{"id":4877,"date":"2019-06-24T15:13:09","date_gmt":"2019-06-24T15:13:09","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/acchumanbio\/chapter\/12-4-dermis-3\/"},"modified":"2023-11-30T18:54:58","modified_gmt":"2023-11-30T18:54:58","slug":"12-4-dermis-3","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/acchumanbio\/chapter\/12-4-dermis-3\/","title":{"raw":"10.4\u00a0Dermis","rendered":"10.4\u00a0Dermis"},"content":{"raw":" \r\n
\r\n\r\n[caption id=\"attachment_3560\" align=\"aligncenter\" width=\"400\"]\"10.4.1\" Figure 10.4.1 Goose bumps!<\/em>[\/caption]\r\n

Goose Bumps<\/h1>\r\n<\/div>\r\nNo doubt you\u2019ve experienced the tiny, hair-raising skin bumps called goose bumps, like those you see in Figure 10.4.1. They happen when you feel chilly. Do you know what causes goose bumps, or why they pop up when you are cold? The answers to these questions involve the layer of skin known as the dermis.\r\n
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What is the Dermis?<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5967\"]dermis[\/pb_glossary]<\/strong>\u00a0is the inner of the two major layers that make up the skin, the outer layer being the\u00a0[pb_glossary id=\"5991\"]epidermis[\/pb_glossary]<\/strong>. The dermis consists mainly of [pb_glossary id=\"2815\"]connective tissues[\/pb_glossary]. It also contains most skin structures, such as [pb_glossary id=\"2936\"]glands[\/pb_glossary]\u00a0and\u00a0blood vessels. The dermis is anchored to the tissues below it by flexible collagen bundles that permit most areas of the skin to move freely over subcutaneous (\u201cbelow the skin\u201d) tissues. Functions of the dermis include cushioning subcutaneous tissues, regulating body\u00a0temperature, sensing\u00a0the environment, and excreting wastes.\r\n
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Anatomy of the Dermis<\/h1>\r\n<\/div>\r\nThe basic anatomy of the dermis is a matrix, or sort of scaffolding, composed of connective tissues. These tissues include collagen fibres \u2014 which provide toughness \u2014 and elastin fibres, which provide elasticity. Surrounding these fibres, the matrix also includes a gel-like substance made of proteins. The tissues of the matrix give the dermis both strength and flexibility.\r\n\r\nThe dermis is divided into two layers: the papillary layer and the reticular layer. Both layers are shown in Figure 10.4.2 below and described in the text that follows.\r\n\r\n[caption id=\"attachment_3561\" align=\"aligncenter\" width=\"376\"]\"Layers Figure 10.4.2 This photomicrograph shows a cross-section of the papillary and reticular layers of the dermis.<\/em>[\/caption]\r\n

Papillary Layer<\/h2>\r\nThe\u00a0[pb_glossary id=\"5843\"]papillary layer[\/pb_glossary]<\/strong> is the upper layer of the dermis, just below the [pb_glossary id=\"5907\"]basement membrane[\/pb_glossary] that connects the dermis to the epidermis above it. The papillary layer is the thinner of the two dermal layers. It is composed mainly of loosely arranged collagen fibres. The papillary layer is named for its fingerlike projections \u2014 or papillae \u2014 that extend upward into the epidermis. The papillae contain capillaries and sensory touch receptors.\r\n\r\n[caption id=\"attachment_3563\" align=\"alignleft\" width=\"390\"]\"10.3 Figure 10.4.3 This photo is an enlarged image of epidermal ridges on a finger.<\/em>[\/caption]\r\n\r\nThe papillae give the dermis a bumpy surface that interlocks with the epidermis above it, strengthening the connection between the two layers of skin. On the palms and soles, the papillae create epidermal ridges. Epidermal ridges on the fingers are commonly called fingerprints (see Figure 10.4.3). Fingerprints are genetically determined, so no two people (other than identical twins) have exactly the same fingerprint pattern. Therefore, fingerprints can be used as a means of identification, for example, at crime scenes. Fingerprints were much more commonly used forensically before DNA analysis was introduced for this purpose.\r\n

Reticular Layer<\/h2>\r\nThe\u00a0[pb_glossary id=\"5847\"]reticular layer<\/strong> [\/pb_glossary]is the lower layer of the dermis, located below the papillary layer. It is the thicker of the two dermal layers. It is composed of densely woven collagen and elastin fibres. These protein fibres give the dermis its properties of strength and elasticity. This layer of the dermis cushions subcutaneous tissues of the body from stress and strain. The reticular layer of the dermis also contains most of the structures in the dermis, such as [pb_glossary id=\"2936\"]glands[\/pb_glossary] and hair [pb_glossary id=\"6015\"]follicles<\/span>[\/pb_glossary]<\/span>.<\/span>\r\n
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Structures in the Dermis<\/h1>\r\n<\/div>\r\nBoth papillary and reticular layers of the dermis contain numerous [pb_glossary id=\"3006\"]sensory receptors[\/pb_glossary], which make the skin the body\u2019s primary sensory organ for the sense of [pb_glossary id=\"3129\"]touch[\/pb_glossary]. Both dermal layers also contain blood vessels. They provide nutrients to remove wastes from dermal cells, as well as cells in the lowest layer of the epidermis, the [pb_glossary id=\"3542\"]stratum basale[\/pb_glossary]. The circulatory components of the dermis are shown in Figure 10.4.4 below.\r\n\r\n[caption id=\"attachment_3565\" align=\"aligncenter\" width=\"1024\"]\"10.3 Figure 10.4.4 Both the papillary layer and the reticular layer of the dermis contain blood vessels, as shown in this diagram.<\/em>[\/caption]\r\n

Glands<\/h2>\r\nGlands in the reticular layer of the dermis include sweat glands and sebaceous (oil) glands. Both are exocrine glands, which are glands that release their secretions through ducts to nearby body surfaces. The diagram in Figure 10.4.5 shows these glands, as well as several other structures in the dermis.\r\n\r\n[caption id=\"attachment_3567\" align=\"aligncenter\" width=\"702\"]\"10.4 Figure 10.4.5 The dermis contains sweat and oil (sebaceous) glands, as well as hair follicles and blood vessels.<\/em>[\/caption]\r\n

Sweat Glands<\/h3>\r\n[pb_glossary id=\"3566\"]Sweat glands[\/pb_glossary]<\/strong>\u00a0produce the fluid called sweat, which contains mainly\u00a0water\u00a0and salts. The glands have ducts that carry the sweat to\u00a0hair\u00a0follicles, or to the surface of the skin. There are two different types of sweat glands: eccrine glands and apocrine glands.\r\n