Soft tissue covering the vault (cranial cap) of the skull.

Layers — Mnemonic: SCALP

First 3 layers (S+C+A) = firmly adherent and inseparable = scalp proper (avulsed together in machinery injuries)

Occipitofrontalis Muscle

Arterial Supply (5 arteries per side — all enter from below at periphery)

Supratrochlear + supraorbital = ICA system (ophthalmic artery); other 3 = ECA Scalp = site of collateral anastomosis between ICA + ECA systems All arteries enter from below at periphery → scalp flaps in craniotomy cut centrally, reflected peripherally to preserve blood supply

Venous Drainage

Emissary veins (in dangerous 4th layer):

• Parietal emissary → through parietal foramen → superior sagittal sinus
• Mastoid emissary → through mastoid foramen → sigmoid sinus

Nerve Supply

In front of auricle (4 sensory + 1 motor):

Behind auricle (4 sensory + 1 motor):

Lymphatic Drainage

• Anterior scalp → preauricular (superficial parotid) nodes
• Posterior scalp → posterior auricular (mastoid) nodes + occipital nodes

Layers of Temple (Superficial → Deep)

1. Skin; 2. Connective tissue; 3. Epicranial aponeurosis extension; 4. Temporal fascia (thickest fascia in body; splits inferiorly; used as graft in tympanoplasty); 5. Temporalis muscle; 6. Pericranium

Applied Anatomy

Dangerous layer (4th) — infection spreads via emissary veins → dural venous sinuses → sinus thrombosis (fatal)

Safety-valve haematoma — vault fracture with torn dura + pericranium → intracranial blood enters subaponeurotic space; signs of cerebral compression delayed → called “safety-valve haematoma”

Black eye — blood in 4th layer tracks anteriorly into eyelids (frontalis has no bony anterior attachment) → periorbital ecchymosis after head injury

Cephalohaematoma — subperiosteal blood collection; bounded by suture lines (pericranium firmly attached at sutures) → takes shape of bone; most common parietal; well-defined, firm edges

Caput succedaneum — subcutaneous oedema over presenting head at birth (impeded venous return); crosses suture lines (unlike cephalohaematoma); soft, poorly defined margins; resolves spontaneously

Scalp bleeding — profuse; vessel walls adherent to fibrous C layer → cannot retract; arrested by pressure against bone or tight bandage above ears + eyebrows

Scalp wounds — do not gape unless galea cut transversely (galea under anteroposterior tension from occipitofrontalis)

Definition and Extent

The scalp is the soft tissue covering the vault (cranial cap) of the skull.

Some authorities extend the lateral boundary to the zygomatic arch.

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Layers — Mnemonic: SCALP

Surgical Layers of the Scalp

The first three layers (S + C + A) are firmly adherent and inseparable — collectively called the scalp proper or surgical scalp. These are avulsed together in machinery injuries and scalping.

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Occipitofrontalis Muscle

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Arterial Supply

Five arteries on each side — all enter from below at the periphery.

First two arteries (supratrochlear + supraorbital) = branches of internal carotid artery via ophthalmic artery. Remaining three = branches of external carotid artery. The scalp is therefore a site of collateral anastomosis between internal and external carotid systems.

All arteries enter the scalp from below at the periphery → scalp flaps in craniotomy are cut centrally and reflected peripherally to preserve blood supply.

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Venous Drainage

Five veins on each side, accompanying arteries of same name:

Emissary veins (in the dangerous 4th layer) connect scalp veins to intracranial dural venous sinuses:

• Parietal emissary vein → through parietal foramen → superior sagittal sinus
• Mastoid emissary vein → through mastoid foramen → sigmoid sinus

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Nerve Supply

In front of auricle (4 sensory + 1 motor):

Behind auricle (4 sensory + 1 motor):

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Lymphatic Drainage

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Layers of Temple (Superficial Temporal Region)

Six layers (superficial to deep):

1. Skin
2. Connective tissue
3. Extension of epicranial aponeurosis (gives origin to auricularis anterior and superior)
4. Temporal fascia — thickest fascia in the body; attached above to temporal line, below to zygomatic arch; splits inferiorly into two layers enclosing fat, a branch of superficial temporal artery, and zygomaticotemporal nerve; used as a graft in tympanoplasty
5. Temporalis muscle
6. Pericranium

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Clinical Correlations

Dangerous layer of scalp (4th layer — loose areolar tissue): Infection here spreads via emissary veins → intracranial dural venous sinuses → sinus thrombosis (can be fatal).

Safety-valve hematoma: In vault fractures with torn dura and pericranium, intracranial blood communicates with the subaponeurotic space. Signs of cerebral compression are delayed until this space fills — hence called safety-valve hematoma.

Black eye: Blood in the 4th layer tracks anteriorly into the eyelids (because frontalis has no bony anterior attachment) → periorbital ecchymosis (black eye) after head injury.

Cephalhematoma: Subperiosteal collection of blood. Bounded by suture lines (pericranium is firmly attached at sutures) → hematoma takes the shape of the bone. Common in parietal region. Edges are well-defined and firm.

Caput succedaneum: Subcutaneous oedema over the presenting part of the head at birth due to impeded venous return during passage through the birth canal. Crosses suture lines (unlike cephalhematoma). Soft, poorly-defined margins. Resolves spontaneously.

Scalp bleeding: Profuse because vessel walls are adherent to dense fibrous network of C layer and cannot retract. Arrested by applying pressure against underlying bone or by encircling the head with a tight bandage above the ears and eyebrows.

Scalp wounds: Do not gape unless the epicranial aponeurosis (galea) is divided transversely — because the aponeurosis is under anteroposterior tension from occipitofrontalis.

Sebaceous cysts: Scalp is the commonest site — due to maximum sebaceous glands in the skin (S layer).

Scalp flaps in craniotomy: Incisions made centrally, flaps reflected peripherally — preserves blood supply entering from below at periphery.

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