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Chapter 06
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1
6.0 Integumentary System
• Integumentary system
– Covers body and consists of skin and accessary
tissues (nails, hair, sweat glands, sebaceous glands)
– Integument = skin
o Cutaneous membrane
– Barrier to the outside world
– Visual indicator of our physiology and health
– Dermatology, study of skin
2
6.1 Composition and
Functions of the Integument
Learning
Objectives:
1.
2.
3.
4.
5.
Describe the five layers
(strata) of the epidermis.
Differentiate between thick
skin and thin skin.
Explain what causes
differences in skin color.
Characterize the two layers of
the dermis.
Explain the significance of
cleavage lines.
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3
6.1 6.
Describe how dermal blood
Composition and Functions of the Integument
vessels function in
(continued)
temperature regulation.
7.
List the functions of the
Learning
subcutaneous layer.
Objectives:
8.
Name ways in which the
epidermis protects the body
and prevents water loss.
9.
Describe the integument’s
involvement in calcium and
phosphorus utilization.
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4
6.1 Composition and Functions of the
Integument (continued)
10.
11.
Learning
Objectives:
12.
13.
Describe the integument’s
role in secretion and
absorption.
Identify the immune cells that
reside in the integument, and
describe their actions.
Explain how skin helps cool
the body or retain warmth.
List the sensations detected
by the skin’s sensory
receptors.
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5
6.1 Composition and Functions of the Integument
• The integument
– Body’s largest organ
– Composed of all tissues types functioning in concert
o Surface covered by an epithelium
o Underlying CT
˗ Provides strength and resilience
˗ Contains smooth muscle associated with hair follicles
o Nervous tissue
˗ Senses touch, pressure, temperature, and pain
– Protects internal body structures
– 7 to 8% of body weight
– Thickness depends on body location
6
6.1 Composition and Functions of the Integument
• Layers of the integument
̶ Epidermis
o Stratified squamous epithelium
̶ Dermis
o Deeper layer
o Primarily dense irregular connective tissue
˗ Deep to dermis
˗ Subcutaneous layer (hypodermis)
˗ Layer of alveolar and CT
˗ Not part of integumentary system
7
Layers of the
Integument
Figure 6.1
8
6.1a Epidermis
• Epithelium of the integument
–
–
–
–
Epidermis
Keratinized, stratified squamous epithelium
Specific layers, or strata
Layers from deep to superficial
1.
2.
3.
4.
5.
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum
– 1st three layers composed of living keratinocytes
– Corneum and lucidum composed of dead cells
9
6.1a Epidermis
• Stratum basale
– Deepest epidermal layer
– Stratum germinativum or basal layer
– Single layer of cuboidal to low columnar cells
– Attached to underlying basement membrane
o Separates epidermis dermis
– Three cell types
1.Keratinocytes
2.Melanocytes
3.Tactile cells
10
6.1a Epidermis
Stratum basale (continued)
• Keratinocytes
–
–
–
–
–
–
Most abundant cells in epidermis
Found in all layers
Large stem cells
Divide to regenerate new cells
Replace old cells shed at surface
Named for synthesizing of keratin
o Protein that strengthens epidermis
o Called cytokeratins in epidermis
o Make skin almost waterproof
11
6.1a Epidermis
Stratum basale (continued)
• Melanocytes
– Scattered among keratinocytes
– Produce and store pigment (melanin) in response to
ultraviolet light
– Transfer pigment granules (melanosomes) into
keratinocytes
o Pigment accumulates around nucleus of keratinocytes
o Shield nuclear DNA from UV radiation
o Responsible for darker tones of skin
12
6.1a Epidermis
Stratum basale (continued)
• Tactile cells
– Merkel cells
– Few in number
– Scattered within stratum basale
– Sensitive to touch
– When compressed, release chemicals
o Stimulate sensory nerve endings
13
6.1a Epidermis
• Stratum spinosum
– Several layers of polygonal keratinocytes
– Spiny layer
o Named for spiny appearance on microscopy
– Daughter cells from stratum basale pushed into this layer
– Begin to develop into specialized, non-dividing
keratinocytes
o Some in deepest level still dividing cells
– Nondividing keratinocytes attached by intercellular
junctions, desmosomes
14
6.1a Epidermis
Stratum spinosum (continued)
• Epidermal dendritic cells (Langerhans cells)
– Fourth cell type
– In stratum spinosum and stratum granulosum
– Initiate immune response
– Responsive to pathogens and epidermal cancer
cells
15
6.1a Epidermis
• Stratum granulosum
– 3 to 5 layers of keratinocytes
– Granular layer
– Superficial to stratum spinosum
– Process begins called keratinization
o Keratinocytes fill with keratin
o Causes nucleus and organelles to disintegrate
o Fully keratinized cell dead but structurally sound
o Process not complete until in more superficial layers
16
6.1a Epidermis
• Stratum lucidum
– 2 to 3 cell layers
– Translucent
– Clear layer
– Superficial to stratum granulosum
– Found only on thick skin on palms and soles
– Cells filled with a translucent protein, eleidin
o Intermediate product in keratin maturation
o Helps protect from UV light
17
6.1a Epidermis
• Stratum corneum
– Hornlike layer
– Most superficial layer
– What you see when you look at your skin
– 20 to 30 layers of dead, interlocking keratinized
cells
o Cells are anucleate (without a nucleus) and tightly
packed
– Cornified epithelium contains large amount of
keratin
18
6.1a Epidermis
Stratum corneum (continued)
̶ Migration of keratinocytes
o Originate from stem cells in stratum basale
o Migrate through strata to stratum corneum over two weeks
o Undergoing structural changes
̶ Remain in stratum corneum another two weeks
̶ Shed
̶ Stratum corneum has dry, thickened surface
o Unsuitable for microorganism growth
o Secretions help protect
19
Epidermal Strata
Figure 6.2
20
6.1a Epidermis
• Variations in the epidermis
– Between different body regions
– Between individuals
– In thickness, color, and skin markings
• Thick versus thin skin
– Thick skin
o Palms of hands, soles of feet
o Occurs in all five layers of epidermal strata
o Houses sweat glands
o No hair follicles or sebaceous glands
o From 0.4 to 0.6 mm thick
21
6.1a Epidermis
• Thick versus thin skin (continued)
– Thin skin
o Covers most of body
o Lacks a stratum lucidum
o Sweat glands, hair follicles, and sebaceous glands
o From 0.075 to 0.150 mm thick
22
Thick Skin and Thin Skin
Figure 6.3
23
6.1a Epidermis
• Skin color
̶ Normal color from hemoglobin, melanin, carotene
̶ Hemoglobin
o
o
o
o
o
Oxygen-binding protein in red blood cells
Bright red color upon binding oxygen
Gives blood vessels in dermis a reddish tint
Seen most easily in fair skinned individuals
More visible if blood vessels dilate
24
6.1a Epidermis
• Melanin
–
–
–
–
Pigment produced and stored in melanocytes
In black, brown, tan, yellow-brown shades
Transferred to keratinocytes in stratum basale
Amount in skin varies
o According to heredity and light exposure
o UV light stimulates melanin production
– All people with same number of melanocytes
– Darker-skinned individuals produce more and darker
colored melanin
25
Production of Melanin by Melanocytes
Figure 6.4
26
6.1a Epidermis
• Carotene
– Yellow-orange pigment
– Acquired from yellow-orange vegetables
– Accumulates in
o Subcutaneous fat
o Keratinocytes of stratum corneum
– Converted to vitamin A by body
– Plays important role in
o Vision
o Reducing free radicals
o Immune function
27
6.1a Epidermis
• Albinism
̶ Inherited recessive condition
̶ Enzyme for melanin nonfunctional
̶ Melanocytes unable to produce melanin
̶ Individuals have white hair, pale skin pink irises
28
6.1a Epidermis
Skin markings
• Nevus
–
–
–
–
Mole
Harmless localized overgrowth of melanocytes
Rarely becomes malignant
Should be monitored for changes suggesting malignancy
• Freckles
– Yellowish or brown spots
– Represent localized areas of increased melanocyte activity
– Degree of pigmentation based on sun exposure and heredity
29
6.1a Epidermis
Skin markings (continued)
• Hemangioma
– Skin discoloration due to benign blood vessel tumor
– Capillary hemangiomas
o Bright red to deep purple nodules
o Usually present at birth and disappear in childhood
o Strawberry-colored birthmarks
– Cavernous hemangiomas
o Larger dermal blood vessels
o May last a lifetime
o Port-wine stains
30
6.1a Epidermis
Skin markings (continued)
• Friction ridges
–
–
–
–
–
–
Small conical pegs in thin skin
Complex arches and whorls on finger, palms, soles, and toes
Large folds and valleys of dermis and epidermis
Increase friction on contact
Each individual with a unique pattern of friction ridges
Personal identification
31
Friction Ridges of Thick Skin
Figure 6.5
32
Clinical View: UV Radiation, Sunscreens, and Sunless Tanners
• Sun generates UVA, UVB, UVC radiation
̶ UVC rays absorbed and do not reach earth
• Sunscreens block UVA and UVB rays
– Protect skin if used correctly
– Need high enough SPF (sun protection factor)
• Sunless tanners create tanned skin without UV light
exposure.
– No protection against UV rays
33
What did you
learn?
•
What are the layers of the epidermis,
starting from the surface of the skin?
•
Which type of skin lacks a stratum
lucidum and is found covering most of
the body?
•
Describe the different types of cells
found in each stratum of the
epidermis?
•
In which stratum are the keratinocytes
alive?
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34
6.1b Dermis
• Dermis
Deep to epidermis
Thickness, 0.5 mm to 3.0 mm
Composed of CT proper
Collagen with elastic and reticular fibers
Motile dendritic cells serve an immune function
Blood vessels, sweat glands, sebaceous glands, hair
follicles, nail roots, sensory nerve endings, arrector pili
– Two layers
–
–
–
–
–
–
o Papillary layer and deeper reticular layer
35
6.1b Dermis
• Papillary layer of the dermis
– Superficial region
– Deep to epidermis
– Areolar connective tissue
– Named for projections of dermis, dermal papillae
o Projections of epidermis interdigitate with papillae,
epidermal ridges
– Interlock and increase area of contact between
layers
36
6.1b Dermis
• Reticular layer of the dermis
– Deeper, major portion of dermis
– From papillary layer to subcutaneous layer
– Dense irregular connective tissue
– Large bundles of collagen fibers project
o Fibers interwoven into meshwork surrounding structures
37
Layers of the Dermis
Figure 6.6
38
6.1b Dermis
• Lines of cleavage and stretch marks
• Collagen and elastic fibers oriented in parallel bundles
at specific locations
–
–
–
–
Due to applied stress during routine movement
Bundles function to resist stress
Orientation indicated by lines of cleavage (tension lines)
Important consideration for surgery
o Incisions parallel to cleavage line are more likely to heal quickly
o Incisions perpendicular to cleavage lines are more likely to open due
to cut elastic fibers
39
6.1b Dermis
• Lines of cleavage and stretch marks (continued)
• Fibers contribute to skin characteristics
– Collagen fibers impart tensile strength
– Elastic fibers allow stretch and recoil
– If skin stretched beyond its capabilities
o Some collagen fibers torn
o Stretch marks, striae
– Flexibility and thickness of dermis
o Diminished by UV light and aging
– Causes sagging or wrinkled skin
40
Lines of Cleavage
Figure 6.7
41
Clinical View: Tattoos
•
•
•
•
•
•
Permanent images produced on integument
Dye injected into dermis
Permanent part of dermis layer
Usually impossible to completely remove a tattoo
Lasers used to break down pigments
Newer inks are available that allow for removal
42
6.1c Subcutaneous Layer
• Subcutaneous layer
–
–
–
–
–
–
–
–
Hypodermis, superficial fascia
Not part of integument
Areolar and adipose CT
Subcutaneous fat in areas of more adipose tissue
CT fibers interwoven with fibers of reticular dermis
Pads and protects body
Acts as energy reservoir
Provides thermal insulation
43
6.1c Subcutaneous Layer
• Subcutaneous layer (continued)
– Drug injection site
o Extensive vascular network promotes rapid absorption
– Sexes have different layer thickness and distribution
o Thicker in women
˗ Accumulates primarily in breasts, buttocks, hips, and thighs
o Thinner in men
˗ Accumulates primarily in neck, upper arms, abdomen,
lower back, buttocks
44
Integument
Layers and the
Subcutaneous
Layer (Table 6.1)
45
What did you
learn?
•
The dermal papillae are a part of
what layer of the skin?
•
Should a surgeon generally cut
perpendicular or parallel to
cleavage lines?
•
What two types of tissue form the
subcutaneous layer?
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46
6.1d Functions of the Integument
• Protection
– Physical barrier
– Protects body from injury and trauma
– Protects from harmful chemicals, toxins, microbes,
temperature extremes
– Protects deeper tissue from solar radiation
47
6.1d Functions of the Integument
• Prevention of water loss/gain
– Epidermis is water resistant, not waterproof
– Water lost by sweat, transpiration
o Fluids penetrate through epidermis and evaporate in air
– Dehydration a danger with severe burns
o Water escapes without skin barrier
– Skin also prevents water gain
o Water resistance prevents absorption
48
6.1d Functions of the Integument
• Metabolic regulation
–
–
–
–
–
–
Vitamin D3 (cholecalciferol
Synthesized from a steroid precursor by keratinocytes
Occurs upon UV exposure
D3 released into blood and transported to liver
Converted to another intermediate molecule (calcidiol)
Transported to kidney and converted to calcitriol
o
o
Active form of vitamin D
Considered a hormone
49
6.1d Functions of the Integument
• Vitamin D (continued)
– Increases absorption of calcium and phosphate
– Role in regulating blood levels of calcium and
phosphate
– 10 to 15 minutes of sunlight daily is adequate
• Other forms of metabolic regulation
– Skin converts some compounds to slightly
different forms
– E.g., hydrocortisone applied to skin helps stop
inflammation/itching
50
6.1d Functions of the Integument
Secretion and absorption
• Secretion
– Waste products secreted onto skin surface during sweating
o
o
o
Urea, salts, water
Amounts adjustable
Role in electrolyte homeostasis
– Sebum of sebaceous glands lubricates skin surface and
hair
o
Helps make integument water resistant
51
6.1d Functions of the Integument
Secretion and absorption (continued)
• Absorption
– Skin absorbs certain chemicals and drugs
– Other materials blocked
– Selectively permeable
o
Some materials pass through, others blocked
– Transdermal administration
o
o
Some oil-soluble drugs delivered by adhesive patch
Slowly penetrate epidermis, absorbed into blood vessels
52
6.1d Functions of the Integument
• Immune function
– Epidermal dendritic cells
o
o
o
In stratum spinosum
Initiate immune response against pathogens
Attack cancer cells
• Temperature regulation
– Influenced by capillaries and sweat glands in dermis
– Dermal blood vessels play important role in body
temperature/blood pressure
53
6.1d Functions of the Integument
• Temperature regulation (continued)
• Vasoconstriction
̶ Vessels narrow, less blood travels through
̶ Less blood passage in dermal vessels means deeper vessels
must be used
̶ Shunting of blood away from periphery of body toward deeper
structures
̶ Occurs when body tries to conserve heat
̶ Reason we look pale when cold
54
6.1d Functions of the Integument
• Temperature regulation (continued)
• Vasodilation
̶ Diameter of vessels increases, more blood travel through
̶ More blood can travel close to surface
̶ Results in reddish/pink skin, flushed face during exercise
• Sensory Reception
– Skin has extensive innervation
o
o
Distribution of nerve fibers
Monitor stimuli in dermis and epidermis
– Touch receptors detect stimuli
o
Send input to brain
55
What did you
learn?
•
What is the active form of
vitamin D?
•
Where is it synthesized?
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56
6.2 Integumentary Structures Derived from Epidermis
• Epidermal derivatives
̶ Nails
̶ Hair
̶ Exocrine glands
̶ Formed during embryonic development
̶ Portions of epidermis invaginated into the dermis
̶ Hair and nails composed of dead cells
̶ Exocrine glands composed of living cells
57
6.2
Integumentary
Structures Derived from
Epidermis
1.
2.
3.
Learning
Objectives:
4.
5.
6.
7.
Describe the function of nails.
List the main components of
the nail.
Describe the structure of a hair
and a follicle.
List the functions of hair.
Differentiate between the two
types of sweat glands.
Describe the function of
sebaceous glands.
Name the two other modified
integumentary glands.
Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education
58
6.2a Nails
• Structure of nails
–
–
–
–
–
–
–
Scalelike modifications of stratum corneum
Dorsal edges of fingers and toes
Protect distal tips of digits
Assist in grasping objects
Distal whitish free edge (no underlying capillaries)
Pinkish nail body (underlying capillaries)
Nail root (part embedded in skin)
o
These three constitute nail plate
– Nail bed
o
Layer of living epidermis covered by nail body
59
6.2a Nails
• Structure of nails (continued)
– Nail matrix
o
Actively growing part of nail at proximal end of nail body
– Lunula
o
Whitish semilunar area on proximal end of nail body
– Nail folds
o
Folds of skin overlapping nail
– Eponychium (cuticle)
o
Narrow band of epidermis from margin of nail wall onto nail body
– Hyponychium
o
Thickened stratum corneum over which free nail edge projects
60
Structure
of a
Fingernail
Figure 6.9
61
Clinical View: Nail Disorders
• Nails are indicative of overall health
– Brittle nails are prone to vertical splitting and separation of
nail plate layers
– Ingrown nails with edge of nail digging into skin
– Onchomycosis is a fungal infection
– Yellow nail syndrome occurs when growth and thickening
slows
– Spoon nails outer surface of nail is concave
– Beau’s lines indicate temporary interference with nail growth
– Vertical ridging common and usually harmless
62
6.2b Hair
• Hair found almost everywhere on the body except
̶ Hands and palmar surface of fingers
̶ Sides and soles of feet and toes
̶ Lips
̶ Portions of external genitalia
• Hair type and distribution
̶ Single hair, pilus, shaped like slender filament
̶ Keratinized cells
̶ Grows from hair follicles
63
6.2b Hair
Hair type and distribution (continued)
•Three types of hair
– Lanugo: fine, unpigmented, downy hair
o
Appears in last trimester
– Vellus: fine hair
o
o
Primary human hair
Found on upper and lower limbs
– Terminal hair: coarser, pigmented, longer
o
o
On scalp, eyebrows, and eyelashes, men’s beards
During puberty, replaces vellus hair in axillary and pubic regions
64
6.2b Hair
Hair structure and follicles
• 3 zones along length of a hair
– Hair bulb
o
o
o
Swelling at base where hair originates in dermis
Surrounds hair papilla, composed of CT
Only region containing living epithelial cells
– Root
o
Zone of hair from bulb to skin surface
– Shaft
o
Portion of hair beyond skin surface
65
6.2b Hair
• Hair components
– Hair matrix
o
o
o
Structure at base of the hair bulb
Epithelial cells divide here
Produce new cells, gradually pushed toward surface
– Medulla
o
o
Remnant of matrix
Flexible, soft keratin
– Cortex
o
o
Flattened cells closer to outer hair surface
Relatively hard
– Cuticle
o
Single cell layer around cortex
66
6.2b Hair
• Hair components (continued)
̶ Hair follicle
o Oblique tube surrounding hair root
o Extends into dermis and sometimes subcutaneous layer
o Outer CT root sheath originating in dermis
o Inner epithelial tissue root sheath originating from epidermis
̶ Arrector pili
o Thin ribbons of smooth muscle
o Extend from hair follicle to dermal papillae
o Elevates hair with contraction, “goosebumps”
67
Hair
Figure 6.10
68
6.2b Hair
Functions of hair
• Protection
–
–
–
–
–
Protects scalp from sunburn and injury
Hair within nostrils traps particles
Hair within ears protects from foreign matter
Eyelashes protect eyes
Eyebrows keep sweat out of eyes
• Facial expression
– Hairs of eyebrows enhance facial expression
• Heat retention
– Prevents loss of heat from scalp
69
6.2b Hair
Functions of hair (continued)
• Sensory reception
– Tactile receptors detect light touch
• Visual identification
– Helps identify age or sex, specific individuals
• Chemical signal dispersal
– Disperse pheromones
o
o
Chemical signals involved in attracting sexual partners
Secreted by specific sweat glands onto hairs in axillary
and pubic regions
70
6.2b Hair
• Hair color
– Synthesis of melanin in matrix adjacent to hair papillae
– Variations reflect genetic, environmental, and hormonal
factors
– Lightens with age as pigment production decreases
– Gray hair results from gradual reduction in melanin
– White hair occurs due to complete stoppage of melanin
production
71
6.2b Hair
• Hair growth and replacement
̶ Three phases of hair growth cycle
1. Anagen—active phase
2. Catagen—brief regression period
3. Telogen—resting phase
72
6.2b Hair
1. Anagen phase
– Living cells in hair bulb rapidly growing,
dividing, and transforming into hair.
– Longest phase, 18 months to 7 years, depending
on genetics
– Each hair grows 1/3mm/day, or 0.5 to 1 cm per
month
– Normally, 80–95% of follicles are in anagen phase
73
6.2b Hair
2. Catagen phase
̶
Cell division ceases
Follicle undergoes involution
Lasts 3 to 4 weeks
̶
̶
3. Telogen phase
̶
Hair is shed
Lasts 3 to 4 months
Then, hair bulb cells begin to regrow
Follicle reenters anagen phase
̶
̶
̶
74
6.2b Hair
• Hair loss
– Normally 10 to 100 hairs lost per day
o
o
More than that could mean a health problem
Temporary loss could be from drugs, dietary factors, radiation,
high fever, stress
– Thinning of hair, alopecia
o
Due to aging
– Diffuse hair loss
o
o
o
Hair shed from all parts of scalp
Primarily in women
Due to hormones, drugs, iron deficiency
75
6.2b Hair
• Hair loss (continued)
– Male pattern baldness
o
o
o
o
Loss of hair first from only crown region of scalp
Combination of genetic and hormonal factors
Baldness allele dominant in males and recessive in females
Expressed only in presence of high testosterone
• Hair growth
– Hirsutism
o
o
o
o
Excessive male pattern hairiness
Typically on face, chest, back
Excess androgens
Caused by medical condition or medication
76
6.2c Exocrine Glands of the Skin
• Skin houses many types of exocrine
glands
• Two most common types
̶ Sweat glands
̶ Sebaceous glands
77
6.2c Exocrine Glands of the Skin
• Sweat glands
̶ Two groups
o Merocrine
o Apocrine
̶ Coiled, tubular secretory portion in reticular dermis
̶ Sweat gland duct transports secretions to surface
̶ Gland duct opens on epidermal surface, sweat pore
̶ Myoepithelial cells
o Contract to squeeze gland
o Discharge secretions in response to sympathetic stimulation
78
6.2c Exocrine Glands of the Skin
• Merocrine sweat glands
̶ Most numerous and widely distributed
̶ Simple, coiled tubular glands
̶ Discharge secretions onto skin surface
̶ Produce secretion by exocytosis
̶ Secrete sweat
o Composed of 99% water and 1% other chemicals
o Includes: electrolytes, metabolites, and waste products
79
6.2c Exocrine Glands of the Skin
• Merocrine sweat glands (continued)
– Major function, thermoregulation
o Regulation of body temperature by fluid evaporation
– Secretions
o
o
o
o
Provide a means for loss of water and electrolytes
May help eliminate ingested drugs
Dilute harmful chemicals
Antibacterial/antifungal activity
80
6.2c Exocrine Glands of the Skin
• Apocrine sweat glands
– Coiled, tubular glands
– Discharge secretions into hair follicles located axillae,
around nipples, in pubic and anal region
– Produce secretion by exocytosis
– Produce viscous cloudy secretions
o
o
Contain proteins and lipids
Produce odor when acted on by bacteria
– Start producing secretions during puberty
81
6.2c Exocrine Glands of the Skin
• Sebaceous glands
– Holocrine glands
– Produce oily secretion, sebum
o Lubricant for skin and hair
o Bactericidal
o Discharges into a hair follicle
– Secretion stimulated by hormones, especially
androgens
– Activated during puberty
82
6.2c Exocrine Glands of the Skin
Other integumentary glands
• Ceruminous glands
– Modified apocrine sweat glands
– Located only in external ear canal
– Secretions of waterproof earwax, cerumen
o
o
Traps foreign material
Lubricates acoustic meatus and eardrum
• Mammary glands
– Modified apocrine sweat glands of breast
– Only function in pregnant and lactating females
– Produce milk
83
Exocrine Glands
of the Skin
Figure 6.11a
84
Clinical View: Acne and Acne Treatments
• Acne
–
–
–
–
Plugged sebaceous ducts
Typically begins during puberty
Increased activity gland secretions may block pores
Treatments
o Benzoyl peroxide, salicylic acid, antibiotics, vitamin A–like
compounds, systemic retinoinds
– May lead to scarring if untreated
85
What did you
learn?
•
What are the three components
of the nail plate?
•
What are the three portions of a
hair?
•
What do sebaceous glands
secrete? Where is this material
secreted?
Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education
6.3 Repair and
Regeneration of the
Integumentary System
86
1.
Distinguish between
regeneration and fibrosis.
2.
Describe the process of wound
healing.
Learning
Objectives:
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87
6.3 Repair and Regeneration of the
Integumentary System
• Tissue is repaired in one of two ways: regeneration or
fibrosis
• Regeneration
̶ Replacement of damaged or dead cells with same cell type
̶ Restores organ function
• Fibrosis
̶ Gap filled with scar tissue
̶ Collagen produced by fibroblasts
̶ Functional activities not restored
88
6.3 Repair and Regeneration of the
Integumentary System
• Stages of wound healing
1) Cut blood vessels bleed into wound
2) Blood clot forms and leukocytes clean wound
– Clot is a temporary barrier for pathogens
3) Blood vessels re-grow and granulation tissue forms
– Vascular CT initially forms in wound
4) Epithelium regenerates and CT fibrosis occurs
89
6.3 Repair and Regeneration of the
Integumentary System
• Wound healing
– Dependent on extent of injury
– Longer time needed for wider and deeper
surfaces
– With severe damage
o Less likely to return to original condition
o Hair follicles, exocrine glands, nerves, and arrector
pili muscle cells not repaired
90
Stages in
Wound
Healing
Figure 6.12
91
Clinical View: Psoriasis
•
•
•
•
•
•
Chronic autoimmune skin disease
Keratinocytes attacked by T-lymphocytes
Causes rapid overgrowth of new skin cells
Patches of whitish, scaly skin on epidermal surface
Symptoms: severe itching, pain, skin cracking
Treatments
̶ Corticosteroids, UV light therapy, medications that
interfere with skin cell production
92
Clinical View: Burns
•
•
•
–
Major cause of accidental death
Caused by heat, radiation, chemicals, sunlight, electrical shock
Threat to life from fluid loss, infection, effects of burned tissue
First degree burns
o Involve only epidermis
o Slight redness and pain
o Immerse burned area in cool water
– Second degree burns
o Involve epidermis and part of dermis
o Skin blistered and painful
o Slight scarring
93
Clinical View: Burns (continued)
– Third-degree burns
o Involve epidermis, dermis, and subcutaneous layer
o Require hospitalization
o Treatment for dehydration and infection
o Require additional caloric intake
o Severe scarring
o May need debridement and skin graft
– Burn severity can be measured by rule of nines
o Estimates surface area of burns
94
Clinical View: Burns (continued)
• Treatments for burns
̶ Manage fluid loss
̶ Relieve swelling
̶ Manage pain
̶ Remove dead tissue
̶ Control infection
̶ Increase calorie intake
95
What did you
learn?
•
What is the term for the process of
scar tissue formation?
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96
6.4 Development and
1.
Aging of the Integumentary System
Learning
Objectives:
2.
3.
4.
Describe how integument
develops from two germ
layers.
Explain the developmental
origins of nails, hair, and
glands.
Explain changes to the skin
with age.
List factors that contribute to
skin aging.
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97
6.4a Integument and Integumentary
Derivatives Development
• Development around week 7
– Ectoderm forms a layer of squamous epithelium
o
o
Becomes periderm and basal layer
Basal layer forms all epidermal layers
• By week 21
– Formation of stratum corneum and friction ridges
o
o
Periderm eventually sloughed off
Mixes with sebum to produce coating on fetus skin, vernix caseosa
• Development around week 11
– Dermis is derived from mesoderm
o
Mesoderm becomes mesenchyme
98
6.4a Integument and Integumentary
Derivatives Development
• By week 32
– Fingernails/toenails form
• Between weeks 9 and 12
– Hair follicles appear
o
Pockets of cells, hair buds
• By week 20
– Sweat and sebaceous glands appear on palms/soles; later
in other regions
99
6.4b Aging of the Integument
• Skin changes with aging
– Reduced number and activity of stem cells
o
o
–
–
–
–
–
Skin repair processes slows
Thin skin less likely to protect from trauma
Fewer collagen fibers
Elastic fibers lose elasticity
Crease lines form (wrinkles)
Immune response decreased due to fewer dendritic cells
Hair follicles produce thinner hair or none at all
100
6.4b Aging of the Integument
• Skin changes with aging (continued)
• UV radiation
– Damages DNA in epidermal cells
o
o
Accelerates aging
Predominant factor in skin cancer
• Skin cancer
Most common type of cancer
Typically on head and neck
Fair-skinned individuals at highest risk
Risk reduced with sunscreen and avoiding UV
overexposure
– Periodic skin exams recommended
–
–
–
–
101
Clinical View: Botox and Wrinkles
• Botox is a treatment for wrinkles caused by facial muscle
expression
• Clostridium botulinum toxin
• Blocks nerve impulses to facial expression muscles
• Decreases or eliminates wrinkles
• Botox injected into specific facial muscles
• Temporary effect only
• Muscles regain function and procedure must be repeated
102
What did you
learn?
•
What two primary germ layers
form the integument?
•
What are the origins of nails, hair,
and glands?
•
Explain how the skin ages and the
factors that affect this aging?
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103