1
Q
what are the functions of the integumentary system?
A
- helps maintain a constant body temperature
- protects the body from external environment
- provides sensory information about the surrounding environment
- indicates homeostatic imbalances in the body
- reveals systemic infections or diseases on internal organs
- excretes and absorbs substances
- synthesizes Vit D
2
Q
what is dermatology?
A
the medical specialty that deals with the structure, function, and disorders of the integumentary system
3
Q
what is the skin?
A
cutaneous membrane, covers the external surface of the body and is by weight the largest organ of the body in weight
4
Q
what are the two main parts of the skin?
A
epidermis: superficial, thinner portion, which is composed of epithelial tissue
dermis: deeper, thicker connective tissue portion
5
Q
what is the subcutaneous tissue?
A
- consists of areolar and adipose tissues
- Fibers that extend from the dermis anchor the skin to the subcutaneous tissue, which in turn attaches to underlying fascia, the connective tissue around muscles and bones
- serves as a storage depot for fat and contains large blood vessels that supply the skin
6
Q
what are lamellar corpuscles?
A
nerve endings that are sensitive to pressure, high frequency vibrations
7
Q
what kind of tissue is the epidermis composed of?
A
keratinized stratified squamous epithelium
8
Q
what four types of cells are found in the epidermis?
A
- keratinocytes
- melanocytes
- dendritic cells
- tactile epithelial cells
9
Q
what are keratinocytes?
A
- produce keratin
- produce lamellar granules
10
Q
what is keratin?
A
tough, fibrous protein
- helps protect the skin and underlying tissues from abrasions, heat, microbes, and chemicals
11
Q
what are lamellar granules?
A
membrane-enclosed, fuses with plasma membrane to release a lipid-rich water-repellent sealant that decreases water entry and loss, inhibits the entry of foreign materials
12
Q
what are melanocytes?
A
- produce melanin
- long, slender pseudopods extend btwn the keratinocytes and transfer melanin granules to them
13
Q
what is melanin?
A
- yellow-red or brown-black pigment that contributes to skin color and absorbs damaging ultraviolet (UV) light
- melanin granules cluster to form a protective veil over the nucleus to shield the nuclear DNA from damage by UV light
- neutralizes free radicals that form in skin after damage by UV radiation
14
Q
what are dendritic cells?
A
- arise from red bone marrow and migrate to the epidermis
- participate in immune responses against microbes that invade the skin
- help other cells of the immune system recognize an invading microbe and destroy it
15
Q
what are tactile epithelial cells?
A
- located in deepest layer of epidermis
- make contact with nonencapsulated sensory corpuscles
- detect touch sensations
16
Q
what is the stratum basale?
A
- deepest layer of epidermis
- composed of single row of cuboidal/columnar epithelial cells
- some are epidermal stem cells that produce new keratinocytes
17
Q
what are tonofilaments?
A
keratin intermediate filaments
- compose the cytoskeleton within keratinocytes of stratum basale
- attaches to desmosomes, hemidesmosomes and attaches cells in stratum basale tgt
18
Q
what are skin grafts?
A
the transfer of a patch of healthy skin taken from a donor site to cover a wound
19
Q
what types of cells/structures are found in stratum basale?
A
- epidermal stem cells
- new daughter cuboidal/columnar keratinocytes
- melanocytes
- tactile epithelial cells and nonencapsulated sensory corpuscles
- tonofilaments
20
Q
why are skin grafts performed?
A
- to protect against fluid loss and infection
- to promote tissue healing
- to reduce scar formation
- to prevent loss of function
- cosmetic reasons
21
Q
what is an autograft?
A
skin graft from skin from same individual
22
Q
what is an isograft?
A
skin graft of skin from an identical twin
23
Q
why are transplanted skin usually taken from same individual/identical twin?
A
to avoid tissue rejection
24
Q
what is an autologous skin transplantation?
A
small amts of individual’s epidermis removed, keratinocytes cultured to produce thin sheets of skin
- performed when skin damage extensive that autograft would cause harm
- usually for severely burned patients
25
what is the stratum spinosum?
- mainly consists of numerous keratinocytes arranged in 8–10 layers
- Cells in the more superficial layers become somewhat flattened
- keratinocytes of the stratum spinosum produce coarser bundles of keratin in intermediate filaments
- strong and flexible because at each spinelike projection, bundles of keratin intermediate filaments insert into desmosomes, which tightly join the cells to one another
26
what types of cells/structures are found in the stratum spinosum?
- keratinocytes
- coarser bundles of keratin in intermediate filaments
- dendritic cells
- projections of melanocytes
27
what is the stratum granulosum?
- consists of three to five layers of flattened keratinocytes that are undergoing apoptosis
- nuclei and other organelles of these cells begin to degenerate as they move farther from their source of nutrition
- marks the transition between the deeper, metabolically active strata and the dead cells of the more superficial strata
28
what is keratohyalin?
darkly staining granules, assembles keratin intermediate filaments into keratin
29
what is apoptosis?
orderly, genetically programmed cell death in which the nucleus fragments before the cells die
30
what is the stratum lucidum?
- present only in thick skin
- four to six layers of flattened, clear, dead keratinocytes with thick plasma membranes and large amounts of keratin
- additional level of toughness
31
where is thick skin found?
- palms
- palmar surfaces of digits, soles
- plantar surfaces of toes
32
what is the stratum corneum?
- consists on average of 25 to 30 layers of flattened, extremely thin dead keratinocytes
- cells continuously shed and replaced by cells from deeper strat
- multiple layers protect deeper strata from injury and microbial invasion
- constant exposure to friction increases cell and keratin production
33
how are keratinocytes in stratum corneum different?
- extremely thin
- no longer have nucleus or internal organelles
34
what is a callus?
abnormal thickening of the stratum corneum due to constant exposure to friction and abrasion
35
what is keratinization?
cells accumulate more and more keratin as keratinocytes move from one epidermal layer to the next
36
why are the cells in the stratum basale the ones that undergo cellular division and replace the dead keratinocytes?
stratum basale is closest to highly vascular dermis
- receives most of nutrients and oxygen
- most active metabolically
- as cells pushed farther from basale, blood supply cut off
37
when does the rate of cell division in stratum basale increase?
when the outer layers of the epidermis are stripped away
ex. abrasions and burns
38
what is psoriasis?
- skin disorder in which keratinocytes divide and move more quickly than normal from the stratum basale to the stratum corneum
- immature keratinocytes make an abnormal keratin, which forms flaky, silvery scales at the skin surface, most often on the knees, elbows, and scalp
- cell division must be suppressed, keratinization inhibited to effectively treat
39
what is the dermis composed of?
dense irregular connective tissue containing collagen and elastic fibers, blood vessels
40
what cells are found in the dermis?
- fibroblasts
- macrophages
- adipocytes near subcutaneous tissue
41
what are the various properties of the dermis?
- woven network of fibers has great tensile strength (resists pulling or stretching forces)
- has the ability to stretch and recoil easily
- has blood vessels that supply nutrient/waste exchange with epidermis
42
what are the two different layers of the dermis?
- papillary dermis
- reticular dermis
43
what is the papillary dermis?
- contains thin collagen and fine elastic fibers
- surface area is greatly increased by dermal papillae
- All dermal papillae contain capillary loops
- some contain tactile corpuscles and free nerve endings
44
what are dermal papillae?
small, nipple-shaped structures that project into the undersurface of the epidermis
45
what are tactile corpuscles?
nerve endings found in a dermal papilla that are sensitive to touch
46
what are free nerve endings?
dendrites that lack any apparent structural specialization
- Different free nerve endings initiate signals that give rise to sensations of warmth, coolness, pain, tickling, and itching
47
what is the reticular dermis?
- attached to the subcutaneous tissue, contains bundles of thick collagen fibers, scattered fibroblasts, and various wandering cells (such as macrophages)
- collagen fibers in the reticular dermis are arranged in a netlike manner and have a more regular arrangement than those in the papillary dermis, helps skin resist stretching
48
what kinds of cells and structures are found in the reticular dermis?
- thick collagen fibres with regular netlike arrangement
- fibroblasts
- wandering cells
- adipocytes
49
what kinds of structures occupy the spaces between the fibres in the reticular fibre?
Blood vessels, nerves, hair follicles, sebaceous glands, and sudoriferous glands
50
what gives skin its strength, extensibility, and elasticity
the combination of collagen and elastic fibres with netlike, regular arrangement in the reticular dermis
51
what results in striae/stretch marks?
the internal damage to the collagenous, vascular dermis that occurs when the skin is stretched too much
- lateral bonding between adjacent collagen fibers is disrupted and small dermal blood vessels rupture
52
what are epidermal ridges?
- series of elevations that appear either as straight lines or as a pattern of loops and whorls
- found on thick skin
- produced during the 3rd month of fetal development
- genetically determined and is unique for each individual
53
what is the function of epidermal ridges?
- increase the surface area of the epidermis and thus increase the grip of the hand or foot by increasing friction
- increases the number of corpuscles of touch and thus increases tactile sensitivity
54
why is the jigsaw puzzle-like connection of the dermal papillae and epidermal pegs important?
- strengthens the skin against forces that move epidermis and dermis in opposite directions
55
what are the three pigments that impart a wide variety of colors to skin?
- carotene
- melanin
- hemoglobin
56
what are the two types of melanin?
pheomelanin and eumelanin
57
what is pheomelanin?
yellow to red form of melanin
58
what is eumelanin?
brown to black form of melanin
59
what is differences in skin colour mainly due to?
- the number of melanocytes is about the same in all people
- differences in skin color are due mainly to the amount of pigment the melanocytes produce and transfer to keratinocytes
60
what are freckles?
patches of melanin accumulations
61
what is a nevus?
a mole; a round, flat, or raised area that represents a benign localized overgrowth of melanocytes
62
what amino acid do melanocytes synthesize melanin from? in the presence of what enzyme?
tyrosine, in the presence of tyrosinase
63
where does melanin synthesis occur?
in melanosomes
64
what does exposure to UV light do in melanocytes?
- increases the enzymatic activity within melanosomes and thus increases melanin production
- Both the amount and darkness of melanin increase on UV exposure
65
how is a tan lost?
when the melanin-containing keratinocytes are shed from the stratum corneum
66
what is albinism?
the inherited inability of an individual to produce melanin
- melanocytes unable to synthesize tyrosinase
67
what is vitiligo?
the partial or complete loss of melanocytes from patches of skin produces irregular white spots
- related to an immune system malfunction in which antibodies attack the melanocytes
68
where is carotene stored in the skin?
the stratum corneum, the fatty areas of the dermis and subcutaneous tissue
69
what causes the yellow appearance due to jaundice?
the buildup of bilirubin in the skin
70
what is erythema caused by?
engorgement of capillaries in the dermis with blood due to skin injury, exposure to heat, infection, inflammation, or allergic reactions
71
What is pallor?
paleness of the skin
- may occur due to shock or anemia
72
why might the skin appear cyanotic?
skin may appear blueish due to blood not picking up adequate amount of oxygen
73
what are pili?
hairs, present on most skin surfaces
74
what determines the thickness and pattern of hair distribution?
- genetics
- hormonal influences
75
what functions do pili have?
- limited protection
- decreases heat loss from scalp
- eyebrows and eyelashes protect eyes from foreign particles
- hair root plexuses associated with hair follicles activate whenever hair is moved slightly
- senses light touch
76
what is the hair shaft?
superficial portion of hair, projects above the surface of the skin
77
what is the hair root?
portion of hair deep to the shaft that penetrates into dermis or subcutaneous tissue
78
what are the three layers that make up hair?
- inner medulla
- middle cortex
- outer cuticle
79
what is the hair's medulla?
composed of two or three rows of irregularly shaped cells that contain pigment granules
- may be lacking in thinner hair
80
what is the hair's cortex?
forms the major part of the shaft and consists of elongated cells
81
what is the hair's cuticle?
outermost layer, consists of a single layer of thin, flat cells that are the most heavily keratinized
82
what is the hair follice?
structure composed of epithelium, surrounds the root of a hair from which hair develops
83
what is the hair follicle made up of?
- internal root sheath
- external root sheath
84
what is the external root sheath?
downward continuation of the epidermis
85
what is the internal root sheath?
produced by the matrix
- forms a cellular tubular sheath of epithelium between the external root sheath and the hair
86
what is the hair matrix similar to?
the stratum basale, it is where new hair cells grow from
87
what is the hair matrix?
germinal layer of cells, the epidermal stem cells are the site of cellular division of the hair
- grows hair, replaces old hair, develops internal root sheath cells
88
what is the hair bulb?
onion-shaped structure at the base of each hair follicle and its surrounding dermal root sheath
89
what is a depilatory?
a substance that removes hair by dissolving the proteins in the hair shaft, turning them into a gelatinous mass that can be wiped away
90
why do laser treatments and electrolysis affect regrowth of hair?
electric currents and alsers destroy the hair matrix so hair cannot regrow
91
what is the arrector muscle of the hair?
smooth muscle that extends from papillary dermis of skin to the dermal root sheath around hair's base
92
what happens to arrector pili muscles when under physiological or emotional stress?
autonomic nerve endings stimulate the arrector muscles of the hair to contract, which pulls the hair shafts perpendicular to the skin surface
93
what is the hair's position when the arrector pili muscles are in their normal position?
hair emerges at a less than 90 degree angle to the surface of the skin
94
what are hair root plexuses?
network of dendrites arranged around the root of a hair as free or naked nerve endings that generate nerve impulses
- stimulated when a hair shaft is moved
95
what are the stages in the growth cycle of a hair follicle?
- growth stage
- regression stage
- resting stage
96
what happens in the growth stage of a hair follicle?
- cells of the hair matrix divide
- As new cells from the hair matrix are added to the base of the hair root, existing cells of the hair root are pushed upward and the hair grows longer
- While the cells of the hair are being pushed upward, they become keratinized and die
- hair is most receptive to hair removal
97
what happens in the regression stage of a hair follicle?
- movement of the hair away from the blood supply in the papilla of the hair
- cells of the hair matrix stop dividing, the hair follicle atrophies (shrinks), and the hair stops growing
98
what happens in the resting stage of a hair follicle?
the old hair root falls out or is pushed out of the hair follicle
99
what can alter the rate of growth and replacement cycle of the hair follicles?
illness, radiation therapy, chemotherapy, age, genetics, gender, and severe emotional stress
100
what is alopecia?
the partial or complete lack of hair, may result from genetic factors, aging, endocrine disorders, chemotherapy, or skin disease
101
what are lanugo?
fine downy nonpigmented hairs that cover the fetus
102
what are terminal hairs?
long, coarse, heavily pigmented hairs
103
what are vellus hairs?
peach fuzz, short, fine, pale hairs that are barely visible to the naked eye
104
what is hirsutism?
excessive body hair in areas that usually are not hairy, result of excessive amount of androgens
105
what is androgenic alopecia?
male-pattern baldness, result of androgens inhibiting hair growth
106
what are the exocrine glands associated with the skin?
- sebaceous glands
- sudoriferous glands
- ceruminous glands
107
what are sebaceous glands?
oil glands
- simple branched acinar glands
- connected to hair follicles
- secreting portion lies in dermis and usually opens into neck of a hair follicle
- secretes sebum
108
what is sebum?
oily substance secreted by sebaceous glands
- mix of triglycerides, cholesterol, proteins, inorganic salts
- coats the surface of hairs preventing them from drying or becoming brittle
- prevents excessive evaporation of water
- inhibits growth of some bacteria
109
what is acne?
an inflammation of sebaceous glands that usually begins at puberty, when the sebaceous glands are stimulated by androgens
- occurs predominantly in sebaceous follicles that have been colonized by bacteria, some of which thrive in the lipid-rich sebum
110
what are sudoriferous glands?
sweat glands
- release sweat, or perspiration, into hair follicles or onto the skin surface through pores
- eccrine or apocrine sweat glands
111
what are eccrine sweat glands?
- simple, coiled tubular glands
- more common than apocrine sweat glands
- secretory portion of eccrine sweat glands is located mostly in the reticular dermis
- excretory duct ends as a pore at the surface of the epidermis
112
what is the function of eccrine sweat glands?
- help regulate body temperature through evaporation
- thermoregulatory sweating
113
what is insensible perspiration?
Sweat that evaporates from the skin before it is perceived as moisture
114
what is sensible perspiration?
Sweat that is excreted in larger amounts and is seen as moisture on the skin
115
what is emotional sweating?
- cold sweat
- Eccrine sweat glands also release sweat in response to an emotional stress such as fear or embarrassment
116
what are apocrine sweat glands?
- coiled tubular glands but have larger ducts and lumens than eccrine glands
- secretory portion of these sweat glands is located in the reticular dermis or upper subcutaneous tissue
- excretory duct opens into hair follicles
117
where are apocrine sweat glands found?
- found mainly in the skin of the axilla (armpit),
- groin,
- areolae (pigmented areas around the nipples) of the breasts
- bearded regions of the face in adult males
118
where are eccrine sweat glands found?
skin of the forehead, palms, and soles
- distributed throughout skin of most regions of body
119
where are eccrine sweat glands not found?
in the margins of the lips, nail beds of the fingers and toes, glans penis, glans clitoris, labia minora, or eardrums
120
why does apocrine sweat appear milky or yellowish?
- Apocrine sweat contains the same components as eccrine sweat plus lipids and proteins
- odorless, but apocrine sweat interacts with bacteria on the surface of the skin, the bacteria metabolize its components, causing apocrine sweat to have a musky odor that is often referred to as body odor
121
when do apocrine sweat glands secrete apocrine sweat?
- active during emotional sweating
- during sexual activities
- do not play a role in thermoregulatory sweating
122
what are ceruminous glands?
modified sweat glands in ear that produce waxy lubricating secretion
- excretory ducts open either directly onto the surface of the external acoustic meatus (ear canal) or into ducts of sebaceous glands
- combined secretion of ceruminous and sebaceous glands is cerumen/earwax
123
what is cerumen? what does it do for the ear?
earwax
- provides a sticky barrier that impedes the entrance of foreign bodies and insects
- waterproofs the meatus and prevents bacteria and fungi from entering cells
124
what are nails?
plates of tightly packed, hard, dead, keratinized epidermal cells that form a clear, solid covering over the dorsal surfaces of the distal portions of the digits
125
what does each nail consist of?
nail plate, a free edge, and a nail root
126
what is the nail plate?
visible portion of the nail
- comparable to the stratum corneum of the epidermis of the skin, with the exception that its flattened, keratinized cells fill with a harder type of keratin and the cells are not shed
- Below it is a region of epithelium and a deeper layer of dermis
127
why does the nail plate appear pink?
blood flowing through the capillaries in the underlying dermis
128
what is the free edge of the nail plate?
part of the nail plate that may extend past the distal end of the digit
- white because there are no underlying capillaries
129
what is the nail root?
portion of the nail that is buried in a fold of skin
130
what is the lunule of the nail?
- whitish, crescent-shaped area of the proximal end of the nail plate
- white appearance is due to the thick opaque layer of partially keratinized matrix cells
131
what is the hyponychium?
- thickened region of stratum corneum
- junction between the free edge and skin of the fingertip and secures the nail to the fingertip
132
what is the nail bed?
skin below the nail plate that extends from the lunula to the hyponychium
- epidermis of the nail bed lacks a stratum granulosum
133
what is the eponychium?
cuticle
- narrow band of epidermis that extends from and adheres to the margin (lateral border) of the nail wall
- occupies the proximal border of the nail and consists of stratum corneum
134
when are sebaceous glands active?
Relatively inactive during childhood; activated during puberty.
135
when are eccrine sweat glands active?
soon after birth
136
when are apocrine sweat glands active?
puberty
137
when are ceruminous glands active?
soon after birth
138
what is the function of sebaceous glands?
Prevent hairs from drying out, prevent water loss from skin, keep skin soft, inhibit growth of some bacteria.
139
what is the function of eccrine sweat glands?
Regulation of body temperature, waste removal; stimulated during emotional stress.
140
what is the function of apocrine sweat glands?
Stimulated during emotional stress and sexual excitement.
141
what is the function of ceruminous glands?
Impede entrance of foreign bodies and insects into external acoustic meatus, waterproof meatus, prevent microbes from entering cells.
142
what are the treatments for impacted cerumen?
periodic ear irrigation with enzymes to dissolve the wax and removal of wax with a blunt instrument by trained medical personnel.
143
what is the nail matrix?
portion of epithelium proximal to nail root
- superficial nail matrix cells divide mitotically to produce new nail cells
144
what is the growth rate of nails determined by?
- the rate of mitosis in matrix cells, which is influenced by factors such as a person’s age, health, and nutritional status
- Nail growth also varies according to the season, the time of day, and environmental temperature
- the longer the digit the faster the nail grows
145
what are the functions of nails?
1. protect the distal end of the digits.
2. provide support and counterpressure to the palmar surface of the fingers to enhance touch perception and manipulation
3. allow us to grasp and manipulate small objects, and they can be used to scratch and groom the body
146
why does thin skin not have epidermal ridges?
poorly developed, fewer, and less well organized dermal papillae
147
what is thermoregulation?
- the homeostatic regulation of body temperature
- skin releases sweat at its surface and adjusts the flow of blood in the dermis
148
how does sweat help with thermoregulation?
- the evaporation of sweat from the skin surface helps lower body temperature
- production of sweat from eccrine sweat glands is decreased, which helps conserve heat
149
how does regulating blood vessels in dermis help with thermoregulation?
- blood vessels in the dermis of the skin dilate, more blood flows through the dermis, which increases the amount of heat loss from the body
- the blood vessels in the dermis of the skin constrict, decreases blood flow through the skin and reduces heat loss from the body
150
how does the skin act as a blood reservoir?
dermis houses an extensive network of blood vessels that carry 8–10% of the total blood flow in a resting adult
151
how does keratin provide protection to the body?
protects underlying tissues from microbes, abrasion, heat, and chemicals, and the tightly interlocked keratinocytes resist invasion by microbes
152
how do the lamellar granules protect body?
Lipids released by lamellar granules inhibit evaporation of water from the skin surface, thus guarding against dehydration; they also retard entry of water across the skin surface during showers and swims
153
how do sebaceous glands protect the body?
The oily sebum from the sebaceous glands keeps skin and hairs from drying out and contains bactericidal chemicals (substances that kill bacteria)
154
how do the sudoriferous glands protect the body?
The acidic pH of perspiration retards the growth of some microbes
155
how do melanocytes protect the body?
melanin helps shield against the damaging effects of ultraviolet light
156
what are cutaneous sensations?
sensations that arise in the skin, including
tactile sensations: touch, pressure, vibration, and tickling
thermal sensations: such as warmth and coolness
157
what substances can move easily into the skin?
lipid-soluble steroids can move easily into papillary dermis
158
how is vitamin D synthesized?
UV rays activate a precursor molecule found in skin
- enzymes in liver and kidneys modify the activated molecule into calcitriol, the most active form of Vit. D
159
what is calcitriol?
hormone that aids in the absorption of calcium from foods in the gastrointestinal tract into the blood
160
what is the function of Vitamin D?
Vitamin D is believed to enhance phagocytic activity, increase the production of antimicrobial substances in phagocytes, regulate immune functions, and help reduce inflammation
161
what are the two kinds of wound-healing processes can occur?
- epithelial wound healing: affects only epidermis
- deep wound healing: affects dermis
162
what is the skin's response to an epidermal injury?
- epidermal stem cells of the epidermis surrounding the wound break contact with the basement membrane
- cells then enlarge and migrate across the wound
- cells appear to migrate as a sheet until advancing cells from opposite sides of the wound meet
- Migration of the epidermal cells stops completely when each is finally in contact with other epidermal cells on all sides
- epidermal growth factor stimulates basal stem cells to divide and replace the ones that have moved into the wound
163
why do epidermal cells stop migrating when they encounter one another?
contact inhibition
164
what four phases occurs in deep wound healing?
- inflammatory phase
- migratory phase,
- proliferative phase, - maturation phase
165
what happens in the inflammatory phase?
- blood clot forms in the wound and loosely unites the wound edges
- involves inflammation
- vasodilation and increased permeability of blood vessels associated with inflammation enhance delivery of helpful cells:
- neutrophils for phagocytosis
- monocytes which turn into macrophages
- mesenchymal cells which turn into fibroblasts
166
what is inflammation?
localized, protective response due to tissue injury designed to destroy, dilute, or wall of the infecting agent or injured tissue
- redness, pain, swelling, heat, loss of function
167
what is the migratory phase?
- clot becomes a scab, and epithelial cells migrate beneath the scab to bridge the wound
- Fibroblasts migrate along fibrin threads and begin synthesizing scar tissue (collagen fibers and glycoproteins), and damaged blood vessels begin to regrow
- tissue filling the wound is called granulation tissue
168
what is the proliferative phase?
- extensive growth of epithelial cells beneath the scab
- deposition by fibroblasts of collagen fibers in random patterns
- continued growth of blood vessels
169
what is the maturation phase?
- scab sloughs off once the epidermis has been restored to normal thickness
- Collagen fibers become more organized
- fibroblasts decrease in number
- blood vessels are restored to normal
170
what is fibrosis?
the process of scar tissue formation
171
what is a hypertrophic scar?
scar remains within boundary of original wound
172
what is a keloid scar?
scar extends beyond boundary of original wound
173
how does scar tissue differ from normal skin?
- collagen fibres more densely arranged
- decreased elasticity
- fewer blood vessels
- usually lighter in colour than normal skin
174
what is the epidermis derived from?
the ectoderm, which covers the surface of an embryo
175
what is the vernix caseosa?
fatty substance that covers and protects the fetus's skin from constant exposure to the amniotic fluid
- facilitates the birth of the fetus due to its slippery nature
176
what is the dermis derived from?
the mesoderm, located deep to the surface ectoderm
- mesoderm gives rise to mesenchyme
177
Which structures develop as downgrowths of the stratum basale?
Most sudoriferous glands are derived from downgrowths (buds) of the stratum basale of the epidermis into the dermis
178
What is the composition of vernix caseosa?
The peridermal cells are continuously sloughed off, and secretions from sebaceous glands mix with them and hairs to form vernix caseosa
179
how are wrinkles formed?
- Collagen fibers in the dermis begin to decrease in number, stiffen, break apart, and disorganize into a shapeless, matted tangle
- Elastic fibers lose some of their elasticity, thicken into clumps, and fray
- Fibroblasts, which produce both collagen and elastic fibers, decrease in number
180
what are some age-associated changes to the skin?
- wrinkles
- dehydration and cracking
- decreased production of sweat
- decreased melanin
- hair loss, graying
- age spots
- subcutaneous tissue lost
- nails become brittle
181
what is rosacea?
- a skin condition that affects mostly light-skinned adults between the ages of 30 and 60
- redness, tiny pimples, and noticeable blood vessels, usually in the central area of the face
182
what are some cosmetic anti-aging treatments?
- topical products
- microdermabrasion
- chemical peel
- laser resurfacing
- fillers
- fat transplantation
- botox
- facelift
183
what are the three forms of skin cancer?
- basal cell carcinomas
- squamous cell carcinomas
- malignant melanomas
184
what are basal cell carcinomas?
tumors arise from cells in the stratum basale of the epidermis and rarely metastasize
185
what are squamous cell carcinomas?
tumors arise from the stratum spinosum of the epidermis, and they have a variable tendency to metastasize
186
what is malignant melanoma?
tumors that arise from melanocytes
- Malignant melanomas metastasize rapidly and can kill a person within months of diagnosis
187
what are the early warning signs of malignant melanoma?
ABCDE
A: asymmetry, irregular shapes
B: Border is irregular
C: color, uneven and various
D: diameter >6mm
E: evolving size, shape, color
188
what are risk factors for skin cancer?
- skin type
- sun exposure
- family history
- age
- immunological status
189
what is a burn?
tissue damage caused by excessive heat, electricity, radioactivity, or corrosive chemicals that denature (break down) proteins in the skin
190
how does the integumentary system contribute to the skeletal system?
Skin helps activate vitamin D, needed for proper absorption of dietary calcium and phosphorus to build and maintain bones
191
how does the integumentary system contribute to the muscular system?
Skin helps provide calcium ions, needed for muscle contraction
192
how does the integumentary system contribute to the nervous system?
Nerve endings in skin and subcutaneous tissue provide input to brain for touch, pressure, thermal, and pain sensations
193
how does the integumentary system contribute to the endocrine system?
Keratinocytes in skin help activate vitamin D to calcitriol, a hormone that aids absorption of dietary calcium and phosphorus
194
how does the integumentary system contribute to the cardiovascular system?
Local chemical changes in dermis cause widening and narrowing of skin blood vessels, which help adjust blood flow to skin
195
how does the integumentary system contribute to the lymphatic and immune system?
- Skin is first line of defense in immunity, providing mechanical barriers and chemical secretions that discourage penetration and growth of microbes
- Dendritic cells in epidermis participate in immune responses by recognizing and processing foreign antigens
- Macrophages in dermis phagocytize microbes that penetrate skin surface
196
how does the integumentary system contribute to the respiratory system?
- Hairs in nose filter dust particles from inhaled air
- Stimulation of pain nerve endings in skin may alter breathing rate
197
how does the integumentary system contribute to the digestive system?
- Skin helps activate vitamin D to the hormone calcitriol, which promotes absorption of dietary calcium and phosphorus in small intestine
198
how does the integumentary system contribute to the urinary system?
- Kidney cells receive partially activated vitamin D hormone from skin and convert it to calcitriol
- Some waste products are excreted from body in sweat, contributing to excretion by urinary system
199
how does the integumentary system contribute to the reproductive system?
- Nerve endings in skin and subcutaneous tissue respond to erotic stimuli, thereby contributing to sexual pleasure
- Suckling of a baby stimulates nerve endings in skin, leading to milk ejection
- Mammary glands (modified sweat glands) produce milk
- Skin stretches during pregnancy as fetus enlarges
200
what is a first-degree burn?
- involves only the epidermis
- characterized by mild pain and erythema (redness) but no blisters
- Skin functions remain intact
- partial-thickness burns
201
what is a second-degree burn?
- destroys the epidermis and part of the dermis
- some skin functions lost
- redness, blister formation, edema, and pain
- blisters: epidermis separates from the dermis due to the accumulation of tissue fluid between them
- Associated structures, such as hair follicles, sebaceous glands, and sweat glands, usually are not injured
- partial-thickness burns
- scarring may result
202
what is a third-degree burn?
- full-thickness burn
- destroys the epidermis, dermis, and subcutaneous tissue
- most skin functions are lost
- vary in appearance from marble-white to mahogany colored to charred, dry wounds
- burned region is numb because sensory nerve endings have been destroyed
203
why are systemic effects of a major burn a greater threat to life than the local effect of the burn?
systemic effects of a burn may include (1) a large loss of water, blood plasma, and blood plasma proteins, which causes shock; (2) bacterial infection; (3) reduced circulation of blood; (4) decreased production of urine; and (5) diminished immune responses
204
what are pressure ulcers?
decubitus ulcers, bedsores
- caused by a constant deficiency of blood flow to tissues
- the affected tissue overlies a bony projection that has been subjected to prolonged pressure against an object such as a bed, cast, or splint
205
Where did the dust originate on the human body?
dust particles are primarily keratinocytes that are shed from the stratum corneum of the skin
206
Josie reassures her mother that the tattoo she received at the tattoo parlor will eventually disappear. She knows this because she has learned in biology class that skin cells are shed every four weeks. Is Josie correct?
Tattoos are created by depositing ink into the dermis, which does not undergo shedding as the epidermis does. Although the tattoo will fade due to exposure to sunlight and the flushing away of ink particles by the lymphoid system, the tattoo is indeed permanent
207
Chef Eduardo sliced through the end of his right thumbnail. Although the surrounding nail grows normally, this part of his nail remains split and doesn’t seem to want to “heal.” What has happened to cause this?
Chef Eduardo has damaged the nail matrix—the part of the nail that produces growth. Because the damaged area has not regrown properly, the nail matrix may be permanently damaged
