Download The SCALP

The SCALP
By
Prof. Dr. Muhammad Imran Qureshi
The “SCALP” includes FIVE layers external to the Calvaria. These are:
S: Skin & Superficial Fascia
C: Connective Tissue
A: Aponeurosis (Epicranial)
L: Loose areolar Tissue
P: Pericranium (Periosteum)
Figure 1: Layers of the SCALP
The Skin; thick with many close set
hair follicles and their associated
sebaceous and sweat glands, firmly joined
to the next deeper layer.
The Superficial Fascia consists of very
dense Connective Tissue and contains
superficial nerves and vessels in
abundance.
The epicranius or Occipitofrontalis muscle
is made up of two occipitalis and two
frontalis muscles, with their intervening
Aponeurosis, called the galea
Aponeurotica. (Laterally auricular muscles
are also part of this layer)
Figure 2: The Dangerous area
A Loose connective tissue layer. (The danger area of the scalp). Contains a few small
vessels. The nature of this layer permits easy movements of the layers above…which move
as a unit.
The Pericranium (Periosteum) of the calvaria. Except at sutures, it is poorly fixed to bone by
connective tissue fibres (Sharpey’s fibres)
The skin is inseparably attached to the dense connective tissue which makes up the
superficial fascia.
This layer is in turn firmly attached to the Epicranius muscle (comprising of the two frontalis
and two occipitalis muscles and the intervening Galea Aponeurotica)
When the epicranius contracts, movement occurs
in all three layers.
Deep to the epicranius is the layer of Loose
connective tissue upon which the epicranius
moves.
It is here that separation of scalp from
pericranium may occur following laceration.
Thus, large areas of lacerated scalp may hang
grossly over the face or neck, held by an
undamaged pedicle.
The entire scalp can be pulled off if long hair is
caught by power machinery.
Figure 3: Coronal Section of the SCALP
It is known as the danger area because the extravasated blood spreads within it with ease to
form a puddle.
To understand where it spreads, you must have the
knowledge of the attachment of the overlying
epicranius muscle.
Each Occipitalis arises from the Superior Nuchal line
and inserts into the Galea Aponeurotica anteriorly.
Each Frontalis muscle is attached to the Galea
Aponeurotica posteriorly but has no bony attachment
as it descends into the region of the forehead;
Instead, it intermingles with the fibres of the
Orbicularis Oculi, and some of its fibres rather attach
to the skin of the forehead and upper eye lid
(Panniculus Carnosus)
Figure 4: Details of the Layers of the SCALP
Any material of a fluid nature, e.g. Extravasated
blood, in the loose layer cannot track into the neck,
because of the firm attachment of the epicranius to the Superior Nuchal line.
However, it can and does track into the upper eyelids and forehead, resulting into TWO black
eyes.
The scalp covering the lateral side of the head i.e. over the temporal fascia undergoes
changes which hinder and even prevent the passage of extravasated blood towards the
zygomatic arch.
In the coronal section of the scalp and
skull, while there is no change in the
skin as one approaches the zygomatic
arch, the superficial fascia becomes less
dense; the Galea aponeurotica
disappears except for a weak layer of
connective tissue difficult to trace to the
zygomatic arch, and the loose layer
becomes fairly dense and is lost as a
distinct entity. Thus, the element of
danger inherent in looseness is largely
removed.
Figure 5: Attachments of the Frontalis & Occipitalis to the
Galea Aponeurotica
Nerve Supply of the SCALP
Anterior to the Auricle:
Supraorbital and Supratrochlear branches of the Ophthalmic
division of Trigeminal Nerve (Va).
Zygomaticotemporal branch of the Maxillary division of
Trigeminal Nerve (Vb), and the Auriculotemporal branch of
the Mandibular division of Trigeminal Nerve (Vc)
Figure 6: Lateral attachments
of the SCALP
Posterior to the Auricle:
Lesser Occipital nerve (C2) from the Cervical plexus.
Greater Occipital and Third Occipital
from the posterior rami of the second
and third cervical nerves.
All of these nerves with the exception
of the supraorbital and supratrochlear
nerves run most of their courses in the
dense connective tissue.
The supraorbital and supratrochlear
nerves run in the loose areolar tissue
layer deep to the frontalis muscle for a
considerable distance, but ultimately,
Figure 7: Nerve Supply of the SCALP
they pierce the frontalis muscle to enter the dense connective tissue.
Infections in the dense connective tissue elicit much pain because this tissue resists swelling
and thus exerts pressure on the nerves lying within it.
Arterial Supply of the SCALP
Each side of the scalp receives FIVE arteries:
Two small ones, the supratrochlear and supraorbital,
which stem indirectly from internal carotid and
Three large ones, the Superficial Temporal, the
Posterior Auricular and the Occipital, which are direct
branches of the external carotid.
These five branches not only anastomose with each
other but also with those of the opposite side.
These anastomoses assume great importance after
ligation of the common or external carotid artery of
one side.
Figure 8: Arterial Supply of the SCALP
In scalp lacerations, blood may spurt from both ends of the cut arteries due not only to
anastomosis but also to the fact that these anastomosing arteries course in dense connective
tissue which blends with their adventitia and actually tends to hold them when they are cut.
Because of widespread anastomoses of arteries, scalp separations are easily restored unless
the loose flap of scalp has a very small pedicle.
Venous Drainage of the SCALP
Venous channels accompany the five paired
arteries BUT
There are veins which connect scalp veins to
Cranial venous sinuses (Emissary Veins)
Emissary veins are the veins that pass
through various foramina and openings in
the cranial wall and establish anastomoses
between the sinuses of the dura inside and
veins on the exterior of the skull.
Figure 9: Venous Drainage of the SCALP
These veins are not confined to the scalp. They also pass through the foramina in the base of
the skull, bony orbit etc.
They do not have valves. The blood therefore, may flow either into or out of the venous
sinuses.
The emissary veins most intimately related to the
scalp are two parietal, two mastoid and indirectly
the ophthalmic veins.
The two parietal emissary veins pass through
canals in the parietal bones, located on either side
of the Sagittal suture, about an inch anterior to the
lambda.
The mastoid emissary veins are located on either
side of the skull. They pass through the mastoid
foramen which lies posteromedial to the mastoid
notch. They communicate the sigmoid sinus with
the Occipital and posterior auricular veins.
Figure 10: Venous anastomoses between the
veins of the Face with veins of the SCALP &
Cavernous Sinus
Indirect communication may be established
between the Supraorbital and supratrochlear veins
of the scalp and the Cavernous sinus through superior and inferior ophthalmic veins.
Infections of the scalp may spread
through these veins into the meninges
causing meningitis.
Besides, there are Four pairs of Diploic
veins that run in the Diploë. They not
only anastomose with one another but
also with the superficial veins of the
scalp and with the dural venous sinuses.
Figure 11: Doploic Veins
Figure 12: Summery of the Nerve & Arterial Supply of the SCALP