What Are 3 Functions Of The Skin – The skin is the largest organ in the body and functions as part of the integumentary system, which works to protect the body from various types of damage. Your skin protects you from environmental factors, ultraviolet radiation, chemicals, weather conditions and microbes. The skin also contains nerves that allow us to access sensations such as touch, heat and cold.
There are three main layers of skin that offer all this incredible protection and more. Continue reading Florida Dermatology and Skin Cancer Center’s guide to skin layers and their functions.
What Are 3 Functions Of The Skin
The epidermis is the waterproof outer layer of the skin and the body’s first line of defense against environmental elements, ultraviolet radiation, bacteria and other germs. It is composed of 4-5 sublayers of packed cells. The epidermis is responsible for the cell renewal cycle: dead skin cells are shed from the stratum corneum (the superficial sublayer of the skin visible to the naked eye) and replaced by new, healthy cells that originate in the deeper sublayers of the epidermis. The epidermis also includes the pores, which allow oil and dirt to escape from the body.
The Three Layers Of Skin And Their Functions
The dermis is the skin layer below the epidermis. This skin layer contains connective tissue and houses the body’s hair follicles, sweat and oil glands and blood vessels. The dermis also contains nerve endings that are responsible for sending messages to the brain when you burn your hand on a hot stove or feel itchy on the back of your neck. Blood vessels found in the dermis help supply fresh blood to the skin and transport the oxygen and nutrients it needs to stay healthy.
The hypodermis is made of subcutaneous fat (under the skin), connective tissue, blood vessels and nerve cells. It is the skin layer where fat is deposited and stored. The blood vessels in the hypodermis are larger and connect to the rest of the body. Stored fat helps regulate body tissue and protects the body’s internal organs from shocks, hard impacts, and falls.
At Florida Dermatology and Skin Cancer Centers, our doctors are experts in hair, skin and nails. We offer a variety of services in general dermatology, cosmetic dermatology, skin cancer treatment and Mohs skin cancer surgery. Contact one of our offices today to schedule an appointment. The skin consists of two main layers: a superficial epidermis and a deeper dermis. The epidermis consists of several layers, the topmost layer consists of dead cells that periodically come off and are successively replaced by cells that are formed from the basal layer. The dermis connects the epidermis to the hypodermis and provides strength and elasticity due to the presence of collagen and elastin fibers. The hypodermis, deep down to the dermis of the skin, is the connective tissue that connects the dermis to underlying structures; it also houses adipose tissue for fat storage and protection.
Although you don’t normally think of the skin as an organ, it is actually made up of tissues that work together as a single structure to perform unique and critical functions. The skin and its accessory structures make up the integumentary system, providing total protection to the body. The skin is made of several layers of cells and tissues, held together by underlying structures of connective tissue (Figure 1). The deepest layer of the skin is well vascularized (it has many blood vessels). It also has many sensory, autonomic and sympathetic nerve fibers that ensure communication to and from the brain.
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Figure 1. The skin consists of two main layers: the epidermis, made of compacted epithelial cells, and the dermis, made of dense, irregular connective tissue that houses blood vessels, hair follicles, sweat glands, and other structures. Underneath the dermis is the hypodermis, which mainly consists of loose connective tissue and adipose tissue.
The skin consists of two main layers and a closely associated layer. Watch this animation to learn more about skin layers. What are the basic functions of each of these layers?
The epidermis consists of keratinized stratified squamous epithelium. It consists of four or five layers of epithelial cells, depending on where they are found in the body. It has no blood vessels inside it (that is, it is avascular). Skin that has four layers of cells is called “thin skin.” From deep to superficial, these layers are the stratum basale, stratum spinosum, stratum granulosum, and stratum corneum. Most skin can be classified as thin skin. “Thick skin” is only found on the palms of the hands and soles of the feet. It has a fifth layer, called the stratum lucidus, which lies between the stratum corneum and the stratum granulosum (Figure 2).
Figure 2. These images show cross-sections of the epidermis and dermis of (a) thin and (b) thick skin. Note the significant difference in the thickness of the thick skin epithelium. From above, LM × 40, LM × 40. (Micrographs provided by Regents of University of Michigan Medical School © 2012)
The Integumentary System (skin, Hair, Nails): Anatomy And Function
Cells in all layers except the stratum basale are called keratinocytes. A keratinocyte is a cell that manufactures and stores the protein keratin. Keratin is an intracellular fibrous protein that gives hair, nails and skin their hardness and water-resistant properties. The keratinocytes in the stratum corneum are dead and shed regularly and are replaced by cells from the deeper layers (Figure 3).
Figure 3. The epidermis is an epithelium consisting of several layers of cells. The basal layer consists of cuboidal cells, while the outer layers are squamous, keratinized cells, so that the entire epithelium is often described as keratinized stratified squamous epithelium. LM × 40. (Micrograph provided by the Regents of the University of Michigan School of Medicine © 2012)
See the University of Michigan WebScope to explore the tissue sample in more detail. If you zoom in on the cells in the outermost layer of this section of skin, what do you see in the cells?
If you zoom in on the cells in the outermost layer of this skin section (Figure 3), what do you notice about the cells?
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These cells have no nucleus, so you can assume they are dead. They seem to peel off.
Stratum basale (also called stratum germinativo) is the deepest epidermal layer and connects the epidermis with the basal lamina, below which lies the layer of dermis. The cells in the stratum basale are attached to the dermis by interweaving collagen fibers called the basement membrane. A finger-shaped projection, or fold, known as a dermal papilla (plural = dermal papillae) is found in the superficial part of the dermis. Dermal papillae increase the strength of the connection between epidermis and dermis; the greater the bend, the stronger the connections are made (Figure 4).
Figure 4. The epidermis of thick skin has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum and stratum corneum.
The stratum basale is a single layer of cells made mostly of basal cells. A basal cell is a cube-shaped stem cell that is a precursor to the keratinocytes in the epidermis. All keratinocytes are produced from this single layer of cells, which constantly undergo mitosis to produce new cells. As new cells form, existing cells are pushed superficially away from the stratum basale. Two other cell types are scattered among the basal cells in the stratum basale. The first is a Merkel cell, which acts as a receptor and is responsible for stimulating the sensory nerves that the brain perceives as touch. These cells are especially abundant on the surfaces of the hands and feet. The other is a melanocyte, a cell that produces the pigment melanin. Melanin gives color to hair and skin and also helps protect the living cells of the epidermis from damage caused by ultraviolet (UV) radiation.
High Proliferation And Delamination During Skin Epidermal Stratification
In a growing fetus, fingerprints form where cells in the stratum basale meet the papillae in the underlying dermal layer (papillary layer), resulting in ridges on the fingers that you recognize as fingerprints. Fingerprints are unique to each individual and are used for forensic analysis because the patterns do not change with growth and aging processes.
As the name suggests, the stratum spinosum has a spiky appearance due to the protruding cellular processes that hold the cells together through a structure called the desmosome. Desmosomes connect and strengthen the bond between cells. It is interesting to note that the “sticky” nature of this layer is an artifact of the staining process. Unstained epidermal samples do not exhibit this characteristic appearance. The stratum spinosum consists of eight to 10 layers of keratinocytes, formed as a result of cell division in the stratum basale (Figure 5). Interspersed between the keratinocytes in this layer is a type of dendritic cell called a Langerhans cell, which acts as a macrophage that engulfs bacteria, foreign particles, and damaged cells present in this layer.
Epidermal cells are derived from stem cells in the stratum basale. Describe how cells change as they integrate into different layers of the epidermis.
As the cells move into the stratum spinosum, they begin to do so