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