Scalp Anatomy PDF

Scalp-layers, blood and nerve supply, applied anatomy…10 marks Definition Scalp is the soft tissue cover of the calvaria (skull cap) Extent Antero-posterior extent- from the supra orbital margin to the superior nuchal line Transverse extent-from one zygomatic arch to the oth...

Scalp-layers, blood and nerve supply, applied anatomy…10 marks Definition Scalp is the soft tissue cover of the calvaria (skull cap) Extent Antero-posterior extent- from the supra orbital margin to the superior nuchal line Transverse extent-from one zygomatic arch to the other Layers of the scalp Skin Connective tissue Aponeurosis Loose areolar tissue Pericranium Skin Thick Hairy Numerous sweat and sebaceous glands Connective tissue Dense subcutaneous tissue Close network of fibro fatty tissue Connects the skin (lying over it) to the aponeurosis (lying below it). Therefore, in case of trauma, it is generally these 3 layers which are avulsed Contains large number of blood vessels and nerves The walls of the blood vessels are adherent to the fibrous network Aponeurosis This is the epicranial aponeurosis or Galea aponeurotica It is the aponeurosis for the insertion of the occipital and frontal bellies of occipito-frontalis muscle The frontal bellies take origin from the skin of the eyebrow region The occipital bellies take a bony origin from the highest nuchal lines Occipitofrontalis muscle can produce antero-posterior movement of the scalp. Frontalis produces horizontal wrinkles and expresses horror Muscle is supplied by the facial nerve Galea is fibrous tissue with fibers extending antero-posteriorly It extends down to the zygomatic arches Loose areolar tissue This contains numerous valve-less emissary veins Emissary veins connect intra cranial venous sinuses to extra cranial veins Any collection of pus in this region can result in spread of infection through the veins into the intra cranial venous sinuses That is why this is the dangerous layer of the scalp Pericranium This is the outer peiosteum of the skull At the sutural lines , it is continuous with the endocranium Therefore, any collection of blood (generally traumatic) beneath the pericranium produces a localized swelling= cephalhaematoma which takes the shape of the related bone Nerve supply-scalp 5 nerves in front of auricle (4 sensory, 1 motor) 5 nerves behind the auricle (4 sensory, 1 motor) Nerve Supply Blood supply of scalp Total 5 arteries supply the scalp # in front of the auricle and 2 behind the auricle Supra orbital and supra trochlear are branches of internal carotid artery Remaining are branches of external carotid artery Therefore, on the scalp there is anastomoses between the ICA and the ECA Venous drainage Applied anatomy Skin is rich in sebaceous glands and therefore is a common site for sebaceous cysts In the connective tissue layer, since the walls of the blood vessels are adherent to the fibres of the tissue, in case of rupture of the vessels they are unable to retract leading to profuse bleeding. To stop such bleeding, manual pressure needs to be applied against the underlying bone Inflammation in the layer of connective tissue is painful as it is unyielding Scalp has a rich nerve supply and wounds may bleed profusely, but heal well Applied anatomy Injury in the scalp/temporal region might result in blood seeping beneath the frontalis muscle and collecting in the loose peri- orbital tissue (as frontalis has no bony attachment). This congeals over days and produces a black eye. Surgical incisions in the scalp should be in an antero-posterior direction (and not transverse as the pull of occipito frontalis muscle will cause the cut to gape) Skin connective tissue and aponeurosis are closely applied to each other and in avulsion of scalp these 3 layers are generally avulsed Loose areolar tissue is the dangerous layer of the scalp In case of fracture skull in which the dura is also torn, blood from an intra cranial haemorrhage leaks into the sub aponeurotic space and relieves raised intra cranial pressure and cerebral compression. This is a safety valve mechanism. Applied anatomy Cephalhaematoma Caput succedaneum- can occur in the newborn. It is a generalized edema over the scalp due to impeded venous return resulting from pressure over the region during passage through the birth canal