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Integument System
Term | Definition |
---|---|
Skin consists of three major regions | epidermis, dermis, hypodermis |
Epidermis | outermost superficial region |
Dermis | middle region |
Hypodermis (superficial fascia) | deepest region |
The epidermis is composed of | keratinized stratified squamous epithelium, consisting of four distinct cell types and four or five layers |
Cell types include | keratinocytes, melanocytes, Merkel cells, and Langerhans' cells |
Outer portion of the skin is | exposed to the external environment and functions in protection |
Keratinocytes | produce the fibrous protein keratin |
Melanocytes | produce the brown pigment melanin |
Langerhans' cells | epidermal macrophages that help activate the immune systems |
Merkel cells | function as touch receptors in association with sensory nerve endings |
Layers of the epidermis | Stratum Basale, Stratum Spinosum, Stratum Granulosum, Stratum Lucidum, and Stratum Corneum |
Stratum Basale | Basal layer |
Deepest epidermal layer | firmly attached to the dermis |
Consists of | a single row of the youngest keratinocytes |
Cells undergo | rapid division, hence its alternate name, stratum germinativum |
Stratum Spinosum | Prickly layer |
Cells contain | a weblike system of of intermediate filaments attached to desmosomes |
Melanin granules and Langerhans' cells are | abundant in this layer |
Stratum Granulosum | Granular layer |