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 :
1.Skin
2.Connective
tissue layer
3.Aponeurotic
layer - Galea aponeurotica with occipitofrontalis muscle.
4.Loose
areolar layer
5.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
Nerve Supply :
Scalp is supplied by ten nerves on each side, five in front of auricle
and five behind the auricle
Arterial
supply: Five sets of arteries supply on each side, three in front and two
behind the auricle.
Venous Drainage: Veins corresponds 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.
Lymphatic drainage:
•Anterior part 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.
