Scalp Anatomy Overview

Scalp Anatomy

• Extent: Extends from eyebrows to nuchal lines, down to ears and zygomatic arches.
• Forehead Composition: Part of both face and scalp, from eyebrows to hairline.
• Scalp Layers (Mnemonic): Skin, Connective tissue, Aponeurosis with muscle (front and back), Loose areolar tissue, Pericranium.
• Skin Thickness: Thickest in the body (3-7 mm), thickest in occipital region. Significantly thicker than body average (1-2 mm).
• Hair Density: Highly hairy region, with high sebaceous gland concentration.
• Attachment: Firmly attached to underlying muscle and aponeurosis via dense connective tissue.
• Blood Vessels: Run within the firm connective tissue, connecting first and third layers.
• Loose Areolar Tissue: Fourth layer, allows movement of layers over the pericranium (skull's periosteum).
• Pericranium Attachment: Loosely attached to bone, easily detached by hematoma. Strongly attached at sutures.
• Subaponeurotic Space: Loose areolar tissue lying beneath the aponeurosis. Crucial for scalp movement/displacement. Bleeding in this area can lead to "black eyes."

Occipitofrontalis Muscle

• Composition: Occipitalis and frontalis muscular parts, joined by epicranial aponeurosis.
• Occipitalis: Originates from highest nuchal line, inserts into the aponeurosis, laterally blends with temporalis fascia.
• Frontals: Originates from front of aponeurosis, inserts into orbicularis oculi and skin above the eyebrow.
• Midline: Right and left frontalis muscles meet at midline; Occipitalis muscles do not connect.
• Bony Attachment: Occipitalis only; frontalis attaches to aponeurosis and muscle but not bone.
• Nerve Supply: Facial nerve branches - posterior auricular to occipitalis; temporal & zygomatic to frontalis
• Action: Occipitalis pulls scalp back(in some individuals) or anchors aponeurosis; frontalis elevates eyebrows producing forehead wrinkles.

Scalp Blood Supply

• Arteries: Originate from external (occipital, posterior auricular, superficial temporal) and internal (supratrochlear, supraorbital) carotid arteries. Arteries anastomose (connect) freely.
• Anatomic Areas of Most Extensive Anastomosis: Junction of forehead and temple (above eyebrows)
• Attachment Level: Arteries are attached to the deepest layer of the dermis.
• Bleeding: Arteries in scalp wounds bleed profusely due to open vessel endings.
• Bone Blood Supply: Scalping doesn’t cause bone necrosis, which stems from the middle meningeal artery.
• Specific Arteries & Branches: Occipital, posterior auricular, superficial temporal, middle temporal, supraorbital, supratrochlear. Descriptions of where they arise and travel.

Scalp Veins

• Course: Veins run alongside arteries.
• Diploic Veins: Frontal, parietal, and occipital bones provide diploic veins that feed into scalp veins.
• Drainage: Supraorbital and supratrochlear veins drain to angular vein, then to facial vein; superficial temporal veins drain to retromandibular vein; occipital veins drain into plexus around semisptinalis capitis muscle; posterior auricular vein (including mastoid emissary vein from sigmoid sinus).

Scalp Lymph Drainage

• Nodes: No lymph nodes are within the scalp.
• Channels: Lymphatic channels drain to occipital, posterior auricular, preauricular and submandibular (and across the face) nodes outside the scalp.
• Deep Cervical Chain Eventually lymph drains to nodes of deep cervical chain

Scalp Nerve Supply

• Sensory: Posteriorly (greater occipital, third occipital), externally (lesser occipital), temporally (auriculotemporal), zygomaticotemporal, frontally (supratrochlear and supraorbital). Exact pathways and origins described.

Temporal Fossa and Zygomatic Arch

• Temporal Lines: Superior and inferior temporal lines diverge from the frontal bone’s zygomatic process; form a convex curve behind the ear.
• Temporal Fossa: Area defined by temporal lines above and zygomatic arch below. The roof is temporalis fascia, and the floor includes the pterion. Boundaries described including zygomatic bone, processes, supramastoid crest, etc.
• Zygomatic Arch: Formed by temporal and zygomatic bones; completed anteriorly by the zygomatic process of the maxilla.
• Vulnerable Nerves & Vessels: Auriculotemporal nerve and facial nerve (temporal and zygomatic branches) cross arch and are vulnerable in trauma.
• Temporalis Fascia: Attached to superior temporal line and zygomatic arch. The superficial temporal vessels and auriculotemporal nerve rest on this rugged membrane; the middle temporal artery and vein traverse this fascia

Temporalis Muscle

• Origin: Temporal fossa, from inferior temporal line to infratemporal crest.
• Development: Small at birth, grows larger in individuals through life.
• Fiber Direction: Most anterior fibers are vertical; most posterior fibers are horizontal, turning downward over the zygomatic arch root.
• Shape: Large, fan-shaped, converges towards the coronoid process of the mandible.
• Insertion: Into mandibular notch, coronoid process (predominantly bevelled inner plate of mandible, along posterior coronoid process and ascending ramus).
• Blood Supply: From temporal branches of maxillary artery, reinforced by middle temporal artery.
• Nerve Supply: Deep temporal branches of mandibular nerve (sometimes reinforced by middle temporal nerve).
• Action: Elevates mandible (closes jaw); posterior fibers retract the jaw. Only retracting muscle for condyle.

Explore the intricate anatomy of the scalp, covering its extent, composition, and distinct layers. This quiz highlights the key features such as skin thickness, hair density, and vascular structure. Delve into the unique characteristics and functions of each scalp layer through engaging questions.