1
Q
skin consists of two distinct regions:
A
- Epidermis: superficial region
* Consists of epithelial tissue and is avascular - Dermis: underlies epidermis
* Mostly fibrous connective tissue, vascular
2
Q
Hypodermis (superficial fascia)
A
- Subcutaneous layer deep to skin
- Not part of skin but shares some functions
- Mostly adipose tissue that absorbs shock and
insulates - Anchors skin to underlying structures: mostly muscles
3
Q
consists mostly of keratinized stratified squamous
epithelium
A
epidermis
4
Q
four cell types found in epidermis
A
keratinocytes, melanocytes, dendritic (langerhans) cells, tactile (merkel) cells
5
Q
keratinocytes
A
- Produce fibrous keratin (protein that
gives skin its protective properties) - Major cells of epidermis
- Tightly connected by desmosomes
- Millions slough off every day
6
Q
melanocytes
A
Spider-shaped cells located in deepest epidermis
* Produce pigment melanin, which is packaged into
melanosomes
– Melanosomes are transferred to keratinocytes, where
they protect nucleus from UV damage
7
Q
Dendritic (Langerhans) cells
A
- Star-shaped macrophages that patrol deep epidermis
– Are key activators of immune system
8
Q
tactile (merkel) cells
A
- Sensory receptors that sense touch
9
Q
5 layers of skin:
A
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum (only in thick skin)
- Stratum corneum
10
Q
1.Stratum basale (basal layer)
A
- Deepest of all epidermal layers (base layer)
- One daughter cell journeys from basal layer to surface,
taking 25–45 days to reach surface
– Cell dies as it moves toward surface - Other daughter cell remains in stratum basale as stem cell
11
Q
- stratum spinosum (prickly layer)
A
- Several cell layers thick
– Keratinocytes in this layer appear spikey, so they are called prickle cells
12
Q
- Stratum granulosum (granular layer)
A
- Four to six cells thick, but cells are flattened, so
layer is thin
– Cell appearance changes
13
Q
- Stratum lucidum (clear layer)
A
- Found only in thick skin
– Consists of thin, translucent band of two to three rows of clear, flat, dead keratinocytes
14
Q
- Stratum corneum (horny layer)
A
- 20–30 rows of flat, anucleated, keratinized dead
cells
– Accounts for three-quarters of epidermal
thickness
15
Q
cells change by going through….
A
apoptosis (controlled cell death)
16
Q
apoptosis
A
– Dead cells slough off as dandruff and dander
– Humans can shed ~50,000 cells every minute
17
Q
dermis
A
- Strong, flexible connective tissue
- Fibers in matrix bind body together
18
Q
two layers of dermis
A
papillary and recticular
19
Q
superficial region of dermis
that sends fingerlike projections up into
epidermis
A
dermal papillea
20
Q
papillae found on soles and
palms that lie on larger mounds which cause
epidermas to produce epidermal ridges
A
dermal ridges
21
Q
peg like projections many contain capillary loops, pain receptors, or touch receptors
A
dermal papillae
22
Q
assumed to enhance gripping and enhance sense of touch
A
epidermal ridges=friction ridges
23
Q
makes up about 80% of dermal thickess
A
recticular layer
24
Q
in reticular layer are caused by many collagen fibers running parallel to skin surface
* Important to surgeons because incisions parallel to cleavage lines heal more readily
A
cleavage (tension) lines
25
reticular layer are dermal folds at or near joints
flexure lines
26
Only pigment made in skin; made by melanocytes
melanin
27
two forms: reddish yellow to brownish black
*All humans have same number of
keratinocytes, so color differences are due to
amount and form of melanin
* Freckles and pigmented moles are local
accumulations of melanin
28
carotene
*Yellow to orange pigment
* Most obvious in palms and soles
* Accumulates in stratum corneum and hypodermis
* Can be converted to vitamin A for vision and
epidermal health
29
hemoglobin
* Oxygenated pigment in erythrocytes
* Pinkish hue of fair skin is due to lower levels of
melanin
30
excessive sun exposure damaged skin
1. Elastic fibers clump, causing skin to become
leathery
2. Can depress immune system and cause
alterations in DNA that may lead to skin cancer
3. UV light destroys folic acid
4. Photosensitivity is increased reaction to sun
31
Blue skin color - low oxygenation
of hemoglobin
cyanosis
32
– Fever, hypertension, inflammation, allergy
erythema (redness)
33
Anemia, low blood pressure, fear,
anger
pallor (blanching)
34
Liver disorder
jaundice (yellow cast)
35
Inadequate steroid hormones in
addison's disease
bronzing
36
clotted blood beneath skin
bruises
37
hair
* Consists of dead keratinized cells
* None located on palms, soles, lips, nipples, and
portions of external genitalia
* Functions: Warn of insects on skin, hair on head guards against physical trauma, protect from heat loss, shield skin from sunlight
* Produced by hair follicles
* Contains hard keratin, not like soft keratin found in skin
38
regions of the hair
shaft and root
39
area that extends above scalp, where
keratinization is complete
shaft
40
area within scalp, where keratinization is still
going on
root
41
three parts of hair shaft:
medulla, cortex, and cuticle
42
central core of large cells and air spaces
medulla
43
several layers of flattened cells
surrounding medulla
cortex
44
outer layer consisting of overlapping
layers of single cells
cuticle
45
actively dividing area of bulb that produces hair cells
hair matrix
46
- small band of smooth muscle attached to follicle
- Responsible for “goose bumps”
arrector pili
47
Dermal tissue containing a knot of
capillaries that supplies nutrients to
growing hair
hair papilla
48
pale, fine body hair of children and
adult females
vellus hair
49
coarse, long hair
* found on scalp and eyebrows, at puberty
Terminal hair
50
hair thinning in both sexes after age 40
* true (frank) baldness
alopecia
51
nails
* Scale-like modifications of epidermis that
contain hard keratin
* Act as a protective cover for distal, dorsal
surface of fingers and toes
52
thickened portion of bed responsible for nail growth
nail matrix
53
skin folds that overlap border of nail
nail folds
54
- nail fold that projects onto
surface of nail body
- also called cuticle
eponychium
55
area under free edge of plate
that accumulates dirt
hyponychium
56
Also called sudoriferous glands
sweat glands
57
two main types of sweat glands
- eccrine (merocrine)
- apocrine
58
eccrine (merocrine)
* Most numerous type
* Abundant on palms, soles, and forehead
* Their secretion is sweat
– 99% water, salts, vitamin C, antibodies,
dermcidin (microbe-killing peptide), metabolic
wastes
59
aprocrine sweat glands
- Confined to axillary and anogenital areas
* Secrete viscous milky or yellowish sweat that
contains fatty substances and proteins
– Bacteria break down sweat, leading to body odor
- begin functioning at puberty
60
modified apocrine gland
ceruminous gland and mammary glands
61
lining of external ear canal; secrete cerumen (earwax)
ceruminous gland
62
secrete milk
mammary gland
63
sebaceous (oil) glands
- Widely distributed, except for thick skin of palms and soles
- secrete subum
64
whiteheads
blocked sebaceous glands
65
acne
usually an infectious inflammation of the
sebaceous glands, resulting in pimples
(pustules)
66
known as "cradle cap"
seborrhea
67
function of skin
protection, body temperature regulation, cutaneous sensations, metabolic functions, blood reservoir and excretion of wastes
68
Skin is exposed to microorganisms, abrasions,
temperature extremes, and harmful chemicals
protection
69
constitutes three barriers of protection
chemical barrier, physical barrier, and biological barrier
70
chemical
– Skin secretes many chemicals, such as:
* Sweat, which contains antimicrobial proteins
* Sebum and defensins, which kill bacteria
* Cells also secrete antimicrobial defensin
71
low pH of skin retards bacterial
multiplication
acid mantle
72
physical barrier
flat, dead, keratinized cells of stratum corneum, surrounded by glycolipids, block most water and water-soluble substances
73
biological barrier
– Epidermis contains phagocytic cells
- Dermis contains macrophages
- DNA can absorb harmful UV radiation, converting it to harmless heat
74
insensible perspiration
Under normal, resting body temperature, sweat glands produce about 500 ml/day of unnoticeable sweat
75
sensible perspiration
If body temperature rises, dilation of dermal vessels can increase sweat gland activity to produce 12 L (3 gallons) of noticeable sweat (designed to cool body)
76
Metabolic Functions
1. Skin can synthesize vitamin D needed for
calcium absorption in intestine
2. Chemicals from keratinocytes can disarm
some carcinogens
3. Keratinocytes can activate some hormones
77
blood reservoir
* Skin can hold up to 5% of the body’s total blood
volume
* Skin vessels can be constricted to shunt blood
to other organs, such as an exercising muscle
78
Skin can secrete limited amounts of
nitrogenous wastes, such as ammonia, urea,
and uric acid
excretion
79
less common, but more damaging are:
skin cancer and burns
80
three major types of skin cancer
basal cell carcinoma, squamous cell carcinoma, and melanoma
81
basal cell carcinoma
- Least malignant and most common
- Cured by surgical excision in 99% of cases
82
squamous cell carcinoma
Second most common type; can metastasize
83
melanoma
Cancer of melanocytes; is most dangerous type
because it is highly metastatic and resistant to
chemotherapy
84
burns
-Tissue damage caused by heat, electricity,
radiation, or certain chemicals
- To evaluate burns, the Rule of Nines is used
85
treatment for burns
debridement (removal) of burned skin, antibiotics, temporary covering, and skin grafts
86
are small fluid-filled blisters that itch, and usually occur around the lips and in the mucosa of the mouth
cold sores
87
may be triggered by stress, food allergies, lack of vitamins and minerals, hormonal changes or menstrual periods; are contagious
canker sores
88
delicate hairs in 5th and 6th
month
lanugo coat
89
sebaceous gland secretion that protects
skin of fetus while in watery amniotic fluid
vernix caseosa
90
skin thickens and accumulates more subcutaneous fat; sweat and sebaceous gland activity increases, leading to acne
infancy to adulthood
91
aging skin
– Epidermal replacement slows; skin becomes
thin, dry, and itchy (decreased sebaceous gland activity)
– Subcutaneous fat and elasticity decrease,
leading to cold intolerance and wrinkles
– Increased risk of cancer due to decreased
numbers of melanocytes and dendritic cells
– Hair thinning
92
ways to delay aging
UV protecton, good nutrition, lots of fluids, and good hygiene
Anatomy and Physiology
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