Scalp
Five-layered soft tissue covering the skull vault. Its rich blood supply makes lacerations bleed heavily, and its loose areolar "danger layer" lets infection spread into the skull.
Core anatomy
- Location
Over the cranial vault from the eyebrows to the superior nuchal lines, and laterally to the zygomatic arches.
- Parts
- S — Skin: thick, hair-bearing, with many sebaceous glands
- C — Connective tissue (dense): contains the vessels and nerves; fibrous septa hold vessel walls open, so cut vessels gape and bleed profusely
- A — Aponeurosis (galea aponeurotica): joins the frontal and occipital bellies of occipitofrontalis
- L — Loose areolar tissue: the "danger layer"; allows the upper three layers to move, and blood or pus spreads freely within it (subgaleal hemorrhage)
- P — Pericranium: periosteum of the skull, attached at the sutures (limits cephalohematoma to one bone)
- Relations
The first three layers are firmly bound together and move as one ("scalp proper").
- Arterial supply
Branches of the external carotid (superficial temporal, posterior auricular, occipital) and the internal carotid via the ophthalmic artery (supratrochlear, supraorbital); extensive anastomoses.
- Venous drainage
Veins accompanying the arteries; emissary veins in the danger layer connect scalp veins with the intracranial dural venous sinuses.
- Lymphatic drainage
Occipital, posterior auricular (mastoid), preauricular (parotid) and submandibular nodes (see cervical lymph nodes).
- Innervation
Anteriorly branches of the trigeminal nerve (supratrochlear, supraorbital, zygomaticotemporal, auriculotemporal); posteriorly the greater occipital nerve (C2) (greater occipital nerve), lesser occipital and great auricular nerves (cervical plexus) and third occipital nerve.
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Clinical correlations
Scalp lacerations PANCE
- Mechanism / lesion
The dense connective tissue holds vessels open.
- Classic presentation
Heavy bleeding (significant blood loss possible in children and anticoagulated patients). Control with direct pressure and closure; repair a gaping galea to restore frontalis function and hemostasis.
Subgaleal hemorrhage and cephalohematoma PANCE
- Mechanism / lesion
Subgaleal bleeding (in the loose areolar layer), e.g. after vacuum-assisted delivery, can spread over the whole vault; cephalohematoma is subperiosteal, so it is limited by suture lines.
- Classic presentation
Subgaleal hemorrhage — a fluctuant swelling crossing sutures that can cause hypovolemic shock in newborns. Cephalohematoma — a firm swelling over one bone appearing hours after birth, risk of jaundice. Caput succedaneum — scalp edema crossing sutures, present at birth, resolves in days.
Spread of infection via emissary veins
- Mechanism / lesion
Infection in the danger layer can travel through valveless emissary veins to the dural venous sinuses.
- Classic presentation
Meningitis or venous sinus thrombosis after scalp infection (rare).
High-yield PANCE pearls
- Scalp layers: Skin, Connective tissue, Aponeurosis, Loose areolar, Pericranium.
- Cephalohematoma doesn't cross sutures; caput succedaneum and subgaleal hemorrhage do.
- Subgaleal hemorrhage in a newborn can cause shock.
Imaging anatomy
- CT
Head CT shows subgaleal hematoma and underlying fractures after trauma.
- Ultrasound
Distinguishes scalp collections in neonates.
Physical exam
- Palpation
In a newborn, a swelling limited to one bone and not crossing sutures = cephalohematoma; a boggy swelling crossing sutures = caput or subgaleal hemorrhage (monitor hemoglobin and head circumference).
- Strength / function testing
Explore lacerations for galeal tears and underlying fracture.
Self-quiz
A newborn delivered by vacuum extraction develops a boggy, fluctuant scalp swelling that crosses suture lines and increases over several hours, with tachycardia and pallor. Which layer contains the bleeding?
Correct answer: C
Subgaleal hemorrhage lies in the loose areolar tissue beneath the galea, which is not limited by sutures and can hold a large volume of blood, causing shock. A cephalohematoma is subperiosteal and limited by sutures.
Show answer
C
Subgaleal hemorrhage lies in the loose areolar tissue beneath the galea, which is not limited by sutures and can hold a large volume of blood, causing shock. A cephalohematoma is subperiosteal and limited by sutures.
Why do scalp lacerations bleed so heavily?
Correct answer: B
In the dense connective tissue layer, vessel walls are attached to fibrous septa, so cut vessels can't retract and constrict — they gape and bleed profusely.
Show answer
B
In the dense connective tissue layer, vessel walls are attached to fibrous septa, so cut vessels can't retract and constrict — they gape and bleed profusely.
A newborn has a firm scalp swelling over one parietal bone that stops sharply at the sutures. Which lesion is this?
Correct answer: C
A cephalohematoma is subperiosteal, and the pericranium is attached at the sutures, so it is limited to one bone. Caput succedaneum and subgaleal hemorrhage both cross suture lines.
Show answer
C
A cephalohematoma is subperiosteal, and the pericranium is attached at the sutures, so it is limited to one bone. Caput succedaneum and subgaleal hemorrhage both cross suture lines.