TOPIC- SCALP

Definition: 

The scalp is the soft tissue that covers the vault of the skull. It is the hair-bearing area of the skull.

Extent:

Anteriorly: To the supraorbital margins.

Posteriorly:  To the highest nuchal line.

On each side: To the superior temporal lines.

Layers of Scalp: It consists of five layers:-

S-Skin

C-connective tissue (superficial fascia)

A-aponeurosis (galea aponeurotica)

L-loose areolar tissue

P-pericranium

SKIN:

The skin is thick and hairy. It is adherent to the epicranial aponeurosis through the dense superficial fascia.  It consists of abundance sebaceous glands.

SUPERFICIAL FASCIA:

It is more fibrous and dense in the center than at the periphery of the head. It provides the proper medium for passage of vessels and nerves of the skin. It binds skin to subjacent aponeurosis.

EPICRANIAL APONEUROSIS:

It is freely movable on the pericranium along with the overlying and adherent scalp and fascia. 

On each side, it is attached to the superior temporal lines.

Anteriorly, it receives the insertion of the frontalis. 

Posteriorly, receives insertion of the occipital bellies.

Frontal belly originates from the skin of the forehead and Occipital belly originate from lateral 2/3 of superior nuchal line.

LOOSE AEREOLAR TISSUE:

It extends:

Anteriorly into the eyelids.

Posteriorly to the highest and superior nuchal lines and

On each side to the superior temporal lines.

It is called dangerous layer of the scalp as the emissary veins open here and may carry infections inside the brain (venous sinus).

PERICRANIUM:

It is loosely attached to the surface of the bones,but is firmly adherent to the sutures where the sutural ligaments bind the pericranium to the endocranium.

ARTERIAL SUPPLY:

IN FRONT OF AURICLE-

Supratrochlear artery

Supraorbital artery

Superficial temporal arteries

BEHIND THE AURICLE-

Posterior auricular artery

Occipital arteries

VENOUS DRAINAGE

• Emissary veins connect the extracranial veins with the intracranial venous sinuses to equalize the pressure.
• The superficial temporal vein joins the maxillary vein to form the retromandibular vein.
• The supratrochlear and the supraorbital vein unite at the medial angle of the eye to form angular vein The posterior division of retromandibular vein unites with the posterior auricular vein to form an external jugular vein.

NERVE SUPPLY:

Scalp supplied by ten nerves on each side.

Five nerves (4 sensory and one motor) enter scalp in front of the auricle.

Remaining five(4 sensory one motor) enter behind the auricle.

IN FRONT OF AURICLE:

Sensory Nerve:

Supraorbital Nerve

Supratrochlear Nerve

Zygomaticotemporal Nerve

Auriculotemporal Nerve

Motor Nerve: Temporal branch of Facial nerve.

BEHIND THE AURICLE:

Sensory Nerve:

Greater Occipital Nerve

Lesser Occipital Nerve

Third Occipital Nerve

Great Auricular Nerve

Motor Nerve: Posterior Auricular of Facial nerve.

LYMPHATIC DRAINAGE:

• Lymph vessels from the frontal region drain into the submandibular nodes.
• Vessels from the rest of the forehead, temporal region, the upper half of the lateral auricular aspect and anterior wall of the external acoustic meatus drain into superficial parotid nodes.
• The occipital region of the scalp is drained by the occipital nodes, and partly by the vessel that runs along the posterior border of the sternocleidomastoid to the lower deep cervical nodes.
• A strip of the scalp above the auricle drains to the upper deep cervical and retro-auricular nodes. The retro-auricular in turn drain to deep cervical.

CLINICAL ANATOMY:

• Due to the presence of numerous sebaceous glands, the scalp is the commonest site for the sebaceous cyst.
• Scalp lacerations bleed profusely because elastic fibers of underlying galea aponeurotic prevent initial vessel retraction, the wounds may be associated with significant blood loss which can result in clinical shock.
• Scalp flaps can be used in craniofacial surgery for correction of congenital deformity, for the release of craniosynostosis, treatment of craniofacial fractures and for repair of scalp defects after excision of skin tumors.
• Failure to control bleeding points as a separate step can result in significant hematomas, often subgaleal, leading to the breakdown of the original wound and sometimes necessitating surgical drainage.