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 tissuea. 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.

Fig. 32-13b, p. 548

outer flattened epidermal cells

cells being flattened

dividing cells

dermis

Dermis – contains accessory structuresa. 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

Fig. 32-13a, p. 548

hair

epidermis

dermis

hypodermis

sensory neuronoil gland

hair follicle sweat gland

blood vessels smooth muscle

Fig. 32-13c, p. 548

hair’s cuticle

one hair cell

keratin macrofibril

keratin polypeptide chain

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