A&P Chapter 5 Integumentary System
Which strata have live cells, and which strata have dead cells?
**stratum corneum: the most superficial, stratum of the epidermis. This stratum is composed of 25 or more layers of dead, overlapping squamous cells joined by desmosomes. Eventually, the desmosomes break apart, and the cells are shed from the surface of the skin. Excessive shedding of the stratum corneum of the scalp results in dandruff. **Stratum lucidum: Three to five layers of dead cells; appears transparent; present in thick skin, absent in most thin skin. **Stratum granulosum Two to five layers of flattened, diamond-shaped cells **Stratum spinosum A total of 8-10 layers of many-sided cells **Stratum basale Deepest stratum of the epidermis; single layer of cuboidal or columnar cells; basement membrane of the epidermis attaches to the dermis
When and where are lanugo, vellus, and terminal hairs found in the skin?
--By the fifth or sixth month of fetal development, delicate, unpigmented hair called lanugo (lă-noo′gō) has developed and covered the fetus --Near the time of birth, long, coarse, and pigmented hairs called terminal hairs replace the lanugo of the scalp, eyelids, and eyebrows. --Vellus hairs, which are short, fine, and usually unpigmented, replace the lanugo on the rest of the body. --
What are the functions of vitamin D?
--Vitamin D functions as a hormone involved in the regulation of calcium homeostasis. --Its primary role is to stimulate the uptake of calcium and phosphate from the intestines. Adequate levels of these minerals are necessary for normal bone metabolism (see chapter 6), and calcium is required for normal nerve and muscle function
How do carotene, blood flow, oxygen content, and collagen affect skin color?
1. Erythema (er-ĭ-thē′mă) is a condition in which the skin turns a reddish hue when the amount of blood flowing through the skin increases. An inflammatory response (see chapter 4) stimulated by infection, sunburn, allergic reactions, insect bites, or other causes can produce erythema, as can exposure to the cold and blushing or flushing when angry or hot 2. A decrease in blood flow, as occurs in shock, can make the skin appear pale, and a decrease in the blood oxygen content produces cyanosis (sī-ă-nō′sis), a bluish skin color 3. Carotene (kar′ō-tēn) is a yellow pigment found in plants, such as carrots and corn. Humans normally ingest carotene and use it as a source of vitamin A. Carotene is lipid-soluble and, when large amounts of carotene are consumed, the excess accumulates in the stratum corneum and in adipocytes of the dermis and subcutaneous tissue, causing the skin to develop a yellowish tint. The yellowish tint slowly disappears once carotene intake is reduced. 4.light reflected off dark pigment in the dermis or subcutaneous tissue can be scattered by collagen fibers of the dermis to produce a blue color. The same effect produces the blue color of the sky as light is reflected from dust particles in the air. The deeper within the dermis or subcutaneous tissue any dark pigment is located, the bluer the pigment appears because of the light-scattering effect of the overlying tissue. This effect causes the blue color of tattoos, bruises, and some superficial blood vessels.
From deepest to most superficial, name and describe the five strata of the epidermis.
1. Stratum Basale 2. Stratim Spinosum 3. Stratum Granulosum 4. Stratum lucidum 5.Stratum corneum 5.
In what ways does the skin provide protection?
1. The skin protects underlying structures from mechanical damage. 2. The skin prevents microorganisms and other foreign substances from entering the body. 3. Melanin absorbs ultraviolet light and protects underlying structures from its damaging effects. 4. The hair on the head acts as a heat insulator and protects against ultraviolet light and abrasion. The eyebrows keep sweat out of the eyes, the eyelashes protect the eyes from foreign objects, and hair in the nose and ears prevents dust and other materials from entering 5. Nails protect the ends of the fingers and toes from damage and can be used in defense. 6. The intact skin plays an important role in reducing water loss because its lipids act as a barrier to the diffusion of water.
Define the different categories of burns. How is repair accomplished after each type?
A burn is injury to a tissue caused by heat, cold, friction, chemicals, electricity, or radiation. --Partial-thickness burns are subdivided into first- and second-degree burns. First-degree burns involve only the epidermis and may result in redness, pain, and slight edema (swelling). They can be caused by sunburn or brief exposure to hot or cold objects, and they heal in a week or so without scarring. Second-degree burns damage the epidermis and dermis. Minimal dermal damage causes redness, pain, edema, and blisters. Healing takes approximately 2 weeks, and no scarring results. However, if the burn goes deep into the dermis, the wound appears red, tan, or white; may take several months to heal; and might scar. In all second-degree burns, the epidermis regenerates from epithelial tissue in hair follicles and sweat glands, as well as from the edges of the wound. Full-thickness burns are also called third-degree burns. The epidermis and dermis are completely destroyed, and deeper tissue may be involved. Third-degree burns are often surrounded by first- and second-degree burns. Although the areas that have first- and second-degree burns are painful, the region of third-degree burn is usually painless because the sensory receptors have been destroyed
Which glands are involved with producing body odor? Where are they located?
Apocrine (ap′ō-krin) sweat glands are simple, coiled, tubular glands that usually open into hair follicles superficial to the opening of the sebaceous glands . Apocrine sweat glands are found in the axillae and genitalia (scrotum and labia majora) and around the anus. Unlike eccrine sweat glands, apocrine sweat glands do not help regulate temperature in humans. Apocrine sweat glands become active at puberty as a result of sex hormones. Their secretions contain organic substances, such as 3-methyl-2-hexenoic acid, that are essentially odorless when first released but are quickly metabolized by bacteria to cause what is commonly known as body odor. Many mammals use scent as a means of communication, and physiologists have suggested that the activity of apocrine sweat glands may signal sexual maturity.
List the functions of the adipose tissue within the subcutaneous tissue.
Approximately half the body's stored lipids are in the subcutaneous tissue, where they function in insulation and padding and as a source of energy.
Describe the structural features resulting from keratinization that make the epidermis structurally strong and resistant to water loss.
As they move from the deeper epidermal layers to the surface, the keratinocytes change shape and chemical composition, through the process called keratinization, where the cells accumulate keratin. During keratinization, the cells eventually die and produce an outer layer of dead, hard cells that resists abrasion and forms a permeability barrier. The study of keratinization is important because many skin diseases result from malfunctions in this process. For example, large scales of epidermal tissue are sloughed off in psoriasis. By comparing normal and abnormal keratinization, scientists may be able to develop effective therapies for psoriasis.
Explain the location and action of arrector pili muscles.
Associated with each hair follicle are smooth muscle cells called the arrector pili (ă-rek′tōr pī′lī). The arrector pili extend from the dermal root sheath of the hair follicle to the papillary layer of the dermis (figure 5.6a). Normally, the hair follicle and the hair inside it are at an oblique angle to the surface of the skin. When the arrector pili muscles contract, however, they pull the follicle into a more perpendicular position, causing the hair to "stand on end." ----Contraction of the arrector pili muscles causes hair to stand on end, but this does not significantly reduce heat loss in humans because so little hair covers the body. However, the hair on the head is an effective insulator.
What are the regions of a hair?
At puberty, terminal hair, especially in the pubic and axillary regions, replaces much of the vellus hair. The hair of the chest, legs, and arms is approximately 90% terminal hair in males and approximately 35% in females
Describe heat exchange in the skin.
Blood vessel dialation and constriction affect the blood flow across the epidermis of the skin.
How does the skin help regulate body temperature?
Body temperature is affected by blood flow through the skin. When blood vessels (arterioles) in the dermis dilate, more warm blood flows from deeper structures to the skin, and heat loss increases. Body temperature tends to increase as a result of exercise, fever, or a rise in environmental temperature. In order to maintain homeostasis, this excess heat must be lost. The body accomplishes this by producing sweat. The sweat spreads over the surface of the skin; as it evaporates, the body loses heat. When blood vessels in the dermis constrict, less warm blood flows from deeper structures to the skin, and heat loss decreases . If body temperature begins to drop below normal, heat can be conserved by a decrease in the diameter of dermal blood vessels
Why is heat potentially dangerous to the elderly?
Decreases in the activity of sweat glands and the blood supply to the dermis result in a reduced ability to regulate body temperature. ---- Elderly individuals who do not take proper precautions may experience heat exhaustion, which can even lead to death.
What are the layers of the skin?
EPIDERMIS: The epidermis is stratified squamous epithelium. It is separated from the underlying dermis by a basement membrane. The epidermis is not as thick as the dermis and contains no blood vessels. The living cells of the epidermis receive nutrients and excrete waste products by the diffusion of substances between the epidermis and the capillaries of the dermis DERMIS: The epidermis rests on the dermis (der′mis; skin), a layer of connective tissue. The structure of the dermis is responsible for most of the strength of the skin. The strength of the dermis is seen in leather, which is produced from the hide (skin) of an animal by removing the epidermis and preserving the dermis in a process called tanning. subcutaneous tissue, or hypodermis (hi-pō-der′mis), a layer of loose connective tissue. The subcutaneous tissue is not part of the skin or the integumentary system, but it does connect the skin to underlying muscle or bone.
Which glands of the skin are responsible for cooling the body? Where are they located?
Eccrine (ek′rin) sweat glands (sometimes called merocrine [mer′ō-krin, mer′ō-krīn, mer′ō-krēn] sweat glands) are the most common type of sweat gland. They are simple, coiled, tubular glands that open directly onto the surface of the skin through sweat pores . --The resulting hyposmotic fluid that leaves the duct is called sweat. When the body temperature starts to rise above normal, the sweat glands produce sweat, which evaporates and cools the body. Sweat also can be released in the palms, soles, and axillae as a result of emotional stress. Emotional sweating is used in lie detector (polygraph) tests because sweat gland activity may increase when a person tells a lie. Such tests can detect the sweat produced, even in small amounts, because the salt solution conducts electricity and lowers the electrical resistance of the skin.
What substances are excreted in sweat? Is the skin an important site of excretion?
Excretion is the removal of waste products from the body. In addition to water and salts, sweat contains a small amount of waste products, including urea, uric acid, and ammonia. However, even when large amounts of sweat are lost, the quantity of waste products eliminated in the sweat is insignificant because the urinary system excretes most of the body's waste products.
How do genetic factors, exposure to sunlight, and hormones determine the amount of melanin in the skin?
Exposure to ultraviolet light darkens the melanin already present in the skin and stimulates melanin production, resulting in tanning. Melanin production is determined by genetic factors, exposure to light, and hormones. Genetic factors are primarily responsible for the variations in skin color among different races and among people of the same race. It is interesting to note that the number of melanocytes in the skin is relatively the same for all humans, regardless of race. Racial variations in skin color are determined by several major factors: the amount and types of melanin produced by the melanocytes and the size, number, and distribution of the melanosomes.
What are the stages of hair growth?
Hair is produced in cycles that involve a growth stage and a resting stage. During the growth stage, a hair increases in length as new matrix cells are produced, differentiate, become keratinized, and die. The hair grows longer as cells are added at the base of the hair root. Eventually, hair growth stops; the hair follicle shortens and holds the hair in place. A resting period follows, after which a new cycle begins and a new hair replaces the old hair, which falls out of the hair follicle.
What makes a nail hard?
KERATIN: the nail matrix and bed are composed of epithelial tissue, with a stratum basale that gives rise to the cells that form the nail. The nail matrix is thicker than the nail bed and produces nearly all of the nail.
What happens to the melanin once it is produced?
Melanin is produced by melanocytes, irregularly shaped cells with many long processes that extend between the keratinocytes of the stratum basale and the stratum spinosum. Melanocytes produce and package melanin into vesicles called melanosomes, which move into cell processes of the melanocytes. Keratinocytes phagocytize the tips of the melanocyte cell processes, thereby acquiring melanosomes. Although all keratinocytes can contain melanin, the only cells that produce it are melanocytes --Although all keratinocytes can contain melanin, the only cells that produce it are melanocytes.
Do nails have growth stages?
Nails grow at an average rate of 0.5-1.2 mm per day, and fingernails grow more rapidly than toenails. Unlike hair, they grow continuously throughout life and do not have a resting phase.
Provide an example for each function of the integumentary system.
PROTECTION SENSATION TEMP REGULATION VITAMIN D PRODUCTION EXCRETION
What kinds of sensory receptors are in the skin, and why are they important?
Receptors in the skin can detect pain, heat, cold, and pressure. For example, the epidermis and dermal papillae are well supplied with touch receptors. The dermis and deeper tissues contain pain, heat, cold, touch, and pressure receptors. Hair follicles (but not the hair) are well innervated, and sensory receptors surrounding the base of hair follicles can detect hair movement
What do sebaceous glands secrete? What is the function of the secretion?
Sebaceous (sē-bā′shŭs) glands, located in the dermis, are simple or compound alveolar glands that produce sebum (sē′bŭm), an oily, white substance rich in lipids. Because sebum is released by the lysis and death of secretory cells, sebaceous glands are classified as holocrine glands. Most sebaceous glands are connected by a duct to the upper part of the hair follicles, from which the sebum oils the hair and the skin surface. The secretion of sebum onto the hair and surrounding skin prevents drying and protects against some bacteria.
What effect does exposure to sunlight have on skin?
Skin that is exposed to sunlight appears to age more rapidly than nonexposed skin. This effect is observed on areas of the body that receive sun exposure, such as the face and hands (figure 5.12). However, the effects of chronic sun exposure on the skin are different from the effects of normal aging. In skin exposed to sunlight, normal elastic fibers are replaced by an interwoven mat of thick, elastic-like material, the number of collagen fibers decreases, and the ability of keratinocytes to divide is impaired.
Describe the three layers of a hair seen in cross section.
The base of the root is expanded to form the hair bulb. Most of the root and the shaft are composed of columns of dead, keratinized epithelial cells arranged in three concentric layers: the medulla, the cortex, and the cuticle (figure 5.6c). The medulla (me-dool′ă) is the central axis of the hair, and it consists of two or three layers of cells containing soft keratin. The cortex surrounds the medulla and forms the bulk of the hair. The cells of the cortex contain hard keratin. The cortex is covered by the cuticle (kū′ti-kl), a single layer of cells also containing hard keratin. The edges of the cuticle cells overlap like shingles on a roof.
What type of cells make up most of a hair?
The base of the root is expanded to form the hair bulb. Most of the root and the shaft are composed of columns of dead, keratinized epithelial cells arranged in three concentric layers: the medulla, the cortex, and the cuticle (figure 5.6c). The medulla (me-dool′ă) is the central axis of the hair, and it consists of two or three layers of cells containing soft keratin. The cortex surrounds the medulla and forms the bulk of the hair. The cells of the cortex contain hard keratin. The cortex is covered by the cuticle (kū′ti-kl), a single layer of cells also containing hard keratin. The edges of the cuticle cells overlap like shingles on a roof.
What are formed by the dermal papillae in thick skin? What roles do they have?
The dermal papillae under the thick skin of the palms of the hands and soles of the feet lie in parallel, curving ridges that shape the overlying epidermis into fingerprints and footprints. The ridges increase friction and improve the grip of the hands and feet. Everyone has unique fingerprints and footprints, even identical twins.
Name and compare the two layers of the dermis.
The dermis is composed of two tissue layers (see figure 5.2a): the superficial papillary (pap′i-lār-ē) layer and the deeper reticular (re-tik′ū-lăr) layer. The papillary layer derives its name from projections, called dermal papillae (pă-pil′ē), that extend toward the epidermis. The papillary layer is loose connective tissue with thin fibers that are somewhat loosely arranged. The papillary layer also contains blood vessels that supply the overlying epidermis with oxygen and nutrients, remove waste products, and aid in regulating body temperature. --- The reticular layer, which is composed of dense irregular connective tissue, is the main layer of the dermis. It is continuous with the subcutaneous tissue and forms a mat of irregularly arranged fibers that are resistant to stretching in many directions. page 149The elastic and collagen fibers are oriented more in some directions than in others and produce cleavage lines, or tension lines, in the skin
What are cleavage lines, and how are they related to the healing of a cut?
The elastic and collagen fibers are oriented more in some directions than in others and produce cleavage lines, or tension lines, in the skin (figure 5.5). It is important for health professionals to understand cleavage line directions because an incision made parallel to the cleavage lines is less likely to gap than an incision made across them. The development of infections and the formation of scar tissue are reduced in wounds where the edges are closer together.
How is the epithelial root sheath important in skin repair?
The epithelial root sheath is divided into external and internal parts. At the opening of the follicle, the external epithelial root sheath has all the strata found in thin skin. Deeper in the hair follicle, the number of cells decreases until, at the hair bulb, only the stratum basale is present. This has important consequences for skin repair. If the epidermis and the superficial part of the dermis are damaged, the keratinocyte stem cells located in the stratum basale of the undamaged part of the hair follicle can be a source of new epithelium. The internal epithelial root sheath has raised edges that mesh closely with the raised edges of the hair cuticle and hold the hair in place. When a hair is pulled out, the internal epithelial root sheath usually comes out as well and is plainly visible as whitish tissue around the root of the hair.
In what part of a hair does growth take place?
The hair bulb is an expanded knob at the base of the hair root. Inside the hair bulb is a mass of undifferentiated epithelial cells called the matrix. The matrix produces the hair and the internal epithelial root sheath. The dermis of the skin projects into the hair bulb as a hair papilla. Within the hair papilla are blood vessels that provide nourishment to the cells of the matrix
Describe the parts of a hair follicle.
The hair follicle is a tubelike invagination of the epidermis that extends into the dermis. A hair develops and grows within each hair follicle. A hair follicle consists of a dermal root sheath and an epithelial root sheath. The dermal root sheath is the portion of the dermis that surrounds the epithelial root sheath
In which stratum are new cells formed by mitosis?
The keratinocytes of the epidermis are constantly lost at its surface but are also constantly replaced by other cells moving from deeper layers. New keratinocytes are produced when keratinocyte stem cells undergo mitosis in the deepest layer of the epidermis. As new cells form, they push older cells to the surface, where they slough off.
Do all hairs grow at the same rate?
The length of each stage depends on the hair—eyelashes grow for approximately 30 days and rest for 105 days, whereas scalp hairs grow for 3 years and rest for 1-2 years. At any given time, an estimated 90% of the scalp hairs are in the growing stage, and loss of approximately 100 scalp hairs per day is normal.
What is the lunula?
The nail bed is visible through the clear nail and appears pink because of blood vessels in the dermis. A small part of the nail matrix, the lunula (loo′noo-lă), is seen through the nail body as a whitish, crescent-shaped area at the base of the nail. The lunula, seen best on the thumb, appears white because the blood vessels do not show through the thicker nail matrix.
Name the parts of a nail. Which part produces most of the nail?
The nail root extends distally from the nail matrix. The nail also attaches to the underlying nail bed, which is located between the nail matrix and the hyponychium. The nail matrix and bed are composed of epithelial tissue, with a stratum basale that gives rise to the cells that form the nail. The nail matrix is thicker than the nail bed and produces nearly all of the nail.
Explain what causes age spots and white hair.
The number of functioning melanocytes generally decreases; however, in some localized areas, especially on the hands and face, melanocytes increase in number, producing age spots. (Age spots are different from freckles, which are caused by an increase in melanin production, not an increase in melanocyte numbers.) White or gray hairs also appear because of a decrease in or lack of melanin production.
Which layer is responsible for most of the structural strength of the skin?
The reticular layer, which is composed of dense irregular connective tissue, is the main layer of the dermis. It is continuous with the subcutaneous tissue and forms a mat of irregularly arranged fibers that are resistant to stretching in many directions. page 149The elastic and collagen fibers are oriented more in some directions than in others and produce cleavage lines, or tension lines, in the skin
How is the subcutaneous tissue related to the skin?
The subcutaneous tissue attaches the skin to underlying bone and muscle and supplies the skin with blood vessels and nerves
Name the types of tissue forming the subcutaneous tissue layer.
The subcutaneous tissue attaches the skin to underlying bone and muscle and supplies the skin with blood vessels and nerves . The subcutaneous tissue consists of loose connective tissue with collagen and elastic fibers. The main types of cells within the subcutaneous tissue are fibroblasts, adipocytes, and macrophages. The subcutaneous tissue, which is not part of the skin, is sometimes called the hypodermis.
What are hemidesmosomes?
These are "half desmosomes" that anchor to the basal layer of cells of teh epidermis.
Compare the structure and location of thick and thin skin. Is hair in thick or thin skin?
Thick skin has all five epithelial strata, and the stratum corneum has many layers of cells. Thick skin is found in areas subject to pressure or friction, such as the palms of the hands, the soles of the feet, and the fingertips. Thin skin covers the rest of the body and is more flexible than thick skin. Each of its strata contains fewer layers of cells than are found in thick skin; the stratum granulosum frequently consists of only one or two layers of cells, and the stratum lucidum is generally absent. Hair is found only in thin skin.
What is the process of melanin production?
To produce melanin, the enzyme tyrosinase, converts the amino acid tyrosine to dopaquinone. Dopaquinone can be converted to a variety of related molecules, most of which are brown to black pigments but some of which are yellowish or reddish.
Name the locations where cholecalciferol is produced and then modified into vitamin D.
When exposed to ultraviolet light, the precursor molecule is converted into cholecalciferol (kō′lē-kal-sif′er-ol). Cholecalciferol is released into the blood and modified first by the liver and later by the kidneys to form active vitamin D3, calcitriol --Vitamin D synthesis involves a precursor molecule, 7-dehydrocholesterol
What cells can be found in the epidermis?
keratinocytes: make up most of the cells of the epidermis. They produce keratin which helps maintain the strength of the cell. Melanocytes: produce the pigment of the skin. Langerhan Cells: part of the immune cells, Merkel Cells: specialized epidermal cells connected to nerve endings that sense light touch and pressure
Which cells of the epidermis produce melanin?
melanocytes (mel′ă-nō-sītz), irregularly shaped cells with many long processes that extend between the keratinocytes of the stratum basale and the stratum spinosum
What determines the different shades of hair color?
melanocytes within the hair bulb matrix produce melanin and pass it to keratinocytes in the hair cortex and medulla. As with the skin, varying amounts and types of melanin cause different shades of hair color. Blonde hair has little black-brown melanin, whereas jet black hair has the most. Intermediate amounts of melanin account for different shades of brown. Red hair is caused by varying amounts of a red type of melanin. Hair sometimes contains both black-brown and red melanin
What is keratinization?
the process of replacing viable cells in the stratum basale with more and more of the waxy keratin protein as cells move from the deepest layer to the surface layer
Compared with young skin, why is aged skin more likely to be damaged, wrinkled, and dry?
the skin is more easily damaged because the epidermis thins and the amount of collagen in the dermis decreases. Skin infections are more likely, and skin repair occurs more slowly. A decrease in the number of elastic fibers in the dermis and a loss of adipose tissue from the subcutaneous tissue cause the skin to sag and wrinkle.-----The skin also becomes drier with age as sebaceous gland activity decreases. ---
