Chapter 5 final review

15. What accounts for the ability of the dermis to undergo repeated stretching?

The presence of elastic fibers and the flexibility and resilience of skin turgor allow the dermis to undergo repeated cycles of stretching and recoiling (returning to its original shape).

29. What term describes the combination of fibrin clots, fibroblast, and the extensive network of capillaries in healing tissue?

The combination of fibrin clots, fibroblasts, and the extensive network of capillaries in tissue that is healing is called granulation tissue.

13. Describe the location of the dermis.

The dermis (a connective tissue layer) lies between the epidermis and the hypodermis

17. Describe the hypodermis.

The hypodermis is a layer of loose connective tissue (areolar tissue) and adipose tissue below (deep to) the dermis. It is also called the subcutaneous layer or superficial fascia. The hypodermis is not considered a part of the integument, but it is important in stabilizing the position of the skin in relation to underlying tissues.

1. Identify the layers of the epidermis.

stratum basale stratum spinosum stratum granulosum stratum lucidum stratum corneum

2. Dandruff is caused by excessive shedding of cells from the outer layer of skin in the scalp. So dandruff is composed of cells from which epidermal layer?

stratum corneum

3. A splinter that penetrates to the third layer of the epidermis of the palm is lodged in which layer?

stratum granulosum

25. Which type of skin gland is most affected by the hormonal changes that occur during puberty?

Apocrine sweat glands enlarge and increase secretory activity in response to the increase in sex hormones that occurs at puberty.

Older individuals do not tolerate the summer heat as well as they did when they were young, and they are more prone to heat-related illness. What accounts for these changes?

As a person ages, the blood supply to the dermis decreases and merocrine sweat glands become less active These changes make it more difficult for older individuals to cool themselves in hot weather.

11. Name the sources of epidermal growth factor in the body.

Salivary glands and duodenal glands (glands of the duodenum) produce epidermal growth factor (EGF).

5. Some criminals sand the tips of tier fingers so as not to leave recognizable fingerprints. Would this practice permanently remove fingerprints? Why or why not?

Sanding the tips of the fingers will not permanently remove fingerprints. The ridges of the fingerprints are formed in layers of the skin that are constantly regenerated so these ridges will eventually reappear. The pattern of the ridges is determined by the arrangement of tissue in the dermis, which is not affected by sanding.

19. Describe a typical strand of hair.

...a keratinous strand produced by epithelial cells of the hair follicle.

4. Why does taking a bath cause wrinkly fingertips and toes?

...due to the constriction of blood vessels in the underlying skin, which causes the skin to shrink. This effect is controlled by the autonomic nervous system, a division of the nervous system that acts outside our awareness.

18. Identify several functions of subcutaneous fat.

...provides insulation to help reduce heat loss, serves as an energy reserve, and acts as a shock absorber for the body.

20. What happens when the arrector pili muscle contracts?

...pulls the hair follicle erect. The result is know as "goose bumps".

In some cultures, women must be covered completely, except for their eyes, when they go out in public. Explain why these women may develop bone problems later in life.

Cholecalciferol (vitamin D) is needed to form strong bones and teeth. When the body surface is covered, UV light cannot penetrate to the stratum basale in the skin to begin vitamin D3 production, resulting in fragile bones.

24. Deodorants are used to mask the effects of secretions from which type of skin gland?

Deodorants are used to mask the odor of apocrine sweat gland secretions, which contain several kinds of organic compounds. Some of these compounds have an odor, and others produce an odor when metabolized by skin bacteria.

12. Identify some roles of epidermal growth factor pertaining to the epidermis.

Epidermal growth factor (EGF) promotes the divisions of basal cells in the stratum basale and stratum spinosum, accelerates the production of keratin in differentiating keratinocytes, stimulates epidermal development and epidermal repair after injury, and stimulates synthetic activity and secretion by epithelial glands.

21. Once a burn on the forearm that destroys the epidermis and extensive areas of the deep dermis heals, will hair grow again in the affected area?

Even though hair is a derivative of the epidermis, the hair follicles are in the dermis. When the epidermis and deep dermis are destroyed, new hair will not grow.

14. Where are the capillaries and sensory neurons that supply the epidermis located?

The capillaries and sensory neurons that supply the epidermis are located in the papillary layer of the dermis.

9. Explain the relationship between sunlight exposure and vitamin D3 synthesis.

In the presence of ultraviolet radiation in sunlight, epidermal cells in the stratum spinosum and stratum basale convert a cholesterol-related steroid into cholecalciferol, or vitamin D3.

26. What substance makes fingernails hard?

Keratin is the substance that gives fingernails their strength.

28. Where does nail growth occur?

Nail growth occurs at the nail root, an epidermal fold that is not visible from the surface.

23. What are the functions of sebaceous secretions?

Sebaceous secretions (called sebum) lubricate and protect the keratin of the hair shaft, lubricate and condition the surrounding skin, and inhibit the growth of bacteria.

30. Why can skin regenerate effectively even after considerable damage?

Skin can regenerate effectively even after considerable damage because stem cells persist in both the epithelial and connective tissue components of skin. When injury occurs, cells of the stratum basale replace epithelial cells, and mesenchymal cells replace cells lost from the dermis.

27. What term is used to describe the thickened stratum corneum underlying the free edge of a nail?

The area of thickened stratum corneum under the free edge of a nail is called the hypomychium.

16. List the two terms for the tissue that connects the dermis to underlying tissues.

The tissue that connects the dermis to underlying tissues is the hypodermis or subcutaneous layer.

22. Identify two types of exocrine glands found in the skin.

Two types of exocrine glands found in the skin are sebaceous (oil) glands and sweat glands.

7. Why does exposure to sunlight darken skin?

When exposed to the ultraviolet radiation in sunlight, melanocytes in the epidermis and dermis synthesize the pigment melanin, darkening the skin.

8. Why does the skin of a fair-skinned person appear red during exercise in hot weather?

When skin gets warm, arriving oxygenated blood is diverted to the superficial dermis or the purpose of eliminating heat. The oxygenated blood gives a reddish coloration to the skin.

Why does hair turn white or gray with age?

With advancing age, melanocyte activity decreases, leading to gray or white hair.

6. Name the two major pigments in the epidermis.

carotene (orange-yellow) melanin - red-yellow (pheomelanin) to brown-black (eumelanin)