The Integumentary System The skin, hair, & nails… The “underappreciated” system

Objectives: List the components of the integumentary system & describe their physical relationship to each other & to the subcutaneous layer. Specify the general functions of the integumentary system Describe the main structural features of the epidermis, and explain their functional significance Explain what accounts for individual and racial differences in skin, such as skin color Discuss the effects of ultraviolet radiation on the skin and the role played by melanocytes. Describe the structure and functions of the dermis Describe the structure and functions of the subcutaneous layer Discuss the various kinds of glands in the skin and the secretions of those glands Explain how the sweat glands of the integumentary system play a major role in regulating body temperature. Explain how the skin responds to injury and repairs itself Learn selected clinical terminology blahblahabl

Integumentary Overview The integument includes the cutaneous layer or skin which includes the epidermis & dermis. The accessory structures include hair, nails, and multicellular exocrine glands. Deep to the dermis, the loose connective tissue of the subcutaneous layer, or hypodermis.

Functions of the Integument Protection Excretion Temperature maintenance Nutrient Storage Vitamin D3 synthesis Sensory Detection

The Epidermis Thin skin formed by 4 layers of keratinocytes covers most of the body Thick skin covers palms of hands & soles of feet. Provides mechanical protection, prevents fluid loss, keeps out bugs

The Epidermis

Layers of the Epidermis Stratum corneum Stratum lucidum (in thick skin) Stratum granulosum Stratum spinulosum Stratum basale or germanitivum

Layers of the Epidermis

Stratum germinativum Innermost layer Forms epidermal ridges - extend into the dermis, increasing area of contact Dermal papilla extend between ridges Ridges = fingerprints; increase surface area of skin and increase friction. Unique to individuals!!

Germinative cells dominate layer These cells undergo mitosis (stem cells) Merkel cells (touch receptors) found on skin surfaces which lack hair. Melanocytes present in layer. These cells contribute to skin color.

Stratum Spinosum “spiny layer” Consists of 8-10 layers of cells Spiny appearance due to tissue prep Langerhans cells present - these cells participate in the immune response. They stimulate defense against 1) microorganisms & 2) superficial skin cancers

Stratum Granulosum “Grainy Layer” 3-5 layers of karatinocytes Cells have stopped dividing by now Make lots of keratin. - protein, waterproof

Stratum Lucidum Found only in “thick skin” Palms of hands & Soles of feet Clear layer Cells are flattened, densely packed, and filled with keratin.

Stratum Corneum Top layer 15-30 layers of keratinized cells Cells shed from this layer in large groups 15-30 days for a cell to move from s.germinativum to s. corneum. Cells remain in S. corneum approx. 2 weeks before shed or washed away. Water resistant layer, not waterproof

Skin color Interaction between epidermal pigmentation and dermal circulation Carotene & melanin important pigments Carotene = orange-yellow pigment Carotene converted to Vitamin A Melanin = brown, yellow-brown, or black pigmentation made by melanocytes

Melanocytes… Located in the stratum germinitivum Regardless of ethnic variation, the ratio of melanocytes to germinative cells ranges between 1:4 and 1:20, depending on region of the body. Variation in skin color due to synthetic activity of the melanocytes, not number Melanin protects against UV damage.

Images of Melanocytes..