Scalp- Layers, Nerve and Blood Supply
After reading this post you will know:
- Layers of scalp.
- Anatomical basis for dangerous layer of scalp.
- Arteries supplying scalp.
- Sensory and motor nerve supply of scalp.
- Origin , insertion action and nerve supply of occipito-frontalis muscle.
- Applied anatomy of scalp.
Q. Define scalp and write its extent.
Ans. a.Definition: Scalp is the soft tissue that covers the vault of the skull.
Anteriorly: Supraorbital margin
Laterally : Superior temporal lines
Posteriorly: External occipital protuberance and superior nuchal lines.
- Layers of scalp
- Arteries supplying scalp
- Sensory nerves of scalp
LAYERS OF SCALP
Ans. a. Layers of scalp: The scalp consists of five layers. Superficial three are intimately bound together and move as one unit. The five layers from superficial to deep are:
C – Connective tissue ( superficial fascia)
A- Aponeurosis ( epicranial aponeurosis)
L- Loose areolar tissue
P – pericranium
|Dangerous layer of scalp: Subaponeurotic loose areolar connective tissue layer is known as dangerous layer of scalp because the blood and pus tend to collect in this layer and the infection from this layer may travel readily along the emissary veins into the intracranial venous sinuses.|
ARTERIAL SUPPLY OF SCALP
Q. Describe arterial supply of scalp.
A. Arteries suppyling scalp: Scalp has a rich blood supply from branches of internal and external carotid arteries. There is a rich anastomosis between the branches of internal and external carotid arteries. There are five arteries on each side , three in front of the auricle and two behind the auricle. The arteries are:
- In front of the auricle:
- Supratrochlear and Supraorbital (Branches of internal carotid artery)
- Superficial temporal (Branch of external carotid artery)
Behind the auricle:
- Posterior auricular and Occipital (Branches of external carotid artery)
Q. Why scalp wounds bleed profusely but heal quickly.
A. Scalp wounds bleed profusely also due to the following reason:
Scalp has a rich blood supply. The main arteries and veins supplying scalp lie in the dense connective tissue layer (CTL) deep to the skin. The walls of the blood vessels are adherent to the fibrous network in the CTL, therefore when the blood vessels are torn they are unable to retract, resulting in profuse bleeding.
NERVE SUPPLY OF SCALP
Q. Describe the sensory nerve supply of scalp.
- A. Sensory nerves supplying scalp
|In front of the auricle||Behind the auricle|
|Supratrochlear ( from ophthalmic division of trigeminal nerve (CN V1))||Great auricular ( from ventral rami of C2, C3 spinal nerves)|
|Supraorbital ( from ophthalmic division of trigeminal nerve (CN V1)||Lesser occipital ( from ventral ramus of C2 spinal nerve)|
|Zygomaticotemporal ( from maxillary division of trigeminal nerve (CN V2)||Greater occipital ( from dorsal ramus of C2 spinal nerve)|
|Auriculotemporal ( from mandibular division of trigeminal nerve (CN V3)||Third occipital ( from dorsal ramus of C3 spinal nerve)|
Q4. Describe occipitofrontalis muscle under the following headings.
- Origin and insertion
- Nerve supply
Ans. Occiitofrontalis muscle: It consists of a pair of occipital bellies (posteriorly) and a pair of fronatal bellies (anteriorly). Both the parts are inserted into the intervening galea aponeurotica or epicranial aponeurosis.
|Occipital bellies||Lateral 2/3rd of superior nuchal lines of occipital bone||Into epicranial aponeurosis||Posterior auricular branch of facial nerve||Alternate contraction of occipitalis and frontalis move the scalp backward and forward.
Frontal bellies raise the eyebrows as in surprise.
|Frontal bellies||Skin and subcutaneous tissue over the eyebrows and root of nose.||Into epicranial aponeurosis||Temporal branch of facial nerve|
APPLIED ANATOMY OF SCALP
Q5. Give anatomical basis of :
- Deep wounds of scalp tend to gape
- A blow on head may lead to ‘Black eye’.
Ans. a. Deep wounds of scalp tend to gape: epicranial aponeurosis is under tension from the tone of occipitalis and frontalis muscles and therefore if aponeurosis is cut , the wound tend to gape.
b. A blow on head may lead to collection of blood in the 4th layer ( loose areolar tissue) of scalp . The blood from this layer may gravitate into the eyelids resulting in ‘black eye’ because the frontalis muscle has no bony attachment. The blood cannot pass laterally or posteriorly due to the attachment of epicranial aponeurosis and occipitalis muscle to the superficial temporal lines and superior nuchal lines respectively.