Scalp

SCALP

Introduction Extent Layers Superficial Temporal Region Arterial Supply Venous Drainage Lymphatic Drainage Nerve Supply Clinical Anatomy

1 Introduction

  • Face is the most prominent part of the body.
  • Facial muscles, being the muscles of facial expression, express emotions such as:
    • Happiness
    • Joy
    • Sadness
    • Anger
    • Frowning
    • Grinning
  • Therefore, the face is an index of mind.
  • The superficial temporal region is conventionally studied with the scalp because both regions have certain structures in common.

2 Scalp and Extent

The soft tissues covering the cranial vault form the scalp.

Extent of Scalp

  • Anteriorly → up to the supraorbital margins.
  • Posteriorly → up to the external occipital protuberance and superior nuchal lines.
  • On each side → up to the zygomatic arch and external acoustic meatus.
  • Some authors consider that the scalp extends up to the superior temporal line.

3 Layers of Scalp

The scalp is made up of five layers:

  1. Skin
  2. Connective tissue / superficial fascia
  3. Epicranial aponeurosis
  4. Loose areolar tissue
  5. Pericranium

1. Skin

  • Skin of scalp is hairy.
  • It is adherent to the epicranial aponeurosis through the dense superficial fascia.
  • Contains numerous:
    • Hair follicles.
    • Sweat glands.
    • Sebaceous glands.

2. Connective Tissue / Superficial Fascia

  • More fibrous and dense in the centre than at the periphery of the head.
  • Contains many blood vessels.
  • Binds the skin to the subjacent aponeurosis.
  • Provides the proper medium for passage of:
    • Vessels.
    • Nerves.

3. Epicranial Aponeurosis

  • Also called galea aponeurotica.
  • Freely movable on the pericranium along with the overlying and adherent skin and fascia.

Anteriorly

  • Receives insertion of the frontalis.
  • Continues into the upper eyelid.

Posteriorly

  • Receives insertion of the occipitalis.
  • Attached to the external occipital protuberance.
  • Attached to the highest/superior nuchal lines between the occipital bellies.

On Each Side

  • Attached to the superior temporal line.
  • Sends down a thin expansion which passes over the temporal fascia.
  • Attached to the zygomatic arch.

Occipitofrontalis Muscle

  • Has two bellies:
    1. Occipital / occipitalis
    2. Frontal / frontalis
  • Both are inserted into the epicranial aponeurosis.

Occipital Bellies

  • Small.
  • Each arises from the lateral 2/3rd of the superior nuchal line.
  • Supplied by the posterior auricular branch of the facial nerve.

Frontal Bellies

  • Longer and wider.
  • Partly united in the median plane.
  • Each arises from the skin of the upper eyelid and forehead.
  • Mingle with:
    • Orbicularis oculi.
    • Corrugator supercilii.
  • Supplied by the temporal branch of the facial nerve.
  • Muscle raises the eyebrows.
  • Causes horizontal wrinkles in the skin of the forehead.

4. Loose Areolar Tissue

  • Extends anteriorly into the eyelids because the frontalis muscle has no bony attachment.
  • Posteriorly → extends up to the highest/superior nuchal lines.
  • On each side → extends to the superior temporal lines.
  • Gives passage to emissary veins.
  • Emissary veins connect extracranial veins to intracranial venous sinuses.

5. Pericranium

  • Pericranium is the periosteum of the skull bones.
  • It is loosely attached to the surface of the bones.
  • It is firmly attached to the sutures where the sutural ligaments bind the pericranium to the endocranium.

Surgical Layers of Scalp

  • The first three layers of the scalp are called the surgical layers of the scalp.
  • They are also called the “scalp proper.”
  1. Skin
  2. Subcutaneous connective tissue
  3. Epicranial aponeurosis

4 Superficial Temporal Region

It is the area between the superior temporal line and the zygomatic arch.

Layers

  1. Skin
  2. Superficial fascia
  3. Thin extension of epicranial aponeurosis
    • Gives origin to extrinsic muscles of the auricle.
  4. Temporal fascia
  5. Temporalis muscle
  6. Pericranium.
  • Tempus means time.
  • Greying of hair first starts here.

5 Arterial Supply of Scalp and Superficial Temporal Region

In Front of Auricle

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

Behind Auricle

  1. Posterior auricular artery
  2. Occipital artery (tortuous).

Origin of Arteries

  • Supratrochlear and supraorbital arteries:
    • Branches of the ophthalmic artery.
    • Ophthalmic artery is a branch of the internal carotid artery.
  • Superficial temporal artery:
    • Smaller terminal branch of the external carotid artery.
  • Posterior auricular and occipital arteries:
    • Branches of the external carotid artery.
  • Thus, scalp has a rich blood supply derived from both:
    • Internal carotid artery.
    • External carotid artery.
  • The two arterial systems anastomose over the temple.

6 Venous Drainage

Veins of the scalp accompany the arteries and have similar names.

1. Supratrochlear and Supraorbital Veins

  • Unite at the medial angle of the eye.
  • Form the angular vein.
  • Angular vein continues down as the facial vein.

2. Superficial Temporal Vein

  • Descends in front of the tragus.
  • Enters the parotid gland.
  • Joins the maxillary vein to form the retromandibular vein.
  • Retromandibular vein divides into two divisions:

a. Anterior Division

  • Unites with the facial vein.
  • Forms the common facial vein.
  • Common facial vein drains into the internal jugular vein.

b. Posterior Division

  • Unites with the posterior auricular vein.
  • Forms the external jugular vein.
  • External jugular vein ultimately drains into the subclavian vein.
  • Occipital veins terminate in the suboccipital venous plexus.

3. Emissary Veins

  • Connect extracranial veins with intracranial venous sinuses.
  • Help to equalise pressure.
  • These veins are valveless.

Parietal Emissary Vein

  • Passes through the parietal foramen.
  • Enters the superior sagittal sinus.

Mastoid Emissary Vein

  • Passes through the mastoid foramen.
  • Reaches the sigmoid sinus.

Extracranial infections may spread through these veins to the intracranial venous sinuses.

4. Diploic Veins

  • Start from the cancellous bone within the two tables of skull.
  • Carry newly formed blood cells into the general circulation.
  • There are four veins on each side.

a. Frontal Diploic Vein

  • Emerges at the supraorbital notch.
  • Opens into the supraorbital vein.

b. Anterior Temporal Diploic Vein

  • Ends in:
    • Anterior deep temporal vein, or
    • Sphenoparietal sinus.

c. Posterior Temporal Diploic Vein

  • Ends in the transverse sinus.

d. Occipital Diploic Vein

  • Opens either into:
    • Occipital vein, or
    • Transverse sinus near the median plane.

7 Lymphatic Drainage of Scalp

Anterior Part

  • Drains into:
    • Preauricular lymph nodes, or
    • Parotid lymph nodes.
  • These nodes are situated on the surface of the parotid gland.

Posterior Part

  • Drains into:
    • Posterior auricular / mastoid lymph nodes.
    • Occipital lymph nodes.

8 Nerve Supply of Scalp and Temple

  • Scalp and temple are supplied by 10 nerves on each side.
  • Five nerves enter the scalp in front of the auricle:
    • Four sensory.
    • One motor.
  • Remaining five nerves enter the scalp behind the auricle:
    • Four sensory.
    • One motor.

In Front of Auricle

Sensory Nerves

  1. Supratrochlear nerve
    • Branch of frontal nerve.
    • Frontal nerve is from the ophthalmic division of trigeminal nerve.
  2. Supraorbital nerve
    • Branch of frontal nerve.
    • Frontal nerve is from the ophthalmic division of trigeminal nerve.
  3. Zygomaticotemporal nerve
    • Branch of zygomatic nerve.
    • Zygomatic nerve is from the maxillary division of trigeminal nerve.
  4. Auriculotemporal nerve
    • Branch of mandibular division of trigeminal nerve.

Motor Nerve

  1. Temporal branch of facial nerve.

Behind Auricle

Sensory Nerves

  1. Posterior division of great auricular nerve
    • C2, C3.
    • From cervical plexus.
  2. Lesser occipital nerve
    • C2.
    • From cervical plexus.
  3. Greater occipital nerve
    • C2.
    • Dorsal ramus.
  4. Third occipital nerve
    • C3.
    • Dorsal ramus.

Motor Nerve

  1. Posterior auricular branch of facial nerve.

9 Clinical Anatomy of Scalp

1. Sebaceous Cysts

  • Because of the abundance of sebaceous glands, scalp is a common site for sebaceous cysts.

2. Black Eye

  • Collection of blood in the layer of loose connective tissue causes generalised swelling of the scalp.
  • Blood may extend anteriorly:
    • Into the root of the nose.
    • Into the eyelids.
  • This occurs because the frontalis muscle has no bony origin.
  • This results in a black eye.
  • The posterior limit of such haemorrhage is not seen.
  • If bleeding is due to local injury, the posterior limit of haemorrhage is seen.

3. Wounds of Scalp — Gaping

  • Wounds of scalp gape when the epicranial aponeurosis is divided transversely.
  • Such wounds require careful stitching of the aponeurotic layer.

4. Profuse Bleeding from Scalp Wounds

  • Scalp wounds bleed profusely because vessels are prevented from retracting by the fibrous fascia in the second layer of scalp.
  • Bleeding can be arrested by applying pressure at the site of injury using a tight cotton bandage against the bone.

5. Subcutaneous Haemorrhage

  • Because of the density of fascia:
  • Subcutaneous haemorrhages are never extensive.
  • Inflammations in this layer cause little swelling but much pain.

6. Cephalhaematoma

  • Pericranium is adherent to sutures.
  • Therefore, collections of fluid deep to the pericranium, called cephalhaematoma, take the shape of the bone concerned when there is a fracture of a particular bone.

7. Safety-Valve Haematoma

  • Fractures of the cranial vault cause escape of intracranial haematoma into the sub-aponeurotic space of the scalp through fracture lines.
  • This prevents compression of the cerebrum.
  • Collection of blood in the sub-aponeurotic space is called safety-valve haematoma.

8. Dangerous Area of Scalp

  • The layer of loose areolar tissue is a dangerous area of the scalp.
  • Emissary veins connect the veins of this layer with the dural venous sinuses.
  • Therefore, infection of the loose areolar tissue layer may easily spread to the dural venous sinuses.
  • It may lead to thrombosis of the venous sinuses, which may be fatal.
  • Because of the spread of blood, compression of the brain is not seen.
  • Therefore, this layer is also called the safety layer.

9. Healing of Avulsed Scalp

  • Blood supply of the scalp and superficial temporal region is very rich.
  • Therefore, avulsed portions need not be cut away.
  • They can be replaced in position and stitched.
  • They usually take up and heal well.

10. Healing of Avulsed Scalp — Anastomotic Blood Supply

  • Scalp and superficial temporal region are richly supplied by anastomosing vessels.
  • Therefore, an avulsed portion need not be cut.
  • It can be placed in position and stitched.
  • It usually heals.

11. Caput Succedaneum

  • It is a subcutaneous oedema of the scalp produced during delivery.
  • It occurs due to interference with venous return during passage of the head through the birth canal.
  • It usually subsides on its own within a few days.