6.6 The Scalp

 

From supraorbital margin ® highest nuchal lines at back of skull & to ears / zygomatic arches at sides

Skin, Connective tissue, Aponeurosis, Loose areolar tissue & Pericranium.

Skin

Thickest on body.  Hairiest (usually) and contains many sebaceous glands.

-           fibres of scalp muscle insert into it.

-           Firmly attached to c.t. beneath through to muscle and aponeurosis.

Occipitofrontalis

Occipitalis and frontalis parts, epicranial aponeurosis intervening.

Occipitalis from highest nuchal line ® into aponeurosis

Aponeurosis meets external occipital protuberance and medial upper nuchal line

-           laterally ® temporalis fascia above zygomatic arch

Frontalis arises from front of aponeurosis ® upper part of orbicularis oris and skin over eyebrow.

-           R and L frontalis meet in midline; blends with procerus a small muscle from nasal bone and cartilage which inserts into skin of lower forehead (contraction ® wrinkles over nose bridge)

Nerve: facial nerve, posterior auricular branch ® occipitalis; and temporal ® frontalis.

Action: Occipitalis pulls scalp back (merely anchors aponeurosis)

-           frontalis elevates eyebrows and wrinkles forehead

Loose Areolar Tissue

Scalp can be moved through here (plane for ‘scalping’)

Extends down beneath orbicularis oculi ® black eye from tracking blood.

Pericranium

Periosteum of vault: loosely attached, easily stripped by haematoma

Blood (17)

Scalp arteries from: occipital, posterior auricular and superficial temporal branches of ECA.

-           and supratrochlear and supraorbital branches of ICA

All anastomose freely.

Arterial walls in dense c.t. layer, hence held open and bleed profusely in lacerations.

Skull supplied by meningeal arteries, so protected from necrosis in scalping.

Occipital artery: apex of posterior triangle ® greater occipital nerve to back of scalp

Posterior auricular: with lesser occipital nerve behind ear

Superficial temporal: over TMJ in front of auriculotemporal n. ® zygomatic arch ® temporalis fascia;

-           middle temporal a. pierces fascia ® temporalis and anastomoses with deep temporal branches

Supraorbital and Supratrochlear run with corresponding nerves, former larger, anastomose i above.

Veins run back with arteries; in forehead, temple and occipital regions

-           receive diploic veins from frontal, parietal and occipital bones

-           note the posterior auricular vein drains scalp behind ear ® EJV; but also receives emissary vein from mastoid and sigmoid sinus; infection transmitted from mastoid ® brain through here.

Lymph

No lymph nodes in scalp; channels ® occipital and posterior auricular nodes or parotid nodes.

Nerve (18)

Run with arteries.

Posteriorly: greater occipital and 3rd occipital (posterior rami C2,3) ® vertex and posterior scalp

-           lesser occipital (anterior ramus C2) ® skin behind ear

Temple by auriculotemporal nerve and zygomaticotemporal

Forehead by supratrochlear and supraorbital.

Temporal Fossa & Zygomatic Arch (63-66)

Temporal Fossa

Bounded by temporal lines above and zygomatic arch below.

Roof = temporalis fascia

Floor = part of side of skull including pterion (frontal, parietal and squamous temporal bone meet) (2)

-           lies on course of anterior branch of middle meningeal artery; marks lat cerebral fissure)

Anterior wall = zygomatic processes of frontal / zygomatic bones & maxilla

Contents: filled with temporalis muscle which arises from floor and overlying fascia.

Deep to arch = continuous with infratemporal fossa.

Zygomatic Arch

Processes of squamous temporal and zygomatic bones: meet at down/back sloping suture.

-           completed anteriorly by zygomatic process of maxilla (see Pl 5)

Nerves crossing arch are vulnerable in incisions and fractures;

-           auriculotemporal nerve crosses well back; just in front of ear

-           temporal and zygomatic branches of facial nerve cross the arch ® frontalis & orb oris

Temporalis Fascia

Attached to superior temporal line ® down to upper border of zygomatic arch

-           above arch, splits ® one attached to lateral, other to medial arch margins.

-           space between = fat and a branch of superficial temporal artery + zygomaticotemporal branch of maxillary nerve

-           temporal and zygomatic branches of facial nerve lie superficial to or in outer layer of fascia

While operating in this region, enter this arch space from above and approach in a plane deep to outer layer to avoid damaging facial nerve branches.

Temporalis

Mastication muscle.

Arises: temporal fossa area b/n inferior temporal line & infratemporal crest and deep fascia surface

Inserts: converges to coronoid process of mandible ( fan shaped)

-           ® bevelled medial aspect adjacent to posterior border, apex and anterior border

-           bands from anterior part of insertion ® down and forward to posterior end of alveolar process enclosing retromolar fossa.

-           Deep tendinous band ® temporal crest on mandible; palpable; guide in inf alveolar n. block

Blood: temporal branches of maxillary and superficial temporal arteries

Nerve 2-3 deep temporal branches of mandibular nerve (enter on deep surface)

Action: elevates mandible when mouth closed; retracts protruded mandible.