5.2 Accessory Structures of the Skin
3 min read•june 18, 2024
The skin is more than just a protective barrier. It's a complex organ with specialized structures that help regulate body temperature, produce important substances, and even enhance our senses. These accessory structures work together to keep us healthy and comfortable.
Hair, sweat glands, and nails are key players in skin function. They help us stay cool, provide sensory information, and protect our bodies. Understanding how these structures work gives us insight into the skin's vital role in maintaining overall health.
Accessory Structures of the Skin
Accessory structures of skin
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- Hair follicles found throughout skin except on palms, soles, and lips consist of within skin and visible above skin
- Sebaceous glands located in usually connected to hair follicles most abundant on face and scalp not found on palms and soles
- Eccrine sweat glands distributed throughout skin most numerous on palms, soles, and forehead
- Apocrine sweat glands found in axillae, areolae, and anogenital regions develop during puberty
- Nails located at distal ends of fingers and toes consist of , , and
Hair follicles and nails
- Hair follicles consist of , , and layers of follicle wall
- contains which produces new hair cells
- Dermal papilla provides blood supply and nutrients to
- Hair follicles provide sensory information through nerve endings help regulate body temperature protect against physical damage and UV radiation
- Nails have nail plate (hard, structure visible on surface), (epithelial layer underneath nail plate), and nail matrix (area at proximal end of nail bed that produces new nail cells)
- Nails protect distal phalanges of fingers and toes enhance sense of touch and manipulation of small objects (threading a needle, playing guitar)
- Nails are primarily composed of , a tough protein that provides strength and protection
Glands in skin homeostasis
- Eccrine sweat glands produce clear, secretion (sweat) consisting mainly of water, salt, and small amounts of other electrolytes
- Help regulate body temperature through evaporative cooling (sweating during exercise or hot weather)
- Assist in maintaining fluid and electrolyte balance
- Apocrine sweat glands produce thick, oily secretion containing proteins, lipids, and steroids
- Secretions are odorless but can be metabolized by bacteria on skin causing body odor (underarm odor)
- Exact function unclear but may be related to pheromone production and sexual attraction
- Sebaceous glands produce , an oily substance composed of lipids and cell debris
- lubricates and waterproofs skin and hair
- Helps maintain skin flexibility and prevents drying and cracking (chapped lips, dry skin)
- Provides some antimicrobial protection due to its acidic pH and certain chemicals in sebum (, )
Skin Layers and Functions
- The skin consists of two main layers: the and
- The is the outermost layer of skin, containing keratinocytes that produce keratin
- The dermis lies beneath the epidermis and contains blood vessels, nerve endings, and various accessory structures
- Melanocytes, located in the epidermis, produce melanin pigment for skin color and UV protection
- The skin plays a crucial role in through its accessory structures and blood flow regulation
Key Terms to Review (53)
Anagen: Anagen is the active phase of the hair growth cycle during which hair follicles rapidly grow. This phase can last for years and determines the length of the hair.
Apocrine sweat gland: Apocrine sweat glands are specialized sweat glands found in certain areas of the body such as the armpits, groin, and around the nipples, which secrete a thicker form of sweat that contributes to body odor when decomposed by bacteria on the skin. Unlike eccrine glands, they begin functioning at puberty and are larger and located deeper in the skin.
Apocrine Sweat Gland: Apocrine sweat glands are a type of secretory gland found in the skin that produce a thicker, oily sweat compared to eccrine sweat glands. They are primarily located in areas with high concentrations of hair follicles, such as the armpits, groin, and areola.
Arrector pili: The arrector pili are small muscles located at the base of hair follicles in the skin. These muscles contract in response to cold or fear, making the hair stand on end and creating what is commonly known as "goosebumps."
Catagen: Catagen is the transitional phase of hair growth, during which the hair follicle shrinks and detaches from the dermal papilla. This phase lasts about two to three weeks and signals the end of the active growth of a hair.
Cortex: In the context of the integumentary system and specifically regarding the accessory structures of the skin, the cortex is the primary part of a hair, composed of keratin, that provides strength, color, and texture. It lies between the hair's outer cuticle and its inner medulla.
Cuticle: The cuticle is a thin layer of clear skin located along the bottom edge of your finger or toe nails, acting as a protective barrier for the nail matrix. It serves to protect new nails from bacterial and fungal infections as they grow.
Dermal Papilla: The dermal papilla is a specialized structure found within the skin's dermis layer. It plays a crucial role in the development and maintenance of various accessory structures of the skin, including hair follicles, sweat glands, and nails.
Dermis: The dermis is the thick layer of living tissue directly beneath the epidermis in the skin, containing nerve endings, sweat glands, hair follicles, and blood vessels. It provides strength and elasticity to the skin through its collagen and elastin fibers.
Dermis: The dermis is the thick, inner layer of the skin that lies beneath the epidermis. It is a complex and dynamic connective tissue that provides structural support, protection, and various functions essential for the integumentary system.
Eccrine sweat gland: Eccrine sweat glands are small tubular structures located in the skin that produce a watery fluid known as sweat, primarily responsible for regulating body temperature through evaporation. They are distributed throughout almost the entire surface of the human body, with higher concentrations in the palms, soles, and forehead.
Eccrine Sweat Gland: Eccrine sweat glands are the most numerous and widely distributed exocrine glands in the human body. They are responsible for the production and secretion of sweat, which plays a crucial role in thermoregulation and maintaining the skin's homeostasis within the context of the accessory structures of the skin.
Epidermis: The epidermis is the outermost layer of the skin, composed of keratinized, stratified squamous epithelium. It serves as a protective barrier against environmental hazards and helps in regulation of moisture loss.
Epidermis: The epidermis is the outermost layer of the skin, serving as the body's primary protective barrier against the external environment. It is a stratified squamous epithelium that plays a crucial role in various aspects of the integumentary system, from tissue types to skin functions and diseases.
Eponychium: The eponychium is a small band of epidermis located at the base of the fingernails and toenails. It functions as a protective barrier, preventing pathogens from entering the nail matrix.
External root sheath: The external root sheath is a layer of the hair follicle that provides a protective sleeve around the hair shaft, extending from the skin surface to the hair bulb. It is composed of epithelial cells and plays a crucial role in hair growth and regeneration.
Germinal Matrix: The germinal matrix is a highly vascular region of the developing brain that serves as the primary site of neurogenesis during fetal development. It is located in the ventricular and subventricular zones of the cerebral hemispheres and is responsible for the production of new neurons and glial cells that will eventually migrate to their final destinations within the brain.
Glassy membrane: The glassy membrane is a thick, transparent layer that exists between the outer root sheath and the inner root sheath of a hair follicle in the integumentary system. It serves as a protective barrier and structural base for the hair follicle.
Hair bulb: The hair bulb is the enlarged, club-shaped structure at the base of the hair follicle containing the cells responsible for producing hair. It is where nutrients are delivered via blood vessels to fuel hair growth.
Hair Bulb: The hair bulb is a specialized structure located at the base of the hair follicle. It is responsible for the growth and regeneration of the hair shaft, providing the essential nutrients and signals required for hair development and cycling.
Hair follicle: A hair follicle is a dynamic organ found in the dermal layer of the skin, responsible for producing individual hairs by packing together keratinized cells. It comprises several layers, including a root sheath and a bulb at its base where hair growth begins.
Hair Follicle: A hair follicle is a tubular structure in the skin that encloses the root of a hair and provides the environment for hair growth. It is considered an accessory structure of the skin, playing a crucial role in the development and maintenance of hair.
Hair matrix: The hair matrix is a rapidly dividing layer of cells found at the base of the hair follicle. These cells are responsible for producing new hair and are the source of both the hair shaft and the inner root sheath.
Hair papilla: The hair papilla is a small, cone-shaped elevation located at the base of the hair follicle that contains capillaries and nerves. It plays a crucial role in the growth of hair by supplying nutrients and signals needed for hair development.
Hair root: The hair root is the part of the hair that is located below the surface of the epidermis, embedded in the hair follicle. It is responsible for the growth of the hair by cell division in its lower part.
Hair shaft: The hair shaft is the part of the hair that is visible above the skin surface. It is made up of dead, keratinized cells that give hair its strength and color.
Hyponychium: The hyponychium is a dense layer of skin under the free edge of the nail. It acts as a barrier protecting the nail bed from infections and external damage.
Hypotonic: Hypotonic refers to a solution or environment that has a lower solute concentration compared to another solution or the interior of a cell. This creates an osmotic gradient that causes water to move from the hypotonic environment into the higher solute concentration area, such as the interior of a cell.
Internal root sheath: The internal root sheath is a component of the hair follicle that surrounds the lower part of the growing hair shaft, providing structural support and playing a role in shaping the hair. It is composed of three layers: the cuticle, Huxley's layer, and Henle's layer, each contributing to its protective and formative functions.
Keratin: Keratin is a type of structural protein that is the primary component of various tissues and structures in the human body, including the skin, hair, nails, and the cytoskeleton of cells. It is known for its strength, durability, and protective properties, making it essential for the proper functioning of several physiological systems.
Keratinized: Keratinized refers to the process of cells becoming hardened and protective through the production of the protein keratin. This is a crucial feature of the accessory structures of the skin, such as hair, nails, and the outer layer of the epidermis, which provide a barrier against the external environment.
Keratinocyte: Keratinocytes are the primary type of cell found in the epidermis, the outermost layer of the skin, responsible for producing keratin, a protein that gives skin its strength and resilience. These cells originate from the basal layer and move upward, changing their form as they go, to eventually form the tough outer skin surface.
Lauric Acid: Lauric acid is a saturated fatty acid that is found in various plant-based oils, particularly coconut and palm kernel oils. It is a key component of the accessory structures of the skin, playing a crucial role in maintaining the skin's barrier function and overall health.
Lunula: The lunula is the visible part of the nail matrix that appears as a white crescent shape at the base of the fingernail or toenail. It plays a crucial role in nail growth and reflects the health of the nail matrix.
Medulla: In the context of the integumentary system, the medulla refers to the innermost layer of hair, made up of a soft, keratinized core that provides elasticity and flexibility to the hair strand. Within the context of gross anatomy of the kidney, it is the innermost part of the kidney that contains nephrons essential for urine production through filtration, reabsorption, and secretion processes.
Melanocyte: A melanocyte is a specialized skin cell that produces melanin, the pigment responsible for skin, hair, and eye color. Melanocytes are a crucial component of the skin's accessory structures, playing a vital role in the protection and coloration of the integumentary system.
Nail bed: The nail bed is the skin beneath the nail plate that provides support and nourishment to the nail. It contains nerves, blood vessels, and melanocytes that contribute to nail health and color.
Nail Bed: The nail bed is the specialized skin underneath the nail plate that nourishes and supports the growth of the nail. It is an accessory structure of the skin that plays a crucial role in the formation and health of the nails.
Nail body: The nail body is the visible part of the nail that is composed of hardened keratin and covers the tips of the fingers and toes. It protects the distal phalanx, the fingertip, and the surrounding soft tissues from injuries.
Nail cuticle: The nail cuticle, also known as the eponychium, is a thin layer of tissue that overlaps and protects the nail plate at its base. It serves as a barrier to prevent pathogens from entering the nail bed and causing infections.
Nail fold: The nail fold is the skin that frames and supports the edges of the nail plate on three sides. It provides a protective barrier which guards against infection at the nail margins.
Nail Matrix: The nail matrix is the hidden part of the nail that lies beneath the skin at the base of the nail. It is the living, germinal tissue that produces the nail plate, which is the visible part of the nail that grows outward from the base of the finger or toe.
Nail Plate: The nail plate is the visible part of the nail that covers the upper surface of the fingertip or toe. It is a hardened, translucent structure made of keratin that protects the delicate skin underneath and enhances the sensory function of the digits.
Nail root: The nail root is the part of the nail that is embedded under the skin at the base of the fingernail or toenail, where nail growth begins. It is a critical component of the nail unit, providing the cells necessary for nail formation.
Sapienic Acid: Sapienic acid is a fatty acid that is found naturally in human sebum, the oily secretion of the sebaceous glands in the skin. It is a key component of the skin's protective barrier and plays a crucial role in the accessory structures of the skin.
Sebaceous gland: Sebaceous glands are small oil-producing glands present in the skin of mammals, located in the dermis layer. They secrete an oily substance called sebum, which helps to lubricate and waterproof the skin and hair.
Sebaceous Gland: Sebaceous glands are specialized exocrine glands found within the skin that produce an oily substance called sebum. These glands are a key accessory structure of the integumentary system and play a crucial role in maintaining the skin's protective barrier and moisture levels.
Sebum: Sebum is an oily substance secreted by sebaceous glands located in the dermis of the skin. It helps to lubricate and protect the skin and hair, keeping them soft and preventing them from drying out.
Sebum: Sebum is a waxy, oily substance produced by the sebaceous glands in the skin. It plays a crucial role in the function and protection of the integumentary system, as well as in the body's innate immune response.
Sudoriferous glands: Sudoriferous glands are specialized exocrine glands found in the dermis layer of the skin, responsible for producing sweat. They play a critical role in regulating body temperature and excreting waste products.
Telogen: Telogen is the resting phase in the hair growth cycle, during which hair growth stops and the hair follicle rests before the hair eventually falls out. This phase typically lasts for about 2 to 4 months before a new hair begins to grow from the same follicle.
Thermoregulation: Thermoregulation is the process by which organisms maintain their internal body temperature within a tolerable range, despite external temperature changes. It involves various physiological responses to either produce or dissipate heat as needed.
Thermoregulation: Thermoregulation is the process by which the body maintains its core temperature within a narrow, optimal range, despite changes in environmental temperature or internal heat production. This vital function ensures the proper functioning of the body's cells, tissues, and organs.