Chapter 5 – The Integumentary System 1.Describe the anatomy and major functions of the skin.1.Integumentary systemIs composed of the skin, hair, oil and sweat glands, nails, and sensory receptors. The integumentary system helps maintain a constant body temperature, protects the body, andprovides sensory information about the surrounding environmentStores blood Protects body from external environment Detects cutaneous sensations Excretes and absorbs substances Synthesizes vitamin D2.Skin or cutaneous membraneThe skin is also known as the cutaneous membrane, covers the external surface of the body and is the largest organ of the body in weight 3.EpidermisThe thinner portion, which Is composed of epithelial tissue 4.DermisThe deeper, thicker connective tissue portion is the dermis. While the epidermis is avascular, thus the dermis is vascular.5.Subcutaneous (SQ) layer or hypodermisDeep to the dermis, but not part of the skin, is the subcutaneous (subQ) layer. Moreover, called the hypodermis, this layer consists of areolar and adipose tissues.Fibers that extend from the dermis anchor the skin to the subcutaneous layer, which in turn attaches to underlying fascia, the connective tissue around muscles and bones. The subcutaneous layer serves as a storage depot for fat and contains large blood vessels that supply the skin. This region (and sometimes the dermis) also contains nerve endings called lamellated corpuscles or pacinian corpuscles. 6.EpidermisI.KeratinocyteAbout 90% of epidermal cells are these which are arranged in 4 or 5 layers and produce protein keratin. II.Keratin Is a tough, fibrous protein that helps protect the skin and underlying tissues from abrasions, 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.III.Melanocyte – 8% of the epidermal cells are these, which develop from the ectoderm of a developing embryo and produce the pigment melanin a.MelaninIs a yellow-red or brown-black pigment that contributes to skin color and absorbs damaging ultraviolet (UV) light. Once inside keratinocytes, the melanin granules cluster to form a protective veil over the nucleus, on the side toward the skin surface.
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