1. Chapter 4

2. Guiding Question: What are the components of the integumentary system?

3.  Not just a covering for the body Largest organ  Blood vessels, connective tissue structures, glands, hair, nails, nerves, skin Plays a large role in homeostasis  Has inherent and adaptive characteristics Calluses Darken in sun Elasticity Sensitive to moisture

4. Guiding Questions: 1.) What embryonic layers form the integumentary system? 2.) Describe the development of the integumentary system. 3.) What are some various causes of hair loss?

5. 4-5 weeks: outermost layer of skin form a simple squamous tissue that becomes stratified as the embryo develops from the ectoderm  In some areas forms nervous tissue that later becomes integrated into the skin structure. 6-7 weeks: deeper parts of skin begin to form from mesoderm. 8-9 wks: mesenchyme begins to mature and fibroblasts form, and dents occur in the upper squamous layer—form lanugo. 10 weeks: ridges form between the outer and inner layers of skin—so don’t separate when rubbed 11 weeks: small nails at the tips of fingers & toes, followed by development of special blood vessels in the layers of skin  Angiogenic factors stimulate the production of these vessels 20 weeks: Glandular structures form  Inward growths of the outermost squamous cell layer  Will eventually produce oils and sweat 25 weeks: Pigmentation About 26 weeks: melanoblasts mature into melanocytes, and nervous tissue structures develop

6.  Ectoderm & mesoderm in origin  Skin is a complex structure  Many things can go wrong in its development  Let’s make a timeline!

8.  What are the three major layers of the skin?  Describe the basic characteristics of the three major layers of the skin (recommend a chart)

9. 1. Epidermis: Epithelial  Superficial & thinnest  cells are very tightly packed  New cells produced here 2. Dermis: Connective  Deep to epidermis & thick  Primarily connective tissue  loosely packed cells 3. Subcutaneous/Hypodermis (adipose tissue) Deep to the skin/dermis Layer of insulation

11.  Outermost: Stratum corneum Dry, dead, keratin filled (waterproof, tough)  Stratum Granulosum Waterproof Contains granules of keratin  Stratum Spinosum “Prickly” layer Contains Langerhans cells (fight infections)

12.  Stratum germinativum / basale Cells undergoing mitosis, move up and horizontally Contains malpighian layer or “Pigment layer” with melanosomes Forms epidermal ridges

14. Stratum corneum: Dead squamous cells Stratum corneum: Dead squamous cells Stratum Germinativum/ Basale: dividing columnar cells Stratum Spinosum: cuboidal cells, desmosomes hold together >> spiny Stratum Spinosum: cuboidal cells, desmosomes hold together >> spiny Stratum granulosum: Granules with lipids and keratin – forms waterproof layer Stratum granulosum: Granules with lipids and keratin – forms waterproof layer Stratum lucidum: (only in thick skin); oils from lysosome disintegration

15.  Specialized cells within epidermis: Melanocytes  Melanin: pigment, inc. w/sun (protection) Keratinocytes  Keratin: tough, waterproof material  Abrasion resistance for cells Langerhans cells  Immune response against microbes invading the skin

16. Second layer of the skin

17.  Collagen, elastin fibers– scattered

18.  Dense, irregular connective tissue  Loose, connective tissue = areolar connective tissue Binds blood vessels, membranes, muscles, nerves, and skin to other structures Contains extensive meshwork of protein fibers (fibroblasts)  Involved primarily in body growth  Connective tissue maintenance  Wound healing

19. Dermal papillae: parallel rows of peg-like projections Unique to each individual; akin to fingerprints

20. Third layer of the skin

21.  Third, innermost layer of the skin  Thickness, composition vary throughout body  Composed of loosely-arranged elastic fibers that anchor the skin to the fascia Sheet of fibrous connective tissue Covers muscles, skull bones, some organs  Large amount of adipose (fat) cells  Large network of blood vessels, capillaries, lymphatic vessels

22.  Glands  Nerves  Nails  Hair

23.  3 Types: Ceruminous Sebaceous Sweat

24.  Produce cerumen (waxy secretion), an apocrine secretion (ear wax)  Found lining ear canal

25.  Holocrine glands (secrete whole dead cells)  Produce, store abundance of fat, which burst and die, releasing sebum

26.  Sebaceous Glands Secrete oil (sebum) for hair/skin Ducts open into hair follicles Accumulated sebum enlarges ducts>>white heads Darkened sebum>>black head

27.  Sudoriferous Glands Eccrine Glands  Widespread  Watery Fluid Apocrine Glands  Armpits/Genitals  Thick/milky fluid

28.  Aprocrine Odorous, sweat-like material in armpits, navel, groin region, areolae Inactive until puberty Contain pheromones Broken down by bacteria, creating odor  Eccrine Skin of armpits, foreheads, palms, soles Mostly secrete water, w/ salts, organic compounds, and wastes (like urea) Microbes feed on these as well, producing odors

30.  Specialized structures: Hair follicle: cells of the epidermis extend into the dermis forming a small tube Hair bulb: base of the follicle Hair papilla: cluster of cells (live); nourished by BV’s Root: part of hair hidden in follicle Shaft: visible part of hair

31.  Sensory receptors Communicate information from environment to the body Found in all skin layers  Mostly in innermost regions, fascia  Free nerve endings Pain-sensing structures Found throughout inner part of epidermis Detect chemicals associated with tissue damage and bleeding

33.  Merkel cells Sensitive to gentle physical sensation Found in stratum germinativum Abundant in fingertips

34.  Elongated, club-shaped pile of connective tissue  Upper region of dermis (in dermal papilla)  Respond to touch

35.  Look like onions  Deeper parts of hypodermis  Hard pressure, vibrations

36.  Pressure, constant touch

37.  Sensitive touch receptors  Found mostly in mucous membrane of mouth

38.  Merely a keratin secretion  Nail root Lies beneath skin-nail fold Grow back as long as nail root and skin-nail fold are not severely damaged Grow 1/8 in per month

39.  Modified stratum corneum  Grows from an individual follicle buried in subcutaneous layer

42.  Specialized Structures (continued) Arrector pili: tiny, smooth muscle attached to base of dermal papillae & side of hair follicle  Contracts: pulls on both simultaneously>>goose bumps

45.  What are the major roles of the integumentary system?  What are “commensals”?  How does heat regulation in the skin work?  How does sensation in the skin work?  Briefly describe the three classifications of burns

46.  Protection  Heat regulation  Sensation  Waste excretion

47.  The skin protects from: Chemical Damage  Can break down connections between cells  Can disintegrate cells  Sweat dilutes & neutralizes  Cerumen and sebum are oily barriers  Repels water  Repels dangerous chemicals that are dissolved in water  Prevents water from escaping the body through the skin.

48.  The skin protects from: Mechanical Damage  Any type of force that can compress, erode, stretch or tear the skin.  Loose connective tissue = flexibility  Shedding stratum corneum = reduce erosion  Calluses, adipose tissue and reticular fibers = shock absorption to minimize compression damage

49.  The skin protects from Microorganism damage  Produce destructive secretions in sebum / sweat  Kept in check by chemicals that benefit commensals— ”good” bacteria and yeast that reduce the chance that harmful bacteria will survive on the skin.  Shedding of stratum corneum removes microorganisms

50.  The body’s ability to maintain a constant internal temperature (98.6F) Blood vessels contract / expand Evaporation of the sweat from the surface Adipose tissue is a natural “blanket”

51.  Sensation: received stimuli from the environment which is interpreted in a way that the brain can comprehend Done by sensory nerves in the skin Cold, heat, injury, pressure, stretching, touch Transducers: nerve cells that convert various environmental messages into body signals.

52.  Eccrine sweat glands Removes urea, organic chemicals, and excess salts Not as efficient as the Excretory System  Other functions Vitamin D production when exposed to sunlight Predictor of a person’s health

53.  Skin loses ability to maintain homeostasis locally and for the whole body  Sun, cooking, acids, bases, corrosive chemicals, electricity, fires, and steam rooms  Damage the skin differently  Severity of burn is based on the extent of the skin damage.

54.  Reddening, swelling  Superficial damage  Steam, sun

56.  Damage to Strata spinosum & basale  Blisters, reddening, swelling and fluid build up under the epidermis

58.  Entire epidermis affected, could be missing so stratum basale not available  Damage to dermis: nerve cell loss  Pain registers b/c histamine from immune system is released in response to the damage.  Susceptible to dehydration, loss of body heat, and infection

60.  Skin entirely damaged; bone, muscle underlying skin damaged as well.  (Too graphic to show)