touch
36.2 | Somatosensation By the end of this section, you will be able to: Describe four important mechanoreceptors in human skin Describe the topographical distribution of somatosensory receptors between glabrous and hairy skin Explain why the perception of pain is subjective Somatosensation is a mixed sensory category and includes all sensation received from the skin and mucous membranes, as well from as the limbs and joints. Somatosensation is also known as tactile sense, or more familiarly, as the sense of touch. Somatosensation occurs all over the exterior of the body and at some interior locations as well. A variety of receptor typesembedded in the skin, mucous membranes, muscles, joints, internal organs, and cardiovascular systemplay a role. Recall that the epidermis is the outermost layer of skin in mammals. It is relatively thin, is composed of keratin-filled cells, and has no blood supply. The epidermis serves as a barrier to water and to invasion by pathogens. Below this, the much thicker dermis contains blood vessels, sweat glands, hair follicles, lymph vessels, and lipid-secreting sebaceous glands Figure 36.4 . Below the epidermis and dermis is the subcutaneous tissue, or hypodermis, the fatty layer that contains blood vessels, connective tissue, and the axons of sensory neurons. The hypodermis, which holds about 50 percent of the bodys fat, attaches the dermis to the bone and muscle, and supplies nerves and blood vessels to the dermis.