Skin Color

Three pigments are most responsibile for normal skin colors:

1. Hemoglobin, the red pigment carried in the dermal blood vessels, along with the white color of the dermal collagen fibers, produces the flesh tones

9fasc = band

Skin Color Physiology Pictures
Figure 6.5 Distribution of Subcutaneous Fat in Males and Females.

typical of Caucasian skin. The skin is redder in places such as the lips, where blood capillaries come closer to the surface and the hemoglobin shows through more vividly.

  1. Melanin11 in the stratum basale and stratum spinosum produces a variety of brown, black, tan, yellowish, and reddish hues (fig. 6.6). The amount of melanin in the skin is determined by a combination of heredity and light exposure. Ultraviolet (UV) radiation from the sun stimulates melanin synthesis and darkens the skin. A suntan fades as melanized keratinocytes migrate to the surface and exfoliate. The amount of melanin varies substantially from place to place on the body. It is relatively concentrated in freckles and moles, on the dorsal surfaces of the hands and feet as compared to the palms and soles, in the nipple and surrounding area (areola) of the breast, around the anus, in the scrotum and penis, and on the lateral surface of the labia majora (female genital folds). The contrast between heavily melanized and lightly melanized regions of the skin is more pronounced in some races than in others, but it exists to some extent in nearly everyone.
  2. Carotene12 is a yellow pigment acquired from egg yolks and yellow and orange vegetables. Depending on the diet, it can become concentrated to various degrees in the stratum corneum and subcutaneous fat. It is often most conspicuous in skin of the heel and in "corns" or calluses of the feet because this is where the stratum corneum is thickest.

11 melan = black 12carot = carrot

Saladin: Anatomy & I 6. The Integumentary I Text I I © The McGraw-Hill

Physiology: The Unity of System Companies, 2003 Form and Function, Third Edition

Chapter 6 The Integumentary System 197

Table 6.1 Stratification of the Skin and Hypodermis

Layer Description

Table 6.1 Stratification of the Skin and Hypodermis

Layer Description

Epidermis

Stratified squamous epithelium

Stratum corneum

Dead, keratinized cells of the skin surface

Stratum lucidum

Clear, featureless, narrow zone seen only in thick skin

Stratum granulosum

Two to five layers of cells with dark-staining keratohyalin granules; scanty in thin skin

Stratum spinosum

Many layers of keratinocytes, typically shrunken in fixed tissues but attached to each other by desmosomes, which give

them a spiny look; progressively flattened the farther they are from the dermis. Dendritic cells occur here but are not

visible in routinely stained preparations.

Stratum basale

Single layer of cuboidal to columnar cells resting on basement membrane; site of most mitosis; consists of keratinocytes,

melanocytes, and tactile cells, but these are not distinguishable with routine stains. Melanin is conspicuous in

keratinocytes of this layer in black to brown skin.

Dermis

Fibrous connective tissue, richly endowed with blood vessels and nerve endings. Sweat glands and hair follicles originate

here and in hypodermis.

Papillary layer

Superficial one-fifth of dermis; composed of areolar tissue; often extends upward as dermal papillae

Reticular layer

Deeper four-fifths of dermis; dense irregular connective tissue

Hypodermis

Areolar or adipose tissue between skin and muscle

Skin Color Physiology Pictures

Figure 6.6 Variations in Skin Pigmentation. (a) Keratinocytes in and near the stratum basale have heavy deposits of melanin in dark skin.

(b) Light skin shows little to no visible melanin in the basal keratinocytes.

Which of the four types of epidermal cells are the melanized cells in figure a?

Figure 6.6 Variations in Skin Pigmentation. (a) Keratinocytes in and near the stratum basale have heavy deposits of melanin in dark skin.

(b) Light skin shows little to no visible melanin in the basal keratinocytes.

Which of the four types of epidermal cells are the melanized cells in figure a?

The skin may also exhibit abnormal colors of diagnostic value:

• Cyanosis13 is blueness of the skin resulting from a deficiency of oxygen in the circulating blood. Oxygen deficiency turns the hemoglobin a reddish violet color.

13cyan = blue + osis = condition

It can result from conditions that prevent the blood from picking up a normal load of oxygen in the lungs, such as airway obstructions in drowning and choking, lung diseases such as emphysema, or respiratory arrest. Cyanosis also occurs in situations such as cold weather and cardiac arrest, when blood flows so slowly through the skin that most of its oxygen is extracted faster than freshly oxygenated blood arrives.

Saladin: Anatomy & 6. The Integumentary Text © The McGraw-Hill

Physiology: The Unity of System Companies, 2003

Form and Function, Third Edition

198 Part Two Support and Movement

  • Erythema14 (ERR-ih-THEE-muh) is abnormal redness of the skin. It occurs in such situations as exercise, hot weather, sunburns, anger, and embarrassment. Erythema is caused by increased blood flow in dilated cutaneous blood vessels or by dermal pooling of red blood cells that have escaped from abnormally permeable capillaries.
  • Jaundice15 is a yellowing of the skin and whites of the eyes resulting from high levels of bilirubin in the blood. Bilirubin is produced by the breakdown of free hemoglobin and disposed of by the liver. Jaundice may therefore occur when there is a rapid rate of erythrocyte destruction; when diseases such as cancer, hepatitis, and cirrhosis interfere with liver function; and in premature infants, where the liver is not well enough developed to dispose of bilirubin efficiently.
  • Bronzing is a golden-brown skin color that results from Addison disease, a deficiency of glucocorticoid hormones from the adrenal cortex. John F. Kennedy had Addison disease and bronzing of the skin, which many people mistook for a suntan.
  • Pallor is a pale or ashen color that occurs when there is so little blood flow through the skin that the white color of the dermal collagen shows through. It can result from emotional stress, low blood pressure, circulatory shock, cold temperatures, or severe anemia.
  • Albinism16 is a genetic lack of melanin that results in white hair, pale skin, and pink eyes. Melanin is synthesized from the amino acid tyrosine by the enzyme tyrosinase. People with albinism have inherited a recessive, nonfunctional tyrosinase allele from both parents.
  • A hematoma,17 or bruise, is a mass of clotted blood showing through the skin. It is usually due to accidental trauma (blows to the skin), but it may indicate hemophilia, other metabolic or nutritional disorders, or physical abuse.

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Responses

  • awet
    What pigment is attributed to the reddish color of the skin of the lips hemoglobin?
    1 year ago

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