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EXSC 223: Exam 2
connective tissue functions
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1. Bind and support
2. protection
3. Insulation
4. Transportation of substances/heat
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Properties of connective tissue
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1. common origin (Mesenchyme)
2. extracellular matrix (majority is non-cellular)
3. degrees of vascularity (no uniformity)
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structural elements of connective tissue
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1. ground substance
2. fibers
3. cells
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ground substance
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Interstitial fluid between the cells; allows for diffusion between blood vessels and cells; Glycosaminoglycan (GAG), proteoglycan; cell adhesion proteins (laminin)
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collagen fibers
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most abundant
very tough tensile strength
tropocollagen activates collagen & creates cross-link to make tough like in tendons and ligaments
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elastic fibers
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proteins that stretch and give
found where elasticity is needed (skin, lungs, blood vessels)
contains a little bit of collagen
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reticular fibers
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delicate, fine collagenous fibers
supports soft tissue around organs
found in lymphatic system organs (spleen)
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cleavage lines
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found in reticular layer of Dermis
collagen fibers arranged in bundles
where incisions are made (parallel)
fibers run in a direction that makes flexion of joints easy
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sweat glands
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eccrine, appocrine, sebaceous
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eccrine glands
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most abundant
function: thermoregulation; secretes sweat (mix of hypotonic blood, 99% H2O, NaCl, % waste)
controlled by sympathetic nervous system
can adapt to exercise demands and routines
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appocrine glands
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Location: axilary and anogenital
Function: secretes sweat mix of H2O & fat/oil
creates b.o. when oil breaks down
ducts empty into hair follicles
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sebaceous glands
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oil glands that puke sebum by holocrine
stimulated by sex hormones and steroids.
Located everywhere but palms and soles
cells die when they rupture
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sebum
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secreted by sebaceous glands
contains lipids and cell fragments
function: lubrication, slows H2O loss in skin, brevets hair brittleness, bacterial function
-stimulated by androgens
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acne
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develops when hair follicles become plugged with sebum and when bacteria causes inflammation
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Function of skin
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protection, body temp regulation, cutaneous sensation, metabolic function (chemical and vid D), blood reservoir, secretion
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cells in epidermis
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keratinocytes, Langerhans, merkel cells, melanocytes
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keratinocytes
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tough fibrous protein
most abundant
produce keratin
connected by desmosomes
eventually rise up to higher levels in skin
dead at surface (turn over 25-45 days)
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Langerhans
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resident macrophage (WBC in skin but not blood)
activates immune system
activated when bruised or injured
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merkel cells
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located at epidermal-dermal junction
associated with sensory nerve endings
receptor for touch
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melanocytes
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synthesize melanin
found in deepest layers
sectretes melanin --keratinocytes pick up melanin
melanin blocks UV light that damages DNA and minimizes damage to skin
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stratum basale
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highly mitotically active cells
produces lots of protein
close to nutrients supply
includes keratinocytes, kernel cells, and melanocytes
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stratum spinosum
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thickest layer
binding site of keratinocytes to blood supply
flat irregular shaped keratinocytes
desmosome attachements
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stratum cornaum
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20-30 layers thick
very thin flat cells
dead cells
glycolipids are between cells to keep water out of body by releasing oil (sebaceous glands)
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stratum lucidum
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1-5 layers thick
only in bottom of feet and palms
between granulosum and cornaum
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Dermis
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Connective tissue proper
2 layers -papillary and reticular
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papillary layer of dermis
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adjacent to epidermis
20% of dermis
loose ariolar connective tissue
ridges between epidermis and papillary increase the surface area for friction and allow epidermis to stay attached to dermis --forms fingerprints
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reticular layer of dermis
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80% of dermis = thickest layer
dense irregular connective tissue
no distinct pattern
lots of fibers and little open space
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which layer of the epidermis is the best nourished?
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stratum basale
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outermost layer of hair shaft
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cuticle
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what do eccrine glans help with?
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thermoregulation
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which cell produces color for hair and skin?
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melanocytes
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Hair stages
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terminal -long hair, thick, coarse
vellus -peach fuzz, very fine, short, not growing
--vellus can be activated and grow and then regress back to a vellus hair
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alopecia
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hair thinning
more hairs entering vellus phase than terminal
has a variety of causes
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baldness
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genetically determines (maternal)
male pattern baldness caused by follicular response to DHT
---DHT binds to receptor
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basal cell carcinoma
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least malignant
stratum basal cells proliferate and invades dermis
sun exposed areas are most common
pit/ulcers in center
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squamous cell carcinoma
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keratinocytes of the spinosum
ulceration-ulcers can be dark
grows rapidly, metastasizes, if caught early-good outcome
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melanoma
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most dangerous/deadly
difficult to treat
chemo resistant
affects the melanocytes
by the time it is visible, it has already metastasized
1/3 are from pre-existing moles
dark color
can move anywhere in the body and grow
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ABCD rule
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Asymmetry
Boarder irregularity
Color
Diameter -larger than 6 mm
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1st degree burns
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only epidermis is damaged
localized redness, swelling, pain
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2nd degree burns
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epidermis and upper dermis is damaged
blisters
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3rd degree burns
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complete destruction of epidermis and dermis
burned area is white/gray/red/black
no initial pain or adema
hydration most important within first 24 hours
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Rule of nines
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...
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Burns are critical if:
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over 25% of body has 2nd degree
over 10% has 3rd degree
3rd degree on face, hands, or feet
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Hyaline cartilage
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most abundant
provides flexible support
-articular surfaces of joints (long bones)
-rib cage
-bronchial tubes
secretes ground substance for lubrication
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elastic cartilage
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specialized hyaline
contains elastic fibers
-earlobes and epiglottis
withstands repeated stretching
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fibrocartilage
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compressible with high tensile strength
-pubic symphasis
-meniscus
-intervertebral discs
tough padding
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appositional cartilage growth
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how cartilage mostly grows
chondroblasts secrete new matrix on external force
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