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Skin Structure
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Chapter 4Skin and Body Membranes
“The Dermis”
DermisDermisTwo layers
1. Papillary layer Projections called dermal papillae Pain receptors Capillary loops
2. Reticular layer Blood vessels Glands Nerve receptors
Skin StructureSkin Structure
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
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
Nerve ReceptorsNerve ReceptorsFree 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
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
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
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
Hair AnatomyHair Anatomy
Central medulla Cortex surrounds
medulla Cuticle on outside of
cortex
-Most heavily keratinized
Associated Hair StructuresAssociated Hair Structures
Hair follicle Dermal and epidermal
sheath surround hair root
Arrector pilli Smooth muscle Goose bumps
Sebaceous gland
Sweat gland
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
Nail StructuresNail Structures
Free edge Body Root of nail Eponychium –
proximal nail fold that projects onto the nail body