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The scalp is composed of five layers of soft tissue that cover the cranium. These layers are the skin, subcutaneous tissue, Occipitofrontalia and its aponeurosis, subaponeurotic areolar tissue, and pericranium. The scalp is important aesthetically as hair grows on the skin of the scalp, aiding in heat conservation and playing a role in an individual's appearance. The Occipitofrontalis (Epicranius) is a broad, musculofibrous layer that covers the top of the skull, from the nuchal lines to the eyebrows. It consists of four bellies—two occipital and two frontal—that work together to move the entire scalp backward and forward.
| Characteristics | Values |
|---|---|
| Number of layers | 5 |
| First layer | Skin |
| Second layer | Connective tissue |
| Third layer | Aponeurosis or epicranial aponeurosis |
| Fourth layer | Loose connective tissue |
| Fifth layer | Pericranium |
| Nerve branches | Posterior auricular, temporal, zygomatic, buccal, marginal mandibular, and cervical nerves |
| Nerve mnemonic | To Zanzibar By Motor Car! |
| Muscles | Occipitofrontalis, orbicularis oculi |
| Veins | Supraorbital, supratrochlear, superficial temporal, occipital, posterior auricular, parietal emissary, frontal, pterygoid venous plexus |
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What You'll Learn
- The scalp is made of five layers: skin, connective tissue, aponeurosis, loose connective tissue, and pericranium
- The occipital belly contracts to draw the scalp back, and the frontal belly contracts to protract the scalp
- The scalp is innervated by the greater and lesser occipital nerves
- The supraorbital and supratrochlear veins drain the superficial scalp anteriorly
- The scalp is covered by the temporal fascia and extends to the zygomatic arches on each side
The scalp is made of five layers: skin, connective tissue, aponeurosis, loose connective tissue, and pericranium
The scalp is made up of five layers, each with its own unique structure and function. These layers, from the outermost to the innermost, are the skin, dense connective tissue, epicranial aponeurosis, loose areolar connective tissue, and pericranium or periosteum.
The first and outermost layer of the scalp is the skin, which is thick and contains numerous hair follicles and sebaceous glands. These glands secrete sebum, a natural oil that lubricates the scalp and promotes hair health. The skin layer is prone to sun damage and can be susceptible to sebaceous cysts.
The second layer, known as the dense connective tissue or superficial fascia, is a subcutaneous layer of fat, blood vessels, nerves, and lymphatics. This layer is richly vascularised and innervated, with blood vessels that are highly adherent to the connective tissue. This prevents full vasoconstriction in response to damage, which can lead to profuse bleeding if the scalp is lacerated.
The third layer is the epicranial aponeurosis or galea aponeurotica, a thin, tendon-like structure that provides a strong and immobile connection between the frontalis and occipitalis muscles. This layer is crucial for stabilising the scalp and facilitating muscle movement.
The fourth layer is the loose areolar connective tissue, a thin and flexible layer that separates the upper layers from the pericranium. This layer allows for smooth mobility and flexibility of the scalp. Due to its ability to be easily dissected, it serves as an important plane of entry in craniofacial surgery. However, this layer is also considered a "danger zone" as it can be a harbour for potential infections that can spread to the meninges.
The fifth and innermost layer of the scalp is the pericranium or periosteum, which covers the bones of the cranial vault. This layer provides protection to the underlying structures and helps shield them from physical trauma and potential pathogens.
Together, these five layers of the scalp serve essential functions, including protection, stabilisation, and facilitating muscle movement, while also playing a role in aesthetics and heat conservation.
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The occipital belly contracts to draw the scalp back, and the frontal belly contracts to protract the scalp
The scalp is a complex anatomical structure, and among the muscles present in this region, we find the occipitofrontalis muscle, which plays a crucial role in scalp movement and facial expressions. This muscle is comprised of three sections: the frontalis, the occipitalis, and the galea aponeurotica, each with distinct functions.
The occipital belly, or occipitalis, is responsible for retracting the scalp when its nuchal part is fixed. It originates from the lateral two-thirds of the superior nuchal lines of the occipital bone and moves the scalp backwards when contracted. This movement, although typically considered insignificant in isolation, becomes highly relevant when combined with the contraction of the frontal belly.
The frontal belly, or frontalis, is the section of the occipitofrontalis muscle that overlies the forehead. It is a thin, flat band in the anterior scalp with no bony attachments. When the forehead attachment is fixed, the frontal belly aids in pulling the scalp forward, contributing to the wrinkling of the forehead and the movement of the eyebrows.
Together, the contraction of the occipital belly to draw the scalp back and the contraction of the frontal belly to protract the scalp enable the entire scalp to move backward and forward. This coordinated action of the occipitofrontalis muscle is essential for various facial expressions and non-verbal communication.
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The scalp is innervated by the greater and lesser occipital nerves
The human scalp is innervated by a complex network of nerves, including the greater occipital nerve (GON) and the lesser occipital nerve (LON). These nerves are part of the occipital nerves, a group of nerves that originate from the cervical spinal nerves C2 and C3. The occipital nerves consist of three primary nerves: the GON, the LON, and the third occipital nerve (TON).
The GON is the largest purely afferent nerve among the occipital nerves. It arises from the medial division of the dorsal ramus of the C2 spinal nerve. The GON travels up to the vertex of the skull, providing sensory innervation to the skin of the posterior scalp. It also pierces the semispinalis capitis muscle and, in some cases, the trapezius and obliquus capitis inferior muscles.
The LON, on the other hand, arises from the anterior rami of C2 and C3. It runs superiorly towards the skull along the posterior aspect of the sternocleidomastoid muscle. The LON innervates the skin behind the ear and gives off two types of branches: communicating and cutaneous. The communicating branches interconnect with the GON, ensuring a complex network of nerve signals.
The TON is the third major occipital nerve and may provide additional innervation to the scalp. It originates from the dorsal ramus of C3 and innervates the C3 dermatome. While the TON is primarily associated with sensory fibres, it also carries some motor fibres, providing motor innervation for the semispinalis capitis muscle.
The intricate network of these nerves ensures the proper functioning of the scalp and surrounding areas. Any disruption or compression of these nerves can lead to conditions such as occipital neuralgia, characterised by intense pain in the occipital region, or migraines.
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The supraorbital and supratrochlear veins drain the superficial scalp anteriorly
The scalp is the anatomical term for the subcutaneous tissue that covers the cranium. It has five layers: skin, connective tissue, galea aponeurotica, loose areolar connective tissue, and the pericranium. The scalp is important aesthetically as hair grows on it, aiding in heat conservation and playing a role in an individual's appearance.
The scalp has a network of veins, arteries, and nerves. The supraorbital and supratrochlear veins drain the superficial scalp anteriorly. The supraorbital vein originates on the forehead and drains the forehead, eyebrow, and upper eyelid. It communicates with the frontal branch of the superficial temporal vein and passes inferiorly, superior to the frontalis muscle. It then joins the supratrochlear vein inferiorly and the superior ophthalmic vein medially. The supratrochlear vein, also known as the frontal vein, originates on the forehead and drains the superficial muscles and skin of the forehead and the front of the scalp.
The supraorbital and supratrochlear veins are branches of the ophthalmic artery, which is a terminal branch of the internal carotid artery. The ophthalmic artery supplies the anterior portion of the scalp. The supratrochlear vein is also associated with the supratrochlear nerve, which is located medially in the supratrochlear vein. The supraorbital nerve, on the other hand, has two branches: the medial branch, which is deep in the supratrochlear vein, and the lateral branch, which is medial and deep to the supraorbital vein.
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The scalp is covered by the temporal fascia and extends to the zygomatic arches on each side
The scalp is covered by the temporal fascia, a dense fibrous layer that covers the temporalis muscle. The temporal fascia attaches superiorly along the superior temporal line and covers the temporalis muscle. The superior temporal line is a bony ridge on the side of the skull, just above the ear. The temporal fascia is divided into two layers: the superficial layer and the deep layer. These two layers surround the temporal fat pad and attach to the zygomatic arch.
The zygomatic arch, or cheekbone, is a bony structure formed by the fusion of the temporal bone and the zygomatic bone. It is located on the side of the skull, just below the eye. The temporal fascia attaches to the medial and lateral surfaces of the zygomatic arch. The medial surface of the zygomatic arch is the side closest to the midline of the body, while the lateral surface is the side farthest from the midline.
The temporal fascia extends to the zygomatic arches on each side of the scalp. The zygomatic arches are important structures that provide attachment points for muscles and ligaments. They also play a role in the formation of the orbit, or eye socket. The zygomatic arches are also significant in evolutionary biology as they are derived from the ancestral temporal fenestra of the synapsid ancestor of mammals.
The temporal fascia and the zygomatic arches are important anatomical structures that contribute to the stability and function of the scalp and surrounding areas. The temporal fascia provides a strong fibrous covering for the temporalis muscle, while the zygomatic arches provide attachment points for muscles and ligaments, and contribute to the structure of the orbit. Together, they play a crucial role in maintaining the integrity of the scalp and allowing for a range of facial expressions and movements.
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Frequently asked questions
The scalp is composed of soft tissue layers that cover the cranium. It is an anatomical region bordered anteriorly by the human face and laterally and posteriorly by the neck. It extends from the superior nuchal lines and occipital turbulences to the supraorbital foramen.
There are five layers to the scalp: the skin, connective tissue layer, galea aponeurotica, loose areolar connective tissue, and the pericranium.
The scalp serves as a physical barrier to protect the cranial vault from physical trauma and potential pathogens that can cause infection. Aesthetically, it serves as an area where hair can grow.
