Anatomy and
Physiology
Chapter 5
Etymological
Breakdown of
the Term
Integumentar
y System:
• Integument-: Derived from the Latin root integumentum, which
means "a covering," "disguise," or "cloak" (stemging from
integere, meaning to cover or protect).
• -ary: A standard adjectival suffix meaning "pertaining to" or
"relating to.”
• System: Derived from the Greek systēma, meaning a "organized
whole" or a "combination of parts" working together.
Put it all together, and the integumentary system literally translates
to the system relating to the body's covering (the skin, hair, nails,
and associated glands that protect the body as an organized unit).
Overview of the
Integumentary System
The Skin and Beyond:
• While commonly called the skin, the integumentary system is actually a
complex organ system.
• Includes the skin (cutaneous membrane) plus its accessory structures: hair,
nails, and sweat and sebaceous (oil) glands.
Scale & Importance:
• The skin is the largest organ of the body, accounting for about 16 percent of
body weight (16 to 20 pounds average adult) and covering a surface area of
1.5 to 2 square meters.
Primary Functions:
• Acts as the immediate barrier protecting the body from pathogens, chemicals,
and mechanical injury.
• Prevents fluid loss and regulates body temperature and sensation.
Clinical Significance:
• Often reflects overall health; changes in color, texture, or integrity can
indicate underlying systemic diseases (e.g., cardiovascular, respiratory, or
liver conditions).
https://www.researchgate.net/
Overview of
Skin Layers
Dual-Layered Organ:
• The skin consists of two main, distinct
layers resting on a supportive subcutaneous layer.
1. Epidermis:
• The superficial, outermost layer of the
skin.
• Composed of keratinized stratified
squamous epithelium.
• Avascular (receives nutrients via diffusion
from the dermis below).
2. Dermis:
• The deeper layer lying directly beneath the epidermis.
• Composed of connective tissue (areolar
and dense irregular).
• Vascularized; houses blood vessels,
lymphatic vessels, nerves, hair follicles,
and sweat glands.
Overview of Skin
Layers
3. Hypodermis (Subcutaneous
Layer / Superficial Fascia):
• Technically not part of the skin itself,
but closely associated.
• Composed of loose areolar and
adipose tissue; anchors skin to
underlying muscle and bone while
providing insulation and cushioning.
https://quizlet.com/
Thick Skin vs. Thin Skin (Epidermal Layers)
Classification Criteria:
• Skin is categorized as either "thick" or "thin" based on the number of epidermal layers and the depth of the stratum corneum, not the total
thickness of the skin organ as a whole.
Thin Skin:
• Contains four layers (stratum basale, spinosum, granulosum, and corneum). NOTE: These are listed from deep to superficial
• Lacks the stratum lucidum.
• Covers the vast majority of the body surface and contains hair follicles and sebaceous glands.
Thick Skin:
• Contains five layers (features the translucent stratum lucidum).
• Found only on areas subject to heavy friction and abrasion: the palms of the hands and the soles of the feet.
• Features a much thicker stratum corneum and lacks hair follicles and sebaceous glands.
https://med.libretexts.org/
Cells of the Epidermis
1. Keratinocytes:
• The most abundant cells in the epidermis (approx. 90%).
• Synthesize keratin, a tough, fibrous protein that gives skin its hardness, durability, and water-resistant properties.
• Continuously produced by stem cells in the deepest layer, pushing upward and eventually shedding.
2. Melanocytes:
• Located in the deepest epidermal layer.
• Produce the pigment melanin, which absorbs UV radiation and protects deeper cell DNA; transferred to keratinocytes.
3. Langerhans Cells:
• Dendritic cells functioning as macrophages in the epidermis.
• Engulf bacteria, foreign particles, and damaged cells to trigger an immune response.
4. Merkel Cells:
• Receptor cells located in the deepest layer that function as touch
receptors, associating with sensory nerve endings.
Cells of the Epidermis
Layers (Strata) of the
Epidermis
Layers (Strata) of the
Epidermis
1. Stratum Basale (Basal Layer / Stratum Germinativum):
• Deepest single layer; attached to the basement membrane and underlying dermis.
• Forms a wavy boundary by interlocking with upward projections of the dermis called
dermal papillae, increasing surface area and strengthening the epidermal-dermal
bond to prevent shearing (enhancing grip).
• The stratum basale is a single layer of cells primarily made of basal cells.
• Site of continuous mitotic cell division (cuboidal stem cells) that continually produce
new keratinocytes.
• Houses melanocytes (pigment producers) and Merkel cells (touch receptors).
2. Stratum Spinosum ("Spiny Layer"):
• 8 to 10 layers of keratinocytes connected by strong desmosomes, giving a spiny
appearance under a microscope.
• Contains maturing keratinocytes and Langerhans cells.
• Keratinocytes in the stratum spinosum begin the synthesis of keratin and release a
water-repelling glycolipid.
https://www.flickr.com/photos/187096960@N06/51172620298
Layers (Strata) of the
Epidermis
1. Stratum Basale (Basal Layer / Stratum Germinativum):
• Deepest single layer; attached to the basement membrane and underlying dermis.
• Forms a wavy boundary by interlocking with upward projections of the dermis called
dermal papillae, increasing surface area and strengthening the epidermal-dermal
bond to prevent shearing (enhancing grip).
• The stratum basale is a single layer of cells primarily made of basal cells.
• Site of continuous mitotic cell division (cuboidal stem cells) that continually produce
new keratinocytes.
• Houses melanocytes (pigment producers) and Merkel cells (touch receptors).
2. Stratum Spinosum ("Spiny Layer"):
• 8 to 10 layers of keratinocytes connected by strong desmosomes, giving a spiny
appearance under a microscope.
• Contains maturing keratinocytes and Langerhans cells.
• Keratinocytes in the stratum spinosum begin the synthesis of keratin and release a
water-repelling glycolipid.
https://www.flickr.com/photos/187096960@N06/51172620298
Layers (Strata) of the
Epidermis
3. Stratum Granulosum ("Granular Layer"):
• 3–5 layers deep; cells flatten and fill with
keratin, keratohyalin granules, and lamellar granules (waterproofing glycolipids).
• Organelles disintegrate and cell death occurs as cells are pushed further from the blood
supply.
4. Stratum Lucidum ("Clear Layer"):
• Thin, translucent layer of dead, flattened cells
packed with eleidin.
• Found only in thick skin (palms of hands and
soles of feet).
5. Stratum Corneum ("Horny Layer"):
• Superficial layer consisting of 15–30 layers of flat, dead, keratin-filled cells.
• Provides a durable, waterproof barrier against microbes, dehydration, and mechanical
abrasion; continuously sloughed off.
Layers (Strata) of the
Epidermis
The Dermis:
Regions &
Structure
General Characteristics:
• The "core" of the cutaneous system; houses blood vessels,
sweat glands, oil glands, hair follicles, and nerve endings.
• Consists of two layers of connective tissue that compose an
interconnected mesh of elastin and collagenous fibers,
produced by fibroblasts.
1. Papillary Layer:
• Upper 20% of the dermis; composed of loose areolar
connective tissue with a loose meshwork of collagen and
elastic fibers.
• Features dermal papillae that project upward into the
epidermis, forming unique epidermal ridges (fingerprints) that
enhance grip.
• Contains rich capillary loops that nourish the avascular
epidermis via diffusion and help regulate body temperature
and lymphatic capillaries.
• Packed with sensory nerve endings, including Meissner
corpuscles (receptors sensitive to light touch) and free nerve
endings that detect pain and temperature.
• 2. Reticular Layer:
• Deeper, thicker 80% of the dermis; composed of dense
irregular connective tissue.
• Packed with thick bundles of collagen fibers (for structural
strength and tensile resilience) and elastic fibers (for skin
stretch and recoil).
• Contains larger blood vessels, sweat/sebaceous glands, and
Pacinian corpuscles (deep pressure receptors).
Papillary layer also contains fibroblasts,
some fat cells (adipocytes), and phagocytes.
Meissner corpuscles
https://neuroscientificallychallenged.com/glossary/meissners-corpuscles https://histology.siu.edu/intro/Meissners2.htm
The Dermis: Regions &
Structure
• Papillary layer also contains fibroblasts, some
fat cells (adipocytes), mast cells, and
phagocytes.
https://www.enhance-me-training.com/topic/the-dermis/
The
Hypodermis
(Subcutaneo
us Layer)
Position & Anatomy:
• Located directly beneath the reticular layer of the dermis.
• Technically not part of the skin proper, but rather a connective tissue layer that anchors
the skin to underlying bone and muscle.
• Composed primarily of loose areolar connective tissue and adipose tissue (fat cells).
Vascular Supply:
• Highly vascularized; contains large blood vessels that supply the skin and serve as a
common site for subcutaneous injections (hypodermic needles).
Primary Functions:
• Energy Storage: Adipocytes store triglycerides as an energy reserve.
• Insulation & Protection: The fat layer provides thermal insulation against heat loss
and acts as a shock-absorbing cushion to protect underlying structures from
mechanical trauma.
Skin
Pigmentation &
Color
Determinants
1. Melanin:
• Produced by melanocytes; primary
pigment determining skin color.
• Exists in two primary forms: eumelanin
(brown/black) and pheomelanin
(red/yellow).
• UV exposure stimulates tyrosinase
enzyme activity, increasing melanin
production (tanning) to shield cell
nuclei from DNA damage.
• Freckles and moles represent
localized accumulations of melanin.
2. Carotene:
• A yellow-orange pigment obtained
from plant-based foods (e.g., carrots,
sweet potatoes) that can accumulate
in the stratum corneum and
hypodermis.
3. Hemoglobin:
• The red oxygen-transporting protein in
red blood cells.
• Imparts a pinkish or red tint to the skin
as blood flows through the dermal
capillaries, particularly visible in
lighter-skinned individuals when
oxygenated.
Carotenodermia https://www.nejm.org/doi/abs/10.1056/NEJMicm950425
https://en.wikipedia.org/wiki/Jaundice
https://www.azolifesciences.com/
Integumentary System Disorders
Overview of
Accessory
Structures
Definition:
• Structures that originate from the
epidermis and extend down into the
dermis or hypodermis.
Key Components:
• Hair
• Nails
• Sweat (Sudoriferous) Glands
• Sebaceous (Oil) Glands
General Function:
• While embedded in the skin, these
structures play critical roles in protection,
sensory input, thermoregulation, and
excretion.
https://www.mayoclinichealthsystem.org/
https://www.harleystreethairtransplants.org/
Hair Structure
and Growth
Anatomy of a Hair:
• Shaft: The portion of the hair exposed above the
skin surface (completely dead, keratinized cells).
• Root: The portion of hair anchored within the
follicle below the skin surface.
• Hair Bulb: The expanded base of the root
surrounding the hair papilla (which contains blood
vessels and nerves).
Layers of the Hair:
• Medulla: The central core of the hair.
• Cortex: The middle layer providing strength and
pigment.
• Cuticle: The outermost layer of overlapping, single
cells protecting the inner layers.
Follicle & Arrector Pili:
• Surrounded by a root sheath and connected to an
involuntary smooth muscle called the arrector
pili, which contracts to pull hair upright
("goosebumps" in response to cold or fear) and is
controlled by the sympathetic nervous system.
• This traps a layer of air to add insulation
https://www.toppik.com/
Internal Root Sheath
Layers of the
Hair Follicle
External Root Sheath
• Structure: Surrounds the growing hair root up to the hair shaft.
• Origin: Derived from the basal cells of the hair matrix.
Wall
• Structure: Encloses the hair root as a direct extension of the epidermis.
• Characteristics: Composed of basal cells at the base; becomes increasingly
keratinous toward the upper regions.
Glassy Membrane
• Structure: A thick, clear connective tissue sheath covering the hair root.
• Function: Connects the hair follicle directly to the surrounding dermal tissue.
Root Hair
Plexuses (Hair
Follicle
Receptors)
• Histological Definition: Specialized networks of
unmyelinated sensory nerve fibers that wrap intricately
around and entwine within the external root sheath of hair
follicles.
• Anatomical Position: Located in the dermal portion of the
hair follicle wall, typically positioned just inferior to the
entrance of the sebaceous gland ducts.
• Functional Role: Act as rapid-adapting
mechanoreceptors (tactile receptors) responsible for
detecting fine, light-touch stimuli.
• Mechanism of Action:
• Deflection of the hair shaft (from wind, clothing, or
a crawling insect) acts as a mechanical lever.
• Movement physically shifts the follicular wall and
deforms the entwined nerve endings.
• Mechanical deformation opens mechanically-
gated ion channels, triggering action potentials
that travel via sensory neurons to the central
nervous system.
• Clinical/Physiological Significance: Highly sensitive to
initial directional movement, providing early cutaneous
awareness of external environmental contact before
deeper touch receptors are engaged.
https://quizlet.com/ca/443370620/hair-and-nails-flash-cards/
https://www.nisenet.org/catalog/scientific-image-human-hair
Hair Growth Cycle &
Dynamics
• Anagen Phase (Growth): Rapid cell division
at the root pushes the hair shaft upward at
~0.3 mm/day; lasts 2 to 7 years.
• Catagen Phase (Transition): A brief 2 to 3
week transitional period marking the end of
active follicular growth.
• Telogen Phase (Resting): Lasts 2 to 4
months with no new growth, culminating in a
new anagen phase that sheds the old hair.
• Shedding & Loss: Average daily loss is 50
hairs; excessive loss exceeding replacement
results from aging, hormonal fluctuations, or
dietary changes.
https://www.pinterest.com/pin/halloween-hair--417638565445540250/
Sweat (Sudoriferous)
Glands
Function:
• Produce sweat to cool the body via evaporative cooling
and excrete metabolic wastes.
1. Eccrine (Merocrine) Sweat Glands:
• More common; distributed across nearly the entire skin
surface (especially palms, soles, and forehead).
• Produce a hypotonic fluid (water, salts, metabolic
wastes) released via exocytosis directly onto the skin
surface for thermoregulation.
2. Apocrine Sweat Glands:
• Confined to areas with hair follicles (e.g., armpits and
genital regions).
• Larger glands that release a thicker, organic-rich (in
addition to water and salts) secretion into hair follicles,
which is metabolized by bacteria to produce body odor;
become active starting at puberty.
• The release of this sweat is under both nervous and
hormonal control
https://en.wikipedia.org/wiki/Apocrine_sweat_gland
Sebaceous
(Oil) Glands
Definition:
• Exocrine glands associated with hair follicles found all
over the body except on the palms and soles.
Secretion (Sebum):
• Produce sebum, a mixture of lipids, cholesterol, and
proteins.
Functions of Sebum:
• Lubricates and waterproofs the skin and hair, preventing
them from drying out.
• Possesses antibacterial properties to inhibit the growth of
microorganisms on the skin surface.
Mode of Secretion:
• Holocrine secretion: cells accumulate sebum until they
rupture and destroy themselves, releasing their product
(replaced by mitotic division of basal cells).
https://quizlet.com/ca/443370620/hair-and-nails-flash-cards/
Nails
Structure & Composition:
• Specialized accessory structures composed of densely packed, dead, heavily keratinized epidermal cells.
Key Anatomical Features:
• Nail Body (Plate): The visible hard plate covering the dorsal surface of the fingertip/toe.
• Nail Bed: The specialized skin underlying the nail body, richly supplied with blood vessels (giving it a pink
color).
• Nail Root: The deep epidermal fold under the skin where nail production begins.
• Eponychium (Cuticle): The fold of epithelial tissue that overlaps the proximal edge of the nail body.
• Lunula: The thick, crescent-shaped whitish area at the base of the nail body overlying the thick nail matrix.
Primary Functions:
• Protects the distal tips of fingers and toes from trauma and enhances precision grip for picking up small
objects.
Overview of Integumentary
Functions
Primary Role:
• The skin and its accessory structures function as an
integrated organ system that maintains homeostasis and protects the body.
Core Physiological Functions:
• Protection: Acts as a physical and chemical barrier
against external elements.
• Sensation: Detects environmental stimuli via
specialized receptors.
• Thermoregulation: Modulates body temperature
through sweat and blood vessel adjustments.
• Vitamin D Synthesis: Produces a crucial hormone
essential for calcium absorption.
Protection (The Body's Armor)
Physical & Chemical Barrier:
• Protects underlying vital organs from mechanical injury, UV
radiation, wind, and water.
Dehydration Prevention:
• Layers of tough keratin and water-resistant glycolipids in the
stratum corneum prevent excessive fluid loss.
Microbial Defense:
• Acts as a first line of defense against pathogens, abrasive grit,
and harmful chemicals.
• Sweat contains dermcidin, which possesses antibiotic
properties to deter microbe over-colonization.
Immune Protection:
• Langerhans (dendritic) cells patrol epidermal layers to intercept
foreign invaders and trigger immune responses.
https://uen.pressbooks.pub/anatomyphysiology/chapter/epidermis/
Langerhan
s
(Dendritic)
Cells
(APC’s)
https://courses.lumenlearning.com/wm-biology2/chapter/antigen-presenting-cells/
Sensation (Sensory Function)
Environmental Awareness:
• The integumentary system contains a rich network of
specialized nerve endings and receptors across the
epidermis, dermis, and hypodermis.
Key Sensory Receptors:
• Meissner (Tactile) Corpuscles: Highly concentrated in
fingertips; respond to light touch.
• Pacinian (Lamellated) Corpuscles: Detect deep
pressure and vibration.
• Merkel Cells & Hair Root Plexuses: Detect fine touch
and minor hair disturbances (e.g., sensing an insect
crawling on the skin).
Pain & Temperature:
• Free nerve endings distributed throughout the skin
monitor noxious stimuli, temperature shifts, and physical
trauma.
Sensation (Sensory Function)
• Merkel cells (Tactile discs): Located in the deep layer of the epidermis (stratum basale),
these are slow-adapting receptors that excel at detecting sustained touch, fine detail, texture, and edges. When pressed, they release signaling molecules that excite adjacent nerve endings, providing high-resolution tactile feedback (like reading Braille or feeling a smooth surface).
• Meissner corpuscles (Tactile corpuscles): Situated in the dermal papillae of hairless
(glabrous) skin, such as your fingertips and lips, these are rapid-adapting receptors. They fire intensely when skin first makes contact with an object and when it loses contact,
making them exceptionally sensitive to light touch, low-frequency vibration, and slippage (helping you adjust your grip on a moving object).
• Pacinian corpuscles (Lamellar corpuscles): Found deep in the dermis and subcutaneous
layer, these large, onion-shaped receptors are rapidly adapting and exquisitely sensitive to deep pressure and high-frequency vibration. Because of their layered capsule, steady pressure is filtered out, allowing them to fire only when vibration or sudden mechanical shifts occur (such as feeling a drill vibrate or walking on a rough surface).
• Hair root plexus (Hair follicle receptors): A web of sensory nerve fibers wrapped around
the base of hair follicles. These rapid-adapting mechanoreceptors detect the bending or movement of hairs. Even a light breeze or an insect crawling across your arm displaces a hair, triggering the surrounding nerve plexus and providing an early warning system for tactile movement across hairy skin.
Pacinian
Corpuscle
(Sensory Organ)
Pacinian Corpuscle Anatomy: Encapsulated, onion-like
mechanoreceptor for deep pressure and vibration.
• The Capsule & Outer Lamination: Dense connective
tissue outer envelope and flattened lamellar cells
that filter out steady pressure.
• Viscous Gel: Interstitial fluid between layers that
shifts hydraulically to dampen sustained forces,
driving rapid adaptation.
• Inner Lamination: Tightly packed, specialized
modified Schwann cells forming a core around the
central nerve terminal.
• Terminal Non-Myelinated Axon: Bare, uninsulated
nerve tip at the center with stretch-sensitive
channels that trigger action potentials when
compressed.
• Myelinated Axon: Insulated nerve fiber exiting the
corpuscle to rapidly transmit electrical impulses
toward the central nervous system via saltatory
conduction.
Thermoregulation
Sympathetic Nervous System Control :
The integumentary system works closely with the autonomic nervous system (involuntary bodily control) to
continuously monitor and adjust core body temperature.
Response to Overheating (Cooling):
• Sweating: Eccrine sweat glands secrete water and electrolytes; evaporative cooling dissipates body heat. (Note:
insensible perspiration secretes ~500 mL/day even without noticeable sweating).
• Vasodilation: Dermal blood vessels dilate to bring warm blood closer to the body surface, releasing heat into the
environment.
Response to Cold (Heat Retention):
• Vasoconstriction: Dermal arterioles constrict to minimize blood flow to the skin surface, trapping core heat
internally (can cause a pale/whitish hue).
• Shivering: Involuntary muscle contractions generate metabolic heat (assisted by the contraction of arrector pili
muscles).
Vitamin D
Synthesis
The Pathway:
• 1. Skin Activation: When epidermal cells are
exposed to ultraviolet (UV) radiation, a
cholesterol derivative in the skin converts into
cholecalciferol (Vitamin 3).
• 2. Liver Processing: The liver converts
cholecalciferol into an intermediate
compound called calcidiol.
• 3. Kidney Activation: The kidneys convert
calcidiol into calcitriol, which is the active,
functional hormone form of Vitamin D.
Physiological Importance:
• Calcitriol is essential for the normal intestinal
absorption of calcium and phosphorus, which
are strictly required for bone health, growth,
and remodeling.
https://www.researchgate.net/
Effects of Aging
on the
Integumentary
System
Epidermal & Dermal Changes:
• Mitotic activity in the stratum basale slows down,
causing the epidermis to thin.
• The dermis exhibits a reduced ability to
regenerate, leading to a loss of structural
elasticity and flexibility (manifesting as wrinkles).
• Fibroblast activity declines, resulting in
decreased production of collagen and elastic
fibers.
Vascular & Glandular Decline:
• Blood supply to the skin decreases, reducing the
skin's capacity to heal quickly and impairing
thermoregulation (leading to increased sensitivity
to cold).
• Functional activity of sweat (sudoriferous) and
sebaceous (oil) glands drops, causing dry, scaly
skin and a reduced ability to sweat effectively.
Subcutaneous & Accessory Alterations:
• The hypodermis loses fat storage over time,
contributing to a loss of padding, insulation, and a
sunken appearance.
• Melanocyte and hair follicle activity slows down,
resulting in graying or thinning hair and a reduced
capacity to protect against UV radiation.
• Immune responsiveness declines as the number
of Langerhans cells drops, increasing
susceptibility to skin infections and damage.
Overview of Skin Cancer
Definition & Cause:
• Cancer caused by abnormal, uncontrollable cell division in the skin.
• Primary culprit is overexposure to ultraviolet (UV) radiation from the sun or
tanning beds, which damages cellular DNA.
The Danger of Metastasis:
• Metastasis is the process where cancer cells break away from the primary
tumor, enter the bloodstream or lymphatic vessels, and spread to secondary
sites (such as lymph nodes, lungs, or liver), making treatment significantly
more difficult.
Types of Skin Cancer:
• Basal Cell Carcinoma (BCC): Starts in the stratum basale and spreads
along that boundary; the most common form of skin cancer, highly curable
with early treatment (common in areas exposed to the sun).
• Treatments include surgery, freezing (cryosurgery), and topical ointments
• Squamous Cell Carcinoma (SCC): Affects keratinocytes of the stratum
spinosum; presents as lesions on the scalp, ears, and hands; more
aggressive than BCC and can metastasize if left untreated.
• Surgery and radiation are used to cure SCC
• Melanoma: Uncontrolled growth of melanocytes, typically developing from a
mole; the most fatal form of skin cancer due to high rates of metastasis.
• Treatment typically involves surgical excision and immunotherapy
Basal Cell Carcinoma
Squamous Cell
Carcinoma
Melanoma
Early Detection
of Melanoma
(The ABCDE
Rule)
Clinical Screening Guidelines:
• A – Asymmetry: The two sides of the mole or lesion do not match.
• B – Borders: The edges are irregular, ragged, notched, or blurred.
• C – Color: The color is not uniform and may include different shades of
brown or black, or patches of pink, red, white, or blue.
• D – Diameter: The lesion is larger than 6 mm (about the size of a pencil
eraser), though melanomas can sometimes be smaller.
• E – Evolving: The mole is changing in size, shape, color, or elevation, or
begins to bleed/itch.
Common
Skin
Disorder
s
Introduction to Skin Disorders:
• Skin disorders range from minor localized irritations to chronic systemic conditions, often involving
inflammation, immune responses, or blocked glands.
• Disorders include psoriasis, cold sores, impetigo, scabies, hives, and warts.
Eczema:
• An inflammatory, allergic condition that presents as dry, red, itchy patches resembling rashes.
• Often accompanied by swelling, flaking, and skin cracking; managed with moisturizers, corticosteroid
creams, and immunosuppressants.
Acne:
• A skin disturbance involving the overproduction of sebum and keratin that blocks hair follicles.
• Most common during puberty due to hormonal surges (androgens) that stimulate sebaceous glands,
leading to bacterial infection and inflammation.
Skin Injuries &
The Healing
Process
Types of Injuries:
• Cuts, punctures, scrapes, and burns
caused by physical trauma, heat,
chemicals, or electricity.
• Step-by-Step Wound Healing Stages:
1. Hemostasis & Clotting: A blood clot
forms immediately to stop bleeding and
eventually dries into a protective scab.
2. Inflammation: White blood cells
(macrophages) clear out debris and fight
potential infection.
3. Proliferation: Fibroblasts migrate into the
wound bed to produce new collagen and
blood vessels (granulation tissue).
4. Remodeling & Scarring: Epithelial cells
regenerate across the wound under the scab,
while scar tissue (dense collagen) replaces
normal tissue depending on the depth of the
injury.
https://www.shieldhealthcare.com/
https://jetem.org/thermal_burns/
Burns and
Classification
s
Nature of Burns:
• Caused by intense heat, radiation, electricity, or chemicals, resulting in massive cell
death and fluid loss.
Severity Classifications:
• First-Degree (Superficial): Affects only the epidermis; results in redness and minor
pain (e.g., mild sunburn) that heals within days.
• Second-Degree (Partial-Thickness): Damages both the epidermis and upper dermis;
results in blistering and significant pain.
• Third-Degree (Full-Thickness): Destroys the full thickness of the skin (epidermis and
dermis), charring tissue and destroying nerve endings (often requiring skin grafts).
• Fourth-Degree (Full-Thickness with Deep Tissue Damage): Extends completely
through the skin down to underlying muscle, tendons, and bone; requires extensive
surgical intervention and often amputation.
Major Systemic Risks:
• Severe dehydration, electrolyte imbalance, renal/circulatory failure, and rampant
secondary infections due to lost skin barrier function.
Fourth degree Burn
https://burncenters.com/burns/evaluate-a-burn/
Common Integumentary
Abnormalities and Injury
Responses
Scars & Keloids:
• Scars: Formed when the skin repairs deep dermal damage using
collagen-rich connective tissue rather than regenerating normal
tissue.
• Lacks accessory structures (e.g., hair follicles, sweat glands, and sebaceous glands)
• Keloids: Result from an overproduction of scar tissue (collagen) that
extends beyond the original boundaries of the wound.
Bedsores (Decubitus Ulcers):
• Caused by constant, long-term pressure on bony areas that cuts off
blood supply to the skin, leading to tissue necrosis and breakdown.
Stretch Marks (Striae):
• Occur when the dermis is stretched beyond its elastic limits (e.g.,
during rapid growth, weight gain, or pregnancy), causing collagen and
elastin fibers to tear.
Calluses & Corns:
• A protective response where the stratum basale increases mitotic
activity in areas subjected to constant friction or pressure, resulting in
a thickened, hardened layer of dead cells.
https://www.healthline.com/health/keloid-ear
https://www.mayoclinic.org/diseases-conditions/corns-and-
calluses/multimedia/callus/img-20007285 https://myexpertmidwife.com/blogs/my-expert-midwife/stretch-marks-101
https://blog.xoxoday.com/empuls/get-to-know-you-questions-for-coworkers/
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