Epicranial

Epicranial refers to the epicranium, the upper portion of the skull that includes the calvaria and its scalp coverings. In anatomy, the term is commonly used for structures associated with the epicranium, most notably the galea aponeurotica, or epicranial aponeurosis, a broad fibrous sheet that covers the calvaria and connects the frontal and occipital muscle groups.

Anatomy and relations: The galea aponeurotica lies between the frontalis muscle anteriorly and the occipitalis muscle posteriorly. It extends laterally and fuses with surrounding temporalis fascia, enabling coordinated movement of the scalp. The scalp itself is traditionally described in five layers, remembered by the mnemonic S-C-A-L-P: skin, dense connective tissue, epicranial aponeurosis, loose areolar tissue, and pericranium. The epicranial aponeurosis is the third layer and serves as a central tendon-like structure for the muscles of facial expression.

Nerve and blood supply: Anterior scalp regions are supplied by branches of the trigeminal nerve, while the posterior scalp receives innervation from cervical nerves, including the greater occipital nerve. Blood supply comes from branches of the external carotid artery, notably the superficial temporal, posterior auricular, and occipital arteries.

Clinical relevance: The galea allows the frontalis and occipitalis muscles to move the scalp as a unit. The loose areolar layer beneath the epicranial aponeurosis is a potential space; infections or hemorrhages can spread within the scalp, and subaponeurotic hemorrhage can occur in infants.