One thing I’ve become obsessed with recently is skincare. I’ve tried learning everything there is to know about skin, skincare products and the truth behind myths and old wives tales. One thing that helped me, and hopefully you, get a grip on taking care of my skin was learning basic anatomy of the skin! Once you know the anatomy and function of healthy skin and what it needs to stay happy and healthy taking care of your skin becomes an easier task. By understanding how everything works together and what your body needs and what it is made of you can pin point what you need or want to address or be able to see the signs and causes of your skin concerns.
This post will just be a quick rundown of the layers, components and function of the skin layers with the emphasis on cosmetic skin care. This won’t really go to deep into nerves, blood vessels or the subcutaneous fat layer. So if you want to know what makes skin tick, continue reading.
Skin has three layers: Epidermis, Dermis and the deeper subcutaneous tissue (Hypodermis) is made of fat and connective tissue. The first two are the most important to skin care.
Let’s start with the Epidermis. The Epidermis is the top layer of skin and it acts as a tough and waterproof barrier of your insides to the outside world. It also is what creates our skin tone. The epidermis is mostly dead skin cells; composed of keratin or keratinocytes, a protein that provides the tough structure, and melanin or melancocytes, which give your skin its color. The epidermis can vary from .05mm thick (on thin areas like the eyelids and lips) to 1.5mm thick (thicker on the palms and soles of the feet) all over your body. The epidermis consists of 5 layers of its own.
- Stratum Corneum: the stratum corneum is made up of dead skin cells, called keratinocytes. These keratinocytes are constantly being shed and replaced by newer cells which work their way up from lower layers. Keratinocytes are replaced every 2 weeks in a process called desquamation. Naturally occurring ceramides are also found in this layer.
- Stratum lucidum: the stratum lucidum is also made of dead skin cells as well, but they are flattened and used to cushion between the stratum corneum and the stratum granulosum. This layer is responsible for thick skin and not present in thin skin areas.
- Stratum granulosum: the stratum granulosum is where keratin is made. This layer is important in creating keratin and skin protecting materials that help waterproof the skin to prevent transepidermal water loss (TEWL).
- Stratum spinosum: more keratin-producing cells.
- Stratum basale: the stratum basale is the lowest layer of the epidermis. The cells of this layer continuously divide and form new keratinocytes to replace the ones that are constantly shed. This layer also has melanocytes, which are the cells that are responsible for skin coloring. The stratum basale has cells that are shaped like columns. In this layer the cells divide and push already formed cells up into higher layers. As the cells move into the higher layers, they flatten and eventually die.
The epidermis is also covered by a barrier, sometimes referred to as the “acid mantle” which creates an inhospitable environment for bacteria and pathogens, protecting the body from diseases and infections. This barrier is also sometimes called the “lipid barrier“, created by the mixing of sebaceous excretions and kertatinocytes, and when it’s referred to as the lipid barrier, it usually in the context of how it helps our skin stay moisturized and control the amount of moisture or water passed or lost through our skin, also called “TransEpidermal Water Loss” (or TEWL).
The Dermis, or the second layer of skin, is where a lot of the structure and the appearance of your skin takes place. What the dermis contains also are main concerns for skin care, as the dermis is where the hair follicles are, the sweat glands and sebaceous glands and where the collagen is. The dermis is comprised of three different types of cells, fibroblasts(collagen and structure), macrophages(healing white blood cells), and adipocytes(stores fat/lipids).
Hair follicles are in the dermis, and are what we commonly call “pores” and these are the only pore that can develop acne or folliculitis. But there are other types of pores, such as sweat pores, but these do not commonly get blocked and cause comedones. If a hair follicle gets blocked by sebum (which is made in the sebaceous glands, located right adjacent to the hair follicles and also in the dermis layer) or keratin it will continue to build up behind the blockage and cause a visible comedone, or pimple.
The dermis is comprised mostly of collagen, whereas the epidermis is made up of mostly dead skin cells. The dermis is also important when it comes to skin care, because of the future damage it can hold. UV rays can penetrate and affect collagen’s DNA in the dermis. The dermis is what makes skin look young, full, youthful and bouncy. Getting products to penetrate to this layer, and also taking care of the structure of this layer by protecting it from damage (such as from the sun), is important to keeping your skin healthy and beautiful for many years to come.
Terms to Know:
Epidermis: The top layer of skin, comprised mostly of dead skin cells, but protects the lower levels from pathogens and excessive moisture loss.
Dermis: The second layer of skin, where the structure-forming collagen is, the healing white blood cells are, and the shape-giving lipids are stored and created.
Keratin: What skin, nails and hair are made out of. It is produced in the epidermis, is constantly being shed and replaced.
Sebum: A waxy, oily substance created in the sebaceous glands. It’s purpose it to lubricate, moisturize and protect the skin. After it’s created in the sebaceous glands in the dermis, it travels up hair follicles to be deposited on the surface of the skin. Commonly referred to as “oil” when discussing skin care.
Hair Follicle: The space in which a hair root and shaft are. Commonly referred to as “pores” when discussing skincare, a hair follicle is different from any other type of pore because it contains a hair root and shaft. Can be found anywhere on the body except the soles of feet and hands, lips, and eyelids.
Desquamation: Also called “skin peeling”. The process in which skin cells, or keratinocytes, are created, replaced and shed. Normal desquamation takes 2 weeks from cell creation to final shedding, but injury, trauma or illness can cause extremely quick shedding or peeling, such as from a sunburn.
Ceramides: A waxy lipid that comprises most of the topmost layer of the epidermis. It’s main function it to create a waterproof barrier to prevent TEWL and block harmful microorganisms from penetrating the lower levels of skin. Also termed “the tumor suppressor lipid”.
Transepidermal Water Loss: The process or amount of water that passes through the skin, to be lost by evaporation or diffusion.
Acid Mantle: A slightly acidic (4.5-5.5) thin layer or film the lays on top of the skin that protects the skin and body from bacteria, viruses and other harmful pathogens.
Collagen: A structural protein that gives skin it’s fullness. It is created and located in the dermis.
Comedo (Plural Comedones): Term for a clogged hair follicle in the skin. There are different types of comedones, and comedones can occur with or without Acne Vulgaris.
UV Rays: Ultraviolet light is an electromagnetic radiation that is typically invisible to the human eye. The main method of exposure to UV radiation is through sunlight. UV rays have both beneficial and harmful affects to human life.