Chapter 5 - Chapter 5 - Introduction to the Integumentary...

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Chapter 5 - Introduction to the Integumentary System The integument is the largest system of the body 16% of body weight; 1.5 to 2 m 2 in area The integument is made up of two parts 1. Cutaneous membrane (skin) 2. Accessory structures a. The cutaneous membrane has two components i. Outer epidermis - superficial epithelium (epithelial tissues) ii. Inner dermis - connective tissues b. Connections Cardiovascular system - blood vessels in the dermis Nervous system - sensory receptors for pain, touch, and temperature Subcutaneous layer (superficial fascia or hypodermis ) - loose connective tissue located below dermis - location of hypodermic injections Functions of Skin i. Protects underlying tissues and organs ii. Excretes salts, water, and organic wastes (glands) iii. Maintains body temperature (insulation and evaporation) iv. Synthesizes vitamin D 3 v. Stores lipids vi. Detects touch, pressure, pain, and temperature A. Epidermis is avascular stratified squamous epithelium Nutrients and oxygen diffuse from capillaries in the dermis Cells of the Epidermis Keratinocytes - contain large amounts of keratin- the most abundant cells in the epidermis Thin Skin - covers most of the body & has 4 layers of keratinocytes Thick Skin - Structures of the Epidermis The five strata of keratinocytes in thick skin from basal lamina to free surface Stratum germinativum (Stratum Basale) Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum 1. Stratum Germinativum - the “germinative layer”; has many germinative (stem) cells/ basal cells Is attached to basal lamina by hemidesmosomes & forms a strong bond between epidermis & dermis Forms epidermal ridges (e.g., fingerprints) Dermal papillae (tiny mounds) - increase the area of basal lamina Specialized Cells of Stratum Germinativum i. Merkel cells - found in hairless skin and respond to touch (trigger nervous system) ii. Melanocytes - contain the pigment melanin; scattered throughout stratum germinativum 2. Stratum Spinosum - the “spiny layer”; produced by division of stratum germinativum 8 - 10 layers of keratinocytes bound by desmosomes; cells shrink until cytoskeletons stick out (spiny) Continue to divide, increasing thickness of epithelium; contain dendritic (Langerhans) cells , active in immune response c. Stratum Granulosum - the “grainy layer”; stops dividing, starts producing: 1. Keratin - a tough, fibrous protein that makes up hair and nails 2. Keratohyalin - dense granules with cross-link keratin fibers 1
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Cells of Stratum Granulosum - produce protein fibers; dehydrate and die Create tightly interlocked layer of keratin surrounded by keratohyalin d. Stratum Lucidum - the “clear layer”; found only in thick skin
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Chapter 5 - Chapter 5 - Introduction to the Integumentary...

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