INTEGUMENTARY SYSTEMIntegumentary System or skin actually make a difference in opinion as to whether an organ or organ system only. Organ called the skin because it has four basic network as the constituent epithelial tissues (epithelium where the dominant is layered flat epithelium), connective tissue or connective tissue made up of collagen fibers, elastin fibers and adipose, muscle cells found in the lining of nerve cells in the dermis and nerve fibers form and korpuskula.While the skin is called organ systems because the skin does not only consist of an organ skin, but also contains a lot of variation in sub-organs such as the appendix to the sweat glands, oil glands, hair, nails and skin all sorts of derivatives.The integumen system also have derivate. Skin actually is a layer that covered the body which generally composed by two principal layers in outside the slack connective tissue, whereas their integument derivate composed by some certain structures which originated from epidermis and dermis layer. That certain structure cam be form like fur, hair, horn and scales, gland and etc. So, we can say the integument derivate of skin can be formed in hard or soft structure.

Structure of the SkinThe superficial, thinner portion, which is composed of epithelial tissue, is the epidermis The deeper, thicker connective tissue portion is the dermis. Deep to the dermis, but not part of the skin, is the subcutaneous (subQ) layer. Also called the hypodermis), this layer consists of areolar and adipose tissues.

I. EpidermisThe epidermis is composed of keratinized stratified squamous epithelium. It contains four principal types of cells: keratinocytes, melanocytes, Langerhans cells, and Merkel cells.

About 90% of epidermal cells are keratinocytes which are arranged in four or five layers and produce the protein keratin. Keratin is a ough, fibrous protein that helps protect the skin and underlying tissues from heat, microbes, and chemicals. Keratinocytes also produce lamellar granules, which release a water-repellent sealant that decreases water entry and loss and inhibits the entry of foreign materials. About 8% of the epidermal cells are melanocytes), which develop from the ectoderm of a developing embryo and produce the pigment melanin. Their long, slender projections extend between the keratinocytes and transfer melanin granules to them. Melanin is a yellow-red or brown-black pigment that contributes to skin color and absorbs damaging ultraviolet (UV) light. Langerhans cells arise from red bone marrow and migrate to the epidermis where they constitute a small fraction of the epidermal cells.. Merkel cells are the least numerous of the epidermal cells. They are located in the deepest layer of the epidermis, where they contact the flattened process of a sensory neuron (nerve cell), a structure called a Merkel (tactile) disc . Merkel cells and their associated Merkel discs detect touch sensations. Several distinct layers of keratinocytes in various stages of development form the epidermis. In most regions of the body the epidermis has four strata or layersstratum basale, stratum spinosum, stratum granulosum, and a thin stratum corneum. This is called thin skin. Where exposure to friction is greatest, such as in the fingertips, palms, and soles, the epidermis has five layersstratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and a thick stratum corneum. This is called thick skin. a. Stratum BasaleThe epidermal cells of the stratum basale are closest to these blood vessels and receive most of the nutrients and oxygen. These cells are the most active metabolically and continuously undergo cell division to produce new keratinocytes. Some cells in this layer are stem cells that undergo cell division to continually produce new keratinocytes. The nuclei of keratinocytes in the stratum basale are large, and their cytoplasm contains many ribosomes, a small Golgi complex, a few mitochondria, and some rough endoplasmic reticulum. The stratum basale is also known as the stratum germinativum to indicate its role in forming new cells.b. Stratum SpinosumSuperficial to the stratum basale is the stratum spinosum arranged in 8 to 10 layers of many-sided keratinocytes fitting closely together. These keratinocytes have the same organelles as cells of the stratum basale. When cells of the stratum spinosum are prepared for microscopic examination, they shrink and pull apart so that they seem to be covered with thornlike spines although they appear rounded and larger in living tissue. Each spiny projection in a prepared tissue section is a point where bundles of tonofilaments are inserting into a desmosome, tightly joining the cells to one another. This arrangement provides both strength and flexibility to the skin. Langerhans cells and projections of melanocytes are also present in this layer.

c. Stratum GranulosumAt about the middle of the epidermis, the stratum granulosum consists of three to five layers of flattened keratinocytes that are undergoing apoptosis. The nuclei and other organelles of these cells begin to degenerate, and tonofilaments become more apparent. A distinctive feature of cells in this layer is the presence of darkly staining granules of a protein called keratohyalin, which converts the tonofilaments into keratin. Also present in the keratinocytes are membraneenclosed lamellar granules, which release a lipid-rich secretion.This secretion fills the spaces between cells of the stratum granulosum, stratum lucidum, and stratum corneum. The lipid-rich secretion acts as a water-repellent sealant, retarding loss and entry of water and entry of foreign materials. As their nucleibreak down during apoptosis, the keratinocytes of the stratum granulosum can no longer carry on vital metabolic reactions, and they die. Thus, the stratum granulosum marks the transition between the deeper, metabolically active strata and the dead cells of the more superficial strata.d. Stratum LucidumThe stratum lucidum is present only in the thick skin of areas such as the fingertips, palms, and soles. It consists of three to five layers of flattened clear, dead keratinocytes that contain large amounts of keratin and thickened plasma membranes.e. Stratum CorneumThe stratum corneum consists on average of 25 to 30 layers of flattened dead keratinocytes. These cells are continuously shed and replaced by cells from the deeper strata. The interior of the cells contains mostly keratin. Between the cells are lipids from lamellar granules that help make this layer an effective water-repellent barrier. Its multiple layers of dead cells also help to protect deeper layers from injury and microbial invasion. Constant exposure of skin to friction stimulates the formation of a callus, an abnormal thickening of the stratum corneum.

II. DermisThe dermis is essential to the survival of the epidermis, and these adjacent layers form many important structural and functional relations. Based on its tissue structure, the dermis can be divided into a superficial papillary region and a deeper reticular region. a) The papillary region makes up about one-fifth of the thickness of the total layer. It consists of areolar con-nective tissue containing thin collagen and fine elastic fibers. Its surface area is greatly increased by dermal papillae, small, fingerlike structures that project into the undersurface of the epidermis. Some of these nipple-shaped structures contain capillary loops (blood vessels). Some dermal papillae also contain tactile receptors called Meissner corpuscles or corpuscles of touch, nerve endings that are sensitive to touch, and free nerve endings, dendrites that lack any apparent structural specialization. Different free nerve endings initiate signals that give rise to sensations of warmth, coolness, pain, tickling, and itching. b) The reticular region, which is attached to the subcutaneous layer, consists of dense irregular connective tissue containing fibroblasts, bundles of collagen, and some coarse elastic fibers. The collagen fibers in the reticular region interlace in a netlike manner. A few adipose cells, hair follicles, nerves, sebaceous (oil) glands, and sudoriferous (sweat) glands occupy the spaces between fibers. The combination of collagen and elastic fibers in the reticular region provides the skin with strength, extensibility (ability to stretch), and elasticity (ability to return to original shape after stretching).

III. Epidermis DerivativeEpidermis Derivative of mammals1. HAIR, Each hair is composed of columns of dead, keratinized epidermal cells bonded together by extracellular proteins. a) The shaft is the superficial portion of the hair, which projects above the surface of the skin b) The shaft is the portion of the hair deep to the shaft that penetrates into the dermis, and sometimes into the subcutaneous layer. The shaft and root of the hair both consist of three concentric layers of cells: medulla, cortex, and cuticle of the hair. The inner medulla, which may be lacking in thinner hair. The middle cortex forms the major part of the shaft and consists of elongated cells. The cuticle of the hair, the outermost layer, consists of a single layer of thin, flat cells that are the most heavily keratinized. c) hair follicle was found surrounding the root , which is made up of an external root sheath and an internal root sheath, together referred to as an epithelial root sheath .d) The dense dermis surrounding the hair follicle is called the dermal root sheath. The base of each hair follicle and its surrounding dermal root sheath is an onion-shaped structure.e) The bulb, This structure houses a nipple-shaped indentation, the papilla of the hair, which contains areolar connective tissue and many blood vessels that nourish the growing hair follicle. The bulb also contains a germinal layer of cells called the hair matrix. f) The hair matrix cells arise from the stratum basale, the site of cell division. Hence, hair matrix cells are responsible for the growth of existing hairs, and they produce new hairs when old hairs are shed.

NailsNails are plates of tightly packed, hard, dead, keratinized epidermal cells that form a clear, solid covering over the dorsal surfaces of the distal portions of the digits. Each nail consists of a nail body, a free edge, and a nail root. 1) The nail body (plate) is the visible portion of the nail. It is comparable to the stratum corneum of the general epidermis, with the exception that its flattened, keratinized cells fill with a harder type of keratin and do not shed. Below the nail body is a region of epithelium and a deeper layer of dermis. Most of the nail body appears pink because of blood flowing through the capillaries in the underlying dermis. 2) The free edge is the part of the nail body that may extend past the distal end of the digit. The free edge is white because there are no underlying capillaries. 3) The nail root is the portion of the nail that is buried in a fold of skin. The whitish, crescent-shaped area of the proximal end of the nail body is called the lunula. Beneath the free edge is a thickened region of stratum corneum called the hyponychium or nail bed, which secures the nail to the fingertip. The eponychium or cuticle is a narrow band of epidermis that extends from and adheres to the margin (lateral border) of the nail wall. It occupies the proximal border of the nail and consists of stratum corneum. The proximal portion of the epithelium deep to the nail root is the nail matrix, where cells divide by mitosis to produce growth. Nail growth occurs by the transformation of superficial cells of the matrix into nail cells. The growth rate of nails is determined by the rate of mitosis in matrix cells, which is influenced by factors such as a persons age, health, and nutritional status.

Epidermis Derivative of AvesFURA keratin structures that are characteristic of the nation's bird, and is considered as modification of Scales. Aves by evolutionary ancestors of reptilian. 1) Penna, the type of fur that is only found in certain areas, called kemiges the wings and the tail called retrices. Kemiges and retrices pivotal movement preformance. While the other penna feather cell was protective properties.2) plumula, the tiny hairs with a stout rachis. At the rachis there are hemp and radicalism that serves as insulation in chicks.3) Filopium, are feathers very fine hair, feathers in birds in9 is characteristic casuari.

IV. Dermis DerivativeDerivatives dermis consists of dermal scales, dermal insert fingers, and keeping the bone or tissue osteoderm. Some kind of castings contained in the dermis are the components that make up the dermal scales, composed of bone tissue, isopedin, dentin, Kosmin, ganoin, and e-mail.1. Almost all nations have fish scales. That be done of structure or similar bone by bone. There are five main kinds of scales:a) Scales plakoidb) Scales kocmoidc) Scales paleoniskoidd) Scales ganoide) Scales leptoid

2. Osteoderm in tetrapodsAmphibians generally do not have scales. But the reptile-keeping has keeping bone as in Lacertilia (Varanus). In veranus, crocodilian and there spenodon osteoderm which is adjacent vental body, called abdominal ribs or grastula. The difference sdengan regular ribs, gastrula not related to the spine, it is considered a modification osteoderm have.

V. Function of the skinRegardless of what is the appropriate designation for the skin - as a system or organ - the skin is the body part that is so important and is a contributor to 15% of total body weight. All too must have known function of the skin. But though more details, skin have some functions that I can take from several sources and outcomes dirty here and there. Skin function is as follows:

1. ThermoregulationRecall that thermoregulation is the homeostatic regulation of body temperature. The skin contributes to thermoregulation in two ways: by liberating sweat at its surface and by adjusting the flow of blood in the dermis.2. Blood ReservoirThe dermis houses an extensive network of blood vessels that carry 810% of the total blood flow in a resting adult. For thisreason, the skin acts as a blood reservoir.3. ProtectionThe skin provides protection to the body in various ways. Like Keratin protects underlying tissues from microbes, abrasion, heat, and chemicals and the tightly interlocked keratinocytes resist invasion by microbes and so on.

4. Cutaneous SensationsCutaneous sensations are sensations that arise in the skin, including tactile sensationstouch, pressure, vibration, and ticklingas well as thermal sensations such as warmth and coolness. 5. Excretion and AbsorptionThe skin normally has a small role in excretion, the elimination of substances from the body, and absorption, the passage of materials from the external environment into body cells. 6. Synthesis of Vitamin DSynthesis of vitamin D requires activation of a precursormolecule in the skin by ultraviolet (UV) rays in sunlight.