MSU BIO215 Lecture - Week 05 Objective Assignment

MSU BIO215 Lecture - Week 05 Objective Assignment - BIOL215...

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BIOL215 Lecture Week 05 Objective Assignment Chapter 5: The Integumentary System The Skin 1. Name the tissue types composing the epidermis and dermis. List the major layers of each and describe the function of each layer. The epidermis is the outermost portion, which in subdivided into thin layers called strata. The epidermis is composed entirely of epithelial cells and contains no blood vessels. As the surface layer of skin, the cells of the epidermis are constantly lost through wear and tear. Because there are no blood vessels in the epidermis, the only living cells are in its deepest layer, the stratum germinativum, where nourishment is provided by capillaries in the underlying dermis. The cells in this layer are constantly dividing and producing daughter cells, which are pushed upward toward the surface. As the surface cells die from the gradual loss of nourishment, they undergo changes in that they develop large amounts keratin, a protein that serves to thicken and protect the skin. By the time the epidermal cells reach the surface, they have become flat and horny, forming the uppermost layer of the epidermis, the stratum corneum. Between the stratum germinativum and the stratum corneum, there are additional layers that vary in number and quantity depending on the thickness of the skin. Cells in the deepest layer of the epidermis produce melanin, the dark pigment that colors the skin. The dermis is our true skin, which has a framework of connective tissue and contains many blood vessels, nerve endings, and glands. What we see as our true skin, the dermis has a framework of elastic connective tissue and is well supplied with blood vessels and nerves. Because of its elasticity, the skin can stretch with little damage. Most of the appendages of the skin, including the sweat glands, oil glands, and hair are located in the dermis and may extend into the subcutaneous layer under the skin. The thickness of the dermis also varies in different areas. Some areas like the soles of our feet and the palms of our hands are covered with very thick layers of skin. Other areas like the eyelids are covered with very thin delicate layers. Portions of the dermis extend upward into the epidermis, allowing blood vessels to get closer to the surface cells. These papillae are extension that form a distinct pattern of ridges on the surface of thick skin which help to prevent slipping, such as when picking up or grasping an object. The unchanging patterns of the ridges are determined by heredity. The skin has many functions; the main four functions are protection against infection, protection against dehydration, regulation of body temperature, and collection of sensory information. The skin forms a primary barrier against invasion of pathogens.
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This note was uploaded on 05/07/2010 for the course BIOLOGY BIO 215 taught by Professor Tucker during the Spring '10 term at Mountain State.

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MSU BIO215 Lecture - Week 05 Objective Assignment - BIOL215...

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