A little bit about the skin

The skin! Why do we have a whole industry worth hundreds of billion dollars just for one organ? I mean, we are not seeing proliferating kidneycare videos by nephrologists or livercare vloggers.

Well, afterall, it is the most visible organ and its appearance strongly affects our social interactions. Social media and the relentless effort to post photos and videos has taken the importance of this organ to a whole new level.

The integumentary system that consists the skin and its accessory organs-the hair, nails and cutaneous glands----is important to our self image. And Positive Self image is important to the attitudes that promote overall good health. The skin is also the most vulnerable of our organs: exposed to radiation, trauma, infections, and chemicals. So, we can all agree it does deserve the attention it gets for keeping the world out and you and I in!

The skin is the body’s largest and heaviest organ, accounting to about 15% of body weight in adults. It can cover an area of 2 sq meters, enough to cover a king size bed if you were to spread it. It consists of two layers: Epidermis and dermis. Hypodermis is technically not part of the skin but it’s often studied together with these two layers.

The epidermis, keratinized stratified squamous epithelium—in plain words means it consists of dead cells packed with the tough protein keratin. This also means, the epidermis lacks blood vessels and depends of the diffusion of nutrients from the layer underneath-the dermis. 

Okay skin color. Why do we come to this planet in different shades? There is one cell that is responsible for all the hate and discrimination we see in this world. Melanocyte cells!! Relevant to us, are found here in the epidermis at the very bottom of the layers, the stratum basale. Melanocytes synthesize the brown to black pigment melanin. Interestingly people of different skin colors have essentially the same number of melanocytes. However, in dark-skinned people like myself, the melanocytes produce greater quantities of melanin, the melanin granules in the keratinocytes are more spread out than tightly clumped and the melanin breaks down more slowly. So,the melanized cells may be seen throughout the epidermis from stratum basale to stratum corneum. In light skinned people, the melanin is clumped near the keratinocyte nucleus, so it imparts less color to the cells. It also breaks down more rapidly so little is seen beyond the stratum basale. 

The amount of melanin in the skin also varies with the exposure of the UV rays of sunlight which stimulates melanin synthesis and darken the skin. A suntan fades as melanin is degraded in older keratinocytes and as the keratinocytes migrate to the surface and exfoliate.

The outer most layer of the epidermis- stratum corneum consists of up to 30 layers of dead, scaly, keratinized cells. The deeper you go through the layers of the epidermis, the younger the cells get. These cells are continuously dying and being replaced. Dead keratinocytes exfoliate as dander. Yup, most of your expensive skincare products are going to dead cells. They say much of the house dust is from skin we shed. Regeneration happens in the lower layers and new cells move towards the surface maturing along the way where they eventually die and sluff-off from the surface of your skin. You completely replace your epidermis every 4 to 6 weeks.

Dermis: This is a connective tissue layer. It is well supplied with blood vessels, sweat glands, sebaceous glands and nerve endings. Hair follicle and nail roots are embedded here too.

Here is a video link if you wish to watch instead💚

REFERENCES

Dehdashtian, Amir, et al. "Anatomy and Physiology of the Skin." Melanoma. Springer, Cham, 2018. 15-26.

McLafferty, Ella, Charles Hendry, and Alistair Farley. "The integumentary system: anatomy, physiology and function of skin." Nursing Standard (through 2013) 27.3 (2012): 35.

Venus, Matt, Jacqueline Waterman, and Ian McNab. "Basic physiology of the skin." Surgery (Oxford) 28.10 (2010): 469-472.