The Integumentary System -the skin and its various accessory structures, and the membranes -functions to protect the body against infection, physical damage, and temperature changes -the largest organ in the body I. Epidermis

Epidermis

The Integumentary System -the skin and its various accessory structures, and the membranes -functions to protect the body against infection, physical damage, and temperature changes -the largest organ in the body I. Epidermis -protects the body against infection and ultraviolet radiation -cells have about 40-day life cycle, shortest-lived cells A. Stratum corneum -“horny layer” -made up entirely of dead, flattened, highly- keratinized (tough, waterproof) keratinocytes -cells contain carotene, yellow/orange pigment most evident in palms and soles, calluses

Stratum corneum Epidermis

The Integumentary System -the skin and its various accessory structures, and the membranes -functions to protect the body against infection, physical damage, and temperature changes -the largest organ in the body I. Epidermis -protects the body against infection and ultraviolet radiation -cells have about 40-day life cycle, shortest-lived cells A. Stratum corneum -“horny layer” -made up entirely of dead, flattened, highly- keratinized keratinocytes -cells contain carotene, yellow/orange pigment most evident in palms and soles, calluses B. Stratum lucidum -“clear layer” -extra layer found in palms and soles C. Stratum granulosum -site of deposition of keratin granules D./E. Stratum germinativum

Stratum corneum Epidermis Stratum lucidum Stratum granulosum

D. Stratum spinosum -“spiny layer” -thick layer where keratinocytes are pushed farther from the nourishing blood supply of the dermis, progressively die and flatten out E. Stratum basale -produces keratinocytes -also contains melanocytes, which produce melanin to deposit in deeper layers of the Stratum spinosum

Epidermis Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale

D. Stratum spinosum -“spiny layer” -thick layer where keratinocytes are pushed farther from the nourishing blood supply of the dermis, progressively die and flatten out E. Stratum basale -produces keratinocytes -also contains melanocytes, which produce melanin to deposit in deeper layers of the Stratum spinosum Rx—Basal Cell Carcinoma -cancer of the keratinocyte-producing cells of the stratum basale 1. Melanocytes -produce melanin, a brown pigment which absorbs visible and ultraviolet (UV) light -all people have about the same number of melanocytes, but differ in the amount of melanin produced by each cell, which is gentically determined, lighter skin thought to be an adaptation for survival against Ricketts and osteomalacia in temperate zones

Rx—Malignant Melanoma -cancer of the melanocytes, very quickly metastasizing and deadly form of skin cancer 1. Melanocytes -keratinocytes further pigmented with carotene (orange) Rx—Albinism -recessive genetic disorder in which melanoctyes are unable to synthesize melanin ♂ ♂ A A A a ♀ ♀ Carrier Carrier Carrier a Aa Aa A AA Aa Normal Normal Normal Normal Carrier Carrier Carrier a a Aa Aa Aa aa Normal Normal Normal Albino

An individual who produces as much melanin as humanly possible has genotype MMLLNN. That person’s phenotype would be to have very dark skin, so brown as to almost appear black. MMLLNN During meiosis, the diploid (2n) genotype, MMLLNN, Is reduced to the haploid genotype. As the alleles are segregated from each other, the only possibility for the sperm or egg is MLN. MLN MLN

Section 15-1 The union of one genetic half-cell, the sperm, with the other genetic half-cell, the egg, results in one genetically whole cell, the zygote MLN sperm + MLN egg MMLLNN zygote fertilization

Add the alleles from the sperm (MLN) and the alleles from the egg (MLN) to determine the genotype of the zygote (and the new individual), (MMLLNN)

The genotype of all the offspring, (1 out of 1, or 1/1), is MMLLNN, so all the offspring have the same phenotype—very dark skin.

An individual who produces as little melanin as humanly possible has genotype mmllnn. That person’s phenotype would be to have very light skin, so as to appear so white that the pink of the blood shows through. mmllnn mln mln During meiosis, the diploid (2n) genotype, mmllnn, is reduced to the haploid genotype. As the alleles are segregated from each other, the only possibility for the sperm or egg is mln.

Add the alleles from the sperm (mln) and the alleles from the egg (mln) to determine the genotype of the zygote (and the new individual)

The genotype of all the offspring, (1 out of 1, or 1/1), is mmllnn, so all the offspring have the same phenotype—very light skin. In both examples, when the very dark mate with the very dark and when the very light mate with the very light, the crosses result in no variation. What happens if the very dark mate with the very light?

Add the alleles from the sperm (MLN) and the alleles from the egg (mln) to determine the genotype of the zygote (and the new individual)

The genotype of all the offspring, (1 out of 1, or 1/1), is MmLlNn, so all the offspring have the same phenotype—medium skin. In all three examples, when the very extreme mate with the very extreme, the crosses result in no variation. What happens if the medium-skinned mate with the medium skinned? If Melvin, who has genotype MmLlNn for shade of skin color, and Melanie, who has genotype MmLlNn for shade of skin color, have 10 children, how many, according to the odds, should have the same shade of skin color as their parents?

During meiosis, the diploid (2n) genotype, MmLlNn is reduced to the haploid genotype. As the alleles segregate and assort independently, maximum diversity results. mln MLN MLn mlN MmLlNn mLn MlN mLN Mln

Add the alleles from the sperm (MLN) and the alleles from the egg (MLN) to determine the genotype of the zygote (and the new individual), (MMLLNN)

Now do the same for the other possible combinations of sperm and eggs, filling in the boxes of the Punnet square

Now, fill in the rest of the squares

If you count up the number of alleles represented by capital letters, you get the number of alleles that code to make a person’s hair, eyes, or skin darker, because each allele represented by a capital letter causes skin cells to make more melanin (brown pigment)

The number of alleles coding for the cells to make melanin determine how genetically dark the individual’s hair, skin, or eyes will be. Count up the alleles and total them in the first square

The number of alleles coding for the cells to make melanin determine how genetically dark the individual’s hair, skin, or eyes will be. Count up the alleles and total them in the first square

Now, count up the alleles coding for melanin production and total them in each square of the Punnet square

Now, count up the alleles coding for melanin production and total them in each square of the Punnet square

Now, fill in the rest of the squares in the Punnet square Now, fill in the rest of the squares in the Punnet square. Notice there is a pattern to the numbers.

Count how many sixes, fives, fours, threes, twos, ones, and zeroes, out of 64, and write the totals in the data table on the next slide.

Now, plot the data on the graph, with the numbers of alleles on the x-axis and the number of individuals on the y-axis. 1 6 15 20 15 6 1

Now, plot the data on the graph, with the numbers of alleles on the x-axis and the number of individuals on the y-axis. 1 6 15 20 15 6 1

Now, plot the data on the graph, with the numbers of alleles on the x-axis and the number of individuals on the y-axis. 1 6 15 20 15 6 1

II. Dermis -protects body from changes in temperature by housing blood vessels, glands, and producing hair -made from collagen and elastin form elasticity A. Hair -can be elevated to trap air for further insulation -offers some physical protection (padding) -axillary and pubic hair linked to apocrine glands -protects against pathogens entering eyes, ears, nose, etc. B. Sebaceous (Oil) Glands -produce sebum (oil) to lubricate skin and protect it from drying out -provide sebum as food source for mutualistic bacteria (Staphylococcus epidermidis) which compete biologically with pathogens (Staphylococcus aureus) Rx—Acne -infection of a sebaceous gland or hair follicle by S. aureus, or other bacteria which feed on oil and produce toxic by-products which damage cells; attack of white blood cells (neutrophils) create pain, swelling, redness, pus

hair Epidermis Sebaceous (oil) gland Dermis

II. Dermis C. Sudoriferous (Sweat) Glands -produce sudor (sweat) as protection against heat by evaporative cooling -protect from pathogens by uric acid, which lowers pH of skin 1. Eccrine glands -most numerous and widespread sweat glands, especially concentrated in palms, soles, forehead 2. Apocrine glands -less numerous, large, high volume sweat glands associated with hair, especially concentrated in axillary and anogenital areas -secretions sometimes associated with stress or sexual arousal

hair Epidermis Sebaceous (oil) gland Dermis Sudoriferous (sweat) gland

II. Dermis C. Sudoriferous (Sweat) Glands 3. Ceruminous glands -produce cerumin (earwax) in ear canal to protect tympanic membrane (eardrum) and inner ear 4. Mammary glands -modified sweat glands which produce milk in mammals to nourish young D. Dermal Blood Vessels -regulate body temperature by dilating (cooling) or constricting (preventing cooling) -along with faster heart rate, speeds cooling, transfer of heat from outside to inside of body

E. Nerve Endings -protect by sending sensory information about skin to cerebral cortex 1. Free Nerve Ending -sense pain, temperature 2. Tactile (Meissner’s) Corpuscle -sense light touch 3. Lamellated (Pacinian) Corpuscle -sense deep pressure III. Subcutaneous Layer (Hypodermis) -stored adipose (fat) provides protection by cushioning and thermal insulation -Swedish bikini team?

Lamellated (Pacinian) hair Tactile (Meissner’s) Corpuscle Epidermis Papillary Layer Dermal blood vessels Sebaceous (oil) gland Dermis Free nerve ending Reticular Layer Sudoriferous (sweat) gland Subcutaneous Layer (Hypodermis) Lamellated (Pacinian) Corpuscle

Rx—Burns -cell damage by heat, electricity, radiation, acids, and bases -loss of fluids and electrolyte imbalance (leading to renal shutdown and circulatory shock) -open up body to infections 1. First degree -only damage to epidermis -sunburn -redness, swelling, pain (localized) 2. Second degree -epidermis and papillary layer of dermis -same symptoms as first degree, plus blistering 3. Third degree -all epidermis, papillary and reticular layer of dermis -skin gray or blackened -no pain or blistering -prevent circulatory shock, prevent infection -treated with pig or cadaver skin as temporary graft -skin grafts (autografts), grown outside of body in tubes -artificial skin grafts made from plastic, collagen from cattle, or ground cartilage from sharks