Al – Rafidain University College General Anatomy Dr. Haydar Munir Salih Lec.6 B.D.S. , F.I.B.M.S. (PhD) THE SCALP The soft tissue covering the vault of skull is termed as SCALP Extent Anterior : Supraciliary arches. Posterior : External occipital protuberance and superior nuchal lines. Lateral : Zygomatic arch and upper border of external acoustic meatus, on each side. Layers of Scalp The soft tissues of the scalp are arranged in five layers: S : Skin C : Connective tissue A : Aponeurosis L : Loose areolar tissue P : Periosteum The skin and superficial fascia of scalp continue in front over the forehead and behind over the back of neck. 1. Skin: Skin of the scalp is thick and richly supplied with hairs, sweat glands and sebaceous glands. It has about 1,200,000 hairs. 2. Connective tissue: subcutaneous tissue consists of lobules of fat bounded in tough fibrous septae which form a very dense network. It is adherent to the skin above and to the underlying aponeurosis. Blood vessels of the scalp lie in this layer. Any injury here results in failure of the lumen of blood vessels to retract because their walls are adherant to the underlying connective tissue. As a result, lacerations of the scalp bleed profusely. LEC: 6 GENERAL ANATOMY By Dr. Haydar Munir Salih. B.D.S., F.I.B.M.S 3. Aponeurotic layer: It is formed by the aponeurosis of occipito-frontalis muscle over the dome of the skull. Occipitofrontalis muscle: It originates from 2 parts: a. Occipital bellies: Muscular fibers arise from the lateral 2/3rd of highest nuchal lines on either side and adjacent mastoid part of temporal bone. b. Frontal bellies: The fibers are attached to the skin of the eye brows and root of nose. It does not have any bony attachment. The fibers from both the bellies are inserted into a central fibrous layer known as the galea aponeurotica or epicranial aponeurosis. Extent of Galea Aponeurotica Anterior: It begins at the coronal suture and extents over the frontal bellies till the eyebrows. A part of the fibrous tissue extends upto the root of nose as a median prolongation. Posterior: It blends with the occipital bellies and extends further to attach over the external occipital protuberance and highest nuchal lines on either side. Lateral: It extends over the temporal fascia and thins out to attach to the zygomatic arch. The superficial fascia connects the apponeurosis to the skin above while it is separated from the periosteum by the layer of loose areolar tissue. 4. Loose areolar tissue: It lies beneath the aponeurotic layer and accounts for the mobility of scalp on the underlying bone. It is limited posteriorly upto the posterior attachment of occipitofrontalis muscle but anteriorly it continues below the muscle over the forehead till the eyebrows. It is in this plane that the surgeons mobilize scalp flaps for reconstructive surgery. 5. Periosteum: It is the pericranium covering the skull bones and is adherent at the suture-lines of the skull. 2 LEC: 6 GENERAL ANATOMY By Dr. Haydar Munir Salih. B.D.S., F.I.B.M.S Arterial Supply of Scalp: The scalp is richly supplied by blood vessels which form an anastomosis in the subcutaneous tissue. Each half of the scalp is supplied by branches of the following five arteries. In front of the ear: Three in number: 1. Supra trochlear artery, branch of ophthalmic artery. 2. Supra orbital artery, branch of ophthalmic artery. 3. Superficial temporal artery, branch of external carotid artery. Behind the ear: Two in number: 4. Posterior auricular artery, branch of external carotid artery. 5. Occipital artery, branch of external carotid artery. Venous Drainage of Scalp: The veins accompany arteries and form an interconnecting network over the scalp. They are: 1. Supratrochlear and supraorbital veins: They join to form the angular vein at the medial angle of eye and further continue as the facial vein. 2. Superficial temporal vein: It forms the retromandibular vein after joining with maxillary vein. 3 LEC: 6 GENERAL ANATOMY By Dr. Haydar Munir Salih. B.D.S., F.I.B.M.S 3. Posterior auricular vein: It joins the posterior division of rectromandibular vein and forms the external jugular vein. 4. Occipital vein: Terminates into suboccipital plexus of veins. Emissary veins: These are veins that connect the intracranial dural venous sinuses to the external veins of the scalp and face. Emissary veins of scalp are: 1. Parietal and mastoid emissary veins which connects occipital vein to sagittal and sigmoid sinuses respectively. 2. Emissary vein from facial vein to cavernous sinus. Lymphatic Drainage of Scalp: Scalp is drained by the following lymph nodes: 1. Pre-auricular lymph nodes: These drain anterior part of scalp, except an area below the centre of forehead. 2. Post auricular lymph nodes: These drain posterior part of scalp. 3. Occipital lymph nodes: A part of posterior aspect of scalp is drained by these nodes also. Nerve Supply of Scalp: 4 LEC: 6 GENERAL ANATOMY By Dr. Haydar Munir Salih. B.D.S., F.I.B.M.S 1. Sensory supply: Each half of the scalp is supplied by 8 sensory nerves. In front of the ear: These are four in number. All are branches of the trigeminal nerve. 1. Supratrochlear nerve 2. Supraorbital nerve 3. Zygomaticotemporal nerve 4. Auriculotemporal nerve Behind the ear: These are also four in number and arise from the cervical plexus. 5. Great auricular nerve (C2, 3) 6. Lesser occipital nerve (C2) 7. Greater occipital nerve (C2) 8. Third occipital nerve (C3) 2. Motor supply: Each half of the scalp is supplied by branches of facial nerve. a. Temporal branch of facial nerve: Supplies the frontal belly of occipitofrontalis muscle. b. Posterior auricular branches of the facial nerve: Supplies the occipital belly of occipito-frontalis muscle. 5 .