So What Does The Skin Do?

32.7 Vertebrate Skin— Example of an Organ System Skin is the body’s interface with the environment Sensory receptors, barrier against pathogens, internal temperature control, water conservation Vertebrate skin is made up of all four tissue types arranged in two layers: Outer epidermis contain keratinocytes Deeper dermis contains nerves, blood and lymph vessels, hair follicles and glands

Epidermis – epithelial tissue a. stratum germinativum – wavy ridges extend from dermis, stem cells regenerate skin takes ~ 14d - as cells move outward they gain keratin   b. stratum corneum – dead outer layer (~ 14 d) Skin Color – melanin & blood supply.

outer flattened epidermal cells cells being flattened Figure 32.13 (a) Skin structure. (b) Section through human skin. (c) Structure of a hair. It arises from a hair follicle derived from epidermal cells that have sunk into the dermis. Figure It Out: How many polypeptide chains are in a keratin macrofibril? Answer: Three dividing cells dermis Fig. 32-13b, p. 548

Dermis – contains accessory structures a. Hair papilla at base of follicle adds keratin - contains blood vessels and nerves (sensation) - arrector pili makes hair stand on end   b. Sebaceous glands – sebum lubricates hair & inhibits bacteria. Activated at puberty. - May clog & form acne c. Sweat glands – secretes water, salt & substances that produce body odor

hair epidermis dermis hypodermis sensory neuron oil gland Figure 32.13 (a) Skin structure. (b) Section through human skin. (c) Structure of a hair. It arises from a hair follicle derived from epidermal cells that have sunk into the dermis. Figure It Out: How many polypeptide chains are in a keratin macrofibril? Answer: Three hypodermis sensory neuron oil gland hair follicle sweat gland blood vessels smooth muscle Fig. 32-13a, p. 548

keratin polypeptide chain hair’s cuticle one hair cell keratin polypeptide chain keratin macrofibril Figure 32.13 (a) Skin structure. (b) Section through human skin. (c) Structure of a hair. It arises from a hair follicle derived from epidermal cells that have sunk into the dermis. Figure It Out: How many polypeptide chains are in a keratin macrofibril? Answer: Three Fig. 32-13c, p. 548

Sunlight and Human Skin Melanocytes in skin make a brown pigment (melanin) which affects skin color and tanning Melanin protects against UV radiation A little UV promotes vitamin D production A lot of UV damages DNA and promotes cancer

Nails – can be used as an indicator for circulation. - WHAT IS CLUBBING?

32.8 Farming Skin Commercially grown skin substitutes are already in use for treatment of chronic wounds Skin may be a source of stem cells that could be used to grow other organs

http://apbrwww5.apsu.edu/thompsonj/Anatomy%20&%20Physiology/2010/2010%20Exam%20Reviews/Exam%202%20Review/Ch%205%20Burns.htm

32.7-32.8 Key Concepts A Closer Look at Skin Skin is an example of an organ system It includes epithelial layers, connective tissue, adipose tissue, glands, blood vessels, and sensory receptors It helps protect the body, conserve water, control temperature, excrete wastes, and detect external stimuli