M01.02.001 The Scalp

The Scalp: Layers, Blood Supply, and Nerves

The scalp is more than just hair! It’s a complex structure of five distinct layers protecting the underlying skull. Understanding these layers and their functions is crucial in medicine.

Layers of the Scalp (Remember with SCALP):

• Skin: The outermost layer, rich in hair follicles and sebaceous glands.
• Dense Connective Tissue: This well-vascularized and innervated tissue connects the skin to the aponeurosis. This layer’s tight adherence to blood vessels can lead to profuse bleeding from scalp wounds.
• Epicranial Aponeurosis: A thin, tough sheet connecting the frontalis and occipitalis muscles (responsible for scalp movement).
• Loose Areolar Connective Tissue: A critical “danger area” containing emissary veins that connect scalp veins to the skull’s interior. Infections here can potentially spread to the brain.
• Periosteum: The tough outer layer of the skull bones, continuous with the inner endosteum at suture lines.

Blood Supply: A Rich Network

The scalp boasts a rich blood supply from two main sources:

• External Carotid Artery: Supplies the scalp through the superficial temporal, posterior auricular, and occipital arteries.
• Ophthalmic Artery (Internal Carotid Branch): Supplies the anterior scalp via the supraorbital and supratrochlear arteries.

Drainage System: Superficial and Deep

The scalp’s venous drainage can be categorized as:

• Superficial Drainage: Mirrors the arterial supply with superficial temporal, occipital, and other veins draining into the external jugular vein.
• Deep Drainage: The temporal region drains into the pterygoid venous plexus, which connects to the maxillary vein.

Nerves: Feeling the Scalp

Sensory information from the scalp travels through various nerves:

• Trigeminal Nerve Branches: Supratrochlear, supraorbital, zygomaticotemporal, and auriculotemporal nerves supply the forehead, temple, and anterior scalp.
• Cervical Nerve Branches: Lesser occipital, greater occipital, great auricular, and third occipital nerves supply the posterior and lateral scalp.

Clinical Relevance: Scalp Lacerations

Deep scalp cuts can bleed significantly due to several factors:

• Muscle Tension: The occipitofrontalis muscle can pull, preventing blood vessel closure.
• Limited Vessel Contraction: Tight connective tissue hinders the normal blood vessel constriction response to injury.
• Abundant Blood Flow: The numerous connections (anastomoses) between scalp vessels contribute to profuse