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CH. 5 Integumentary system

Terms in this set (27)

Skin
largest organ in the body
-two layers, epidermis and dermis
Functions of skin
Protection, sensory reception, body temperature regulation, Production of vitamin D, Excretion
Epidermis
Contains keratinized stratified squamous.
Four main cell types
- Keratinocytes
- Melanocytes
- Tactile epithelial cells
-Dendritic cells
Keratinocytes
most abundant cell type in epidermis
•Arise from deepest layer of epidermis•
Produce keratin, a tough fibrous protein•
Keratinocytes are dead at skin's surface
Layers of epidermis
Stratum basale
Stratum spinosum
Stratum granulosum
•Stratum lucidum (only in thick skin)
•Stratum corneum
Stratum basale
•Deepest layer of epidermis
•Attached to underlying dermis
•Cells actively divide
•Stratum basale contains
•Tactile epithelial cells—associated with sensory nerve ending
•Melanocytes—secrete the pigment melanin
Stratum spinosum "Spiny layer"
Stratum spinosum
appearance caused by artifacts of histological preparation
•Contains thick bundles of intermediate filaments (tonofilaments)
•Resist tension
•Among the keratinocytes are star-shaped dendritic cells
•Are a type of macrophage
•Function in immune system
Stratum granulosum
Consists of a few layers of keratinocytes
•Keratinocytes contain•Keratohyaline granules—help form keratin•Lamellar granules—contain waterproofing glycolipid
•Above stratum granulosum
•Cells are too far from dermal capillaries to receive nourishment
Stratum lucidum (clear layer)
•Occurs only in thick skin
•Locations of thick skin—palms and soles
•Composed of a few rows of flat, dead keratinocytes
Stratum corneum (horny layer)
Thick layer of dead keratinocytes and thickened plasma membranes
•Protects skin against abrasion and penetration
Dermis
Second major region of the skin
•Strong, flexible connective tissue
•Richly supplied with blood vessels and nerves
•Has two layers
•Papillary dermis—includes dermal papillae
•Reticular dermis•Deeper layer—80% of thickness of dermis
Papillary dermis
Increase surface area for exchange of gases, nutrients, and wastes
•Dermal papillae lie on dermal ridges
•Push epidermis into Epidermal ridges
•Cause of fingerprints
•Increase gripping ability of hands and feet
Reticular dermis
Accounts for 80% of dermal thickness
•Dense irregular connective tissue
•Cleavage lines—separation between collagen fibers, important in surgical incision healing and scaring
•Flexure lines- Deep creases in palms, wrists, soles, fingers, and toes
•Has rich nerve and blood supply
•Blood vessels play important role in temperature regulation
Hypodermis
Hypodermis•Deep to the skin
•Also called superficial fascia
•Contains areolar and adipose connective tissue
•Anchors skin to underlying structures
•Helps insulate the body
•Site of subcutaneous fat (adipose)
•Has different distribution in males and females
Skin Color
•Determined by:- pigments - melanin, carotene, hemoglobin - genetics- blood circulation- thickness of stratum corneum
Melanin
- produced by melanocytesin epidermins
- responsible for hair and eye color
- provides protection against UV light
- amt. produced determined by genetics, UV light, & hormones
- freckles are accumulation of melanin
- albinism is absence of melanin
Nails
—scalelike modification of epidermis
•Made of hard keratin
Parts of the nail-
•Free edge
•Body
•Root
•Nail folds
•Eponychium—cuticle
Hair
Flexible strand of dead, keratinized cells
•Chief parts of a hair
•Root—embedded in the skin (dermis)
•Shaft—projects above skin's surface
Has three consecutive layers
Medulla—central core
•Cortex—surrounds medulla
•Cuticle—outermost layer
Parts of hair
•Hair follicles•Extend from epidermis into dermis
•Hair bulb•Deep, expanded end of the hair follicle
•Root plexus•Knot of sensory nerves around hair bulb
•Arrector pili- smooth muscle•Hair stands erect when arrector pilicontracts
Sebaceous Glands
Occur over entire body•Except palms and soles
•Secrete sebum—an oily substance•Simple alveolar glands•Most are associated with a hair follicle
•Functions of sebum•Collects dirt; softens and lubricates hair and skin
Sweat glands
widely distributed on body
•Sweat—is a blood filtrate •99% water with some salts•Contains traces of metabolic wastes
•About 2% urea
Two types of sweat glands
Eccrine gland (merocrine)•Most numerous—these produce true sweat
•Open into sweat pore
•Apocrine gland•Confined to axillary, anal, and genital areas
•Open into hair follicle
•Produce a special kind of sweat
•Musky odor—attracts a mate
•Signal information about a person's immune system
Burns
Classified by severity
•First-degree burn—only upper epidermis is damaged
•Second-degree burn—upper part of dermis is also damaged•Blisters appear•Skin heals with little scarring
•Third-degree burn•Damages entire thickness of skin (epidermis and Dermis), including nerve endings
•Burned area appears white, red, or blackened
Skin Cancer
•Most common cancer
•Mainly caused by UV light exposure
•Fair-skinned people more prone
•Prevented by limiting sun exposure and using sunscreen
•UVA rays cause tan and is associated with malignant melanomas
•UVB rays cause sunburns
•Sunscreens should block UVA and UVB rays
Skin Cancer types
Basal cell carcinoma•Least malignant and most common
•Squamous cell carcinoma•Arises from keratinocytes of stratum spinosum
•Melanoma•A cancer of melanocytes •The most dangerous type of skin cancer•Can metastasize
Fetal Skin
•Well formed after the fourth month
•At 5-6 months, the fetus is covered with lanugo(downy hairs)
•Fetal sebaceous glands produce vernix caseosa
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