Anatomy and physiology

Torie

ch_05_lecture_presentation.pptx

Home >Biology homework help >Anatomy homework help >Anatomy and physiology

PowerPoint® Lecture Slides

prepared by

Karen Dunbar Kareiva

Ivy Tech Community College

Chapter 5

The Integumentary System

Why This Matters

Understanding the integumentary system will help you evaluate and treat injuries to the skin such as burns

Integumentary System

Integumentary system consists of:

Skin

Hair

Nails

Sweat glands

Sebaceous (oil) glands

5.1 Structure of skin

Skin consists of two distinct regions:

Epidermis: superficial region

Consists of epithelial tissue and is avascular

Dermis: underlies epidermis

Mostly fibrous connective tissue, vascular

Hypodermis (superficial fascia)

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

Figure 5.1 Skin structure.

Hair shaft

Dermal papillae

Epidermis

Papillary

layer

Subpapillary

plexus

Sweat pore

Appendages of skin

• Eccrine sweat gland

• Arrector pili muscle

• Sebaceous (oil) gland

• Hair follicle

• Hair root

Dermis

Reticular

layer

Hypodermis

(subcutaneous

tissue; not part

of skin)

Cutaneous plexus

Nervous structures

• Sensory nerve fiber

with free nerve endings

• Lamellar corpuscle

• Hair follicle receptor

(root hair plexus)

Adipose tissue

5.2 Epidermis

Cells of the Epidermis

Epidermis consists mostly of keratinized stratified squamous epithelium

Four cell types found in epidermis:

Keratinocytes

Produce fibrous keratin (protein that gives skin its protective properties)

Major cells of epidermis

Tightly connected by desmosomes

Millions slough off every day

Figure 5.2 Epidermal cells and layers of the epidermis.

Keratinocytes

Stratum corneum

Most superficial layer; 20–30 layers of dead

cells, essentially flat membranous sacs

filled with keratin. Glycolipids in

extracellular space.

Stratum granulosum

Typically one to five layers of flattened

cells, organelles deteriorating; cytoplasm

full of lamellar granules (release lipids) and

keratohyaline granules.

Stratum spinosum

Several layers of keratinocytes unified by

desmosomes. Cells contain thick bundles

of intermediate filaments made of

pre-keratin.

Stratum basale

Deepest epidermal layer; one row of actively

mitotic stem cells; some newly formed cells

become part of the more superficial layers.

See occasional melanocytes and dendritic

cells.

Dermis

Melanin

granule

Dermis

Sensory

nerve

ending

Tactile

(Merkel)

cell

Desmosomes

Dendritic cell

Melanocyte

Cells of the Epidermis (cont.)

Melanocytes

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

Dendritic (Langerhans) cells

Star-shaped macrophages that patrol deep epidermis

Are key activators of immune system

Tactile (Merkel) cells

Sensory receptors that sense touch

Layers of the Epidermis

Epidermis is made up of four or five distinct layers

Thick skin contains five layers (strata) and is found in high-abrasion areas (hands, feet)

Thin skin contains only four strata

Five layers of skin

Stratum basale

Stratum spinosum

Stratum granulosum

Stratum lucidum (only in thick skin)

Stratum corneum

Layers of the Epidermis (cont.)

Stratum basale (basal layer)

Deepest of all epidermal layers (base layer)

Layer that is firmly attached to dermis

Consists of a single row of stem cells that actively divide (mitotic), producing two daughter cells each time

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

Layer also known as stratum germinativum because of active mitosis

10–25% of layer also composed of melanocytes

Layers of the Epidermis (cont.)

Stratum spinosum (prickly layer)

Several cell layers thick

Cells contain weblike system of intermediate prekeratin filaments attached to desmosomes

Allows them to resist tension and pulling

Keratinocytes in this layer appear spikey, so they are called prickle cells

Scattered among keratinocytes are abundant melanosomes and dendritic cells

Layers of the Epidermis (cont.)

Stratum granulosum (granular layer)

Four to six cells thick, but cells are flattened, so layer is thin

Cell appearance changes

Cells flatten, nuclei and organelles disintegrate

Keratinization begins

Cells accumulate keratohyaline granules that help form keratin fibers in upper layers

Cells also accumulate lamellar granules, a water-resistant glycolipid that slows water loss

Cells above this layer die

Too far from dermal capillaries to survive

Layers of the Epidermis (cont.)

Stratum lucidum (clear layer)

Found only in thick skin

Consists of thin, translucent band of two to three rows of clear, flat, dead keratinocytes

Lies superficial to the stratum granulosum

Layers of the Epidermis (cont.)

Stratum corneum (horny layer)

20–30 rows of flat, anucleated, keratinized dead cells

Accounts for three-quarters of epidermal thickness

Though dead, cells still function to:

Protect deeper cells from the environment

Prevent water loss

Protect from abrasion and penetration

Act as a barrier against biological, chemical, and physical assaults

Layers of the Epidermis (cont.)

Cells change by going through apoptosis (controlled cell death)

Dead cells slough off as dandruff and dander

Humans can shed ~50,000 cells every minute

Figure 5.2 Epidermal cells and layers of the epidermis.

Keratinocytes

Stratum corneum

Most superficial layer; 20–30 layers of dead

cells, essentially flat membranous sacs

filled with keratin. Glycolipids in

extracellular space.

Stratum granulosum

Typically one to five layers of flattened

cells, organelles deteriorating; cytoplasm

full of lamellar granules (release lipids) and

keratohyaline granules.

Stratum spinosum

Several layers of keratinocytes unified by

desmosomes. Cells contain thick bundles

of intermediate filaments made of

pre-keratin.

Stratum basale

Deepest epidermal layer; one row of actively

mitotic stem cells; some newly formed cells

become part of the more superficial layers.

See occasional melanocytes and dendritic

cells.

Dermis

Melanin

granule

Dermis

Sensory

nerve

ending

Tactile

(Merkel)

cell

Desmosomes

Dendritic cell

Melanocyte

5.3 Dermis

Strong, flexible connective tissue

Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells

Fibers in matrix bind body together

Makes up the “hide” that is used to make leather

Contains nerves, blood vessels, and lymphatic vessels

Contains epidermal hair follicles, oil glands, and sweat glands

Two layers

Papillary

Reticular

Figure 5.3 Light micrograph of the dermis.

Epidermis

Papillary

layer

Dermis

Reticular

layer

Figure 5.1 Skin structure.

Hair shaft

Dermal papillae

Epidermis

Papillary

layer

Subpapillary

plexus

Sweat pore

Appendages of skin

• Eccrine sweat gland

• Arrector pili muscle

• Sebaceous (oil) gland

• Hair follicle

• Hair root

Dermis

Reticular

layer

Hypodermis

(subcutaneous

tissue; not part

of skin)

Cutaneous plexus

Nervous structures

• Sensory nerve fiber

with free nerve endings

• Lamellar corpuscle

• Hair follicle receptor

(root hair plexus)

Adipose tissue

Papillary Layer

Superficial layer of areolar connective tissue consisting of loose, interlacing collagen and elastic fibers and blood vessels

Loose fibers allow phagocytes to patrol for microorganisms

Dermal papillae: superficial region of dermis that sends fingerlike projections up into epidermis

Projections contains capillary loops, free nerve endings, and touch receptors (tactile corpuscles, also called Meissner’s corpuscles)

Papillary Layer (cont.)

In thick skin, dermal papillae lie on top of dermal ridges, which give rise to epidermal ridges

Collectively ridges are called friction ridges

Enhance gripping ability

Contribute to sense of touch

Sweat pores in ridges leave unique fingerprint pattern

Figure 5.4a Dermal modifications result in characteristic skin markings.

Openings of

sweat gland

ducts

Friction

ridges

Friction ridges of

fingertip (SEM 12×)

Reticular Layer

Makes up ~80% of dermal thickness

Consists of coarse, dense fibrous connective tissue

Many elastic fibers provide stretch-recoil properties

Collagen fibers provide strength and resiliency

Bind water, keeping skin hydrated

Cutaneous plexus: network of blood vessels between reticular layer and hypodermis

Extracellular matrix contains pockets of adipose cells

Reticular Layer (cont.)

Cleavage (tension) lines in reticular layer are caused by many collagen fibers running parallel to skin surface

Externally invisible

Important to surgeons because incisions parallel to cleavage lines heal more readily

Figure 5.4b Dermal modifications result in characteristic skin markings.

Cleavage lines in the

reticular dermis

Reticular Layer (cont.)

Flexure lines of reticular layer are dermal folds at or near joints

Dermis is tightly secured to deeper structures

Skin’s inability to slide easily for joint movement causes deep creases

Visible on hands, wrists, fingers, soles, toes

Figure 5.4c Dermal modifications result in characteristic skin markings.

Flexure

lines

on digit

Flexure

lines

on the

palm

Flexure lines of the

hand

Clinical – Homeostatic Imbalance 5.1

Extreme stretching of skin can cause dermal tears, leaving silvery white scars called striae

Also known as “stretch marks”

Acute, short-term traumas to skin can cause blisters, fluid-filled pockets that separate epidermal and dermal layers

Figure 5.5 Stretch marks (striae).

5.4 Skin Color

Three pigments contribute to skin color

Melanin

Only pigment made in skin; made by melanocytes

Packaged into melanosomes that are sent to keratinocytes to shield DNA from sunlight

Sun exposure stimulates melanin production

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

5.4 Skin Color

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

Hemoglobin

Pinkish hue of fair skin is due to lower levels of melanin

Skin of Caucasians is more transparent, so color of hemoglobin shows through

Clinical – Homeostatic Imbalance 5.2

Excessive sun exposure damages skin

Elastic fibers clump, causing skin to become leathery

Can depress immune system and cause alterations in DNA that may lead to skin cancer

UV light destroys folic acid

Necessary for DNA synthesis, so insufficient folic acid is especially dangerous for developing embryos

Photosensitivity is increased reaction to sun

Some drugs (e.g., antibiotics, antihistamines) and perfumes cause photosensitivity, leading to skin rashes

Clinical – Homeostatic Imbalance 5.3

Alterations in skin color can indicate disease

Cyanosis

Blue skin color: low oxygenation of hemoglobin

Erythema (redness)

Fever, hypertension, inflammation, allergy

Pallor (blanching or pale color)

Anemia, low blood pressure, fear, anger

Jaundice (yellow cast)

Liver disorders

Clinical – Homeostatic Imbalance 5.3

Alterations in skin color can indicate disease (cont.)

Bronzing

Inadequate steroid hormones (example: Addison’s disease)

Bruises (black-and-blue marks)

Clotted blood beneath skin

5.5 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

Structure of a Hair

Hairs (also called pili): flexible strands of dead, keratinized cells

Produced by hair follicles

Contains hard keratin, not like soft keratin found in skin

Hard keratin is tougher and more durable, and cells do not flake off

Regions:

Shaft: area that extends above scalp, where keratinization is complete

Root: area within scalp, where keratinization is still going on

Structure of a Hair (cont.)

Three parts of hair shaft:

Medulla: central core of large cells and air spaces

Cortex: several layers of flattened cells surrounding medulla

Cuticle: outer layer consisting of overlapping layers of single cells

Structure of a Hair (cont.)

Hair pigments are made by melanocytes in hair follicles

Combinations of different melanins (yellow, rust, brown, black) create all the hair colors

Red hair has additional pheomelanin pigment

Gray/white hair results when melanin production decreases and air bubbles replace melanin in shaft

Figure 5.6ab Skin appendages: Structure of a hair and hair follicle.

Follicle wall

• Peripheral

connective tissue

(fibrous) sheath

• Glassy membrane

• Epithelial root sheath

• External root sheath

• Internal root sheath

Hair

• Cuticle

• Cortex

• Medulla

Diagram of a cross section of a hair within its follicle

Photomicrograph of a cross

section of a hair and hair

follicle (100×)

Structure of a Hair Follicle

Extends from epidermal surface to dermis

Hair bulb: expanded area at deep end of follicle

Hair follicle receptor (or root hair plexus): sensory nerve endings that wrap around bulb

Hair is considered a sensory touch receptor

Wall of follicle composed of:

Peripheral connective tissue sheath

Derived from dermis

Also called fibrous sheath

Glassy membrane: thickened basal lamina

Epithelial root sheath

Derived from epidermis

Structure of a Hair Follicle (cont.)

Hair matrix: actively dividing area of bulb that produces hair cells

As matrix makes new cells, it pushes older ones upward

Arrector pili: small band of smooth muscle attached to follicle

Responsible for “goose bumps”

Hair papilla

Dermal tissue containing a knot of capillaries that supplies nutrients to growing hair

Figure 5.6cd Skin appendages: Structure of a hair and hair follicle.

Follicle wall

• Peripheral

connective tissue

(fibrous) sheath

• Glassy membrane

• Epithelial root sheath

• External root sheath

• Internal root sheath

Hair root

• Cuticle

• Cortex

• Medulla

Hair matrix

Hair papilla

Melanocyte

Subcutaneous

adipose tissue

Diagram of a longitudinal view of the expanded hair

bulb of the follicle, which encloses the matrix

Photomicrograph of longitudinal view

of the hair bulb in the follicle (150×)

Types and Growth of Hair

Vellus hair: pale, fine body hair of children and adult females

Terminal hair: coarse, long hair

Found on scalp and eyebrows

At puberty

Appear in axillary and pubic regions of both sexes

Also on face and neck of males

Nutrition and hormones affect hair growth

Follicles cycle between active and regressive phases

Average 2.25 mm growth per week

Lose 90 scalp hairs daily

Clinical – Homeostatic Imbalance 5.4

In women, ovaries and adrenal glands produce small amounts of androgens (male sex hormones), but tumors on these organs can cause abnormally large amounts of androgens

Can result in excessive hairiness, called hirsutism, as well as other signs of masculinization

Treatment is surgical removal of tumors

Hair Thinning and Baldness

Alopecia: hair thinning in both sexes after age 40

True (frank) baldness

Genetically determined and sex-influenced condition

Male pattern baldness caused by follicular response to DHT (dihydrotestosterone)

Clinical û Homeostatic Imbalance 5.5

Hair thinning can be induced by several factors:

Acutely high fever

Surgery

Severe emotional trauma

Certain drugs (such as antidepressants, blood thinners, steroids, and chemotherapeutic drugs)

Protein-deficient diets

Alopecia areata: immune system attacks follicles

Some hair loss is reversible, but others (such as from burns or radiation) are permanent

5.6 Nails

Scale-like modifications of epidermis that contain hard keratin

Act as a protective cover for distal, dorsal surface of fingers and toes

Consist of free edge, nail plate, and root

Nail bed is epidermis underneath keratinized nail plate

Nail matrix: thickened portion of bed responsible for nail growth

5.6 Nails

Nail folds: skin folds that overlap border of nail

Eponychium: nail fold that projects onto surface of nail body

Also called cuticle

Hyponychium: area under free edge of plate that accumulates dirt

Nails normally appear pink because of underlying capillaries

Lunule: thickened nail matrix, appears white

Abnormal color or shape can be an indicator of disease

Figure 5.7 Skin appendages: Structure of a nail.

Lunule

Lateral

nail fold

Free edge

of nail

Body

of nail

Eponychium

(cuticle)

Proximal

nail fold

Nail

matrix

Hyponychium

Nail bed

Phalanx (bone of fingertip)

Root of nail

5.7 Sweat Glands

Also called sudoriferous glands

All skin surfaces except nipples and parts of external genitalia contain sweat glands

About 3 million per person

Two main types

Eccrine (merocrine) sweat glands

Apocrine sweat glands

Contain myoepithelial cells

Contract upon nervous system stimulation to force sweat into ducts

Eccrine (Merocrine) Sweat Glands

Most numerous type

Abundant on palms, soles, and forehead

Ducts connect to pores

Function in thermoregulation

Regulated by sympathetic nervous system

Their secretion is sweat

99% water, salts, vitamin C, antibodies, dermcidin (microbe-killing peptide), metabolic wastes

Figure 5.8b Skin appendages: Cutaneous glands.

Sebaceous

gland

Sweat

pore

Eccrine

gland

Duct

Dermal connective

tissue

Secretory cells

Photomicrograph of

a sectioned eccrine

gland (140×)

Apocrine 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

Larger than eccrine sweat glands with ducts emptying into hair follicles

Begin functioning at puberty

Function unknown but may act as sexual scent gland

Apocrine Sweat Glands (cont.)

Modified apocrine glands

Ceruminous glands: lining of external ear canal; secrete cerumen (earwax)

Mammary glands: secrete milk

Sebaceous (Oil) Glands

Widely distributed, except for thick skin of palms and soles

Most develop from hair follicles and secrete into hair follicles

Relatively inactive until puberty

Stimulated by hormones, especially androgens

Secrete sebum

Oily holocrine secretion

Bactericidal (bacteria-killing) properties

Softens hair and skin

Figure 5.8a Skin appendages: Cutaneous glands.

Dermal

connective

tissue

Sebaceous

gland

Sebaceous

gland duct

Hair in

hair follicle

Sweat

pore

Eccrine

gland

Secretory cells

Photomicrograph of a

sectioned sebaceous

gland (90×)

Clinical – Homeostatic Imbalance 5.6

Whiteheads are blocked sebaceous glands

If secretion oxidizes, whitehead becomes a blackhead

Acne is usually an infectious inflammation of the sebaceous glands, resulting in pimples (pustules)

Overactive sebaceous glands in infants can lead to seborrhea, known as “cradle cap”

Begins as pink, raised lesions on scalp that turn yellow/brown and flake off

Figure 5.9 Cradle cap (seborrhea) in a newborn.

5.8 Functions of Skin

Skin is first and foremost a barrier

Its main functions include:

Protection

Body temperature regulation

Cutaneous sensations

Metabolic functions

Blood reservoir

Excretion of wastes

Protection

Skin is exposed to microorganisms, abrasions, temperature extremes, and harmful chemicals

Constitutes three barriers:

Chemical barrier

Physical barrier

Biological barrier

Protection (cont.)

Chemical barrier

Skin secretes many chemicals, such as:

Sweat, which contains antimicrobial proteins

Sebum and defensins, which kill bacteria

Cells also secrete antimicrobial defensin

Acid mantle: low pH of skin retards bacterial multiplication

Melanin provides a chemical barrier against UV radiation damage

Protection (cont.)

Physical barrier

Flat, dead, keratinized cells of stratum corneum, surrounded by glycolipids, block most water and water-soluble substances

Some chemicals have limited penetration of skin

Lipid-soluble substances

Plant oleoresins (e.g., poison ivy)

Organic solvents (acetone, paint thinner)

Salts of heavy metals (lead, mercury)

Some drugs (nitroglycerin)

Drug agents (enhancers that help carry other drugs across skin)

Protection (cont.)

Biological barriers

Epidermis contains phagocytic cells

Dendritic cells of epidermis engulf foreign antigens (invaders) and present to white blood cells, activating the immune response

Dermis contains macrophages

Macrophages also activate immune system by presenting foreign antigens to white blood cells

DNA can absorb harmful UV radiation, converting it to harmless heat

Body Temperature Regulation

Under normal, resting body temperature, sweat glands produce about 500 ml/day of unnoticeable sweat

Called insensible perspiration

If body temperature rises, dilation of dermal vessels can increase sweat gland activity to produce 12 L (3 gallons) of noticeable sweat

Called sensible perspiration; designed to cool body

Cold external environment

Dermal blood vessels constrict

Skin temperature drops to slow passive heat loss

Cutaneous Sensations

Cutaneous sensory receptors are part of the nervous system

Exteroreceptors respond to stimuli outside body, such as temperature and touch

Free nerve endings sense painful stimuli

Figure 5.1 Skin structure.

Hair shaft

Dermal papillae

Epidermis

Papillary

layer

Subpapillary

plexus

Sweat pore

Appendages of skin

• Eccrine sweat gland

• Arrector pili muscle

• Sebaceous (oil) gland

• Hair follicle

• Hair root

Dermis

Reticular

layer

Hypodermis

(subcutaneous

tissue; not part

of skin)

Cutaneous plexus

Nervous structures

• Sensory nerve fiber

with free nerve endings

• Lamellar corpuscle

• Hair follicle receptor

(root hair plexus)

Adipose tissue

Metabolic Functions

Skin can synthesize vitamin D needed for calcium absorption in intestine

Chemicals from keratinocytes can disarm some carcinogens

Keratinocytes can activate some hormones

Example: convert cortisone into hydrocortisone

Skin makes collagenase, which aids in natural turnover of collagen to prevent wrinkles

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

Excretion

Skin can secrete limited amounts of nitrogenous wastes, such as ammonia, urea, and uric acid

Sweating can cause salt and water loss

5.9 Skin Cancer and Burns

Skin can develop over 1000 different conditions and ailments

Many internal diseases reveal themselves on skin

Most common disorders are infections

Less common, but more damaging, are:

Skin cancer

Burns

Skin Cancer

Most skin tumors are benign (not cancerous) and do not spread (metastasize)

Risk factors

Overexposure to UV radiation

Frequent irritation of skin

Some skin lotions contain enzymes that can repair damaged DNA

Three major types of skin cancer

Basal cell carcinoma

Squamous cell carcinoma

Melanoma

Skin Cancer (cont.)

Basal cell carcinoma

Least malignant and most common

Stratum basale cells proliferate and slowly invade dermis and hypodermis

Cured by surgical excision in 99% of cases

Figure 5.10a Photographs of skin cancers.

Basal cell carcinoma

Skin Cancer (cont.)

Squamous cell carcinoma

Second most common type; can metastasize

Involves keratinocytes of stratum spinosum

Usually is a scaly reddened papule on scalp, ears, lower lip, or hands

Good prognosis if treated by radiation therapy or removed surgically

Figure 5.10b Photographs of skin cancers.

Squamous cell

carcinoma

Skin Cancer (cont.)

Melanoma

Cancer of melanocytes; is most dangerous type because it is highly metastatic and resistant to chemotherapy

Treated by wide surgical excision accompanied by immunotherapy

Key to survival is early detection: ABCD rule

A: asymmetry; the two sides of the pigmented area do not match

B: border irregularity; exhibits indentations

C: color; contains several colors (black, brown, tan, sometimes red or blue)

D: diameter; larger than 6 mm (size of pencil eraser)

Figure 5.10c Photographs of skin cancers.

Melanoma

Burns

Tissue damage caused by heat, electricity, radiation, or certain chemicals

Damage caused by denaturation of proteins, which destroys cells

Immediate threat is dehydration and electrolyte imbalance

Leads to renal shutdown and circulatory shock

To evaluate burns, the Rule of Nines is used

Body is broken into 11 sections, with each section representing 9% of body surface (except genitals, which account for 1%)

Used to estimate volume of fluid loss

Figure 5.11 Estimating the extent and severity of burns using the rule of nines.

Totals

41⁄2%

Anterior and posterior

head and neck, 9%

Anterior and posterior

upper limbs, 18%

41⁄2%

trunk, 18%

Anterior and posterior

trunk, 36%

Perineum, 1%

Anterior and posterior

lower limbs, 36%

100%

Burns (cont.)

Burns can be classified by severity

First-degree

Epidermal damage only

Localized redness, edema (swelling), and pain

Second-degree

Epidermal and upper dermal damage

Blisters appear

First- and second-degree burns are referred to as partial-thickness burns because only the epidermis and upper dermis are involved

Burns (cont.)

Burns can be classified by severity (cont.)

Third-degree

Entire thickness of skin involved (referred to as full-thickness burns)

Skin color turns gray-white, cherry red, or blackened

No edema is seen and area is not painful because nerve endings are destroyed

Skin grafting usually necessary

Figure 5.12 Partial-thickness and full-thickness burns.

1st-degree

burn

3rd-degree

burn

2nd-degree

burn

Skin bearing partial-thickness

burn (1st- and 2nd-degree burns)

Skin bearing full-thickness

burn (3rd-degree burn)

Burns (cont.)

Burns are considered critical if:

>25% of body has second-degree burns

>10% of body has third-degree burns

Face, hands, or feet bear third-degree burns

Treatment includes:

Debridement (removal) of burned skin

Antibiotics

Temporary covering

Skin grafts

Developmental Aspects of the Integumentary System

Fetal: by end of 4th month, skin of fetus is developed

Lanugo coat: delicate hairs in 5th and 6th month

Vernix caseosa: sebaceous gland secretion that protects skin of fetus while in watery amniotic fluid

Developmental Aspects of the Integumentary System

Infancy to adulthood: skin thickens and accumulates more subcutaneous fat; sweat and sebaceous gland activity increases, leading to acne

Optimal appearance during 20s and 30s

After age 30, effects of cumulative environmental assaults start to show

Scaling and dermatitis become more common

Developmental Aspects of the Integumentary System

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

Ways to delay aging:

UV protection, good nutrition, lots of fluids, good hygiene