The integument or skin is the largest organ in the body. It is composed of two layers and contains many different types of appendages, including hair, nails, and several kinds of glands. The layers of the skin include: (1) an outer layer of stratified squamous keratinized epithelium, the epidermis and (2) an inner layer of dense irregular connective tissue, the dermis. These two layers sit upon the subcutaneous tissue, which is composed of loose connective tissue, adipose tissue, and dense connective tissue (Skin). Skin is classified into two types based on the thickness of the epidermis and keratin layer. Thick skin is found on the palms of the hands and soles of the feet (Thick Skin). Thin skin covers the rest of the body (Thin Skin). Show Thick SkinThe epidermis of thick skin follows the contours of the dermal ridges, producing the epidermal ridges of the fingerprint. The dermal ridges penetrate into the epidermis as true papillae, and are separated by epithelial downgrowths called interpapillary pegs (Thick Skin 1). Five layers of cells or cell products are found in the epidermis: (1) stratum germinativum, columnar basal stem cells; (2) stratum spinosum, polyhedral cells with "spiny" projections: (3) stratum granulosum, diamond shaped cells containing keratohyalin granules; (4) stratum lucidum, a clear, homogenous line composed of eleidin, a keratohyalin transformation product (not always seen); and (5) stratum corneum, the keratin filled squames (Thick Skin 2). DermisThe dermis is composed of two layers: (1) the papillary dermis closest to the epithelium, is composed of less dense connective tissue and is vascularized with capillary networks penetrating the papillae and (2) the underlying reticular dermis composed of avascular, dense irregular connective tissue (Dermis). Subcutaneous LayerBeneath the dermis, a layer composed of adipose and loose/dense connective tissues make of the subcutaneous layer. Numerous structures are found in this layer. The secretory portion of the eccrine sweat glands are found here, with their ducts penetrating the dermis to enter the epidermis through the interpapillary pegs (Subcutaneum). Also, sensory structures (pacinian corpuscles), nerve bundles, blood vessels, and the bases of hair follicles are found in the subcutaneous layer. Thin SkinThe epidermis differs from that of thick skin in having thinner stratum spinosum, granulosum, and corneum, and lacks the stratum lucidum (Thin Skin 1). The dermis is not arranged in ridges, but does project into the epidermis as true papillae. However, no epidermal ridges are produced (Thin Skin 2). The pigment of the skin is produced by melanocytes, which take up residence in the basal layer (stratum germinativum) and produce melanin or pigment granules (Melanocytes). Hair FolliclesHair follicles are formed when the epidermis grows down into the dermis. The deepest portion of the hair follicle is composed only of stratum germinativum cells and is called the germinal matrix of the follicle. It sits upon a papillae of connective tissue. It is from this portion that the hair shaft is produced. The epidermal down-growth between the germinal matrix and the skin surface, forms a canal, the external root sheath (Hair 1). Several sebaceous glands are found associated with the hair follicle, usually along the upper one-third of the external root sheath. Also in this area are the arrector pili muscles (Hair 2). The sebaceous gland cells secrete via rupture, releasing oil. Thus the gland maintains a stem cell population and a gradient from immature to mature, oil filled cells is observed (Hair 3). The growth of the hair shaft from the germinal matrix begins by forming the layers of keratin producing cells called the internal root sheath (Hair 4). The hair shaft, composed of three keratinized layers travels within the external root sheath towards the surface of the skin (Hair 5). ReviewScope 1Scope 2Scope 3Scope 4Scope 5AnswersTemplate:Infobox Anatomy Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] The dermis is a layer of skin beneath the epidermis that consists of connective tissue, and cushions the body from stress and strain.The dermis is the lower layer of skin; contains main blood vessels. The dermis is tightly connected to the epidermis by a basement membrane, and harbors many nerve endings that provide the sense of touch and heat. It contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, and blood vessels. The blood vessels in the dermis provide nourishment and waste removal to its own cells, as well as the Stratum basale of the epidermis. StructureThe dermis is structurally divided into two areas: a superficial area adjacent to the epidermis, called the papillary region, and a deep thicker area known as the reticular region. Papillary regionThe papillary region is composed of loose areolar connective tissue. It is named for its fingerlike projections called papillae, which extend toward the epidermis. The papillae provide the dermis with a "bumpy" surface that interdigitates with the epidermis, strengthening the connection between the two layers of skin. In the palms, fingers, soles, and toes, the influence of the papillae projecting into the epidermis forms contours in the skin's surface. These are called friction ridges, because they help the hand or foot to grasp by increasing friction. Friction ridges occur in patterns (see fingerprint) that are genetically determined and are therefore unique to the individual, making it possible to use fingerprints or footprints as a means of identification. Reticular regionThe reticular region lies deep to the papillary region and is usually much thicker. It is composed of dense irregular connective tissue, and receives its name from the dense concentration of collagenous, elastic, and reticular fibers that weave throughout it. These protein fibers give the dermis its properties of strength, extensibility, and elasticity. Located within the reticular region are also the hair roots, sebaceous glands, sweat glands, receptors, nails, and blood vessels. Tattoo ink is injected into the dermis. Stretch marks are also located in the dermis. Additional images
External linksFind out How to get rid of stretch mark after pregnancy.
Template:Integumentary system Template:WH Template:WikiDoc Sources Which layer of the skin contains papillae?The dermal papillae are part of the uppermost layer of the dermis, the papillary dermis, and the ridges they form greatly increase the surface area between the dermis and epidermis.
What kind of connective tissue is found in the papillary layer of the dermis?The papillary layer is made of loose, areolar connective tissue, which means the collagen and elastin fibers of this layer form a loose mesh.
What layer of the skin has come like projections?The squamous cell layer is located above the basal layer, and is also known as the stratum spinosum or "spiny layer" due to the fact that the cells are held together with spiny projections.
What's in the papillary layer?The papillary layer is defined by rete ridges (i.e. papillae) which are finger-like structures extending into the epidermis and contains thin collagen fibres, sensory nerve endings, cytoplasms and a rich network of blood capillaries.
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