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- Valentine Du Bois
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The skin is the largest organ of the human body and has numbers of essential functions. There are three main layers : the epidermis, the dermis, and the hypodermis.
THE EPIDERMIS : protection
The epidermis is the outermost layer of the skin and acts as a barrier against the entry of pathogens as well as maintaining fluids inside the body. The epidermis is made up of 80% keratinocytes, cells that produce keratin, a fibrous protein that gives the skin its toughness. The first layer of the epidermis, called the "stratum corneum", is made up of dead cells that are continuously replaced, held together by epidermal lipids with hydro-retaining powers. The epidermis also carries melanocytes, cells that produce melanin pigments, which form an "umbrella" over the cell nucleus, protecting the DNA from highly mutagenic UV rays.
THE DERMIS : strength and elasticity
This thick intermediate layer owes its elasticity and resistance to collagen and elastin. The dermis also contains hair follicles, sebaceous glands and sweat glands
+ Hair follicles : in humans, hairs contribute slightly to thermoregulation and provide protection against debris (eyelashes, eyebrows).
+ Sebaceous glands : they produce and release sebum into the hair follicle. Sebum is a combination of lactic acid, acidifying the skin, and lipids, preventing skin dehydration.
+ Sweat glands : they produce sweat, contributing to thermoregulation.
HYPODERMIS : insulation et irrigation
The hypodermis (or subcutaneous tissue) is made up primarily of cushion-like adipose lobules that pad and insulate the body. The hypodermis also contains blood vessels and nerves that extend to the dermis.
References :
Marieb, Elaine, et Katja Hoehn. 2014. Anatomie et physiologie humaines. Pearson Education France.
Pocock, Gillian, Christopher D. Richards, et David A. Richards. 2018. Human Physiology. Oxford University Press.
Par Valentine Du bois
Master's degree in medical biology, University of Lausanne, Switzerland
Valentine holds a Master's degree in medical biology from the University of Lausanne, following a Bachelor's degree from the University of Geneva. During her Masters, Valentine specialised in the fields of pharmacology and toxicology, focusing on applied laboratory research for the development of new treatments.
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