Our skin, which has about 5 million sensory cells overll, is the main organ of the sense of touch. While your other four senses (sight, hearing, smell, and taste) are located in specific parts of the body, your sense of touch is found all over. The skin is one of the bodies largest and most complex organs. His weighs is between 1.5 and 2.5 kilograms. Skin is made up of two layers:
- The epidermis is the outermost layer which provides waterproofing and serves as a barrier to infection. The top part of the epidermis is a layer of dead skin cells. These flake off and are replaced all the time. Also In the epidermis are the melanocyte a cell type that produces pigment (melanin). That color protects the lower layers of the skin from harmaful ray of the Sun.
- The dermis or the layer beneath the epidermis. It contains hair follicles, nerve endings, sweat glands, blood vessels. (see in the figure) ant the different touch receptors.
The skin is not equally thick al over your body. The soles of your feet are the thickest. And the eyelid has the thinnest skin on the entire body.
The dermis is filled with many tiny nerve endings which give you information about the things with which your body comes in contact. The most common receptors are heat, cold, pain, and pressure or touch receptors. Pain receptors (nociceptors) are probably the most important for your safety because they can protect you by warning your brain that your body is hurt. In the figure you can see the differnt types of receptors.
Some parts of your skin have more nerve endings that other parts, so some parts are more sensitive to touch than others are. Your fingertips, tongue, and lips have the most nerve endings. You do not only have sense of touch on the outside of your body, you also have touch sense in the inside of your body.
Finally, in this link you have play and learn activities about the senses.