Skin and body membranes Anatomy and Physiology

Bellringer Think about the skin on your body, is all the skin identical? If no, how is it different?

Intro to skin

What is integumentary system What is integumentary system? Integument means “covering” It is the cover of our body and includes 1-the skin that has several important functions. 2- The nails that protects the sensors in our fingers 3- The hair that protects us from UV light and keeps us warm

The skin Fun Facts: Avg. makes up about 9-11 lbs. or 7% of your weight Regenerates every 25-45 days Every minute you lose 30,000-40,000 dead skin cells

Skin Structure (EDH) Epidermis (epithelial) : Top or outermost layer made of squamous epithelium that continuous regenerates itself from the inside out. Made from the embryonic ectoderm layer. Site where pigments or melanin is made. Dermis (fibrous): Middle layer made of connective tissue. Hypodermis (subcutaneous layer – fat): The innermost layer

Skin Structure: Epidermis Epidermis—outer layer Stratified squamous epithelium

5 Layers “stratum” of the Epidermis (CLGSB) Stratum corneum: top, dead cells shed by desquamation Stratum lucidum: present in 4 layers skin: palms of the hand and soles of feet. Stratum granulosum: Sulfur rich protein “keratin” found in keratinocytes Stratum spinosum: “Prickly layer” (desmosomes for binding) and Landerhans cells for immunity and healing Stratum basale (innermost): create new cells through mitosis * TO REMEMBER USE: “Come, Lets Get Sun Burn” Stratum basale: The cells start out cuboidal or columnar, but they become flattened as they migrate to the skin surface. Migration takes 60-75 days. Keratin: tough protein for strength

Thick skin- covers palms, fingertips, soles of feet NOTE: Thick skin- covers palms, fingertips, soles of feet Thin skin – covers rest of body Very thin skin is missing stratum lucidum and sometimes stratum granulosum

GENETICS is the key factor Quantity of melanin (yellow to reddish- brown to black) protects skin from UV radiation Melanocytes use enzyme tyrosinase to convert tyrosine into dark brown melanin pigment. albinos lack DNA code to make tyrosinase Pigment produced by melanocytes and deposited into the epidermis cells Amount of melanin produced depends upon genetics and exposure to sunlight

Bellringer A child asks you why his lips “turn blue” when it is cold outside. What would you explain to this child? The color change is the result of diminished blood flow to the periphery of the body. The skin in more exposed areas is especially susceptible to blood vessel constriction in the body's attempt to retain body heat. The color change is the result of diminished blood flow to the periphery of the body. The skin in more exposed areas is especially susceptible to blood vessel constriction in the body's attempt to retain body heat.

Albinism in Humans

Melanin – Skin Color Sunlight increases melanin production by the release of hormones freckles or moles are accumulations of melanin other pigments such as carotene or hemoglobin contribute to skin color Prolonged exposure causes substantial melanin buildup which helps protect the DNA of viable skin cells from UV radiation by absorbing the light and dissipating the energy as heat

Skin Structure Dermis Dense connective tissue “true skin” layer Anchors skin to underlying organs Contains areolar connective tissue: binds blood vessels, membranes, muscles, nerves, and skin to other structures. Attached to the stratum germinativum by hemisdesmosomes along the dermal papilla

Dermis Papillary layer (upper dermal region) Dermal papillae: Fingerlike extensions of the underlying dermis bind tightly to the epidermal cells above by a thin layer of fibrous connective tissue known as the basement membrane Reticular layer (deepest skin layer)

Dermis Overview Collagen fibers give skin its toughness Elastic fibers give skin elasticity Blood vessels play a role in body temperature regulation

Subcutaneous “hypodermis” Layer Third and innermost layer of the skin Thickness of this layer varies throughout the body and from person to person Absent in thin skin Anchors to fascia: fibrous tissue that covers muscles, skull bones, and some organs Contains: adipose tissue “fat cells” blood vessels that branch out in capillaries into the dermis Lymphatic system Immune system nerves Fasciitis caused by microbes or injuries

Quiz Study skin structure notes, vocabulary from textbook for skin structure, and concept check questions. Labeling: epidermis, dermis, papillary layer of dermis, reticular layer of dermis, hypodermis, hair shaft, pore, layers of the epidermis

Quiz Please clear your desk of all except for a pen or pencil.

Word bank Pore Hemidesmosome Dermal papilla Stratum lucidum Fasciitis Stratum granulosum Stratum corneum Stratum basale Stratum spinosum Epidermis Desquamation Melanin Areolar connective tissue Integumentary system Reticular layer Pore Hemidesmosome Dermal papilla Stratum lucidum Fasciitis Papillary layer Hypodermis Dermis Hair shaft

Skin Appendages Glands Hair Hair follicles Nails Assist the skin with its functions

Three most common in skin: glands Three most common in skin: Ceruminous glands: Waxy (cerumen), ear canal sebaceous glands: Produce oil Glands are activated at puberty sweat glands:

Sebaceous glands

Sweat glands Produce sweat Widely distributed in skin Two types Eccrine: secrete mostly water and salts, organic compounds, and wastes on the skin of armpits, forehead, palms, and soles chemicals in food odors Microbes feed off nutrients Apocrine: secrete sweat(odorous material) into hair follicles of armpits, navel, groin region, and areolae Also broken down by bacteria (odor) pheromones: “Play a role in courtship and social behavior”

Bellringer What is responsible for the thinness or thickness of your skin? Explain. Missing layers: stratum lucidum and sometimes stratum granulosum and varying subcutaneous layer.

Sweat glands

Bellringer A sales representative for a shampoo company tells you their product “feeds” your hair cells protein. What arguments could you use to debate the validity of their claim? Students should be able to “tell” the sales representative that the shampoo is useless because it cannot feed the dead hair shaft cells. Any protein in the shampoo would merely stick to the hair surface.

Modified stratum corneum> inward protrusion of epidermis Hair Modified stratum corneum> inward protrusion of epidermis Produced by hair follicle Hair papilla: structure associated with small blood vessels at the base of the follicle Hair shaft: dead hardened cells that protrude the skin Hair cortex: dead, densely packed, keratinized cells similar to stratum corneum Consists of hard keratinized epithelial cells Melanocytes provide pigment for hair color

Hair Hair follicle- shaft, follicle (root) Growth- 4 in./year or 2 mm/week

Associated hair structures Hair follicle Arrector pili muscle Sebaceous gland Sweat gland

Scale-like modifications of the epidermis Made from keratin secretion Nails Scale-like modifications of the epidermis Made from keratin secretion Grows forward from nail root beneath the skin-nail fold. Keratocytes at the base move up.

Nails Consists of: Growth- 0.5 mm/week free edge Body Root Cuticle Lunula Growth- 0.5 mm/week

Nails

Nails Did you know that your fingernails grow much faster than your toe nails? 3-4 times faster!

Please draw and label the figure 4. 7 (a) pg. 145 and Figure 4. 8 pg Please draw and label the figure 4.7 (a) pg. 145 and Figure 4.8 pg. 146 on blank side(no lines) of index card

Skin Infections and Allergies Contact dermatitis Exposures cause allergic reaction Cold sores Caused by virus Impetigo Caused by bacterial infection Psoriasis Cause is unknown Triggered by trauma, infection, stress

Skin Infections and Allergies

Burns Burns Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals

Burns Associated dangers

Rule of Nines Way to determine the extent of burns Body is divided into 11 areas for quick estimation Each area represents about 9% of total body surface area

Critical Burns Burns are considered critical if Over 25% of body has second-degree burns Over 10% of the body has third-degree burns There are third-degree burns of the face, hands, or feet

Rule of Nines

First-degree burns Third-degree burns Severity of Burns Second-degree burns Third-degree burns