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Scalp
Gray's	subject #105 378
Artery	supratrochlear, supraorbital, superficial temporal, occipital
Vein	superficial temporal, posterior auricular, occipital
Nerve	supratrochlear, supraorbital, greater occipital, lesser occipital
Lymph	occipital, mastoid
MeSH	Scalp

The scalp is the anatomical area bordered by the face anteriorly and the neck to the sides and posteriorly.

Layers

It is usually described as having five layers, which can be remembered with the mnemonic "SCALP":^[1].

• S: The skin on the head from which head hair grows. It is richly supplied with blood vessels.
• C: Connective tissue. A thin layer of fat and fibrous tissue lies beneath the skin.
• A: The aponeurosis called epicranial aponeurosis (or galea aponeurotica) is the next layer. It is a tough layer of dense fibrous tissue which runs from the frontalis muscle anteriorly to the occipitalis posteriorly.
• L: The loose areolar connective tissue layer provides an easy plane of separation between the upper three layers and the pericranium. In scalping the scalp is torn off through this layer. It also provides a plane of access in craniofacial surgery and neurosurgery. This layer is sometimes referred to as the "Danger Zone" because of the ease by which infectious agents can spread through it to emissary veins which then drain into the cranium. The loose areolar tissue in this layer is made up of random collagen I bundles, collagen III. It contains the majors blood vessels of the scalp, which bleed profusely upon injury, partly due to the absence of venous valves found in the circulation below the neck. It will also be rich in glycosaminoglycans (GAGs) and will be constituted of more matrix than fibers.
• P: The pericranium is the periosteum of the skull bones and provides nutrition to the bone and the capacity for repair. It may be lifted from the bone to allow removal of bone windows (craniotomy).

The clinically important layer is the aponeurosis. Scalp lacerations through this layer mean that the "anchoring" of the superficial layers is lost and gaping of the wound occurs; this requires suturing. This can be achieved with simple or vertical matress sutures using a non-absorbable material, which are subsequently removed at around days 7-10.

Blood supply

The blood supply of the scalp is via five pairs of arteries, three from the external carotid and two from the internal carotid:

• internal carotid
  • the supratrochlear artery to the midline forehead. The supratrochlear artery is a branch of ophthalmic branch of the internal carotid artery.
  • the supraorbital artery to the lateral forehead and scalp as far up as the vertex. The supraorbital artery is a branch of ophthalmic branch of the internal carotid artery.
• external carotid
  • the superficial temporal artery which gives frontal and parietal branches to supply much of the scalp
  • the occipital artery which runs from posteriorly to supply much of the back of the scalp
  • the posterior auricular artery, a branch of the external carotid artery, ascends behind the auricle to supply the scalp above and behind the auricle.

Innervation

Innervation is the connection of nerves to the scalp: the sensory and motor nerves innervating the scalp. The scalp is innervated by the following:^[2]

• Supratrochlear nerve and the supraorbital nerve from the ophthalmic division of the trigeminal nerve
• Greater occipital nerve (C2) posteriorly up to the vertex
• Lesser occipital nerve (C2) behind the ear
• Zygomaticotemporal nerve from the maxillary division of the trigeminal nerve supplying the hairless temple
• Auriculotemporal nerve from the mandibular division of the trigeminal nerve

The innervation of scalp can be remembered using the mnemonic, "Z-GLASS" for, Zygomaticotemporal nerve, Greater occipital nerve, Lesser occipital nerve, Auriculotemporal nerve, Supratrochlear nerve and Supraorbital nerve.^[2]

Lymphatic drainage

There are no lymph nodes in the scalp; lymphatic drainage is to the pre- and post-auricular nodes.

Role in aesthetics

The scalp plays an important role in the aesthetics of the face. Androgenic alopecia, or male pattern hair loss, is a common cause of concern to men. It may be treated by medication (eg finasteride, minoxidil) or hair transplantation with variable success. If the scalp is heavy and loose, a common change with aging, the forehead may be low, heavy and deeply lined. The brow lift procedure aims to address these concerns.

Hair transplantation

All the current hair transplantation techniques utilize the patient's existent hair. The aim of the surgical procedure is to use such hair as efficiently as possible. The right candidates for this type of surgery are individuals who still have hair growing in a healthy way on the sides and the back of the head, in order to acquire hair from those areas. Different techniques are utilized in order to obtain the desired cosmetic results based on factors such as the color of the hair, the type of texture and others such as curliness or waviness.

The most utilized technique is the one known as micro grafting, as it is the one that produces natural-like results. It is akin to Follicular Unit Extraction, but it is not so advanced. A knife with multiple blades is used to remove tissue from donor areas, then such tissue is fragmented into smaller chunks using direct vision instead of using a microscope. ^[3]

Redness in scalp after surgery

After the surgery is complete, and during the process of healing, redness in the scalp is a possibility. The main reason is because during this period, the areas of the head where the transplant has taken place are softer than normal, but this is a regular consequence of the medical procedure therefore, the plastic surgeon will point it out the patient, and will provide him with a series of indications to be followed in order to contribute to a desired recovery. Such recommendations might include the application of ice and abstaining from any physical activities in the short term. ^[4]

Pathology

The scalp is a common site for the development of tumours including:

• epidermoid cyst
• pilar cyst
• actinic keratosis and squamous cell carcinoma
• basal cell carcinoma
• merkel cell tumours

Scalp conditions

• Dandruff -- A common problem due to the excessive shedding of dead skin cells from the scalp
• Seborrhoeic dermatitis -- a skin disorder causing scaly, flaky, itchy, red skin
• Cutis verticis gyrata -- A descriptive term for a rare deformity of the scalp.
• Head lice
• Tycoon's cap, also known as acne necrotica miliaris, characterized by pustules and itching.

See also

• Trichology -- the scientific study of hair and scalp
• Trichodynia -- burning scalp syndrome
• Scalping -- the act of removing the scalp, usually with the hair, as a portable proof or trophy of prowess in war.
• Dermatillomania - obsessive skin picking

Additional images

Diagrammatic section of scalp.

References

1. ^ Mnemonic at medicalmnemonics.com 258
2. ^ ^{a b} "Scalp: Nerve supply, Medical mnemonic". LifeHugger. http://mc.lifehugger.com/moc/925/Scalp_nerve_supply. Retrieved 2009-12-15. 
3. ^ An overview on head transplantation Retrieved on 2010-03-09
4. ^ Pistone, Gregory MD. "Scalp Redness Following a Hair Transplant" 2010-03-09.

Human anatomy (TA A01.1) Head Forehead · Ear · Jaw · Face (Cheek, Eye, Nose, Mouth, Chin) · Occiput · Scalp · Temple Neck Throat · Adam's apple Torso Breast · Thorax · Abdomen · Navel · Back · Pelvis Sex organs Limbs Upper limb Shoulder · Axilla · Arm Elbow · Forearm Wrist · Hand · Finger (Thumb · Index · Middle · Ring · Little) Lower limb/ (see also leg) Hip · Buttocks · Thigh Knee · Calf · Crus Ankle · Heel · Foot · Toe (Hallux · Fifth) · Sole Skin Hair

External links

• Histology at BU 08601ooa - "Integument: scalp, transverse"
• Histology at BU 08801ooa - "Integument: scalp"
• lesson1 at The Anatomy Lesson by Wesley Norman (Georgetown University)
• http://www.dartmouth.edu/~humananatomy/figures/chapter_47/47-1.HTM

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