Integumentary system (Pert)

functions of skin

• Protection

• Vitamin D synthesis

• Sensation

• Thermoregulation

• Nonverbal communication

thick skin

on palms and sole, and corresponding surfaces on fingers and toes

• Has sweat glands, but no hair follicles or sebaceous (oil) glands

• Epidermis ~0.5 mm thick

thin skin

Possesses hair follicles, sebaceous glands, and sweat glands

Epidermis

made up of epithelial cells and is formed of several layers of cells.

Stratum basale

bottom layer or innermost layer of the epidermis

undergoes constant division of cells

contains melanocytes

helps protect from damage by excessive UV radiation.

As cells are dividing, old cells are pushed to the top to make the outermost layer

melanocytes

produce the protective skin-darkening pigment melanin.

helps protect from damage by excessive UV radiation.

Stratum corneum

outermost layer of the epidermis

These cells die and become flattened and hard

Cells produce keratin

These cells are constantly being rubbed off as we touch objects throughout the day.

keratin

waterproof protein helping to keep us from soaking up excess water.

Cells of Epidermis

Stem cells

Keratinocytes

Dendritic (Langerhans) cells

Melanocytes

Tactile (Merkel) cells

Stem cells

• Undifferentiated cells that give rise to keratinocytes

• In deepest layer of epidermis (stratum basale)

Keratinocytes

• Great majority of epidermal cells

• Synthesize keratin

Dendritic (Langerhans) cells

• Macrophages originating in bone marrow

• Found in stratum spinosum and granulosum

Melanocytes

• Only in stratum basale

• Synthesize melanin

• Branched processes

Tactile (Merkel) cells

• In basal layer of epidermis

• Touch receptor cells associated with dermal nerve fibers

Epidermis layers from deep to superficial

Stratum basale or germinativum

Stratum spinosum

Stratum granulosum

Stratum lucidum (only on thick skin)

Stratum corneum

Stratum basale or germinativum

A single layer of cuboidal to low columnar stem cells and keratinocytes resting on the basement membrane

Stratum spinosum

Numerous desmosomes and cell shrinkage produces spiny appearance; Consists of several layers of keratinocytes that produce pre-keratin filaments which causes cell to flatten

Stratum granulosum

3-5 layers of flattened keratinocytes producing keratin; Contains coarse dark-staining keratohyalin granules and lamellar granules

Stratum lucidum (only on thick skin)

Thin translucent zone; Keratinocytes are densely packed with eleidin, no nucleus or other organelles

Stratum corneum

horny layer (up to 30 layers of dead, scaly, keratinized cells)

Dermis

• connective tissue layer beneath the epidermis.

  • Ranges from 0.2 mm (eyelids) to 4 mm (palms, soles)

  • Composed mainly of collagen with elastic fibers, reticular fibers, and fibroblasts

  • Lots of blood vessels, sweat glands, sebaceous glands, and nerve endings

Smooth muscle (piloerector muscles)

associated with hair follicles

• Contract—goose bumps

Dermal papillae

upward fingerlike extensions of the dermis

• Friction ridges on fingertips that leave fingerprints

Papillary layer

superficial zone of dermis

• Thin zone of areolar tissue in and near the dermal papilla

• Allows mobility of white blood cells

• Rich in small blood vessels

Reticular layer

deeper and much thicker layer of dermis

• Dense irregular connective tissue

• Stretch marks (striae): tears in the collagen fibers caused by stretching of the skin

• Tension lines/Lines of cleavage

Hypodermis

Deep to the dermis is a layer of loose connective tissues. flexible connection between the skin and the underlying muscles and bones as well as a fat storage area.

Underlying muscles in hypodermis under adipose

• Subcutaneous tissue

• More areolar and adipose than dermis

  • Energy reservoir

  • Thermal insulation

  • Padding

  • Thicker in women

• Binds skin to underlying tissues

• Drugs introduced by injection

  • Highly vascular and absorbs them quickly

Friction ridges

fingerprints

Flexion lines (flexion creases)

lines on the flexor surfaces of the digits, palms, wrists, elbows

Freckles and moles

tan to black aggregations of melanocytes

Hemangiomas (birthmarks)

patches of discolored skin caused by benign tumors of dermal blood capillaries

Accessory skin organs

hair, nails, sweat glands, and sebaceous glands (derived from dermis layer)

Pilus

hair

3 zones of hair

Bulb

Root

Shaft

Bulb

swelling at the base where hair originates in dermis

root

he remainder of the hair in the follicle

shaft

the portion above the skin surface

medulla

Core of loosely arranged cells and air spaces

cortex

Constitutes bulk of the hair

Consists of several layers of elongated keratinized cells

cuticle

• Thin, scaly cells that overlap each other

• Free edges directed upward

Functions of hair

Warmth

sensation

protects from sunburn

guard hairs

eyelashes and eyebrows

lanugo

fine, downy, unpigmented hair that appears on the fetus in the last 3 months of development

Vellus

fine, pale hair that replaces lanugo by time of birth

• Two-thirds of the hair of women

• One-tenth of the hair of men

• All of hair of children except eyebrows, eyelashes, and hair of the scalp

Terminal

• longer, coarser, and usually more heavily pigmented

  • Forms eyebrows, eyelashes, and the hair of the scalp

  • After puberty, forms the axillary and pubic hair

  • Male facial hair and some of the hair on the trunk and limbs

Hair cycle stages

Anagen

Catagen

Telogen

Anagen

growth stage, 90% of scalp follicles at any given time

Catagen

degenerative stage, mitosis in the hair matrix ceases and sheath cells below the bulge die

Telogen

resting stage

alopecia

thinning of the hair or baldness

Hirsutism

excessive or undesirable hairiness in areas that are not usually hairy

Male Pattern baldness

the condition in which hair loss occurs from specific regions of the scalp

• Combination of genetic and hormonal influence

• Baldness allele is dominant in males , expressed only in high testosterone levels

• Testosterone causes terminal hair in scalp to be replaced by vellus hair

nails

help humans function

guard against injuries

enhance sensation

Fingernails and toenails

stratum corneum cells packed with hard keratin

Nail plate

hard part of the nail

free edge

overhangs the fingertip

nail body

visible attached part of nail

nail root

extends proximally under overlying skin

exocrine glands

regulate body temperature by producing sweat, feeding babies milk, cleaning, moistening and lubricating the eye to produce tears, helps start digestion and lubricate the mouth producing saliva.

Sudoriferous glands

are exocrine glands found in the dermis of the skin and commonly known as sweat glands.

Two kinds of sweat (sudoriferous) glands

Merocrine

apocrine

Merocrine

eccrine) sweat glands

• Most numerous skin glands

• Simple tubular glands

• Watery perspiration that helps thermoregulation

• Myoepithelial cells

apocrine

sweat glands

• Occur in groin, anal region, axilla, areola, bearded area in mature males

• Ducts lead to nearby hair follicles

• Produce sweat that is thicker, milky, and contains fatty acids

• Develop at puberty

• Pheromones

Sebaceous glands

are exocrine glands found in the dermis of the skin that produce an oily secretion known as sebum.

Holocrine glands

• Will release whole broken cells broken in your ductal system.

• These cells contain the reserves of substance that the gland will release.

• This secretion method requires frequent cell rotation and replacement.

Ceruminous glands

are special exocrine glands found only in the dermis of the ear canals.Their secretion combines with sebum and dead epithelial cells to form earwax (cerumen).Simple, coiled tubular glands with ducts that lead to skin surface

Mammary gland

is a gland located in the breasts of females that is responsible for lactation, or the production of milk.

mammary glands

milk-producing glands that develop only during pregnancy and lactation

• Modified apocrine sweat gland

• Richer secretion released by ducts opening into the nipple

regeneration

• Replacement of damaged or dead cells with same cell type

• Restores organ function

Fibrosis

• Gap filled with scar tissue

• Collagen produced by fibroblasts

• Functional activities not restored

Repair of integument/wound healing

1. Damaged blood vessel leaks blood and fill wound with blood

2. Blood clot forms. Leukocytes (neutrophils and macrophages) invade and begin to clean up the wound

3. Blood vessels begin to regrow and granulation tissue begins to form. Granulation produced by fibroblasts due to cell division and production of collagen and fibers. Granulation is more cellular than surrounding connective tissue and contains many blood vessels.

4. Epithelium heals and fibrosis occurs. Epithelium heals from stratum basale up, eventually pushing up and exfoliating the scab. Fibrosis occurs in the connective tissue as fibroblasts continue to produce fibers and a scar forms.

First-degree (superficial) burns

First-degree burns affect only the outer layer of skin, the epidermis. The burn site is red, painful, dry, and with no blisters. Mild sunburn is an example. Long-term tissue damage is rare and often consists of an increase or decrease in the skin color.

Second-degree (partial thickness) burns

Second-degree burns involve the epidermis and part of the lower layer of skin, the dermis. The burn site looks red, blistered, and may be swollen and painful.

Third-degree (full thickness) burns

Third-degree burns destroy the epidermis and dermis. They may go into the innermost layer of skin, the subcutaneous tissue. The burn site may look white or blackened and charred.

Fourth-degree burns

Fourth-degree burns go through both layers of the skin and underlying tissue as well as deeper tissue, possibly involving muscle and bone. There is no feeling in the area since the nerve endings are destroyed.

Skin Cancer

Cancer occurs when normal cells undergo a transformation and grow and multiply without normal controls. You only need a single cell in a tissue to be genetically damaged to produce cells with uncontrolled proliferation.

Detecting skin cancer

• A – asymmetry

• B – border is irregular

• C – color varies from one area to another

• D – diameter is larger than 6mm

• E – elevated

Skin cancer prevention

limiting sun exposure

avoid sun rays

Apple sunscreen

avoid artificial tanning booths

Fitzpatrick scale