Chapter 5 - Integumentary Flashcards
Dermatology
Study and treatment of integumentary system: the skin (integument), hair, nails, and cutaneous glands
Skin is the body’s _________ organ.
largest
The Layers of Skin Plus a Nearby Layer
- Epidermis: epithelium of skin
- Dermis: connective tissue of skin
- Hypodermis: connective tissue just underneath skin
Thick Skin
- Palms of hands, front of fingers, soles of feet, bottom of toes
- Hairless, no sebaceous/oil glands but does sweat
- Adaptive for high friction
Thin Skin
- Covers most of body
- Hairy, has both sebaceous oil glands and sweat glands
Functions of Skin
- Resistance to trauma & infection
- Water retention
- Sensation
- Vitamin D synthesis
- Thermoregulation
- Nonverbal communication
Epidermis
- Keratinized stratified squamous epitehlium
- Avascular (nutrients diffuse from deeper connective tissue)
- Sparse nerve endings
Cells of the Epidermis
- Stem cells
- Keratinocytes
- Melanocytes
- Tactile (Merkel) cells
- Dendritic (Langerhans) cells
Stem Cells
- Divide and produce keratinocytes
- Only in stratum basale
Keratinocytes
- Synthesize keratin
- Vast majority of epidermal cells (found in many layers)
Melanocytes
- Make melanin (brown to black pigment)
- Melanin is taken up by keratinocytes and used to protect their DNA from UV radiation
- Found in stratum basale
Tactile (Merkel) Cell
- Touch receptors that join with nerves
- Only found in stratum basale
Dendritic (Langerhans) Cell
- Immune cells, guard against toxins/microbes/pathogens
- Found in stratum spinosum, stratum granulosum
Layers of the Epidermis
- Stratum Corneum - layers of dead, scaly cells
- Stratum Lucidum - only in thick skin, no organelles
- Stratum Granulosum - cells have dark granules
- Stratum Spinosum - several layers of cells
- Stratum Basale - one cell thick, varied cell types
Dermis
- Rich in collagen fiber
- Large blood supply
- Cutaneous glands
- Hair follicles
- Piloerector muscles
- Nail roots
Layers of the Dermis
- Papillary layer
2. Reticular layer
Papillary Layer of Dermis
- Superficial, thin layer
- Areolar tissue
- Rich in blood vessels
Reticular Layer of Dermis
- Deep, thick layer
- Dense irregular connective tissue
- Striae (stretch marks): stretching of the dermal collagen
Hypodermis
- Not a true layer of the skin
- Located below the dermis
- Contains adipose (subcutaneous fat) and areolar tissue
Functions of Hypodermis
- Pads body
- Binds skin to underlying tissues
- Energy reservoir
- Thermoregulation
Skin Color Components
- Melanin
- Hemoglobin
- Carotene
Melanin
- Eumelanin - brownish black
- Pheomelanin - reddish yellow
- Across individuals, skin tones vary due to type and distribution of melanin (not number of melanocytes)
Hemoglobin
red pigment of blood
Carotene
- Yellow orange
- Concentrates in stratum corneum
Diagnostic Skin Colors
- Cyanosis
- Erythema
- Pallor
- Albinism
- Jaundice
- Hematoma
Cyanosis
Blue skin tone due to lack of oxygen
Erythema
Redness of skin due to increased blood flow
Pallor
Pale or ashen tone of skin due to reduced blood flow
Albinism
White skin/hair/irises due to genetic lack of melanin
Jaundice
Yellow skin tone due to atypical liver function/bilirubin
Hematoma
Bruise
Skin Markings
- Friction ridges of fingertips
- Flexion lines (creases)
- Freckles
- Mole (nevus)
- Hemangiomas (birthmarks)
Friction Ridges of Fingertips
- Aid in sensitivity to texture and ability to grasp
- Cause fingerprint pattern
Flexion Lines
- Creases in skin
- Where skin near joint attaches to deeper tissue
Freckles
- Flat, melanized patches
- Vary with hereditary and UV exposure
Mole (nevus)
- Elevated patch of melanized skin
- “Beauty marks”
Hemangiomas (birthmarks)
- Discolored skin
- Caused by benign tumors of capillaries
Hair
- aka “pilus” (“pili” - plural)
- Accessory organ of the skin
- Fliament of keratinized cells
- Grows from a tube called a hair follicle
- Grows on most thin skin (exceptions: lips, nipples, parts of genitals, distal segments of fingers)
Types of Hair
- Lanugo
- Vellus
- Terminal
Lanugo
Fine, downy, unpigmented hair of fetus
Vellus
- Fine, unpigmented
- Two-thirds hair of women
- One-tenth hair of men
- All hair of children except eyebrows, eyelashes, & scalp
Terminal Hair
- Coarse, pigmented
- Eyebrows, eyelashes, & scalp
- After puberty: axillary, male facial hair, pubic, some hair on trunk and limbs
Function of Hair of the Torso and Limbs
Vestigial, but serves a sensory purpose as in detection of small insects crawling on the skin
Function of Scalp Hair
Heat retention, protection from sun
Function of Beard, Pubic, & Axillary Hair
Advertises sexual maturity; associated with apocrine scent glands in these areas and modulates the dispersal of sexual scents from these glands
Function of Guard Hairs (vibrissae)
Help keep foreign objects out of nostrils and auditory canal; eyelashes help keep debris from eyes
Function of Eyebrows
Enhance facial expression, may reduce glare of sun and help keep forehead perspiration from eyes
Three Zones Along Length of Hair
- Shaft - portion above skin’s surface, dead tissue
- Root - remainder of hair within follicle, dead tissue
- Bulb - swelling at base where hair originates in dermis, dermal papilla provides nutrition, hair matrix is the growth center (mitosis)
Hair Follicle
- Diagonal tube extending in dermis or as deep as hypodermis
- Two layers: Epithelial root sheath (inner layer) & Connective tissue root sheath (derived from dermis)
- Hair receptors: nerve fibers that respond to hair’s movement
- Piloerector muscle (arrector pili): smooth muscle that casues “goose bumps”
Nails
- Derivatives of stratum corneum
- Composed of very thin, dead, scaly cells with parallel rows of keratin
- Primates have flat nails as opposed to claws - easier manipulation
Structures of the Nail
- Nail plate (free edge, nail body, nail root)
- Nail fold & nail groove
- Nail bed (hyponychium - epidermis of nail bed, nail matrix, lunule, eponychium - cuticle)
Types of Cutaneous Glands
- Sudoriferous (sweat) glands (apocrine & merocrine)
- Sebaceous glands
- Ceruminous glands
- Mammary glands
Types of Sudoriferous Glands
- Apocrine glands
2. Merocrine glands
Apocrine Glands
- Type of sudoriferous gland
- Found in groin, anal, axilla, areola, and beard regions
- Duct opens into hair follicle
- Produce sweat with many fatty acids (bacterial metabolism of fatty acids causes odor)
- Respond to stress & sexual stimulation
- Develop in puberty
- Believed to secrete pheromones
Merocrine Glands
- Type of sudoriferous gland
- Numerous, widespread, especially abundant on palms, soles, & forehead
- Simple ducts lead to pores at skin surface
- Produce watery perspiration to cool body (also contains some wastes found in urine)
- Myoepithelial cells - contractile cells that squeeze sweat up the ducts
Sebaceous Glands
- Produce oily secretion called sebum
- Usually open to hair follicle
- Holocrine secretion
- Keep skin & hair from becoming brittle
Ceruminous Glands
- Found in auditory canal
- Produce cerumen (earwax) - combination of sebum & dead skin cells
- Keeps eardrum pliable, waterproofs canal, kills bacteria, and coats guard hair
Mammary Glands
- Produce milk
- Not synonymous with breasts; glands develop during pregnancy and lactation, otherwise scant
- Modified apocrine gland
Integumentary System Ageing
- Senescence
- hair turns grayer, thinner
- melanocyte stem cells die out
- Mitosis slows down
- dead hairs not replaced
- atrophy of sebaceous glands
- skin becomes thinner, more translucent
- Skin and Blood Supply
- fewer and more fragile vessels
- rosacea (due to dilated blood vessels)
- increased bruising
- Thermoregulation
- vulnerability to hypothermia and heat stroke
Skin Cancer
- Induced by UV rays
- Elderly and fair-skinned most common
- 3 types: basal cell carcinoma, squamous cell carcinoma, malignant melanoma
Basal Cell Carcinoma
- Most common skin cancer
- Least dangerous
- Hardly metastasizes
- Arises in stratum basale and invades dermis
Squamous Cell Carcinoma
- Arises from keratinocytes of stratum spinosum
- Can metastasize to lymph nodes
- Can be lethal
Melanoma
- Most deadly, but only 5% of all skin cancer cases
- Arises from melanocyte of existing mole
- Metastasizes quickly and often fatal if not treated quickly
Burns
- Leading cause of accidental death
- Death primarily from:
- fluid loss
- infection
- toxic effects of eschar (dead tissue)
Characteristics of 1st Degree Burn
- Partial-thickness burn
- Only affects epidermis
- Usually localized
- Redness, slight edema, and pain
- E.g. sunburn
Characteristics of 2nd Degree Burn
- Partial-thickness burn
- Affect epidermis and part of dermis
- Red, tan, or white
- Blistered and painful
- May damage hair folicles, nerve endings, and cutaneous glands
- E.g. severe sunburns and scalds
Characteristics of 3rd Degree Burn
- Full-thickness burn
- Epidermis and dermis completely destroyed
- Contracture and disfigurement can result
