Chapter 6 Integumentary System

Organ Two or more types of tissues grouped together that perform a specialized task. Integumentary System Skin plus accessory structures Skin is the largest organ in our body

Functions of skin include Forms protective coating Retards water loss Vitamin D synthesis Temperature control Houses sensory receptors

3 Layers of Skin Epidermis Dermis Hypodermis Subcutaneous Not part of skin

Epidermis Outermost layer of skin Stratified squamous epithelium Outermost layers are keratinized No direct blood supply – Receives nutrients by diffusion

Stratum Corneum Stratum Basale Outermost layer of epidermis Tightly packed dead cells Cells are keratinized Keratin = water insoluble protein Stratum Basale Deepest layer of epidermis Cells are nourished by dermal blood vessels Site of cell growth and division Stratum Basal contains Melanocytes

Figure 6.3 Epidermis of thick skin

Melanocytes Secrete melanin – pigment Number of melanocytes is similar in all people Darker skin from darker and larger melanin granules Albinism – mutation resulting in no melanin production

Figure 6.4a A melanocyte with melanin granules Figure 6.5 The red eyes and pale skin reflect the lack of melanin in albinism.

Dermis Deeper layer of skin Dense irregular connective tissue Contains dermal papillae Blood vessels and nerves Hair follicles Sweat glands and Sebaceous glands

Figure 6.2 Section of skin

Sweat Glands Secrete sweat onto skin surface Eccrine glands – respond to elevated temperatures Apocrine glands - anxiety, sexual arousal, and pain Sebacous glands Associated with hair follicles Secretes Sebum – oil Keeps hair and skin soft and waterproof

Figure 6.10 Illustration of sweat glands and sebaceous glands.

Hypodermis Subcutaenous layer – not part of skin Adipose Tissue, Areolar Tissue, Blood vessels Binds skin to underlying organs Adipose insulates the body

End of Chapter 6