The skin is the largest and heaviest organ found within the human body. In most people, the skin accounts for 15% of the person’s total body weight. Most skin is 1 to 2 millimeters thick, but can be as thin as 0.5 millimeters and as thick as 6 millimeters. Thick skin covers the palms, soles, fingers and toes. Thick skin contains no hair follicles or oil glands, but contains sweat glands. The rest of the body is covered in thin skin, which contains hair follicles, oils glands and sweat glands. The skin has six key functions in the body.
One of the most important roles the skin takes on is that of a barrier. The skin acts as a waterproof barrier, sealing the internal organs and tissues away from the external environment. The skin prevents the body from absorbing water while immersed, or losing water. The skin also acts as a protective barrier against harmful sun rays. The skin is capable of protecting the body from many foreign substances, but it is not impermeable and toxins can be introduced through the skin.
Feeling & Sensation
The skin is the largest sensory organ within the body. The skin is capable of sensing and reacting to touch, temperature and other stimuli. The skin is capable of reacting to stimuli due to the sensory receptors found within the skin. These receptors occur in great number in areas such as the palms, fingers, face, soles, and genitals.
The skin is capable of protecting the body from a great deal of injuries. The skin is injured more often than any other organ in the body but deals with injury well and is capable of recovering quicker and more easily than most organs. The skin is so durable partly because of the tightly packed keratin proteins found within it. Infectious organisms and harmful pathogens are often kept at bay due to an inability to permeate the skin. If the skin is injured, however, it is possible for foreign antigens to enter the body.
The skin is capable of reacting to both heat and cold. The skin contains special receptors known as thermoreceptors capable of detecting changes in temperature and transmitting this information to the brain. When the body becomes too hot, the blood vessels dilate, rising closer to the skin, allowing heat to be released. When the body becomes too cold, the blood vessels constrict, keeping heat as close to the core as possible.
Humans have a large variety of facial expressions made possible by the connections between facial muscles and facial skin. These expressions play a large role in non-verbal communication between humans.
Vitamin D Synthesis
The skin is responsible for the first part of vitamin D synthesis. Vitamin D is obtained through the absorption of sun rays into the skin, and is then used alongside calcium for the formation and growth of the bones. Without vitamin D, calcium would not be able to be used by the body.
Saladin, Kenneth S.. Anatomy & physiology: the unity of form and function. 5th ed. Dubuque: McGraw-Hill, 2010. Print.
Skin and It’s Function