HUMAN ANATOMY – VOLUME 1

Fig. 102. Muscles of neck. Right aspect.

1 — sternocleidomastoid; 2 — mylohyoid; 3 — digastric (anterior belly); 4 — hyoid bone; 5 — sternohyoid; 6 — omohyoid muscle; 7 — anterior and middle scaleni muscles; 8 — trapesius; 9 — digastric (posterior belly).

The sternocleidomastoid muscle (m. sternocleidomastoídeus) originates from the anterior surface of manubrium sterni and medial end of clavicle. It stretches upward and somewhat lateral and attaches on the mastoid process of temporal bone.

F u n c t i o n: during bilateral contraction it bends the head back; unilateral contraction bends the head to the corresponding side and turns the face toward the opposite side. When the head is fixed this muscle pulls up the thorax, contributing to inhaling.

I n n e r v a t i o n: accessory nerve.

B l o o d s u p p l y: sternocleidomastoid branch (of the superior thyroid artery), occipital and superior thyroid arteries.

Muscles situated above the hyoid bone

The digastric muscle (m. digástricus) consists of anterior and posterior venters. The p o s t e r i o r b e l l y (venter) arises in the mastoid process of the temporal bone, stretches downward and to the front, adjoining

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Fig. 103. Muscles of neck. Anterior aspect.

1 — digastric (anterior belly); 2 — mylohyoid; 3 — sternocleidomastoid; 4 — sternohyoid; 5 — sternothyroid; 6 — omohyoid; 7 — scalenes (anterior, middle, posterior); 8 — hyoid bone; 9 — digastricus; 10 — stylohyoid.

the posterior surface of the stylohyoid bone. It continues into the i n t e r - m e d i a t e t e n d o n, which perforates the stylohyoid muscle and is inserted into the greater horn of the hyoid bone with a tendinous loop. The intermediate tendon continues into the a n t e r i o r b e l l y, which stretches up and to the front to the digastric fossa of the mandible.

F u n c t i o n: During bilateral contraction this muscle pulls the hyoid bone upward and to the back. The anterior venters dislocate the hyoid bone up and forward. When the hyoid bone is fixed (during contraction of the infrahyoid muscles) this muscle lowers the mandible, thus opening the mouth.

I n n e r v a t i o n: posterior belly — facial nerve; anterior belly—my- lohyoid nerve.

B l o o d s u p p l y: mental, occipital and auricular arteries.

The stylohyoid muscle (m. stylohyoídeus) originates from the styloid process of the temporal bone, stretches forward and down and is inserted into the body of the hyoid bone.

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F u n c t i o n: During unilateral contraction it pulls the hyoid bone backward and up, to the corresponding side. Bilateral contraction dislocated the hyoid bone up and to the back.

I n n e r v a t i o n: facial nerve.

B l o o d s u p p l y: occipital and facial arteries, sublingual branch of the lingual artery.

The mylohyoid muscle (m. mylohyoídeus) is a broad flat muscle. It originates on the mylohyoid line of the mandible. The medial two thirds of its fascicles stretch toward the middle line, where they form the tendinous raphe. Its lateral fascicles insert on the body of the hyoid bone. The mylohyoid muscle forms the muscular base of the diaphragm of the mouth. At the top it adjoins to the sublingual gland and geniohyoid muscle. At the bottom it adjoins the anterior venter of the digastric muscle.

F u n c t i o n: When the mandible is fixed (the mouth is closed) this muscle raises the hyoid bone together with the larynx. When the hyoid bone is fixed it lowers the mandible.

I n n e r v a t i o n: mylohyoid nerve (branch of the inferior alveolar nerve)

B l o o d s u p p l y: sublingual and mental arteries.

The geniohyoid muscle (m. geniohyoídeus) is situated on the superior surface of the mylohyoid muscle, at either side of the middle line. It originates from the mental spine and is inserted into the body of the hyoid bone.

F u n c t i o n: When the mandible is fixed it lifts the hyoid bone together with the larynx (during swallowing or speech). When the hyoid bone is fixed it lowers the mandible.

I n n e r v a t i o n: hypoglossal nerve, muscular branch of the cervical plexus.

B l o o d s u p p l y: sublingual artery, mental artery.

Muscles situated below the hyoid bone

During contraction, these muscles fix the hyoid bone forming a support for the larynx and mandible.

The omohyoid muscle (m. omohyoídeus) originates with its inferior belly on the superior margin of the scapula. The inferior belly stretches obliquely upward and to the front, passing lateral of the scalene muscles. Below the posterior edge of the sternocleidomastoid muscle this venter continues into the intermediate tendon, which passes into the superior venter. The s u p e r i o r b e l l y stretches upward and to the front, and is inserted into the hyoid bone.

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F u n c t i o n: When the hyoid bone is fixed, bilateral contraction stretches the pretracheal lamina of the cervical fascia preventing the collapse of deep veins of the neck. When the scapula is fixed this muscle pulls the hyoid bone down and to the back. Unilateral contraction dislocates the hyoid bone down and backwards, and toward the corresponding side.

I n n e r v a t i o n: cervical ansa.

B l o o d s u p p l y: inferior thyroid and transverse cervical arteries.

The sternohyoid muscle (m. sternohyoídeus) originates on the posterior surface of manubrium sterni and sternal end of clavicle and is inserted into the hyoid bone.

I n n e r v a t i o n: cervical ansa.

B l o o d s u p p l y: inferior thyroid and transverse cervical arteries.

The sternothyroid muscle (m. sternothyroídeus) originates from the posterior surface of the manubrium sterni and the first costal cartilage. It stretches upward and is inserted into the oblique line of the thyroid cartilage.

F u n c t i o n: lowers the larynx. I n n e r v a t i o n: cervical ansa.

B l o o d s u p p l y: inferior thyroid and transverse cervical arteries.

The thyrohyoid muscle (m. thyrohyoídeus) is, in a way, a continuation of the sternothyroid muscle. It originates from the oblique line of the thyroid cartilage and attaches the body and greater horn of the hyoid bone.

F u n c t i o n: Brings the hyoid bone closer to the larynx. When the hyoid bone is fixed it raises the larynx.

I n n e r v a t i o n: cervical ansa.

B l o o d s u p p l y: inferior thyroid and transverse cervical arteries.

DEEP MUSCLES OF THE NECK

The deep muscles of the neck are divided into a lateral and medial groups. The lateral group includes the anterior, middle and posterior scalene muscles. The medial group includes the longus colly and longus capitis muscles, rectus capitisanterior and rectus capitis lateralis muscles.

The anterior scalene muscle (m. scalénus antérior) originates from the transverse processes of C3 and C4 vertebrae. It stretches downward and is inserted into the tubercle of anterior scalene muscle of the first rib.

I n n e r v a t i o n: cervical plexus.

B l o o d s u p p l y: ascending cervical artery, inferior thyroid aretery.

The middle scalene muscle (m. scalénus médius) originates from the transverse processes of C2-C7 vertebrae. It stretches down and lateral

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and is inserted into the upper edge of rib 2, behind the groove of the subclavian artery.

I n n e r v a t i o n: cervical plexux.

B l o o d s u p p l y: vertebral artery, deep cervical artery.

The posterior scalene muscle (m. scalénus postérior) originates from the posterior tubercles of transverse processes of C4-C6 vertebrae, and is inserted into the upper edge of rib 2.

I n n e r v a t i o n: cervical plexus.

B l o o d s u p p l y: transverse cervical artery, deep cervical artery. Function of the scalene muscles: When the cervical section of the

spine is fixed, these muscles raise ribs 1 and 2 lifting the thorax. When the thorax is fixed, they bend the cervical spine forward and toward the corresponding side.

The rectus capitis anterior muscle (m. réctus cápitis antérior) originates from anterior surface of lateral mass of the atlas and fixes to the basilar part of occipital bone. It bends head forward.

I n n e r v a t i o n: cervical plexus.

B l o o d s u p p l y: vertebral artery, ascending pharyngeal artery.

The rectus capitis lateralis muscle (m. réctus cápitis laterális) originates from the transverse process of atlas and fixes to the inferior surface

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Suprahyoid muscles

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TOPOGRAPHIC ANATOMY AND FATTY TISSUE SPACES

OF THE NECK

The platysma muscle, like the other facial expression muscles, is situated beneath the skin and is covered only by its own proper fascia.

Corresponding to the three groups of muscles of the neck (superficial suprahyoid and infrahyoid), which have different derivations and anatomic locations, the c e r v i c a l f a s c i a has three layers or lamina (three cervical fasciae) (Fig. 104).

The s u p e r f i c i a l l a m i n a is attached to the hyoid bone; it covers from the front the infrahyoid and suprahyoid muscles. This lamina accretes with the connective tissue capsule of the sublingual gland, the masseteric fascia and the capsule of the parotid gland. Towards the posterior regions of the neck it accretes with the nuchal ligament. At the top it attaches to the external occipital protuberance and the superior nuchal line, and at the bottom it continues into the fsuperficial fascia of back.

The p r e t r a c h e a l l a m i n a accretes on the right and left sides with the connective tissue sheath of the neurovascular bundle (carotid artery, internal jugular vein and vagus nerve) and with the superficial lamina. Behind the pretracheal lamina lie the larynx, the thyroid gland and the upper section of the trachea. In front of it is only the superficial lamina of the cervical fascia and the platysma, which separate the skin and the inter-

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Fig. 104. Positioning of plates of cervical fascia (transverse section at a level of larynx).

1 — superficial layer; 2 — prevertebral layer; 3 — platysma; 4 — sternocleidomastoid; 5 — pretracheal layer; 6 — thyroid cartilage; 7 — rima vocalis; 8 — oesophagus; 9 — carotid sheath; 10 — longus colli; 11 — scalenus anterior; 12 — scalenus posterior; 13 — trapesius.

nal organs of the neck. The pretracheal lamina of the cervical fascia has the shape of a trapezoid, bordered by its points of attachment to lateral anatomical structures of the neck. Due to its anatomic and topographic characteristics this lamina is also called the scapuloclavicular aponeurosis. The pretracheal lamina reminds a sail, especially when it is stretched by contraction of omohyoid muscles, which eases the outflow of blood from the head. Between the superficial and pretracheal laminae, above the jugular notch, is the s u p r a s t e r n a l i n t e r f a s c i a l f a t t y t i s s u e s p a c e, which contains the jugular venous arch, which connects the right and left superficial veins. Behind the right and left sternocleidomastoid muscles this fatty tissue space has protrusions, which extend to the lateral edges of these muscles.

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Between the internal organs of the neck (thyroid gland, larynx and trachea) and the pretracheal lamina is a p r e t r a c h e a l f a t t y t i s s u e s p a c e. Along the anterior surface of trachea this space communicates with the anterior mediastinum.

The p r e v e r t e b r a l (deep) l a m i n a, which is situated behind the larynx and esophagus, covers the scalene muscles, long muscles of the head and neck, and anterior and lateral rectus muscles of the head. At the top this lamina attaches to the outside of the skull base, behind the pharyngeal tubercle; at the sides it attaches to trasverse processes of cervical vertebrae and forms fascial sheaths (cases) for the scalene muscles. At the bottom the prevertebral lamina attaches to ribs 1 and 2 and continues into the endothoracic fascia. Between this lamina and the pharynx and esophagus is a p r e v e r t e b r a l f a t t y t i s s u e s p a c e, which continues along the esophagus into the posterior mediastinum.

The interfascial spaces, filled by loose fibrous connective tissue, can spread inflammatory processes not only within the neck, but also into the anterior and posterior mediastina.

In the posterior regions of the neck, between muscles of the occipital group are the laminae of the n u c h a l f a s c i a (fáscia núchae), which forms the fascial sheath of these muscles. At the bottom this fascia continues into the thoracolumbar fascia.

TRIANGLES OF THE NECK

According to the surface topographical relief of the neck, it is divided into the anterior, sternocleidomastoid (right and left) and lateral (right and left) regions.

The anterior region, or anterior cervical triangle (trigónum cervicále antérius), is bordered at the sides by the sternocleidomastoid muscles. The base of the triangle is formed by the mandible, and the apex reaches the jugular notch of the manubrium sterni. This region, in turn, contains the medial cervical triangle, bordered by the middle line, the mandible and the edge of the sternocleidomastoid. The anterior region is also subdivided into a s u p r a h y o i d (r é g i o s u p r a h y o í d e a) and i n f r a h y o i d (r é g i o i n f r a h y o í d e a) r e g i o n s. The infrahyoid region contains the carotid and muscular (omotracheal) triangles. The c a - r o t i d t r i a n g l e (trigónum caróticum) is bordered by the posterior venter of the digastric muscle, the anterior edge of the sternocleidomastoid muscle and the superior venter of the omohyoid muscle. Beneath the superficial lamina of the cervical fascia this triangle contains the cervical branch of facial nerve, superior branch of the transverse cervical nerve

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and the anterior jugular vein. Beneath them, encased in a connective tissue sheath lie the common carotid artery, internal jugular vein and, behind them, the vagus nerve. Also in this region lie the deep lateral cervical lymph nodes. Within the carotid triangle, at the level of the hyoid bone, the common carotid artery divides into the external and internal carotid arteries. To the front of the sheath of the neurovascular bundle lies the superior root of the hypoglossal nerve. Somewhat deeper and lower than this root lies the pharyngeal nerve (branch of the vagus), and deeper, on the prevertebral lamina of the cervical fascia, lied the sympathetic trunk.

The omotracheal triangle (trigónum omotracheále) is bordered by the anterior edge of the sternocleidomastoid muscle, the superior venter of the omohyoid muscle and the middle line.

Within this triangle, above the jugular notch, the trachea is covered only by the skin and the superficial and pretracheal laminae of the cervical fascia. About 1 cm away from the middle line lies the anterior jugular vein, which extends into the interfascial fatty tissue space.

The suprahyoid region is divided into the unpaired submental and paired submandibular and lingual triangles.

The submental triangle (trigónum submentále) is bordered by the anterior ventricles of the digastric muscles. The base of the triangle is formed by the hyoid bone and its floor is formed by the right and left mylohyoid muscles. This triangle contains the submental lymph nodes.

The submandibular triangle (trigónum submandibuláre) is bordered by the body of the mandible and the anterior and posterior venters of the digastric muscle. This triangle confines the homonymous salivary gland. It also contains the cervical branch of the facial nerve and branches of the transverse nerve of the neck. In the superficial part of the triangle lie the facial artery and vein, and behind the submandibular gland lies the retromandibular vein. Within the triangle also lie the homonymous lymph nodes.

The lingual triangle (Pirogoff’s triangle, trigónum linguále) is situated within the submandibular triangle. It is bordered by the posterior edge of the mylohyoid muscle, the posterior venter of the digastric muscle and the sublingual nerve.

The l a t e r a l r e g i o n o f t h e n e c k is divided into the omoclavicular and omotrapezius triangles. The o m o c l a v i c u l a r t r i a n g l e (trigónum omoclaviculáre) is bordered by the clavicle, the inferior venter of the omohyoid muscle and the posterior edge of the sternocleidomastoid muscle. This triangle contains the end part of the subclavian artery, nerves of the brachial plexus, suprascapular artery and superficial cervical artery. To the front of the subclavian artery and the anterior scalene muscle (in the prescalene space) lies the subclavian vein. This vein is tightly

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