MODULE 1 Touch (Skin) The sense of touch in humans is the skin. For example, in the form of mechanoreceptors, nociceptors and thermoreceptors. Therefore, the skin is very sensitive to touch, heat, cold, pressure and pain (pain). If the skin is stimulated, various different stimuli can occur. The different types of stimulation that arise are determined by special receptors (senses) found on nerve endings. In general, there are two types of nerve endings in skin receptors, namely free nerve ending receptors and receptors with capsule/membrane-covered nerve endings. Free nerve ending receptors are found in all body tissues and function to detect pain. Receptors with sheathed or webbed nerve endings can beCorpuscle MeissnerAndMerkel Discuss, functions to detect soft touch stimuli,Pacini's Corpuscle detect pressure stimulation,Corpuscle Ruffinidetect heat stimulation AndCorpuscle Krausedetect stimulation cold. All specialized receptors are not evenly distributed on the skin. Certain skin areas can be much more sensitive than other skin areas to a stimulus. For example, fingertips and lips are very sensitive to touch, much more so than the back of the hand. 1. Skin Anatomy The skin is the barrier between the body and the surrounding environment because it is located on the outermost part. The area of adult skin is 1.5 m2 with a weight of approximately 15% of body weight. Classification based on: 1) Color: a) light (fair skin), blonde, and black; b) pink: on the soles of the baby's feet and hands; c) black-brown: on adult genitalia. 2) Type: a) Elastic and loose: on the eyelids, lips and prepuce. b) Thick and tense: on the soles of the feet and hands of adults. c) Thin: on the face. d) Gentle: on the neck and body. e) Coarse hair: on the head. 2. Histopathological skin anatomy a. Epidermis layer (cuticle) 1) Stratum Corneum (horny layer) => the outermost layer of skin consisting of dead flat cells, without nuclei, whose protoplasm turns into keratin (horny substance) 2) Stratum Lusidum => located under the corneum layer, a layer of flattened cells without nuclei, whose protoplasm turns into a protein called eleidin. This layer is more clearly visible on the palms of the hands and feet. 3) Stratum Granulosum (keratohyalin layer) => is 2 or 3 layers of flattened cells with coarse-grained cytoplasm and a nucleus between them. The coarse grains consist of keratohyalin. The mucosa usually does not have this layer. 4) Stratum Spinosum (Malpighian stratum) or prickle cell layer (acanta layer) => consists of polygonal shaped cells, the protoplasm is clear because it contains a lot of glycogen, the cells will become flatter the closer they are to the surface. Between the stratum spinosum, there are intercellular bridges consisting of protoplasm and tonofibrils or keratin. The adhesions between these bridges form small rounded thickenings called Bizzozero nodules. Among the spinosum cells there are also Langerhans cells. . 5) Stratum Basalis => consists of cubic (columnar) cells arranged vertically at the dermo-epidermal border in a row like a fence (palisade). Basal cells undergo mitosis and function reproductively. a) Columnar cells => basophilic protoplasm, large oval nuclei, connected by bridges between cells. b) Melanin-forming cells (melanocytes) or clear cells => light colored cells, basophilic cytoplasm and dark nuclei, containing pigment (melanosomes). b. Dermis Layer(corium, cutis vera,true skin) => consists of elastic and fibrous layers along with cellular elements and hair follicles. 1) Pars papilare => the part that protrudes into the epidermis, contains the endings of nerve fibers and blood vessels. 2) Pars Reticulare => lower part that protrudes subcutaneously. Consists of supporting fibers such as collagen, elastin, and reticulin. The base (matrix) of this layer consists of a thick liquid of hyaluronic acid and chondroitin sulfate, in this section there are also fibroblasts. Collagen fibers are formed by fibroblasts, which then form bundles containing hydroxyproline and hydroxycillin. Young collagen is elastin, with age, it becomes less soluble and more stable. Reticulin is like young collagen. Elastin fibers are usually wavy, amorphous, expand easily and are more elastic. c. Subcutis Layer (hypodermis)=>the innermost layer, consisting of loose connective tissue containing round, large fat cells, with nuclei pushed to the edge of the increased fat cytoplasm. These cells are grouped and separated by fibrous trabeculae. The layer of fat cells, called the adipose paniculus, functions as a food reserve. In this layer there are peripheral nerves, blood vessels and lymph. The fat layer also functions as a cushion, the thickness is different in some skins. On the eyelids and penis it is thinner, on the stomach it is thicker (up to 3 cm).