The skin is the largest organ

The skin is the largest organ


The skin is the largest organ of our body and one of the 7 channels of elimination containing about 70% water, 25% protein and 2% lipids; the skin helps the main organs of elimination (liver, kidney, intestines) get rid of waste buildup. The skin separates the internal environment of the body from the external environment that consists of three different layers. The epidermis, which is the outer layer, made of stratified squamous, keratinizing epimelial tissue and cell keratinocytes. The stratum germinativum the innermost layer also called the stratum basale, where mitosis takes place keratinocytes produce the protein and keratin, which is relatively waterproof. The dermis which is the final layer of the skin an uneven junction of the dermis with the epidermis papillary layer accessory skin structures hair follicles, nail follicles, sensory receptors, and the glands. The skin prevents entry of many harmful substances.

The Skin has five main functions: It acts as a mechanical barrier to infections. 1) It ultimately prevents microorganisms and other substances from entering the body. Langerhans cells (a type of macrophage) are found within the dermis, they engulf invaders foreign to the body and debris. Kaeratin layers in the epidermis together with sebum produced by sebaceous glands act as a waterproof barrier. Melanocytes protect the body from ultraviolet light. Finger and toenails protect the extremities of fingers and toes from damage. Fingertips are important for dexterity and the sense of touch; they have ridged areas to assist in picking things up. Hair follicles offer some extra protection to certain parts of the body such as eyes and head. 2) Skin provides the sense of touch or sensation we need to know more about our outside environment through recognizing heat, cold, pain and other sensations. Nerve endings of the skin provide the body with a great deal of information about the outside environment. 3) It regulates body temperature. Considerable heat is lost through the skin. Even under extreme conditions of high temperature and exercise, our skin tends to make body temperature normal. The production (evaporation) of sweat in the skin cools us down when exposed to too much heat. The core body temperature needs to be kept constant for normal physiological activity to take place (370c). It needs to maintain a core temperature for homeostasis. 4) Skin excretes waste product and excess salt from the body. Sweat includes waste products in solution. Water is lost continuously through the skin as insensible sweating. More pronounced water loss through sweating occurs as a part of temperature regulation. 5) Skin synthesizes the use of Vitamin D in the presence of sunlight and ultra violet radiation needed for the absorption of calcium and phosphate.

The following is a general list of types to help you begin learning more about your best approach to personal skin care.

Oily skin:

This one may look oily and coarse, may have recurring blackheads, acne and large pores. The texture of skin is thick; the touch is often sticky. This type is usually youthful- looking due to the presence of oil on the skin. Often, individuals with oily skin have a tendency to develop acne in their teen and middle years, and overgrown oil glands, or sebaceous hyperplasia, in the middle and late years.

Normal Skin:

It is the type that we'd all love to have. This is the “healthy” type of skin. This type is the not too oily, not too dry type, characterized by few blemishes, generally firm and smooth with small pores. When you pull the skin away from the bony structure, it springs back to normal position. Lines and wrinkles are appropriate for age.

Dry Skin:

This type of skin is sensitive to hot and cold weather, and can feel tight or have visible flaking -- especially after cleansing. This one has a matte finish; small pores, and tends to become drier and more wrinkled with age compared with other types.
Many factors can cause dry skin. Sometimes it's hereditary and occurs year-round. Some people have seasonally dry skin that occurs mostly during cold, dry winter months. This type is also linked to the natural aging process.

Sensitive Skin:

A person with type has a lot more trouble with environmental factors than the average person. Skin burns more easily in the sun, there may be frequent reactions to cosmetics and rashes or a burning sensation can even develop from weather conditions. Problem skin often accompanies this skin type, as it is very reactionary.

Combination skin:

Most of us have this type, with an oily center area or a T-zone across the forehead, nose, and chin, and areas of dryness on the cheeks, and around the eyes and neck. Acne will be more active in the areas that are oily.


Our skin is our largest vital organ covering us from head to toe, but it's really the one that we present to the world every day that concerns most of us. It's on our faces; necks and shoulders that we want to have really great looking!

Ironically, those same areas are targeted areas for acne. It's where the pimples, zits, nodules and cysts grow; click here for more information about types of Acne.

The reason the problems appear here is because there are thousands of very fine hairs growing on your face, neck, back, chest and shoulders. Each hair has a tiny little gland that is attached to the hair follicle under your skin, which produces oil. When too much oil is produced, pores get clogged up with the oil and dead skin cells and an outbreak occurs. The oil production is determined by the level of hormone activity in your body.

Diagram of Skin Layers

The skin is an ever-changing organ that contains many specialized cells and structures. The skin functions as a protective barrier that interfaces with a sometimes-hostile environment. It is also very involved in maintaining the proper temperature for the body to function well. It gathers sensory information from the environment, and plays an active role in the immune system protecting us from disease. Understanding how the skin can function in these many ways starts with understanding the structure of the 3 layers of skin - the epidermis, dermis, and subcutaneous tissue.
The epidermis is the outer layer of skin. The thickness of the epidermis varies in different types of skin. It is the thinnest on the eyelids at .05 mm and the thickest on the palms and soles at 1.5 mm. The epidermis contains 5 layers. From bottom to top the layers are named:

  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum licidum
  • Stratum corneum

The bottom layer, the stratum basale, has cells that are shaped like columns. In this layer the cells divide and push already formed cells into higher layers. As the cells move into the higher layers, they flatten and eventually die.

The top layer of the epidermis, the stratum corneum, is made of dead, flat skin cells that shed about every 2 weeks. Illustration of maturation of epidermis cells There are three types of specialized cells in the epidermis.

The melanocyte produces pigment (melanin) The Langerhans' cell is the frontline defense of the immune system in the skin The Merkel's cell's function is not clearly known
The dermis also varies in thickness depending on the location of the skin. It is .3 mm on the eyelid and 3.0 mm on the back. The dermis is composed of three types of tissue that are present throughout - not in layers. The types of tissue are:

  • Collagen
  • Elastic tissue
  • Reticular fibers

The two layers of the dermis are the papillary and reticular layers.

The upper, papillary layer, contains a thin arrangement of collagen fibers.

The lower, reticular layer, is thicker and made of thick collagen fibers that are arranged parallel to the surface of the skin.
The dermis contains many specialized cells and structures.

The hair follicles are situated here with the erector pili muscle that attaches to each follicle. Sebaceous (oil) glands and apocrine (scent) glands are associated with the follicle. This layer also contains eccrine (sweat) glands, but they are not associated with hair follicles. Blood vessels and nerves course through this layer. The nerves transmit sensations of pain, itch, and temperature. There are also specialized nerve cells called Meissner's and Vater-Pacini corpuscles that transmit the sensations of touch and pressure. The subcutaneous tissue is a layer of fat and connective tissue that houses larger blood vessels and nerves. This layer is important is the regulation of temperature of the skin itself and the body. The size of this layer varies throughout the body and from person to person. The skin is a complicated structure with many functions. If any of the structures in the skin are not working properly, a rash or abnormal sensation is the result. The whole specialty of dermatology is devoted to understanding the skin, what can go wrong, and what to do if something does go wrong.

Here are just a few examples of what skin anatomy reveals about you:

Your skin's color and texture are inherited through genetics, and that provides information about your family history.

After vigorous exercise, you have a unique scent that is created by your particular combination of skin secretions from your sebaceous and sweat glands. Even the amount of perspiration can differ from one person to another.

Whether you tan or burn during sun exposure is controlled by the amount of melanin you inherited.

While the actual thickness of skin varies throughout the body, the thinnest skin (approximately 0.5mm) is found on the eyelids, and the thickest skin (approximately 4mm) is on the palms of your hands and the soles of your feet.

Despite this lack of density, your skin protects your body in remarkable ways: Skin protects body tissues and organs against injuries. The nerves in your skin receive the stimuli that tell your brain when your skin has been touched.

The nerves in your skin also help your brain respond to sensations of hot and cold. Your skin helps to regulate your body's temperature by making your pores smaller when it's cold, and making pores larger when it's hot.

Your skin is the “armor” that helps to protect your immune system from bacteria and disease. Skin keeps your essential body fluids (blood, water and lymph) from evaporating.

Your skin protects you from the sun's harmful ultraviolet rays. The amount of sun protection you have depends on the amount of melanin you inherited.
Your skin anatomy is composed of three layers, the epidermis, the dermis, and subcutaneous fat.

· Epidermis: This is the top layer of skin, and it is somewhat translucent, so light can partially pass through it. There are no blood vessels in the epidermis, so this top layer gets it's nutrients and oxygen from the deeper layers. The epidermis is attached to the next layer, the dermis, via a membrane.

· Dermis: This is the second, deeper layer of your skin. The dermis is where your hair roots and sweat glands reside, and the dermis also contains with some blood vessels and nerves.

· Subcutaneous fat: This is the bottom or lowest layer of your skin, and this is where your larger blood vessels and nerves reside. The subcutaneous fat layer is composed of fat-filled cells call adipose cells, and the depth of the subcutaneous fat layer is different from one person to another.

Subcutaneous fat is attached to your bones and muscles by connective tissue, which is loose, allowing skin to move. If you have too much subcutaneous fat, the connection points of your connective tissue become more obvious. This causes a pockmarked or rippled appearance--the dreaded cellulite.

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