The skin: A vital organ
The integumentary system is an organ system that includes the skin and its accessory structures, to include the nails, the hair, and the sweat glands. The skin is the largest organ in the body and accounts for 15% of a person’s body weight. As a protector, our skin protects our bodies from trauma acting as a barrier to bacteria and viruses. As a receptor, the skin leads to increased and decreased stimulation of hot and cold thermoreceptors therefore acting as a ‘control center’ for our body. In addition, many sensations that include touch, tickle, pressure, vibration, temperature, and pain allow the skin to perform vital roles to deal with these sensations. And as a regulator, our skin protects us from UV rays, regulating body temperature, secreting waste products, and producing vitamin D.
The skin forms a very effective chemical, biological, and physical barrier. The following substances help provide protection: Keratin, sweat, defensins, Langerhans cells, glycolipids and melanin. First, the layers of keratinized stratified squamous epithelium form a physical barrier against pathogens, and protect deeper tissue against abrasion and heat. And second, when the body temperature rises, sweat is secreted onto the skin regularly. It is relatively acidic and salty, both of which help inhibit microbial growth. Third, the skin cells secrete Defensins that literally punch holes in bacteria, and are antibodies which help prevent the colonization of the skin. Next there are the Langerhans cells which alert the body to pathogens while dermal macrophages take over viruses and bacteria that have managed to come into the body thus far. Fifth and not quite the last, there are glycolipids, which are lipids with attached sugar groups. Found only in the plasma membrane, the account for about 5% of the total membrane lipids. These glands along with the sebaceous glands prevent both the absorption of water into the skin, and excessive evaporation of water from the skin. And last there is melanin, which is a polymer made of tyrosine amino acids are mainly responsible for the coloration or discoloration of our skin. Melanin absorbs ultraviolet (UV) radiation to protect deeper tissue from damage.
There are a number of sensations that arise from the skin in a process known as cutaneous sensation. These include touch, pressure, vibration, tickle, temperature, and pain. In sensing touch, pressure, and heat, the skin plays a significant role. The detection of these different stimuli and subsequent processing has many different functions. Many different and specialized nerve endings are required to detect such a diverse array of sensations. Nerve impulses from the receptors are conveyed via sensory nerves to the thermoregulatory center in the hypothalamus. In response to various stimuli, the sensory receptor initiates sensory transduction by creating action potentials in the same cell or in an adjacent one.
Figure 1: Structure of human sensory system
The temperature of the body must remain roughly constant at 98.6 F (37 C) in order for the underlying biochemical reactions that control the body to proceed at optimal conditions. Some conditions that