malinin Flashcards
Melanin:
Melanin is the primary pigment responsible for skin color. It comes in different shades, including yellow, reddish-brown, and black.
Melanin production is stimulated by sunlight. When the skin is exposed to UV rays, melanocytes (specialized skin cells in the epidermis) produce more melanin as a protective response.
Melanin is stored in membrane-bound granules called melanosomes.
These granules travel to the spidery arms of melanocytes and are transferred to nearby keratinocytes (the main cell type in the epidermis).
In keratinocytes, the melanin forms a protective “umbrella” over the nuclei (the “sunny” side) to shield the DNA from UV damage.
People who produce a lot of melanin typically have darker skin (brown tones), while those with less melanin tend to have lighter skin.
Carotene:
Carotene is an orange-yellow pigment found in foods like carrots, sweet potatoes, and leafy green vegetables.
When you consume large amounts of carotene-rich foods, it can accumulate in the skin, particularly in the stratum corneum (the outermost layer of the epidermis) and in subcutaneous tissue. This gives the skin a yellow-orange tint.
While carotene can influence skin color, it is generally not as prominent as melanin in most people.
Hemoglobin:
Hemoglobin is the protein in red blood cells that carries oxygen.
In people with light skin, the crimson color of oxygen-rich hemoglobin in the dermal blood vessels can give the skin a rosy glow or a pinkish hue, as it shines through the thin layers of skin.
This effect is most noticeable in fair-skinned individuals because the melanin content is lower, allowing more of the blood’s color to be visible.
Homeostatic Imbalance:
Homeostatic imbalance refers to any disruption in the normal functioning of the body, in this case, related to skin pigmentation. An example might be:
Excessive sun exposure can damage skin cells, leading to skin cancer.
Albinism is a condition where individuals lack the ability to produce melanin, resulting in very light skin, hair, and eyes.
Carotenemia is a condition where excess carotene in the blood causes the skin to develop a yellow-orange tint, often seen in individuals who consume large amounts of carotene-rich foods.
emotions also influence skin colour
Redness, or erythema (er″ĭ-the′mah). Reddened skin may indicate embarrassment (blushing), fever, hypertension, inflammation, or allergy.
Pallor, or blanching. Under certain types of emotional stress (fear, anger, and others), some people become pale. Pale skin may also signify anemia, low blood pressure, or impaired blood flow into the area.
Jaundice (jon′dis), or a yellow cast. An abnormal yellow skin tone usually signifies a liver disorder in which excess bile pigments accumulate in the blood, circulate throughout the body, and become deposited in body tissues.
Bruises. The black-and-blue marks of bruising reveal sites where blood has escaped from the circulation and has clotted in the tissue spaces. Such clotted blood masses are called hematomas. An unusual tendency to bruise may signify a deficiency of vitamin C in the diet or hemophilia (bleeder’s disease).
Cutaneous Glands
The cutaneous glands are all exocrine glands that release their secretions to the skin surface via ducts. They fall into two groups: sebaceous glands and sweat glands. As these glands are formed by the cells of the stratum basale, they push into the deeper skin regions and ultimately reside almost entirely in the dermis.
Sebaceous (Oil) Glands
The sebaceous (se-ba′shus) glands, or oil glands, are found all over the skin, except on the palms of the hands and the soles of the feet. Their ducts usually empty into a hair follicle (Figure 4.6a), but some open directly onto the skin surface.
sebum (
is a mixture of oily substances and fragmented cells. Sebum is a lubricant that keeps the skin soft and moist and prevents the hair from becoming brittle. Sebum also contains chemicals that kill bacteria, so it is important in preventing bacterial infection of the skin. The sebaceous glands become very active when androgens (male sex hormones) are produced in increased amounts (in both sexes) during adolescence. Thus, the skin tends to become oilier during this period of life.
Sweat Gland
Sweat glands, also called sudoriferous (su″do-rif′er-us; sudor = sweat) glands, are widely distributed in the skin. Their number is staggering—more than 2.5 million per person. There are two types of sweat glands, eccrine and apocrine.
The eccrine
The eccrine (ek′rin) glands are far more numerous and are found all over the body. They produce sweat, a clear secretion that is primarily water plus some salts (sodium chloride), vitamin C, traces of metabolic wastes (ammonia, urea, uric acid), and lactic acid (a chemical that accumulates during vigorous muscle activity). Sweat is acidic (pH from 4 to 6), a characteristic that inhibits the growth of certain bacteria, which are always present on the skin surface. Typically, sweat reaches the skin surface via a duct that opens externally as a funnel-shaped sweat pore (Figure 4.6b). Notice, however, that the facial “pores” commonly referred to when we talk about our complexion are the external outlets of hair follicles where sebaceous ducts empty, not these sweat pores.
Apocrine
ap′o-krin) glands are largely confined to the axillary (armpit) and genital areas of the body. They are usually larger than eccrine glands, and their ducts empty into hair follicles. Their secretion contains fatty acids and proteins in addition to all the substances present in eccrine sweat; consequently, it may have a milky or yellowish color. The secretion is odorless, but when bacteria that live on the skin use its proteins and fats as a source of nutrients, it can take on a musky, unpleasant odor.
Apocrine glands begin to function during puberty under the influence of androgens. Although they produce their secretions almost continuously, apocrine glands play a minimal role in thermoregulation. Their precise function is not yet known, but they are activated by nerve fibers during pain and stress and during sexual arousal.
