The structure and function of the skin
The thickness of the skin varies depending on where it is located, with thicker skin being found on body parts that are subject to friction or wear and tear, such as the palms of the hands and the soles of the feet.
A layer of fatty tissue that is sometimes referred to as the hypodermis supports the skin. This fatty region is crucial for insulation as well as acting as a cushion to protect the body.
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The epidermis
The epidermis, the outer layer of the skin, is divided into five layers and is composed of stratified squamous epithelium, hair follicles, sebaceous glands, and sweat glands. It is made up of rete pegs, projections that maintain skin integrity during stress. Melanocytes, located in the deepest layer of the epidermis, produce melanin, which helps protect the body from harmful sun rays. The stratum corneum, a protective layer, is formed by stratified squamous epithelium.
02
The dermis
The dermis is a layer of the skin that provides physical support and nutrients to the epidermis. It consists of two layers: the papillary layer and the reticular layer. Key substances in the dermis include elastin, fibrillin, and collagen, which provide support and protection.
As the skin ages, these substances decrease. The dermis also contains nerve endings, sweat glands, sebaceous glands, hair follicles, and blood vessels. The papillary dermis contains smaller blood vessels that supply oxygen, elastic fibers, and nutrients to the lower epidermis. Nerve endings sense pain, touch, temperature, and pressure, and are vital for the body's protective mechanisms.
Sweat glands produce sweat, which contains body waste products, water, and salt, and evaporates, cooling the body. Sebaceous glands secrete sebum into hair follicles, which keep the skin moist and act as a barrier against foreign substances. Hair follicles produce various hair types, affecting appearance and protecting the body from injury. Blood vessels within the dermis regulate temperature. The reticular layer contains dense connective tissue, larger blood vessels, elastic fibers, and collagen bundles. Key cell types within the reticular layer include fibroblasts, mast cells, lymphatic vessels, epidermal appendages, and ground substances. These cells support the cells within the dermis and provide structure to the area.
03
Hypodermis (subcutaneous tissue)
The hypodermis provides support for the dermis and is made up largely
of fatty and connective tissue. It is essential for protection of internal
structures and also provides insulation.
References
Bianchi, J., Page, B., & Robertson, S. (2022, November 11). Common skin conditions explained. InfoBooks.org. https://www.infobooks.org/pdfview/486-common-skin-conditions-explained-janice-bianchi-barbara-page-sheila-robertson/