biomedicalephemera:“Van Gogh gave you an ear? Well I’ll give you my entire skin!”The ski

biomedicalephemera:“Van Gogh gave you an ear? Well I’ll give you my entire skin!”The skin is the largest organ in the human - and yes, its secretory and absorptive properties mean that it’s an organ!In the adult human, the surface area of our epidermis (the only exposed layer of the skin) is approximately 1.5-2.0 square meters (16.5-21.5 sq. ft.).There are six primary functions of the skin (some argue seven, including aesthetics and signalling to other members of our tribe), and two secondary functions:Physical barrier protecting from pathogens and environmental damage.Sensory receptor: Nerve endings perceive touch, temperature, pressure, and vibration.Heat regulation: There are far more blood vessels in the skin than are needed to supply its living cells - when the body is overheated it pumps blood out to the skin to radiate heat away from the body.Evaporation control: A separate aspect of heat regulation is controlling the sweat output of the skin, allowing evaporative cooling. Because of the way the epidermis is structured, sweat can escape, but can’t be reabsorbed, and removes heat from the skin as it evaporates.Water resistance: Along with letting water out of the body, it also doesn’t let water into the body! The connective tissue between the epidermal layers creates a membrane with a low enough permeability to allow us to survive away from water.Storage and Synthesis: Skin is a significant storage site for both water and fats, and synthesizes vitamin D from cholesterol stored near the top layer of the dermis.(Secondary) Excretion: While water is the primary component of sweat, the skin also secretes urea. However, urine excretes more than 100x more urea, and the urea excretion is secondary to evaporative cooling.(Secondary) Absorption: The skin is quite good at absorbing fat-soluble molecules, but it did not evolve in order to do this. Rather, it evolved to repel water, which in turn made it very lipophilic. This trait is used in medicine, with patches and creams that are absorbed through the surface of the skin.Skin is nothing short of a hard-working organ that deserves at least as much credit as your lungs. Blemishes and spots and “discolorations” are no detriment to its functionality - love the skin you’re in! It’s one of the most important reasons why you’re not constantly sick!Anatomia del corpo humano. Juan Valverde de Amusco, 1560.Early modern medical illustration: gorgeous, if perhaps not for the faint of heart! -- source link

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