Transcript The Integumentary System

The Integumentary System
I. Functions:
A. Protection
B. Temperature regulation
C. Excretion
D. Vitamin D synthesis
(calcitriol)
E. Sensation
II. Anatomy of the skin
A. Three regions
1. Epidermis (surface coat)
stratified epithelium
2. Dermis (bulk of the skin)
dense irregular connective
3. Hypodermis (subcutaneous
layer)
loose conn tissue, adipose
B. Layers of Epidermis
1. Stratum Corneum- superficial
keratin (hard, H2O insoluble
protein)
keratinocytes originate deep
(can become dandruff, callus)
2. Stratum Lucidum
only in “thick” skin
3. Stratum granulosum- keratinocytes
die
4. Stratum spinosum - Langerhans
cells
5. Stratum basale
- deep layer near dermis
- keratinocyte division, melanocytes
C. Cells of the Epidermis
1. Keratinocytes (90% of epidermal
cells)
2. Melanocytes- (2-3% of cells)
- brown skin pigment aids in UV
light absorption
- can increase /decrease
production
3. Langerhans cells - <1% cells, immune
4. Merkel cell - touch sensation
D. Dermis layer of the skin
1. Composition:
Gel matrix (hydrated)fibers:collagen, elastin
Cells: Fibroblasts
Macrophages
Leukocytes, mast cells
(heparin)
2. Layers of the Dermis:
a. Papillary layer(boundary)
- areolar tissue
- free nerve endings, papilla
(fingerprints)
- exchange of materials, attachment
b. Reticular layer- tough dense
irregular tissue
- striae & flexure lines
E. Subcutaneous Layer
1. Composition
- Loose connective tissue
soft gel (water + collagen),
elastin, fewer fibers than dermis
- Fat (adipose)
variable amount
cushions, skin contours,
insulator, energy depot
F. Skin derivatives
1. Sweat glands (sudoriferous)
eccrine- thermoregulation
apocrine- associated with hair
follicle
2.Sebaceous gland (oil)
ubiquitous
empties into hair follicle,skin
3. Hair
Column of keratinized cells
epidermal cells of follicle
extends into the dermis
growth /rest activity is cyclical
- vellus vs. terminal
Hair loss, Alopecia
arrector pili- smooth muscle
4. Nails (fingers, toes)
Analogous to hair
- keratin in stratum corneum
but not melanocytes
Protective Function
Skin Color (pigments):
1. Melanin (yellow-brown-black)
2. Carotene (yellow- orange)
- accumulates in corneum
3. Hemoglobin (red)
erythema vs. cyanosis
Influenced by blood flow, liver
(jaundice)
Aging changes to Integument
I. Aging vs. Abnormal changes
A. Effects of Sunlight on
epidermis - DNA damage
- keratinocytes irregular
- melanocytes less evenly
distributed
- decreased Langerhans cell
number
Warren (1991) no difference
until after age 45, more wrinkles,
less elasticity with > 12 hr /wk
for previous yr
B. Sunlight effects on Dermis:
- increase number but irregular
elastin fibers (shape/ arrangement)
elastosis
- blood vessels decrease
CLASS ACTIVITY
Many tanning salons claim to use
the longer”safe” wavelengths of UV
light (UVA). Based on the slide I will
show discuss the validity of this
claim:
1.List the potential side of effects
of UVA vs,UVB light.
2. Groups vote as to which is
more dangerous.
UVA ( tanning salon)
(UVA weaker)
vs. UVB (sunburn)
more intense burn
more penetrating
(more reaches earth)
dermis- collagen
epidermis
blood vessels
melanin
immune
cataracts,retina
C. Neoplastic skin conditions
1. Uncontrolled cell production
- benign or malignant
2. Skin cancers: basal cell
squamous cell, malignant melanoma
Asymmetry
Color
Border
Diameter
2. Due to several factors:
- decreased inflammatory
response, melanin, Langerhans,
removal of harmful substances,
increased cell irregularity
- all of these also related to sunlight
exposure
D. Other Preventable Aging effects
1. Effects of prolonged pressure
(i.e. bedridden)
- Bedsores (decubitus ulcers)
decreased blood flow + thinning
of subcutaneous fat
II. Aging changes
A. Epidermis
1. More permeable corneum
2. Keratinocytes more
variable
-
Strength of attachment,
spacing of keratinocytes
Rate of production
3. Melanocytes
- uneven distribution (age spots)
- reduced production of melanin
- higher risk for sunburn and skin
cancer due to sun exposure
4. Langerhans cells
- numbers
, allergic response
5. Hair
-
follicles
-
number of follicles inactive
stage,thinner, made slower
(related to hormone changes)
- air pockets, melanin( graying not
chronological age)
- decreased sebum
6. Nails
-
in growth (50%)
-
reduced blood flow to extremities
(toes)
- more susceptible to injury, fungal
infections, longer to repair
B. Aging on Dermis
1. Collagen fibers
- decrease in amount
- cross-linkages (stiffer, less
resisting to pulling forces)
in time cross links decrease, then
increased skin tears
2. Elastin fibers
- less well documented
- thicker,clumped, stiffer
- reduced ability to recoil
- some calcification
- looser covering that hangs
(1,2 due to fibroblast deficiency)
3. Immunity decline
- WBC, mast cells, macrophages
decline
- reduced heparin (less vessel
formation)
4. Mucopolysaccharides
- reduced water binding
(shape, reduced movement of molecules)
5. Blood vessels
- decrease number
- increased thickness of basement
membrane of endothelial cells
slower delivery of nutrients,
removal of wastes, decline of other
skin structures
skin pallor, thermoregulation
6. Sweat glands
- decreased # eccrine
(except in scalp)
- reduced threshold for sweating
- decrease in apocrine secretion
( one positive!)
7. Sebaceous glands
- no change #, increase in size but
decrease sebum production
8. Sensory neurons
- no change in pain or touch
receptors in hair follicles
- other touch/pressure receptors
- decreased sensory input from
fingers, hands, areas with little hair
Increase Risk of Vit D deficiency ( Ca2+):
Vit D (inactive form) synthesis in
epidermis
blood flow to bring cholesterol
precursors
ability to convert (> light for same result)
ability to activate to calcitriol (kidney)
ability to digest milk products
outdoor activity
C. Aging of Subcutaneous Layer
- ? Loose connective tissue
-
subcutaneous fat, not total body
fat
(sagging, loose skin appearance
translucent skin appearance)
Wrinkles, liver spot treatment
tretinoin (Retin-A)
increased thickness epidermis
increased turnover stratum corneum
decreased #,size melanocytes
increase in collagen, elastin
dermal vessel dilation
regression precancerous lesions
RETIN-A: TOO GOOD TO BE TRUE?
- redness, peeling, blistering,
swelling
- increased sun sensitivity
- 92% of cases skin inflammation
- no long term studies- hairless,
albino mice accelerated tumorigenic
potential of UV radiation
- interaction with abrasives