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Biology ch 5
| Question | Answer |
|---|---|
| • Structures that are part of the integumentary system | – Skin – Hair – Nails – Glands |
| • Overview of Functions | – Protection – Sensation – Temperature regulation – Vitamin D production – Excretion – Immunity |
| Hypodermis | • Deep to skin • Consists of loose connective tissue with collagen and elastic fibers • Types of cells – Fibroblasts – Adipose cells – Macrophages • Also called – Subcutaneous tissue – Superficial fascia • Contains about one-h |
| Skin: | composed of dermis and epidermis |
| • Dermis | Gives structural strength. C.T. with many fibers, fibroblasts, macrophages. Some adipocytes and blood vessels. |
| • Dermis | • Contains nerves, blood vessels, hair follicles, smooth muscles, glands, and lymphatic vessels. • Sensory functions: pain, itch, tickle, temperature, touch, pressure, two-point discrimination. |
| Two Layers of the Dermis | •Two layers variable in thickness – Reticular – Papillary |
| – Reticular | Deep (inner) 4/5 Dense irregular C.T. Collagen and elastic fibers. In the picture see: some adipose, hair follicles, nerves, oil glands, ducts of sweat glands, heat sensors. |
| – Papillary | Superficial (outer) 1/5. Areolar with lots of elastic fibers. Dermal papillae, capillary beds. Fingerprints. Whorls of ridges. Touch receptors (Meissner's), free nerve endings sensing pain |
| • Cleavage (tension) lines | elastin and collagen fibers oriented in some directions more than in others • Important in surgery – If incision parallel to lines, there is less gapping, faster healing, less scar tissue |
| • Striae (stretch marks) occur | If skin is overstretched |
| – Keratinocytes | most cells. Produce keratin for strength |
| – Melanocytes | contribute to skin color. Melanin produced by these cells then transferred to keratinocytes. Same number of melanocytes in all people. |
| – Langerhans’ cells | part of the immune system |
| – Merkel’s cells | Detect light, touch, and superficial pressure |
| • Desquamate | cells of the deeper layers undergo mitosis; as they move toward the surface, older cells slough off |
| • Keratinization | as cells move outward through the layers, they fill with keratin, die and serve as a layer that resists abrasion and forms permeability layer |
| • Stratum basale (germinitivum) | Deepest portion of epidermis and single layer. High mitotic activity and cells become keratinized |
| • Stratum spinosum | Limited cell division. Desmosomes. Lamellar bodies and additional keratin fibers |
| • Stratum granulosum | Contains keratohyalin. In superficial layers nucleus and other organelles degenerate and cell dies |
| • Stratum lucidum | Thin, clear zone. Found only in palms and soles |
| • Stratum corneum | Most superficial and consists of cornified cells |
| • Thick skin | – Has all 5 epithelial strata – Found in areas subject to pressure or friction •Palms of hands, fingertips, soles of feet – Fingerprints and footprints. Papillae of underlying dermis in parallel rows |
| • Thin skin | – More flexible than thick skin – Covers rest of body |
| • Callus | Increase in number of layers in stratum corneum. When this occurs over a bony prominence, a corn forms. |
| • Blood circulating through the skin (Skin color/pigment) | –Imparts reddish hue and increases during blushing, anger, inflammation – Cyanosis • Thickness of stratum corneum |
| – Cyanosis | blue color caused by decrease in blood oxygen content |
| Accessory Skin Structures: Hair | • Found everywhere on human body except palms, soles, lips, nipples, parts of external genitalia, and distal segments of fingers and toes |
| • Hair Shaft | protrudes above skin surface |
| • Hair Root | located below surface; base of root is the hair bulb |
| •Hair has 3 concentric layers | – Medulla – Cortex – Cuticle |
| – Medulla | Central axis |
| – Cortex | Forms bulk of hair |
| – Cuticle | Forms hair surface |
| • Hair follicle | consists of dermal root sheath and epithelium root sheath • Internal part contains stratum basale that may remain after injury and supply a source of new epidermis |
| – Dermal root sheath: part of dermis that surrounds the epithelial root sheath | part of dermis that surrounds the epithelial root sheath |
| – Epithelial root sheath | with internal and external parts. |
| • Hair follicle | • When hairs are pulled out, internal part comes out and is visible as white bulb |
| • Hair bulb | – Internal matrix is source of hair – Dermis projects into bulb and is blood supply |
| – Growth Stages | cells added at base and hair elongates. Average rate is 0.3 mm/day |
| – Rest (Resting Stages) | follicle shortens and holds hair in place. Rest, then hair falls out of follicle. New hair begins. |
| – Regular hair loss means hair is being replaced. | hair is being replaced. |
| – Permanent hair loss: pattern baldness most common cause | pattern baldness most common cause |
| • Hair Color Cause by varying amounts and types of melanin. Melanin can be black-brown and red | by varying amounts and types of melanin. Melanin can be black-brown and red |
| • Muscles. Arrector pili. | Type of smooth muscle. – Muscle contraction causes hair to “stand on end” – Skin pushed up by movement of hair follicle |
| Accessory Skin Structures: Glands- Sebaceous (Oil) | • Holocrine (death of secretory cells) • Oily secretion • Prevents drying and may inhibit bacteria • Most empty into hair follicle – Exceptions: lips, meibomian glands of eyelids, genitalia |
| Accessory Skin Structures: Glands- Sudoriferous (Sweat) | • Two types traditionally called apocrine and merocrine, but apocrine may secrete in a merocrine or holocrine fashion. |
| Accessory Skin Structures: Glands- Sudoriferous (Sweat) | • Merocrine or eccrine. Most common. –Simple coiled tubular glands. –Open directly onto surface of skin. Have own pores. –Coiled part in dermis, duct exiting through epidermis. |
| • Merocrine or eccrine. Most common. | – Produce isotonic fluid (water and NaCl, but also excretory because sweat includes ammonia, urea, uric acid and lactic acid). As fluid moves through duct, NaCl is moved by active transport back into the body. Final product is hyposmotic (hypertonic). Swe |
| • Merocrine or eccrine. Most common. | – Numerous in palms and soles. Absent from margin of lips, labia minora, tips of penis, and clitoris. |
| • Apocrine | Active at puberty. – Compound coiled tubular, usually open into hair follicles superficial to opening of sebaceous gland. – Secretion: organic compounds that are odorless but, when acted upon by bacteria, may become odiferous. |
| • Apocrine | – Found in axillae, genitalia (external labia, scrotum), around anus. |
| Accessory Skin Structures | Glands- Ceruminous and Mammary |
| • Ceruminous glands | modified merocrine sweat glands, external auditory meatus. |
| – Earwax (cerumen) | Composed of a combination of sebum and secretion from ceruminous. |
| – Accessory Skin Structures Function | In combination with hairs, prevent dirt and insects from entry. Also keep eardrum supple. |
| • Mammary glands | modified apocrine sweat glands. Covered with reproductive chapter. |
| Accessory Skin Structures | Nails |
| • Anatomy of the Nails | Nail body Eponychium or cuticle Matrix and nail bed Nail root |
| – Nail body | stratum corneum |
| – Eponychium or cuticle | is corneum superficial to nail body, hyponychium is corneum beneath the free edge |
| – Matrix and nail bed | cells that give rise to the nail |
| – Nail root | extends |
| • Growth | – Grow continuously unlike hair – Fingernails grow 0.5-1.2 mm/day; faster than toenails |
| Skin Functions: Protection | • Against abrasion, sloughing off of bacteria as desquamation occurs. • Against microorganisms and other foreign substances. Glandular secretions bacteriostatic and skin contains cells of the immune system. • Melanin against UV radiation. |
| Skin Functions: Protection | • Hair on head is insulator and protection against light, and from abrasion. Eyebrows keep sweat out of the eyes; eyelashes protect eyes from foreign objects. Hair in nose and ear against dust, bugs, etc. • Nails protect ends of digits, self defense. |
| Skin Functions: Protection | • Acts as barrier to diffusion of water. |
| Skin Functions | Sensation and Temperature Regulation |
| • Sensation | Pressure, temperature, pain, heat, cold, touch, movement of hairs. |
| • Temperature Regulation: sweating and radiation. | – Sweat causes evaporative cooling. – Arterioles in dermis change diameter as temperature changes. More or less blood flows through the dermis. |
| Skin Functions: Vitamin D Production | • Begins here in skin; aids in Ca+2 absorption. |
| • Vitamin D (calcitriol): hormone. | – Stimulates uptake of Ca and PO4 from intestines – Promotes Ca and PO4 release from bones – Reduces Ca loss from kidneys. – Increases blood Ca and PO4 levels. |
| • Functions of Ca | – bone formation, growth, repair – clotting – nerve and muscle function. |
| • Functions of Ca | • 7-dehydrocholesterol converts to cholecalciferol when exposed to UV radiation. Cholecalciferol released to blood and modified in the liver and kidneys to form calcitriol (active vitamin D). |
| • Functions of Ca | • People in cold climates and those who cover the body can be deficient, but calcitriol can be absorbed through intestinal wall. |
| • Functions of Ca | – Sources: dairy, liver, egg yolks, supplements. |
| Skin Functions: Excretion | • Removal of waste products from the body. Sweat. Water, salt, urea, ammonia, uric acid. •Insignificant when compared with kidneys. |
| Burns • Classifications | – First-degree – Second-degree – Third-degree |
| • Skin Grafts | – Split skin – Artificial skin – Cadavers or pigs |
| The Rule of Nines | • Used to estimate amount of body that is burned. • Note differing proportions in adult and child. |
| Aging Effects | • Skin more easily damaged because epidermis thins and amount of collagen decreases • Skin infections more likely • Wrinkling occurs due to decrease in elastic fibers • Skin becomes drier |
| Aging Effects | • Decrease in blood supply causes poor ability to regulate body temperature • Functioning melanocytes decrease or increase; age spots •Sunlight ages skin more rapidly |
Created by:
Wendy Starks
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