most frequent form of cancer in the head and neck area. Every year, 3,600 men and 500 women develop the disease. The average age of onset is 68 years. It is estimated that about 50 per 100,000 people develop cancer of the head and neck in Germany every year.

In contrast, about 180 per 100,000 people (women and men combined) develop colon or rectal cancer. Breast cancer, the most frequent type of cancer in women, has an incidence of about 136 per 100,000. The incidence of prostate cancer is 145 per 100,000.

The development of malignant tumors is influenced by several factors like smoking, regular consumption of alcohol, exposure to hazardous substances (e.g., asbestos, paints rich in chrome or nickel), and viral infections (e.g., human papillomavirus, HIV).

Chronic mucosal ulcers, UV and radioactive radiation, bad mouth hygiene, and a weakened immune system may also contribute to the development of head and neck cancer.

Preliminary Stages of Cancer: Leukoplakia

Preliminary stages of cancer, so-called precancerous lesions, form the basis of malignant tumors. Leukoplakia–also referred to as ‘white calluses disease’–is one of these precancerous lesions. They are seen as ligamentous white lesions on the gums and inner aspect of the cheeks that cannot be wiped off.

Leukoplakia mainly occurs in the mucosae of the oral cavity, pharynx, or larynx.

It mainly occurs as a result of chronic inflammation, such as repeated tobacco use, loose dentures, loose teeth, and alcohol use.

Superficially, there are white areas, which cannot be wiped away and are caused by a pathological thickening of the outer layers of the mucosa. Over time, they transform into malignancies.

Often, these white spots are not larger than pinheads, but they should be spotted early by an ENT specialist or dentist.

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