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The Scalp
It is a 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 :
Skin
Connective tissue layer
Aponeurotic layer - Galea aponeurotica with occipitofrontalis muscle.
Loose areolar layer
Pericranium
Skin - Thick with 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.
Occipitofrontalis muscle or epicranius :
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.
Galea aponeurotica or eicranial 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.
Loose areolar layer or 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.
Sometimes fracture of skull 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. Follow me in blogspot - [ Ссылка ] _________________________________________________________________________________________________________________ Visit my blogs - [ Ссылка ]
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