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 • 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