For the purposes of this video, we will define the perioral region as the area that lies beneath the columella, that is also bounded laterally by the nasolabial folds, and lies above the chin. We will now look at the key layers within the perioral region. Currently, we can see the skin and now the muscles in this area. The first muscle highlighted is the orbicularis oris, then the lip elevators, called the levator labii superioris alaeque nasi, the levator labii superioris, and the zygomaticus minor. Now, the lip depressors are indicated, which are called the depressor angularis oris, the depressor labii, and the platysma. We will discuss the platysma in more detail in another video. The buccinator and risorius muscles are also found in this area. We can see the modiolus, which is where some of these muscles come together. Within this region, the blood vessels are located relatively deep in comparison to the muscles.
There are some key features in this region that we should be aware of. Just below the nose we can see the philtral columns. The white roll is also highlighted. The vermillion border is the demarcation between the highly keratinised skin epidermis and the less keratinised red vermillion lip mucosa. The vermillion body, which is also called the red vermillion, contains mucosa that has both a dry and wet portion. Here, at the edge of the lips, you can find the oral commissures. Finally, in the centre of the upper lip is the cupid’s bow which provides a central projection of the lips with two peaks that give rise the the philtral columns. These then terminate in the columella.
The lip ratios differ between people of different ethnicities. For people of caucasian descent, the upper lip is often smaller than the lower lip and is usually between ⅓ to ⅔ the size of the lower lip. The golden proportion in this group is 1:1.618. In people of Afro-Caribbean, Chinese, and Japanese descent, the lip ratio is closer to 50/50. As we can see illustrated here, the upper lip is often ‘M’ shaped, while the lower lip is usually ‘W’ shaped. On the upper lip, we can see the Cupid’s bow and medial tubercle and on the lower lip we have the lateral tubercles. Both the upper and lower lip taper out from medial to lateral aspects. Within this region, the key muscles for us to identify are the orbicularis oris and the depressor angularis oris. The orbicularis oris muscle is a round, sphincteric muscle, and when it contracts it narrows the orifice of the mouth and purses the lips. The depressor angularis oris is a pyramidal shaped muscle that arises from the mandible posterior to the oblique line and inserts into the modiolus. Its action is to pull the mouth corners down, resulting in a mouth frown.
We are now going to look at a number of changes that occur to the perioral region during ageing. Here, we can see that perioral lines have developed, which are seen when pursing the lips or whistling. The white roll elongates and blunting can occur to the vermillion border. The Cupid’s bow and the philtral columns start to flatten. Inversion of the vermillion also occurs. The lip body inverts and thins, leading to a loss of volume in this area. Rhytids and wrinkles also appear in the lip mucosa. Finally, we can see the downturn of the corners of the mouth. As we assess this area for treatment, we need to bear in mind the importance of dental support for optimal effect of any aesthetic technique that we apply. Based on our anatomical landmarks, we can identify two points where we can inject botulinum toxin to address perioral lines. One is found close to the oral commissure and another is close to the philtrum. Both of these points are located approximately 3 mm above the vermillion border. Treating the depressor angularis oris with botulinum toxin can help maintain the continence of the oral commissure. We need to ensure that we treat lower in the muscle, where it is bulkier, and laterally. This is to avoid treating the depressor labii inferioris, which would lead to smile and speech asymmetry.
When we treat the lips with dermal filler, it is important to adjust volume to avoid over projecting the upper lip or excessively treating the lower lip in the lateral aspect. If we don’t do this, the patient will be left with a ‘sausage lip’ appearance. We also need to be mindful of a number of ‘at-risk’ areas within this region, which we need to avoid. Firstly, the facial artery gives off the inferior labial artery and superior labial artery as it passes the modiolus. These tend to run deep to the muscles in this area. As such, the safest zone for injecting is into the superficial, or submucosal layers. When a deeper injection is needed, a soft tissue cannula should be used to reduce the risk of vascular injury.