Download - Ch4 Dermis
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Chapter 4Skin and Body Membranes
“The Dermis”
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DermisDermisTwo layers
1. Papillary layer Projections called dermal papillae Pain receptors Capillary loops
2. Reticular layer Blood vessels Glands Nerve receptors
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Skin StructureSkin Structure
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Normal Skin Color DeterminantsNormal Skin Color DeterminantsMelanin
Yellow, brown or black pigments
Carotene Orange-yellow pigment from some
vegetables
Hemoglobin Red coloring from blood cells in dermis
capillaries
Oxygen content determines the extent of red coloring
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Appendages of the SkinAppendages of the Skin
Sebaceous glands
Produce oil
- Lubricant for skin
- Kills bacteria
Most with ducts that empty into hair follicles
Glands are activated at puberty
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Nerve ReceptorsNerve Receptors
Free nerve endings
• detect temp, mechanical stimuli (such as pressure), pain, & touch
Meissner’s corpuscles
• Tactile, light touch, found in abundance in fingertips, palms, soles, lips, tongue, face, genitals. In dermal papillae.
Pacinian corpuscles
• Deep, pressure, adaptive
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Appendages of the SkinAppendages of the Skin
Sweat glands
Widely distributed in skin
Two types
1. Eccrine
Open via duct to pore on skin surface
2. Apocrine
Ducts empty into hair follicles
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Sweat and Its FunctionSweat and Its FunctionComposition
Mostly water Some metabolic waste Fatty acids and proteins (apocrine only)
Function Helps dissipate excess heat Excretes waste products Acidic nature inhibits bacteria growth
Odor is from associated bacteria
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Appendages of the SkinAppendages of the Skin
Hair
Produced by hair bulb
Consists of hard keratinized epithelial cells
Melanocytes provide pigment for hair color Figure 4.7c
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Hair AnatomyHair Anatomy
Central medulla
Cortex surrounds medulla
Cuticle on outside of cortex
-Most heavily keratinized
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Associated Hair StructuresAssociated Hair Structures
Hair follicle
Dermal and epidermal sheath surround hair root
Arrector pilli
Smooth muscle
Goose bumps
Sebaceous gland
Sweat gland
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Appendages of the SkinAppendages of the Skin
Nails Scale-like modifications of the epidermis
- Heavily keratinized
Stratum basale extends beneath the nail bed
- Responsible for growth
Lack of pigment makes them colorless
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Nail StructuresNail Structures
Free edge
Body
Root of nail
Eponychium – proximal nail fold that projects onto the nail body