Chapter 6: Integumentary System

6.1 Introduction

Why is skin considered to be an organ?

What makes up the integumentary system?

Integumentary System

Skin (cutaneous membrane)

Skin derivatives

Sweat glands

Oil glands

Hair

Nails

6.2 Skin and its Tissues

Skin is also know as a cutaneous membrane

How is the skin vital in maintaining homeostasis?

Skin has 2 layers Epidermis: most superficial; thin; stratified

squamous epithelial tissue; keratinized

Dermis: deep to epidermis; thicker; loose and dense connective tissue; contains appendages (hair, glands, blood vessels, nerves, etc)

Subcutaneous layer or hypodermis – lies deep to dermis; consists mostly of loose adipose connective tissue

Skin Structure

Figure 4.3

Epidermis – composed of keratinized stratified squamous epithelium. Structure: Principle Cell types and layers

Keratinocytes – makes up 90%, arranged in 4 to 5 layers, produce:

Keratin: tough, fibrous, waterproof protein

Lamellar granules: repel water

Melanocytes – 8%, produces pigment melanin, have long slender projections that transfer melanin to keratinocytes

Melanin: brown/black pigment, absorbs UV light

Langerhans cells – aid in immune response; easily damaged by UV light

Merkel cells – contact sensory neuron, aid in sensation

A Closer look at the Epidermis

Epidermal Cell layers (deepest to most superficial)

Stratum basale (deepest or base layer) – attached to basement membrane, contains most of the melanocytes, has cuboidal or columnar cells, mitosis.

Stratum spinosum (spiny layer) – 8-10 layers of irregular shaped keratinocytes, become flattened

Stratum granulosum (granular layer) – 3 - 5 layers of flat keratinocytes, undergoing cell death

Stratum lucidum (clear layer) – dead cells w/ lots of keratin; only in thick skin of finger tips, palms and feet

Stratum corneum (most superficial, horny layer) – 25 to 30 layers of flattened dead cells containing keratin, continuously shed and replaced by cells from deeper strata

What is Keratinization?

Melanin

Pigment (melanin) produced by melanocytes

Melanocytes are mostly in the stratum basale

Color is yellow to brown to black

Amount of melanin produced depends upon genetics and exposure to sunlight

Normal Skin Color Determinants

Melanin

Yellow, brown, or black pigments

Carotene

Orange-yellow pigment from some vegetables

Hemoglobin

Red coloring from blood cells in dermal capillaries

Oxygen content determines the extent of red coloring

Functions of epidermis

Protection (damage, UV rays, etc)

Growth / Repair (regeneration)

Immune response

Sensation

Water-repellent & sealant

Epidermal growth and repair

Regeneration time for skin is about 35 days

Shortened regeneration time results in increased thickness of stratum corneum making a callus (thick skin)

Dermis: deep to the epidermis

Structure of Dermis

Much thicker than epidermis has 2 portions:

Papillary Dermis (Superficial part of dermis): Loose areolar connective tissue

Dermal Papillae: finger-like projections indenting epidermis; increase surface area

Contain capillaries

Contain corpuscles of touch (Meissner corpuscles)

Reticular Dermis (Deep part of dermis): dense connective tissue

Contains hair follicles, nerves, blood vessels, sebaceous (oil) glands, & sudoriferous (sweat) glands

A Closer look at the Dermis

Functions of the Dermis

Sensitivity

Strength / support

Stretchable / elasticity

Flexibility

Dermal growth & repair

Dermis does not continually shed and regenerate like epidermis

If this layer is damaged, the fibroblasts form a dense mass of connective fibers forming a scar

Extreme stretching may produce small tears causing striae or stretch marks

Skin Structure

Subcutaneous tissue (hypodermis) is deep to dermis

Not part of the skin

Anchors skin to underlying organs

Composed mostly of adipose tissue

Sebaceous (oil) glands

Secretes oil (sebum), keeps hair & skin soft/pliable, prevents water loss from skin

Located in dermis, except for palms & soles

Aids in formation of pimples & black heads

2 types of Sudoriferous (sweat) glands

Eccrine glands –.

Apocrine glands –

Glands

Appendages of the Skin

Sebaceous glands

Produce oil

Lubricant for skin

Prevents brittle hair

Kills bacteria

Most have ducts that empty into hair follicles; others open directly onto skin surface

Glands are activated at puberty

Appendages of the Skin

Figure 4.6a

Appendages of the Skin

Sudoriferous (sweat) glands

Produce sweat

Widely distributed in skin

Two types

Eccrine

Open via duct to pore on skin surface

most common; secretes sweat, eliminates wastes, maintains core temp

Apocrine

Ducts empty into hair follicles

activated during puberty, located in armpit, groin, beard.

Appendages of the Skin

Figure 4.6b

Sweat and Its Function

Composition Mostly water

Salts and vitamin C

Some metabolic waste

Fatty acids and proteins (apocrine only)

Function Helps dissipate excess heat

Excretes waste products

Acidic nature inhibits bacteria growth

Odor is from associated bacteria

Appendages of the Skin

Ceruminous glands

Located in ear canal

Produces ear wax (cerumen)

Too much wax can cause a blockage of ear canal, loss of hearing

Appendages of the Skin

Hair follicles – composed of epithelial cells, distributed all over body except for palms, anterior side of fingers, soles, genitalia, and lips

Dermal and epidermal sheath surround hair root

Genetics and hormones determine thickness and distribution of hair

Hair is also important for protection and reproduction

Melanocytes provide pigment for hair color

Arrector pili muscle

Smooth muscle

Pulls hairs upright when cold or frightened (goose bumps)

Appendages of the Skin

Figure 4.7c

Appendages of the Skin

Hair anatomy

Central medulla

Cortex surrounds medulla

Cuticle on outside of cortex

Most heavily keratinized

Figure 4.7b

Appendages of the Skin

Figure 4.7a

Appendages of the Skin

Figure 4.8

Appendages of the Skin

Nails – Plates of tightly packed, hard, keratinized cells of epidermis

Very protective of ends of fingers; aids in grasping and manipulating small objects; scratching

Stratum basale extends beneath the nail bed

Responsible for growth

Lack of pigment makes them colorless

Appendages of the Skin

Nails can indicate health issues

Bluish nail beds may indicate circulation issue

White nail bed or oval depressions can indicate anemia

Pigmented spot (not injury) can indicate melanoma

Horizontal furrows may indicate period of illness or malnutrition

Disorders of heart, liver, or lungs may cause extreme curvature of nails

Red streaks in nails may be traced to RA, uclers, or hypertension

Nails: Figure 6.4

Free edge – extends past end of finger

Nail plate / body – visible part of nail

Nail root – sides and bottom of nail in groove, hidden by cuticle

Nail bed – skin surface that is covered by nail plate

Cuticle – skin around bottom of nail (stratum corneum)

Lunula – half-moon shaped white area at base of nail; the most active growing region

average growth is 0.5 to 1 mm per week

Appendages of the Skin

Figure 4.9

Skin Functions

Table 4.1 (1 of 2)

Skin Functions

Table 4.1 (2 of 2)

Overall Functions of the Integumentary System

Regulation of body temperatures

Sensitivity

Excretion and absorption

Vitamin D synthesis

Protection

Barrier to microorganisms

Barrier to chemical hazards

Reduces injury to underlying structures

Prevents dehydration

Protects (via melanin) excessive UV exposure

Surface film – protective barrier over skin’s surface; (like wax on your car)

6.4 Regulation of Body Temp.

How does your skin aid in regulating body temperature?

What portion of the brain controls the set point for body temperature?

Differentiate between hypothermia and hyperthermia. Discuss the consequences of each.

6.5 Healing of Wounds

What is inflammation? Is it normal or abnormal and why?

Differentiate between the healing processes of a superficial wound and a deeper wound. Which one would result in a scar?

Skin Homeostatic Imbalances

Infections

Athlete’s foot (tinea pedis)

Caused by fungal infection

Itchy, red, peeling condition of skin between the toes

Boils and carbuncles

Caused by bacterial infection

Common on dorsal neck, inflammation of hair follicles and sebaceous glands.

Cold sores

Caused by virus (herpes simplex) – activated by stress, fever, illness, and UV Radiation

Small fluid-filled blisters that itch and sting

Homeostatic Imbalances

Skin Homeostatic Imbalances

Infections and allergies

Contact dermatitis

Exposures cause allergic reaction

Itching, redness, and swelling of skin – progressing to blistering

Impetigo

Caused by bacterial infection

Pink, water-filled, raised lesions (nose and mouth) that develop a yellow crust and eventually rupture

Psoriasis

Cause is unknown

Triggered by trauma, infection, stress

Overproduction of skin cells, reddened epidermal lesions covered with dry, silvery scales that itch, burn, crack and sometimes bleed.

Skin Homeostatic Imbalances

Figure 4.10

Skin Homeostatic Imbalances

Burns

Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals

Associated dangers

Dehydration

Electrolyte imbalance

Circulatory shock

Rule of Nines

Way to determine the extent of burns

Body is divided into 11 areas for quick estimation

Each area represents about 9% of total body surface area

Rule of Nines

Figure 4.11a

Severity of Burns First-degree burns

Only epidermis is damaged

Skin is red and swollen

Second-degree burns

Epidermis and upper dermis are damaged (partial-thickness burn)

Skin is red with blisters

Third-degree burns

Destroys entire skin layer (full-thickness burn)

Burn is gray-white or black

Severity of Burns

Figure 4.11b

Critical Burns

Burns are considered critical if

Over 25% of body has second-degree burns

Over 10% of the body has third-degree burns

There are third-degree burns of the face, hands, or feet

Skin Cancer

Cancer—abnormal cell mass

Classified two ways

Benign

Does not spread (encapsulated)

Malignant

Metastasized (moves) to other parts of the body

Skin cancer is the most common type of cancer

Skin Cancer Types

Basal cell carcinoma

Least malignant – 99% cure in which lesion is removed surgically

Most common type – Sun Exposure

Arises from stratum basale – cells are altered so that they cannot form keratin

They invade dermis and subcutaneous tissue

Symptoms: shiny, dome-shaped nodule that later develop a central ulcer with a “pearly” beaded edge.

Skin Cancer Types

Figure 4.12a

Basal Cell Carcinoma

Skin Cancer Types

Squamous cell carcinoma

Metastasizes to lymph nodes if not removed

Early removal allows a good chance of cure

Believed to be sun-induced

Arises from stratum spinosum

Symptoms: lesion, scaly, reddened papule (small, rounded elevation), that gradually forms a shallow ulcer with a firm, raised border.

Grows rapidly and metastasizes to adjacent lymph nodes if not removed

If caught early and removed surgically or by radiation – the cure rate is good.

Squamos Cell Carcinoma

Skin Cancer Types

Figure 4.12b

Skin Cancer Types

Malignant melanoma

Most deadly of skin cancers

Cancer of melanocytes

Metastasizes rapidly to lymph and blood vessels

Detection uses ABCD rule

Cause: Genetics, accumulated damage to DNA in skin cells

Symptoms: arise as a spreading brown to black patch that metastasizes rapidly to surrounding lymph and blood vessels

Chance of survival is 50%

Accounts for 5% of skin cancers

Skin Cancer Types

Figure 4.12c

Malignant Melanoma

ABCD Rule A = Asymmetry

Two sides of pigmented mole do not match

B = Border irregularity

Borders of mole are not smooth

C = Color

Different colors in pigmented area

D = Diameter

Spot is larger then 6 mm in diameter

E = Elevation/Evolves

Spot is elevated or changes over time