A&P 1: Chapter 6

Body’s largest organ

Skin

Study of the skin

Dermatology

What is the integumentary system made up of?

Integument (skin) and accessory organ (hairs, nails, and cutaneous glands)

Skin is made up of 2 parts

Epidermis (epithelium) and dermis (Loose areolar CT & Dense irregular CT)

Hypodermis is made up of

areolar CT and adipose tissue

Skin is classified as thick or thin based on the thickness of the

epidermis

Where is thick skin found?

palms, soles, and corresponding surfaces on fingers and toes

Thick skin lacks 2 things but has _____

hair follicles and sebaceous gland; sweat glands

What does thin skin contain?

hair follicles, sweat, and sebaceous glands

Functions of the Integument

1. Contains the body
2. Resists trauma and infection
3. Serves as a barrier against water loss/gain, UV radiation, certain chemicals, and Vitamin D synthesis
4. Sensation
5. Thermoregulation
6. Non-verbal communication

5 cell types present in the Epidermis

1. stem cells
2. keratinocytes
3. melanocytes
4. tactile cells
5. dendritic cells

What is the deepest layer of the epidermis?

Stratum basale

What is the most superficial layer of the epidermis?

Stratum corneum

Layers of the epridermis

1. Stratum corneum
2. Stratum lacidum (only in thick skin)
3. Stratum granulosum
4. Stratum spinosum
5. Stratum basal

Stem cells define

undifferentiated cells that give rise to keratinocytes in the stratum basal

Keratinocytes define

major cell; responsible for making keratin

Melanocytes

make melanin; cells remain in the stratum basal

Melanosomes define

packages of melanin

Tactile cells

involved in sensation of touch; tactile discs include the cell and associated nerve fiber

Dendritic cells

immune cells that have migrated to the stratum spinosum or stratum granulosum

Life history of keratinocytes

1. Begins in stratum basal with differentiation from stem cells
2. Pushed towards the surface by further division of cells
3. enter stratum granulosum and flatten, increase keratin and lipid production
4. Cell surface becomes waterproof
5. cells seal themselves off and die
6. Result from granulosum is epidermal water barrier
7. Dead keratinocytes continue through the stratum corneum until they are shed as dander

What is the dermis made of?

Primarily collagen with some reticular and elastic fibers

2 regions of the dermis

Papillary layer (superficial; areolar CT); reticular layer (deep; dense irregular CT)

What does the papillary layer produce?

Friction ridges that lead to fingerprints

Where are stretch marks produced?

the reticular layer

3 pigments that contribute to skin color

melanin, carotene, and hemoglobin

Melanin

Only pigment made in skin

Carotene

1. From plant products
2. Accumulates in the stratum corneum and the fatty deposits of the hypodermis
3. Converts to Vitamin A

Hemoglobin

Pinkish color; more evident in Caucasian skin

2 forms of melanin

pheomelanin (reddish-yellow) and eumelanin (brownish-black)

Color difference is due to

amount and form of melanin

UV can damage a cell’s

structure

Cyanosis

Blue skin color; low oxygen in the hemoglobin

Erythema

redness of the skin; fever, hypertension, inflammation, and allergy

Pallor

Blanching; anemia, low blood pressure, fear, and anger

Jaundice

yellowing of the skin; liver disorder

Hematoma

bruises; clotted blood beneath skin

Albinism

genetic mutation disorder; melanocytes fail to produce melanin

Friction ridges

On fingertips and soles of feet; enhance sense of touch and grip

Flexion lines

dermal folds at or near joints; dermis tightly secured to deeper structures

Hemangiomas

birthmarks; benign tumors of the capillaries

2 types of hemangiomas

1. Capillary/cavernous hemangiomas
2. port-wine stain

Capillary/cavernous hemangiomas

present at or soon after birth, often disappear with age

Port-wine stain

flat, pinkish to dark purple in color; remains for life

Function of hair

1. Sensation
2. Retains heat
3. Protects scalp from UV radiation
4. Guard hairs protect the eyes, nasal cavity, and ears from debris
5. Eyebrows are important for facial expression and protecting the eyes

Lanugo meaning

no pigment

Lanugo

fine hairs on the fetus during last trimester

Vellus meaning

some pigment

Vellus

replaces lanugo hair; remains dominant on men and women

Terminal meaning

heavily pigmented

Terminal

makes up the hair on the scalp, eyebrows, and eyelashes; after puberty it makes up hair on the axilla, pubic region, male facial hair, and some hair on the trunk and limbs

2 regions of hair structure

shaft and root

Shaft

sticks out of the skin

Root

part of hair in follicle

3 layers of keratinized cells

cuticle, cortex, and medulla

Cuticle

Heavily keratinized; arranged like overlapping shingles

Cortex

hard keratin with injected melanin, flattened

Medulla

large cells and air spaces

Follicle

tube of epidermal tissue in the dermis

Hair bulge

contain stem cells for follicle growth and capillaries for blood supply

Hair receptors

nerve fibers detect hair movement

Piloerector muscles

Arrector pili or pilometer muscle; smooth muscles to raise hair

Hair matrix

Mitotically active cells- hair growth

Brown/black hair is

rich in eumelanin

Red hair is

rich in pheomelanin, some eumelanin

Blond hair is

little eumelanin and some pheomelanin

Gray hair is

little melanin; airsapace in the medulla

Alopecia

thinning of the hair

Hirsutism

undesirable hair growth; influences by abnormal testosterone levels and genetics

Nail is a

hardened derivative of the stratum corneum

Yellow nails indicate

Respiratory or thyroid gland disorders

Concavity of nail indicate

iron deficiency

horizontal lines in nails indicate

malnutrition

Free edge

extends beyond distal edge of fingertip

Nail body

visible attached portion

Nail root

proximal edge of nail embedded in skin

Nail bed

epidermal layers deep to nail body

nail matrix

thickened proximal portion of nail bed; makes nail grow

Sudoriferous glands are also known as

sweat glands

Sebaceous glands

oil glands; secrete sebum; important for normal skin and hair health

Ceruminous glands

only in external ear; secretions combine with sebum to make earwax

Mammary glands

secrete breast milk

Apocrine sweat glands

1. confined to axillary, areolar, and genital areas
2. Secretions contain fatty acids and proteins
3. secrete to hair follicle
4. Begin functioning during puberty
5. activated by nerve fibers during pain, stress, and sexual activity

Bacteria metabolize secretions creating

body odor

Merocrine sweat glands

1. secrete to skin surface
2. acidic secretion
3. Creates acid mantle
4. widely distributed over the body
5. responsible for cooling down the body through evaporative cooling

In sweat glands what pushes perspiration up the duct

myoepithelial cell

Diaphoresis

heat, exercise lead to noticeable perspiration

Acne

inflammation of sebaceous glands

Dermatitis

Any inflammation of the skin, usually with itching and redness

Eczema

Itchy, red skin lesions caused by an allergy; may progress to thickened, leathery, dark patches

Psoriasis

Recurring, reddened plaques covered with silvery scale; possibly an autoimmune disorder; hereditary

Rosacea

rash-like formation, often around nose and cheeks, marked by fine networks of blood vessels; worsened by hot drinks, alcohol, and spicy food

Seborrheic dermatitis

Patches of scaly white or yellowish inflammation often on head, face, chest, and back; called cradle cap

Tinea

any fungal infection of the skin; common in moist areas such as the axilla, groin, and foot

Cancer

uncontrolled division of cells

Mole characteristics

1. uniform color
2. even contour
3. relatively small

Cancer characteristics

1. various color
2. scalloped border
3. large in size
4. spreads

Most important risk factors

exposure to UV radiation; genetics

Basal cell carcinoma

least malignant; most common; cells of stratum basal grow and invade dermis and subcutaneous glands

Squamous cell carcinoma

cells of stratum spinosum; believed to be sun-induced