Anatomy and Physiology Fisher

Anatomy and Physiology Fisher

Chapter 6: Skin and Integumentary System

Critical Thinking Questions, p. 124 #’s 1-7

1. Everyone’s skin contains about the same number of melanocytes even though people are of many different colors. How is this possible?

Melanocytes produce differing amounts of melanin and different sized granules of melanin. This is based on both genetics and environmental conditions. The amount of melanin and its distribution determine skin color. Melanin can travel via cytoplasmic extensions through a process called cytocrine secretion. This carries melanin to more superficial layers of the epidermis. (p. 116)

2. Why would collagen and elastin added to skin creams be unlikely to penetrate the skin—as some advertisements imply they do?

These fibers are too large to penetrate the epidermis—which is made up of various strata, the outermost layer being keratinized to protect against water loss and infection. In order to change the skin they would need to be present in the dermis, and topically applied they will not reach the dermis. (P. 114)

3. A severe form of the inherited illness epidermolysis bullosa causes extreme blistering of the skin. The person lacks a protein called laminin, which normally attaches the dermis to the epidermis. Explain how lack of this protein disrupts the skin’s structure.

Without the protein that binds the epidermis to the dermis (basement membrane) the structure of the skin and therefore the skin’s integrity is compromised. This means the epidermis may not completely cover the dermis in places, providing gaps in this coverage. As the dermis contains vessels that supply the epidermis, and the deep layers of the epidermis do not keratinize, the protection is incomplete and blistering occurs—there could be potential bleeding, loss of moisture in general from the skin, and avenues for infection from these openings. If the epidermis is damaged for any reason, because the blood source is in the dermis, then healing would be slow. More blood and lymph may attempt to get to the site, but there may be difficulties with this. This may cause more fluid to be expelled, slower healing may also encourage further infection.

4. How is skin peeling after a severe sunburn protective?

The damaged cells die and are shed, for new epidermal cells to take their place. This lowers the risk of DNA mutations that can cause cancer. (pp. 119, 121)

5. What special problems would result from the loss of 50% of a person’s functional skin surface? How might this person’s environment be modified to compensate partially for such a loss?

The loss of fluids is significant, the ability of the person to protect against the loss of fluids in the future is also significant. A person will generally need to have skin grafted or a skin substitute applied in order to survive. Oil and sweat may not be produced or produced as well in the effected area—so cooling the environment and moisturizing may be of critical import to the individual in the future, as well.

6. A premature infant typically lacks subcutaneous adipose tissue. Also the surface area of an infant’s small body is relatively large compared to its volume. How do you think these factors affect the ability of an infant to regulate its body temperature?

The infant will have trouble retaining body heat, due to the lack of subcutaneous fat and large surface area. The increased surface area allows heat to dissipate quickly from the body. IN addition infants have higher heart rates and blood moves quickly throuout.

7. Which of the following would result in the more rapid absorption of a drug: a subcutaneous injection or an intradermal injection? Why?

Subcutaneous to get to the blood vessels quicker and travel throughout the body.

1 modified 11/10/2014