Skin Basics Structure Function and Aging Changes By

Skin Basics Structure, Function, and Aging Changes By: Maria Kneusel RN, BSN 2012

Some Facts About Skin • Skin is the largest organ of the body. • It accounts for up to 15% of the body’s weight. • Skin may hold up to 5% of the body’s blood supply. • Together with hair and nails, it comprises the Integumentary System.

Skin Structure Skin consists of three main layers: 1. Epidermis 2. Dermis 3. Hypodermis (Subcutaneous Tissue)

Epidermis • The outermost layer of the skin • Avascular (not containing blood vessels) • Measures between 0. 05 -0. 1 mm in thickness. • Replaced with new cells every 28 days. • Contains Keratinocytes, Melanocytes, Langerhans cells, and Merkel cells

Epidermal Cells Keratinocytes Melanocytes Langerhans • 90% of epidermal cells • Responsible for vitamin D synthesis • Produce Keratin (protective skin barrier) • 5% of • Alert immune epidermal cells system to the presence of • Found in the pathogens in basal cell layer. skin. • Produce Melanin (skin pigment) • Regulate immune response to skin pathogens. Merkel • Unknown function. • Localized in touch-sensitive areas such as fingertips. • Recent studies in mice suggest they play a role in the ability to sense texture.

Epidermis Epidermal Structure

Dermis • Highly vascular connective tissue layer. • Measures between 1 - 4 mm in thickness. • Assists with temperature and blood pressure regulation. • Houses nerves, blood vessels, sebaceous glands, sweat glands, and hair follicles. • Contains Fibroblasts.

Dermal Cells Fibroblasts • Primary cells in the Dermis • Produce collagen (mechanical strength of skin). • Produce elastin (necessary in wound healing).

Dermal Structure

Hypodermis (Subcutaneous Tissue) • Located beneath the dermis. • Attaches dermis to underlying tissues (muscle or bone). • Provides insulation. • Provides shock absorption. • Contains adipocytes (fat cells).

Hypodermal Cells Adipocytes • Primary cells in subcutaneous tissue. • Separated by collagen fibers and larger blood vessels. • Amounts vary with age, gender, heredity and nutrition.

Hypodermal Structure Retrieved from: http: //classes. midlandstech. edu/carterp/Courses/bio 110/chap 05/110 chap 05. htm

Skin Functions The skin serves a variety of functions: 1. Protection 4. Infection control 2. Temperature regulation 5. Sensory perception 3. Excretion 6. Vitamin D production

Skin Functions (cont. ) Protection Protects underlying tissues from damage due to sunlight, environmental chemicals, viruses or bacteria, trauma, and fluid loss. Regulates temperature in two ways: Temperature Regulation 1. Stimulation of sweat glands: as sweat evaporates off the skin’s surface, the body temperature drops. 2. Blood relocation: as core temperature rises, blood is moved toward the skin’s surface to release heat into the air. When core temperature drops, blood is moved away from skin and to internal organs to warm up the core.

Skin Functions (cont. ) Excretion Infection Control Through sweating, the skin excretes toxins and waste products including urea, lactic acid and sodium chloride. The skin is the first line of defense against invading pathogens. Langerhans cells found in the epidermis serve immune function by warning the immune system of pathogens found in skin, and by controlling the intensity of the immune response to skin pathogens.

Skin Functions (cont. ) Sensory Perception Millions of nerve endings found in the dermis allow the skin to sense pressure, temperature, and pain. This ability serves as a protective mechanism. Damage to dermal nerves can lead to loss of protective sensation, which could result in tissue injury. Vitamin D Production Vitamin D is synthesized when skin cells are exposed to UV rays of a specific wavelength. Vitamin D plays an important part in calcium absorption as well as cardiovascular and immune health.

Aging and Skin Changes Aging can affect skin function in various ways: • Fewer melanocytes lead to decreased pigmentation and impaired protection against harmful UV rays. • Atrophy of sebaceous glands leads to dry skin. • Loss of elastin fibers leads to wrinkling.

Aging (cont. ) • Increased permeability to substances leads to higher potential for skin irritation. • Decreased fibroblast production and fragmented collagen lead to weaker skin that can tear more easily. • Decreased, more fragile vasculature leads to impaired wound healing and easy bruising. • Fewer nerve endings lead to reduced pressure and touch perception.

Aging (cont. ) • Decreased sweat production leads to poor temperature control and impaired excretion of waste products. Image retrieved from: http: //www. nlm. nih. gov/medlineplus/ency/imagepages/8690. htm • Loss of subcutaneous fat can lead to hypothermia and lessened shock absorption, increasing vulnerability to injury from pressure or repetitive impact.

Concluding Points • Skin plays an important role in wellness. • Knowledge of the skin’s basic structures and their functions can help nurses improve patient care. • Aging skin changes can be significant and impact overall health and quality of life.

References Birmingham City University (n. d. ). The Skin. Retrieved from: http: //www. hcc. bcu. ac. uk/physiology/Skin. htm Prentice A. , Goldberg, G. R. , Schoenmakers, I. (2008). Vitamin D across the lifecycle. American Journal of Clinical Nutrition. 88(2) 500 s-506 s Festa E. , Fretz, J. , Berry, R. , Schmidt, B. , Rodeheffer, M. , & Horowitz, M. (2011) Adipocyte Lineage Cells Contribute to the skin stem cell niche to drive hair cycling. Cell. 146, 761– 771. DOI 10. 1016/j. cell. 2011. 07. 019 Gu, L-H. , Cuolombe, P. A. , (2007) Keratin function in skin epithelia: a broadening palette with surprising shades. Current Opinion in Cell Biology. 19: 13– 23 Haberle, H. , Lumpkin, E. A. , (2008, June 1) Merkel cells in somatosensation. Chemosens Percept. 1(2): 110– 118. doi: 10. 1007/s 12078 -008 -9012 -6. Jarvis, C. (2008). Physical examination and health assessment (5 th ed. ) St. Louis, MO: Mosby Elsevier

References (cont. ) Lewis, L. S. , Heitkemper M. , Dirsken, S. R. , O’Brien, P. G. , Bucher, L. (2007). Medicalsurgical nursing: Assessment and management of clinical problems (7 th ed. ). St. Louis, MO: Mosby Elsevier Maricich, S. M. , Morrison K. M. , Mathes, E. L. , Brewer, B. M. (2012) Rodents rely on merkel cells for texture discrimination Tasks. The journal of neuroscience. 32(10) 3296 – 3300 Mc. Cance, K. L. , Huether, S. E. (2010). Pathophysiology: The biologic basis for disease in adults and children. Maryland Heights, MO: Mosby Elsevier Sparber, F. , Tripp C. H. , Hermann, M. , Romani, M. , Stoitzner, P. (2010). Langerhans cells and dermal dendritic cells capture protein antigens in the skin: Possible targets for vaccination through the skin. Immunobiology. 215(9 -10): 770– 779. doi: 10. 1016/j. imbio. 2010. 05. 014. Yale University (2005, December 20). Langerhans Cells Regulate Immune Reactions In The Skin. Science Daily. Retrieved April 24, 2012