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The Integumentary System. Chapter 4. Integumentary System Includes:. Skin (cutaneous membrane) Subcutaneous tissue below the skin Accessory Structures Sweat glands Sebaceous or oil glands Hair Nails. Layers Of The Skin. Epidermis – outer composed of stratified squamous epithelium
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The Integumentary System Chapter 4
Integumentary System Includes: • Skin (cutaneous membrane) • Subcutaneous tissue below the skin • Accessory Structures • Sweat glands • Sebaceous or oil glands • Hair • Nails
Layers Of The Skin • Epidermis – outer • composed of stratified squamous epithelium • Dermis – inner • anchored to a subcutaneous layer • Hypodermis • subcutaneous fat (adipose) layer – • energy storage
Epidermis • Composed of stratified squamous epithelium • Avascular- as it has no blood supply of its own • Oxygen and nutrients diffuse from the underlying dermis
Click here to copy the picture “skin, thick trichrome” And paste it here. Click here to copy the picture “skin, thin H&E” And paste it here.
First Layer of the Epidermis Stratum Basale • Deepest layer of the epidermis (closest to the dermis). • Consists of a single layer of columnar or cuboidal cells • Renewal - takes about 3 to 4 weeks • Cells here undergo keratinization • keratin- a tough protein, is deposited within the cell. • keratin hardens and flattens the cells as they move outward and it waterproofs the skin.
Epidermal Layers • Stratum spinosum • Consists of spiny prickle cells that interlock to support the skin. • Stratum granulosum • This thin middle layer, initiates keratinization (production of keratin). • Stratum lucidum • This thick layer appears only in frequently used areas such as palms of the hands and soles of the feet.
Final Epithelial Layer Stratum Corneum • Outermost layer • Thick with rows of dead cells. • These cells contain soft keratin, which keeps the skin elastic and protects underlying cells from drying out. • Act as barrier against microbe invasion.
Dermis- Called "true skin, " is the layer beneath the epidermis. Its major components are: • collagen (a protein that adds strength) • reticular fibers (thin protein fibers that add support) • elastic fibers (a protein that adds flexibility)
Click here to copy and paste the picture “skin, thick van Gieson elastin”
Skin Color Skin color results from the presence of : • Melanin- keeps excessive ultraviolet rays from burning the skin. Exposure to sunlight -> more melanin, causing suntan, a temporary change in skin color. Melanin-rich cells move toward the surface. • Carotene -yellow to orange pigment usually hidden by the effects of melanin. underlying blood reflected through skin. • Hormones produced by the pituitary and the adrenal glands also affect pigmentation. • Diseases of these two organs often result in changes of the skin.
Melanin Click here to copy and paste a picture of The integument showing melanocytes stained blue
Malfunctioning Melanocytes • Albinism – melanocytes completely fail to secrete melanin. Hair, skin, and iris are white. • Freckles and molesare formed when melanin becomes concentrated in local areas. • Malignant melanoma– a cancerous change in a mole that may metastasize (spread) rapidly and is most difficult to treat. Exposure to sunlight increases risk. • Vitiligo – loss of pigment in certain areas of the skin producing white patches.
Other Pigments in Skin • Pinkish color – seen in fair-skinned persons because the vascular dermis is visible. • Cyanosis – blue look to skin due to poorly oxygenated blood • Blushing – caused by dilation of blood vessels • Pale by fright – caused by restriction of vessels
Response to Disease • Jaundice – when bilirubin is deposited in skin because a diseased liver is unable to excrete this pigment • Bronzed skin-due to the deposit of excess melanin when a person’s adrenal gland is functioning poorly. • A bruise or contusion indicates that blood has escaped from the blood vessels and has clotted under the skin. • Over eating carotene-rich vegetables such as carrots may cause skin to have a yellow tint.
Accessory Structures of the Skin • Hair –(most)skin is haired -the hair is (usually)short, fine and only lightly pigmented. • Truly hairless -the palms of hands • soles of feet • sides of fingers and toes • parts of the external genitalia.
Accessory Structures of the Skin • The free part of each hair is called the shaft. • The root of each hair is anchored in a tubular invagination of the epidermis, the hair follicle. • The hair that you groom daily is actually dead keratinized cells. • Each has an associated bundle of smooth muscle, the arrector pili muscle. causes your hair stand up on its end.
Hair Color/Texture/loss • Hair color is determined by the amount and type of melanin present. • Melanocytes become less active with age= Gray hair • Red hair results from a modified type of melanin that contains iron. • The shape of the hair shaft determines texture. • Alopecia is the term for hair loss. • Alopecia Areata- is an autoimmune disease where the immune system recognizes hair follicles as foreign invaders and attacks them. The disease is complex and different for everyone.
Accessory Structures of the Skin • Nails • Plates of stratified squamous epithelial cells with hard keratin • Protect distal ends of phalanges • Nail growth occurs in the lunula • Athlete's foot is a fungal infection that develops in the moist areas between your toes and sometimes on other parts of your foot.
Exocrine Glands • Sweat glands or sudoriferous glands - simple coiled tubular glands., divided into two principal types: • eccrine and apocrine. • Apocrine glands - found mainly in the skin of the armpits, anogenital areas and of the areola of the breasts. • They start secreting at puberty. • Eccrine glandsare the most common. • Produce sweat, a watery mixture of salts, antibodies and metabolic wastes. • Sweat prevents overheating & helps regulate body temperature. • Ceruminous glands-produce ear wax glands • Mammary glandsProduce milk -are modified apocrine sweat glands.
Physiology of the Skin • Protection - the epidermis provides a barrier to fluid loss from the body. • Barrier Function - intact skin prevents the entry of micro-organisms into the body. laceration - a torn ragged wound • Antimicrobial proteins - they act by piercing holes in the outer membranes of micro-organisms. • Resistance to wear and tear - continuous replacement of the outer epidermal cells that wear off.
Continued • Excretion- water, salt, and small amounts of waste products such as urea. • Vitamin D -can be synthesized in skin exposed to sunlight ( also be obtained from the diet) • Barrier- to ultraviolet light. The melanocytes absorb UV radiation. • Skin exposed to sunlight- wrinkled and crease. • Dried blood and tissue fluid will create a scab.
Cancer • Ultraviolet light causes mutations at points on a DNA strand. • Three types of skin cancer corresponding to three major types of skin cells: • basal cells • squamous cells • melanocytes. • Cancer of melanocytes - malignant melanoma - is the most lethal variety, but also the least common.
Sensory The integumentary system is well-supplied with receptors for touch, pain, temperature, vibration and pressure. Sensory information is relayed to the central nervous system via sensory nerves 3 types of receptors for touch- Meissner corpuscle, Merkel disk, Krause end bulb. 2 types of receptors for pressure-Pacini corpuscles, and Ruffini endings. Free nerve endings- sense pain, heat and cold (READ YOUR HANDOUT)
Burns-pg 76 in your text First-degree - red and very sensitive to touch, involve minimal tissue damage Sun burn is a good example. Second-degree - affect both the outer-layer (epidermis) and the under lying layer of skin (dermis) causing redness, pain, swelling and blisters.- often affect sweat glands, and hair follicles.
Burns Third-degree- affect the epidermis, dermis and hypodermis, causing charring of skin or a translucent white color. Usually result in extensive scarring. Fourth degree- involves tissues down to the bone. Chances of survival –not good Major concern with burns-fluid and heat loss and bacterial infection.
“Rule of nines” You can estimate the body surface area on an adult that has been burned by using multiples of 9. Head = 9% Chest/Abdomen (front) = 18% Upper/mid/low back and buttocks = 18% Each arm = 9% Groin = 1% Each leg = 18% total (front = 9%, back = 9%)