The Integumentary
System
The Skin and its Appendages
The Skin
Two main components
● Epidermis
● Dermis
● (Hypodermis)
Epidermis
Cells of the Epidermis
● Keratinocytes
● Melanocytes
● Dendritic Cells
(Langerhans cells)
Epidermis
Layers of the Epidermis
● Thick Skin
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Stratum Basale
Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum
● Thin Skin
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Absence of Stratum Lucidum
Epidermis
Layers of Epidermis
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Stratum Basale
(germinatum)
Single row of stem
cells
10-25%
melanocytes
very small amount
of tactile cells
Epidermis
Layers of the Epidermis
● Stratum Spinosum
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several cells thick
weblike intermediate filament
network
melanin granules and dendritic cells
present
Epidermis
Layers of the Epidermis
● Stratum Granulosum
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Keratinization Begins
Keratohyaline granules
Lamellar granules
Epidermis
Layers of the Epidermis
● Stratum Lucidum
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Only present in thick skin
2-3 rows of clear, flat, dead
keratinocytes
Epidermis
Layers of the Epidermis
● Stratum Corneum
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anucleate
20-30 cells thick
¾ of epidermis
high keratin content
thickened, glycoprotein covered plasma
membranes
loses 50k cells/min
Dermis
Composition
● Connective Tissue proper
● Rich nerve and vascular supply
● contains hair follicles, glands, and sensory receptors
Layers
● Papillary Layer
● Reticular Layer
Dermis
Papillary Layer
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Thin
areolar
highly vascularized
low density (great for
phagocytes)
Dermal papillae (form
friction ridges in thin
skin)
Dermis
Reticular layer
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80% of Dermis
dense irregular
connective tissue
blood vessel network
(cutaneous plexus)
cleaveage and flexure
lines
Appendages of the Skin
Hair and Hair Follicles
Nails
● Sweat Glands
○ Eccrine Glands
Apocrine Glands
Sebaceous (oil) Glands
Appendages of the Skin
Hair and Hair Follicles
● Structure of hair
● Structure of a hair follicle
● Types and growth of hair
● Hair thinning and baldness
Appendages of the skin
Structure of a hair (fig 5.5)
● Produced by hair follicles
● Conists primarily of dead keratinized cells
● cells contain hard keratin
Regions
● Shaft
● Root
Concentric Layers
● Medulla
● Cortex
● Cuticle
Appendages of the skin
Structure of a Hair Follicle (fig 5.5)
● Epithelium based
● Hair bulb
● Hair follicle receptor
● Hair papillae
● Peripheral connective tissue sheath
● Epithelial root sheath
Appendages of the Skin
Types and Growth of Hair
● Vellus Hair
● Terminal Hair
Appendages of the Skin
Hair Thinning and Baldness
● Alopecia
● True Baldness (Male Pattern)
Appendages of the Skin
Nails (fig 5.6)
● Scale-like modification of epidermis
● hard keratin
● free edge, nail plate, root
● nail bed
● nail matrix
● nail folds and cuticle
Appendages of the Skin
Sweat (Sudoriferous) Glands
●Eccrine (Merocrine) Sweat Glands
●Apocrine Sweat Glands
Appendages of the Skin
Sebaceous (Oil) Glands
● Simple branched alvolar glands
● secrete sebum
● holocrine type glands
● secrete into hair follicles and occasionally pores
Skin Functions
Protection
● Chemical Barriers
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acid mantle
● Physical Barriers
● Biological Barriers
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dendritic cells, macrophages, DNA
Skin Functions
Body Temperature Regulation
Heat Loss
● Vaodilation
● heat loss through sweat evaporation
Heat conservation
● Vasoconstriction
Skin Functions
Cutaneous Sensation
Skin Functions
Metabolic Functions
● Produces vitamin D precursor
● disarm cancer causing chemicals
● activate some steroid hormones
Skin Functions
Blood Resevoir
● 5% of total blood volume
Skin Functions
Excretion
● ammonia, uric acid, urea, salt, water.
Homeostatic Imbalances of Skin
Skin Cancer
● Basal Cell Carcinoma
● Squamous Cell Carcinoma
● Melanoma
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Asymmetry
Border Irregularity
Color
Diameter
Elevation
Study Guide
Will Post Wednesday