{"id":1813,"date":"2014-10-23T21:54:29","date_gmt":"2014-10-23T21:54:29","guid":{"rendered":"https:\/\/courses.candelalearning.com\/apvccs\/?post_type=chapter&#038;p=1813"},"modified":"2017-09-26T20:14:20","modified_gmt":"2017-09-26T20:14:20","slug":"1813","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-ap1\/chapter\/1813\/","title":{"raw":"Slides of the Integumentary System","rendered":"Slides of the Integumentary System"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Objectives<\/h3>\r\n<ul>\r\n \t<li>Be able to identify principal layers of the skin (epidermis, dermis and hypodermis) at the light microscope level and know the principal functions of each\u00a0layer.<\/li>\r\n \t<li>Be able to identify the layers of the epidermis in thick and thin skin and describe the major cellular events that take place in each layer in the process of\u00a0keratinization.<\/li>\r\n \t<li>Identify melanocytes and explain the process of pigment formation in the\u00a0skin.<\/li>\r\n \t<li>Be able to identify eccrine and apocrine sweat glands at the light microscope\u00a0level.<\/li>\r\n \t<li>Identify the components of the pilosebaceous apparatus and know the structural and developmental relationship between each component and the epidermis of the\u00a0skin.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<a href=\"http:\/\/histology.medicine.umich.edu\/resources\/integumentary-system\" target=\"_blank\" rel=\"noopener\">This material may also be accessed here.<\/a>\r\n<h2>Integumentary Structures<\/h2>\r\nThe skin and its associated structures, hair, sweat glands and nails make up the integumentary\u00a0system.\r\n<h3>Thick\u00a0skin<\/h3>\r\n<ul>\r\n \t<li><strong>106\u00a0<\/strong><em>thick skin, sole of foot H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Basic%20Tissues\/Epithelium%20and%20CT\/106_HISTO_40X.svs\/view.apml\">Webscope<\/a><\/li>\r\n \t<li><strong>112\u00a0<\/strong><em>thick skin, sole of foot H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112_HISTO_40X.svs\/view.apml\">Webscope<\/a><\/li>\r\n \t<li><strong>112N\u00a0<\/strong><em>thick skin, sole of foot H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112N_HISTO_40X.svs\/view.apml\">Webscope<\/a><\/li>\r\n<\/ul>\r\nIn this slide the structure of skin, especially the epidermis, is exaggerated in response to the continued stress and abrasion applied to the plantar surface of the foot.\u00a0 Study the\u00a0<span style=\"text-decoration: underline;\">epidermis<\/span>\u00a0in\u00a0<strong>slides #106<\/strong>,\u00a0<strong>#112<\/strong>, and\u00a0<strong>#112N<\/strong>.\u00a0 Identify the various\u00a0strata:\r\n<ol>\r\n \t<li><span style=\"text-decoration: underline;\">Stratum basale<\/span>\u00a0(also known as S. germinativum):\u00a0 A single layer of cuboidal to columnar cells resting on and separated from the underlying dermis by a basal lamina.\u00a0 Mitotic figures occur in this\u00a0layer.<\/li>\r\n \t<li><span style=\"text-decoration: underline;\">Stratum<\/span>\u00a0<span style=\"text-decoration: underline;\">spinosum<\/span>:\u00a0 Several layers in thickness.\u00a0 In reduced light, the cells appear interconnected by \u201cspinous\u201d\u00a0processes.<\/li>\r\n \t<li><span style=\"text-decoration: underline;\">Stratum granulosum<\/span>:\u00a0 A few layers of cells that are characterized by numerous, dense, basophilic granules.\u00a0\u00a0 These are keratohyaline and membrane coating\u00a0granules.<\/li>\r\n \t<li><span style=\"text-decoration: underline;\">Stratum<\/span>\u00a0<span style=\"text-decoration: underline;\">corneum<\/span>: Note the striking change in cellular morphology.\u00a0 The cells are flattened, devoid of nuclei or cytoplasmic granules, and filled with mature keratin (<strong>#112N<\/strong>).\u00a0\u00a0 In \u00a0<strong>#106\u00a0<\/strong>or\u00a0<strong>#112<\/strong>, however, nuclei are still present in many cells of this layer, which are not normal.\u00a0\u00a0 Because of differential dye penetration, the staining of the stratum corneum is variable and unpredictable.\u00a0 Sectioning artifacts are\u00a0common.<\/li>\r\n<\/ol>\r\nThe principal cell type of the epidermis is termed a\u00a0<span style=\"text-decoration: underline;\">keratinocyte<\/span>\u00a0and you will see this term used as a general descriptor for the epithelial cell found in any stratified squamous epithelium.\u00a0 Note the absence of blood vessels in the epidermis.\u00a0 Nourishment is obtained by diffusion from capillaries in the underlying\u00a0dermis.\r\n\r\nThe interface of the epidermis and dermis is uneven.\u00a0 A pattern of ridges and grooves on the deep surface of the epidermis fit a complementary pattern of corrugations of the underlying dermis.\u00a0 The projections of the dermis are called dermal papillae and those of the epidermis, epidermal ridges (pegs), because of their appearance in vertical sections of the skin.\u00a0 However, these terms are not always accurately descriptive of the three dimensional configuration of the region of interdigitation.\u00a0 With low power, identify the epidermal ridges and dermal papillae.\u00a0<strong>What is the function of the epidermal ridges and dermal papillae?<\/strong>\u00a0Answer: Epidermal ridges and dermal papillae provide increased surface area for the epidermis and dermis to connect.\u00a0Note the finer arrangement of collagen fibers in the papillary dermis\u00a0<strong>#112N\u00a0papillary dermis<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112N_HISTO_40X.svs\/view.apml?x=0.1614517462&amp;y=0.4188532377&amp;zoom=35.9732889274&amp;transform=\">Webscope\u00a0<\/a>\u00a0as opposed to that of the reticular dermis\u00a0<strong>#112N\u00a0reticular dermis<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112N_HISTO_40X.svs\/view.apml?x=0.1633952298&amp;y=0.3792541712&amp;zoom=35.9732889274&amp;transform=\">Webscope\u00a0<\/a>\u00a0(refer back to<strong>#033\u00a0morphology and distribution of elastic fibers\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Basic%20Tissues\/Epithelium%20and%20CT\/033_HISTO_20X.svs\/view.apml?x=-0.1142549752&amp;y=-0.3797563078&amp;zoom=50.0000000000&amp;transform=\">Webscope\u00a0<\/a>\u00a0in order to review the morphology and distribution of elastic fibers in the dermis).\u00a0 The fatty layer beneath the dermis, the\u00a0<span style=\"text-decoration: underline;\">subcutaneous<\/span>\u00a0<span style=\"text-decoration: underline;\">connective<\/span>\u00a0<span style=\"text-decoration: underline;\">tissue<\/span>, is often called the\u00a0<span style=\"text-decoration: underline;\">hypodermis<\/span>\u00a0or\u00a0<span style=\"text-decoration: underline;\">superficial<\/span>\u00a0<span style=\"text-decoration: underline;\">fascia<\/span>.\u00a0 It is this layer that allows the skin to\u00a0\u201cmove\u201d.\r\n<h3>Thin\u00a0Skin<\/h3>\r\n<ul>\r\n \t<li><strong>105-1\u00a0<\/strong><em>hair follicle H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/105-1_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\r\n \t<li><strong>105-2\u00a0<\/strong><em>thin skin H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/105-2_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\r\n \t<li><strong>104-1\u00a0<\/strong><em>thin skin H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/104-1_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\r\n \t<li><strong>104-2\u00a0<\/strong><em>thin skin H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/104-2_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\r\n<\/ul>\r\nThe epidermis in thin skin is much thinner and simpler in structure.\u00a0 Each stratum is thinner and the stratum granulosum may be absent.Melanocytes\u00a0<strong>#105-1\u00a0melanocytes<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/105-1_HISTO_40X.svs\/view.apml?x=0.2034644159&amp;y=0.0192744042&amp;zoom=100.0000000000&amp;transform=\">Webscope\u00a0<\/a>(derived from neural crest cells) capable of producing the pigment melanin are numerous in the deeper (toward the base) layers of the epidermis. They can be identified by the presence of a nucleus surrounded by a clear space.\u00a0 The cells with brownish pigments are actually keratinocytes that have received melanin granules from the melanocytes by pigment donation. The\u00a0<strong>slides<\/strong>\u00a0<strong>104-1<\/strong>and\u00a0<strong>104-2\u00a0<\/strong>are skin samples from light and darker skinned individuals.\u00a0 It is not difficult to tell which sample is from which individual.\u00a0 Note the presence of portions of hair follicles and sebaceous glands in the\u00a0dermis.\r\n<h2>Peripheral Mechanosensory Receptors<\/h2>\r\n<h3>Meissner\u2019s\u00a0Corpuscles<\/h3>\r\n<ul>\r\n \t<li><strong>UCSF 180\u00a0<\/strong><em>finger tip H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/UCSF%20Histology\/UCSF180_40X.svs\/view.apml\">Webscope<\/a>\u00a0(virtual slide courtesy of the University of California, San Francisco)<\/li>\r\n \t<li><strong>112\u00a0<\/strong><em>thick skin, sole of foot H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a>(note, there\u2019s only one corpuscle apparent in this\u00a0slide)<\/li>\r\n<\/ul>\r\nMeissner\u2019s corpuscles\u00a0<strong>#UCSF 180\u00a0meissner\u2019s corpuscles<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/UCSF%20Histology\/UCSF180_40X.svs\/view.apml?x=0.0656270071&amp;y=0.1073216394&amp;zoom=50.0000000000&amp;transform=\">Webscope\u00a0<\/a>are touch receptors that are responsive to low-frequency stimuli and are usually associated with hairless skin of the lips and palmar and plantar surfaces, particularly those of the fingers and toes. Generally, these receptors are tapered cylinders located in the undulating connective tissue just underneath the stratified epithelium of the skin. The long axis of the cylinder is perpendicular to that of the overlying epidermis and is usually about 150 um long and is usually tucked within extensions of the underlying connective tissue dermis (called \u201cdermal papillae\u201d) that project into the underside of the epidermis. Within these receptors, one or two nonmyelinated endings of myelinated nerve fibers follow a spiral path through the corpuscle. The fibers are accompanied by ensheathing Schwann cells, the nuclei of which are flattened and stacked on top of each other giving the corpuscle its characteristic irregular, lamellar\u00a0appearance.\r\n<h3>Pacinian\u00a0Corpuscles<\/h3>\r\n<ul>\r\n \t<li><strong>108\u00a0<\/strong><em>fetal fingar Masson<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/108_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\r\n \t<li><strong>042\u00a0<\/strong><em>mesentery H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Cardiovascular%20System\/042_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\r\n \t<li><strong>095\u00a0<\/strong><em>Small arteries and vein H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Cardiovascular%20System\/095_HISTO_20X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\r\n \t<li><strong>095M\u00a0<\/strong><em>mesentary Masson<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Cardiovascular%20System\/095M_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\r\n<\/ul>\r\nPacinian corpuscles\u00a0<strong>#095M\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Cardiovascular%20System\/095M_HISTO_40X.svs\/view.apml?x=0.1908347401&amp;y=0.1904834073&amp;zoom=25.0000000000&amp;transform=\">Webscope\u00a0<\/a>(best seen in slide 108) are large, ovoid structures up to 1 mm in diameter found in the dermis and hypodermis of the skin and also in the connective tissue associated with bones, joints, and internal organs. They respond primarily to pressure and vibration and are composed of a myelinated nerve ending surrounded by a capsule. The nerve enters the capsule at one pole (which might be out of the plane of section and therefore not visible) with its myelin sheath intact but then it is quickly lost. The unmyelinated portion of the axon extends toward the opposite pole from which it entered and its length is covered by flattened Schwann cell lamellae that form the inner core of the corpuscle. The remaining bulk of the capsule, or outer core, is comprised of a series of concentric, onionlike lamellae with each layer separated by an extracellular fluid similar to lymph. Each lamella is composed of flattened Schwann cells and endoneurial fibroblasts. In addition the fluid between each layer, delicate collagen fibers may be present as well as occasional capillaries. Displacement of the lamellae by pressure or vibrations effectively causes depolarization of the axon, which sends the signal to the central nervous\u00a0system.\r\n<h2>Scalp and Hair<\/h2>\r\n<ul>\r\n \t<li><strong>107\u00a0<\/strong><em>Scalp hair H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/107_HISTO_40X.svs\/view.apml\">Webscope<\/a><\/li>\r\n<\/ul>\r\nUnderneath the thin epidermis, there are numerous circular to oblong structures with a hollow or yellow-brown center and surrounding cellular layers.\u00a0 These structures are hair follicles\u00a0<strong>#107\u00a0<\/strong>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/107_HISTO_40X.svs\/view.apml?x=0.1797414425&amp;y=0.1386101965&amp;zoom=6.4905471519&amp;transform=\">Webscope\u00a0<\/a>sectioned transversely or tangentially at different levels.\u00a0 The keratinized component of the hair occupies the central cavity of the follicle, and appears yellow-brown when present. However, the hair often falls out during tissue processing, in which case the central cavity will appear to be occupied by just empty space.\u00a0 The surrounding layers of clear cells form the external root sheath of the hair, which is a downgrowth of the epidermis. In fact, in cases where most of the epidermis is removed (such as severe abrasions or when taking skin graft), it is cells of the external root sheath that will divide and spread over the exposed surface to re-establish the epidermis. \u00a0 In some sections, you may also see an internal root sheath of darker staining cells right up against the hair follicle \u2013this is the layer of cells that actually produce the keratinized hair shaft. Note also the presence of sebaceous glands\u00a0<strong>#107\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/107_HISTO_40X.svs\/view.apml?x=0.1706576987&amp;y=0.2326887715&amp;zoom=36.0000000000&amp;transform=\">Webscope\u00a0<\/a>and the arrector pili muscle\u00a0<strong>#107\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/107_HISTO_40X.svs\/view.apml?x=0.1464568167&amp;y=0.2801145390&amp;zoom=100.0000000000&amp;transform=\">Webscope\u00a0<\/a>near the hair follicle.\u00a0 In most instances, you will not find complete pilosebaceous units in a single section, so a bit of mental reconstruction will be\u00a0required.\r\n<h2>Sweat Glands<\/h2>\r\n<h3>Eccrine Sweat Gland<\/h3>\r\n<ul>\r\n \t<li><strong>106\u00a0<\/strong><em>Thick skin, sole of foot (Homo)\u00a0<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Basic%20Tissues\/Epithelium%20and%20CT\/106_HISTO_40X.svs\/view.apml?x=-0.2241109127&amp;y=-0.1057661521&amp;zoom=19.3806699468&amp;transform=\">Webscope<\/a><\/li>\r\n \t<li><strong>112\u00a0<\/strong>\u00a0<em>Thick skin (Homo)\u00a0<\/em><a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112_HISTO_40X.svs\/view.apml?x=-0.1451530172&amp;y=-0.1029983767&amp;zoom=19.3806699468&amp;transform=\">Webscope<\/a><\/li>\r\n \t<li><strong>112N\u00a0<\/strong><em>Thick skin (Homo)<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112N_HISTO_40X.svs\/view.apml?x=-0.1292488527&amp;y=0.2329551176&amp;zoom=10.0371983993&amp;transform=\">Webscope<\/a><\/li>\r\n \t<li><strong>105-1\u00a0<\/strong><em>Thin skin (Homo)<\/em>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/105-1_HISTO_40X.svs\/view.apml?x=0.4583594194&amp;y=-0.3319463629&amp;zoom=30.0000000000&amp;transform=\">Webscope<\/a><\/li>\r\n<\/ul>\r\nNumerous coiled\u00a0<span style=\"text-decoration: underline;\">eccrine<\/span>\u00a0<span style=\"text-decoration: underline;\">sweat<\/span>\u00a0<span style=\"text-decoration: underline;\">glands<\/span>\u00a0are located at the junction of dermis and hypodermis.\u00a0 The coiled morphology can be particularly appreciated in the example shown in\u00a0<strong>slide 112N<\/strong>. Distinguish between the\u00a0<span style=\"text-decoration: underline;\">secretory portions<\/span>\u00a0of the gland (secretory cells and myoepithelial cells; the latter are best seen in the apocrine gland, see below,\u00a0<strong>slide 111<\/strong>\u00a0and\u00a0<strong>104-2<\/strong>) and the stratified (two layers) cuboidal epithelial cell-lined\u00a0<span style=\"text-decoration: underline;\">duct<\/span>.\u00a0\u00a0<strong>Where do the ducts empty?<\/strong>?\u00a0Answer: Ducts of eccrine sweat glands empty onto the surface of the skin. Apocrine glands, however, empty into hair follicles in the axillary, areolar and perianal regions.\u00a0<strong>How does sweat get to the surface?<\/strong>\u00a0Answer: Eccrine sweat glands have ducts that lead to the surface of the skin. Eccrine sweat glands are a type of merocrine gland (a gland that releases its product by exocytosis). The secretory cells of the eccrine gland are surrounded by myoepithelial cells which can contract to propel its secretions to the surface. Apocrine sweat glands (apocrine being a misnomer, they are truly a merocrine gland, not an apocrine gland) function in the same way, however, their ducts lead to hair follicles, not directly to the skin\u00a0surface.\r\n<h3>Apocrine Glands<\/h3>\r\n<ul>\r\n \t<li><strong>109-1\u00a0<\/strong><em>Perianal region Masson<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/109-1_HISTO_20X.svs\/view.apml\">Webscope<\/a><\/li>\r\n \t<li><strong>109-2\u00a0<\/strong><em>Perianal region PAS\/Pb hematoxylin<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/109-2_HISTO_20X.svs\/view.apml\">Webscope<\/a><\/li>\r\n \t<li><strong>111\u00a0<\/strong><em>axilla, subcutaneal region Masson<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/111_HISTO_40X.svs\/view.apml\">Webscope<\/a><\/li>\r\n \t<li><strong>104-2\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/104-2_HISTO_40X.svs\/view.apml?x=0.3670398775&amp;y=0.1096661997&amp;zoom=14.2317090684&amp;transform=\">Webscope\u00a0<\/a>(this slide has both eccrine AND apocrine sweat glands; see if you can identify\u00a0them)<\/li>\r\n<\/ul>\r\nLook in the deep dermis or hypodermis for secretory tubules with a wide lumen.\u00a0 The epithelium is cuboidal to columnar with distinct apical secretory granules.\u00a0 What should be apparent in your section is the apical \u201cblebbing\u201d of the secretory cells that was responsible for histologists originally designating these cells as \u201c<span style=\"text-decoration: underline;\">apocrine<\/span>\u201d secretory cells, although we now know the cells actually secrete in a MEROCRINE manner just like eccrine sweat glands.\u00a0 The \u201capocrine\u201d sweat glands, present in the axillary, areolar, and anal regions, represent the second type of sweat glands.\u00a0 These glands produce a viscous secretion which acquires a distinctive odor as a result of bacterial\u00a0decomposition.\r\n\r\nIn complete transverse sections of the glands (e.g.\u00a0<strong>slide #111<\/strong>), look for oblong nuclei just inside the basement membrane.\u00a0 These are the nuclei of\u00a0<span style=\"text-decoration: underline;\">myoepithelial cells<\/span>.\u00a0 In some planes of section, the nuclei may appear round.\u00a0 Now look for a tangential section of the gland.\u00a0 Look for regularly spaced, elongate strands of cytoplasm\u00a0 investing the outside of the secretory epithelium.\u00a0 With a bit more looking you should be able to see that these elongate bits of cytoplasm contain the above mentioned oblong nuclei.\u00a0\u00a0<strong>Slide 104-2\u00a0<\/strong>is another good place to see myoepithelial cells\u00a0<strong>#104-2\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/104-2_HISTO_40X.svs\/view.apml?x=0.3670398775&amp;y=0.1096661997&amp;zoom=14.2317090684&amp;transform=\">Webscope\u00a0<\/a>; look for eosinophilic strands of cytoplasm and small nuclei just peripheral to the secretory epithelial cells. In PAS stained slides (e.g.\u00a0<strong>#109-2<\/strong>), densely staining granules are obvious in the apical cytoplasm the secretory cells, but the cytoplasm of myoepithelial cells is not well seen.\u00a0 Instead you see darker pink-stained basement membrane between the projections of myoepithelial cells.\u00a0 The relatively great number of these cells in sweat glands (and mammary glands) can only be appreciated by studying such tangential\u00a0cuts.\r\n\r\nPlease also look for apocrine sweat gland ducts in these slides. They look similar to eccrine gland ducts described above (small diameter and small lumen with a stratified cuboidal epithelium). Similarly, they also lack lack myoepithelial cells. Make sure you can discriminate the ductal portion of apocrine sweat grlands from their secretory\u00a0portion.\r\n<h2>Electron\u00a0Micrographs<\/h2>\r\n<ul>\r\n \t<li><strong>65 Epidermis\u00a0<i>Skin\u00a0<\/i><\/strong><a href=\"http:\/\/virtualslides.med.umich.edu\/Histology\/EMsmallCharts\/3%20Image%20Scope%20finals\/065%20-%20Epidermis_001.svs\/view.apml\">Webscope<\/a><\/li>\r\n<\/ul>\r\nReview the layering of the epidermis. Remember that there is a continuous process of cell migration and differentiation from the basal cell layer to the most superficial layer. Review the features of the epidermal-dermal junction.\r\n<ul>\r\n \t<li><strong>67 Epidermis - Details of the Stratum Spinosum\u00a0<i><\/i><\/strong><a href=\"http:\/\/virtualslides.med.umich.edu\/Histology\/EMsmallCharts\/3%20Image%20Scope%20finals\/067%20-%20Epidermis_001.svs\/view.apml\">Webscope<\/a><\/li>\r\n<\/ul>\r\nObserve the abundance of tonofibrils (= keratin intermediate filaments) and ribosomes and the small number of mitochondria. Note the absence of Golgi apparatus and granular endoplasmic reticulum. Epidermal cells do contain these organelles but in reduced amount, as the bulk of synthesis is for structural proteins, not exportable ones. What is the function of the numerous desmosomes? The function of the tonofibrils? (IN4)\r\n<ul>\r\n \t<li><strong>69 Epidermis \u2013 Details of the Stratum Granulosum and Stratum Corneum\u00a0<i><\/i><\/strong><a href=\"http:\/\/virtualslides.med.umich.edu\/Histology\/EMsmallCharts\/3%20Image%20Scope%20finals\/069%20-%20Epidermis_001.svs\/view.apml\">Webscope<\/a><\/li>\r\n<\/ul>\r\nNote the keratohyaline granules in the cells of the stratum granulosum. The keratinization process is completed in the cell layers above the stratum granulosum, indicated by the disappearance of nuclei and cell organelles. Note that the cornified cells are of variable appearance (some \"dark\" and some \"light\") a reflection of the tissue processing rather than of a functional difference.\r\n<div class=\"textbox exercises\">\r\n<h3>Review Questions<\/h3>\r\n<ol>\r\n \t<li>What is the function of the numerous myoepithelial cells (in sweat\u00a0glands)?[reveal-answer q=\"594330\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"594330\"]Myoepithelial cells are what propel the secretory contents of the glands to the surface of the\u00a0body.\r\n[\/hidden-answer]<\/li>\r\n \t<li>What is the function of the epidermal ridges and dermal\u00a0papillae?[reveal-answer q=\"510934\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"510934\"]Epidermal ridges and dermal papillae provide increased surface area for the epidermis and dermis to\u00a0connect.\r\n[\/hidden-answer]<\/li>\r\n \t<li>Where do the ducts\u00a0empty?[reveal-answer q=\"50922\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"50922\"]Ducts of eccrine sweat glands empty onto the surface of the skin. Apocrine glands, however, empty into hair follicles in the axillary, areolar and perianal\u00a0regions.\r\n[\/hidden-answer]<\/li>\r\n \t<li>How does sweat get to the\u00a0surface?[reveal-answer q=\"454049\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"454049\"]Eccrine sweat glands have ducts that lead to the surface of the skin. Eccrine sweat glands are a type of merocrine gland (a gland that releases its product by exocytosis). The secretory cells of the eccrine gland are surrounded by myoepithelial cells which can contract to propel its secretions to the surface. Apocrine sweat glands (apocrine being a misnomer, they are truly a merocrine gland, not an apocrine gland) function in the same way, however, their ducts lead to hair follicles, not directly to the skin\u00a0surface.[\/hidden-answer]<\/li>\r\n<\/ol>\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Objectives<\/h3>\n<ul>\n<li>Be able to identify principal layers of the skin (epidermis, dermis and hypodermis) at the light microscope level and know the principal functions of each\u00a0layer.<\/li>\n<li>Be able to identify the layers of the epidermis in thick and thin skin and describe the major cellular events that take place in each layer in the process of\u00a0keratinization.<\/li>\n<li>Identify melanocytes and explain the process of pigment formation in the\u00a0skin.<\/li>\n<li>Be able to identify eccrine and apocrine sweat glands at the light microscope\u00a0level.<\/li>\n<li>Identify the components of the pilosebaceous apparatus and know the structural and developmental relationship between each component and the epidermis of the\u00a0skin.<\/li>\n<\/ul>\n<\/div>\n<p><a href=\"http:\/\/histology.medicine.umich.edu\/resources\/integumentary-system\" target=\"_blank\" rel=\"noopener\">This material may also be accessed here.<\/a><\/p>\n<h2>Integumentary Structures<\/h2>\n<p>The skin and its associated structures, hair, sweat glands and nails make up the integumentary\u00a0system.<\/p>\n<h3>Thick\u00a0skin<\/h3>\n<ul>\n<li><strong>106\u00a0<\/strong><em>thick skin, sole of foot H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Basic%20Tissues\/Epithelium%20and%20CT\/106_HISTO_40X.svs\/view.apml\">Webscope<\/a><\/li>\n<li><strong>112\u00a0<\/strong><em>thick skin, sole of foot H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112_HISTO_40X.svs\/view.apml\">Webscope<\/a><\/li>\n<li><strong>112N\u00a0<\/strong><em>thick skin, sole of foot H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112N_HISTO_40X.svs\/view.apml\">Webscope<\/a><\/li>\n<\/ul>\n<p>In this slide the structure of skin, especially the epidermis, is exaggerated in response to the continued stress and abrasion applied to the plantar surface of the foot.\u00a0 Study the\u00a0<span style=\"text-decoration: underline;\">epidermis<\/span>\u00a0in\u00a0<strong>slides #106<\/strong>,\u00a0<strong>#112<\/strong>, and\u00a0<strong>#112N<\/strong>.\u00a0 Identify the various\u00a0strata:<\/p>\n<ol>\n<li><span style=\"text-decoration: underline;\">Stratum basale<\/span>\u00a0(also known as S. germinativum):\u00a0 A single layer of cuboidal to columnar cells resting on and separated from the underlying dermis by a basal lamina.\u00a0 Mitotic figures occur in this\u00a0layer.<\/li>\n<li><span style=\"text-decoration: underline;\">Stratum<\/span>\u00a0<span style=\"text-decoration: underline;\">spinosum<\/span>:\u00a0 Several layers in thickness.\u00a0 In reduced light, the cells appear interconnected by \u201cspinous\u201d\u00a0processes.<\/li>\n<li><span style=\"text-decoration: underline;\">Stratum granulosum<\/span>:\u00a0 A few layers of cells that are characterized by numerous, dense, basophilic granules.\u00a0\u00a0 These are keratohyaline and membrane coating\u00a0granules.<\/li>\n<li><span style=\"text-decoration: underline;\">Stratum<\/span>\u00a0<span style=\"text-decoration: underline;\">corneum<\/span>: Note the striking change in cellular morphology.\u00a0 The cells are flattened, devoid of nuclei or cytoplasmic granules, and filled with mature keratin (<strong>#112N<\/strong>).\u00a0\u00a0 In \u00a0<strong>#106\u00a0<\/strong>or\u00a0<strong>#112<\/strong>, however, nuclei are still present in many cells of this layer, which are not normal.\u00a0\u00a0 Because of differential dye penetration, the staining of the stratum corneum is variable and unpredictable.\u00a0 Sectioning artifacts are\u00a0common.<\/li>\n<\/ol>\n<p>The principal cell type of the epidermis is termed a\u00a0<span style=\"text-decoration: underline;\">keratinocyte<\/span>\u00a0and you will see this term used as a general descriptor for the epithelial cell found in any stratified squamous epithelium.\u00a0 Note the absence of blood vessels in the epidermis.\u00a0 Nourishment is obtained by diffusion from capillaries in the underlying\u00a0dermis.<\/p>\n<p>The interface of the epidermis and dermis is uneven.\u00a0 A pattern of ridges and grooves on the deep surface of the epidermis fit a complementary pattern of corrugations of the underlying dermis.\u00a0 The projections of the dermis are called dermal papillae and those of the epidermis, epidermal ridges (pegs), because of their appearance in vertical sections of the skin.\u00a0 However, these terms are not always accurately descriptive of the three dimensional configuration of the region of interdigitation.\u00a0 With low power, identify the epidermal ridges and dermal papillae.\u00a0<strong>What is the function of the epidermal ridges and dermal papillae?<\/strong>\u00a0Answer: Epidermal ridges and dermal papillae provide increased surface area for the epidermis and dermis to connect.\u00a0Note the finer arrangement of collagen fibers in the papillary dermis\u00a0<strong>#112N\u00a0papillary dermis<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112N_HISTO_40X.svs\/view.apml?x=0.1614517462&amp;y=0.4188532377&amp;zoom=35.9732889274&amp;transform=\">Webscope\u00a0<\/a>\u00a0as opposed to that of the reticular dermis\u00a0<strong>#112N\u00a0reticular dermis<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112N_HISTO_40X.svs\/view.apml?x=0.1633952298&amp;y=0.3792541712&amp;zoom=35.9732889274&amp;transform=\">Webscope\u00a0<\/a>\u00a0(refer back to<strong>#033\u00a0morphology and distribution of elastic fibers\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Basic%20Tissues\/Epithelium%20and%20CT\/033_HISTO_20X.svs\/view.apml?x=-0.1142549752&amp;y=-0.3797563078&amp;zoom=50.0000000000&amp;transform=\">Webscope\u00a0<\/a>\u00a0in order to review the morphology and distribution of elastic fibers in the dermis).\u00a0 The fatty layer beneath the dermis, the\u00a0<span style=\"text-decoration: underline;\">subcutaneous<\/span>\u00a0<span style=\"text-decoration: underline;\">connective<\/span>\u00a0<span style=\"text-decoration: underline;\">tissue<\/span>, is often called the\u00a0<span style=\"text-decoration: underline;\">hypodermis<\/span>\u00a0or\u00a0<span style=\"text-decoration: underline;\">superficial<\/span>\u00a0<span style=\"text-decoration: underline;\">fascia<\/span>.\u00a0 It is this layer that allows the skin to\u00a0\u201cmove\u201d.<\/p>\n<h3>Thin\u00a0Skin<\/h3>\n<ul>\n<li><strong>105-1\u00a0<\/strong><em>hair follicle H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/105-1_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\n<li><strong>105-2\u00a0<\/strong><em>thin skin H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/105-2_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\n<li><strong>104-1\u00a0<\/strong><em>thin skin H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/104-1_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\n<li><strong>104-2\u00a0<\/strong><em>thin skin H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/104-2_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\n<\/ul>\n<p>The epidermis in thin skin is much thinner and simpler in structure.\u00a0 Each stratum is thinner and the stratum granulosum may be absent.Melanocytes\u00a0<strong>#105-1\u00a0melanocytes<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/105-1_HISTO_40X.svs\/view.apml?x=0.2034644159&amp;y=0.0192744042&amp;zoom=100.0000000000&amp;transform=\">Webscope\u00a0<\/a>(derived from neural crest cells) capable of producing the pigment melanin are numerous in the deeper (toward the base) layers of the epidermis. They can be identified by the presence of a nucleus surrounded by a clear space.\u00a0 The cells with brownish pigments are actually keratinocytes that have received melanin granules from the melanocytes by pigment donation. The\u00a0<strong>slides<\/strong>\u00a0<strong>104-1<\/strong>and\u00a0<strong>104-2\u00a0<\/strong>are skin samples from light and darker skinned individuals.\u00a0 It is not difficult to tell which sample is from which individual.\u00a0 Note the presence of portions of hair follicles and sebaceous glands in the\u00a0dermis.<\/p>\n<h2>Peripheral Mechanosensory Receptors<\/h2>\n<h3>Meissner\u2019s\u00a0Corpuscles<\/h3>\n<ul>\n<li><strong>UCSF 180\u00a0<\/strong><em>finger tip H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/UCSF%20Histology\/UCSF180_40X.svs\/view.apml\">Webscope<\/a>\u00a0(virtual slide courtesy of the University of California, San Francisco)<\/li>\n<li><strong>112\u00a0<\/strong><em>thick skin, sole of foot H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a>(note, there\u2019s only one corpuscle apparent in this\u00a0slide)<\/li>\n<\/ul>\n<p>Meissner\u2019s corpuscles\u00a0<strong>#UCSF 180\u00a0meissner\u2019s corpuscles<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/UCSF%20Histology\/UCSF180_40X.svs\/view.apml?x=0.0656270071&amp;y=0.1073216394&amp;zoom=50.0000000000&amp;transform=\">Webscope\u00a0<\/a>are touch receptors that are responsive to low-frequency stimuli and are usually associated with hairless skin of the lips and palmar and plantar surfaces, particularly those of the fingers and toes. Generally, these receptors are tapered cylinders located in the undulating connective tissue just underneath the stratified epithelium of the skin. The long axis of the cylinder is perpendicular to that of the overlying epidermis and is usually about 150 um long and is usually tucked within extensions of the underlying connective tissue dermis (called \u201cdermal papillae\u201d) that project into the underside of the epidermis. Within these receptors, one or two nonmyelinated endings of myelinated nerve fibers follow a spiral path through the corpuscle. The fibers are accompanied by ensheathing Schwann cells, the nuclei of which are flattened and stacked on top of each other giving the corpuscle its characteristic irregular, lamellar\u00a0appearance.<\/p>\n<h3>Pacinian\u00a0Corpuscles<\/h3>\n<ul>\n<li><strong>108\u00a0<\/strong><em>fetal fingar Masson<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/108_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\n<li><strong>042\u00a0<\/strong><em>mesentery H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Cardiovascular%20System\/042_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\n<li><strong>095\u00a0<\/strong><em>Small arteries and vein H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Cardiovascular%20System\/095_HISTO_20X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\n<li><strong>095M\u00a0<\/strong><em>mesentary Masson<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Cardiovascular%20System\/095M_HISTO_40X.svs\/view.apml\">Webscope\u00a0<\/a><\/li>\n<\/ul>\n<p>Pacinian corpuscles\u00a0<strong>#095M\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Cardiovascular%20System\/095M_HISTO_40X.svs\/view.apml?x=0.1908347401&amp;y=0.1904834073&amp;zoom=25.0000000000&amp;transform=\">Webscope\u00a0<\/a>(best seen in slide 108) are large, ovoid structures up to 1 mm in diameter found in the dermis and hypodermis of the skin and also in the connective tissue associated with bones, joints, and internal organs. They respond primarily to pressure and vibration and are composed of a myelinated nerve ending surrounded by a capsule. The nerve enters the capsule at one pole (which might be out of the plane of section and therefore not visible) with its myelin sheath intact but then it is quickly lost. The unmyelinated portion of the axon extends toward the opposite pole from which it entered and its length is covered by flattened Schwann cell lamellae that form the inner core of the corpuscle. The remaining bulk of the capsule, or outer core, is comprised of a series of concentric, onionlike lamellae with each layer separated by an extracellular fluid similar to lymph. Each lamella is composed of flattened Schwann cells and endoneurial fibroblasts. In addition the fluid between each layer, delicate collagen fibers may be present as well as occasional capillaries. Displacement of the lamellae by pressure or vibrations effectively causes depolarization of the axon, which sends the signal to the central nervous\u00a0system.<\/p>\n<h2>Scalp and Hair<\/h2>\n<ul>\n<li><strong>107\u00a0<\/strong><em>Scalp hair H&amp;E<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/107_HISTO_40X.svs\/view.apml\">Webscope<\/a><\/li>\n<\/ul>\n<p>Underneath the thin epidermis, there are numerous circular to oblong structures with a hollow or yellow-brown center and surrounding cellular layers.\u00a0 These structures are hair follicles\u00a0<strong>#107\u00a0<\/strong>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/107_HISTO_40X.svs\/view.apml?x=0.1797414425&amp;y=0.1386101965&amp;zoom=6.4905471519&amp;transform=\">Webscope\u00a0<\/a>sectioned transversely or tangentially at different levels.\u00a0 The keratinized component of the hair occupies the central cavity of the follicle, and appears yellow-brown when present. However, the hair often falls out during tissue processing, in which case the central cavity will appear to be occupied by just empty space.\u00a0 The surrounding layers of clear cells form the external root sheath of the hair, which is a downgrowth of the epidermis. In fact, in cases where most of the epidermis is removed (such as severe abrasions or when taking skin graft), it is cells of the external root sheath that will divide and spread over the exposed surface to re-establish the epidermis. \u00a0 In some sections, you may also see an internal root sheath of darker staining cells right up against the hair follicle \u2013this is the layer of cells that actually produce the keratinized hair shaft. Note also the presence of sebaceous glands\u00a0<strong>#107\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/107_HISTO_40X.svs\/view.apml?x=0.1706576987&amp;y=0.2326887715&amp;zoom=36.0000000000&amp;transform=\">Webscope\u00a0<\/a>and the arrector pili muscle\u00a0<strong>#107\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/107_HISTO_40X.svs\/view.apml?x=0.1464568167&amp;y=0.2801145390&amp;zoom=100.0000000000&amp;transform=\">Webscope\u00a0<\/a>near the hair follicle.\u00a0 In most instances, you will not find complete pilosebaceous units in a single section, so a bit of mental reconstruction will be\u00a0required.<\/p>\n<h2>Sweat Glands<\/h2>\n<h3>Eccrine Sweat Gland<\/h3>\n<ul>\n<li><strong>106\u00a0<\/strong><em>Thick skin, sole of foot (Homo)\u00a0<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Basic%20Tissues\/Epithelium%20and%20CT\/106_HISTO_40X.svs\/view.apml?x=-0.2241109127&amp;y=-0.1057661521&amp;zoom=19.3806699468&amp;transform=\">Webscope<\/a><\/li>\n<li><strong>112\u00a0<\/strong>\u00a0<em>Thick skin (Homo)\u00a0<\/em><a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112_HISTO_40X.svs\/view.apml?x=-0.1451530172&amp;y=-0.1029983767&amp;zoom=19.3806699468&amp;transform=\">Webscope<\/a><\/li>\n<li><strong>112N\u00a0<\/strong><em>Thick skin (Homo)<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/112N_HISTO_40X.svs\/view.apml?x=-0.1292488527&amp;y=0.2329551176&amp;zoom=10.0371983993&amp;transform=\">Webscope<\/a><\/li>\n<li><strong>105-1\u00a0<\/strong><em>Thin skin (Homo)<\/em>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/105-1_HISTO_40X.svs\/view.apml?x=0.4583594194&amp;y=-0.3319463629&amp;zoom=30.0000000000&amp;transform=\">Webscope<\/a><\/li>\n<\/ul>\n<p>Numerous coiled\u00a0<span style=\"text-decoration: underline;\">eccrine<\/span>\u00a0<span style=\"text-decoration: underline;\">sweat<\/span>\u00a0<span style=\"text-decoration: underline;\">glands<\/span>\u00a0are located at the junction of dermis and hypodermis.\u00a0 The coiled morphology can be particularly appreciated in the example shown in\u00a0<strong>slide 112N<\/strong>. Distinguish between the\u00a0<span style=\"text-decoration: underline;\">secretory portions<\/span>\u00a0of the gland (secretory cells and myoepithelial cells; the latter are best seen in the apocrine gland, see below,\u00a0<strong>slide 111<\/strong>\u00a0and\u00a0<strong>104-2<\/strong>) and the stratified (two layers) cuboidal epithelial cell-lined\u00a0<span style=\"text-decoration: underline;\">duct<\/span>.\u00a0\u00a0<strong>Where do the ducts empty?<\/strong>?\u00a0Answer: Ducts of eccrine sweat glands empty onto the surface of the skin. Apocrine glands, however, empty into hair follicles in the axillary, areolar and perianal regions.\u00a0<strong>How does sweat get to the surface?<\/strong>\u00a0Answer: Eccrine sweat glands have ducts that lead to the surface of the skin. Eccrine sweat glands are a type of merocrine gland (a gland that releases its product by exocytosis). The secretory cells of the eccrine gland are surrounded by myoepithelial cells which can contract to propel its secretions to the surface. Apocrine sweat glands (apocrine being a misnomer, they are truly a merocrine gland, not an apocrine gland) function in the same way, however, their ducts lead to hair follicles, not directly to the skin\u00a0surface.<\/p>\n<h3>Apocrine Glands<\/h3>\n<ul>\n<li><strong>109-1\u00a0<\/strong><em>Perianal region Masson<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/109-1_HISTO_20X.svs\/view.apml\">Webscope<\/a><\/li>\n<li><strong>109-2\u00a0<\/strong><em>Perianal region PAS\/Pb hematoxylin<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/109-2_HISTO_20X.svs\/view.apml\">Webscope<\/a><\/li>\n<li><strong>111\u00a0<\/strong><em>axilla, subcutaneal region Masson<\/em>\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/111_HISTO_40X.svs\/view.apml\">Webscope<\/a><\/li>\n<li><strong>104-2\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/104-2_HISTO_40X.svs\/view.apml?x=0.3670398775&amp;y=0.1096661997&amp;zoom=14.2317090684&amp;transform=\">Webscope\u00a0<\/a>(this slide has both eccrine AND apocrine sweat glands; see if you can identify\u00a0them)<\/li>\n<\/ul>\n<p>Look in the deep dermis or hypodermis for secretory tubules with a wide lumen.\u00a0 The epithelium is cuboidal to columnar with distinct apical secretory granules.\u00a0 What should be apparent in your section is the apical \u201cblebbing\u201d of the secretory cells that was responsible for histologists originally designating these cells as \u201c<span style=\"text-decoration: underline;\">apocrine<\/span>\u201d secretory cells, although we now know the cells actually secrete in a MEROCRINE manner just like eccrine sweat glands.\u00a0 The \u201capocrine\u201d sweat glands, present in the axillary, areolar, and anal regions, represent the second type of sweat glands.\u00a0 These glands produce a viscous secretion which acquires a distinctive odor as a result of bacterial\u00a0decomposition.<\/p>\n<p>In complete transverse sections of the glands (e.g.\u00a0<strong>slide #111<\/strong>), look for oblong nuclei just inside the basement membrane.\u00a0 These are the nuclei of\u00a0<span style=\"text-decoration: underline;\">myoepithelial cells<\/span>.\u00a0 In some planes of section, the nuclei may appear round.\u00a0 Now look for a tangential section of the gland.\u00a0 Look for regularly spaced, elongate strands of cytoplasm\u00a0 investing the outside of the secretory epithelium.\u00a0 With a bit more looking you should be able to see that these elongate bits of cytoplasm contain the above mentioned oblong nuclei.\u00a0\u00a0<strong>Slide 104-2\u00a0<\/strong>is another good place to see myoepithelial cells\u00a0<strong>#104-2\u00a0<\/strong>\u00a0\u00a0<a href=\"http:\/\/141.214.65.171\/Histology\/Integumentary%20System\/104-2_HISTO_40X.svs\/view.apml?x=0.3670398775&amp;y=0.1096661997&amp;zoom=14.2317090684&amp;transform=\">Webscope\u00a0<\/a>; look for eosinophilic strands of cytoplasm and small nuclei just peripheral to the secretory epithelial cells. In PAS stained slides (e.g.\u00a0<strong>#109-2<\/strong>), densely staining granules are obvious in the apical cytoplasm the secretory cells, but the cytoplasm of myoepithelial cells is not well seen.\u00a0 Instead you see darker pink-stained basement membrane between the projections of myoepithelial cells.\u00a0 The relatively great number of these cells in sweat glands (and mammary glands) can only be appreciated by studying such tangential\u00a0cuts.<\/p>\n<p>Please also look for apocrine sweat gland ducts in these slides. They look similar to eccrine gland ducts described above (small diameter and small lumen with a stratified cuboidal epithelium). Similarly, they also lack lack myoepithelial cells. Make sure you can discriminate the ductal portion of apocrine sweat grlands from their secretory\u00a0portion.<\/p>\n<h2>Electron\u00a0Micrographs<\/h2>\n<ul>\n<li><strong>65 Epidermis\u00a0<i>Skin\u00a0<\/i><\/strong><a href=\"http:\/\/virtualslides.med.umich.edu\/Histology\/EMsmallCharts\/3%20Image%20Scope%20finals\/065%20-%20Epidermis_001.svs\/view.apml\">Webscope<\/a><\/li>\n<\/ul>\n<p>Review the layering of the epidermis. Remember that there is a continuous process of cell migration and differentiation from the basal cell layer to the most superficial layer. Review the features of the epidermal-dermal junction.<\/p>\n<ul>\n<li><strong>67 Epidermis &#8211; Details of the Stratum Spinosum\u00a0<i><\/i><\/strong><a href=\"http:\/\/virtualslides.med.umich.edu\/Histology\/EMsmallCharts\/3%20Image%20Scope%20finals\/067%20-%20Epidermis_001.svs\/view.apml\">Webscope<\/a><\/li>\n<\/ul>\n<p>Observe the abundance of tonofibrils (= keratin intermediate filaments) and ribosomes and the small number of mitochondria. Note the absence of Golgi apparatus and granular endoplasmic reticulum. Epidermal cells do contain these organelles but in reduced amount, as the bulk of synthesis is for structural proteins, not exportable ones. What is the function of the numerous desmosomes? The function of the tonofibrils? (IN4)<\/p>\n<ul>\n<li><strong>69 Epidermis \u2013 Details of the Stratum Granulosum and Stratum Corneum\u00a0<i><\/i><\/strong><a href=\"http:\/\/virtualslides.med.umich.edu\/Histology\/EMsmallCharts\/3%20Image%20Scope%20finals\/069%20-%20Epidermis_001.svs\/view.apml\">Webscope<\/a><\/li>\n<\/ul>\n<p>Note the keratohyaline granules in the cells of the stratum granulosum. The keratinization process is completed in the cell layers above the stratum granulosum, indicated by the disappearance of nuclei and cell organelles. Note that the cornified cells are of variable appearance (some &#8220;dark&#8221; and some &#8220;light&#8221;) a reflection of the tissue processing rather than of a functional difference.<\/p>\n<div class=\"textbox exercises\">\n<h3>Review Questions<\/h3>\n<ol>\n<li>What is the function of the numerous myoepithelial cells (in sweat\u00a0glands)?\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q594330\">Show Answer<\/span><\/p>\n<div id=\"q594330\" class=\"hidden-answer\" style=\"display: none\">Myoepithelial cells are what propel the secretory contents of the glands to the surface of the\u00a0body.\n<\/div>\n<\/div>\n<\/li>\n<li>What is the function of the epidermal ridges and dermal\u00a0papillae?\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q510934\">Show Answer<\/span><\/p>\n<div id=\"q510934\" class=\"hidden-answer\" style=\"display: none\">Epidermal ridges and dermal papillae provide increased surface area for the epidermis and dermis to\u00a0connect.\n<\/div>\n<\/div>\n<\/li>\n<li>Where do the ducts\u00a0empty?\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q50922\">Show Answer<\/span><\/p>\n<div id=\"q50922\" class=\"hidden-answer\" style=\"display: none\">Ducts of eccrine sweat glands empty onto the surface of the skin. Apocrine glands, however, empty into hair follicles in the axillary, areolar and perianal\u00a0regions.\n<\/div>\n<\/div>\n<\/li>\n<li>How does sweat get to the\u00a0surface?\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q454049\">Show Answer<\/span><\/p>\n<div id=\"q454049\" class=\"hidden-answer\" style=\"display: none\">Eccrine sweat glands have ducts that lead to the surface of the skin. Eccrine sweat glands are a type of merocrine gland (a gland that releases its product by exocytosis). The secretory cells of the eccrine gland are surrounded by myoepithelial cells which can contract to propel its secretions to the surface. Apocrine sweat glands (apocrine being a misnomer, they are truly a merocrine gland, not an apocrine gland) function in the same way, however, their ducts lead to hair follicles, not directly to the skin\u00a0surface.<\/div>\n<\/div>\n<\/li>\n<\/ol>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-1813\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Integumentary System and Mammary Gland. <strong>Authored by<\/strong>: Histology and Virtual Microscopy Learning Resources. <strong>Provided by<\/strong>: University of Michigan Medical School. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/histology.med.umich.edu\/medical\/integumentary-system\">http:\/\/histology.med.umich.edu\/medical\/integumentary-system<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA: Attribution-NonCommercial-ShareAlike<\/a><\/em><\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":74,"menu_order":6,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Integumentary System and Mammary Gland\",\"author\":\"Histology and Virtual Microscopy Learning Resources\",\"organization\":\"University of Michigan Medical School\",\"url\":\"http:\/\/histology.med.umich.edu\/medical\/integumentary-system\",\"project\":\"\",\"license\":\"cc-by-nc-sa\",\"license_terms\":\"\"}]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1813","chapter","type-chapter","status-publish","hentry"],"part":1792,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/pressbooks\/v2\/chapters\/1813","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/wp\/v2\/users\/74"}],"version-history":[{"count":13,"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/pressbooks\/v2\/chapters\/1813\/revisions"}],"predecessor-version":[{"id":3978,"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/pressbooks\/v2\/chapters\/1813\/revisions\/3978"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/pressbooks\/v2\/parts\/1792"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/pressbooks\/v2\/chapters\/1813\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/wp\/v2\/media?parent=1813"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/pressbooks\/v2\/chapter-type?post=1813"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/wp\/v2\/contributor?post=1813"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-ap1\/wp-json\/wp\/v2\/license?post=1813"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}