Checklist I took notes I labeled the layers of skin

Notebook Work What do you know about the layers of skin? How does skin function? Why do we need it? Is skin an organ?

Inte – = whole - gument = body covering Integumentary System Inte – = whole - gument = body covering

Skin Skin is an organ because it consists of different tissues that are joined to perform specific activities In adults, skin covers an area of about 2 square meters (22 square ft) Dermatology is the branch of medicine that specializes in diagnosing and treating skin disorders

Structure of Skin 3 parts – thin, outer portion called the epidermis and the deeper, thicker, connective tissue called the dermis Deep to the dermis is the subcutaneous layer also called the hypodermis Attaches skin to underlying structures

Epidermis Stratified squamous epithelium and contains 4 types of cells 1) 90% is keratinocytes which undergo keratinization Cells formed in basal layer move to surface, the cells die, slough off, and are replaced by new cells 2) 8% are melanocytes which produce melanin, the brown-black pigment that gives skin color and absorbs UV light. 5 layers and has NO blood vessels

Skin Color 3 pigments Emotions can also influence skin color! Cyanosis Melanin-yellow, reddish brown, or black Carotene-orange-yellow (carrots) Oxygen rich hemoglobin- pigment of red blood cells Emotions can also influence skin color! Cyanosis Jaundice

Epidermis 3) Langerhans cells-important in immune responses and easily damaged by UV light 4) Merkel cells – located in deepest part of epidermis, important in the sensation of touch

Dermis Made of connective tissue containing collagen and elastic fibers that give skin the extensibility and elasticity Stretch marks are called striae Thick on soles of feet and palms, thin on eyelids Dermal papillae cause ridges in epidermis=fingerprints

Hypodermis (subcutaneous) Subcutaneous layer (deepest) consists of adipose tissue and other connective tissue Serves as storage depot for fat and contains large blood vessels that supply the skin The subcutaneous layer and dermis contain sensory neurons (sensitive to pressure)

Functions of Skin (6) 1. Regulation of body temp.-evaporation of sweat lowers body temp, changes in the flow of blood in the skin also regulate body temp

Functions of Skin (6) 2. Protection- skin covers body and provides a physical barrier that protects underlying tissues from physical abrasions, bacterial invasion, dehydration, and UV radiation Check out the leather!!! 

Functions of Skin (6) 3. Sensation- contains abundant sensory nerve ending and sensory receptors that detect temp., touch, pressure, and pain

Functions of Skin (6) 4. Excretion- small amounts of water, salts, and several organic compounds are excreted by sweat glands

Functions of Skin (6) 5. Immunity- the cells in the epidermis are an important component of the immune system, which fends of foreign invaders of the body.

Functions of Skin (6) 6. Synthesis of vitamin D- exposure of skin to UV radiation initiates synthesis of the active form of vitamin D Aids in the absorption of calcium and phosphorus from the G.I. Tract into the blood

Accessory Structures of the Skin Hair is present on most skin surfaces except the palms of fingers soles and toes Hair on scalp protects from sun, eyebrows and lashes protect eyes from foreign objects, and nostril hair keeps insects and foreign objects out of nose Arrector pili muscle makes “goosebumps”

Accessory Structures of the Skin

Accessory Structures of the Skin Cutaneous glands Sebaceous glands (oil glands) Sweat glands (2.5 million per person)

Homeostasis of Body Temp. When it is hot, thermoreceptors (nerve endings in skin) detect and send impulses to the brain The temp control center of brain (hypothalamus) sends an impulse to sweat glands When the sweat evaporates, it takes the heat with it Other ways body heat is regulated: dilating or restricting blood vessels, metabolic rate change, skeletal muscle contractions

Damage to the Skin Cuts and scrapes- minor cuts, the epidermis divides to replace lost cells Major cuts, blood flows clot forms making a scab cells beneath scab divide to fill wound White blood cells kill invaders

Effects of Sunburns As people age, the elasticity of their skin decreases=wrinkles Exposure to UV rays can speed the process and cause burns

Effects of Sunburn First-degree=cells in epidermis, redness, swelling, pain Second-degree= cells deeper in the epidermis die, cells in the dermis injured and may die, blisters Third-degree=cells in epidermis and dermis die. Nerve cells and muscle cells injured, skin function lost, need transplant, no pain because of nerve damage Infection is a leading cause of death for burn victims

Skin Cancer UV radiation (natural or fake bake) Damage DNA in skin cells causing cells to grow and divide uncontrollably=skin cancer Most common cancer in the U.S. Melanoma-deadly-one person every hour Nonmelanoma WEAR SUNSCREEN! 1 in 5 Americans will develop skin cancer in their lives!

Did You Get It? 8. What are 3 important functions of the skin? 9. What cell type is most abundant in the epidermis? 10. What pigments determine skin color? 11. What are the criteria for classifying burns as 1st, 2nd, and 3rd degree? 12. What is the single most common risk factor for skin cancer?