Integumentary System

17. Integumentary System - covering of the body A. Includes - skin, hair, and nails

Skin 18. Body’s largest organ

B. Functions – most important is protection

Functions a. Holds fluids in

Functions b. Keeps disease causing microorganisms out

Functions c. Pigments protect from UV rays

Functions d. Makes vitamin D from sunlight and cholesterol

Functions e. Nerve endings in skin sense heat, cold, and pressure

Made of two main layers

19. Epidermis - outer layer, stratified squamous

A. Stratum Corneum - outer layer of dead cells, contain keratin

Keratin a. A tough fibrous protein, waterproofs forms basic structure of hair, nails, and cuticles soft keratin hard keratin

In animals, keratin also makes: cow horns, reptile scales, bird feathers, and porcupine quills

Replaced b. Once every 14-28 days

B. Stratum Germinativum – bottom layer of epidermis-mitosis happens

Melanocytes a. contain melanin pigment, protection from UV

Light and dark skin b. We all have roughly the same amount of melanocytes, the difference is in the amount of melanin produced

Freckles and moles Concentrated areas of melanin

Importance of melanin c. absorbs Ultraviolet Radiation from the sun

20. Dermis – thick, inner layer of the skin, contains living cells

Nerve endings A. Feel our environment

Blood vessels B. Bring nutrients to cells and help regulate body temperature

Hot – vessels widen and release heat through the skin Cold – vessels narrow to keep heat in the body

Glands C. Sacs that release contents at the surface of the skin

Sweat glands a. Produce and secrete sweat – water, salts, and cellular wastes

Purpose Helps cool the body as sweat evaporates

Smell? Sweat itself doesn’t smell, it is the bacteria that feed on the sweat

Sebaceous glands b. Produce an oil called sebum

Purpose lubricate the skin and hair, kills many bacteria

Acne – inflammation of the sebaceous glands

Whitehead – glands are blocked with sebum Blackhead – sebum dries and darkens Pimple – glands become infected with bacteria

Hair follicle D. Sac that surrounds the hair and it’s root

Arrector pili E. Smooth muscle cells that pull the hair upright when cold or scared

21. Hypodermis - Layer of fat and connective tissue below the dermis

Issues with skin

Blister A. Friction causes the epidermis to separate from the dermis, fluids fill the space

Callus B. Increased pressure causes the epidermis to thicken

Burns C. Tissue damage caused by heat, cold, chemicals, electricity, radiation

1st degree a. Only the epidermis is damaged, redness, swelling, pain

2nd degree b. Damage epidermis and upper part of dermis, blisters form

3rd degree c. Damage entire thickness of skin, appears gray-white, cherry red, or black, no pain

Melanoma D. Cancer of the melanocytes, most dangerous of skin cancers

Warning signs A – asymmetry B – border irregularity C – color D – diameter

As it evolves… Old moles can evolve into cancerous ones

23. Hair – made of dead, keratinized cells Hard keratin: More durable Cells don’t flake off

A. Functions – not really for warmth a. Sense insects on skin before they bite or sting b. Eyelashes shield the eyes c. Nose hairs filter particles before we inhale

Hair structure a. Shaft – projects from the skin b. Root - below the skin, living cells dividing c. Hair follicle – tube like pockets that extend into the dermis and house the hair roots

Shaft layers a. Medulla – central core of large cells and air spaces

Shaft layers b. Cortex – several layers of flattened cells surrounding the medulla

Shaft layers c. Cuticle – outermost layer of cells that overlap like shingles – provides strength and keeps inner layers tightly packed Subjected to the most abrasion, it tends to wear away at the ends of the shaft which allows the inner layers to separate causing split ends

Split ends

Follicle shape – determines hair texture a. Straight hair – round follicles b. Curly hair – flat follicles

Hair growth E. Most grow for several years and then fall out

24. Nails – solid plates of dead, keratinized epidermal cells

Functions a. Protect tips of fingers and toes b. “tool” for digging, scratching, picking up small things

Nail structure a. Nail plate – body of the nail, hard

Nail structure b. Nail bed – lies under the nail plate, gives nails their pink color

Nail structure c. Nail matrix – where nail cells are produced, if damaged, nail will not grow

Nail structure d. Cuticle – flap of skin that covers the nail root

Nail structure e. Lunula – white crescent shape at base of nail, visible part of the matrix Thicker cells of the matrix make it look white – damage to this will permanently deform the nail Even if the nail is removed the lunula will remain and look like a small nail imbedded in the finger

Nail growth C. Grow continuously without shedding, avg. 3 mm a month Fingernails require 3 to 6 months to regrow completely, and toenails require 12 to 18 months

2 feet, 11 inch thumb nail Lee Redmond, right, former record holder for longest fingernails with Melvin Booth, the male owner of the longest finger nails.