The key difference between epidermis and dermis is that epidermis is the outermost layer or the upper layer of the skin while dermis is the inner layer of the skin located beneath the epidermis.
Birds and mammals are endothermic animals. In order to maintain constant body temperature, these organisms need to have a high metabolic rate and an effective means of controlling heat loss from the body surface. The skin is the organ of the body that is in contact with the external environment while monitoring and regulating the changing temperature. In fact, it is the outer covering of vertebrates. It contains connective tissue, blood vessels, sweat glands and sense cells, which carry out numerous functions. The human skin has two main layers as epidermis and dermis, which overlay the subcutaneous fat-containing adipose tissues.
What is Epidermis?
Epidermis is one of the two layers of the skin. In fact, it is the outermost layer of skin which is embryonic ectodermal in origin. It is separated from the dermis (inner layer) by a basement membrane. Most importantly, it forms a complete covering to the body perforated only by sweat gland openings and hair follicles.
Epidermis has many layers of cells, forming a stratified squamous epithelium. The basal cell layer has cuboidal cells. The outer layers have squamous keratinized cells. Moreover, the epidermis has four to five layers of epithelial cells. These layers are stratum basale, stratum spinosum, stratum granulosum, stratum corneum and stratum lucidum.
Furthermore, stratum basale is the deepest epidermal cell layer composed of a single layer of cuboidal cells. It is attached to the basal lamina. Stratum spinosum comprises eight to ten layers of keratinocytes. Keratinocytes synthesize keratin, which is a protein that makes cells waterproof. As the keratin content in cells increases, they get cornified and die. They also can be modified as nails, claws, hooves, feathers and hair in animals. Moreover, stratum corneum is the most superficial layer of the epidermis and it is in contact with the external environment. Its cells are dry and mostly dead. Cells of the stratum corneum are subject to periodic shedding. The below layer – stratum granulosum – replaces the cells of the stratum corneum.
What is Dermis?
Dermis is the inner layer of the skin which is mostly mesodermal in origin. It is a dense matrix composed of connective tissue rich in elastin fibres and contains blood capillaries, lymph vessels, muscle fibres, pigment calls, sweat glands and hair follicles.
Furthermore, the hair follicles, which are epidermal in origin, invaginate to the dermis to gain nourishment from the blood capillaries in the dermis. Sebaceous glands open into the hair follicle, which secretes sebum. The sebum keeps the skin wet and prevents water loss from the skin. At the base of the hair follicle, there is a smooth muscle called arrector pili muscle. It helps in changing of position of hair and the amount of air trapped between the hair and skin. Thus, it carries out a thermoregulatory function as well. The sweat glands in the dermis produce sweat and help in an execratory function as well as a thermoregulatory function.
In addition, there are both motor and sensory neurons in the dermis. The sensory neurons detect heat, cold, touch, pain and pressure. The blood capillaries present in the dermis supply nourishment and oxygen to both dermis and the live part of the epidermis through diffusion.
What are the Similarities Between Epidermis and Dermis?
- Epidermis and dermis are protective cell covers of animals.
- They are the two layers that make the skin.
- Moreover, the dermis lies beneath the epidermis.
What is the Difference Between Epidermis and Dermis?
The key difference between epidermis and dermis is that epidermis is the outermost layer while dermis is the inner layer. Furthermore, the dermis is mesodermal in origin while the epidermis is ectodermal in origin. In addition, epidermis modifies to form hair, nails, feathers, antlers, hooves etc, while dermis does not. This is another difference between epidermis and dermis.
The epidermis consists of both living and non-living components, but the dermis is entirely alive. This is an important difference between epidermis and dermis. In addition, the dermis contains glands capillaries, smooth muscles, pigment cells, and nerves, while the epidermis has none of these elements. Another difference between epidermis and dermis is that epidermis sheds cells constantly while dermis cannot shed cells.
Summary – Epidermis vs Dermis
Dermis and epidermis are two layers that form the basic body covering or the skin. Together, they perform the function of protecting internal organs from damage, dehydration, and disease. The cornified epidermis prevents damage by friction, while the dermis and subcutaneous tissues prevent mechanical damage. Melanin, the dark pigment in chromatophores of the dermis, protects the body from UV radiation. Moreover, the sebum and structure of the skin itself prevent the entry of pathogens. This summarizes the difference between epidermis and dermis.
1. “Epidermis.” Encyclopedia.Lubopitko, Available here.
1. “Epidermis-delimited” By Normal_Epidermis_and_Dermis_with_Intradermal_Nevus_10x.JPG: KilbadCropped and labeled by Fama Clamosa (talk) and Mikael Häggström, respectively (Public Domain) via Commons Wikimedia