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• Hypodermis

• Subcutaneous

• Not part of skin

Epidermis

• Outermost layer of skin

• Stratified squamous epithelium

• Outermost layers are keratinized• 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 • 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• 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• Binds skin to underlying organs

• Adipose insulates the body

End of Chapter 6