Questions and Answers
What are the three epidermal derivatives of the integument?
Nails, hair, and exocrine glands.
What is the primary component of nails and hairs?
Dead keratinocytes.
What is the function of fingernails?
They protect the distal tips of the digits during jumping, kicking, or catching, and assist in grasping objects.
What is the nail body?
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What is the significance of changes in the shape, structure, or appearance of the nails?
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What causes brittle nails?
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What is the nail bed?
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What is the nail root?
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What is the embryonic hair that first appears on the fetus in the last trimester of development?
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What type of hair grows on the scalp, and is the hair of eyebrows and eyelashes?
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What is the zone of the hair extending from the bulb to the skin surface?
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What contains living epithelial cells in the hair?
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What is the remnant of the soft core of the matrix in hair structure?
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What forms the outermost layer of the hair shaft?
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What is the muscular structure that surrounds the hair follicle and is responsible for goose bumps?
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What is the primary function of hair on the head?
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What type of keratinization occurs within the hair matrix?
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What is the zone at the base of the hair where the hair originates in the dermis?
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What is the likely cause of nail pitting, and what are some possible underlying disorders associated with it?
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What is nail clubbing, and what is it often associated with?
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What is onychomycosis, and what causes it?
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What is yellow nail syndrome, and what is it often associated with?
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What is Beau's lines, and what do they indicate?
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Why does the nail body appear darker or pinkish in color?
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What is the lunula, and what causes its lighter-colored appearance?
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What is the eponychium, and what is its function?
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What is the hyponychium, and what is its function?
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What is spoon nails, and what is it often associated with?
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How do cerumen and tiny hairs in the meatus work together to protect the eardrum?
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What is the primary function of mammary glands in lactating females?
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How do apocrine sweat glands differ from merocrine sweat glands in terms of their secretions?
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What is the function of sebaceous glands in the body?
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How does the development of mammary glands and their secretions relate to hormonal control?
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What is the primary function of merocrine sweat glands in the regulation of body temperature?
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What is the mechanism by which both apocrine and merocrine sweat glands produce their secretion?
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What is the composition of sweat secreted by merocrine sweat glands?
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What are the characteristics of the secretion produced by apocrine sweat glands?
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What is the role of myoepithelial cells in sweat gland function?
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What is the function of sebum produced by sebaceous glands?
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Where do apocrine sweat glands release their secretions?
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What is the effect of nervous system stimulation on sweat gland production and secretion?
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What stimulates the secretion of sebum in both sexes?
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What are ceruminous glands, and where are they located?
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What is the significance of merocrine sweat gland secretions in protecting against environmental hazards?
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What is acne, and what causes it?
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What is the location of sebaceous glands in the skin?
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What determines hair color?
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What is the process by which merocrine sweat glands release their secretions?
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What is the function of sebaceous glands in the skin?
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What is the function of cerumen produced by ceruminous glands?
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When do sebaceous glands become active and produce secretions?
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What is the common cause of hirsutism?
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What is the significance of apocrine sweat glands becoming active during puberty?
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What is the primary function of hair within the nostrils?
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How does hair on the head contribute to heat retention?
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What are the different types of acne lesions?
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What is the longest stage of the hair growth cycle?
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What is the typical rate of hair loss on a normal scalp?
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What is alopecia areata?
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What is the cause of male pattern baldness?
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What is hirsutism?
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What is the significance of the hair follicle receptors?
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What is the consequence of complete stoppage of melanin production within the hair follicle?
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Study Notes
Integumentary Structures Derived from Epidermis
- Nails, hair, and exocrine glands of the skin are derived from the epithelium that forms the epidermis
- These structures are also known as epidermal derivatives or epidermal appendages of the integument
- They formed during embryologic development as portions of the epidermis invaginated into the dermis
Nails
- Nails are scalelike modifications of the stratum corneum layer of the epidermis that form on the dorsal edges of the fingers and toes
- Protect the distal tips of the digits during jumping, kicking, or catching
- Fingernails also assist in grasping objects
- Each nail has a distal light-colored free edge, a darker colored nail body, and a nail root, which is the proximal part embedded in the skin
- The nail body covers a layer of epidermis called the nail bed, which contains only the deeper, living cell layers of the epidermis
Nail Disorders
- Changes in the shape, structure, or appearance of the nails are clinically significant
- Nail disorders can be indicative of overall health
- Examples of nail disorders:
- Brittle nails: prone to vertical splitting and separation of the nail plate layers at the free edge
- Ingrown nails: painful condition where the edge of a nail digs into the skin around it
- Nail pitting: tiny depressions or shallow holes that appear in the nail body
- Nail clubbing: the tip of the finger enlarges and the edges of the nail grow and curve around the tip
- Onychomycosis: fungal infection that occurs in nails constantly exposed to warmth and moisture
- Yellow nail syndrome: slowed or stopped nail growth, often a sign of respiratory disease
- Spoon nails: concave shape of the nails, often a sign of iron deficiency
- Beau's lines: horizontal lines across the nail, indicating temporary interference with nail growth
- Vertical ridging of the nails: common and usually not indicative of a serious medical problem
Hair
- Found almost everywhere on the body except the palms of the hands and palmar surface of the fingers, the sides and soles of the feet and toes, the lips, and portions of the external genitalia
- General structure of hair and its relationship to the integument are shown in figure 6.10
- Hair is a derivative of the epithelium
- Composed of keratinized cells growing from hair follicles that extend into the dermis, and often deeper into the underlying subcutaneous layer
Hair Type and Distribution
- Three kinds of hair produced during our lives: lanugo, vellus, and terminal hair
- Lanugo: fine, unpigmented, downy hair that first appears on the fetus in the last trimester of development
- Vellus: fine, unpigmented or lightly pigmented hair that is the primary human hair and is found on the upper and lower limbs
- Terminal hair: coarser, pigmented, and longer than vellus, grows on the scalp, eyebrows, and eyelashes
Hair Structure and Follicles
- Three zones of a hair: the hair bulb, root, and shaft
- Hair bulb: consists of epithelial cells and is a swelling at the base where the hair originates in the dermis
- Hair root: zone of the hair extending from the bulb to the skin surface
- Hair shaft: third portion of the hair that extends beyond the skin surface
- Hair bulb contains living epithelial cells, whereas the root and shaft consist of dead epithelial cells
- Hair production involves a specialized type of keratinization that occurs within the hair matrix, a structure immediately adjacent to the hair papilla in the hair bulb
Hair Growth and Replacement
- Three stages of the hair growth cycle: anagen, catagen, and telogen
- Anagen phase: active phase of growth where living cells of the hair bulb are rapidly growing, dividing, and transforming into hair
- Catagen phase: brief regression period where cell division ceases and the follicle undergoes involution
- Telogen phase: resting phase and is usually the phase when the hair is shed
- Hair growth rate and the duration of the hair growth cycle vary; however, the scalp normally loses between 10 and 100 hairs per day
Exocrine Glands of the Skin
- Two types of exocrine glands: sweat glands and sebaceous glands
- Sweat glands: release their secretions directly onto the surface of the skin or into a hair follicle
- Sebaceous glands: produce an oily, waxy secretion called sebum that is usually discharged into a hair follicle and onto the hair itself
Sweat Glands
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Merocrine sweat glands: the most numerous and widely distributed sweat glands, discharge their secretions directly onto the surface of the skin
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Apocrine sweat glands: release their secretion into hair follicles in the axillae, around the nipples, in the pubic region, and in the anal region### Acne
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Acne can occur at any age, but it is most prevalent during teenage years
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There are different types of acne lesions, including comedos, papules, pustules, nodules, and cysts
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Comedos can be open (blackheads) or closed (whiteheads) and are caused by plugged sebaceous glands
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Papules are dome-shaped, fluid-filled lesions that can form red elevations on the skin
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Pustules are similar to papules but are filled with a mixture of white blood cells, dead skin cells, and bacteria
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Nodules are similar to pustules but extend deeper into the skin and can cause scarring
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Cysts are large, fluid-filled nodules that can become severely inflamed and painful, leading to scarring
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There are various medicinal treatments available for acne, including benzoyl peroxide, salicylic acid, antibiotics, and retinoids
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Untreated severe acne can lead to scarring, as can picking at acne lesions
Ceruminous Glands
- Ceruminous glands are modified apocrine sweat glands located in the external acoustic meatus (ear canal)
- These glands produce cerumen, a waterproof earwax that helps trap foreign particles and lubricate the ear canal
- Cerumen also helps prevent small insects from reaching the eardrum
Mammary Glands
- Mammary glands are modified apocrine sweat glands located in the breasts
- These glands become functional only in pregnant and lactating females, producing breast milk that nourishes offspring
- The development of mammary glands and their secretions are controlled by a complex interaction between gonadal and pituitary hormones
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Description
This quiz covers the formation and characteristics of nails, hair, and exocrine glands of the skin, derived from the epidermis during embryologic development.