The skin contains a large number of sensory nerve ending. These nerve endings are the terminal part of the protrusion around sensory neurons (pseudopolar neurons), which together with other structures make up the receptors. Sensory nerve endings according to their structure can be divided into free nerve endings and tunicaedic nerve endings two categories.
Free nerve ending: The simpler, thinner part of myelinated or unmyelinated nerve fibers loses myelination. The end of the axon is subdivided into fine branches, distributed between the epithelium of the epidermis, cornea, and hair follicles, or distributed In all types of connective tissue, such as periosteum, meninges, adventitia, joint capsule, tendon, ligament, fascia and teeth
Pith and other places. Can feel the pain, cold, heat and touch the stimulus.
Encapsulated nerve ending: The outer surface of the capsule is surrounded by connective tissue, as follows.
⑴ tactile corpuscle: Meissner, located in the dermal papillae to the finger, the majority of the skin on the palmar side of the toe, feeling touch, the number can be gradually decreased with age. Tactile body oval-shaped, long axis perpendicular to the skin surface, outsourcing of connective tissue sac, there are many small flat horizontal cells.
Myelinated nerve fibers into the body loses myelination, axons are divided into thin branches coiled in the flat cells.
⑵ lamellar corpuscle: Pacinian, larger (diameter 1 ~ 4mm), oval or spherical, are widely distributed in the subcutaneous tissue, mesentery, ligaments and joint capsule, etc., feel pressure sensation and vibration. Body capsule is composed of dozens of concentric circles arranged flat cells, the body has a central homogeneous circle
Cylinder. Myelinated nerve fibers into the body loses myelination, naked axon traverses in the body of the central cylinder.
The skin is distributed with a variety of receptors, can produce a variety of feelings. It is generally considered that there are mainly four types of skin sensations, namely, sensation of touch, pressure sensation caused by mechanical stimulation of the skin, chills and thermal sensations caused by temperature stimulation, and pain sensations caused by noxious stimulation. With different types of punctate stimuli to check the skin feel when found in different areas of feeling in the skin
The surface was independent of each other dot-like distribution. When slender hair gently touches the surface of the skin, only when some special points are touched, can cause haptic. In a similar way you can find cold spots, hot spots and pain points. In the skin to stimulate the two points, to distinguish the two points when the minimum distance between the two stimuli, known as the two-point threshold or two-point discrimination threshold.