Title

Key Vocabulary:


  • Epidermis: Protecting the body from the outside as the outermost layer, keeping your skin hydrated, producing new skin cells, and determining your skin color.

  • Dermis: The middle layer of skin, contains collagen, blood vessels, glands, hair follicles, and nerve endings support and protect the skin and deeper layers, assist in thermoregulation, and aid in sensation.

  • Hypodermis (subcutaneous): The innermost layer of skin, storing energy, connecting the dermis layer of your skin to your muscles and bones, insulating your body, and protecting your body from harm.

  • Dermal papillae: Regulate hair growth, protrusions of dermal connective tissue into the epidermal layer.

  • Melanocytes: Produce and distribute melanin, which is a skin pigment.

  • Stratum corneum: First line of defense against the environment.

  • Stratum lucidum: Thin somewhat translucent layer of cells lying superficial to the stratum granulosum and under the stratum corneum, found especially in thickened parts of the epidermis (as of the palms or the soles of the feet).

  • Stratum granulosum: Accumulate dense basophilic keratohyalin granules that contain lipids helping to form a waterproof barrier which prevents fluid loss from the body.

  • Stratum spinosum: This layer mostly consists of keratinocytes held together by sticky proteins called desmosomes, helping make your skin flexible and strong.

  • Stratum basale: Deepest of the five layers of the epidermis, contains the only layer where the proliferation of skin cells can occur and attaches epidermis to the dermis.




Introduction:


The skin is the body’s largest organ which includes many organs and glands that are crucial for the regulation of temperature and protection of the body. The baseline knowledge of this body system will significantly support your future success in the nursing program. The mastery of the anatomical and physiologic components of the integumentary system will now be pivotal as you learn a variety of disease processes, disorders, and other abnormalities in the nursing program.




The Epidermis:


The skin contains 2 layers and a subcutaneous layer. The superficial layer is called the epidermis. The epidermis consists of stratified epithelium tissue arranged in layers called strata. Deep to the epidermis is the dermis. The dermis consists of loose connective tissue and a number of other structures we will investigate later. The deepest layer is the subcutaneous layer that consists of loose connective tissue and adipose tissue along with blood vessels and nerves.

The epidermis consists of stratified squamous epithelium arranged in layers or strata. The layers are:

  • Stratum corneum

  • Stratum lucidum

  • Stratum granulosum

  • Stratum spinosum

  • Stratum basale

The epidermis is anchored to the dermis by means of a basement membrane. The epidermis does not contain any blood vessels. The cells of the stratum basale are nourished by the blood vessels in the dermis. These cells can divide and move toward the surface pushing the old cells off of the superficial layers. 

The stratum corneum is the most superficial layer of the epidermis. It consists of cells that have been hardened with keratin. Keratin is secreted by cells located in the deep layers of the epidermis called keratinocytes.

The stratum lucidum is an additional layer that is found only in the palms of the hands and soles of the feet. It provides an added thickness to these layers.

The stratum granulosum contains cells that have lost their nuclei. These cells remain active and secrete keratin. The cells contain granules in their cytoplasm that harbor keratin.

The stratum spinosum contains cells called prickle cells. These cells have small radiating processes that connect with other cells. Keratin is synthesized in this layer.

The stratum basale or basal cell layer contains epidermal stem cells. This is the deepest layer of the epidermis. It consists of one layer of cells that divide and begin their migration to the superficial layers. This is the layer where basal cell cancer develops.

As we have seen, there are a good number of keratinocytes located in the epidermis.

Psoriasis is an abnormality of keratinocytes. Keratinocytes abnormally divide rapidly and migrate from stratum basale to stratum corneum. Many immature cells reach the stratum corneum producing flaky, silvery scales (mostly on knees, elbows and scalp). The epidermis also responds to the environment. Friction causes the formation of corns and calluses.

Another kind of cell found in the epidermis is the melanocyte. This cell produces the pigment melanin that gives skin its color. Melanocytes are located in the deepest portion of the epidermis and superficial dermis.

The color of the skin results from the activity of the melanocytes, not the number. Melanocytes are located in the deepest layer of the epidermis. They respond to ultraviolet radiation by producing more melanin pigment which turns skin a darker color. Melanocytes respond to UVB radiation (approximately 320 nm wavelength). The hair and middle layer of the eye contain melanocytes. A condition known as malignant melanoma can develop in melanocytes.