HUMAN ANATOMY ATLAS - G.L. Bilich - 2014

Muscular System

MUSCLES AND FASCIA OF THE HEAD

Topography of the Fascia and Fascial Spaces of the Head

The HEAD is conventionally subdivided, According to the Skull's topography, into the cranial and facial regions. The dense Hair-bearing Skin of the frontal, parietal, and occipital regions, containing numerous sweat and Sebaceous Glands, is firmly anchored to the epicranial aponeurosis (galea aponeurotica) by vertically oriented connective-tissue septa. Consequently, the subcutaneous tissue is partitioned into numerous loculi filled with adipose tissue; therefore, intradermal Arteries passing through this area—including the tiniest ones fused with the Connective Tissue fibers—do not collapse even upon minor wounds of the scalp, resulting in profuse bleeding. The epicranial aponeurosis is loosely attached to the periosteum, allowing the skin and the aponeurosis to move quite freely. In the lateral PARTS OF THE head, the epicranial aponeurosis thins out and continues into the superficial Fascia of the temporal region. Beneath the epicranial aponeurosis, between it and the periosteum, lies the subaponeurotic space, 2–3 mm thick, bounded by the origins and insertions of this Muscle. A thin layer of loose Fibrous connective tissue, 0.5–1 mm thick, lies beneath the periosteum of the cranial vault bones and is compartmentalized by suture lines. Along these sutures, the periosteum fuses firmly with the BONES OF THE cranial vault.

The thin facial skin contains a high density of sebaceous and Sweat Glands. A moderately developed layer of subcutaneous tissue covers the entire face, with the exception of the dorsum of the Nose. The superficial fascia of the head is absent because the mimetic (facial expression) Muscles insert directly into the dermis. At the same time, each facial muscle is enveloped by its own delicate connective-tissue fascia and a well-defined subcutaneous fat layer, which forms the buccal fat pad over the buccinator muscle in children, giving a child's face its characteristic rounded appearance.

The buccal fat pad (corpus adiposum buccae, or Bichat's fat pad) lies against the anterior border of the masseter muscle within a fairly dense connective-tissue capsule fused with the fascial Sheath of the temporalis muscle (named after Marie François Xavier Bichat, 1771–1802, a French anatomist and physiologist). The buccal fat pad features temporal, orbital, and pterygoid processes, which can serve pathways for the spread of inflammatory processes from the lateral facial region into the Orbit and cranial cavity. The temporal process of the buccal fat pad extends upward and forward, projecting beneath the fascia of the temporalis muscle, the lower part of which descends into the anterolateral Regions of the face (the subzygomatic region). From the fat pad, its orbital process extends into the infratemporal fossa toward the inferior orbital fissure, while the pterygoid process penetrates the pterygopalatine fossa. Occasionally, the pterygoid process extends through the inferomedial part of the superior orbital fissure into the cranial cavity, where it abuts the wall of the intercavernous sinus of the dura mater. In newborns and young infants, the fat pad prevents the Cheeks from being sucked inward during nursing.

The temporal fascia, which covers the temporalis muscle, originates on the lateral surface of the skull along the temporal line and the epicranial aponeurosis. Above the zygomatic arch (3–4 cm superior to it), the temporal fascia splits into a superficial layer, which attaches to the lateral margin of the zygomatic arch, and a deep layer, which attaches to its medial margin. Enclosed between these layers is a small amount of adipose tissue containing the superficial temporal Blood Vessels and nerves (frontal and zygomatic branches), as well as Branches of the auriculotemporal and facial nerves (Figs. 233, 234). This interfascial adipose tissue extends inferiorly and anteriorly beyond the BOUNDARIES OF THE temporal region. Along with the anterior part of the Superficial layer of the temporal fascia, it continues onto the anterolateral surface of the Zygomatic bone and the zygomatic muscles.

A small amount of connective tissue (subfascial adipose tissue) is present between the temporal fascia and the temporalis muscle; it extends inferiorly beneath the zygomatic arch into the narrow cleft between the temporal and masseter muscles, continuous with the connective tissue situated between the masseter and the lateral surface of the mandibular ramus. The masseteric artery and nerve, supplying the masseter muscle, pass into this space, while the corresponding vein emerges from it. Adipose tissue is also found in the interval between the anterior border of the temporalis muscle (beneath the temporal fascia) and the outer wall of the orbit, communicating with the region of the buccal fat pad.

Class="center">

Fig. 233. Muscles of Mastication, right view (superficial layer of the temporal fascia incised and reflected):

1 — Masseter, superficial part: 2 — Masseter, dcep part; 3 — Temporal fascia, superficial laver

Externally, the buccinator muscle is covered by the buccopharyngeal fascia (fascia buccopharyngea), where the fascia of the buccinator transitions into the adventitia of the lateral wall of the Pharynx. In the area between the pterygoid hamulus of the Sphenoid bone superiorly and the Mandible inferiorly, this fascia forms a thickened band known as the pterygomandibular raphe. On its inner aspect, facing the Oral Cavity, the buccinator muscle is lined by the oral mucosa.

The masseteric fascia (fascia masseterica), which covers the masseter muscle and is tightly fused with its superficial fascicles, attaches superiorly to the lateral surface of the zygomatic bone and the zygomatic arch. Anteriorly, the masseteric fascia fuses with the buccopharyngeal fascia, and posteriorly with the capsule of the Cytology/practical/97.html">Parotid salivary gland located in the retromandibular fossa. The parotid duct courses across the lateral surface of the fascia-covered masseter muscle in an anteroposterior direction, opening onto the buccal mucosa in the oral vestibule at the level between the First and Second upper molar Teeth.

The deep fascial space of the temporal region is situated between the temporalis muscle and the periosteum within the temporal fossa. The deep temporal vessels (anterior and posterior deep temporal arteries), ascending here from the infratemporal fossa, course through this adipose tissue.

Fig. 234. Superficial and deep layers of the temporal fascia, superior view, horizontal section above the zygomatic

arch:

1 — Cerebral Cortex; 2 — Squamous part; 3 — Temporalis; Temporal muscle; 4 — Interfascial space; 5 — Temporal fascia, deep laver; 6 — Orbit; 7— Eyebali; 8 — Temporal fascia, superficial layer

The region of the infratemporal fossa should be regarded as a deep area of the face, where adipose tissue housing Blood Vessels and nerves is located near the lower part of the temporal and pterygoid muscles. Within the infratemporal region, the temporomandibular and interpterygoid fascial spaces are distinguished, communicating with one another. The temporomandibular space, traversed by the maxillary artery and the pterygoid venous plexus, is located between the temporalis and lateral pterygoid muscles. Some Veins of this venous plexus are found within the substance of the fascia of the lateral pterygoid muscle. The interpterygoid space occupies the region between the medial and lateral pterygoid muscles, which are covered by their respective fasciae. Where these muscles come into contact, their fasciae form a single sheet known as the interpterygoid fascia. The mandibular nerve and its branches (mandibular, auriculotemporal, buccal, and lingual nerves) pass through the interpterygoid space. Blood vessels supplying the pterygoid muscles and the mandible also run through this area.

Medial to the deep facial region lies the parapharyngeal space. It is bounded laterally by the fascia-covered medial pterygoid muscle, medially by the lateral wall of the pharynx, and posteriorly by the transverse processes of the upper cervical vertebrae covered by the prevertebral fascia and muscles. Muscles originating from the styloid process (stylopharyngeus, styloglossus, and stylohyoid), enveloped in their own fasciae, divide the parapharyngeal space into anterior and posterior compartments. This musculo-fascial bundle originating from the styloid process merges with the buccopharyngeal fascia, partitioning the parapharyngeal space into anterior and posterior parts. The posterior compartment of the parapharyngeal space contains the Internal Carotid Artery, Internal jugular vein, and four Cranial Nerves (vagus, accessory, hypoglossal, and glossopharyngeal). Lymph Nodes located adjacent to the internal jugular vein are also found here. The anterior compartment of the parapharyngeal space is occupied by adipose tissue and small blood vessels.