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

2. 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
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3. 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.

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

5. 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

6. The Epidermis

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

8. Layers of the Epidermis

9. 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!!

10. 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.

11. 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

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

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

14. 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

15. 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

16. 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.

17. Images of Melanocytes..