Student Performance Objectives1. Describe the organization of the dermis. 2. Explain three functions of the dermis3. Describe the structure of the subcutaneous layer.4. Describe three functions of the hypodermis.
Lesson OutlineA. 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) http://www.enchantedlearning.com/subjects/anatomy/skin/ 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.