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The Integumentary System Chapter 5

The Integumentary System Chapter 5. The Skin. epithelial and connective tissues working together the largest organ of the body 1.5 - 2 square meters 4 - 5 kg variable thickness: 0.5 mm to 4 mm. The Architecture of the Skin. 2 main parts:

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The Integumentary System Chapter 5

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  1. The Integumentary System Chapter 5

  2. The Skin • epithelial and connective tissues working together • the largest organ of the body • 1.5 - 2 square meters • 4 - 5 kg • variable thickness: 0.5 mm to 4 mm

  3. The Architecture of the Skin 2 main parts: • Epidermis – keratinized stratified squamous epithelium • Dermis – areolar & dense irregular connective tissues Beneath the dermis: • Hypodermis (the subcutaneous layer) – separates skin from muscle; contains areolar and adipose tissues

  4. A Bigger Picture

  5. Skin’s Many Functions • regulation of body temperature • protection – a physical barrier & water conservation • sensation – due to sensory nerve endings • excretion – sweat • immunity – epidermis contains phagocytes • synthesis of vitamin D – for calcium absorption

  6. The Epidermis 4 cell types: • Keratinocytes filled with protein keratin; waterproof barrier • Melanocytes produce pigment melanin • Langerhans cells phagocytes (function in immunity); easily damaged by UV light • Merkel cells detect touch sensations

  7. Epidermal Cell Layers • Stratum basale • a single layer; mitosis pushes the other layers to the top; Merkel cells & melanocytes • Stratum spinosum • 8 to 10 layers of closely packed cells; Langerhans’ cells • Stratum granulosum • 3-5 layers of flattened non-dividing cells; produce large amount of keratin; nuclei & organelles disintegrate

  8. Epidermal Layers Cont. • Stratum lucidum • only in thick skin • 3-5 layers of clear, flat dead cells with keratin • Stratum corneum • 25-30 layers of flattened, dead, keratin-filled cells • continuously shed and replaced It takes 2-4 weeks for each cell to move from the stratum basale to stratum corneum

  9. Epidermal Histology • Stratum Corneum • Stratum Granulosum • Stratum Spinosum • Stratum Basale

  10. Skin Pigments • Hemoglobin – red, carries oxygen in red blood cells • Carotene – yellow/orange,converted to vitamin A, used in the synthesis of vision pigments • Melanin – yellow/red or brown/black

  11. Melanin Cont. • The number of melanocytes is similar in all races – but the amount of melanin produced varies • The UV ↑ production of melanin; melanin protects the body against UV radiation by absorbing UV • Albinism - inability to produce melanin; genetic

  12. Practice – Be able to complete by Wednesday 

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