Substitute for Integumentary Lab



Substitute for Integumentary Lab

PLEASE DO NOT WRITE ON THIS PAPER. Answer the questions on a separate piece of paper and RETURN THESE QUESTIONS with your answer sheet.

Use the information from the lab (on back) or in your textbook to help answer the questions.

PLEASE USE COMPLETE SENTENCES.

1. What is meant by “density of tactile receptors”?

2. (a) Which areas of your body contain densely packed receptors?

(b) Which areas contain lower concentrations of receptors?

3. Why might an injection in the upper arm hurt more than one given in the hip?

4. For what functions would a specific body area need to be more sensitive?

5. Different receptors are stimulated with a light pressure on the skin and with a strong pressure on the skin. Name the type of receptor involved with light pressure sensation.

6. In what area of the dermis are these light pressure receptors located?

7. Name the type of receptor involved with deep pressure sensation.

8. In what area of the dermis are these deep receptors located?

9. Explain what “adaptation of touch receptors” means.

10. Why would it be necessary for sensory receptors to adapt to a stimulus?

11. Pain receptors do not adapt. Why is this important?

12. What three pigments contribute to skin color?

13. If you press your hand firmly on a solid surface, what changes in the color of your skin might you observe?

14. What is the reason for this color change?

15. What sensation would you begin to experience if the pressure was continued for an extended time?

16. What is a decubitus ulcer?

17. Describe the four steps involved in the formation of decubitus ulcers.

18. Explain why your fingers turn lighter color or start to tingle or hurt when you are very cold.

19. What is another name for the cuticle?

20. What is the purpose of the cuticle?

21. You should not push back or cut your cuticles. Why not?

22. Why do the nails normally look pink?

23. What is cyanosis?

24. What CAUSES cyanosis?

25. When you smash your finger so that a bruise results under the nail, why would the bruise seem to migrate toward the distal end of the nail over the next few weeks?

Two-Point Threshold

Although humans rely heavily on the sense of vision to detect and recognize objects, the sense of touch can provide information about an object, such as surface texture, that is not easily detectable by vision. The human skin contains touch receptors that are sensitive to mechanical pressure. However, the density of receptors varies in different areas of the body. Areas that have the greatest density of tactile receptors are more sensitive and typically are found in areas of fine motor control. Areas of skin, such as the lips and fingertips, contain densely packed receptors (very close together), while insensitive areas, such as the stomach and back, contain lower concentrations of receptors (further apart).

Touch acuity (sharpness) is conventionally measured using the two-point threshold test.

Demonstrating Adaptation of Touch Receptors

In many cases, when a stimulus is applied for a prolonged period, the rate of a receptor response slows and conscious awareness of the stimulus declines or is lost until a stimulus change occurs. This phenomenon is referred to as adaptation. The touch receptors adapt particularly rapidly, which is highly desirable. Who, for instance, would want to be continually aware of the pressure of clothing on their skin? However, pain receptors do not adapt because pain is a sign of danger or something that may be harmful to the body. You would not want to lose awareness if your receptors are detecting something that would potentially damage the body.

Visualizing Changes in Skin Color

The rich dermal blood supply allows the skin to play a role in regulating body temperature. When body temperature is high, the capillary network of the dermis becomes engorged with heated blood, and body heat is allowed to radiate from the skin surface. If the environment is cool and body heat must be conserved, the dermal blood vessels constrict so that the blood bypasses the dermis temporarily. Deep pressure applied to the dermis closes blood vessels, preventing blood from flowing to the tissues. The lack of oxygen will begin to affect cells, resulting in a tingling or numb feeling. If the pressure continues for an extended period of time, the cells will begin to die.

Identifying Nail Structures

Nails, the hornlike derivatives of the epidermis, are transparent and nearly colorless, but they appear pink because of the blood supply in the underlying dermis. The exception to this is the proximal region of the thickened nail matrix which appears as a white crescent called the lunula. When someone is cyanotic due to lack of oxygen in the blood, the nail beds take on a gray or blue cast.

Nails consist of a free edge, a body, and a root. The borders of the nail are overlapped by skin folds called nail folds. The thick proximal nail fold, the eponychium, is commonly called the cuticle. This structure is responsible for sealing the edges of the nail fold to the nail, which prevents substances from entering the body. The germinal cells at the lunula are responsible for nail growth. As new cells are produced at the proximal end of the nail, they push the older cells toward the distal end of the nail. As they migrate, they become heavily keratinized and die.

Testing Tactile Localization

Tactile localization is the ability to determine which portion of the skin has been touched. The tactile receptor field of the body periphery has a corresponding “touch” field in the brain. Some body areas are well represented with touch receptors, and tactile stimuli can be localized with great accuracy, but density of touch receptors in other body areas allows only crude discrimination.

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