The integumentary system includes the skin and accessory structures. The skin is the largest organ of the body and has several important functions, including forming a protective barrier, regulating temperature and water loss, synthesizing vitamin D, and detecting sensory stimuli. The skin is composed of two main layers - the epidermis and dermis. The epidermis is the outermost layer and contains stratified squamous epithelium and five layers including the stratum corneum and stratum basale. The dermis lies deeper and contains dense connective tissue, blood vessels, nerves, hair follicles, and glands.

1. Chapter 6
Integumentary System

2. Organ
An organ consists of two or more types of tissues
grouped together that perform a specialized task.
Integumentary System
Includes the skin plus accessory structures
Skin is the largest organ in our body

3. Functions of skin include
1. Forms protective coating
2. Retards water loss
3. Vitamin D synthesis
4. Temperature control
5. Houses sensory receptors

4. The skin is composed of 2 layers
1. Epidermis
2. Dermis
The subcutaneous layer
(hypodermis) lies beneath the skin,
but is not considered part of the
skin.

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

6. There are five (5) layers of the epidermis:
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale

7. Layers of the epidermis
Stratum corneum
Is the outermost layer of epidermis
Composed of 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

8. 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

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

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

11. Figure 6.2 Section of skin

12. Sweat Glands - secrete sweat onto surface of the skin
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

13. Subcutaneous layer (often called hypodermis)
Subcutaneous layer – not part of skin
Comoposed of adipose tissue, areolar tissue, and blood vessels
The subcutaneous layer binds skin to underlying organs
Adipose insulates the body

14. End of Chapter 6