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Dermis

Dermis, also known as 'true skin' is considered the core of the integumentary system. It contains blood and lymph vessels, nerves, hair follicles, sebaceous glands, sweat glands and other structures such as deep touch receptors called Pacinian corpuscles. The dermis is made of two layers of connective tissue that compose an interconnected mesh of elastin and collagen fibers produced by fibroblasts (Tortora, 2018). 

Dermis provides a flexible but tough support structure, between 1 - 4  mm thick (depending on age and body location) making it much thicker than the epidermis. The thickness of dermis doubles between the age of 3 and 7 years and again at puberty. With ageing, the thickness and moisture in the dermis decreases and causes loss of volume and sagging skin (Shin et al., 2019). 

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Structural components in the dermis are:

  • Collagen fibers (strength)

  • Elastic fibers (elasticity)

  • Extrafibrillar matrix (gelatinous glycosaminoglycans that binds water and gel-like substances fill-up the space within the cells)

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Papillary Layer

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The papillary layer is made of loose, areolar connective tissue, which means the collagen and elastin fibers of this layer form a loose mesh (Bernstein. et al., 2021). This superficial layer of the dermis projects into the stratum basale of the epidermis to form finger-like dermal papillae (Chamber & Vukmanovic-Stejic, 2020). Within the papillary layer are fibroblasts, a small number of fat cells (adipocytes), and an abundance of small blood vessels. In addition, the papillary layer contains phagocytes, defensive cells that help fight bacteria or other infections that have breached the skin (Papaccio et al., 2022). This layer also contains lymphatic capillaries, nerve fibers, and touch receptors called the Meissner corpuscles.

 

Reticular Layer

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Underlying the papillary layer is the much thicker reticular layer, composed of dense, irregular connective tissue. This layer is well vascularized and has a rich sensory and sympathetic nerve supply. The reticular layer appears reticulated (net-like) due to a tight meshwork of fibers (Roger et al., 2019). Elastin fibers provide some elasticity to the skin, enabling movement. Collagen fibers provide structure and tensile strength, with strands of collagen extending into both the papillary layer and the hypodermis. In addition, collagen binds water to keep the skin hydrated (Shin et al., 2019).

 

Collagen injections contain hyaluronic acid and Retin-A creams (Khalil et al., 2017) help restore skin turgor by either introducing collagen externally or stimulating blood flow and repair of the dermis (Mathew-Steiner et al., 2021), respectively. From cosmeceutical perspective, topical vitamin C has excellent efficacy for the fibroblasts activity (Pandey et al., 2023).

Treatments such as microneedling and higher concentration of chemical peels also can stimulates the fibroblasts production (Lee et al., 2021).

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However, none of these will work without daily application of sunscreen (Guan et al., 2021).

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REFERENCES

 

Bernstein, E. F., Weiss, A. S., Bates, D., Humphrey, S., Silberberg, M., & Daniels, R. (2021). Clinical Relevance of Elastin in the Structure and Function of Skin. Aesthetic surgery journal. Open forum, 3(3), ojab019. doi:https://doi.org/10.1093/asjof/ojab019

 

Chambers, E., & Vukmanovic-Stejic, M. (2020). Skin barrier immunity and ageing. Immunology, 160(2), 116-125. doi:https://doi.org/10.1111/imm.13152

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Cherney, K. (2018, May 30). Microneedling: Collagen Induction Therapy. Retrieved from Healthline: https://www.healthline.com/health/microneedling

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Guan, L. L., Lim, H. W., & Mohammad, T. F. (2021). Sunscreens and Photoaging: A Review of Current Literature. American journal of clinical dermatology, 22(6), 819-828. doi:https://doi.org/10.1007/s40257-021-00632-5

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Khalil, S., Bardawil, T., Stephan, C., Darwiche, N., Abbas, O., Kibbi, A. G., . . . Kurban, M. (2017). Retinoids: a journey from the molecular structures and mechanisms of action to clinical uses in dermatology and adverse effects. Journal of Dermatological Treatment, 28(8), 684-696. doi:https://doi.org/10.1080/09546634.2017.1309349

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Lee, H., Hong, Y., & Kim, H. (2021). Structural and Functional Changes and Possible Molecular Mechanisms in Aged Skin. International journal of molecular sciences, 22(22), 12489. doi:https://doi.org/10.3390/ijms222212489

 

Mathew-Steiner, S. S., Roy, S., & Sen, C. K. (2021). Collagen in Wound Healing. Bioengineering (Basel, Switzerland), 8(5), 63. doi:https://doi.org/10.3390/bioengineering8050063

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Pandey, A., Jatana, G. K., & Sonthalia, S. (2023). Cosmeceuticals. StatPearls Publishing [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK544223/

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Papaccio, F., D Arino, A., Caputo, S., & Bellei, B. (2022). Focus on the Contribution of Oxidative Stress in Skin Aging. Antioxidants (Basel, Switzerland), 11(6), 1121. doi:https://doi.org/10.3390/antiox11061121

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Roger, M., Fullard, N., Costello, L., Bradbury, S., Markiewicz, E., O'Reilly, S., . . . Przyborski, S. (2019). Bioengineering the microanatomy of human skin. Journal of anatomy, 234(4), 438-455. doi:https://doi.org/10.1111/joa.12942

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Shin, J. W., Kwon, S. H., Choi, J. Y., Na, J. I., Huh, C. H., Choi, H. R., & Park, K. C. (2019). Molecular Mechanisms of Dermal Aging and Antiaging Approaches. International journal of molecular sciences, 20(9), 2126. doi:https://doi.org/10.3390/ijms20092126

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Tortora, G. (2018). Principles of Anatomy and Physiology (2nd ed.). Wiley.

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