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The Integumentary System. Ya gotta have skin to keep your insides in!!! Chapter 5 pages 142-159. Skin Factoids. Skin is part of the Integumentary System. -Largest organ of the body. (21.5 ft 2 )( 12-15% of body weight). -Thickness varies: .5 cm on upper back .05 cm on eyelids
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The Integumentary System Ya gotta have skin to keep your insides in!!! Chapter 5 pages 142-159
Skin Factoids Skin is part of the Integumentary System. -Largest organ of the body. (21.5 ft2)( 12-15% of body weight). -Thickness varies: .5 cm on upper back .05 cm on eyelids Hair and sweat glands are not located in all areas! • No hair on the palms - No sweat glands on the eye lids.
Skin Trivia Skin is always being replaced from within. Most of the dust in your house is dead skin. By the time you are 70 you will have shed 70 lbs. of skin. • Skin is important in helping the body to maintain homeostasis (“steady state) of such things as body temperature, fluid balance and disease protection.
General Skin Structure • 2 main layers - epidermis and dermis • Epidermis • 4 to 5 layers of epithelium • 3 main cell types • Keratinocytes • Melanocytes • Langerhans cells (like the one pictured here) are free ranging white blood cells that are found in the stratum spinosum. They phagocytize foreign material and bacteria.
The skin as an ecosystem • The skin supports a wide variety of microorganisms. • Species of Bacteria and yeasts inhabit the surface of the skin and help to protect us from more dangerous microbes. • We are all hosts of tiny mites which feed on our dead skin. • They are most common in the eyebrows and eyelashes. • All houses have dust mites that eat the dead skin that accumulates in pillows and cushions. • These mites can become very numerous and some people can become allergic to their droppings. • It is suspected that this may be the explanation for some cases of asthma.
This picture shows a group of follicle mites nested in the follicle of an eyebrow.
Perspiration • Inactive person (3 mL/hr) • Active person (1 L/ hr) In hot climates this can increase to 2 to 3 L/hr in 6 weeks. • In addition to cooling the body sweat provides nutrients for certain bacteria and fungi that lie on the skins surface. • These bacteria produce lactic acid which prevents many kinds of harmful bacteria from growing on the skin! • Sweat is produced in the sweat glands and exits through the sweat pore. • It is mostly water. There is some urea, salts, proteins and oils that are also secreted.
Sebaceous glandSecreting oil to help lubricate and protect the hair shaft.
Apocrine glands Apocrine sweat glands are formed from the same structure as the hair follicle and sebaceous glands. • They produce a thicker, viscous liquid that produces a noticeable odor. • The apocrine glands become very active with the onset of puberty. They are found in the armpit and the genital area. • The milk glands in the breasts are modified apocrine sweat glands. • Body odor is produced by micro-organisms that grow where the apocrine glands exist. • The bacteria produce an odor as they digest this sebum. • Since they can only do this if water is present many deodorants are antiperspirants as well.
Functions of Skin • The skin provides protection against mechanical injury. • The skin helps to prevent the penetration of many kinds of harmful chemicals. • This photograph shows a typical case of poison ivy. Poison ivy is caused by an allergic reaction between the body and an oil, urushiol, that is produced by this plant. • 85% of the people in the US are sensitive to this oil.
Functions of Skin • The skin, with its continuous waterproof covering, helps to prevent microbes from getting inside the body. • The skin is host to a community of microbes that assists in the prevention of disease.
Functions of Skin • Prevention of dehydration. For burn patients who lose more than 50% of their skin, they are very likely to become severely dehydrated. • The skin provides protection of the internal sea that bathes all of our cells. • This picture is of human skin magnified 1000X by a scanning electron microscope.
Functions of Skin • The skin helps to maintain a constant body temperature. • Extensive capillary networks and sweat glands help to radiate excess heat and to cool the body through evaporation of water.
Functions of Skin • Excretion of Wastes. • Water, urea and some salt are excreted when people sweat. • Recently people discovered a new compound in sweat, a protein called dermicidin. • This protein seems to play a role in inhibiting bacterial growth.
Functions of Skin • The skin serves as a large sensory receptor organ of the body. • Many nerve endings end in the skin. • Sensations include touch, pressure, heat, cold, and pain. • Meissner’s corpuscle (fine touch), • free nerve endings (touch, pressure and pain, (tickle?). • Merkel’s discs (light touch and pressure), • Krause’s end bulbs (cold?), • Pacinian corpuscle (heavy pressure and vibration)
Skin nerve receptors • Pacinian corpuscle • Sensitive to heavy pressure and vibration • Abundant near joints and skeletal muscles, palms and soles
Meissner’s corpuscle • Fine touch receptors • Found in high concentrations in fingertips • Important in two point discrimination
Skin nerve receptors • Pain, cold and warmth nerve receptors are free nerve endings located very close to the epidemis • Cornea of the eye contains only these nerve receptors
Cold and Warmth • Detected by specific free dendrites • 3 to 10 times more cold than warm receptors • Extremes in temp. (<100 C and >450C) involve pain receptors
Functions of Skin • Vitamin D synthesis • Skin that is exposed to the sun will produce Vitamin D. • Vitamin D seems to play a role in preventing certain types of cancer.
Hair Structure and function • Hair protects the head, eyes and ears. • For creatures in cold climates often there are two layers. • Most hair structure is the same. • Hair grows at different rates.
Hair continued • Composed of keratin • Grows in cycles • Grows faster in the morning than the evening. • Curly hair is oval in shape • Grey hair lacks pigment
Hair Transplants • The first step in the hair transplant process is the design of the hairline. • Next the donor area is prepared. • Hair in the back is lifted and a narrow strip of hair is trimmed to about 1/16th of an inch.
Hair Transplant Procedure • Both the top and the back of the scalp are then anesthetized. • Patients are given the option for nitrous oxide (laughing gas) while the local anesthesia is applied. • Narrow strips of hair bearing skin are removed from the donor area and the hair from above and below is then brought back together with a running stitch. • The stitches are covered by your hair and removed in ten days, usually leaving a thin scar line that is concealed by your own hair.
Hair Transplant procedure • From the donor strip tiny grafts are prepared. • Grafts for the hairline are usually between 1 to 3 hairs and are dissected under a microscope to preserve every follicle possible.
Hair Transplant procedure • The hair transplant surgeon next creates the sites where the grafts will be placed. • Tiny slit incisions are made at the hairline for the smallest single hair grafts.
Hair Transplants cont. • As the surgeon works back he will make gradually larger slit and slot incisions (approximately 1/32" wide by 1/8" long) . • After the procedure most patients are given a baseball cap or bandana. • There is usually no bandage and the hair can be washed in two days. • Tiny crusts will form where the transplants have been placed and usually shed in 4 to 7 days. • The small hairs in the newly transplanted grafts normally shed within 2 to 4 weeks after the procedure. • Permanent hair growth usually begins in 8 to 12 weeks. Significant hair growth within 6 to 8 months and full hair growth within 9 to 12 months.
Nails • Horny plates composed of keratin • Growth occurs in nail matrix. • Cells grow and fill with keratin • .1 mm/day average growth rate
African Black Rhinoceros • The horns of the Black Rhinoceros is made up of the same protein as found in your nails and the stratum corneum. • The Black Rhinoceros’ thick skin is really a very thick layer of keratin filled cells.
Skin pigmentation • Oxyhemoglobin, carotene and melanin determine skin color • Melanin produced by melanocytes in stratum basale. • Melanocytes thought to originate from nervous tissue. • Melanin produced in reaction to UV radiation.
Burns • Classified by degree • 1st degree - redness, swelling • 2nd degree - blisters • 3rd degree - destroyed skin tissue. • 2nd and 3rd degree burns need medical attention. • Burns to the head, neck and groin are the most serious. • When the skin is burned, it can’t protect the body against bacteria, prevent the loss of body fluid, or keep the body at a normal temperature. • 2nd and/or 3rd degree burns over 30% of the body are usually fatal.
Burn Care • The patient is placed in a special cart that allows for cleansing of the burned area. • Cleansing is initially done with soap and water. • Medication is given to relieve pain and antibiotics and bandages are used. • Surgery is performed to remove dead and dying tissue. (debridement) • Skin grafting is done using skin from healthy areas of the patient. • If the area burned is large it may be necessary to do more than one grafting operation.
Skin Grafting • Dead skin is removed from the damaged area (debridement) • A section of skin larger than the injury is placed over the burn and covered with bulky, wet bandages that have been soaked in an antibiotic. • The graft begins to grow and adhere in 48 hours and usually is totally attached in 4 to 5 days. • The patient will need to protect this area for up to two weeks before it is totally healed
Artificial Skin • The typical cover for extensive burn wounds was cadaver skin, known as allografts. • The skin grafts did not always have the desired effects. They sometimes introduce disease to the burn victim or were rejected by the body. • In the 1980’s artificial skin was successfully developed. • Fibroblasts from neonatal foreskin samples are enmeshed in a collagen gel. • After several weeks keratinocytes are added and they form an epidermal layer.
Artificial Skin • An artificial skin graft eliminates the need for tissue typing. • Artificial skin can be made in large quantities and frozen for storage and shipping, making it available as needed. • Each culture is screened for pathogens, reducing the chance of infection. • Because artificial skin does not contain immunogenic cells such as dendritic cells and capillary endothelial cells, it is not rejected by the body. • Finally, rehabilitation time is significantly reduced.
Skin Cancer • 3 kinds basal, squamos and melanoma • Basal cell carcinoma involves cells in the stratum basale which become cancerous • Usually noticed as persistant skin ulcers. • metastasis is uncommon
Skin Cancer • Squamous cell carcinoma • Begins in stratum spinosum • Metastasis may occur so these growths are operated on as soon as they are diagnosed.
Skin Cancer • Malignant Melanoma is cause by cancerous melanocytes • Metastasis is common and early treatment is essential • Increased 600% in last 15 years • 6/7 of all skin cancers • Most common cancer in women aged 25-29. • Often starts as a mole that suddenly changes in size and texture.
Wounds • Injured cells release histamine which causes swelling and dialation of blood vessels. • White blood cells released from bone marrow. • Clot forms • A decrease in chalones causes increased cell division. • The drying scab helps to pull the injured layers together. • Fibroblasts in the dermis produce collagen which fills in the wound below the scab.