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The Integumentary SystemChapter 5
Goals- Integumentary system
• Function of integumentary system
• Structure of the Skin and its accessory structures
• Disorders of skin
Skin• Also called the cutaneous membrane or the
integument
• Covers the entire surface of the body
• Largest organ in the body; 1.8 m2
• Comprised of all 4 tissue types
• The integumentary system is made up of the skin and several accessory organs
• Two regions – epidermis and dermis
• Hypodermis or subcutaneous tissue attaches the skin to underlying tissue
4
Skin Anatomy
Largest organ in body
• Organ?
• What tissue types are in the integumentary system
– Epithelial- covers surface
– Connective tissue- tough/flexible protein fiber acts like organic glue
– Muscle tissue-interacts with hairs
– Nervous tissue- allows us to detect external stimulus
Layers of skin
• Two layers
– Epidermis (5 layers)- Outer layer
• External portion-layers of dead flattened skin containing keratin- protect and give elasticity
• Interior portion- living cells that are constantly dividing and pushing upwards to replace dead cells that are sloughed off
– Dermis- Inner layer
• Thicker layer that is the control center of the skin
• Hypodermis/ Subcutaneous
7
Function of Skin
• Protection/Physical Barrier
• Cutaneous Sensation
• Thermoregulation
• Vitamin D synthesis
• Blood Reservoir
Protection
• Micro-organisms
• Water loss
• The sun’s harmful rays/uv radiation• Burns
• Cancer
Sensory Organ
• Tactile receptors in skin
– Thermal
– Touch (light v. deep)
– Pressure (light v. deep)
– Pain
Thermoregulation/Heat Balance
• Sweating
– Sweat gland
• Evaporation of sweat cools our body
• Blood flow through cutaneous blood vessels
– Cutaneous Vasodilation-Flushing
– Cutaneous Vasoconstriction-Pallid
Synthesis of Vitamin D
• Skin as a gland- produces a hormone
• Cholesterol + UV light Vitamin D
• Vitamin D converted to Calcitriol in liver and kidney.
• Why is Vitamin D important?
– Regulates absorption of Calcium in digestive tract
– Important for bone growth
• Rickets
Largest organ in body
• Organ?
• What tissue types are in the integumentary system
– Epithelial- covers surface
– Connective tissue- tough/flexible protein fiber acts like organic glue
– Muscle tissue-interacts with hairs
– Nervous tissue- allows us to detect external stimulus
Layers of skin
• Two layers
– Epidermis (5 layers)- Outer layer
• External portion-layers of dead flattened skin containing keratin- protect and give elasticity
• Interior portion- living cells that are constantly dividing and pushing upwards to replace dead cells that are sloughed off
– Dermis- Inner layer
• Thicker layer that is the control center of the skin
• Hypodermis/ Subcutaneous
Epidermis
• Outer, thinner region
• Stratified Squamous Epithelium
• 5 layers (strata)
– Stratum Corneum -C- Come
– Stratum lucidum- -L- Let’s
– Stratum granulosum - G- Get
– Stratum spinosum - S- Sun
– Stratum Basale - B- Burned
19
Stratum Basale• Deepest layer/just superficial to dermis• Constantly dividing • New cells pushed upward to surface, die and
slough off• Cells:
– Keratinocytes-keratin-water proofing protein– Melanocytes- melanin- give skin color/uv protection– Langerhans cells- macrophages– Stem cells
• Sensory Nerve– Free nerve endings: pain and temperature sensation– Merkel cells/Tactile Cells- touch sensation
Stratum Spinosum
• Cells still dividing
• Take on spiny appearance due to keratin fibers
Stratum Granulosum
• Cell death starting to occur
• Cells die and condense- Flattened cells
• Contain keratin and dark staining pigment granules
• Keratin-glycolipid secreted (hydrophobic)forms a water barrier
Stratum Lucidum
• Only in thick skin –palms/soles
• Provides protection from constant friction
Stratum Corneum
• Tough uppermost layer of epidermis
• Keratinized cells- hardened and dead
• Protects body from
• Cells will slough off/exfoliate…dust
• Life cycle of cell in epidermis- 3 weeks
Cells in the Epidermis
• Keratinocytes- 90%– Keratin– Function: physical
barrier/prevent H2O loss
• Melanocytes– Melanin– Function: UV protection– Skin color
• Langerhan cells– Guardians of the skin
• Merkel cell/Tactile disk– Light touch/sensation
Dermis
Control Center of the Skin
29
Dermis• Thicker than epidermis (varies in thickness)
• Dense fibrous Connective Tissue (irregularly arranged)
• Collagenous fibers prevent skin from being torn
• Elastic fibers stretch to allow movement of muscles and joints
• Vascularization of dermis supplies oxygen and nutrients to cells of dermis and epidermis and causes temporary changes to skin color
• Numerous nerve fibers- sensory and motor
In the Dermis
• Hair follicles
• Glands
– Sebaceous
– Sudiferous
• Blood vessels
• Nerves
• Nerve endings
Papillary Folds
• Junction between epidermis and dermis
• Inter-digitates
• Function?
33
Hypodermis/Subcutaneous layer
• Composed of loose connective tissue and fascia that connects skin to underlying tissues
• Subdermal fat
• Superficial muscles
• Mostly adipose tissue and fascia
Accessory Structures of the Skin
Hair
• All over body except palms, soles, lips, nipples and part of external reproductive organs
• Types:
– Lanugo- fetal hair
– Vellus hair- thin, child’s hair
– Terminal hair- thicker, darker hair: puberty
Hair Follicle
• Formed from epidermal cells
• Located in dermis
• Cells become keratinized as they are pushed out
• Hair root-portion within follicle
• Hair shaft- portion that continues beyond skin
b: © The McGraw Hill Companies, Inc./Dr. Alvin Tesler, photographer
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Fig. 5.2
hair shaft
(beyond epidermis)
Epidermis
hair
root
sebaceous
(oil) gland
Dermisarrector
pili muscle
dermal blood
vessels
a.
region of
cell division
b.
LM 70x
Hair Follicle-Associated with:
• Sebaceous Gland (oil)
– Secrete sebum
• Arrector Pili muscle
– Smooth muscle attached to hair follicle
– Causes “pilo-erection”• Cold
• emotion
Hair Function
• Warmth
• Sensation
• Aid in cooling of skin
• Some protection
Glands of the skin
• Gland: groups of specialized cells that produce/secrete substances into ducts
– Sebaceous (oil) gland*
– Sudoriferous (sweat)*
– Mammary glands
Sebaceous Glands
• Opens into neck of hair follicle
• Secretes sebum
• Secretion is stimulated by sex hormones
• Comedones– Sebum plugging duct
• Acne vulgaris– Inflammation of
sebaceous gland
Acne Vulgaris
• At pilosebaceous unit
• Occurs at puberty (80%)
• Cause– Genetic
– Increase sebum
– bacteria
• Worse on face, back and chest– Densest population of
sebaceous follicles
Sudoriferous (sweat) glands
• Present in all areas of skin:
• Some more active under stress
• Types:
– Eccrine
– Apocrine glands
– Ceruminous glands
Eccrine Sweat Gland
• Open onto surface of skin secretes sweat
• Contains
– Water
– NaCl
– Urea- waste product
• Functions in Thermoregulation
– Evaporation of sweat cools body temperature
Apocrine glands
• Opens into hair follicle
• Location: genital, perianal, inguinal, axillary
• Function: ?
• Begins to secrete during puberty
• More with stress
• Smelly (fatty sweat + bacteria)
Blood and Lymphatic Vessels of skin
• None located in epidermis
• Cutaneous Blood Vessels in Dermis
– Flushing v. pallor
– Bruising
• Lymphatic vessels
– Conduct excess tissue fluid away from the region to be returned to blood stream
• edema
Nerve Fibers of Skin
• Majority in dermis (nerve endings in the epidermis)
• Sensory Nerve Fibers:– Thermoreceptors– Mechanoreceptors– Nociceptors/Pain receptors
• Motor Nerve Fibers:– Autonomic motor nerve fibers supply:
• Glands• Arector pili muscle• Cutaneous blood vessels
Nails
• Formed by specialized epithelial cells-
• Nail root- base of nail
• Nail body- visible portion of the nail
• Cuticles- folds of skin that hides the root
• Lunula- area of rapidly dividing cells
• Epithelial cells become keratinized as move away from the root
• Pink color due to vascular dermis under the nail body
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
body of nail
dermis
epidermis
finger bone
cuticle
nail root
nail bed
Fig. 5.1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
stratum corneum
stratum lucidum
stratum granulosum
stratum spinosum
stratum basale
free nerve endings
dermal papilla
arrector pili muscle
sebaceous (oil) gland
capillariessweat gland
vein
artery
nerve
adipose connective tissue
Epidermis
hair shaft
Dermis
Hypodermis
hair follicle areolar
connective tissue
sensory
receptors
sensory
nerve fiber
Skin Cancer
• Begins with mutation of the skin cell DNA
• Non-melanoma cancers- less likely to metastasize
– Basal Cell carcinoma
– Squamous cell carcinoma
• Melanoma
Basal Cell Carcinoma
• Most common• UV radiation causes
epidermal basal cells to form a tumor
• Signs (varied):– Open sore that will not
heal– Recurring reddish patch– Smooth, circular growth
with raised edges– Shiny bump– Pale mark
• 95% curable
Squamous Cell Carcinoma
• 5x less common than basal cell carcinoma
• More likely to spread than BCC
• 1% die• Triggered by excessive UV
exposure• Similar presentation to
BCC but may present as wart-like lesion or scaly growth that bleeds and scabs
Melanoma
• More likely to be malignant
• Starts in melanocyte
• Triggered by excessive UV exposure
• Has the appearance of unusual mole
• More common in fair skinned people
Table 5.1
Fig. 5.5
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. Basal cell carcinoma c. Melanomab. Squamous cell carcinomaa: © Ken Greer/Visuals Unlimited; b: © Dr. P. Marazzi/SPL/Photo Researchers; c: © James Stevenson/SPL/Photo Researchers
Prevention
• Use broad-spectrum sunscreens of at least SPF 15
• Wear protective clothing to cover skin
• Wear UV sunglasses
• Stay out of sun between 10-3pm
• Avoid tanning beds
Wound healing
• Cut causes inflammatory response
• Steps of wound healing– Clot formation– Cells move to the area
(WBC and fibroblasts)– Fibroblasts pull margings
together and promote tissue regeneration
– Basal layer produces new cells
– Proliferatin fibroblasts form a scar
Fig. 5.6-1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
wound
subcutaneous fat
White
blood cells
Dermis
of skin
blood
vessel
Epidermis
of skin
a.
Fig. 5.6-2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
wound
subcutaneous fat
White
blood cells
Dermis
of skin
blood
vessel
Epidermis
of skin
a.
scab
fibroblast
white
blood cells
b.
Fig. 5.6-3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
wound
subcutaneous fat
White
blood cells
Dermis
of skin
blood
vessel
Epidermis
of skin
a.
scab
fibroblast
white
blood cells
b.
fibroblast
regrowth of
blood vessel
regenerating
tissue
(epidermis)
scab
c.
Fig. 5.6
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
wound
subcutaneous fat
White
blood cells
Dermis
of skin
blood
vessel
Epidermis
of skin
a.
scab
fibroblast
white
blood cells
b.
fibroblast
regrowth of
blood vessel
regenerating
tissue
(epidermis)
scab
c.
regenerated
tissue
(epidermis)
scar tissue
(fibrosis)
fibroblast
freshly healed
epidermis
d.
Burns
• Cause: heat, radioactive, chemical, electrical
• Severity determined by:
– Depth• 1st, 2nd, 3rd
– Width• Rule of nines –estimates
burn severity
Fig. 5B
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
9%
9%
36%
9%
perineum
1%
18% 18%
First Degree Burns
• Epidermis only
• Red and painful
• No blisters or swelling
Second Degree burns
• Entire epidermis and part of dermis
• Erythema (red)
• Pain
• Blistering occurs
Third degree burns/ Full thickness
• Entire thickness of the skin
• Surface is leathery
• May be brown, black, tan, white or red
• Not painful
Fourth degree burn
• Burn that goes through entire thickness all the way to muscle or bone
Burns are critical if:
• Second degree burn >25% of body
• Third degree burn
– >10%
– On face, hands or feet
• Any 4th degree burn
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