Ap integumentary Flashcards
Epidermis function
The epidermis is composed of layers (strata) of keratinocytes
Thick skin = five layers (palms of hands, soles of feet) Thin skin = four layers (everywhere else)
- Provides mechanical protection
- Prevents fluid loss
- Keeps microorganisms from invading the body
- 4 cell types
- 4 or 5 layers
layers of epidermis
Keratinocytes
- 90% of cells in the skin
- Originate in the S. basale and differentiate as they progress upwards.
- Differentiated cells produce keratin
- Tightly connected by specialized gap junctions called desmosomes
- Growth is controlled at least in part by epidermal growth factor (EGF)
Langerhans Cells
- Specialized macrophages
- Arise from bone marrow, migrate to epidermis (s. spinosum / s. granulosum)
- Recognize antigens and present them to lymphocytes for destruction
Merkel Cells
- Present at the epidermal – dermal junction
- Associated with a sensory nerve fiber
- Functions in touch reception
Melanocytes
- Present in the S. basale
- Synthesize a reddish-brown biochrome, melanin, and dispense it to keratinocytes through their dendrites
- Melanin: dispersed screen against the potentially harmful ultraviolet rays of the sun
Skin color depends on
–Amount of melanin produced by melanocytes
- Blood supply
- Freckles and pigmented moles are local accumulations of melanin
Disorders of melanocytes
Vitiligo:
- Occurs when melanocytes die or stop producing melanin
- Autoimmune condition
Albinism:
- Inherited genetic disorder with mutation in genes involved in melanin production
- Vision problems
•Describe the location and explain the purpose of mitosis in the epidermis.
Dermis
Dermal Organization
•Papillary layer
–Contains blood vessels, lymphatics, sensory nerves of epidermis
•Reticular layer
–Contains network of collagen and elastic fibers to resist tension
Papillary layer
Loose connective tissue
Highly vascular
Most sensory receptors for cutaneous senses are found here
Free nerve endings – for heat, cold, itch and pain
Encapsulated nerve endings like Meissner’s corpuscles (tactile corpuscle) for touch and pressure
Epidermal Ridges
•Interacts with the epidermis, forming “ridges” and “valleys”
thumb print
Reticular layer
About 80% of the dermis
Dense connective tissue with collagen and elastin
Also vascular
Lamellated corpuscle senses vibration / pressure touch
Stretch marks
- Caused by excessive stretching of the reticular layer
- Patterns of collagen and elastic fibers form lines of cleavage
The Subcutaneous Layer
hypodermis
- Stabilizes skins position against underlying organs and tissues
- Known as subcutaneous tissue or superficial fascia
•
•Consists of
–Lose connective tissue (WBC, mast cell)
–Adipose tissue
The Hypodermis
Functions of adipose tissue:
–energy reservoir
–thermal insulation
–hypodermic injections
Accessories of the Skin
- Hair, Nails
- Glands
- sweat glands (merocrine / eccrine, apocrine)
- ceruminous (wax) glands
- mammary (milk) glands
- sebaceous glands
Hair types
- Vellus hairs (peach fuzz)
- Terminal hairs (scalp, eyebrows)
Shed and grow according to hair growth cycle
- About 4 years for the scalp
- About 4 months for eyebrows
Hair Follicles
- Millions of hair follicles over the body
- Present everywhere except lip’s, palms, soles of feet parts of the external genitals and nipples
- Flexible epithelial structure
- Shaft – projection out of skin
- Hair formed from well nourished S. basale epithelial in matrix (growing)
Functions of Hair
- Body hair too thin to provide warmth
- Sensory functions
–alert us to parasites crawling on skin
–contraction of arrector pili muscle = goose bumps
- Scalp hair provides heat retention & sunburn cover
- Guard hairs & eyelashes prevent foreign objects from getting into nostrils, ear canals or eyes
Hair disorders
- Male pattern baldness
- Alopecia
- Hirsutism
- Tinea capitis
Nails
- Tightly packed keratinized cells
- Nail body
–visible portion pink due to underlying capillaries
–free edge appears white
•Nail root
–buried under skin layers
–lunule is white due to thickened S. basale
•Eponychium (cuticle)
–stratum corneum layer
Sweat Glands
•Humans have over 2.5 million sweat glands on the entire body surface
–Merocrine – located on palms of the hands, soles of the feat and forehead
–Apocrine – located in axillary and anogenital areas
Sweat Glands
Merocrine “sweat” glands
- Hypotonic solution of water, salt, wastes
- Function is to cool the body (also nervous)
Apocrine sweat glands
- Secrete fatty acids and proteins (in addition to eccrine secretion)
- Odor occurs when broken down by bacteria
- Function is unclear but may be related to phermones
Specialized apocrine glands
Ceruminous
- Found only in external ear canal
- Secretion combines with sebum and dead epithelial cells to form earwax (cerumen)
Mammary
- Develop only during pregnancy and lactation
- Secrete milk which is released by ducts at nipple
Sebaceous (oil) glands
- Secretary portion in the dermis
- Found all over the body except palms of the hands and soles of feet
- Most open onto hair shafts
- Secrete sebum, a combination of cholesterol, proteins, fats & salts
–keeps hair and skin soft & pliable
–inhibits growth of bacteria & fungi
summary glands
Functions of the Integument
- Protection (tough, dry, acid mantle, water barrier, UV barrier)
- Thermoregulation
- Excretion
- Sensory functions
- Vitamin D synthesis
- Immune response
Protection
•Chemical barrier
–Skin secretions (sweat and sebum) “acid mantle”
–melanin
•Biological barrier
–Langerhans cells
–Dermal macrophages
•Physical barrier
–Hair
–Nails
–Epidermis
Injury and repair
- Regenerates easily
- Regeneration process includes formation of
–Scab
–Granulation tissue
–Scar tissue
Thermoregulation
- Perspiration lowers body temperature
- 500mL = insensible loss
- Up to 12L per day with heavy exercise, etc
- Adjustable flow of blood to the body surface
–Dilation = heat loss
–Constriction = heat conservation
Excretion
•Sweat consists mostly water plus:
–sodium and chloride
–potassium
–calcium
–magnesium
•Also has metabolic waste products such as lactic acid, urea, uric acid, and ammonia
sensory function
breeze
light touch
heat/cold
pressure/vibration
Vitamin D synthesis
- Sunlight activates a precursor to vitamin D
- Enzymes in the liver and kidneys transform that molecule into calcitriol (most active form of vitamin D)
- Necessary vitamin for absorption of calcium from food in the gastrointestinal tract
Immune response
- Langerhans cells
- Keratinocytes produce an array of cytokines (IL-1, IL-3, IL-6, IL-8, and GM-CSF) including growth factors for T cells
- Rich vascular and lymphatic environment
summary : function of integumentary system
Pathophysiology of Integument
- Aging
- Wear and tear
- Infections
- Autoimmune diseases
- Burns
- Cancer
Changes in the Epidermis
- Blister: A collection of fluid below or within the epidermis
- Callus: Thickening of an area of epidermis
- Hives: A very itchy eruption of the skin, usually the result of an allergy
Acne Vulgaris
•Common chronic disorder of sebaceous glands
–Adolescents ( hormonal variations, sebaceous gland)
–Usually self-limiting
•Pathogenesis
–Increased sebum production
•Regulated by androgens
–Retention hyperkeratosis
•Increased follicular keratinization resulting in the obstruction of the outflow of the pilosebaceous unit
–Presence of Propionibacterium acnes
- Bacterial lipolysis of sebum triglycerides to free fatty acids
- Irritation, comedones and inflammation
- Classification: Inflammatory and non-inflammatory
–Cystic acne: potential for scarring
•Complicating factors: Drugs & hormones, physical trauma, menstrual cycle, cosmetics, environmental factors
•
Skin Infection - Verracue(Warts)
- Caused by a virus, usually HPV
- Makes epidermal cells divide abnormally
- Transmission of disease usually involves direct contact
- Most common on the hands and feet
