Summary
Highlights
Dr. Hemin Rasuman Sharif introduces his lecture on head and neck anatomy, focusing on the face, scalp, skin, and superficial fascia of the neck. He outlines the discussion points for facial anatomy, including the skin, superficial fascia, muscles of facial expression, blood supply, nerve supply, and lymphatic drainage.
The skin of the face has characteristics like sweat glands, sebaceous glands, hair, and Langer's lines (resting skin tension lines) that influence wrinkle patterns. Beneath the skin lies the superficial fascia, which contains muscles of facial expression, blood vessels, nerves, lymph nodes, and glands. Unlike other body parts, the face's superficial fascia contains a membranous structure called SMAS (Superficial Musculoaponeurotic System), allowing delicate muscle movements for expressions.
Muscles of facial expression originate from bone or fascia and insert into the skin, enabling diverse facial movements. Examples include Orbicularis Oculi (sphincter around the eyes) which has thin palpebral and thicker orbital parts for blinking, and Orbicularis Oris (around the mouth). Other muscles like frontalis and occipitalis work together to move the eyebrows and create forehead wrinkles. The corrugator supercilii, procerus, and platysma (a thin sheet in the neck) also contribute to facial expressions like frowning and lower lip movement. All these muscles are supplied by the facial nerve.
The face primarily receives blood supply from branches of the external carotid artery (facial artery, transverse facial artery, maxillary artery, zygomaticofacial artery). A smaller supply comes from the internal carotid artery via ophthalmic branches (supraorbital, supratrochlear, infratrochlear, dorsal nasal arteries). Venous drainage largely goes to the internal jugular vein. Important connections exist between facial veins and the cavernous sinus (via the ophthalmic vein), posing a risk of intracranial infection from facial infections.
Lymphatic drainage from the face mainly goes to submental, submandibular, pre-auricular, and parotid lymph nodes before reaching deeper systems. Sensory nerve supply to the face and anterior scalp is from branches of the trigeminal nerve (ophthalmic, maxillary, mandibular divisions). A small area of the mandible and ear is supplied by the great auricular nerve from the cervical plexus. Motor nerve supply is primarily from the facial nerve, which divides into five branches within the parotid gland to innervate facial expression muscles. Muscles of mastication are supplied by the mandibular division of the trigeminal nerve.
The scalp is a multi-layered soft tissue structure covering the cranium, extending from the supraciliary arch to the superior nuchal line and external occipital protuberance. It consists of five layers: Skin (hair-bearing), Connective tissue, Aponeurosis (galea aponeurotica), Loose areolar tissue, and Pericranium. The pericranium adheres tightly to the bone. The loose areolar tissue is a pliable, avascular potential space where hematomas collect and is used for surgical dissection. The galea aponeurotica is a strong sheet connecting frontal and occipital muscles, and laterally merges with the superficial temporal fascia.
The scalp has a rich blood supply from six sources: supratrochlear, supraorbital (from internal carotid), zygomaticotemporal, superficial temporal, posterior auricular, and occipital arteries (from external carotid). Superficial temporal and occipital arteries provide substantial supply, capable of sustaining the entire scalp alone. Sensory innervation comes from six nerves: supratrochlear, supraorbital, zygomaticotemporal (corresponding to artery names), auriculotemporal, lesser occipital, and greater occipital nerves. Venous drainage mirrors the arterial supply.
The neck is defined as the region between the lower margin of the mandible and superior nuchal line (posteriorly) and the suprasternal notch and clavicle (inferiorly). It is anatomically significant due to the high concentration of vital structures in a confined space, necessitating a thorough understanding of its anatomy.
The skin of the neck has Langer's lines that run horizontally, making horizontal incisions cosmetically preferable to vertical ones. Cutaneous nerve supply varies: the back of the neck and posterior scalp (up to the vertex) are supplied by posterior rami of cervical nerves C2-C5. The front and sides of the neck are supplied by anterior rami of cervical spinal nerves C2-C4 through the cervical plexus. The face, forehead, and anterior scalp receive innervation from branches of the trigeminal nerve.
Key cutaneous nerves of the neck include the greater occipital, lesser occipital, great auricular, transverse cutaneous of the neck, and supraclavicular nerves (divided into medial, intermediate, and lateral branches). These nerves originate from cervical spinal nerves (C2-C5). The superficial fascia of the neck is a thin layer underlying the skin, investing the platysma muscle, and containing cutaneous nerves, superficial veins (external and anterior jugular veins and their tributaries), and superficial lymph nodes. The platysma muscle, located in this fascia, is also a muscle of facial expression.