Note that the skin is the major barrier between the inside and outside of your body.
Without these defense mechanisms, water and moisture would leak out, we’d be very susceptible to pathogens crossing the single squamous epithelium (SSE) and we’d be subjected to the daily harmful UV rays of the sun.
I want to reiterate the important functions of the skin.
Protection : it protects against UV light, mechanical, thermal and chemical stresses, dehydration and invasion by micro-organisms.
Sensation : skin has receptors that sense touch, pressure, pain and temperature.
Thermoregulation : various features of the skin are involved in regulating temperature of the body. For example sweat glands, hair, and adipose tissue.
Metabolic functions: subcutaneous adipose tissue is involved in production of vitamin D, and triglycerides.
(There’s a purpose to why SSE are located in the capillaries, lung alveoli, glomeruli, mainly because this lining functions for rapid diffusion of gases, nutrients and wastes rather than protecting the host from gargantuan external threats.)