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Chapter 60 Structure and Function of the Skin
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Functions of the Skin Prevents body fluids from leaving the body
Protects the body from potentially damaging environmental agents Serves as an area for heat exchange Provides protection against invading microorganisms
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Role of Receptors in the Skin
Relay the following sensations to the CNS for localization and discrimination: Pressure Temperature Pain
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Layers of the Skin Outer epidermis
Avascular layer composed of 4–5 layers of stratified squamous keratinized epithelial cells formed in the deepest layer of the epidermis These cells migrate to the skin surface to replace cells lost during normal shedding. Basement membrane Thin adhesive layer cementing the epidermis to the dermis Layer involved in blister formation
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Layers of the Skin (cont.)
Inner dermis Connective tissue layer that separates the epidermis from the underlying subcutaneous fat layer Contains blood vessels and nerve fibers that supply the epidermis
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Cells of the Epidermis Keratinocytes Melanocytes Merkel cells
Langerhans cells
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Papillary Dermis Definition
A thin, superficial layer that lies adjacent to the epidermis Composition Consists of collagen fibers and ground substance This layer is densely covered with conical projections called dermal papillae.
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Papillary Dermis (cont.)
Function Minimizes the separation of the dermis and the epidermis Nourishes the epidermal layers of the skin
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Reticular Dermis Definition
The thicker area of the dermis that forms the bulk of the dermal layer Composition Complex meshwork of three-dimensional collagen bundles interconnected with large elastic fibers and ground substance A viscid gel that is rich in mucopolysaccharides
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Question Which of the following is not found in the epidermis?
Keratinocytes Melanocytes Merkel cells Langerhans cells Blood vessels
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Answer Keratinocytes Melanocytes Merkel cells Langerhans cells
Blood vessels: Blood vessels are found in the dermal layer.
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Skin Appendages Hair Nails Sebaceous glands Eccrine glands
Apocrine glands
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Types of Sweat Glands Eccrine sweat glands
Simple tubular structures that originate in the dermis and open directly to the skin surface Numerous (several million) and vary in density Located over the entire body surface Transport sweat to the outer skin surface to regulate body temperature
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Types of Sweat Glands (cont.)
Apocrine sweat glands Less numerous than eccrine sweat glands Larger and located deep in the dermal layer Open through a hair follicle, even though a hair may not be present Found primarily in the axillae and groin
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Apocrine gland Hair papilla Sebaceous gland Arrector pili muscle
Which of the following structures would likely be present in a hair follicle in a man’s groin but not on the face? Apocrine gland Hair papilla Sebaceous gland Arrector pili muscle
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Apocrine gland
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Secretions of the Sebaceous Glands
Lipids, including triglycerides Cholesterol Wax
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Nails Definition Hardened keratinized plates Function
Protect the fingers and toes and enhance dexterity
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Immune Cells Found in the Dermis
Macrophages T cells Mast cells Fibroblasts
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Skin Rashes and Lesions
Macule Patch Papule Plaque Nodule Tumor Wheal
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Skin Rashes and Lesions (cont.)
Vesicle Bulla Pustule Blister Calluses Corns
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Pruritus or Itchy Sensation
Originates in free nerve endings in the skin Carried by small myelinated type C nerve fibers Itch and pain are antagonistic Causes Histamine Tryptase Opioids Neuropeptides Substance P Bile salts Bradykinin
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Xerosis Dry skin Dehydration of the stratum corneum
Aging skin will be dry due to a change in the composition of sebaceous gland secretions and a decrease in the secretion of moisture from the sweat glands. Moisturizing agents are the cornerstone of treatment for dry skin. Emollients Humectants Occlusives
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Dark Skin Variations Because of their skin color, dark-skinned persons are better protected against skin cancer, premature wrinkling, and aging of the skin that occurs with sun exposure. Problems Ashy skin Hypo- and hyperpigmentation
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Question Is the following statement true or false?
The pathology of itchy skin is well understood.
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Question False: The pathology of itchy skin is not well understood.
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Case study Explain the anatomic and functional differences between eccrine and apocrine glands. What autonomic nervous system controls the function of thermoregulation of the skin? How do goose bumps contribute to heat conservation? Describe the location of the blood plexuses in the skin. How is blood circulation to the skin involved in thermoregulation
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Case study Typical signs and symptoms of a fracture?
How does a hematoma form and what function it serve in the healing function? Describe the muscular and joint changes in immobilization?
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