integumentary system our 1 st system!. integumentary system includes skin, sweat glands, sebaceous...

Integumentary System

OUR 1ST SYSTEM!

Integumentary system Includes skin, sweat glands, sebaceous (oil)

glands, hair, and nails SKIN (or cutaneous membrane or integument)

• Largest organ

• Makes up 16% of total body mass.

• 0.5 (eyelids) to 4 (heels) mm thick

• Mostly 1-2 mm

• About 2 square meters in adults

• Weighs about 10-11 lbs

Fun FactsDon’t write

THE LAYERS OF SKIN

Epidermis

Superficial layer Keratinized stratified squamous

epithelium Avascular Cells are continually replaced

•Old cells “keratinize”- harden THICK SKIN- 5 layers (palms, fingers, soles

of feet) THIN SKIN- 4 layers (rest of body)

Epidermis cont.

90% of cells are keratinocytes: • produce keratin – a protein - protects skin

from heat, microbes, and chemical.

• Produce lamellar granules

• release a lipid that decreases water entry and loss

8% melanocytes melanin

Epidermis Layers (from deep to superficial)

1. Stratum Basale (Base layer)- firmly attached to the dermis, cells rapidly divide

2. Stratum Spinosum – cells start to flatten and appear spiny, produce keratin

3. Stratum Granulosum- cells are flat and start to die

4. Stratum Lucidum present only in thick skin; clear, flat, dead cells

5. Stratum Corneum- durable overcoat of dead cells, thickest layer

Dermis Deep to epidermis Dense irregular connective tissue and elastic

fibers • gives skin toughness and elasticity

Rich nerve and blood supply Contains hair follicles, sebaceous glands (oil),

and sweat glands. Pain and touch receptors “stretch marks” (striae) caused by small tears

in the dermis

Subcutaneous layer – technically not a layer of skin

Hypodermis areolar and adipose tissue Insulation, protection, and contains

major blood vessels.

Check for understanding 4 - I can explain to my peers characteristics

of each of the major layers of the skin 3 - I understand characteristics of each of

the major layers of the skin 2 - I understand, but need to review my

notes. 1 - skin has layers???

Skin accessory structures

Hair

Function: protects the body•Scalp: also decreases heat loss

•Eyebrows/eyelashes/nostrils/external ear: protect eyes/nose/ears from foreign particles.

•Also function in sensing light touch.

Hair anatomy

Made of column of dead, keratinized cells bonded together by extracellular proteins

Shaft: above skin Root: deep into dermis Bulb:

•base; blood vessels nourish

Make-up of shaft and root

Medulla: can be lacking Cortex: Cuticle: made of single layer of thin , flat

cells that are keratinized; arranged like shingles

Arrector pili: muscle pulls the hair shafts perpendicular to the skin

Occurs when emotionally upset or cold

Hair growth

Visible hair is dead, but portion of its root are alive

Goes through a growth stage and resting stage (scalp hair: 2-6 years, 3 months)

Normal hair loss: 70-100 hairs a day Can by altered by chemotherapy,

radiation, age, genetics, gender, emotional stress, rapid weight loss, childbirth.

Nails

Tightly packed, hard, dead, keratinized epidermal cells

Consists of a nail body, free edge and a nail root

Most active growing region is the lunula, half moon shaped area at the base of the nail.

Nail slides forward over the nail bed.

Nail growth

Determined by rate of mitosis of cells deep to nail root.

Affected by age, health, nutrition Function: help grasp small objects,

protection for ends of digits, and allow us to scratch various parts of the body.

Sebaceous Glands (oil)

Epithelial tissue Gland lies in dermis and opens into hair follicle Not on palm and soles, varied sizes elsewhere Secrete sebum (fatty material, protein, and

salt). Coats hair prevents drying Prevents too much evaporation from skin,

keeps skin soft and pliable, inhibits growth of certain bacteria.

Oversecretion (due to hormones) causes acne due to bacteria

Sudoriferous Glands (sweat)

Epithelial tissue Each gland is a tiny tube that starts

as a coil shaped ball Two types:

•Eccrine – thermal regulation

•Apocrine – “cold sweat”: stimulated during emotional stress and sexual excitement

1. Eccrine Glands

•Most numerous

•Active from birth

•Common on forehead, back, neck

•Originates in dermis

•Empties into pores on surface of skin

•Secrete: water, ions, urea, uric acid, ammonia, amino acids, glucose, and lactic acid.

•Function: regulate body temperature through evaporation.

2. Apocrine Glands

•Found mainly in axillary and inguinal regions.

•Originates in hypodermis

•Empties through a duct into hair follicle

•Same components of eccrine sweat plus lipids and protein

•Stimulated during emotional stress and sexual excitement

•Begin functioning at puberty

•Commonly called “cold sweat”

SKIN COLOR

What influences our appearance?

Pigments:

1. melanin

Produced from melanocytes of epidermis

Varies by•Color: yellow-brown-black

•amount Freckles/moles Natural “shield”

2. hemoglobin

RBCs; carry O2 Hidden by melanin

3. carotene

Yellow-orange pigment From diet

Skin color as a diagnostic clue

Cyanotic (bluish): Jaundice (yellowish): Erythema (red): Pallor (paleness):

Functions of skin

1. Regulation of Body Temp.

HOT•Blood rushes to skin – heat released

•Sweat- evaporation cools COLD

•Blood moves to vital organs

•Goose bumps

2. protection

1. keratin protects underlying tissues from microbes, abrasion, heat, chemicals

2. Lipids: guards against dehydration 3. Sebum (oil): prevents skin and hairs from

drying and kills surface bacteria 4. Acidic pH of sweat inhibits growth of

bacteria 5. Melanin: shield against UV light.

3. Cutaneous sensations

Tactile: touch, pressure, vibration, Thermal Pain

4. Excretion and absorption

Excretion: sweat removes water and small amounts of salts, carbon dioxide, ammonia and urea

Absorption of some lipid-soluble materials: • Fat-soluble vitamins (ex. A, D, E,K)

• Lead, mercury

• Chemical in poison ivy

Medical application of this function:

transdermal drug administration (a patch):

examples: nicotine, hormones to prevent contraception

5. Synthesis of vitamin D

UV activates a molecule to turn into vitamin D (a hormone that aids in the absorption of calcium from intestines into the blood)

SKIN CANCER

Cause: sun Types:

• basal cell carcinoma

• 78% of all, from stratum basale, rarely metastasize

• Squamous cell carcinomas

• 20% of all, squamous cells of epidermis, some tendency to metastasize

• Malignant melanomas

• 2% of all, from melanocytes, metastasize and kill rapidly

• Early detection: ABCD

RISK FACTORS

1. Skin type2. Sun exposure3. Family history4. Age5. Immunological status Risk doubled in last 20 years: ozone

depletion and more time in sun/tanning beds

Wound healing

Repairs skin to normal (or near normal) structure and function

2 types

1. Epidermal wound healing

Center may penetrate dermis, edges involve only slight damage to superficial epidermal cells

Basal cells divide and migrate across wound until they encounter basal cells from the other side.

2. Deep wound healing

Injury to dermis and subcutaneous layer. Phases:

• Inflammatory phase: formation of blood clot in wound; vasodilation enhances delivery of helpful cells

• Migratory phase: scab, epithelial cells migrate beneath to bridge wound, scar tissue starts (collagen fibers), blood vessel regrowth

• Proliferative phase: much growth of scar tissue, blood vessels, and epithelial cells beneath scab

• Maturation phase: scab sloughs off

(scar tissue: more collagen fibers densely packed, less elasticity, fewer blood vessels, may not have same # of hairs, glands or sensory structures as undamaged skin)