Chapter 6

What is the function of melanin?

Melanin provides skin color and protects against the damaging effects of ultraviolet radiation.

Merocrine Sweat Glands

Merocrine sweat glands secrete through tubes (ducts) to the skin surface, are found all over the body, and respond to elevated body temperature

What, besides body temperature regulation, are some functions of the skin?

Skin acts a protective covering houses sensory receptors, and plays a role in vitamin D production.

What are the functions of these tissues?

The Connective Tissues give the dermis toughness and elasticity. The Smooth Muscle Tissue can wrinkle the skin. Blood vessels in the dermis supply nutrients to the skin cells. Nervous Tissue includes sensory receptors.

Distinguish between the Stratum Basale and the Stratum Corneum?

The cells in the stratum basale divide and grow, whereas the cells in the stratum corneum are dead and keratinized.

Name the tissues in the outer and inner layers of the skin?

The epidermis is composed of stratified squamous epithelium. The dermis has connective tissue, smooth muscle tissue, and nervous tissue.

What is the composition of the epidermis?

The epidermis is stratified squamous epithelium and lacks blood vessels.

What are the protective functions of the epidermis?

The epidermis protects against water loss, mechanical injury, harmful chemicals, and pathogens.

What is the structure of the nail bed?

The nail bed is made up of specialized epithelial cells continuous with the epithelium of the skin.

What types of tissues make up the dermis?

The papillary layer is areolar connective tissue, and the reticular layer is dense irregular connective tissue. Blood vessels, smooth muscle tissue, and nervous tissue are found in the dermis.

Functions of the Subcutaneous Layer?

The subcutaneous layer conserves heat and has major blood vessels that supply the skin

Name the tissues in the Subcutaneous Layer beneath the skin?

The subcutaneous layer contains aerolar and adipose tissues

How do physiological factors influence skin color?

Well oxygenated blood and dilated blood vessels redden the skin. Carotenes may turn the skin yellowish. Disease also affects skin color.

How does the skin help regulate body temperature?

When body temperature rises above the set point dermal blood vessels dilate so heat escapes to the outside of the body and sweat glands produce sweat that evaporates and cools the body. When body temperature drops below the set point dermal blood vessels constrict to conserve heat and sweat glands remain inactive, also skeletal muscles may begin to contract (shivering) to produce more heat.

How does a scab slough off?

When damaged tissues are replaced with epithelial cells and fibroblasts with their collagen fibers.

What changes occur with age in the epidermis and dermis?

With age, the epidermis thins, and the dermis is less elastic showing wrinkling.

How does the body lose excess heat?

Excess body heat is lost through radiation, conduction, convection, and evaporation.

Which type of burn is most likely to leave a scar? Why?

A full-thickness (third degree) burn is most likely to scar because most of the epithelial cells have been destroyed and healing from the cells on the margins is not very effective. The fibroblasts and collagen framework are also destroyed in this type of burn.

Apocrine Sweat Glands

Apocrine sweat glands secrete through tubes (ducts) to hair follicles, are most numerous in the axillary and groin areas, and respond when a person is emotionally upset, frightened, or in pain.

What is the tissue response to inflammation?

Blood vessels dilate and fluids leak into the damaged tissues.

How is body heat produced?

Body heat is produced by cellular metabolism, particularly in the skeletal and cardiac muscle cells.

What produces goose bumps?

Contraction of the arrector pili muscles causes goose bumps.

Which environmental factors influence skin color?

Environmental factors that affect skin color include untraviolet light from the sum or sunlamps and X rays

Explain how a hair forms?

Epidermal stem cells at the base of the hair follicle divide and grow. The older cells are pushed toward the skin surface, and as they move away from the blood supply at the follicle base they die and become keratinized. These cells form the hair shaft.

How do genetic factors influence skin color?

Genes control the amount of melanin the melanocytes produce.

Why do older people have more difficulty controlling body temperature than do younger people?

Older people have difficulty controlling body temperature because the ability to shiver declines, as well as fewer deep blood vessels with a lesser ability to shunt blood toward the body's interior.

How do the skin's accessory structures change over time?

Over time less sebum is produced (drying of skin and hair), hair growth slows and whitens, nails harden, sensitivity to pain and pressure diminishes, and the ability to control body temperature falters.

What is the function of the sebaceous glands?

Sebaceous glands secrete sebum, which keeps the hair and skin soft, pliable, and waterproof.