Chapter 6: The Integumentary System

Merged flashcards from Chapter 6, McGraw Hill Anatomy and Physiology Ninth Edition, by Kenneth S. Saladin.

Skin cancer

Cancer caused by exposure to the UV rays of the sun, most often on the head, neck, and hands of fair-skinned people and the elderly; one of the most common and easily treated cancers

Types of skin cancer

• Basal cell carcinoma (stratum basale)

• Squamous cell carcinoma (stratum spinosum)

• Malignant melanoma (melanocytes)

Basal cell carcinoma

The most common type of skin cancer in the stratum basale; forms a small shiny bump with central depression and is the least dangerous because it seldom metastasizes

Squamous cell carcinoma

Arises from the keratinocytes of the stratum spinosum on the scalp, ears, lower lip, or back of hand and can form a concave ulcer; early detection and removal can allow recovery but if untreated can spread to lymph nodes and become lethal

Malignant melanoma

Skin cancer that arises from melanocytes and is less than 5% of all skin cancer; can be removed if caught early but is fatal when metastasized—greatest risk is genetics in men, redheads, and severe sunburn victims in childhood

Burns

The leading cause of accidental death from extreme tempreatures, radiation, electricity, or acids; fluid loss, infection, or toxic eschar cause most deaths

Eschar

The burned, dead tissue that forms over a burn

Debridement

The removal of eschar

Burn classification

Made to the depth of tissue involvement; first, second and third degree

First-degree burn

Burns that only involve the epidermis that can cause redness, slight edema, and pain but heal within days

Second-degree burn (partial-thickness burn)

Burns that can involve part of the dermis and may appear red, tan, or white with blisters and pain; these take several months to heal and may leave scars

Third-degree burn (full-thickness burn)

Burns that involve all of the dermis and deeper tissue; they require skin grafts and need fluid replacement, infection control, and nutrition to recover

UV Rays

Rays from the sun that have the potential to cause cancer; sunscreens may provide protection but may provide a false sense of security and damage DNA through their chemicals

Skin graft

Taking skin and putting it on a burn (usually of the third degree)

Autograft

Skin grafts taking tissues from another location on the same person’s body

Split-skin graft

Taking the epidermis and part of the dermis from an undamaged area and grafting it elsewhere; is an autograft

Isograft

Using tissue from an identical twin in a skin graft

Homograft (allograft)

Using tissue from an unrelated person in a skin graft

Heterograft (xenograft)

Using tissue from another species in a skin graft

Other graft options

Using the amnion from afterbirth and artificial skin from silicone and collagen

Types of sweat glands

Apocrine and eccrine

Apocrine glands

Type of sweat glands that are inactive until puberty and located in the axillary and groin region; the sweat produced is milky and contains fatty acids and pheromones

Bromhidrosis

The disagreeable body odor produced by bacterial action on sweat from apocrine glands

Eccrine glands

The most numerous skin glands; they are tubular and create a watery perspiration for thermoregulation

Myoepithelial cells

Cells found in both the apocrine and eccrine glands; they contact in response to stimulation by the sympathetic nervous system to squeeze perspiration out (as in stress sweating)

Sweat

A fluid made up of 99% water and a pH range of 4 to 6 to inhibit bacterial growth; begins as a protein free filtrate of blood plasma produced by deep secretory portion of gland

Sweat excretions

Sodium chloride (salt) and some drugs

Insensible prespiration

Prespiration that does not produce visible wetness of skin; humans sweat up to 500 ml per day this way

Diaphoresis

Sweating with the wetness of the skin; humans lose 1 L of sweat per hour during exercise this way

Cutaneous transporation

The water loss from skin not due to sweating; diffuses between keratinocytes and evaporates from the skin

Sebum

The oily secretion of sebaceous glands to aid moisturization

Sebaceous glands

Flask shaped glands that open into hair follicles that secrete sebum

Cerumen (earwax)

Yellow secretion combined with sebum and dead epithelial cells; it keeps the eardrum pliable, waterproof, and free from bacteria

Ceruminous glands

Coiled, simple tubular glands in the external ear canal; they are modified apocrine glands

Mammary glands

Glands that produce milk and develop only during pregnancy and lactation; they are heavily modified apocrine sweat glands

Mammary ridges (milk lines)

Two rows of mammary glands in mammals

Accessory organs of skin

The hair, nails, and cutaneous glands

Pliable soft keratin

Keratinized cells making up the stratum corneum of the skin

Compact hard keratin

Kertinized cells making up the hair and nails; tougher and more compact

Plius (pili)

A slender filament of keratinized cell growing from the skin called a hair follicle

Types of hair

Lanugo, vellus, and terminal

Lanugo hair

Fine hair that appears on the fetus in the last three months of development

Vellus hair

Fine and pale hair that replaces lanugo by the time of birth; two-thirds of hair in women, one-tenth hair in men, and all hair of children except eyebrows, eyelashes, and scalp hair

Terminal hair

Longer, coarser, and heavily pigmented hair; makes up eyebrows, eyelashes, scalp hair, and pubic, facial, and axillary hair after puberty

Hair bulb

The bottommost layer of the hair; swelling at the base where hair originates in the dermis

Hair root

Remainder of the hair in the follicle

Hair shaft

The portion of hair above the skin surface

Dermal papilla

Bud of vascular connective tissue encased by the bulb; the only source of nutrition for hair

Hair matrix

The region of mitosis above the papilla; hair’s growth center

Hair layers

Medulla, cortex, cuticle

Hair medulla

Core of hair, loosely arranged cells, and air spaces

Hair cortex

The center of the hair; contains elongated keratinized cells

Hair cuticle

The outer layer of the hair; multiple layers of thin and scaly cells that overlap

Hair follicle

Contains the hair root in a diagonal root; contains the epithelial root sheath as a source of stem cells and connective tissue root sheath which surrounds it

Hair receptors

Sensory nerve fibers around muscle; includes the arrector pili which attaches the follicle to the dermis

Hair texture

Related to the cross sectional shape of hair; straight is round, wavy is oval, curly is flat

Hair color

Determined by pigment granules in the cortex; brown has high eumelanin, while red has high pheomelanin (white has none)

Stages of hair

• Anagen—the growth stage where stem cells multiply and continue making hair cells

• Catagen—the degeneration stage where the hair keratinizes

• Telogen—the resting stage when papilla reaches the bulge

Hair growth

About 1 mm per 3 days

Alopecia

Thinning of the hair or baldness

Pattern baldness

Having hair lost from select regions; most common in males due to baldness allele being sex-linked

Hirsutism

Excessive hairiness in areas not usually hairy

Functions of hair

• Parasite detection with receptors

• Vestigial warmth

• Scalp hair to retain heat and protect against sunburn

• Pubic hair to signify sexual maturity

• Guard hairs to guard nostrils and ears

• Eyelashes for nonverbal communication

Fingernails and toenails

Clear and hard derivatives of stratum corneum to improve grooming and food picking

Nail plate

The hard part of the nail

Free edge

Overhangs the fingertip on nails

Nail body

The visible, attached part of the nail

Nail root

Extends proximally under skin

Nail fold

Surrounding skin rising above nail

Nail groove

Separates nail fold from nail plate

Nail bed

Skin underlying the nail plate

Nail matrix

The mitotic growth zone of thickened stratum basale at the end of the nail

Hyponychium

The epidermis of the nail bed

Lunule

Opaque white crescent at the proximal end of the nail due to matrix thickness

Eponychium (cuticle)

The narrow zone of dead skin overhanging proximal end of nail

Dermatology

The scientific study and medical treatment of the integumentary system

Integumentary system

Contains the skin, accesory organs, hair, nails, and cutaneous glands

Skin

The body’s largest and heaviest organ; covers 1.5 to 2.0 m² and is about 15% of body weight—made of the epidermis, dermis, and hypodermis

Epidermis

Outermost layer of keratinized stratified squamous epithelium on the skin; it is avascular with some nerve endings for touch

Dermis

The middle wavy layer of deeper connective tissue on the skin; made of the papillary and reticular layer and is 0.2 to 4 mm thick with hair follicles, blood vessels, glands, nerves, nails, roots, and muscles

Hypodermis

The bottommost layer of adipose tissue on the skin; contains more areolar and adipose tissue than the dermis and also contains blood vessels

Skin thickness

0.5 to 6 mm

Thick skin

Found on the palms of hands and soles of feet; only sweat glands and measures about 0.5 mm thick

Thin skin

Found on the rest of the body; contains hair follicles, sebaceous glands, and sweat glands and measures about 0.1 mm thick

Functions of skin

• Resistance to trauma and infection with keratin

• Barrier functions for water retention and UV defense

• Sensation of the outside world

• Thermoregulation and sensation for vasoconstriction/dilation, perspiration

• Facial expression

• Vitamin D synthesis

Epidermal cell types

Stem cells, keratinocytes, melanocytes, tactile cells, dendritic cells

Stem cells

Undifferentiated cells in the epidermis that give rise to keratinocytes in the stratum basale (deepest layer)

Keratinocytes

The great majority of epidermal cells, synthesizes keratin

Melanocytes

Cells in the epidermis that synthesize the pigment melanin to shield DNA; located in the stratum basale but distribute melanin along keratinocytes

Tactile cells

Touch receptors associated with dermal nerve fibers in the basal layer; also called Merkel’s cells and are star-shaped

Dendritic cells

Macrophages from the bone marrow guarding against pathogens in the stratum spinosum/granulosum; also called Langerhans’s cells

Strata

Layers of the epidermis

• Stratum corneum (top)

• Stratum lucidum (only in thick skin)

• Stratum granulosum

• Stratum spinosum

• Stratum basale (bottom)

Stratum basale

The deepest epidermal layer; only contains a single layer of stem cells, keratinocytes, and a few melanocytes and tactile cells

Stratum spinosum

Several layers of keratinocytes alongside some dendritic cells

Stratum granulosum

Three to five layers of flat keratinocytes

Stratum lucidum

Thin, pale layer only found in thick skin made up of keratinocytes with a clear protein

Stratum corneum

The surface layer of the skin, made up of several layers of keratinized stratified squamous epithelium to resist abrasion

Keratinocyte life

• Protein is released to bundle keratin

• Cells produce tough keratin protein under membranes

• Lipids are released to waterproof cells on the membrane (retain water)

• Organelles degenerate and die

Papillary layer

The thin zone of areolar tissue in and near the dermal papilla with blood vessels; uppermost layer of dermis

Reticular layer

The thick layer of dense irregular connective tissue that may have stretch marks due to stretched collagen; bottommost layer of dermis