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Lesson 2 - The Dermis and Subcutaneous Tissue

Student Performance Objectives
1. Describe the organization of the dermis.
2. Explain three functions of the dermis
3. Describe the structure of the subcutaneous layer.
4. Describe three functions of the hypodermis.

Lesson Outline
A. The Dermis
    1. The upper layer of the dermis, or papillary layer, is a loose connective tissue layer
        (areolar connective tissue) containing the blood vessels, lymphatics and nerves that
        service the epidermis.
    2. The lower layer of the dermis, or reticular layer, is a dense irregular connective tissue
        layer whose bundled collagen fibers extend both deeply and superficially to bind the
        entire dermis and subcutaneous layers together.
3. The dermis contains the typical cells of fibrous connective tissue including fibroblasts,
        macrophages, lymphocytes, mast cells, and adipocytes.
    4. Collagen fibers of the dermis provide strength; the elastin fibers provide flexibility.
        Excessive stretching of the dermis as in pregnancy, weight gain, or body building, can
        tear the tissue resulting in scarring - stretch marks.
    5. The dermis has a rich blood supply organized into networks of blood vessels in the
        subcutaneous layer and dermis, and capillaries that loop superficially into the dermal
        papillae from which diffusion supplies nutrients to the epidermis.
    6. The dermis is richly innervated containing receptors for pressure and vibrations, pain,
        light touch, and temperature.
B. The Subcutaneous Layer (Hypodermis)
    1. The subcutaneous layer has many synonyms: hypodermis or superficial fascia, or tela
        subcutanea). It is a loose, irregular connective tissue with a high fat (adipose) content.
        It forms a continuous sheet surrounding all parts of the body just under the skin.
    2. It loosely but firmly attaches the skin to underlying tissues.
    3. Forms a subdivision between the skin and often the striated muscle beneath it.
    4. Provides a passageway for blood vessels and nerves to reach the skin.
    5. Helps body temperature regulation through dilation or constriction of blood vessels
        thus bringing more or less heat to the body surface.
    6. Provides insulation against body heat loss through the thickness of the adipose layer.
    7. Stores energy as lipid (mostly triglyceride) in adipose tissue. This fat can be
        released into the blood and reach the liver and other organs for metabolism.

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