L4: Integumentary Pt. 1 Flashcards
(377 cards)
1
Q
contributes to homeostasis by protecting the body and helping regulate body temperature. It also allows you to sense pleasurable, painful, and other stimuli in your external environment.
A
integumentary system
2
Q
helps maintain a constant body tem perature, protects the body, and provides sensory information about the surrounding environment
A
integumentary system
3
Q
the bluish skin color associated with ____ (oxygen deficiency at the tissue level) is one sign of heart failure as well as other disorders.
A
hypoxia
4
Q
Abnormal skin eruptions or rashes such as chicken pox, cold sores, or measles may reveal ____ or diseases of internal organs, whereas other conditions, such as warts, age spots, or pimples, may involve the skin alone.
A
systemic infections
5
Q
includes the skin, hair, oil and sweat glands, nails, and sensory receptors.
A
integumentary system
6
Q
Functions of the Integumentary System
A
- Regulates body temperature. 2. Stores blood. 3. Protects body from external environment. 4. Detects cutaneous sensations. 5. Excretes and absorbs substances. 6. Synthesizes vitamin D
7
Q
Components of the integumentary system.
A
The skin consists of a superficial, thin epidermis and a deep, thicker dermis. Deep to the skin is the subcutaneous tissue, which attaches the dermis to underlying fascia.
8
Q
is the medical specialty that deals with the structure, function, and disorders of the integumentary system.
A
Dermatology
9
Q
covers the external surface of the body and is by weight the largest organ of the body in weight. In adults, the skin covers an area of about 2 square meters (22 square feet) and weighs 4.5–5 kg (10–11 lb), about 7% of total body weight.It ranges in thickness from 0.5 mm (0.02 in.) on the eyelids to 5.0 mm (0.2 in.) on the heels. Over most of the body it is 1–2mm (0.04–0.08 in.) thick.
A
skin or cutaneous membrane
10
Q
The skin consists of two main parts
A
epidermis and dermis
11
Q
The superficial, thinner portion, which is composed of epithe lial tissue, is the ____. It is also avascular.
A
epidermis
12
Q
The deeper, thicker connective tissue portion is the ____; vascular
A
dermis
13
Q
If you cut the ____ there is no bleeding, but if the cut penetrates to the ____ there is bleeding.
A
epidermis and dermis
14
Q
Deep to the dermis, but not part of the skin, is the
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sub cutaneous (subQ) tissue or hypodermis
15
Q
this tissue consists of areolar and adipose tissues
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hypodermis
16
Q
Fibers that extend from the dermis anchor the skin to the ___, which in turn attaches to underlying fascia, the connective tissue around muscles and bones.
A
sub cutaneous tissue
17
Q
serves as a storage depot for fat and contains large blood vessels that supply the skin.
A
sub cutaneous tissue
18
Q
The subcutaneous region also contains nerve endings called ____ that are sensitive to pressure
A
lamellar corpuscles or pacinian corpuscles
19
Q
is composed of keratinized stratified squa mous epithelium.
A
epidermis
20
Q
It contains four principal types of cells:
A
kera tinocytes, melanocytes, dendritic cells, and tactile epithelial cells
21
Q
About 85% of epidermal cells are _____, which are arranged in four or five layers and produce the protein keratib
A
keratinocytes
22
Q
is a tough, fibrous protein that helps protect the skin and under lying tissues from abrasions, heat, microbes, and chemicals.
A
keratin
23
Q
Keratinocytes also produce lamellar granules, which release a water- repellent sealant that decreases water entry and loss and inhibits the entry of foreign materials.
A
lamellar granules
24
Q
About 8% of the epidermal cells are _____, the pigment producing cells of the body. They migrate from the ectoderm of a developing embryo and produce the pigment melanin. Their long, slender projections extend between the keratinocytes and transfer melanin granules to them.
A
melanocytes
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is a yellow- red or brown- black pigment that contributes to skin color and absorbs damaging ultraviolet (UV) light. Within the keratinocytes, mela nin granules cluster to form a protective veil over the nucleus to shield the nuclear DNA from damage by UV light. Although their melanin granules effectively protect keratinocytes, melanocytes themselves are particularly susceptible to damage by UV light.
Melanin
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arise from red bone marrow and migrate to the epidermis, where they constitute about 5% of the epidermal cells. They participate in immune responses mounted against microbes that invade the skin, and are easily damaged by UV light. Their role in the immune response is to help other cells of the immune system recognize an invading microbe and destroy it.
Dendritic cells or Langerhans cells
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are the least numerous of the epidermal cells, making up about 2% of epider mal cells.
tactile epithelial cells, or Merkel cells
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They are located in the deepest layer of the epidermis, where they make contact with the flattened process of a sensory neuron (nerve cell), called a
nonencapsulated sensory corpuscle or Merkel disc
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Tactile epithe lial cells and their associated nonencapsulated sensory corpus cles detect
touch sensations
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Several distinct layers of keratinocytes in various stages of development form the
epidermis
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In most regions of the body the epidermis has four strata (STRĀ- ta) or layers
stratum basale, stratum spinosum, stratum granulosum, and a thin stratum corneum
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In most regions of the body the epidermis has four strata (STRĀ- ta) or layers— stratum basale, stratum spinosum, stratum granulosum, and a thin stratum corneum. This is called
thin skin
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Where expo sure to friction is greatest, such as in the palms, palmar surfaces of the digits, soles, and plantar surfaces of the toes, the epidermis has five layers— stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and a thick stratum corneum. This is called
thick skin
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Most of the ___ consists of keratinocytes, which produce the protein keratin (protects underlying tissues), and lamellar granules (contain a waterproof sealant).
epidermis
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Cells in the epidermis.
Besides keratinocytes, the epidermis contains melanocytes, which produce the pigment melanin; dendritic cells, which participate in immune responses; and tactile epithelial cells, which function in the sensation of touch.
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The epidermis consists of
keratinized stratified squamous epithelium.
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The deepest layer of the epidermis is the ____, composed of a single row of cuboidal or columnar keratinocytes.
stratum basale
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What is the deepest layer of the epidermis?
Stratum basale
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What is the stratum basale composed of?
A single row of cuboidal or columnar keratinocytes
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What type of cells in the stratum basale undergo cell division to continually produce new keratinocytes?
Epidermal stem cells
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What is the size of the nuclei of keratinocytes in the stratum basale?
Large
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What does the cytoplasm of keratinocytes in the stratum basale contain?
Many ribosomes, a small Golgi complex, a few mitochondria, and some rough endoplasmic reticulum
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What are the scattered intermediate filaments within keratinocytes of the stratum basale called?
Keratin intermediate filaments (tonofilaments)
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What does the keratin intermediate filaments form in the more superficial epidermal layers?
Tough protein keratin
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What does keratin protect the deeper layers from?
Injury
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What structure do keratin intermediate filaments attach to, which binds cells of the stratum basale to each other and to adjacent stratum spinosum cells?
Desmosomes
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What structure binds the keratinocytes to the basement membrane?
Hemidesmosomes
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Where is the basement membrane positioned?
Between the epidermis and the dermis
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What types of cells are scattered among the keratinocytes of the basal layer?
Melanocytes and tactile epithelial cells with their associated nonencapsulated sensory corpuscles
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What is another name for the stratum basale?
Stratum germinativum
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Why is the stratum basale also called the stratum germinativum?
To indicate its role in forming new cells
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What is superficial to the stratum basale?
Stratum spinosum
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What does the stratum spinosum mainly consist of?
Numerous keratinocytes arranged in 8–10 layers
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What happens to the cells in the more superficial layers of the stratum spinosum?
They become somewhat flattened
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What produces the keratinocytes in the stratum spinosum?
Epidermal stem cells in the basal layer
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What do keratinocytes in the stratum spinosum have the same as the cells of the stratum basale?
The same organelles
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What do the keratinocytes of the stratum spinosum produce?
Coarser bundles of keratin in intermediate filaments than those of the basal layer
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How do cells of the stratum spinosum appear when prepared for microscopic examination?
They shrink and pull apart except where the membranes join at desmosomes, appearing to be covered with thornlike spines
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Why do cells of the stratum spinosum appear covered with thornlike spines?
Because they shrink and pull apart except where the membranes join at desmosomes
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What inserts into desmosomes at each spinelike projection?
Bundles of keratin intermediate filaments
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What does the arrangement of keratin intermediate filaments and desmosomes provide to the skin?
Both strength and flexibility
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What other cells are present in the stratum spinosum?
Dendritic cells and projections of melanocytes
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Where is the stratum granulosum located?
About the middle of the epidermis
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What does the stratum granulosum consist of?
Three to five layers of flattened keratinocytes that are undergoing apoptosis
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What is apoptosis?
An orderly, genetically programmed cell death in which the nucleus fragments before the cells die
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Why do the nuclei and other organelles of these cells begin to degenerate?
Because they move farther from their source of nutrition (the dermal blood vessels)
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Why do keratin intermediate filaments become more apparent in the stratum granulosum?
Because the organelles in the cells are regressing
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What is a distinctive feature of cells in the stratum granulosum?
The presence of darkly staining granules of a protein called keratohyalin
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What does keratohyalin do?
Assembles keratin intermediate filaments into keratin
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What are also present in the keratinocytes of the stratum granulosum?
Membrane-enclosed lamellar granules
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What do lamellar granules do?
Fuse with the plasma membrane and release a lipid-rich secretion
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Where is the lipid-rich secretion deposited?
In the spaces between cells of the stratum granulosum, stratum lucidum, and stratum corneum
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What does the lipid-rich secretion act as?
A water-repellent sealant, retarding loss and entry of water and entry of foreign materials
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Why can keratinocytes of the stratum granulosum no longer carry on vital metabolic reactions?
Because their nuclei break down during apoptosis
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What happens to keratinocytes of the stratum granulosum after apoptosis?
They die
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What does the stratum granulosum mark?
The transition between the deeper, metabolically active strata and the dead cells of the more superficial strata
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Where is the stratum lucidum present?
Only in the thick skin of areas such as the palms, palmar surfaces of the digits, soles, and plantar surfaces of the toes
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What does the stratum lucidum consist of?
Four to six layers of flattened clear, dead keratinocytes
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What do the keratinocytes in the stratum lucidum contain?
Large amounts of keratin and thickened plasma membranes
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What does the stratum lucidum probably provide?
An additional level of toughness in this region of thick skin
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What does the stratum corneum consist of?
25 to 30 layers of flattened dead keratinocytes
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How thick can the stratum corneum range from?
A few cells in thin skin to 50 or more cell layers in thick skin
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What do the cells in the stratum corneum no longer contain?
A nucleus or any internal organelles
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What are the cells in the stratum corneum enclosed by?
Plasma membrane–enclosed packages of keratin
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What are the cells in the stratum corneum the final product of?
The differentiation process of the keratinocytes
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How do the cells within each layer of the stratum corneum overlap?
Like the scales on the skin of a snake
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What type of connections do neighboring layers of cells form?
Strong connections with one another
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How are the plasma membranes of adjacent cells arranged?
In complex, wavy folds that fit together like pieces of a jigsaw puzzle to hold the layers together via ridges and grooves
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What happens to cells in the outer stratum of the epidermis?
They are continuously shed and replaced by cells from the deeper strata
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What do the multiple layers of dead cells in the stratum corneum help protect against?
Injury and microbial invasion
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What does constant exposure of skin to friction stimulate?
Increased cell production and keratin production
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What does increased cell production and keratin production result in?
The formation of a callus
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What is a callus?
An abnormal thickening of the stratum corneum
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When can new skin not regenerate?
If an injury destroys a large area of the stratum basale and its stem cells
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What do skin wounds of this magnitude require in order to heal?
Skin grafts
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What is a skin graft?
The transfer of a patch of healthy skin taken from a donor site to cover a wound
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Why is a skin graft performed?
To protect against fluid loss and infection, to promote tissue healing, to reduce scar formation, to prevent loss of function, and for cosmetic reasons
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How is tissue rejection avoided in a skin graft?
By taking the transplanted skin from the same individual (autograft) or an identical twin (isograft)
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What procedure is used if skin damage is so extensive that an autograft would cause harm?
Autologous skin transplantation
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What is autologous skin transplantation?
A self-donation procedure where small amounts of an individual’s epidermis are removed, and the keratinocytes are cultured in the laboratory to produce thin sheets of skin
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Who is autologous skin transplantation most often performed for?
Severely burned patients
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What happens to the new skin in autologous skin transplantation?
It is transplanted back to the patient so that it covers the burn wound and generates a permanent skin
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What other products are available as skin grafts for wound coverage?
Apligraft and Transite
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Where are Apligraft and Transite grown from?
The foreskins of circumcised infants
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Deepest layer, composed of single row of cuboidal or columnar keratinocytes that contain scattered keratin intermediate filaments (tonofilaments); epidermal stem cells undergo cell division to produce new keratinocytes; melanocytes and tactile epithelial cells associated with nonencapsulated sensory corpuscles are scattered among epidermal stem cells.
Stratum Basale
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Eight to ten rows of many- sided keratinocytes with bundles of keratin intermediate filaments; contains projections of melanocytes and dendritic cells
Stratum Spinosum
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Three to five rows of flattened keratinocytes, in which organelles are beginning to degenerate; cells contain the protein keratohyalin (converts keratin intermediate filaments into keratin) and lamellar granules (release lipid- rich, water- repellent secretion).
Stratum Granulosum
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Present only in skin of palms, palmar surfaces of digits, soles, and plantar surfaces of toes; consists of four to six rows of clear, flat, dead keratinocytes with large amounts of keratin.
Stratum Lucidum
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Few to 50 or more rows of dead, flat keratinocytes that contain mostly keratin.
Stratum Corneum
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What happens to newly formed cells in the stratum basale?
They are slowly pushed to the surface
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What do cells accumulate as they move from one epidermal layer to the next?
More and more keratin
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What is the process of accumulating keratin called?
Keratinization
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What happens to cells after undergoing keratinization?
They undergo apoptosis to form dead surface layers of cells
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What eventually happens to keratinized cells?
They slough off and are replaced by underlying cells that in turn become keratinized
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How long does the whole process of cell formation, keratinization, and sloughing off take?
About seven to ten weeks in an average epidermis of 0.1 mm (0.004 in.) thickness
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Where do nutrients and oxygen diffuse from to reach the avascular epidermis?
From blood vessels in the dermis
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Which epidermal cells receive most of the nutrients and oxygen?
The epidermal cells of the stratum basale
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Why do the epidermal cells of the stratum basale receive most of the nutrients and oxygen?
Because they are closest to the blood vessels
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What do the cells of the stratum basale continuously undergo?
Cell division to produce new keratinocytes
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What happens to new keratinocytes as they are pushed farther from the blood supply?
They receive fewer nutrients, become less active, and eventually die
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When does the rate of cell division in the stratum basale increase?
When the outer layers of the epidermis are stripped away, as occurs in abrasions and burns
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What plays a role in regulating epidermal growth?
Hormonelike proteins such as epidermal growth factor (eGF)
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What is an excessive amount of keratinized cells shed from the skin of the scalp called?
Dandruff
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What is psoriasis?
A common and chronic skin disorder in which keratinocytes divide and move more quickly than normal from the stratum basale to the stratum corneum
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How quickly are keratinocytes shed in psoriasis?
Prematurely in as little as 7 to 10 days
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What do immature keratinocytes produce in psoriasis?
An abnormal keratin
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What does abnormal keratin form on the skin surface?
Flaky, silvery scales
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Where are flaky, silvery scales most often found in psoriasis?
On the knees, elbows, and scalp (dandruff)
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What are effective treatments for psoriasis?
Various topical ointments and ultraviolet phototherapy
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How do effective treatments help with psoriasis?
They suppress cell division, decrease the rate of cell growth, or inhibit keratinization
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What is the second, deeper part of the skin called?
The dermis
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What type of tissue is the dermis composed of?
Dense irregular connective tissue containing collagen and elastic fibers
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What property does the woven network of fibers in the dermis have?
Great tensile strength (resists pulling or stretching forces)
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What abilities does the dermis have?
It can stretch and recoil easily
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How does the thickness of the dermis vary?
It is much thicker than the epidermis and varies from region to region, reaching its greatest thickness on the palms and soles
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What is leather made from?
The dried and treated dermis of other animals
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What are the few cells present in the dermis?
Predominantly fibroblasts, with some macrophages and a few adipocytes near the subcutaneous tissue
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What structures are embedded in the dermal layer?
Blood vessels, nerves, glands, and hair follicles
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Why is the dermis essential to the epidermis?
It is essential to the survival of the epidermis, forming important structural and functional relations
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What are the two divisions of the dermis based on tissue structure?
The papillary dermis and the reticular dermis
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What fraction of the total dermal thickness does the papillary dermis make up?
About one-fifth
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What type of fibers does the papillary dermis contain?
Thin collagen and fine elastic fibers
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What are dermal papillae?
Small, nipple-shaped structures that project into the undersurface of the epidermis
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What do all dermal papillae contain?
Capillary loops (blood vessels)
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What are tactile corpuscles (Meissner corpuscles)?
Nerve endings in some dermal papillae that are sensitive to touch
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What are free nerve endings?
Dendrites in some dermal papillae that lack structural specialization
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What sensations do free nerve endings initiate?
Warmth, coolness, pain, tickling, and itching
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What is the reticular dermis attached to?
The subcutaneous tissue
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What does the reticular dermis contain?
Bundles of thick collagen fibers, scattered fibroblasts, and various wandering cells (such as macrophages)
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Where can adipose cells be found in the reticular dermis?
In the deepest part, along with coarse elastic fibers
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How are collagen fibers in the reticular dermis arranged?
In a netlike manner with a more regular arrangement than those in the papillary dermis
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What is the function of the large collagen fibers in the reticular dermis?
They help the skin resist stretching
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What structures occupy the spaces between fibers in the reticular dermis?
Blood vessels, nerves, hair follicles, sebaceous glands, and sudoriferous glands
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What does the combination of collagen and elastic fibers in the reticular dermis provide?
Strength, extensibility, and elasticity
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What is extensibility?
The ability of the skin to stretch
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What is elasticity?
The ability of the skin to return to its original shape after stretching
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Where can extensibility be readily seen?
Around joints, in pregnancy, and in obesity
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What surfaces have a series of elevations that appear either as straight lines or as a pattern of loops and whorls?
The surfaces of the palms, palmar surfaces of the digits, soles, and plantar surfaces of the toes
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What are the elevations on the palms, soles, and digits called?
Epidermal ridges
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When are epidermal ridges produced?
During the third month of fetal development
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What do epidermal ridges follow?
The contours of the dermal papillae of the papillary dermis
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What are epidermal pegs?
Extensions of the epidermis that project into the papillary dermis between dermal papillae
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What is one function of epidermal ridges?
They increase the surface area of the epidermis and thus increase the grip of the hand or foot by increasing friction
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How do epidermal ridges affect tactile sensitivity?
They greatly increase surface area, which increases the number of corpuscles of touch and thus increases tactile sensitivity
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How are fingerprints or footprints formed?
The ducts of sweat glands open on the tops of the epidermal ridges as sweat pores, and the sweat and ridges form fingerprints or footprints on touching a smooth object
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How is the epidermal ridge pattern determined?
It is in part genetically determined and is unique for each individual
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Do identical twins have the same epidermal ridge pattern?
No, even identical twins have different patterns
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How does the epidermal ridge pattern change during life?
It normally does not change, except to enlarge
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What is the study of the pattern of epidermal ridges called?
Dermatoglyphics
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What do the dermal papillae increase?
They greatly increase the surface contact between the dermis and epidermis
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What is the function of the increased dermal contact surface?
It serves as an important source of nutrition for the overlying epidermis
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How do molecules reach the cells of the stratum basale?
They diffuse from the small blood capillaries in the dermal papillae to the cells of the stratum basale
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Why do keratinocytes eventually lose their organelles?
As keratinocytes push toward the surface and away from the dermal blood source, they are no longer able to obtain the nutrition they require, leading to the breakdown of their organelles
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How do dermal papillae and epidermal pegs fit together?
They form an extremely tight junction between the two layers
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What does the jigsaw puzzle-like connection between the dermis and epidermis do?
It strengthens the skin against forces that move the epidermis and dermis in opposite directions (shear forces)
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What would happen if shear forces acted on the skin without this tight junction?
The epidermis would slide across the dermis, tearing the junction between the layers
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What can result from the internal damage to the dermis when the skin is stretched too much?
Striae (stretch marks)
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What type of scarring are striae?
A form of internal scarring
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What happens when the skin is overstretched?
The lateral bonding between adjacent collagen fibers is disrupted and small dermal blood vessels rupture
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Why do striae initially appear as reddish streaks?
Because small dermal blood vessels rupture
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Why do stretch marks later appear as silvery white streaks?
Because scar tissue, which is poorly vascularized, forms at these sites of dermal breakdown
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When do striae often occur in the abdominal skin?
During pregnancy
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Where do striae appear on weightlifters?
On the skin where it is stretched by a rapid increase in muscle mass
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In what condition does striae appear due to stretched skin?
Gross obesity
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Why do collagen fibers within the reticular dermis tend to orient more in one direction than another in certain regions of the body?
Because of natural tension experienced by these regions of the skin resulting from bony projections, orientation of muscles, and movements of joints
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What do tension lines (cleavage lines) in the skin indicate?
The predominant direction of underlying collagen fibers
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Why is knowledge of tension lines especially important to plastic surgeons?
Because a surgical incision running parallel to the collagen fibers will heal with only a fine scar
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What happens when a surgical incision is made across the rows of collagen fibers?
The collagen is disrupted, and the wound tends to gape open and heal in a broad, thick scar
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Superficial portion of dermis (about one- fifth); consists of areolar connective tissue with thin collagen and fine elastic fibers; contains dermal ridges that house blood capillaries, tactile corpuscles, and free nerve endings.
Papillary
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Deeper portion of dermis (about four- fifths); consists of dense irregular connective tissue with bundles of thick collagen and some coarse elastic fibers. Spaces between fibers contain some adipose cells, hair follicles, nerves, sebaceous glands, and sudoriferous glands.
reticular
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What are the three pigments that impart a wide variety of colors to the skin?
Melanin, hemoglobin, and carotene
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What causes the skin’s color to vary from pale yellow to reddish-brown to black?
The amount of melanin
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Where is the difference between the two forms of melanin, pheomelanin (yellow to red) and eumelanin (brown to black), most apparent?
In the hair
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What are melanocytes?
The melanin-producing cells
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Where are melanocytes most plentiful?
In the epidermis of the penis, nipples, areas just around the nipples (areolae), face, and limbs
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Where else are melanocytes present?
In mucous membranes
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Why do differences in skin color occur if the number of melanocytes is about the same in all people?
Due mainly to the amount of pigment the melanocytes produce and transfer to keratinocytes
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In some people who are genetically predisposed, where does melanin accumulate?
In patches called freckles
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What are freckles?
Reddish or brown patches of melanin that tend to be more visible in the summer than the winter
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What are age (liver) spots?
Flat blemishes that look like freckles and range in color from light brown to black
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What causes age spots?
Accumulations of melanin that build up over time due to exposure to sunlight
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How are age spots different from freckles?
They are darker than freckles, build up over time, and do not fade away during winter months
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In which age group are age spots more common?
Adults over 40
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What is a nevus (mole)?
A round, flat, or raised area that represents a benign localized overgrowth of melanocytes
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When do nevi (moles) usually develop?
During childhood or adolescence
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What do melanocytes synthesize melanin from?
The amino acid tyrosine
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What enzyme is required for the synthesis of melanin?
Tyrosinase
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Where does the synthesis of melanin occur?
In an organelle called a melanosome
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What increases enzymatic activity within melanosomes and melanin production?
Exposure to ultraviolet (UV) light
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What effect does UV exposure have on melanin?
It increases both the amount and darkness of melanin, giving the skin a tanned appearance
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How does melanin protect the body against further UV radiation?
It absorbs UV radiation, prevents damage to DNA in epidermal cells, and neutralizes free radicals that form in the skin
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What happens to melanin production in response to DNA damage?
It increases
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Why is exposing the skin to a small amount of UV light necessary?
To begin the process of vitamin D synthesis
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What is the risk of repeatedly exposing the skin to a large amount of UV light?
It may cause skin cancer
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Why is a tan lost over time?
Because melanin-containing keratinocytes are shed from the stratum corneum
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Why do dark-skinned individuals have a skin color ranging from yellow to reddish-brown to black?
Because they have large amounts of melanin in the epidermis
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Why do light-skinned individuals appear pink to red in skin color?
Because they have little melanin in the epidermis, making the epidermis translucent and showing the oxygen content of blood in capillaries
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What gives the skin a red color?
Hemoglobin, the oxygen-carrying pigment in red blood cells
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What is carotene?
A yellow-orange pigment that gives egg yolks and carrots their color
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What is carotene a precursor of?
Vitamin A
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What is vitamin A used for?
To synthesize pigments needed for vision
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Where is carotene stored?
In the stratum corneum and fatty areas of the dermis and subcutaneous tissue
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What causes the skin to turn orange?
Excessive dietary intake of carotene-rich foods
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How can an orange skin tone caused by excess carotene be reversed?
By decreasing carotene intake
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What is albinism?
The inherited inability of an individual to produce melanin
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What are albinos?
People affected by albinism
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Why are albinos unable to produce melanin?
Because their melanocytes are unable to synthesize tyrosinase
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What is missing from the hair, eyes, and skin of individuals with albinism?
Melanin
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What problems do individuals with albinism experience?
Problems with vision and a tendency of the skin to burn easily on overexposure to sunlight
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What is vitiligo?
The partial or complete loss of melanocytes from patches of skin, producing irregular white spots
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What causes the loss of melanocytes in vitiligo?
An immune system malfunction in which antibodies attack the melanocytes
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What can the color of skin and mucous membranes provide clues for?
Diagnosing certain conditions
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What happens when blood is not picking up an adequate amount of oxygen from the lungs?
The mucous membranes, nail beds, and skin appear bluish or cyanotic
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What is the term for a bluish appearance of mucous membranes, nail beds, and skin due to lack of oxygen?
Cyanotic
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What is jaundice?
A condition due to a buildup of the yellow pigment bilirubin in the skin
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What color does jaundice give to the skin and whites of the eyes?
Yellowish
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What condition does jaundice usually indicate?
Liver disease
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What is erythema?
Redness of the skin caused by engorgement of capillaries in the dermis with blood
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What causes erythema?
Skin injury, exposure to heat, infection, inflammation, or allergic reactions
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What is pallor?
Paleness of the skin
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In what conditions may pallor occur?
Shock and anemia
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In whom are skin color changes observed most readily?
People with light-colored skin
243
Where can circulation be observed in individuals with darker skin?
The nail beds and gums
244
What is tattooing?
A permanent coloration of the skin in which a foreign pigment is deposited with a needle into macrophages in the dermis
245
Where is the pigment deposited during tattooing?
Into macrophages in the dermis
246
When is it believed that tattooing originated?
Between 4000 and 2000 B.C. in ancient Egypt
247
How many U.S. college students are estimated to have one or more tattoos?
About one in three
248
How are tattoos created?
By injecting ink with a needle that punctures the epidermis, moves between 50 and 3000 times per minute, and deposits the ink in the dermis
249
Why are tattoos permanent?
Because the dermis is stable, unlike the epidermis, which is shed about every four to six weeks
250
Why can tattoos fade over time?
Due to exposure to sunlight, improper healing, picking scabs, and flushing away of ink particles by the lymphoid system
251
What are some uses of tattoos besides body art?
Landmarks for radiation and permanent makeup (eyeliner, lip liner, lipstick, blush, and eyebrows)
252
What are some risks of tattoos?
Infections (staphylococcal infections, impetigo, and cellulitis)
253
How can tattoos be removed?
By lasers, which use concentrated beams of light
254
What happens during laser tattoo removal?
The tattoo inks and pigments selectively absorb high-intensity laser light without destroying normal surrounding skin tissue
255
How does the immune system help in tattoo removal?
The laser causes the tattoo to dissolve into small ink particles that are eventually removed by the immune system
256
What are some downsides to laser tattoo removal?
It involves a considerable investment in time and money, can be quite painful, and may result in scarring and discoloration
257
What is body piercing?
The insertion of jewelry through an artificial opening
258
Who practiced body piercing in ancient times?
Egyptian pharaohs and Roman soldiers
259
How many U.S. college students are estimated to have had a body piercing?
About one in two
260
What steps does a piercer take before inserting body jewelry?
Cleans the skin with an antiseptic, retracts the skin with forceps, and pushes a needle through the skin
261
How long can total healing of a body piercing take?
Up to a year
262
What are some common piercing locations?
Ears, nose, eyebrows, lips, tongue, nipples, navel, and genitals
263
What are some complications of body piercing?
Infections, allergic reactions, and anatomical damage (such as nerve damage or cartilage deformation)
264
How can body piercing jewelry interfere with medical procedures?
It may interfere with resuscitation masks, airway management, urinary catheterization, radiographs, and delivery of a baby
265
Why must body piercing jewelry be removed before certain medical procedures?
Because it can interfere with specific medical equipment and procedures
266
What are the accessory structures of the skin?
Hair, skin glands, and nails
267
Where do the accessory structures of the skin develop from?
The embryonic epidermis
268
What is the function of hair and nails?
To protect the body
269
What is the function of sweat glands?
To help regulate body temperature
270
What are hairs also called?
Pili
271
Where are hairs not present on the body?
Nipples, the palms, palmar surfaces of the fingers, the soles, plantar surfaces of the toes, labia minora, and prepuce of the penis
272
Where is hair most heavily distributed in adults?
Scalp, eyebrows, axillae (armpits), and around the external genitals
273
What largely determines the thickness and pattern of hair distribution?
Genetic and hormonal influences
274
How does hair on the head protect the scalp?
Guards the scalp from injury and the sun’s rays, and decreases heat loss
275
What is the function of eyebrows and eyelashes?
Protect the eyes from foreign particles
276
How does hair in the nostrils and external acoustic meatus function?
Defends those structures from foreign particles
277
What activates touch receptors (hair root plexuses)?
Whenever a hair is moved even slightly
278
What is another function of hairs besides protection?
Sensing light touch
279
are growths of epidermis composed of dead, keratinized epidermal cells.
Hairs
280
What is each hair composed of?
Columns of dead, keratinized epidermal cells bonded together by extracellular proteins
281
What is the hair shaft?
The superficial portion of the hair, which projects above the surface of the skin
282
What is the hair root?
The portion of the hair deep to the shaft that penetrates into the dermis and sometimes into the subcutaneous tissue
283
What are the three concentric layers of cells in the shaft and root of the hair?
Medulla, cortex, and cuticle of the hair
284
What is the inner medulla composed of?
Two or three rows of irregularly shaped cells that contain large amounts of pigment granules in dark hair, small amounts of pigment granules in gray hair, and a lack of pigment granules with air bubbles in white hair
285
What forms the major part of the shaft?
The middle cortex
286
What does the cuticle of the hair consist of?
A single layer of thin, flat cells that are the most heavily keratinized
287
How are cuticle cells on the shaft arranged?
Like shingles on the side of a house, with their free edges pointing toward the end of the hair
288
What surrounds the root of the hair?
The hair follicle
289
What are the two parts of the hair follicle?
External root sheath and internal root sheath
290
What is the external root sheath?
A downward continuation of the epidermis
291
What is the internal root sheath produced by?
The matrix
292
What is the epithelial root sheath?
The combination of the external and internal root sheath
293
What is the dense dermis surrounding the hair follicle called?
The dermal root sheath
294
What is the onion-shaped structure at the base of each hair follicle and its surrounding dermal root sheath?
The hair bulb
295
What does the papilla of the hair contain?
Areolar connective tissue and many blood vessels that nourish the growing hair follicle
296
What is the hair matrix?
A germinal layer of cells responsible for hair growth and replacement
297
What are hair matrix cells responsible for?
The growth of existing hairs and the production of new hairs when old hairs are shed
298
What do hair matrix cells also give rise to?
The cells of the internal root sheath
299
What are the sebaceous glands and a bundle of smooth muscle fibers associated with?
Hairs
300
What is the arrector muscle of the hair?
A bundle of smooth muscle fibers that extends from the papillary dermis to the dermal root sheath around the base of the hair follicle
301
What happens under physiological or emotional stress?
Autonomic nerve endings stimulate the arrector muscles of the hair to contract, pulling the hair shafts perpendicular to the skin surface
302
What causes “goose bumps” or “gooseflesh”?
The contraction of arrector muscles, forming slight elevations in the skin around the hair shaft
303
What forms a hair root plexus?
Dendrites of neurons surrounding each hair follicle
304
What is the function of the hair root plexus?
It is sensitive to touch and generates nerve impulses when the hair shafts are moved
305
What is a substance that removes hair called?
Depilatory
306
What does a depilatory do?
It dissolves the protein in the hair shaft, turning it into a gelatinous mass that can be wiped away.
307
Why does regrowth of the hair occur after using a depilatory?
Because the hair root is not affected.
308
What is electrolysis?
An electric current used to destroy the hair matrix so the hair cannot regrow.
309
What other treatment may also be used to remove hair?
Laser treatments
310
What are the stages of the growth cycle of a hair follicle?
Growth stage, regression stage, and resting stage.
311
What happens during the growth stage?
Cells of the hair matrix divide, new cells are added to the base of the hair root, pushing existing cells upward, making the hair grow longer.
312
What happens to the cells of the hair as they are pushed upward?
They become keratinized and die.
313
When is hair most receptive to hair removal?
During the growth stage.
314
What characterizes the regression stage?
Movement of the hair away from the blood supply in the papilla of the hair, stopping cell division, atrophy of the hair follicle, and cessation of hair growth.
315
What happens during the resting stage?
The old hair root falls out or is pushed out of the hair follicle.
316
What happens after the resting stage?
A new growth stage begins.
317
How long does scalp hair stay in the growth stage?
2 to 6 years.
318
How long does scalp hair stay in the regression stage?
2 to 3 weeks.
319
How long does scalp hair stay in the resting stage?
About 3 months.
320
At any time, what percentage of scalp hairs are in the growth stage?
About 85%.
321
Is visible hair alive?
No, visible hair is dead, but portions of its root within the scalp are alive until pushed out by a new hair.
322
What is the normal hair loss in the adult scalp per day?
About 70–100 hairs per day.
323
What factors can alter the rate of growth and replacement cycle of hair?
Illness, radiation therapy, chemotherapy, age, genetics, gender, and severe emotional stress.
324
What types of diets increase hair loss?
Rapid weight-loss diets that severely restrict calories or protein.
325
How long does increased hair shedding last after childbirth?
Three to four months.
326
What is alopecia?
The partial or complete lack of hair.
327
What are some causes of alopecia?
Genetic factors, aging, endocrine disorders, chemotherapy, or skin disease.
328
What is chemotherapy?
The treatment of disease, usually cancer, by means of chemical substances or drugs.
329
What do chemotherapeutic agents do?
They interrupt the life cycle of rapidly dividing cancer cells.
330
Why does chemotherapy cause hair loss?
Because the drugs also affect other rapidly dividing cells in the body, such as the hair matrix cells.
331
Why are some hair matrix cells not affected by chemotherapy?
Because about 15 percent of the hair matrix cells of scalp hairs are in the resting stage.
332
What happens to hair growth after chemotherapy is stopped?
The hair matrix cells replace lost hair follicles, and hair growth resumes.
333
What are some other side effects of chemotherapy?
Red bone marrow suppression (which can result in infections, bleeding problems, and anemia), nausea and vomiting, appetite and weight changes, diarrhea or constipation, fatigue, nervous system disorders, genital disorders, and liver and kidney damage.
334
What is the color of hair primarily due to?
The amount and type of melanin in its keratinized cells.
335
What synthesizes melanin in the hair?
Melanocytes scattered in the matrix of the bulb.
336
Where does melanin pass into after being synthesized?
Into the cells of the cortex and medulla of the hair.
337
What type of melanin does dark-colored hair mostly contain?
Eumelanin (brown to black).
338
What type of melanin do blond and red hair contain?
Variants of pheomelanin (yellow to red).
339
Why does hair become gray?
Because of a progressive decline in melanin production.
340
What does gray hair contain?
Only a few melanin granules.
341
Why does white hair occur?
Due to the lack of melanin and the accumulation of air bubbles in the shaft.
342
What does hair coloring do?
It adds or removes pigment.
343
What do temporary hair dyes do?
They coat the surface of a hair shaft and usually wash out within 2 or 3 shampoos.
344
How long does it take for temporary hair dye to wash out?
Within 2 or 3 shampoos.
345
How do semipermanent hair dyes affect the hair?
They penetrate the hair shaft moderately and fade and wash out after about 5 to 10 shampoos.
346
How long does it take for semipermanent dyes to wash out?
After about 5 to 10 shampoos.
347
How do permanent hair dyes affect the hair?
They penetrate deeply into the hair shaft and don’t wash out but are eventually lost as the hair grows out.
348
When do males develop the typical male pattern of hair growth?
At puberty.
349
What causes males to develop a beard and a hairy chest?
Significant quantities of androgens secreted by the testes.
350
What produces small quantities of androgens in females at puberty?
The ovaries and the suprarenal glands.
351
What do androgens promote in females?
Hair growth throughout the body, including the axillae and pubic region.
352
What happens if a tumor of the suprarenal glands, testes, or ovaries produces an excessive amount of androgens?
Hirsutism, excessive body hair or body hair in areas that usually are not hairy.
353
What is hirsutism?
Excessive body hair or body hair in areas that usually are not hairy.
354
What must be present for the most common form of baldness to occur?
Androgens.
355
What is another name for androgenic alopecia?
Male-pattern baldness.
356
How do androgens affect hair growth in genetically predisposed adults?
They inhibit hair growth.
357
How does male-pattern baldness typically begin in men?
With a receding hairline followed by hair loss in the temples and crown.
358
How does male-pattern baldness typically affect women?
They are more likely to have thinning of hair on top of the head.
359
What was the first drug approved for enhancing scalp hair growth?
Minoxidil (Rogaine).
360
What does minoxidil cause?
Vasodilation (widening of blood vessels), increasing circulation, direct stimulation of hair follicle cells to pass into growth stage follicles, and inhibition of androgens.
361
How does minoxidil improve hair growth?
It causes scalp follicles to enlarge and lengthens the growth cycle.
362
How many people benefit from minoxidil?
About a third of the people who try it.
363
Does minoxidil help people who are already bald?
No, it does not.
364
What are glands?
Epithelial cells that secrete a substance.
365
What kinds of exocrine glands are associated with the skin?
Sebaceous glands, sudoriferous glands, and ceruminous glands.
366
What are mammary glands?
Specialized sudoriferous glands that secrete milk.
367
What are sebaceous glands?
Simple, branched acinar (rounded) glands.
368
What is another name for sebaceous glands?
Oil glands.
369
To what are sebaceous glands usually connected?
Hair follicles.
370
Where does the secreting portion of a sebaceous gland lie?
In the dermis.
371
Where does the sebaceous gland usually open?
Into the neck of a hair follicle.
372
In which locations do sebaceous glands open directly onto the skin surface?
Lips, glans penis, labia minora, and tarsal glands of the eyelids.
373
Where are sebaceous glands absent?
Palms, palmar surfaces of the digits, soles, and plantar surfaces of the toes.
374
Where are sebaceous glands small?
Most areas of the trunk and limbs.
375
Where are sebaceous glands large?
Skin of the breasts, face, neck, and superior chest.
376
What oily substance do sebaceous glands secrete?
Sebum.
377
What is sebum composed of?
Triglycerides, cholesterol, proteins, and inorganic salts.
