Ch. 5 - Integumentary System Flashcards
What are the functions of the skin?
Thermoregulation, protection (env, antimicrobial), sensations, vit D synthesis, excretion/absorption
How does the skin perform thermoregulation?
lowers body temp via perspiration (heat released with sweat evaporation); vasodilation increases blood flow in dermis
raises temp via vasoconstriction of surface
What type of junctions allow for protection?
Tight cell junctions prevent entry of chemicals and bacterial invasion
How does the skin perform antimicrobial protection?
sweat contains antibacterial agents
macrophages (1) Langerhans initiate immune responses (2) Dermal macrophages engulf microbes
What kind of receptors does the skin contain?
tactile sensations (touch, pressure, vibration, tickling)
thermal sensations
pain
How does the synthesis of Vitamin D work?
enz from liver and kidneys modify activated molecule (from UV light) to produce calcitriol (an active form of vit D)
How does the skin absorb drugs?
non-polar drugs/molecules administered transcutaneously (patches and creams, e.g. corticosteroid)
What are the 3 main structures of the skin and what tissues do they comprise of?
Epidermis - keratinized strat squamous
Dermis - areolar & adipose CT, nervous, muscle
Hypodermis - areolar & adipose; not part of skin
What is the function of keratinocytes? Where are they located?
produce keratin; helps protect skin and underlying tissue from heat, microbes, chem and abrasion
contain lamellar granules that release lipids (waterproof sealant)
located in epidermis
What is the purpose of stem cells in the basal layer of the epidermis?
divide and differentiate into keratinocytes
What are melanocytes and where are they located?
produce melanin and transfer it to keratinocytes via exocytosis; located in basal layer of epidermis
What does melanin do?
Contributes to skin color and absorbs UV light, protecting keratinocytes from damage
What do Merkel cells do? (tactile epithelial)
make contact with tactile discs, transmit touch sensations
Name the 5 layers of epidermis
(stratum)
corneum, lucidum, granulosum, spinosum, basale
What cells are the stratum basale composed of? What is its function?
single row of cuboidal or columnar kcytes; attached by demosomes; attaches to basal lamina by hemidesmosomes
contain stem cells that continually divide + differentiate into kcytes
contain melanocytes
What cells is the stratum spinosum composed of? What is its function?
8-10 layers of keratinocytes held tgt by desmosomes; oxygen diffuses from dermis
most metabolically active; kcytes synthesize and fill up with keratin + melanin (from melanocytes)
What is the stratum granulosom composed of? What is its function?
3-5 layers of dying cells (undergoing apoptosis); between metabolically and active layers
contain lamellar granules that release lipid=-reach secretions (fill space b t dead sells of stratum G, L, C)
Where is the stratum lucidum present in? What is it composed of?
thick skin (fingertips, palms, soles))
3-5 layers of dead cells; contains large amounts of keratin (protection!)
What is the stratum corneum composed of? What is its function?
25-30 layers of tightly packed dead cells filled with keratin + surrounded by lipids
serves as barrier to injuries, heat, water, chem, microbes
**continuously shed
How do thin skin and thick skin differ?
THIN - covers whole body, lacks stratum lucidum, lacks epid ridges, fewer sweat glands + sensory receptors
THICK - palms + soles, distinct stratum L/C, lacks hair follicles and sebaceous glands (not sweat!)
What is keratinization and when does it occur?
replacement of cell contents with keratin; occurs as cells move close to skin surface;
What are the steps in keratinization?
- stem cells divide to produce kcytes
- as they push up towards surface of skin, they fill up with keratin
- as they move further from blood supply, they receive less nutrients and eventually die
What are keratinized cells and do they serve any function?
dead cells filled with keratin; protection
How is the process of keratinization controlled?
by epidermal growth factor (hormone) over ~4 weeks
What is the dermis composed of?
collagen and elastic fibers, fibroblasts, macrophages, adipose cells
What does the dermis contain?
hair follicles, glands, nerves, BV
What are the 2 regions of the dermis?
top 20% - papillary
bottom 80% - reticular
What does the papillary region of the dermis contain?
capillaries that supply epidermis
receptors for sensations
What is the papillary region of the dermis composed of?
areolar CT, thin collagen and fine elastic fibers
What is the function of dermal papillae on the dermis?
increase SA to provide better adhesion of epidermis to dermis
What does the epidermal ridge determine?
pattern of fingerprints; conforms to pattern of dermal papillae; increases friction
What does the reticular region of the dermis contain?
interlacing collagen and elastic fibers (strength + elasticity!)
packed with oil glands, sweat gland ducts, fat, hair follicles
What is the reticular region of the dermis composed of?
dense irregular CT (strength in all directions!), coarse elastic fibers
How do stretch marks occur?
dermal tears from extreme stretching
What are the advantages and disadvantages to UV light exposure?
+ : increases melanin production; melanin protects DNA by absorbing UV radiation
- : can increase cell damage, mutations, cancer
In tattoos, how do the pigments show up in the skin?
dermal macrophages engulf foreign pigments in dermis
How do abrasions and minor burns heal?
**not bleeding
- basal cells divide and migrate across wound
- bcells synthesize basement membrane along the way
- bcells differentiate into kcytes and the epidermis regenerates upwards
How can scar formation result?
when injury extends to the dermis and subcutaneous layer
What are the stages of deep wound healing?
- inflammatory (cleaning and prepping for repair)
2. repair (repair dermis + epidermis; scar tissue is formed)
Describe the inflammation phase of deep wound healing
- injured tissue cells secrete signalling molec
- molec dilate blood vessels (vasodilation)
- molec attract phagocytes via chemotaxis
- phagocytes squeeze out bt blood vessel endothelial cells (extravasation)
- phagocytes ingest bacteria/cell debris
- platelets form clot which prevents infection spread
What is chemotaxis?
moving towards higher concentration of chemicals
Describe the repair phase of deep wound healing
- blood clot forms
- BV reform
- fibroblasts synthesize scar tissue
- basal cells divide+migrate beneath scab towards each other
- epidermis regenerates upwards
- scab falls off as regenerating epidermis pushes up
What are the 3 common causes of skin cancer?
basal cell carcinoma, squamous cell carcinoma, malignant melanomas
How does basal cell carcinoma arise? What is its incidence?
arise from cells of stratum basale; 78% of all skin cancers –> benign tumour as it rarely metastasizes
How does squamous cell carcinoma occur? What is its incidence?
arise from keratinocytes; 20% of all skin cancers –> may or may not met
How does malignant melanoma arise?
arise from melanocytes; 2% of all skin cancers –> metastasize rapidly/life threatening
What should one observe for early detection of skin cancer?
ABCDE: asymmetry, border, colour, diameter, expanding
What are the risk factors for skin cancers?
Lighter skin type, increased sun exposure, family history, older age, immunosuppression
What is the difference between terminal hairs and vellus hairs?
TERMINAL - long, coarse, heavily pigmented (eyebrows, eyelashes, scalp at birth, axillary + pubic hair)
VELLUS - short, fine, pale that are barely visible to naked eye
What are the functions of hair?
prevents heat loss, decrease sunburn, touch receptors sense light touch
lashes protect eyes from debris, sweat, dirt
Describe the structure of hair
each hair is a column of dead, tightly-packed keratinized cells
shaft (above skin) and root (deep into dermis or hypodermis)
What do the hair shaft and root consist of?
3 layers of cells: medulla (2-3 layers of irregular cells), cortex, cuticle (single layer of flat keratinized cells)
What is the hair follicle and what does it consist of?
surrounds hair root
consists of 2 layers of cells: internal + external root sheaths and one layer of CT (dermal root sheath)
What is a hair bulb?
base of each hair follicle and root sheath
What are papilla and matrix in the hair responsible for?
PAPILLA: contains areolar CT and BV to nourish growing hair
MATRIX: surrounds papilla, germinal layer responsible for hair growth
What are parts of hair?
root, sheath, follicle, bulb, papilla, matrix
Describe the hair growth cycle
- Growth stage: matrix cells at hair base produce length; cells are keratinizing + differentiating; new cells added to base pushes out root of old hair
- Resting stage: matrix cells inactive, follicle atrophies; old hair falls out as growth stage begins again
What is a hair root plexus?
nerve ending surrounding bulb; detects hair movement
What is the arrector pili muscle?
smooth muscle in dermis attached to follicle; contracts with cold/emotion
What are sebaceous glands?
oil glands connected to hair follicles in dermis
holocrine glands produce sebum
What does sebum contain? What is its function?
contains cholesterol, proteins, fats, salts
moisten hairs, waterproofs + softens skin, inhibits bact/fungi growth
What causes acne?
inflammation of sebaceous glands cause by bact
What are the 2 types of sudoriferous glands?
both merocrine; released via exocytosis
- ECCRINE - duct empties at surface
- APPOCRINE - duct opens into hair follicle
Where are eccrine glands found? What is their function?
found in most areas of skin, especially forehead, palms, soles
regulate body temp via evaporative cooling
Where are apocrine glands found?
axillary and pubic regions
secretions more viscous; not involved with thermoregulation
What are ceruminous glands?
modified sebaceous glands that produce waxy secretion in ear canal
ducts open to surface or into sebaceous ducts
What is cerumen and its function?
earwax containing secretions of oil + wax glands; helps form sticky barrier to hinder entrance of foreign bodies
What is the structure of a nail?
plate of tightly packed, hard, keratinized epidermal cells
What are the parts of a nail?
- nail body (pink bc underlying capillaries)
- nail root (lunula white due to thickened epithelium)
- eponychium (cuticle; band of epidermis)
- nail matrix (germinal layer below nail root)
- hyponychium (secures nail to fingertip; thickened stratum corneum)
What is the function of nails?
protects fingertips, weapons!
