Papillary layer made up of areolar connective tissue

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Papillary layer Made up of areolar connective tissue proper Dermal papillae are finger-like projections that interface with the overlying epidermis and increase surface area for exchange of gases, nutrients, and waste products 63 Skin Structure Figure 5.1 Epidermis Hair shaft Dermis Reticular layer Papillary layer Hypodermis (superficial fascia) Dermal papillae Pore Subpapillary vascular plexus Appendages of skin Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Nervous structures Sensory nerve fiber Lamellar (Pacinian) corpuscle Hair follicle receptor (root hair plexus) Dermal vascular plexus Adipose tissue 64 Thick skin 65 The Two Regions of the Dermis Figure 5.5 Dermis (a) Light micrograph of thick skin identifying the extent of the dermis, (100 × ) (b) Papillary layer of dermis, SEM (570 × ) (c) Reticular layer of dermis, SEM (430 × ) 66
7/21/15 12 Dermis Papillary layer On the palms of the hands and the soles of the feet, dermal papillae lie atop larger mounds called dermal ridges which elevate overlying epidermis into epidermal ridges (friction ridges) which create finger prints 67 Friction ridges (a) Friction ridges of finger tip (SEM 20 × ) (b) Cleavage lines in the reticular dermis (c) Flexure lines of the hand Openings of sweat gland ducts Flexion creases on digit Flexion creases on the palm Dermal Modifications Figure 5.6 68 Dermis Reticular layer Makes up 80% of thickness of dermis Dense irregular connective tissue Thick bundles of interlacing collagen and elastic fibers give skin its stretch and recoil properties 69 Thick skin 70 Dermis Reticular layer cleavage lines Separations or less dense regions between the collagen bundles form the cleavage lines or tension lines in the reticular dermis of the skin over the entire body • The cleavage lines run longitudinally in the skin of the limbs and head and in circular patterns around the neck and trunk Knowledge of cleavage lines is important to surgeons; when possible it is best to cut parallel to cleavage lines 71 Friction ridges (a) Friction ridges of finger tip (SEM 20 × ) (b) Cleavage lines in the reticular dermis (c) Flexure lines of the hand Openings of sweat gland ducts Flexion creases on digit Flexion creases on the palm Dermal Modifications Figure 5.6 72
7/21/15 13 Dermis Reticular layer striae = stretch marks Extreme sustained stretching of the skin which can occur with obesity and pregnancy can tear the collagen in the in the reticular dermis resulting in linear patches on the skin called striae which are also known as stretch marks 73 Dermis Flexure lines Arise from the deep part of the dermis and result from the repeated folding of the skin such as in the palms of your hands and around joints e.g., at the wrist, fingers, and toes 74 Friction ridges (a) Friction ridges of finger tip (SEM 20 × ) (b) Cleavage lines in the reticular dermis (c) Flexure lines of the hand Openings of sweat gland ducts Flexion creases on digit Flexion creases on the palm Dermal Modifications Figure 5.6 75 Hypodermis

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