Scalp and Temple

Competencies

AN27.1: Describe the layers of the scalp, its blood supply, its nerve supply, and surgical importance.

• The scalp and temple are the important regions of the head. Injuries and infections are common in these regions.

SCALP

– The scalp is the soft tissue covering the vault of the skull (skullcap).

Extent

·  he scalp extends to the following anatomical landmarks:

  • Anteriorly: It extends up to the supraorbital margins.
  • Posteriorly: It reaches the external occipital protuberance and superior nuchal lines.
  • Laterally: It extends up to the zygomatic arches and external acoustic meatuses.

Layers (structure)

– The scalp consists of five layers, arranged from superficial to deep:

  1. Skin
  2. Subcutaneous connective tissue (superficial fascia)
  3. Epicranial aponeurosis (galea aponeurotica)
  4. Loose areolar tissue
  5. Pericranium

– Mnemonic: SCALP

  • S: Skin
  • C: Connective tissue
  • A: Aponeurosis
  • L: Loose areolar tissue
  • P: Pericranium

1. Skin

  • The skin of the scalp contains abundant hair follicles, except over the forehead.
  • It contains numerous sebaceous glands associated with the hair follicles.
  • The skin is firmly connected to the epicranial aponeurosis by dense subcutaneous connective tissue. Therefore, separating these layers during dissection is difficult.

2. Subcutaneous Connective Tissue (Superficial Fascia)

  • This layer consists of dense fibrous connective tissue that firmly binds the skin to the underlying epicranial aponeurosis.
  • It contains numerous blood vessels and nerves supplying the scalp.
  • The walls of the blood vessels are firmly attached to the surrounding fibrous tissue.
  • Clinical significance: Injuries to the scalp may cause profuse bleeding because the cut blood vessels are held open by the surrounding connective tissue and cannot retract effectively.

3. Epicranial Aponeurosis (Galea Aponeurotica)

  • The epicranial aponeurosis is a strong fibrous sheet situated beneath the superficial fascia. It connects the frontal and occipital bellies of the occipitofrontalis muscle. It allows the overlying skin and subcutaneous tissue to move over the pericranium.

Attachments

  • Anteriorly: It is continuous with the frontal bellies of the occipitofrontalis muscle.
  • Posteriorly: It is attached to the external occipital protuberance and superior nuchal lines through the occipital bellies.
  • Laterally: It continues with the temporal fascia in the region of the superior temporal lines.

4. Loose Areolar Tissue

  • This layer consists of loose connective tissue situated between the epicranial aponeurosis and pericranium.
  • It permits free movement of the superficial three layers of the scalp over the underlying skull.
  • Anteriorly: It is continuous with the loose connective tissue of the eyelids because the frontal belly of the occipitofrontalis has no direct bony attachment.
  • Posteriorly: It extends up to the superior nuchal lines.
  • Laterally: It is limited by the attachment of the epicranial aponeurosis to the temporal fascia.
  • It contains emissary veins that connect extracranial veins with intracranial dural venous sinuses.
  • Clinical significance: This layer is called the dangerous area of the scalp because infections may spread through emissary veins to the intracranial dural venous sinuses.

5. Pericranium

  • The pericranium forms the deepest layer of the scalp and represents the periosteum covering the outer surface of the skull bones.
  • It is loosely attached to the underlying bones over most of their surfaces.
  • It becomes firmly adherent along the cranial sutures.
  • Clinical significance: Blood accumulating beneath the pericranium forms a cephalohematoma, which is typically confined to a single skull bone because of the firm attachment of the pericranium at the sutures.

Blood Supply of Scalp

Arterial supply
  • The scalp receives its arterial supply from five arteries on each side.
  • These arteries are grouped according to their position in relation to the auricle.

In front of the auricle:

  1. Supratrochlear artery
  2. Supraorbital artery
  3. Superficial temporal artery

Behind the auricle:

  1. Posterior auricular artery
  2. Occipital artery

1. Supratrochlear Artery

  • It arises from the ophthalmic artery, a branch of the internal carotid artery.
  • It emerges near the superomedial margin of the orbit, medial to the supraorbital artery.
  • It ascends over the forehead to supply the medial part of the anterior scalp.

2. Supraorbital Artery

  • It originates from the ophthalmic artery, a branch of the internal carotid artery.
  • It emerges through the supraorbital notch or foramen.
  • It ascends over the forehead and supplies the anterior part of the scalp.

3. Superficial Temporal Artery

  • It is one of the two terminal branches of the external carotid artery.
  • It ascends in front of the auricle and crosses the posterior root of the zygomatic arch.
  • It divides into frontal and parietal branches, which supply the temporal and lateral regions of the scalp.

4. Posterior Auricular Artery

  • It arises from the external carotid artery.
  • It ascends behind the auricle and supplies the scalp in the region immediately above and behind the ear.

5. Occipital Artery

  • It is a branch of the external carotid artery.
  • It follows a tortuous course and passes deep to the mastoid region, where it may produce a groove on the temporal bone.
  • It emerges into the superficial fascia of the scalp by piercing the muscles and fascia of the posterior neck.
  • It enters the posterior scalp approximately midway between the auricle and external occipital protuberance.

Anastomosis

  • All five arteries form extensive anastomoses within the scalp.
  • These anastomoses establish communication between branches of the internal and external carotid arteries.
Venous drainage
  • The venous drainage of the scalp occurs through five principal veins on each side.
  • These veins generally accompany the corresponding arteries.

In front of the auricle:

  1. Supratrochlear vein
  2. Supraorbital vein
  3. Superficial temporal vein

Behind the auricle:

  1. Posterior auricular vein
  2. Occipital vein

1. Supratrochlear and Supraorbital Veins

  • These veins accompany their respective arteries.
  • They unite near the medial angle of the eye to form the angular vein, which continues inferiorly as the facial vein.

2. Superficial Temporal Vein

  • It descends in front of the tragus and enters the parotid gland.
  • Within the parotid gland, it joins the maxillary vein to form the retromandibular vein.
  • The retromandibular vein divides into anterior and posterior divisions.

Anterior division of the retromandibular vein

  • It joins the facial vein to form the common facial vein.
  • The common facial vein drains into the internal jugular vein.

Posterior division of the retromandibular vein

  • It unites with the posterior auricular vein to form the external jugular vein.
  • The external jugular vein descends through the neck and terminates in the subclavian vein.

3. Posterior Auricular Vein

  • It drains the scalp behind the auricle.
  • It joins the posterior division of the retromandibular vein to form the external jugular vein.

4. Occipital Vein

  • It drains the posterior part of the scalp.
  • It usually communicates with the suboccipital venous plexus, which drains into the deep cervical and vertebral venous systems.

Lymphatic Drainage of Scalp

– The lymphatic drainage of the scalp occurs mainly through the following groups of lymph nodes:

1. Preauricular (Parotid) Lymph Nodes

  • These nodes receive lymph from the anterior part of the scalp, particularly the frontal and anterior temporal regions.
  • They are situated in relation to the parotid gland, mainly in front of the auricle.

2. Posterior Auricular (Mastoid) Lymph Nodes

  • These nodes receive lymph from the scalp above and behind the auricle.
  • They are located over the mastoid region, posterior to the auricle.

3. Occipital Lymph Nodes

  • These nodes drain the posterior part of the scalp, particularly the occipital region.
  • They are situated near the attachment of the trapezius muscle to the occipital bone.
EMISSARY VEINS
  • Emissary veins are valveless veins that connect extracranial veins with intracranial dural venous sinuses.
  • They allow blood to flow in either direction according to the pressure gradient and help equalize venous pressure.
  • They may provide a route for the spread of infection from the scalp to the intracranial venous sinuses.

1. Parietal Emissary Vein

  • It passes through the parietal foramen.
  • It connects the veins of the scalp with the superior sagittal sinus.

2. Mastoid Emissary Vein

  • It passes through the mastoid foramen.
  • It connects extracranial veins with the sigmoid sinus.
DIPLOIC VEINS
  • Diploic veins are thin-walled, valveless veins located within the diploë, the spongy bone between the outer and inner tables of the cranial vault.
  • They drain blood from the cranial bones and communicate with extracranial veins and intracranial dural venous sinuses.
  • They are classified into four principal groups.

1. Frontal Diploic Vein

  • It drains the frontal bone.
  • It emerges near the supraorbital notch and usually drains into the supraorbital vein.

2. Anterior Temporal Diploic Vein

  • It drains the anterior temporal region, including the greater wing of the sphenoid bone.
  • It communicates with the sphenoparietal sinus.

3. Posterior Temporal Diploic Vein

  • It drains the posterior temporal and adjoining parietal regions.
  • It communicates with the transverse sinus near the parietomastoid region.

4. Occipital Diploic Vein

  • It drains the occipital bone.
  • It communicates with the transverse sinus near the internal occipital protuberance.

Nerve Supply of Scalp

  • The scalp receives both sensory and motor innervation.
  • On each side, the nerve supply is described through 10 nerves, consisting of eight sensory nerves and two motor branches.
  • These nerves are divided into two groups according to their location in relation to the auricle.
    • In front of the auricle: Four sensory nerves and one motor branch.
    • Behind the auricle: Four sensory nerves and one motor branch.

1. Nerves Supplying the Scalp in Front of the Auricle

Sensory Nerves

  1. Supratrochlear nerve: It arises from the frontal nerve, a branch of the ophthalmic division (V1) of the trigeminal nerve. It supplies the medial part of the forehead and anterior scalp.
  2. Supraorbital nerve: It is a branch of the frontal nerve (V1). It supplies the forehead and scalp, extending posteriorly towards the vertex.
  3. Zygomaticotemporal nerve: It arises from the zygomatic nerve, a branch of the maxillary division (V2) of the trigeminal nerve. It supplies the skin of the anterior temporal region.
  4. Auriculotemporal nerve: It arises from the mandibular division (V3) of the trigeminal nerve. It supplies the temporal scalp and skin in front of the auricle.

Motor Nerve

5. Temporal branch of the facial nerve: It supplies the frontal belly of the occipitofrontalis muscle, which elevates the eyebrows and produces transverse wrinkles on the forehead.

2. Nerves Supplying the Scalp Behind the Auricle

Sensory Nerves

  1. Great auricular nerve (posterior branch): It arises from the cervical plexus (C2–C3). Its posterior branch supplies the skin over the mastoid region and posterior surface of the auricle.
  2. Lesser occipital nerve: It arises from the cervical plexus, mainly from the ventral ramus of C2. It supplies the lateral part of the occipital scalp and the region behind the auricle.
  3. Greater occipital nerve: It arises from the dorsal ramus of C2. It supplies a large area of the posterior scalp, extending towards the vertex.
  4. Third occipital nerve: It arises from the dorsal ramus of C3. It supplies the skin over the lower occipital region and upper part of the posterior neck.

Motor Nerve

5. Posterior auricular branch of the facial nerve: It supplies the occipital belly of the occipitofrontalis muscle and the posterior auricular muscle.

Important Anatomical Facts

  • The trigeminal nerve (CN V) provides sensory innervation to most of the scalp anterior to the auricle.
  • The cervical spinal nerves (C2 and C3) provide sensory innervation mainly to the scalp behind the auricle.
  • The facial nerve (CN VII) supplies the muscles of the scalp through its temporal and posterior auricular branches.
  • The greater occipital nerve (C2) supplies a substantial portion of the posterior scalp and may be involved in occipital neuralgia.

Clinical Anatomy

Clinical Integration

1. Sebaceous Cyst

  • The scalp is a common site for cyst formation because it contains numerous hair follicles and associated sebaceous glands. Most cysts traditionally called sebaceous cysts on the scalp are actually pilar (trichilemmal) cysts, which arise from hair follicles.

2. Surgical Layers of the Scalp

  • The first three layers of the scalp, namely the skin, dense connective tissue, and epicranial aponeurosis, are firmly attached to one another. These layers move together as a single unit and are collectively called the surgical layers of the scalp.

3. Black Eye (Periorbital Ecchymosis)

  • Bleeding into the loose areolar tissue of the scalp may spread anteriorly into the eyelids and root of the nose. This occurs because the frontal belly of the occipitofrontalis and the epicranial aponeurosis lack direct bony attachments anteriorly. Accumulation of blood around the eyelids produces a black eye, also called periorbital ecchymosis. Posterior and lateral spread is restricted by the attachments of the occipital belly and epicranial aponeurosis near the superior nuchal and temporal lines.

4. Dangerous Area of the Scalp

  • The loose areolar tissue, which forms the fourth layer of the scalp, is known as the dangerous area of the scalp. Emissary veins passing through this layer establish connections between extracranial veins and intracranial dural venous sinuses.
  • Since these veins are valveless, infection may spread from the scalp to the dural venous sinuses. Such infections may cause dural venous sinus thrombosis, a potentially life-threatening complication.

5. Safety-Valve Hematoma

  • In certain fractures of the cranial vault, blood from an intracranial collection may escape through the fracture line into the subaponeurotic space. The blood accumulates in the loose areolar tissue beneath the epicranial aponeurosis. This collection is traditionally called a safety-valve hematoma because the escape of blood may reduce intracranial pressure. However, this mechanism does not reliably prevent compression of the brain.

6. Cephalohematoma

  • A cephalohematoma is a collection of blood between the pericranium and the underlying skull bone, usually occurring in newborns following birth-related trauma.
  • Since the pericranium is firmly attached at the cranial sutures, the hematoma remains confined to the affected bone. It commonly develops over one of the parietal bones.
  • The swelling does not cross the suture lines and usually resolves gradually without treatment.

7. Caput Succedaneum

  • Caput succedaneum is a diffuse swelling of the newborn’s scalp caused by edema of the subcutaneous tissue during delivery. It develops due to pressure on the presenting part of the fetal head, which interferes with venous and lymphatic drainage. Unlike cephalohematoma, the swelling may cross cranial suture lines. It usually resolves spontaneously within a few days after birth.

8. Profuse Bleeding from Scalp Wounds

  • Scalp injuries often produce considerable bleeding because the scalp has a rich vascular supply. The blood vessels are firmly attached to the dense fibrous conn ctive tissue of the superficial fascia. Following injury, the divided vessels cannot retract effectively, resulting in profuse bleeding. Management: Bleeding can usually be controlled by applying firm, direct pressure to compress the injured vessels against the underlying skull.

9. Healing of an Avulsed Scalp

  • The scalp has an extensive arterial network with numerous anastomoses, which supports tissue survival and wound healing. A partially avulsed scalp flap may remain viable if sufficient vascular connections are preserved. Such flaps should be assessed for viability and may be repositioned and sutured. Completely detached scalp tissue may require microsurgical replantation, as simple suturing does not reliably restore its blood supply.

10. Gaping Wounds of the Scalp

  • The epicranial aponeurosis is maintained under tension by the frontal and occipital bellies of the occipitofrontalis muscle. When the aponeurosis is divided transversely, the opposing muscle bellies pull the cut edges apart, producing a gaping scalp wound. Such wounds generally require careful suturing of the divided aponeurosis to restore tissue alignment and promote proper healing.

error: Content is protected !!
Scroll to Top