Scalp

Scalp

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  Scalp
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  The Scalp It isa soft tissue covering the calvaria of the skull. Extent : • Anteriorly - supraorbital margins • Posteriorly - External occipital protuberance & superior nuchal line • Laterally - zygomatic arch, here it overlaps the temporal region superficial to temporal fascia. Layers : 1. Skin 2. Connective tissue layer 3. Aponeurotic layer - Galea aponeurotica with occipitofrontalis muscle. 4. Loose areolar layer 5. Pericranium
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  Skin - • Thickwith numerous hairs, sweat and sebaceous glands. • It is one of the commonest site for sebaceous cyst. Connective tissue layer - • It is composed of dense fibro - fatty layer. • It connects the skin to the underlying galea. • It contains large blood vessels and nerves. • The walls of the blood vessels are closely adherent to the fibrous tissue, so when the vessels are torn in an open wound, produce profuse bleeding, as the adherence prevent retraction. Bleeding can be arrested by applying pressure against the underlying bone. • Subcutaneous haemorrhage in a closed wound is localised in extent. • Inflammation in this layer is so painful, due to unyielding nature of the fibrous tissue. • Rich blood supply of scalp ensure good healing even a large area is avulsed with narrow pedicle, when replaced and sutured.
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  Occipitofrontalis muscle orepicranius : It consists of a pair of occipital bellies behind and a pair of frontal bellies in front. Occipital bellies - widely separated from each other. • Origin - from lateral 2/3 of superior nuchal line • Insertion - to epicranial aponeurosis or galea aponeurotica • Nerve supply - by posterior auricular branch of facial nerve Frontal bellies - have no bony origin. They are longer, wider and approximated to each other in the median plane. • Origin - from skin & subcutaneous tissue of eyebrow and root of nose • Insertion - to epicranial aponeurosis. • Nerve supply - by temporal branch of facial nerve. • Action - Alternate contraction of occipital and frontal bellies move the entire scalp backward and forwards Frontal bellies - acting from above - raises the eyebrow as in surprise or horror. acting from below - produces transverse wrinkles on forehead as in freight. Temporo-parietalis: It is a variable slip of muscle between auricularis anterior and auricularis superior. • Origin - from galea aponeurosis • Insertion - to the root of auricle. • Nerve supply - by temporal branch of facial nerve • Action - raises the auricle.
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  Galea aponeurotica oreicranial aponeurosis : • It is a sheet of fibrous tissue which connects the occipitalis and frontalis muscles. • Extent - • Posterior - attached to external occipital protuberance and highest nuchal lines. • Anterior - sends narrow extension between the two frontal bellies and blends with the subcutaneous tissues at root of nose. • On each side - it extends as a thin membrane superficial to temporal fascia. It is attached to zygomatic arch. • It gives attachments to auricularis muscles and temporo-parietalis muscles. • When it is divided transversely, the wound will gape.
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  Loose areolar layeror subaponerotic layer : • It consists of loose areolar tissue and forms a potential space. • This has emissary veins, which are valveless, connects the veins of scalp and intracranial venous sinuses. • Any infection in the scalp will be carried intracranial, • hence this layer is called dangerous area of scalp. Any blow on the skull produces collection of blood, which is generalised affecting the whole dome of skull. The blood slowly gravitates into the eyelids, as frontal bellies has no bony attachments. This is called black eye.
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  Sometimes fracture ofskull is associated with a tear in pericranium and dura mater. In such cases the intracranial haemorrhage communicates with the subaponeurotic space through the fracture line. Signs of cerebral compression does not develop until this space is full. This is called as safety - valve haematoma. Traumatic cephalo-hydrocoele is a condition in which the space is filled with cerebrospinal fluid. This is due to fracture of skull associated with tear in meninges of the brain. Caput succedaneum is present in newborn. It is a temporary swelling, affecting the scalp due to interference of venous return occurs during the process of delivery. Pericranium : It is the outer periosteum of the skull. It loosely covers the skull bones except at the sutures, where it becomes continuous with endocranium derived from the endosteal layer of dura mater through the sutural ligaments. Cephalhaematoma - collection of blood beneath the pericranium, assume the shape of the affected bone.
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  Nerve Supply : Scalpis supplied by ten nerves on each side, five in front of auricle and five behind the auricle Source Infront of auricle Source Behind the auricle Sensory Motor Sensory Motor Ophthalmic division of trigeminal nerve Frontal Nerve Supratrochlear nerve Temporal branch of facial nerve C2,C3 of cervical plexus Posterior branch of Great auricular nerve Posterior auricular branch pf facial nerve Supra orbital nerve C2 of cervical plexus Lesser occipital nerve Maxillary division of trigeminal nerve Zygomatic Nerve Zygomatico- temporal nerve dorsal ramus of C2 nerve Greater occipital nerve Mandibular division of trigeminal nerve Auriculo-temporal nerve dorsal ramus of C3 nerve third occipital nerve Applied Anatomy - Surgeries on the scalp should be preferably done under general anaesthesia, as the dermatomes of trigeminal and cervical nerves overlap considerably and the density of fibrous tissue prevents the diffusion of local anaesthetic in the scalp
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  Nerves and Arteriesof Scalp
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  Arterial supply: Fivesets of arteries supply on each side, three in front and two behind the auricle. Source In front of auricle Source Behind the auricle Internal carotid artery ophthalmic artery supra trochlear artery External carotid artery Posterior auricular artery supraorbital artery Occipital artery External carotid artery terminal branch superficial temporal artery Importance: Scalp is the site where there is free anastomosis of branches of External and Internal carotid arteries.
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  Venous Drainage: Veinscorresponds the arteries. They drain as follows: 1. supra orbital vein joins with the supra trochlear vein to form angular vein at the medial angle of eye. 2. Angular vein continues across down the face as facial vein. 3. The superficial temporal vein enters the parotid gland, joins with maxillary vein to form retromandibular vein. This vein divides into anterior and posterior divisions. 4. The anterior division joins with facial vein forming the common facial vein, terminating into internal jugular vein. 5. The posterior division joins with posterior auricular vein to form external jugular vein, terminating into subclavian vein. 6. Occipital vein draining into sub occipital plexus of veins.
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  Lymphatic drainage: • Anteriorpart of scalp drains into pre auricular or superficial parotid lymph nodes. • Posterior part of scalp drains into post auricular or mastoid group and occipital group of lymph nodes.