INTEGUMENTARY SYSTEM

1. INTEGUMENTARY SYSTEM Skin, hair, nails, and glands

2. What does it mean? • Integere (Latin)- “to cover” • Dermato and cutis (Greek and Latin)- “skin” • Epi- (Greek)- “upon” or “above”

3. Why do we need it? overview • Largest organ • Retains moisture • Sensory receptors for: • pain, • Heat • Touch • Excretes salts • Excretes small amounts of waste • Stores blood • Regulates body temp.

4. 2 main parts • Epidermis and dermis • Under the dermis is the hypodermis (supericial fascia- subcutaneous tissue) • It acts a foundation not truly part of the skin

5. Epidermis • Surface skin • 1st line of defense against infection • Contains no blood vessels • Layers and layers of epithelial cells

6. Melanocytes • ¼ of stratum basale is made of these • Synthesize a pale yellow to black pigment called melanin • Cytocrine secretion- melanin is secreted into keratinocytes • Melanin- skin color and protection against uv rays • Keratinocytes • majority of stratum basale • Primary epithelial cell of skin

7. More about the epidermis • Carotene- in stratum corneum and fatty layers beneath the skin • Produces yellowish hue common with Asian ancestry • Hemoglobin- cause for pinkish color of Caucasian skin • Less melanin, more hemoglobin • Albinos- no melanin in skin at all • Ridges and grooves- increase friction to grasp other objects • Ex. Loops and whorls (fingerprints, palm prints, footprints)

8. The Dermis • Also known as the corium • Thicker and more fibrous than the dermis • 2 layers • Fibrolasts- connective tissue develops • Macrophages- engulf wastes and foreign microorganisms • Adipose tissue • Thinnest over eyelids and male sex organs • Thicker on back than stomach • Thickest on palms of hands and soles of feet

9. Papillary Layer • Top (outer) layer • Soft • Elastic, reticular fibers that enter the epidermis • Brings blood and nerve endings closer • Papillae are finger-like projections- loops of capillaries to increase the surface area of dermis and anchor epidermis • Meissner’s corpuscles- nerve endings sensitive to soft touch. • In some papillae

10. Reticular Layer • Rete- net (Latin) • Dense, irregular connective tissue • Interlacing bundles of collagenous and elastic fibers • Strong resistant layer • Gives skin strength, extensibility, ad elasticity • Oil glands (seaceous glands), sweat glands, fat cells, and larger blood vessels are in this layer

11. Hair • Follicles embedded in the epidermis and extend to the dermis angle hair growth (curly or straight). • Follicle bases are expanded (called bulbs) reach nerve endings • Epithelial cells in the bulb divide to create the hair shaft • Hair pigment: melanin • Gives hair its color • Gray and white hair grow when melanin levels decrease and air pockets form • sebaceous gland- sebum is produced (cholesterol, fats, and other substances) • Keeps hair soft, pliable, and waterproof

12. Hair has 3 layers • Medulla • Central core • Cells contain eleidin separated by air spaces • Fine hair- minimal/ nonexistent • Cortex • Major part of hair shaft • Several layers • Flattened cells • Elongated pigment-bearing cells in dark hair • Air pockets in white hair • Cuticle • Single layer, overlapping cells with free end pointing up • Strengthens and compacts the inner layers • Split ends • Abrasion wears away the end of the shaft, exposes the medulla and cortex to create the horrid split end

13. Sweat? Gross…or is it? • 2 types of sweat glands (sudoriferous) • Coiled tubules in the dermis • Eccrine glands-all over body • Watery (99%), salty secretion known as sweat • Passes through the epidermis to skin’s surface and opens to a sweat pore • Controlled by the sympathetic nervous system • Apocrine sweat glands • Under the armpits and groin area, associated with hair follicles • Same components as eccrine and is odorless • Bacteria breaks down apocrine sweat’s fatty acids and proteins • Creates the odor accompanying post exercise

14. Connection to the Nervous System • 4 receptors are involved in the sensation of touch • 2 primary temperature receptors • Dermis has neuromuscular spindles (proprioceptors) • Transmit information to the spinal cord and brain about the lengths and tensions of muscles • Provides awareness about the body’s position • Spindles help in muscle coordination and muscle action efficiency

15. Touch • Free nerve endings- dendrites are primarily pain receptors • Sometimes touch, temperature, and muscles • Fibers swell at the end in response • Disc-shaped (merkel discs) endings- light-touch receptors in deep layers of epidermis • Meissner’s corpuscles- light-touch mechanoreceptors in dermal papillae • Egg-shaped capsules of connective tissue around a spiraled end of a dendrite • Great amounts in lips and fingertips • Sense quick touch, not sustained

16. Pacinian corpuscles- deep-pressure mechanoreceptor • Dendrites surrounded by layers of connective tissue • Respond to deep/firm pressure or vibration • Visible to the naked eye- 2 millimeters long • Hair nerve endings • Respond to change in hair position • Bare dendrites

17. TEMPERATURE • End-bulbs of Krause (Krause’s corpuscles) • Activate below 68 degrees F • Bulbous capsule surrounds the dendrite • Commonly found throughout the body in the dermis and lips, tongue, and conjunctiva of the eyes • Brushes of Ruffini (Ruffini cylinders/Ruffini’s Corpuscles) • Respond between 77 degrees and 113 degrees F • Found in dermis and subcutaneous tissue • Dendrite endings in flattened capsules • There are less then end-bulbs and are deeper in the tissue • Human body is less sensitive to heat than to cold