The Skin (Human Anatomy): Picture, Definition, Function, and Skin Conditions

Skin is the largest organ of human anatomy. Its function includes protecting the body against infection, regulating body temperature, providing sensation, and helping maintain balance. This article covers the structure of the skin, including the epidermis, dermis, and hypodermis; the functions of the skin; and common conditions affecting the skin.

Skin Conditions

Rashes: Nearly any change in skin appearance can be called an arash. They’re usually caused by simple skin irritation, such as dryness, scratching, or friction. But sometimes they occur because of underlying medical conditions, including allergies, infections, autoimmune diseases, and some types of cancer.

Dermatitis: A general word for inflammation of the skin, including eczema.

Atopic dermatitis (AD): An allergic disease characterized by red, swollen patches of skin covered with scaly, oozing lesions. AD affects 2 million children under age 18 each year in the United States alone.

Eczema: Skin inflammation resulting in itching and flaking. There are several different kinds of eczema.

Most commonly, it’s due to a hypersensitive immune response triggered by environmental allergens like dust mites, pollen, pet dander, insect bites, or food additives. Other causes include contact dermatitis (from irritants), seborrheic dermatitis (due to bacterial infection), psoriasis (an inflammatory skin disorder), and lichen planus (a chronic skin disorder).

Skin Tests

A skin biopsy is a medical procedure used to diagnose diseases such as cancer and infections. During the procedure, a small sample of tissue is taken from the affected area, usually the arm or leg. This tissue is sent to a laboratory where it is analyzed under a microscope. If there are no signs of disease, the sample is discarded. But if the sample contains cells or structures associated with a particular disease, doctors can determine whether the person has that disease.

The most common type of skin test involves injecting a substance into the patient’s skin. For example, tuberculin tests for latent tuberculosis infection. After the injection, the patient is monitored for swelling, redness, or other symptoms that indicate an allergy reaction. These types of tests are called intradermal injections because the substance is injected directly into the dermis layer of the skin.

Tuberculosis skin tests involve injecting purified proteins extracted from the Mycobacterium tuberculosis bacteria. When the body encounters these proteins, immune system cells release chemicals known as cytokines. Cytokine levels increase during a positive skin test response. Doctors use these responses to confirm a diagnosis of active tuberculosis.

Skin Treatments

Cellulitis is a common skin infection caused by bacterial infections. Cellulitis usually affects the lower legs, buttocks, thighs, and arms. A person with cellulitis may feel pain and discomfort. In addition, he or she may notice redness, swelling, warmth, and tenderness.

The cause of cellulitis is usually a staphylococcus infection. This type of infection is spread via contact with infected areas such as cuts, burns, wounds, insect bites, or sexual contact. Once the body becomes infected, it releases chemicals called cytokines into the bloodstream. These cytokines activate white blood cells, which attack the bacteria.

Topical corticosteroid creams can help treat mild cases of cellulitis. Oral antibiotics may be prescribed for severe cases. Antifungal medications may be added to treat fungal infections.

Structure and functions of the skin

The skin is the largest organ in our bodies. It protects us against environmental factors such as cold weather, wind and sun exposure. It also helps regulate temperature and maintain water balance. In addition, it provides sensory information about touch, pain and pressure.

Skin is composed of three distinct layers: the epidermis, dermis and hypodermis. The surface of the skin is called the stratum corneum. It consists of dead keratinocytes and contains sebaceous glands, sweat glands and hair follicles. The outermost layer of the skin, the epidermis is mostly composed of living keratinocytes. These are produced continuously throughout life. The epidermis is covered by another layer of tissue, the dermis, which contains blood vessels, nerves, lymphatics, collagen fibers and fibroblasts. Below the dermis lies the subcutaneous layer, which is mainly fat and connective tissues.

Functions of the skin

The human body consists of about 10 pounds of skin. Skin protects us from external elements like cold weather, water and wind, while providing protection against internal elements such as bacteria, viruses and toxins. Our skin also provides a sensory organ to help us feel touch, temperature and pain. In addition, it acts as an important defense mechanism.

Skin is composed of three layers; epidermis, dermis and hypodermis. Epidermis is the outermost layer of the skin. It contains dead cells called keratinocytes, which are constantly being replaced. Keratinocytes produce the protein keratins, which make up hair and nails. Dermis is the middle layer of the skin. This layer is mostly composed of connective tissue. Hypodermis is the deepest layer of the skin. Here lies the muscle and fat tissues.

What does skin do?

Skin has a lot of different purposes. It protects our bodies against dangerous things like water, heat and UV radiation, while keeping us warm and moist. But it also provides information about our health and helps regulate our body temperature. In fact, changes in skin color or structure are often a sign of a medical problem.

For example, people with too little red blood cells in their bloodstream may look pale, and those suffering from hepatitis have yellowish skin because their liver isn’t functioning properly.

The outer layer (epidermis)

Your skin is composed of three different types of tissue: Epithelium, connective tissue, and hair follicles. Your epithelial tissue is the most visible part of your skin, and it consists of several layers. The outermost layer of your skin is known as the epidermis. This layer contains dead cells that form a protective barrier against bacteria, viruses, chemicals, and physical damage. Keratinocytes make up the bulk of the epidermal cells. They are responsible for producing the protein keratin, which gives our skin its strength and helps keep it waterproof. As we age, our bodies begin to lose some of these cells, causing wrinkles and fine lines.

The middle layer (dermis)

Underneath our outermost layer of skin is another one. This is called the dermis. It’s made up of a dense, fibrous meshwork of collagen and elastin, which gives us strength, flexibility and resilience. But there’s a catch: if you stretch the skin too much, it can rip apart. And sometimes that happens. A ripped dermis looks like little wrinkles or even lines. They are called stretch marks.

The deepest layer (subcutis)

The subcutis is the outermost layer of skin. This layer consists mainly of adipose tissue, blood vessels, nerves, lymphatic vessels, hair follicles, sweat glands and sebaceous glands. It is also called the hypodermis because it lies beneath the epidermis.

In humans, it covers most of the body except for the palms of the hands, soles of the feet, face, scalp, and external genitalia. It is thicker in some areas than others. For example, the thighs are covered with about 2 cm of fat while the arms are covered with about 0.5 cm.

The subcutis contains two types of fat: white adipose tissue and brown adipose tissue. White adipose tissue is found throughout the entire body and is used primarily for heat production. Brown adipose tissue is located around the neck, chest, abdomen, buttocks, and legs. It produces heat due to increased activity of mitochondria within its cells.

The subcutaneous layer is divided into three layers: superficial fascia, deep fascia, and muscle fascia.

Superficial Fascia

This layer is composed of loose connective tissue containing blood vessels, lymphatics, nerve endings, and sensory receptors. It is continuous with the dermis.

Deep Fascia

This layer connects the superficial fascia to the muscles. It is thickest at the back of the head, where it forms the cervical fascia. It is thinner elsewhere on the body.

Muscle Fascia

This layer surrounds all voluntary muscles. It is composed of bundles of fibers that attach to bones. It is continuous with both the superficial fascia and the deep fascia.

How does it work?

Your skin has many functions besides keeping you warm. It protects your internal organs from injury and infection, keeps harmful substances out of your body, and provides an interface between your body and the outside world.

It does this by acting as a barrier to prevent water loss through evaporation. Water evaporates from the surface of the skin, leaving behind a thin film of air. This prevents moisture from escaping into the environment. If the skin were not present, the body would quickly dry out.