Chapter 5 The Integumentary System and Body Membranes

CLASSIFICATION OF BODY MEMBRANES Classification of body membranes (Figure 5-1) Epithelial membranes—composed of epithelial tissue and an underlying layer of connective tissue Connective tissue membranes—composed largely of various types of connective tissue

CLASSIFICATION OF BODY MEMBRANES Epithelial membranes Cutaneous membrane—the skin Serous membranes—simple squamous epithelium on a connective tissue basement membrane Types Parietal—line walls of body cavities Visceral—cover organs found in body cavities Examples Pleura—parietal and visceral layers line walls of thoracic cavity and cover the lungs Peritoneum—parietal and visceral layers line walls of abdominal cavity and cover the organs in that cavity Diseases Pleurisy—inflammation of the serous membranes that line the chest cavity and cover the lungs Peritonitis—inflammation of the serous membranes in the abdominal cavity that line the walls and cover the abdominal organs

CLASSIFICATION OF BODY MEMBRANES Epithelial membranes (cont.) Mucous membranes Line body surfaces that open directly to the exterior Produce mucus, a thick secretion that keeps the membranes soft and moist

CLASSIFICATION OF BODY MEMBRANES Connective tissue membranes Do not contain epithelial components Produce a lubricant called synovial fluid Examples are the synovial membranes in the spaces between joints and in the lining of bursal sacs

THE SKIN Structure (Figure 5-2)—two primary layers called epidermis and dermis Epidermis Outermost and thinnest primary layer of skin Composed of several layers of stratified squamous epithelium Stratum germinativum—innermost layer of cells that continually reproduce; new cells move toward the surface As cells approach the surface, they are filled with a tough, waterproof protein called keratin; eventually cells flake off of body Stratum corneum—outermost layer of keratin-filled cells Skin pigment—produced by deepest epidermal layer; gives color to the skin The brown pigment melanin is produced by specialized cells in deepest epidermal layer Blisters—caused by breakdown of union between cells or primary layers of skin

THE SKIN Structure (cont.) Dermal-epidermal junction—specialized area between two primary skin layers Dermis Deeper and thicker of the two primary skin layers; composed largely of connective tissue Upper papillary layer of dermis characterized by parallel rows of tiny bumps called dermal papillae Ridges and grooves in dermis form pattern unique to each individual Basis of fingerprinting Improves grip for tool use and walking Deeper reticular layer of dermis filled with network of tough, interlacing, collagenous and stretchable elastic fibers Number of elastic fibers decreases with age and contributes to wrinkle formation Dermis also contains nerve endings, muscle fibers, hair follicles, sweat and sebaceous glands, and many blood vessels

THE SKIN Accessory structures of the skin Hair (Figures 5-5) Lanugo—soft hair of fetus and newborn Hair follicle—epidermal tubelike structure required for hair growth Hair papilla—structure from which hair growth begins Hair root—lies hidden in follicle Hair shaft—visible part of hair Arrector pili—specialized smooth muscle that produces “goose bumps” and causes hair to stand up straight

THE SKIN Accessory structures of the skin (cont.) Receptors (Figure 5-2) Specialized nerve endings—make it possible for skin to act as a sense organ Meissner’s corpuscle—capable of detecting light touch Pacinian corpuscle—capable of detecting pressure

THE SKIN Accessory structures of the skin (cont.) Nails (Figure 5-6) Produced by epidermal cells over terminal ends of fingers and toes Nail body—visible part of nail Root—lies in a groove; hidden by cuticle Lunula—crescent-shaped area nearest root Nail bed may change color with change in blood flow

THE SKIN Accessory structures of the skin (cont.) Skin glands—two types Sweat, or sudoriferous, glands Eccrine sweat glands Most numerous, important, and wide-spread of the sweat glands Produce perspiration or sweat, which flows out through pores on skin surface Function throughout life and assist in body heat regulation Apocrine sweat glands Found primarily in axilla and around genitalia Secrete a thicker secretion quite different from eccrine perspiration Breakdown of secretion by skin bacteria produces odor Sebaceous glands Secrete oil or sebum for hair and skin Level of secretion increases during adolescence Amount of secretion is regulated by sex hormones Sebum in sebaceous gland ducts may darken to form a blackhead

THE SKIN Skin cancer Functions of the skin Protection—first line of defense against: Infection by microbes Ultraviolet rays from sun Harmful chemicals Cuts and tears

THE SKIN Functions of the skin (cont.) Temperature regulation Skin can release almost 3000 calories of body heat per day Mechanisms of temperature regulation Regulation of sweat secretion Regulation of blood flow close to the body surface Sense organ activity Skin functions as an enormous sense organ Receptors serve as receivers for the body, keeping it informed of changes in its environment

THE SKIN Burns Treatment and recovery or survival depend on total area involved and severity or depth of the burn Body surface area is estimated using the “rule of nines” (Figure 5-8) in adults Body is divided into 11 areas of 9% each Additional 1% located around genitals

THE SKIN Burns (cont.) Classification of burns First-degree (partial-thickness) burns—only the surface layers of epidermis involved Second-degree (partial-thickness) burns—involve the deep epidermal layers and always cause injury to the upper layers of the dermis Third-degree (full-thickness) burns—characterized by complete destruction of the epidermis and dermis May involve underlying muscle and bone Lesion is insensitive to pain because of destruction of nerve endings immediately after injury—intense pain is soon experienced Risk of infection is increased

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