1. Chapter 5 The Integumentary System
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Integumentary System
The body’s covering
Includes: skin, nails, and hairs
Skin: cutaneous membrane
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Structure
Two main parts
Epidermis - surface epithelial layer
Dermis - deeper connective tissue layer
Subcutaneous (subQ) layer or hypodermis lies deep to dermis; is not part of the skin
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Integumentary System
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Epidermis
Keratinized stratified squamous epithelium
Cell types (4):
Keratinocytes
Melanocytes
Langerhans cells
Merkel cells
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Epidermal Cells
Keratinocytes
90% of epidermal cells
4-5 layers
Produce keratin
Protects skin
Waterproofs skin
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Epidermal Cells
Melanocytes
Produce melanin that gives color to skin, hairs
Transfer pigment to keratinocytes
Make up 8% of epidermal cells
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Langerhans cells
Immune response
Merkel cells
Sense of touch
Consist of tactile disc and neuron for touch sensation
Free nerve ending
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Epidermal Layers
Four Layers (strata)
Stratum basale
Includes stem cells; new cells arise here
Stratum spinosum: 8-10 cell layer
Cells beginning to look flattened
Stratum granulosum makes keratin
Losing cell organelles and nuclei
Have waterproofing lipid
Stratum corneum: flattened dead cells
Cells here consist mostly of keratin.
Cells here are shed and replaced from below.
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Skin Color
Melanin: dark color
Darkness depends on amount of melanin produced.
Provides some protection against UV rays
Carotene: yellow orange
In stratum corneum and adipose layers-
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Skin Color
Genetic Factors
Amount of melanin – determined by DNA
varying size of melanin granules
albinos lack melanin
Physiological Factors – affect skin color but not melanin production
Hemoglobin in dermal blood vessels = pink
Lack of hemoglobin in dermal blood vessels = blue (cyanosis)
Inability to breakdown hemoglobin (liver problems) = jaundice - yellow
Environmental Factors
UV rays
chemicals
Drugs (antihistamines & antibiotics)
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Dermis
binds epidermis to underlying tissues
smooth muscle cells
nerve cell processes
blood vessels
hair follicles
glands – sweat & sebaceous
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13. Dermis: 2 distinct layers
Papillary Layer – 20% below epidermis
Loose areolar CT
Surface forms dermal papillae (fingerprints)
Meissner’s Corpuscles
Reticular layer – 80% dense irregular CT
Bundles of collagen, elastic, & reticular fibers
Strength & resiliency
Pacinina corpuscles
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Cutaneous Sensation
Light touch detection – Meissner’s Corpuscle’s
Egg-shaped
Located in dermal papillae
Fingertips, palms, soles, eyelids, tip of tongue, nipples, clitoris, tip of penis
Pressure detection – Pacinian Corpuscle’s
Onion-shaped
Located in deep dermis and subcutaneous regions
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Dermis
Main function = nourishment of epidermis
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Hair
Found on most skin surfaces
Not on palmar surfaces of hand and fingers or plantar surfaces of feet
Made of fused keratinized cells
Nerves in hair root plexuses
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Hair Follicles
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Hair Follicles
Structure
Root or base in deep dermis
Follicle throughout dermis
Hair shaft in epidermis
Keratinization
Cells in root = active mitosis
Cells in follicle = maturing & accumulating keratin
Cells in epidermis = dead epithelial cells; full of keratin = exposed hair or hair shaft
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Arrector Pili Muscle
Bundle of smooth muscle associated with every hair follicle
Causes hair to stand on end (“goose bumps”) when frightened or cold
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Hair
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Glands
Sebaceous gland: secrete oily sebum
Connected to hair follicles; keeps hair from drying out
Disorders
acne - hypersecretion of sebum; ducts clog & inflame
seborrhea – hypersecretion of sebum; oily scales
Sudoriferous (sweat) gland
Merocrine/Eccrine sweat gland
Wide distribution- thermoregulation
Apocrine sweat gland
Axilla, groin, areolae, beard
Contain other cell material
Ceruminous (wax) gland
Modified apocrine gland
Wax combines with sebum = earwax
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22. Merocrine (Eccrine) Glands
Structure
Coil in deep dermis
Duct in dermis
Pore at surface
Characteristics
Respond to elevated T/exercise
No odor in secretion
Function throughout life
Not associated with hair follicles
Location: forehead, neck, back
Secretion (merocrine) = water plus
Salts & wastes (urea & uric acid)
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Apocrine Glands
Structure:
ducts terminate into hair follicles
Characteristics
Respond to stress/emotions
Odor in secretion
Begin to function at puberty & continue through life
Location: armpits, groin
Secretion (apocrine) = sweat plus
Oil & cellular debris
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Nails
nail plate
nail bed
lunula – active mitosis
Functions
Manipulation
Protection of digit ends
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Nails
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Nails
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27. Subcutaneous Layer = Adipose Tissue
also called hypodermis – beneath the skin
function = insulation
major blood vessels
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28. Functions of Integumentary System
Temperature regulation
Protection
Sensory reception
Excretion and absorption: small amounts
Vitamin D synthesis
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Heat production & Loss
Heat production is mostly a by-product of cellular metabolism
Heat is maintained through Negative feedback
Heat Loss is controlled by regulating dermal blood flow
Vasodilation – increases dermal blood flow, which also increases heat loss
Vasoconstriction – decreases dermal blood flow which decreases heat loss
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30. Low body T require heat loss to be minimized
Hypothalamus signals for sweating to decrease & dermal vasoconstriction
Usually brings the body T back to normal
If body T remains low after above action
Heat must be produced
Shivering occurs & tiny muscle contractions involved produce heat
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31. Problems in Temperature Regulation
Hyperthermia – abnormally high body temperature
Two common causes
Humid air decreases evaporation
Air T exceeds body T, thus heat is gained not lost
Hypothermia – abnormally low body temperature
Very dangerous if core body T drops below 94 degrees F
Limbs can withstand about 65 degrees F because they contain no
vital organs
Cause is intentional during some surgical procedures
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Hypothermia
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Protection
Physical Barrier
From water loss
From injury
From chemicals & microorganism growth
Chemical barrier pH
Prevents microorganism growth
Biological barrier
Langerhan’s cells (epidermis)
Macrophages and mast cells (dermis)
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Excretion
Minimal, most through kidneys
Urea
Uric acid
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Vitamin D Synthesis
UV rays in sunlight activate its synthesis
Vitamin D is required for bone homeostasis
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Blood Reservoir
The dermis houses about 10% of the body’s blood vessels
Skin only requires 1-2% of the body’s blood
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Immunity
Langerhan’s cells (macrophages)
Interact with T-helper cells in immune responses
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38. Healing of Wounds & Burns
Inflammation – process that involves blood flow changes & chemical signaling leading to healing
Cuts:
Epidermal cuts – closed by increased cell division in the stratum basale
Deep cuts involve blood vessel damage resulting in
Inflammation
Blood clotting
Scab formation
Fibroblast infiltration & repair
Scab falls off
Scar may or may not remain
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Healing of Burns
First degree burn – superficial partial-thickness
Epidermis only
Reddening due to increased blood flow
Mild pain
Common in sunburn
Heals in a few days – 2 weeks
Second degree burn – deep partial-thickness
Epidermis & some dermal damage
Reddening & blistering caused by blood vessel damage
Moderate pain
Common to physical contact with hot objects
Heals in 2-6 weeks without scars unless infected
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40. Third degree burn – full-thickness
Epidermis, entire dermis, & potentially subcutaneal damage
Dry, leathery tissue with red or black color
Severe pain
Caused by prolonged heat or chemical contact
Healing rarely occurs due to lack of surviving skin cells, skin replacements (grafts) are usually needed
autograft – transplant form undamaged area of yourself
homograft - temporary transplant from cadaver
various skin substitutes
extensive scars
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41. Healing of Wounds & Burns
Burns - Body surface affected
Estimated by “rule of nines”
Important for determining treatment & prognosis
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Rule of Nines
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Aging
Adolescence: can develop acne
Visible signs of aging by about age 40. These include:
Loss of collagen fibers
Loss of elasticity
Loss of immune responses
Decreased melanocyte functions:
gray hair, skin blotches
Thinning of skin and hairs
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Clinical Application
Acne Vulgaris
most common skin disorder
sebum and epithelial cells clog glands
produces whiteheads and blackheads (comedones)
anaerobic bacteria trigger inflammation (pimple)
largely hormonally induced
androgens stimulate sebum production
treatments include antibiotics, topical creams, birth control pills
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Skin Cancer - ABCD
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End of Chapter 5
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