40.1 Introduction to the Skin and Its Function
4 min read•june 18, 2024
Your skin is like a superhero suit, protecting you from harm and regulating your body. It's made up of layers, each with a special job. The outermost layer, the , is your first line of defense against the world.
Underneath, the gives your skin strength and flexibility. It's packed with blood vessels, nerves, and glands that help you stay cool and feel sensations. The , the deepest layer, acts like a cushion and keeps you warm.
Skin Structure and Function
Epidermis and dermis
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- forms outermost layer of skin composed of stratified squamous epithelium provides protective barrier against external factors (UV radiation, microorganisms, chemicals) consists of five distinct layers (, , , , ) undergoes continuous renewal through (process of cell differentiation and maturation)
- located beneath epidermis composed of connective tissue ( and fibers) provides mechanical support and elasticity to skin contains blood vessels (supply nutrients and oxygen, regulate temperature), lymph vessels (aid in immune function and fluid balance), nerve endings (responsible for sensory perception), hair follicles (produce hair), and sweat glands (regulate body temperature) plays crucial role in temperature regulation (blood vessel dilation or constriction) and sensory perception (various receptors for touch, pressure, temperature, pain)
Layers of the epidermis
- (horny layer) outermost layer of epidermis consists of dead, flattened filled with keratin (tough, fibrous protein) provides waterproof barrier and protection against external factors (physical, chemical, biological)
- (clear layer) present only in thick skin (palms and soles) composed of dead, flattened keratinocytes aids in reducing friction and shear forces (prevents skin damage from mechanical stress)
- (granular layer) contains keratinocytes with granules (precursors to keratin) plays role in formation of stratum corneum produces lipids (ceramides, cholesterol, fatty acids) that contribute to skin's barrier function
- (spinous layer) consists of several layers of keratinocytes connected by (cell junctions) provides mechanical strength to epidermis involved in synthesis of keratin and other structural proteins (involucrin, loricrin)
- (basal layer) deepest layer of epidermis contains stem cells that continuously divide to replenish epidermis anchored to dermis via (specialized cell junctions) produces (pigment that protects against UV radiation) via (pigment-producing cells)
Dermis and Hypodermis
Composition and functions of dermis
- Composition of dermis:
- : uppermost layer, contains loose connective tissue and capillary loops (supply nutrients to epidermis)
- : deeper layer, composed of dense irregular connective tissue (collagen and elastin fibers) provides strength and elasticity
- Functions of dermis:
- Provides mechanical support and elasticity to skin
- Contains blood vessels that nourish epidermis and regulate body temperature (vasodilation or vasoconstriction)
- Houses lymph vessels that aid in immune function and fluid balance (remove waste products and excess fluid)
- Contains nerve endings responsible for sensory perception (touch, pressure, temperature, pain)
- Includes hair follicles (produce hair), sweat glands (produce sweat for temperature regulation), and sebaceous glands (produce for skin lubrication)
- Role in temperature regulation:
- Blood vessels in dermis dilate (increase in diameter) to increase heat loss or constrict (decrease in diameter) to retain heat
- Sweat glands produce sweat, which evaporates and cools skin surface ()
- Role in sensory perception:
- Meissner's corpuscles detect light touch and texture (located in papillary dermis)
- Pacinian corpuscles respond to deep pressure and vibration (located in reticular dermis)
- Ruffini endings sense sustained pressure and stretching of skin (located in reticular dermis)
- Free nerve endings detect temperature, pain, and itch sensations (located throughout dermis)
Hypodermis and dermatologic disorders
- (subcutaneous layer) deepest layer of skin, located beneath dermis composed of loose connective tissue and adipose tissue (fat cells) provides insulation (retains body heat), energy storage (triglycerides), and cushioning for underlying structures (muscles, bones)
- Relationship between hypodermis and dermatologic disorders:
- Disorders affecting hypodermis can alter skin appearance and function
- Cellulite: dimpling of skin due to uneven distribution of fat in hypodermis (more common in women)
- : abnormal distribution or loss of body fat, which can be caused by certain medications (antiretroviral drugs) or medical conditions (insulin resistance, autoimmune disorders)
- Impact on drug absorption and distribution:
- Hypodermis acts as reservoir for lipophilic drugs (drugs that dissolve in fat)
- Drugs administered via subcutaneous injection are absorbed through blood vessels in hypodermis (slower absorption compared to intramuscular or intravenous routes)
- Factors such as blood flow (affected by exercise, temperature), body fat composition (varies among individuals), and injection site (abdomen, thigh, upper arm) can influence drug absorption and distribution
- Certain medications (insulin, heparin, growth hormone) are specifically designed for subcutaneous administration to ensure proper absorption and therapeutic effect (sustained release, localized action)
Key Terms to Review (42)
Clients with darker skin: Clients with darker skin have higher levels of melanin, which can affect the presentation and treatment of dermatologic disorders. Nurses should be aware of these differences to ensure accurate diagnosis and effective treatment.
Collagen: Collagen is a structural protein found in the extracellular matrix of various tissues throughout the body, including skin, bones, cartilage, and blood vessels. It provides strength, support, and elasticity to these tissues, playing a crucial role in both clotting and coagulation processes as well as the overall function and integrity of the skin.
Corneocytes: Corneocytes are the terminally differentiated, flattened, and enucleated cells that make up the outermost layer of the epidermis, known as the stratum corneum. These cells are essential for the skin's barrier function, providing protection and preventing water loss from the body.
Dermis: The dermis is the middle layer of the skin that lies beneath the epidermis and above the subcutaneous tissue. It contains blood vessels, nerves, hair follicles, and glands which play essential roles in skin health and function.
Dermis: The dermis is the thick, inner layer of the skin that lies beneath the epidermis. It is composed of two main layers, the papillary layer and the reticular layer, and provides structural support, blood supply, and sensation to the skin.
Desmosomes: Desmosomes are specialized cell-cell junctions that mechanically connect adjacent cells, particularly in tissues that experience high levels of mechanical stress, such as the skin. They act as 'spot welds' that hold cells together and provide structural integrity to tissues.
Desquamation: Desquamation is the process of shedding or peeling of the outermost layer of the skin, known as the stratum corneum. It is a natural and continuous process that helps maintain the integrity and function of the skin's barrier.
Eccrine Glands: Eccrine glands are the most numerous sweat glands in the human body, responsible for producing sweat to regulate body temperature. They are found throughout the skin, except on the lips, and play a crucial role in the skin's function as a protective and homeostatic organ.
Elastin: Elastin is a highly elastic protein found in the extracellular matrix of various tissues, particularly the skin, blood vessels, and lungs. It provides flexibility and resilience, allowing these tissues to stretch and recoil without permanent deformation.
Epidermis: The epidermis is the outermost layer of the skin, providing a protective barrier against environmental damage. It consists of multiple sublayers, including the stratum corneum and the basal layer.
Epidermis: The epidermis is the outermost layer of the skin, serving as a protective barrier against environmental threats and playing a crucial role in the skin's function. It is a stratified squamous epithelium composed of several distinct layers of cells.
Hemidesmosomes: Hemidesmosomes are specialized cell-matrix adhesion complexes that connect the basal layer of the epidermis to the underlying basement membrane. They play a crucial role in maintaining the structural integrity and attachment of the skin.
Hypodermis: The hypodermis, also known as the subcutaneous layer, is the deepest layer of the skin that lies below the dermis. It primarily consists of fat and connective tissue which helps insulate the body and protect underlying muscles and bones.
Hypodermis: The hypodermis, also known as the subcutaneous tissue, is the deepest layer of the skin. It is composed of loose connective tissue and fat that provides insulation, cushioning, and attachment to the underlying tissues and organs.
Integumentary System: The integumentary system is the organ system that provides the body's external covering, known as the skin. It serves as a protective barrier, helps regulate body temperature, and facilitates sensory perception.
Keratinization: Keratinization is the process by which cells in the outermost layer of the skin, known as the epidermis, undergo a transformation to become tough, protective, and waterproof. This process is essential for maintaining the skin's barrier function and overall health.
Keratinocytes: Keratinocytes are the predominant cell type in the epidermis, the outermost layer of the skin. They are responsible for the production of keratin, a structural protein that provides strength and protection to the skin.
Keratohyalin: Keratohyalin is a granular substance found in the granular layer of the epidermis, the outermost layer of the skin. It plays a crucial role in the process of keratinization, which is the transformation of living skin cells into dead, protective keratin-rich cells that make up the stratum corneum, the outermost layer of the epidermis.
Langerhans cells: Langerhans cells are specialized dendritic cells found in the epidermis, playing a crucial role in the skin's immune response. They capture and present antigens to T-cells, initiating an adaptive immune response.
Langerhans Cells: Langerhans cells are a type of dendritic cell found in the epidermis, the outermost layer of the skin. They act as antigen-presenting cells, playing a crucial role in the skin's immune response and defense against pathogens and environmental threats.
Lipodystrophy: Lipodystrophy is a medical condition characterized by abnormal or uneven distribution of body fat, often associated with certain medications or medical conditions. It can manifest in different ways, including the loss of fat tissue (lipoatrophy) or the accumulation of excess fat tissue (lipohypertrophy), and can have significant impacts on various aspects of health and well-being.
Melanin: Melanin is a natural pigment produced by specialized cells called melanocytes, which are found in the basal layer of the epidermis. It is responsible for the coloration of the skin, hair, and eyes, and plays a crucial role in protecting the skin from the harmful effects of ultraviolet (UV) radiation.
Melanocytes: Melanocytes are specialized pigment-producing cells found in the basal layer of the epidermis, the outermost layer of the skin. These cells are responsible for the production and distribution of melanin, the pigment that determines skin, hair, and eye color.
Merkel Cells: Merkel cells are specialized mechanoreceptor cells found in the basal layer of the epidermis, the outermost layer of the skin. They play a crucial role in the sense of touch and pressure perception.
Panniculitis: Panniculitis is a group of inflammatory conditions that affect the subcutaneous fat layer of the skin. It is characterized by the development of painful, red nodules or plaques on the skin, often on the lower extremities.
Papillae: Papillae are small, nipple-like projections on the skin and mucous membranes. They play a crucial role in sensory perception and nutrient absorption.
Papillary Dermis: The papillary dermis is the uppermost layer of the dermis, the second layer of the skin. It is composed of connective tissue and contains capillaries that nourish the epidermis above it, as well as specialized nerve endings that provide sensations of touch, pressure, and temperature.
Reticular Dermis: The reticular dermis is the deeper layer of the dermis, the second layer of the skin. It is composed of a dense network of collagen and elastic fibers that provide structure, support, and elasticity to the skin.
Sebum: Sebum is an oily, waxy substance produced by the sebaceous glands in the skin. It acts as a natural lubricant and protectant, helping to maintain the skin's barrier function and prevent water loss.
Stratum basale: The stratum basale is the deepest layer of the epidermis, consisting of a single row of continually dividing keratinocytes. It plays a critical role in the regeneration of the skin.
Stratum Basale: The stratum basale, also known as the basal layer, is the deepest layer of the epidermis, the outermost layer of the skin. It is responsible for the continuous regeneration of the epidermis, providing new cells to replace those that are shed from the skin's surface.
Stratum corneum: The stratum corneum is the outermost layer of the epidermis, composed mainly of dead keratinized cells. It acts as a primary barrier to protect underlying tissues from infection, dehydration, and chemicals.
Stratum corneum: The stratum corneum is the outermost layer of the epidermis, the skin's protective barrier. It is composed of flattened, dead skin cells called corneocytes that are held together by lipids, creating a waterproof, protective shield for the body.
Stratum granulosum: The stratum granulosum is the third layer of the epidermis, located between the stratum spinosum and stratum lucidum. It plays a crucial role in skin barrier function and water retention.
Stratum Granulosum: The stratum granulosum is a layer of the epidermis, the outermost portion of the skin. It is composed of flattened, granular keratinocytes that are undergoing the process of cornification, a critical step in the formation of the protective barrier function of the skin.
Stratum lucidum: The stratum lucidum is a thin, clear layer of dead skin cells in the epidermis. It is found only in the thick skin areas such as the palms of the hands and soles of the feet.
Stratum Lucidum: The stratum lucidum is a thin, transparent layer of the epidermis located between the stratum granulosum and the stratum corneum. It serves as a transitional zone between the living cells of the epidermis and the dead, flattened cells of the outermost skin layer.
Stratum spinosum: The stratum spinosum is a layer of the epidermis located between the stratum basale and the stratum granulosum. It is characterized by its spiny appearance due to desmosomes that connect keratinocytes.
Stratum spinosum: The stratum spinosum, also known as the spinous layer or prickle cell layer, is one of the five main layers of the epidermis, the outermost layer of the skin. It plays a crucial role in the structure and function of the skin.
Superficial fascia: Superficial fascia is a layer of connective tissue that lies just beneath the skin and is composed primarily of adipose (fat) tissue. It plays a critical role in storing fat, providing insulation, and serving as a pathway for nerves and blood vessels.
Thermoregulation: Thermoregulation is the process by which the body maintains its internal temperature within a narrow, optimal range, despite changes in the external environment. It is a critical physiological function that helps the body adapt and survive in different temperature conditions.
Vitamin D Synthesis: Vitamin D synthesis is the process by which the body naturally produces vitamin D, an essential nutrient that plays a crucial role in maintaining bone health, regulating calcium and phosphorus levels, and supporting immune function. This process occurs primarily in the skin when it is exposed to ultraviolet B (UVB) radiation from sunlight.