Integumentary System

1. Integumentary System Chapter 5

2. Learner Objectives • To analyze the structural and functional relationships of the tissues within the integument. • To identify characteristics of the aging process on the integumentary system. • To investigate the role of radiation in cancer and mutations. • To analyze the effects of force on the skin.

3. Functions • Protects internal structures, prevents the entry of infectious agents, regulates body temperature, produces vitamin D, and detects stimuli such as touch, pain, and temperature.

4. Hypodermis • Not really a layer of the skin (subcutaneous tissue or superficial facia) – the “basement” of the skin. • Attaches the skin to underlying bone and muscle. • Loose connective tissue with collagen and elastin fibers. • Cells are predominately fibroblasts, adipose cells, and macrophages. • It is full of blood vessels and nerves. • ½ of the bodies stored fat.

5. Epidermis • Stratified squamous epithelium separated from the dermis by its basement membrane. • Thin, not blood vessels, nourished by diffusion from the capillaries in the papillary layer of the dermis. • Most of the cells are keratinocytes which produce keratin (protein mixture). • Keratinocytes are responsible for the structural strength and permeability. • Melanocytes are also present – skin color. • The stages of keratinization form the strata of the epidermis.

6. Epidermis • Stratum Basale: most deep strata. Single layer of cuboidal shaped cells. Epidermis anchored to the basement membrane by cell junctions. Cells are called keratinocytes. Mitosis occurs every 19 days and it takes 40-56 days for the stratum basale to reach the surface.

7. Epidermis • Stratum Spinosum: 8 to 10 layers of many-sided cells which flatten as they move toward the surface. Additional keratin fibers and lipid filled organelles (called lamillar bodies) within the kertinocytes. No mitosis occurs. Cell connection begin to degenerate.

8. Epidermis • Stratum Granulosum: 2-5 layers of flattened diamond-shaped cells with long axes which are parallel to the surface. Protein granules called keratohyelin accumulates in the cytoplasm.

9. Epidermis • Stratum Lucidum: Thin clear zone – several layers of dead cells without boundaries. Keratin fibers present but not granules. • Only see this layer in thick skin.

10. Epidermis • Stratum Corneum: most superficial stratum. 25 or more layers of dead stratified squamous cells. Cornified cells – dead cells surrounded by a hard protein. • Exocrine gland ducts come to the surface of this layer to secrete sebaceous oils and sweat.

12. Dermis • Dense irregular connective tissue with fibroblasts, few adipose cells and macrophage. • Structural strength of the skin. • Nerve endings, hair follicles, smooth muscles, glands and lymphatics extend into the dermis. • Made of 2 indistinct layers: Reticular and Papillary.

13. Dermis – Reticular Layer • Deep • Continuous with hypodermis. • Main fibrous layer with mats of fibers resist stretching. • Elastin and collagen are heavier in some areas – results in cleavage or tension lines. If the skin is overstretched the dermis may rupture leaving striae or stretchmarks.

14. Dermis – Papillary Layer • Superficial • Extensions (papillae) that go into the epidermis. • Layer has more cells and fewer fibers. • There are a large number of blood vessels which supply the epidermis with blood, nutrients, remove wastes, and aid in regulating the body temperature.