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The unique structure and innervation of facial skin contributes to it's specialised functions such as facial expressions and blushing, and offers some unique pathways for therapeutic interventions - which may explain the profound effects that we observe during MLD treatments for the neck and face.
Comparing innervation of facial skin and the skin of the rest of the body reveals the direct connection that facial skin has with autonomic centres of the brain. This may explain how the seemingly simple techniques of MLD, which are mainly gentle, repetitive, circular movements of the skin, can have such a calming effect on both vascular issues such as rosacea, and in emotional stress and anxiety.
Facial skin has a thinner, more delicate structure than skin on the rest of the body. This and the presence of autonomic fibres in more superficial layers of the dermis highlights the need for MLD Facialists to have very refined hand skills. Hear Koby talking about this on our YouTube Channel.
The Neural Landscape: Face vs. Body
Facial skin
Facial skin is innervated by the facial and trigeminal nerves (cranial nerves V & VII).
These nerve bundles which carry motor and sensory fibres of the somatic nervous system, and parasympathetic fibres of the autonomic system.
Autonomic functions are mediated in the thalamus and hypothalamus which sit atop the brain stem.
Sensory afferents from the skin of the upper face are carried by the cranial nerves, while the sensory afferents from the lower face and neck are carried by spinal nerves of the cervical plexus.
Sympathetic contributions are are also via the cervical ganglia of the sympathetic chains arising from thoracic spinal segments.
This distinct pattern of innervation is vital for co-ordination of blood flow to the facial skin, and to co-ordinate facial muscles during the expression of various emotional states.
Skin of the body
In contrast, the rest of the body relies on a complex network of spinal nerves that carry a broader range of sensory modalities, including proprioception, pain, and temperature.
This spinal system provides a more extensive and diverse sensory landscape, crucial for autonomic activities ranging from balance to protective reflexes.
This variation on origin between the face and body in both the somatic and autonomic nervous systems, creates a complex autonomic and sensory landscape, and one that can be utilised to maximum benefit by the skilled MLD Therapist.
A direct line to autonomic control centres
Autonomic control of the facial region is particularly unique due to the interaction of cranial parasympathetic fibres, superior cervical sympathetic fibres, and trigeminal sensory nerves.
This intricate network plays a crucial role in facial vasomotor control, influencing blood flow and skin colour during emotional responses such as blushing.
Research has identified parasympathetic involvement in blood flow in the upper dermis, whereas elsewhere in the body this is restricted to the sub-dermal regions of the skin.
Parasympathetic stimulation dilates small blood vessels, and their presence in the most superficial layers of the dermis may account for the unique responses of facial skin to emotional states such as embarrassment (1).
Sympathetic fibres originate from the superior cervical ganglion and travel along the external carotid artery and its branches to reach the face.
They contain more complex combinations of transmitters here than in other body regions, allowing them to control the skeletal muscles of facial expression (2).
MLD Therapists will be very familiar with the sympatholytic effects of MLD, especially during application of the basic face sequence.
The unique innervation of the skin of the face may explain why this has such a profoundly relaxing effect for most recipients.
The Role of Sensory Innervation
Facial skin is also richly supplied with sensory nerves that relay a variety of stimuli, including temperature changes and pain. For MLD Facial Therapists, an understanding of how facial skin communicates with the CNS is essential.
Sensory neurons in the skin of the face have a direct connection to the autonomic centres of the brain, and may provide an even more direct pathway for the effects of MLD to reach brain regions such as the thalamus and hypothalamus.
The rest of the body relies on a complex network of sensory inputs and recent research has illuminated the role of light touch mechanoreceptors in the skin, particularly in the context of immune function, lymph formation, wound healing, and connective tissue homeostasis.
These mechanoreceptors, including Merkel cells and Meissner's corpuscles, not only provide tactile information but also modulate various cellular and molecular activities. This interaction underscores the importance of tactile stimulation in managing skin health.
Read more in our post on MLD and the Mechanics of Skin Health.
Emotional and Psychological Connections
Coordinating facial expressions makes facial muscles amongst the most finely tuned effectors in the human motor system.
Neuromuscular control of our facial expressions is provided exclusively via the facial nerve and the interplay between facial skin innervation and emotional expression cannot be overstated.
The unique autonomic and sensory pathways governing the face allow for immediate physical manifestations of emotional states, eg stress or fear can trigger visible facial expressions and initiate physiological changes like sweating or flushing.
The gentle, reassuring touch of MLD may prove beneficial in addressing the psychosomatic components of facial conditions, and therapists should consider these emotional connections when designing treatment plans.
So much more to know!
We still have a lot more to find out about the intricate neural factors that control the human face. Research has been hampered by issues with using cadaver skin, and a lack of sensitivity in visualisation methods to discriminate between different nerve types at the smallest distributions.
Innervation of the facial skin is also one area in which we differ greatly from other mammals, so rodent and canine models cannot be used to simulate human neural responses. (3)
Conclusion
The distinct autonomic innervation of facial skin compared to the rest of the body highlights the importance of tactile stimulation in therapeutic practices.
For MLD Therapists, understanding the rich tapestry of facial innervation offers insights to finely tune their techniques to specific clinical goals, and enhance treatment efficacy. In an era where the mind-body connection is increasingly recognised, acknowledging the nuances of facial skin innervation is not just beneficial—it's essential.
References
Nolano, Maria, et al. "Cutaneous innervation of the human face as assessed by skin biopsy." Journal of anatomy 222.2 (2013): 161-169.
Matsubayashi, Tadatoshi, et al. "Significant differences in sympathetic nerve fiber density among the facial skin nerves: a histologic study using human cadaveric specimens." The Anatomical Record 299.8 (2016): 1054-1059.
Newly identified axon types of the facial nerve unveil supplemental neural pathways in the innervation of the face https://doi.org/10.1016/j.jare.2022.04.009
Neuronal Control of Skin Function: The Skin as a Neuroimmunoendocrine Organ. Roosterman et al. https://doi.org/10.1152/physrev.00026.2005
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