Understanding the Body's Largest Organ: The Skin

Understanding the Body's Largest Organ: The Skin

Let's go back to Biology and talk about your skin.

What did you think when you learned about organs?

Were you surprised to find out that the skin is an organ?

How surprised were you to find out that it is the largest organ of the body?

Each organ serves a specific purpose. And, of course, the functions our skin serves are vital to our well-being.

As your first line of defense, your skin is susceptible to injuries and wounds. The wounds can sometimes be superficial and heal quickly, while others can be deeper and require expert medical treatment.

Some of you may not remember what you learned in Biology. Let's take a look at what we know! 

The Skin1

Skin is one of the most important organs that covers the outside of the body, providing a barrier against pathogens and environmental injuries. It is the biggest organ of the body, covering the entire outside of the body, with a thickness of about 2 millimeters and a weight of about six pounds. The skin protects the body from heat, light, injury, and infection. In addition, the skin is responsible for regulating body temperature, gathering sensory information from the environment, storing water, fat, and vitamin D, and protecting us from disease.

Layers of The Human Skin

The Human Skin Consists of How Many Layers?

It consists of three main layers:

  1. Epidermis
  2. Dermis, and 
  3. Hypodermis


The Skin's Layers and Their Functions2,3,4,5,6

1. Epidermis


Skin's epidermis is the protective layer that prevents harmful bacteria, viruses, and foreign substances from reaching deeper layers. Due to the presence of melanocytes, it prevents the loss of water from the skin and also determines its color.         


Epidermis Consists of The Following Layers:

A. Stratum Basale

The lowest layer of the epidermis is composed of keratinocytes, melanocytes, and tactile cells. These keratinocytes undergo continuous cell division and are pushed toward the epidermis' upper layers.

It is a type of cell composed of keratin, a fibreous protein that influences both the structure and the hardness of skin, hair, and nails. The cells in this layer are attached to the dermal layer of the skin via collagen fibers, referred to as the basement membrane.

B. Stratum Spinosum

This layer is comprised of daughter keratinocytes and dendritic cells, which protect the body from infections. The stratum spinosum appears shiny due to protruding structures called desmosomes.

C. Stratum Granulosum

Three to five layers of Keratinocytes make up this layer. The changes in keratinocytes that have been pushed to this layer cause it to appear grainy.

D. Stratum Lucidum

There are dense keratinocyte cells here, with seleiden, a lipid-rich transparent protein. The thick skin on your hands and feet is transparent due to seleiden.

E. Stratum Corneum

There are 15-30 layers of dead keratinized cells in this layer. Every four weeks, they are shed. As a result of the process of keratinization, or cornification, the layer gets its name. 


2. Dermis

After the epidermis is the dermis, which is composed of collagen, elastin, blood vessels, and hair follicles. It is composed of sweat glands that help flush out toxins from the body, keeping it cool. The dermal layer contains the nerve endings responsible for the sense of touch in your body. Sebum, the natural oil which keeps the skin lubricated, is also produced in this layer by sebaceous glands.


It Consists of Two Sublayers

A. Papillary Dermis

In this layer, collagen and elastin form a loose mesh. An adipocyte (fat cell), blood vessel and phagocyte (defensive cell) layer is found in the papillary layer. Furthermore, lymphatic capillaries, nerve fibers, and touch receptors are found within. 

B. Reticular Dermis

It is composed of dense, irregular, vascularized connective tissue. Elastin and collagen are present in it. Fibrous proteins such as collagen are responsible for providing the structure and elasticity of the skin. Moreover, they give skin strength. 


3. Subcutaneous Tissue

Subcutaneous tissue consists of well-vascularized, loose connective tissue and adipose tissue. The tissues that lie beneath the hypodermis, such as muscle, tendon, ligament, joint capsule, and bone. Besides maintaining the temperature, this layer acts as a cushion or shock absorber. A layer of fat in this layer is responsible for protecting your muscles, bones, and internal organs. Additionally, the layer ensures the dermis is attached to your bones and muscles.



  1. Tortora GJ, Derrickson BH. Principles of anatomy and physiology. John Wiley & Sons; 2018 May 15.
  2. InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. How does skin work? 2009 Sep 28 [Updated 2019 Apr 11]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279255/
  3. Yousef, H., M. Alhajj, and S. Sharma. "Anatomy, skin (integument), epidermis. StatPearls." Treasure Island (2020). Available from: https://www.ncbi.nlm.nih.gov/books/NBK470464/
  4. Agarwal S, Krishnamurthy K. Histology, Skin. [Updated 2021 May 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537325/
  5. Nafisi S, Maibach HI. Skin penetration of nanoparticles. InEmerging nanotechnologies in immunology 2018 Jan 1 (pp. 47-88). Elsevier.
  6. McMullen, Roger L., and Gopinathan K. Menon. "Structure and Function of Human Skin."
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