HUMAN ANATOMY – VOLUME 1

The o r b i t a l p a r t originates from the frontal process of maxilla, the nasal part of the frontal bone and the medial palpebral ligament. Its fibers stretch along the superior and inferior margins of the orbit to its lateral wall, where the upper and lower fibers continue into each other.

The l a c r i m a l p a r t of the muscle originates from the lacrimal crest and lateral surface of the lacrimal bone. Its fibers pass behind the lacrimal sac and are inserted into the palpebral part of the orbicularis oculi muscle.

F u n c t i o n: The palpebral part of this muscle shuts the eyelids. The orbital part closes the eye tightly, squinting it, and thus causing radial folds to form at its lateral corner. The lacrimal part widens the lacrimal sac, regulating the outflow of tears into the nasolacrimal duct.

B l o o d s u p p l y: facial, superficial temporal, infraorbital and supraorbital arteries.

The corrugator supercilii muscle (m. corrugátor supercílii) originates from the medial part of the brow ridge, stretches upward and lateral and is inserted into the skin of the eyebrow.

F u n c t i o n: It corrugates the eyebrow, forming vertical folds above the root of the nose.

B l o o d s u p p l y: frontal, supraorbital and superficial temporal arteries.

Muscles of the nose

The nasalis muscle (m. nasális) consists of the transverse and alar parts.

The t r a n s v e r s e p a r t originates above and laterally of the incisors of the maxilla. Its muscle fibers stretch upward and medial and continue into a thin aponeurosis, which overlaps the nasal spine and fuses with the transversal part of the other side.

The a l a r p a r t originates on the maxillae, below and medial of the transverse part, and is inserted into the skin of the ala nasi.

F u n c t i o n: The transverse part narrows the nostrils. The alar part widens the nostrils, pulling the ala nasi down and to the side.

B l o o d s u p p l y: the superior labial artery, angular artery.

The depressor septi nasi muscle (m. depréssor sépti nási) originates above the medial incisor of the maxilla and is inserted into the cartilaginous nasal septum.

F u n c t i o n: Pulls the nasal septum down. B l o o d s u p p l y: superior labial artery.

Muscles of the mouth

The orbicularis oris muscle (m. orbiculáris óris) forms the muscles of the lips. It consists of marginal and labial parts.

The m a r g i n a l p a r t (peripheral part of the orbicularis oris) is formed by fascicles of the neighboring muscles of facial expression. The l a b i a l p a r t is the central part of this muscle. It consists of muscle fascicles that stretch from one corner of the mouth to the other.

F u n c t i o n: It closes the mouth, takes part in chewing and sucking. B l o o d s u p p l y: superior and inferior labial arteries, submental

artery.

The depressor anguli oris muscle (m. depréssor ánuguli óris) originates on the mandible, between the submental protuberance and the region of the first premolar tooth. Its fibers insert into the skin of the corner of the mouth.

F u n c t i o n: Pulls the corner of the mouth down and to the side. B l o o d s u p p l y: inferior labial artery, submental artery.

The depressor labii inferioris muscle (m. depréssor lábii inferióris) originates on the base on the mandible. It is partially covered by the depressor anguli oris muscle. Its fascicles stretch upwards and medially and are inserted into the skin and mucosa of the lower lip.

F u n c t i o n: It pulls the lower lip downward and lateral. With bilateral constriction it turns the lip inside out (expression of disgust).

B l o o d s u p p l y: inferior labial artery, submental artery.

The mentalis muscle (m. mentális): originates on the alveolar eminencies of the incisors of mandible, stretches downward and medial, unites with the muscle fibers of the paired muscle and inserts into the skin of the chin.

F u n c t i o n: Pulls the skin of the chin upward and lateral, forms a fossula on the chin and participates in pulling the lower lip forward.

B l o o d s u p p l y: inferior labial artery and submental artery.

The cheek muscle, or buccinator (m. buccinátor) forms the muscular base of the cheek. It originates on the oblique line of mandible, the outer surface of the alveolar arch of maxilla on the level of the molars, and the anterior part of the pterygomandibular raphe. Its fascicles stretch to the angle of mouth, cross over each other and continue into the muscles of lips. On the level of the second molar the buccinator is perforated by the parotid duct.

F u n c t i o n: Pulls the corner of the mouth to the back and pushes the cheeks against the teeth.

B l o o d s u p p l y: buccal artery.

F u n c t i o n: Pulls the auricular concha upward.

The auricularis posterior muscle (m. auriculáris postérior) originates from the mastoid process and is inserted into the posterior surface of the concha. It is usually better developed than the other auricular muscles.

F u n c t i o n: This muscle can pull the concha to the back.

B l o o d s u p p l y: auricularis anterior and superior muscles—super- ficial temporal artery; auricularis posterior muscle — posterior auricular artery.

Muscles of the face are demonstrated in the table 11.

Table 11. Muscles of facial expression.

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MASTICATORY MUSCLES

The muscles of mastication are derivatives of the first visceral arch. They act upon the temporomandibular joint, bringing the mandible into motion. These muscles participate in production of speech, in chewing and swallowing. This group of muscles includes the masseter, temporal, and lateral and medial pterygoid muscles. All muscles of mastication are innervated by the third branch of the trigeminal nerve.

The masseter (m. masséter) consists of superficial and deep parts. The s u p e r f i c i a l p a r t is larger; it originates on zygomatic process of maxilla and anterior part of the zygomatic arch (Fig. 101). It stretches downward and to the back and is inserted on the masseteric tuberosity of the mandible. The d e e p p a r t of this muscle is partly covered by the superficial part; it originates on the lower edge and internal surface of the zygomatic arch. Its fascicles stretch almost vertically down. Both parts are inserted on the external surface of the ramus and the angle of the mandible (to the masseteric tuberosity).

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Fig. 101. Masticatory muscles. Right aspect.

A — zygomatic arch sawed off and pulled aside with masseter: 1 — temporal muscle; 2 — coronoid process of mandible; 3 — masseter; 4 — lateral pterygoid. B — zygomatic arch and part of ramus of mandible are removed: 1 — zygomatic arch (sawed off); 2 — medial pterygoid; 3 — angle of mandible; 4 — ramus of mandible; 5 — lateral pterygoid.

F u n c t i o n: This muscle raises the mandible. The superficial part participates in protraction of the lower jaw.

B l o o d s u p p l y: masseteric artery, transverse facial artery.

The temporal muscle (m. temporális) occupies the surface of the temporal fossa and the internal surface of the temporal fascia. Its fascicles stretch downward, continuing into a tendon, which attaches to the coronoid process of the mandible.

F u n c t i o n: It lifts the mandible. Its posterior fascicles retract the lower jaw.

B l o o d s u p p l y: deep and superficial temporal arteries.

The medial pterygoid muscle (m. pterygoídeus mediális) originates in the pterygoid fossa of the pterygoid process. Its muscle fascicles stretch downwards, laterally and to the back. They are inserted on the pterygoid tuberosity of mandible.

F u n c t i o n: Lifts the mandible.

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B l o o d s u p p l y: pterygoid branches of the maxillary artery, facial artery.

The lateral pterygoid muscle (m. pterygoídeus laterális) is short and thick. It has two heads of origin — the upper and lower. The u p p e r h e a d originates from the maxillary surface and infratemporal crest of the sphenoid bone; the lo w e r h e a d — from the external surface of lateral lamina of the pterygoid process. The two heads join each other, the fascicles stretch to the back and laterally and are inserted into the neck of the articular process of the mandible, articular capsule and articular disc of the temporomandibular joint.

F u n c t i o n: During bilateral contraction the lower jaw is protracted. During unilateral contraction the muscle pulls the mandible to the opposite side.

B l o o d s u p p l y: pterygoid branches of maxillary artery, facial artery.

Masticatory muscles are demonstrated in the table 12.

Table 12. Muscles of mastication.

FASCIAE OF THE HEAD

The temporal fascia (fáscia temporális) is a thick fibrous lamina, which covers the temporal muscle. This fascia begins on the lateral surface of the skull (on the temporal line) and the galea aponeurotica. Above the zygomatic arch this fascial divides into a deep and superficial layers. The s u p e r f i c i a l l a y e r (lamina) attaches on the lateral surface of the zygomatic arch, and the d e e p l a y e r (lamina) accretes with the inner surface.

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The masseteric fascia (fáscia massetérica) covers the masseter muscle, accreting with it. At the top this fascia attaches to the lateral surface of the zygomatic bone and zygomatic arch; in the front it continues into the buccopharyngeal fascia; in the back it accretes with the capsule of the parotid gland. The b u c c o p h a r y n g e a l f a s c i a (f á s c i a b u c - c o p h a r ý n g e a) covers the buccinator muscle and accretes with the lateral wall of the pharynx. Between the hamulus of the sphenoid bone and the mandible this fascia has a thickening, which forms the p t e r y g o - m a n d i b u l a r r a p h e (ráphe pterygomandibularis).

TOPOGRAPHIC ANATOMY AND FATTY TISSUE SPACES

OF THE HEAD

The skin of the frontoparieto-occipital (pilose) region of the head is tightly accreted with the galea aponeurotica. The subcutaneous fatty tissue contains many vertical connective tissue fibers. For this reason even the smallest intracutaneous arteries of this region do not collapse after traumatic injuries of the head, which leads to profuse bleeding. The galea aponeurotica does not fuse with the periosteum, and therefore the skin above the scalp is movable. In the lateral regions of the head the galea aponeurotica continues into the superficial layer of temporal fascia. Beneath the aponeurosis there is a subaponeurotic space filled with fatty tissue, bordered by points of origin and insertion of the occipitofrontal muscle. Beneath the periosteum of the scalp there is a thin layer of loose connective tissue. The periosteum accretes with the bones of the skull along the suture lines.

The skin of the face is thin; it contains a large number of sweat and sebaceous glands. The superficial fascia is absent on the head. Muscles of facial expression are inserted into the skin. At the same time, each of these muscles is covered by a thin connective tissue fascia. In children, the welldeveloped subcutaneous fatty tissue forms an adipose body on the buccinator muscle. The buccal adipose body has a temporal, orbital and pterygopalatine processes, along which inflammation processes can spread from the face into the orbit and the cranial cavity. The temporal process of the adipose body penetrates beneath the fascia of the temporal muscle. Its orbital process extends to the inferior orbital fissure. The pterygopalatine process enters the pterygopalatine fossa. Sometimes this process enters the cranial cavity through the medial part of the superior orbital fissure. On the inside the buccinator muscle adjoins with the mucosa of the mouth.

Between the laminae of the temporal fascia there is a small amount of fatty tissue, which contains superficial vessels and nerves of the temporal region. This interfascial fatty tissue continues downwards and to the front,

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beyond the temporal region. Together with the superficial plate of the temporal fascia, it passes onto the zygomatic muscles.

Between the temporal fascia and temporal muscle there is a small amount of connective tissue, which continues between the temporal and masseter muscles, and also between the masseter and the lateral surface of the mandible. There is also fatty tissue in the space between the temporal muscle (beneath its fascia) and the external wall of the orbit. This space is communicated with the adipose tissue of the cheek.

The lateral surface of the thick masseteric fascia adjoins with the parotid duct. This duct passes towards the front and opens into the mucosa of the mouth between the upper first and second molars. The deep fatty tissue space of the temporal region is situated between the temporal muscle and the periosteum. This space contains vessels of this region, which extend from the infratemporal fossa.

The region of the infratemporal fossa, next to the lower sections of the temporal and pterygoid muscles, is filled with fatty tissue, which contains vessels and nerves. Fatty tissue fills up the t e m p o r o p t e r y g o i d and i n t e r p t e r y g o i d s p a c e s, which are communicated with each other. The temporopterygoid space is situated between the temporal and lateral pterygoid muscles. The interpterygoid space lies between the lateral and medial pterygoid muscles, which are covered with their proper fasciae.

The deep region of the face contains a p a r a p h a r y n g e a l f a t t y t i s s u e s p a c e of the head. This space is limited from the outside by the pterygoid muscle; on its inside is the lateral wall of the pharynx; in the back it is limited by the prevertebral fascia and muscles. Muscles, which originate from the styloid process (stylopharyngeal, styloglossus and stylohyoid) divide the parapharyngeal space into anterior and posterior sections. The posterior section contains the internal carotid artery, internal jugular vein and four cranial nerves (vagus, accessory, hypoglossal and glossopharyngeal). Next to the internal jugular vein there are lymph nodes. The anterior section of this space is occupied by fatty tissue with small blood vessels.

Questions for revision and examination

1.What funcitonal significance is attributed to the radial and circular orientation of muscles of facial expression? Give examples.

2.Name the parts of the orbicularis oculi muscle. Where are their points of origin and insertion, and what functions do they have?

3.What are the functions of the occipital and frontal venters of the occipitofrontal muscle?

4.Which muscles raise the mandible?

5.Which muscles lower the mandible?

6.Where does the mandible displace during bilateral contraction of the lateral pterygoid muscles?

7.Where does it displace during unilateral contraction of the lateral pterygoid muscle?

8.Name the fatty tissue spaces of the head and say where they are situated.

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MUSCLES AND FASCIAE OF THE NECK

Muscles of the neck are divided into groups according to their derivation (origin of development) and topography. According to derivation, there are muscles, which develop from the first (mandibular) and second (hyoid) visceral arches, which develop from the branchial arches and muscles and which derive from the ventral sections of myotomes.

Mesenchyme of the first visceral arch develops into the mylohyoid muscle and the anterior venter of the digastric muscle. Mesenchyme of the second visceral arch develops into the stylohyoid muscle, the posterior venter of the digastric muscle and the platysma (one of the facial expression muscles). Transformation of the branchial arches produces the sternocleidomastoid and trapezius muscles. Ventral sections of myotomes develop into the sternohyoid, thyrohyoid, sternothyroid and omohyoid muscles, as well as the anterior, middle and posterior scalene and the prevertebral muscles.

According to topography, there are superficial and deep muscles of the neck. The superficial group includes the platysma and sternocleidomastoid muscles, and two subgroups of muscles, which attach to the hyoid bone (Fig. 102 and 103). The suprahyoid group includes the mylohyoid, digastric, stylohyoid and geniohyoid muscles. The group of muscles situated below the hyoid bone (infrahyoid) includes the sternohyoid, sternothyroid, thyrohyoid and omohyoid muscles. The deep muscles of the neck are divided into the medial (prevertebral) and lateral groups. The medial group includes the longus colli and capitis muscles. The lateral group includes the anterior, middle and posterior scalene muscles.

SUPERFICIAL MUSCLES OF THE NECK

The platysma muscle (m. platýsma) is a very thin and flat muscle of facial expression, situated directly beneath the skin. It originates on the superficial lamina of the pectoral fascia, stretches upward covering the entire anterolateral surface of the neck. The platysma continues onto the face, inserting into the masseteric fascia and the depressor muscle of the lower lip.

F u n c t i o n: It tenses the skin of the neck, protecting superficial veins from collapsing, and pulls the angle of the mouth down.

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

B l o o d s u p p l y: transverse cervical artery, facial artery.

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