Integumentary System. The integumentary system is an organ system consisting of the skin, hair, nails, and exocrine glands. The skin is only a few millimeters thick yet is by far the largest organ in the body. The average persons skin weighs 1. Skin forms the bodys outer covering and forms a barrier to protect the body from chemicals, disease, UV light, and physical damage. Hair and nails extend from the skin to reinforce the skin and protect it from environmental Continue Scrolling To Read More Below. Continued From Above. Stratum 1 Black' title='Stratum 1 Black' />Learning Objectives 1. Describe the structures and main functions of the skin. Explain the functions of keratin and melanin. Identify the. The Raspberry Pi as a Stratum1 NTP Server. As an experiment, I purchased one of the lowcost creditcardsize Raspberry Pi computers, and have configured it to run. Noble definition, distinguished by rank or title. See more. StratumAqua,Blue,Orange chic custom wallpaper by franbail for sale on Spoonflower. CHAPTER 3 Basic Biology of the Skin Cholecalciferol is converted into 25hydroxycholecalciferol 25OH in the liver and nally to activated 1, 25 hydroxychole. JPG&w=600&q=85&zc=2' alt='Stratum 1 Black' title='Stratum 1 Black' />The exocrine glands of the integumentary system produce sweat, oil, and wax to cool, protect, and moisturize the skins surface. Anatomy of the Integumentary System. Epidermishe epidermis is the most superficial layer of the skin that covers almost the entire body surface. Best Loft Driver Distance'>Best Loft Driver Distance. The epidermis rests upon and protects the deeper and thicker dermis layer of the skin. Structurally, the epidermis is only about a tenth of a millimeter thick but is made of 4. The epidermis is an avascular region of the body, meaning that it does not contain any blood or blood vessels. The cells of the epidermis receive all of their nutrients via diffusion of fluids from the dermis. The epidermis is made of several specialized types of cells. Almost 9. 0 of the epidermis is made of cells known as keratinocytes. Stratum 1 Black' title='Stratum 1 Black' />Keratinocytes develop from stem cells at the base of the epidermis and begin to produce and store the protein keratin. Keratin makes the keratinocytes very tough, scaly and water resistant. At about 8 of epidermal cells, melanocytes form the second most numerous cell type in the epidermis. Melanocytes produce the pigment melanin to protect the skin from ultraviolet radiation and sunburn. Langerhans cells are the third most common cells in the epidermis and make up just over 1 of all epidermal cells. Langerhans cells role is to detect and fight pathogens that attempt to enter the body through the skin. Finally, Merkel cells make up less than 1 of all epidermal cells but have the important function of sensing touch. Merkel cells form a disk along the deepest edge of the epidermis where they connect to nerve endings in the dermis to sense light touch. In most of the body, the epidermis is arranged into 4 distinct layers. In the palmar surface of the hands and plantar surface of the feet, the skin is thicker than in the rest of the body and there is a fifth layer of epidermis. The deepest region of the epidermis is the stratum basale, which contains the stem cells that reproduce to form all of the other cells of the epidermis. The cells of the stratum basale include cuboidal keratinocytes, melanocytes, and Merkel cells. Superficial to stratum basale is the stratum spinosum layer where Langerhans cells are found along with many rows of spiny keratinocytes. The spines found here are cellular projections called desmosomes that form between keratinocytes to hold them together and resist friction. Just superficial to the stratum spinosum is the stratum granulosum, where keratinocytes begin to produce waxy lamellar granules to waterproof the skin. The keratinocytes in the stratum granulosum are so far removed from the dermis that they begin to die from lack of nutrients. In the thick skin of the hands and feet, there is a layer of skin superficial to the stratum granulosum known as the stratum lucidum. The stratum lucidum is made of several rows of clear, dead keratinocytes that protect the underlying layers. The outermost layer of skin is the stratum corneum. The stratum corneum is made of many rows of flattened, dead keratinocytes that protect the underlying layers. Dead keratinocytes are constantly being shed from the surface of the stratum corneum and being replaced by cells arriving from the deeper layers. Dermis. The dermis is the deep layer of the skin found under the epidermis. The dermis is mostly made of dense irregular connective tissue along with nervous tissue, blood, and blood vessels. The dermis is much thicker than the epidermis and gives the skin its strength and elasticity. Within the dermis there are two distinct regions  the papillary layer and the reticular layer. The papillary layer is the superficial layer of the dermis that borders on the epidermis. The papillary layer contains many finger like extensions called dermal papillae that protrude superficially towards the epidermis. The dermal papillae increase the surface area of the dermis and contain many nerves and blood vessels that are projected toward the surface of the skin. Blood flowing through the dermal papillae provide nutrients and oxygen for the cells of the epidermis. The nerves of the dermal papillae are used to feel touch, pain, and temperature through the cells of the epidermis. The deeper layer of the dermis, the reticular layer, is the thicker and tougher part of the dermis. The reticular layer is made of dense irregular connective tissue that contains many tough collagen and stretchy elastin fibers running in all directions to provide strength and elasticity to the skin. The reticular layer also contains blood vessels to support the skin cells and nerve tissue to sense pressure and pain in the skin. Hypodermis. Deep to the dermis is a layer of loose connective tissues known as the hypodermis, subcutis, or subcutaneous tissue. The hypodermis serves as the flexible connection between the skin and the underlying muscles and bones as well as a fat storage area. Areolar connective tissue in the hypodermis contains elastin and collagen fibers loosely arranged to allow the skin to stretch and move independently of its underlying structures. Fatty adipose tissue in the hypodermis stores energy in the form of triglycerides. Adipose also helps to insulate the body by trapping body heat produced by the underlying muscles. Hair. Hair is an accessory organ of the skin made of columns of tightly packed dead keratinocytes found in most regions of the body. The few hairless parts of the body include the palmar surface of the hands, plantar surface of the feet, lips, labia minora, and glans penis. Hair helps to protect the body from UV radiation by preventing sunlight from striking the skin. Hair also insulates the body by trapping warm air around the skin. The structure of hair can be broken down into 3 major parts the follicle, root, and shaft. The hair follicle is a depression of epidermal cells deep into the dermis. Stem cells in the follicle reproduce to form the keratinocytes that eventually form the hair while melanocytes produce pigment that gives the hair its color. Within the follicle is the hair root, the portion of the hair below the skins surface. As the follicle produces new hair, the cells in the root push up to the surface until they exit the skin. The hair shaft consists of the part of the hair that is found outside of the skin. The hair shaft and root are made of 3 distinct layers of cells the cuticle, cortex, and medulla. The cuticle is the outermost layer made of keratinocytes. The keratinocytes of the cuticle are stacked on top of each other like shingles so that the outer tip of each cell points away from the body. Under the cuticle are the cells of the cortex that form the majority of the hairs width. The spindle shaped and tightly packed cortex cells contain pigments that give the hair its color. The innermost layer of the hair, the medulla, is not present in all hairs. Download Adobe Pagemaker 7 Manual Pdf. When present, the medulla usually contains highly pigmented cells full of keratin.