Skin Structure and Functions

Introduction

Your skin has around 19 million skin cells and 60,000 melanocytes per inch (cells that make melanin or skin pigment). Additionally, 1,000 nerve endings and 20 blood arteries are contained within. Understanding the skin structure and functions is vital in truly understanding the science of wound healing. The skin is our body’s largest organ, measuring 18 square feet in area and weighing around 12 pounds. Regardless of its beneficial properties, the skin is always prone to injury and breakdown. Maintaining skin integrity equates to maintaining skin health, which is applicable to individuals of all ages. Due to the natural aging process of the skin, older persons are at a greater risk. As skin ages, the epidermis-dermis junction thins and flattens, limiting circulation. Moisturizing factors are also diminished in older persons, resulting in dry, flaky skin and an increased risk of skin breakdown.

Skin that is prone to injury, damaged, or incapable of healing is said to have a skin integrity problem. Skin integrity is affected by intrinsic and extrinsic variables, but extended extrinsic influences render the skin more susceptible to injury or impairment. When the skin is damaged, the risk of infection, amputation, and even death increases. Intrinsic factors can include but are not limited to, diabetes, skin problems, malnutrition, and cardiovascular illness. Extrinsic variables can include, but are not limited to, pressure, friction, shearing, falls, immobility, and surgical procedures.

 

What Are the Layers of the Skin?

The following three layers of tissue make up the skin.

  • Epidermis, the top layer.
  • Dermis, the middle layer.
  • Subcutaneous or Hypodermis, the bottom or fatty layer.

Epidermis

Your epidermis is the visible and touchable layer of your skin. Keratin, a protein found inside skin cells, is what gives skin cells their shape and, along with other proteins, forms this layer. The epidermis consists of the following:

Protects the body and bloodstream: The epidermis acts as a protective barrier, preventing bacteria and germs from entering the body and bloodstream and causing infections. Additionally, it safeguards against rain, sun, and other factors.

The epidermis is constantly producing new skin cells. These new cells will eventually replace the approximately 40,000 old skin cells shed daily by your body. Every 30 days, you receive a new layer of skin.

Safeguards your body: The epidermis’s Langerhans cells are a component of the body’s immune system. They aid in the battle against bacteria and diseases.

Melanin, the pigment that gives skin its color, is found in the epidermis. Your melanin level dictates the color of your skin, hair, and eyes. Individuals with increased melanin production have darker skin and may sunburn more quickly.

 

Dermis

The dermis accounts for 90% of the thickness of the skin. This intermediate layer of skin consists of the following:

  • Collagen and elastin: Collagen is a protein that contributes to the strength and resilience of skin cells. Elastin, another protein found in the dermis, helps maintain the skin’s flexibility. Additionally, it assists stretched skin in regaining its shape.
  • Hair follicles grow hair by attaching their roots to the dermis.
  • Maintains contact: Nerves in the dermis alert you when something is too hot to touch, itchily irritating, or excessively soft. Additionally, these nerve receptors aid in the perception of pain.
  • Produces oil: Oil glands in the dermis contribute to the skin’s softness and smoothness. Additionally, the oil protects your skin from excessive water absorption when you swim or are caught in a thunderstorm.
  • Sweat glands in the dermis produce sweat, which is released through skin pores. Sweat aids in the regulation of your body temperature.
  • Blood veins in the dermis supply nutrition to the epidermis, which helps maintain the skin layers healthy.

Subcutaneous or Hypodermis

The fatty layer is located at the bottom of the skin, the subcutaneous layer or hypodermis. The hypodermis consists of the following: 

  • Muscles and bones are cushioned by fat in the hypodermis: Fat in the hypodermis protects muscles and bones from injury when you fall or are involved in an accident.
  • Has connective tissue: This connective tissue connects the skin’s layers to the muscles and bones.
  • Contributes to the health of the nerves and blood vessels: The dermis’s (middle layer) nerves and blood vessels become larger in the hypodermis. The hypodermis is connected to the rest of the body via these nerves and blood vessels.
  • Body temperature regulation: Fat in the hypodermis prevents you from becoming too cold or hot.

Disclaimer

The views and opinions stated in this blog are exclusively those of the author and do not reflect iWound, its affiliates, or partner companies.

 

Further Reading and References

 

Yousef H, Alhajj M, Sharma S. Anatomy, Skin (Integument), Epidermis. [Updated 2021 Nov 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470464/

 

Blair MJ, Jones JD, Woessner AE, Quinn KP. Skin Structure-Function Relationships and the Wound Healing Response to Intrinsic Aging. Adv Wound Care (New Rochelle). 2020;9(3):127-143. doi:10.1089/wound.2019.1021

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