Monday, January 6, 2014

Chapter 9: Physiology and Histology of the Skin

1. The six functions of the skin are protection, sensation, heat regulation, excretion, secretion, and absorption.

2. The barrier function is the protective barrier of the epidermis. The corneum and intercellular cement protect the surface from irritation and dehydration.

3. Sebum is important because it provides protection for the epidermis from external factors and lubricates both the skin and hair.

4. The skin protects itself using the acid mantle, self-healing, and melanin.

The acid mantle is the protective barrier made up of sebum, lipids, sweat, and water that form a hydrolipidic film to protect the skin from drying out and from exposure to external factors.

The skin can heal itself through a hyper production of cells and blood clotting.

The skin also produces melanin, the pigment that protects us from the sun.

5. Hair follicles, sweat glands, and blood vessels help with heat regulation in the skin. Hair follicles and sweat glands dissipate heat and cause evaporation to help cool the body. Blood vessel dilation assists in cooling the body. Constriction of the blood vessels and decreasing blood flow protects the body from cold.   The body's fat layers also help to insulate and warm the body.

6. The skin is comprised of two parts.

The epidermis is the outermost layer that contains five layers of the skin.

The dermis is the live layer of connective tissues below the epidermis. The dermis has two layers.

7.  The layers of the epidermis are the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum germinativum.

8. The layers of the dermis are the papillary layer and the reticular layer.

9. Collagen is a fibrous, connective tissue made from protein that is found in the reticular layer of the dermis. Collagen gives skin its firmness. Topically it is a large, long-chain molecular protein that lies on the top of the skin and binds water. Derived from the placentas of cows or other sources.

10. Elasticity is important to the skin because it keeps the skin from sagging, wrinkling, and aging.

11. Melanocytes are cells that produce pigment granules in the basal layer.

12. Skin gets its nourishment from blood and lymph.

Blood supplies nutrients and oxygen to the skin.

Lymph bathes the skin cells, removes the toxins and cellular waste.

Topical products can also nourish the epidermis. 

13. The three types of nerve fibers are:
Motor nerve fibers- stimulate muscles such as the at rector pili muscles.
Sensory nerve fibers- send messages to the brain to react to heat, cold, pain, pressure, and touch.
Secretory nerve fibers- dispersed to sweat and oil glands. They regulate excretion from the sweat glands and control sebum output to the surface of the skin.

14. The body replaces billions of cells each day.

15. Skin gets its color from the pigment produced by melanocytes.  Melanocytes are cells that produce pigment granules called melanosomes. Melanosomes produce a complex protein called Melanin, which determines hair and skin color.

16. The two main glands associated with the skin are the Sebaceous glands (connected the the hair follicles and produce oil) and the Sudoriferous glands (regulate body temperature and eliminate waste products by excreting sweat).

17. The two types of sweat glands are the apocrine glands (attached to hair follicles under the arms and in the genital area) and the eccrine glands (all over the body and more active during physical activity). 

18. Free radicals are oxygen atoms or molecules with unpaired electrons that cause oxidation. They steal electrons from other molecules, which damages the other molecules.

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