Hey everyone, I hope you are having a good day. I will be discussing in details Burns in humans. Before I start to explain about burns, let me quickly do a run-through on the skin.
The skin is the largest organ of the human body, followed by the liver, and the brain. The skin covers the entire surface of the body and serves as a barrier to protect the internal body from external environmental factors. The skin is made up of three main layers the epidermis, dermis, and subcutaneous tissue.
The Epidermis is the outermost layer of the skin. It serves as the protective barrier of the body from the environment as well as regulation of water loss from the body. The epidermis is made up of several layers of cells, including the stratum basale (the deepest portion of the epidermis), stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum (the most superficial portion of the epidermis). The stratum corneum is composed of dead skin cells that have been pushed to the surface and are constantly shed. The epidermis also contains Melanocytes which are a layer of basal cells that produce the pigment melanin that gives color to the skin.
The Dermis is the layer of skin beneath the epidermis. The dermis is made up of connective tissue, as well as blood vessels, nerves, hair follicles, and sweat glands. The dermis provides structural support to the skin, regulates temperature, and picks touch pressure and pain sensation. The papillary dermis is the uppermost layer of the dermis. It is composed mainly of loose connective tissue and blood vessels and is responsible for nourishing the epidermis. The papillary dermis is the region that holds fingerprints. The reticular dermis is the lower part of the dermis below the papillary dermis. It is made up of thicker and denser connective tissue which contains collagen and elastin fibers, providing strength and elasticity to the skin.
The Hypodermis also known as the subcutaneous layer is the last layer of the skin. It is below the dermis and is composed mainly of fat and connective tissue. It serves as a cushion and insulation for the body. It also helps to anchor the skin to underlying structures. The hypodermis has blood vessels passing through it and provides a reserve for energy sources for the body.
With the skin explained properly, what are burns?
Burns are injuries to the tissues of the skin as a result of heat, electricity, chemicals, radiation, or friction. These burns can be named depending on the source, such as Thermal burns (caused by fire, hot liquids, steam, or contact with hot surfaces), Inhalation burns, Electrical burns, Radiation burns, and chemical burns. When a burn occurs in the skin, the skin changes and this change can be on any of the skin layers. According to Jackson's model, the burn can cause damage in different zones of the skin such as the Coagulation zone, Stasis zone, and Hyperamia zone. When a burn reaches the coagulation zone, complete damage has been done to the skin, and tissue burns are irreversible and coagulative necrosis. The Stasis zone is characterized by decreased tissue perfusion. Damages in this zone are reversible if the ischemia to the skin tissues is reversed. In the Hyperemia zone, tissue perfusion is increased as they can be treated.
Understanding the depth of the burns is very important when studying burns. Burns can be superficial or Deep. When burns are superficial, it causes damage to the epidermis and the capillary layer of the dermis. They damage the keratinocytes, causing the activation of immune cells (mast cells and macrophages) in the area, and an immune response is triggered. The cytokines as a result of the burns will send signals to the pain sensory nerve which will cause people to feel pain with the type of burns. The cytokines can also cause an increase in vascular permeability which can lead to interstitial edema, which could lead to blisters if the fluid accumulates in a particular area of the skin. As a result of the fluid, superficial burns usually appear moist in appearance. In severe cases, it could lead to vasodilation and then lead to warmth in the area, as blood flows through the area, and can also lead to erythema, and blanching of the skin.
Superficial Burns can be divided into Superficial partial-thickness burns and superficial epidermal burns. In superficial epidermal burns, only the epidermis is burned. The usually affects the uppermost layer of the skin as in the case of sunburns. Superficial partial-thickness burn causes damage to the papillary layer of the dermis and this type of burn usually causes blisters since the blood vessel will increase permeability, followed by rupturing of the blisters. This burn affects the epidermis and the dermis layer of the skin, but the sensation of the skin is working perfectly causing the person to feel pain.
Deep burns go beyond the epidermis, but rather it burns through the dermis and gets to the hypodermis. These burns can damage some blood vessels in the skin, causing a lack of blood in the area. The lack of blood in the area causes the burns to be dry, and non-elastic. Deep burn destroys the receptors and nerve fibers in the skin which could lead to hypoesthesia causing the loss of sensation. Since not all the blood vessels are damaged, active blood vessels react to the cytokines that were produced as a result of the burns, increasing vascular permeability, and causing interstitial edema. These burns can lead to hypertension, and there is minimal or no pain as nerve fibers are burned.
Deep burns can be divided into Deep Partial-thickness burns and Full thickness burns. In the Deep Partial-thickness burns as the name implies, not all parts of the burns are deep. The burns can cause blisters that can rupture. The skin can still have access to the blood supply if not destroyed, it can be reddish in color, or pale if the blood vessels are damaged. They may also damage the sensory nerve fibers of the skin, which can decrease the pain sensation. In full-thickness burns, all layers of the skin are completely burned. The burn causes the skin to have a waxy white color or leathery gray color as a result of the depth of the burns. The burn causes the sensory nerves and the blood vessels to be destroyed.
