Cheeks

The cheeks (Latin: buccae) are described as the area between the eyes and jaws. They shape the human face and are considered a part of the digestive system as muscles within the cheeks participate in digestion, and the soft tissue of the cheeks forms the walls of the oral cavity. The cheeks are complex anatomical structures made of many muscle fibers, blood vessels, fat cells, minor glands and other tissue. As an anatomical structure, the cheeks have several functions. They take part in eating and chewing, talking and facial expression creation.

Cheek anatomy

The main mass or the base of the cheeks is mainly formed by the buccinator muscle fibers covered by the buccopharyngeal fascia. The eye defines the superior border of the cheeks, while the inferior border goes along the jawline. On the medial aspect is the nose, but on the lateral side is the ear.

The bony frame of the cheeks is formed by the bones of the skull. The upper bony part includes the maxilla and zygomatic bone, while the inferior portion - the mandible. The maxilla also forms the medial area of the cheeks. The term cheekbones is often used to describe the zygomatic arch composed of the temporal process of the zygomatic bone and the zygomatic process of the temporal bone. Therefore, the temporal bone also participates in creating the bony frame of the cheeks.

Within the cheeks are located the largest salivary glands - wedge-shaped parotid glands. Each parotid gland is situated anterior to the external ear, and they help form the cheeks and give them fullness. Through the cheeks goes the duct of the parotid gland (Stensen's duct). The mucosa of the cheeks in the oral cavity contains the papilla of the parotid duct through which the duct opens. The papilla is located opposite the second maxillary molar tooth.

Cheek fat pads

The cheeks contain several fat pads called buccal fat pads that lie close to the skin, mainly on the outer surface of the buccinator muscle. Newborn babies have very well-developed fat pads in their cheeks, but they decrease in size with age. The buccal fat pads give fullness to the cheeks and affect the shape of the face. The size and shape of fat pads vary among people and ethnic groups as these characteristics are associated with eating habits and genetics. The cheek fat pads can indicate nutrition level, and, for example, in malnutrition, they are not well developed and visible. In addition, loss of cheek fullness can also be an indicator of underlying disease.

The cheeks contain larger and smaller fat pads, and the smaller ones usually come together. Below the eyes are the infraorbital fat pads, and right under them are the medial cheek fat pads. The nasolabial fat pad goes from the lateral side of the nose or the ala of the nose to the corner of the mouth. The central aspects of the cheeks contain the middle cheek fat pads, but close to the ear is a large fat pad called the lateral temporal - cheek fat pad. It goes along the external ear from the jawline to the lateral aspect of the forehead. Along the jawline and close to the mouth are the superior and inferior jowl fat pads. Healthcare professionals can remove cheek fat pads during plastic surgeries, and they are also widely used in face reconstruction surgeries or congenital disability repairing surgeries.

Cheek muscles

The cheeks contain many muscle fibers that form them. The most prominent muscles found within the cheeks are the masseter and buccinator. The buccinator is the primary muscle involved in cheek compression, and it presses the cheeks to the teeth. It lies deep within the central aspect of each cheek and stretches from the alveolar arches of the mandible and maxilla to the corner of the mouth. The buccinator blends with the fibers of the orbicularis oris that form the medial aspects of the cheeks. The masseter is located anterior to the ear in the lateral aspect of each cheek. It extends from the zygomatic arch to the mandible, and, as a muscle of mastication, it helps in the chewing process.

Elevators (levators) of the lips and mouth and both zygomaticus muscles are also situated in the cheeks. The levator labii superioris aleaque nasi forms the medial aspect of the cheeks as it goes along the sides of the nose. Next to it lies the levator labii superioris, and it also forms the medial region of the cheeks. The zygomaticus major, zygomaticus minor and levator anguli oris muscle fibers are located more in the central aspect of the cheeks, mostly stretching from the zygomatic bone to the corner of the mouth. Inferior to previously mentioned muscles lies the risorius. Also, a small part of the lower aspect of the orbicularis oculi forms the superior border of the cheeks.

Cheek dimples

Some people show cheek dimples in both or only one cheek when smiling. Cheek dimples develop due to different variations of the zygomaticus major muscle. People, who have cheek dimples, usually have separated zygomaticus major. It is divided into two parts that appear as two separate bundles. The split is known as the duplication or bifurcation of the zygomaticus major, and skin movements over it result in cheek dimples. They are best visible when a person is smiling. The zygomaticus major stretches between the zygomatic bone and the corner of the mouth. If the zygomaticus major is separated, one bundle inserts at the corner of the mouth, but the other inserts slightly below it.

Cheek histology

The outer surface of the cheeks is covered by the skin, while the inner - by the mucosa. The histology of the cheeks is very similar to that of other parts of the oral cavity. But, unlike other anatomical structures, the cheeks contain a lot more muscle fibers and adipose (fat) tissue. Also, the skin of the cheeks has a massive amount of thick elastic fibers that create an elastic fiber network. The skin of the cheeks is lined with the stratified squamous keratinized epithelium, but the mucosa with the stratified squamous non-keratinized epithelium.

The mucosa contains minor buccal salivary glands, mainly in the areas that correspond to the maxilla and mandible. Around the parotid gland duct, the minor buccal glands are slightly larger than those in other cheek areas. These larger glands are called the molar glands because their ducts open next to the last maxillary molar teeth. The cheeks also contain sebaceous glands, and they are located in the midline of the mucosa, where the maxillary and mandibular teeth connect. They are similar to sebaceous glands found in the skin and appear as yellow, or yellowish-grey spots called the Fordyce spots. Epithelium of this area has slight signs of keratinization.

And finally, the cheeks contain high amounts of blood vessels and capillaries. The presence of capillaries can be easily observed when a person blushes and cheeks become red-colored. It happens because the blood vessels of the cheeks widen. This process is called vasodilation. It leads to increased perfusion, and there is a higher amount of blood in capillaries.

Neurovascular supply of cheeks

Arterial supply

The main arteries that provide arterial supply for structures found within the cheeks are the transverse facial and facial arteries. The transverse facial artery is a terminal branch of the superficial temporal artery, while the facial artery arises from the external carotid artery.

The medial aspect of the cheeks receives arterial blood supply from the angular artery - a terminal branch of the facial artery. The infraorbital and buccal arteries from the maxillary artery provide the superior and central parts of the cheeks with arterial blood. And the zygomatico-orbital artery may also supply the superior aspect of the cheeks.

Venous drainage

Venous drainage of the cheeks is provided by the facial vein that further drains into the internal jugular vein.

Lymphatic drainage

Lymph from the lateral and superior areas of the cheeks is drained to the preauricular lymph nodes, while from the inferior and medial regions to the submandibular lymph nodes. Eventually, lymph from the left cheek is drained into the thoracic duct, while from the right cheek into the right lymphatic duct.

Innervation

Innervation of the muscles found within the cheeks is mainly provided by the branches arising from the facial nerve (CN VII). The buccal branch of the facial nerve provides nerve supply to both zygomaticus muscles, levator labii superioris, risorius, buccinator and orbicularis oris muscles. The zygomatic branch also innervates the zygomaticus muscles. And finally, the masseteric nerve is a motor nerve that arises from the mandibular nerve (CN V3), and it supplies the masseter muscle.

The skin and mucosa of the cheeks receive sensory nerve supply from two divisions of the trigeminal nerve (CN V) - mandibular (CN V3) and maxillary (CN V2) nerves. The buccal nerve of the mandibular nerve provides sensory innervation to the cheeks. Also, the infraorbital nerve and zygomaticofacial branch of the zygomatic nerve (branch of the maxillary nerve) supply the cheeks.

Cheek functions

The cheeks have several functions that provide normal physiological processes of the human body. All anatomical structures within the cheeks participate in digestion, talking and different facial expression creation.

The cheeks help in both digestion processes - the mechanical and chemical food processions. The mechanical food procession is provided by the muscles. The masseter is classified as the mastication muscle, and it contracts during chewing. Muscles within the cheeks regulate the size and shape of the oral fissure and, therefore, also help to get the food into the oral cavity. In contrast, the chemical food procession is provided by saliva secreted by the parotid gland and minor buccal salivary glands.

Most of the muscles within the cheeks are classified as facial muscles or muscles of facial expression. And their contractions are responsible for various facial expressions, except the buccinator, as it helps to hold the food in the oral cavity while it is being chewed. Most of the muscles also contract during talking.

Disorders of cheeks

Multiple disorders can affect the appearance of the cheeks. Usually, changes in the visual appearance of the cheeks are related to systemic conditions or various skin diseases. Some systemic disorders present with their pathognomonic or typical symptoms on the cheeks. However, the most common disorders include various skin diseases such as acne. The outer surface of the cheeks is visible to everyone, and changes in visual appearance can impact the social life and mental health of a person. Disorders affecting cheeks can be caused by many factors, such as:

• Unhealthy diet
• Various antigens
• Genetic predisposition
• Stress
• Lack of sleep
• Cosmetic products
• Hormonal changes
• Sun exposure
• Excessive tobacco and alcohol consumption
• Weather and temperature changes

The skin of the cheeks also changes with aging. Lack of elastic fibers and collagen, inadequate hydration and negative facial expressions can cause the formation of wrinkles.

Pathognomonic symptoms

Some of the pathognomonic or typical symptoms of various diseases can manifest on the cheeks. For example, butterfly or malar rash is a specific symptom of systemic lupus erythematosus. When the malar rash appears, lupus is present beyond any doubt, and it is visible across the cheeks and the bridge of the nose. The malar rash is a red or purple facial rash that resembles the form of a butterfly, and it is similar to the rash that develops after a sunburn.

Acne

As mentioned previously, the most common disorders affecting the cheeks are various skin diseases such as acne. Acne is a skin disease that occurs when hair follicles become plugged with dead skin cells and oils, resulting in inflammation and bacterial infection. Usually, acne is seen in teenagers, and although it can also affect adults, teenagers show more severe manifestations than adults. Acne affects skin areas that contain sebaceous glands, including cheeks.

Genetic predisposition and sebaceous gland overactive secretion can lead to acne. Hormonal changes, poor diet, stress, medications, other underlying diseases such as digestive tract disorders and usage of bad quality cosmetics can affect acne and make it worse.

Acne appears as various types of comedones such as whiteheads, blackheads and blisters or pimples. Whiteheads are plugged pores that are closed, while blackheads are plugged pores that are open. Acne can present with only a few small raised skin lesions, or more severe forms can manifest with painful nodules or even cystic lesions.