Scalp page 1
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I. DEFINITION: It is the soft tissue that covers the vault of the skull
II. EXTENT:
ANTERIORLY: Supra- orbital margin. s
POSTERIORLY: External occipital protuberance and highest nuchal line.
LATERALY: Superior temporal line.
III. LAYERS: The scalp is formed of 5 layers, The letters of the word "scalp" indicate each of these layers:
S=Skin
C=Connective tissue
A=Aponeurosis
L=Loose areolar tissue
P=Pericranium.
SKIN: Thick, hairy, highly vascular, rich in sweat and sebaceous glands (common site for seborrhea & sebaceous cyst due to blockage of the duct draining the sebaceous gland).
CONNECTIVE TISSUE: it is a dense connective tissue, containing arteries, veins, nerves & lymphatics. It contains also septa that connect this layer with the layer above &the layer below; thus the first 3 layers are adherent. The septa divide the layer into partitions that are filled with fat, Since the connective tissue is dense:
a- Infection tends to remain localized, however it causes pain.
b- Wounds do not gap.
c- A small wound causes profuse bleeding because the walls of arteries adhere to the connective tissue septa, which prevent them from contraction or retraction.
APONEUROSIS "EPICRANIAL APONEUROSIS"s A strong fibrous sheet adherent to the first 2 layers. . Anteriorly: it receives the insertion of frontal bellies of occipito-frontalis.
Laterally: it is attached to the superior temporal line Posteriorly: it receives the insertion of occipital bellies of occipito-frontalis (A wound reaching this layer Gaps because of contraction of the muscle).
page 2
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OCCIPITO-FRONTALIS MUSCLE
it has 2 frontal and 2 occipital bellies
ORIGIN:
Frontal bellies: are wider, partly united in midline, each arises from the skin of eyebrows.
Occipital bellies: are narrower separated from each other by an extension of epicranial aponeurosis, each arises from lateral 2/3 of the highest nuchal line.
INSERTION: Epicranial aponeurosis.
NERVE SUPPLY:
a- Frontal bellies: Temporal branch of facial nerve
b- Occipital bellies: Posterior auricular branch of facial nerve.
ACTION:
a- Frontal bellies: pull the scalp and eyebrows forward producing transverse wrinkles of the forehead.
b- Occipital bellies: pull the scalp backwards.
IV. BLOOD SUPPLY: The scalp has rich blood supply.
*The arteries anastomose freely with each other.
*They are branches of either the external carotid artery (ECA) or internal carotid artery (ICA).
Scalp layers fig (2)
Extent of the scalp fig (1)
Occipito-frontalis muscle
page 3
ARTERIES OF THE SCALP :
Arteries of the scalp
VEINS OF THE SCALP:
*Veins of the scalp accompany the arteries and have similar names.
*Veins of the scalp anastomose freely with one another and are connected to diploic veins of the skull bones and intracranial venous sinuses by "emissary veins ".
.Supratrochlear & supraorbital veins unite at the medial angle of eye to form the facial vein.
.Superficial temporal vein unites with maxillary vein inside parotid gland to form retromandibular vein. The latter divides into anterior and posterior divisions at the lower end of parotid gland.
Veins of the scalp
Emissary veins
*They are valveless veins that pass through skull foramina to connect veins inside the cranial cavity (venous sinuses) with veins outside the cranial cavity: Some are constant, while others may be absent.
*they help reduce venous pressure inside the cranial cavity, but they may be the routes of spread infection from outside to the cranial cavity Example: Parietal emissary vein pass through parietal emissary foramen to connect veins of the scalp with superior sagittal sinus inside the skull.
Emissary veins
page 4
V. Nerve supply:
By 10 nerves 5 in front of the auricle & 5 behind the auricular
*In Front of the auricle.
4 Sensory nerves: (branches of trigeminal nerve)
Supratrochlear n. supplies skin of forehead.
Supraorbital n. (from ophthalmic skin of forehead up to the vertex.
Zygomaticotemporal n. (from maxillary n.) supplies non-hairy part of temporal region.
Auriculotemmporal n. (from mandibular n.) supplies the hairy part of temporal region.
1 Motor nerve: temporal branch of facial nerve supplies frontal belly of occipito-frontalis.
*Behind the auricle.
4 Sensory nerves: (branches of cervical spinal nerves)
Great auricular n. (C 2,3) supplies skin over the mastoid process.
Lesser occipital n. (C 2) supplies skin of scalp behind auricle.
Great occipital n. (C2) supplies skin of scalp up to vertex.
Third occipital n. (C 3) supplies skin of lower part of occipital
1 Motor nerve: Posterior auricular branch of facial nerve supplies occipital belly of occipito-frontalis.
Nerve supply of the scalp
VI. LYMPH DRAINAGE:
Pre-auricular region: drained by parotid L.Ns.
Post-auricular region: drained by mastoid & occipital LNs.
REFRENCES
Head and Neck regional anatomy for dental students Part 1;Ain Shams Uni. 2015-26085
Disclaimer: all images were brought from google search and no copyright was claimed on them.
