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

painSebacous 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