Human Anatomy - Key Lecture Notes - Savchuk O.I. 2017

Muscles and fasciae of the head and neck

Lecture Outline

1. Muscles of facial expression

2. Muscles of Mastication

3. SUPERFICIAL MUSCLES OF the neck

4. Deep Muscles of the Neck

5. Triangles of the neck

6. Fasciae of the neck

The Muscles of the HEAD are divided into the muscles of facial expression and the muscles of mastication.

The muscles of facial expression are thin Muscle bundles that lack fascia, insert into the Skin, and are typically arranged around the natural orifices of the face, occasionally originating from bones.

The most important muscles of facial expression:

1) The epicranius muscle has a broad tendinous part, or epicranial aponeurosis (galea aponeurotica), which fuses with the skin, and frontal and occipital bellies. Function: elevates the eyebrows, moves the scalp upward and backward ("muscle of surprise").

2) The corrugator supercilii muscle draws the eyebrows together ("frowning muscle").

3) The orbicularis oculi Muscle consists of circular muscle bundles that surround the Orbit and insert into the skin of the eyelids. It dilates the lacrimal sac, closes the eyelids, draws the eyebrows down, and pulls the skin of the cheek upward.

4) The orbicularis oris muscle lies as circular muscle bundles beneath and around the skin of the Lips. It closes the Mouth and protrudes the lips ("kissing muscle").

5) The depressor anguli oris muscle pulls the corner of the mouth downward.

6) The levator anguli oris muscle is the muscle of a good, cheerful mood ("comedy mask").

7) The buccinator muscle forms the lateral wall of the Oral Cavity. Upon contraction, it presses the cheek against the Teeth and participates in the act of sucking.

The muscles of facial expression also include the zygomaticus Major and minor, risorius, procerus, and mentalis muscles.

The muscles of mastication are represented by four pairs of muscles. They share a common feature: they originate on the BONES OF THE Skull, insert into various PARTS OF THE Mandible, and act on the temporomandibular joint.

The masseter muscle originates from the zygomatic arch and inserts into the lateral surface of the angle of the mandible. Function: elevates the mandible.

The temporalis muscle originates from the entire temporal fossa and inserts into the coronoid process of the mandible. Function: elevates the mandible; its posterior fibers retract the mandible (act of mastication).

The lateral pterygoid muscle lies in the infratemporal fossa. It originates from the pterygoid process of the Sphenoid bone and inserts into the condylar process of the mandible. Function: bilateral contraction protrudes the mandible, while unilateral contraction moves the mandible to the opposite side.

The medial pterygoid muscle originates from the pterygoid fossa and inserts into the pterygoid tuberosity on the Medial surface of the angle of the mandible. Function: together with the masseter muscle, it forms a physiological muscular sling, allowing the mandible to be firmly pressed against the Maxilla.

Neck

MUSCLES AND FASCIAE of the neck

The muscles of the neck are divided into superficial and deep groups. In addition, a separate group of superficial muscles is formed by those attached to the Hyoid bone: the suprahyoid and Infrahyoid muscles.

Superficial muscles of the neck:

1) Platysma — a thin muscular sheet located just beneath the skin. It originates from the pectoral fascia below the clavicle and inserts into the mandible. Function: depresses the corner of the mouth and tenses the skin of the neck.

2) Sternocleidomastoid muscle originates from the clavicle and Sternum and inserts into the mastoid process of the Temporal bone. Function: unilateral contraction tilts the cervical spine to the ipsilateral side; bilateral contraction maintains the head in an upright position, and maximal contraction tilts the head backward.

3) Suprahyoid muscles.

a) Digastric muscle. The anterior belly originates from the mandible, and the posterior belly from the mastoid notch of the temporal bone. An intermediate tendon connects the two bellies and attaches to the hyoid bone. Function: elevates the hyoid bone and, consequently, the Larynx; participates in swallowing and articulate speech.

b) Mylohyoid muscle extends from the mandible to the hyoid bone, forming the floor (Diaphragm) of the mouth. Its function is the same as that of the previous muscle.

c) Geniohyoid muscle runs from the mental spine of the mandible to the hyoid bone. Function: depresses the mandible when the hyoid bone is fixed, and elevates the larynx and hyoid bone when the jaws are closed (assisting in mastication, swallowing, and speech).

d) Stylohyoid muscle runs from the styloid process of the temporal bone to the hyoid bone. Its function is the same as that of the previous muscle, but it does not depress the mandible.

4) Infrahyoid muscles

a) Sternohyoid muscle originates from the sternum and inserts into the hyoid bone. It pulls the hyoid bone downward.

b) Sternothyroid muscle runs from the sternum to the oblique line of the thyroid Cartilage; it depresses the thyroid cartilage, larynx, and hyoid bone.

c) Thyrohyoid muscle is a continuation of the sternothyroid, extending from the thyroid cartilage to the hyoid bone; it elevates the larynx.

Deep muscles of the neck: these include the scalene muscles (anterior, middle, and posterior), as well as the prevertebral muscles of the Head and Neck, and the rectus capitis anterior and rectus capitis lateralis muscles.

In front of the anterior scalene muscle lies the antescalene space, and between the anterior and middle scalene muscles is the interscalene space (through which the Subclavian Artery, vein, and trunks of the Brachial Plexus pass).

Cervical fascia. According to modern anatomical data, There is a single cervical fascia divided into three layers (laminae): superficial, pretracheal, and prevertebral. The superficial layer lies beneath the platysma and forms sheaths for the trapezius and sternocleidomastoid muscles. The pretracheal layer is stretched between the omohyoid muscles and forms sheaths for the infrahyoid muscles. The prevertebral layer covers the prevertebral and scalene muscles, forming sheaths for them. Topographical and anatomical structures of the neck

1) Carotid triangle — bounded superiorly by the posterior belly of the digastric muscle, and inferiorly by the superior belly of the omohyoid muscle.

2) Omotracheal (muscular) triangle — bounded by the superior belly of the omohyoid muscle, the sternocleidomastoid muscle, and the midline of the neck.

3) Submental triangle — bounded by the anterior bellies of the digastric muscles and inferiorly by the hyoid bone.

4) Submandibular triangle — bounded by both bellies of the digastric muscle (with its intermediate tendon below) and the mandible above. Within this space, another triangle is distinguished — the lingual (Pirogov's) triangle, through which the lingual artery passes. It is bounded by the posterior border of the mylohyoid muscle, the posterior belly of the digastric muscle, and the Hypoglossal nerve.

In the lateral region:

1. Omotrapezoid triangle. Bounded by the posterior border of the sternocleidomastoid muscle, the lateral border of the trapezius muscle, and the inferior belly of the omohyoid muscle.

2. Omoclavicular triangle, bounded by the clavicle, the inferior belly of the omohyoid muscle, and the posterior border of the sternocleidomastoid muscle.

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