INTEGUMENTARY SYSTEM

[Audio] BIO 1 Integumentary System. INTEGUMENTARY SYSTEM.

[Audio] Objectives Describe the general functions of the integumentary system. Identify the different structures in the integumentary system and describe their specific functions. Identify the normal and altered functions of the skin..

[Audio] INTEGUMENTARY SYSTEM The integumentary system consists of the skin and accessory structures, such as hair, glands, and nails. Integument means covering. The appearance of the integumentary system can indicate physiological imbalances in the body. Indicators of Physiological Imbalances The condition and appearance of the integumentary system can reflect the overall health of an individual. For example: Color Changes: Yellowing of the skin (jaundice) may indicate liver problems, while paleness can suggest anemia. Rashes or Lesions: These can signal allergic reactions, infections, or autoimmune disorders. Hair Loss: Sudden or patchy hair loss might be linked to stress, hormonal changes, or nutritional deficiencies. Nail Changes: Abnormalities in nail color, shape, or texture can indicate various health issues, including respiratory or circulatory problems..

[Audio] Functions: Protection Sensation Vitamin D Production Temperature Regulation Excretion Protection: The skin acts as a barrier against environmental hazards, including bacteria, UV radiation, and chemical exposure. Regulation: It helps maintain homeostasis by regulating body temperature through sweat production and blood flow. Sensation: Contains sensory receptors that allow the body to perceive touch, pain, temperature, and pressure. Vitamin D Synthesis: When exposed to sunlight, the skin synthesizes vitamin D, which is essential for calcium absorption and bone health..

[Audio] 1. Protection Ultraviolet Lights (melanin Absorbs Uv) Microorganisms And Other Foreign Substances Hair On The Head Act As Heat Insulator. Eyebrows Keeps Sweat Out Of The Eyes Eyelashes Protect The Eyes From Foreign Objects Hair In The Nose And Ears Intact Skin Reduce Water Loss (its Lipids Act As A Barrier To Water Diffusion) Ultraviolet Light Protection Melanin Production: Melanin is a pigment produced by melanocytes in the skin. It absorbs harmful ultraviolet (U-V---) radiation from the sun, reducing the risk of D-N-A damage that can lead to skin cancer. The more melanin present, the darker the skin, which offers greater protection against UV rays. Defense Against Microorganisms and Foreign Substances Barrier Function: The skin acts as a physical barrier that prevents pathogens, such as bacteria and viruses, from entering the body. The outer layer of skin (epidermis) is composed of tightly packed cells that are difficult for microorganisms to penetrate. Antimicrobial Proteins: The skin secretes substances like defensins and cathelicidins that have antimicrobial properties, further protecting against infections. Hair as Insulation Heat Insulation: The hair on the head provides insulation by trapping air, which helps to retain body heat. This is particularly important in colder environments, where maintaining body temperature is crucial for survival. Sweat Control Eyebrows: These help keep sweat from dripping into the eyes, which can impair vision and cause discomfort. Eyelashes: They serve as a barrier to protect the eyes from dust, debris, and other foreign objects, preventing irritation and potential injury. Nasal and Ear Hair Hair in the Nose and Ears: These hairs filter out dust, pollen, and other airborne particles, preventing them from entering the respiratory system and inner ear, thereby reducing the risk of infections and irritation. Water Loss Prevention Intact Skin Barrier: The skin's outer layer contains lipids (fats) that create a waterproof barrier. This barrier is essential for preventing excessive water loss from the body, maintaining hydration, and supporting overall health. When the skin is intact, it minimizes the risk of dehydration and maintains fluid balance..

[Audio] 2. Sensation The Integumentary System Has Sensory Receptors . Heat, Cold, Touch, Pressure Pain.

[Audio] Sensory Receptors 1. Thermoreceptors (temperature) 2. Nociceptors (pain) = stimulates involuntary motor response. 3. Mechanoreceptors (pressure) Merkel receptor = detects steady pressure from small objects. Meissner corpuscle = useful for detecting texture or movement of objects against the skin. Pacinian corpuscle = detects large changes in the environment i.e vibrations. 2. ex . Pulling of hands away from a hot surface. Mechanoreceptors are specialized sensory receptors in the skin that respond to mechanical stimuli, such as pressure, vibration, and texture. They play a crucial role in our ability to perceive touch and environmental changes. Here are three key types of mechanoreceptors: 1. Merkel Receptors Function: These receptors are responsible for detecting steady pressure and texture. They provide information about the shape and texture of objects. Location: Merkel receptors are found in the basal layer of the epidermis, particularly in areas of the skin that are sensitive to touch, such as fingertips and lips. Response: When pressure is applied, they send signals to the brain, allowing us to perceive fine details and shapes of small objects. 2. Meissner Corpuscles Function: Meissner corpuscles are sensitive to light touch and are particularly useful for detecting changes in texture and movement of objects against the skin. Location: These receptors are located just beneath the epidermis, primarily in areas like the fingertips, palms, soles of the feet, and around the lips. Response: They are rapidly adapting receptors, meaning they respond quickly to changes in stimuli. This allows us to sense when something moves across the skin or when we are touching different textures. 3. Pacinian Corpuscles Function: Pacinian corpuscles are specialized for detecting deep pressure and vibrations. They are particularly responsive to large changes in the environment, such as vibrations from a phone or the impact of a heavy object. Location: These receptors are found deeper in the dermis and in the subcutaneous tissue, making them more sensitive to deeper pressure. Response: They are also rapidly adapting, which means they respond quickly to changes but stop firing if the pressure remains constant. This allows us to perceive vibrations and larger pressure changes effectively..

[Audio] Sensory Receptors. [image]. SENSORY RECEPTORS.

[Audio] Functions: UV light ↓ PRECURSOR molecule is formed ↓ Carried by the blood to the Liver to modify it. ↓ Kidneys modify it further. ↓ Formation of active Vitamin D Vitamin D Production PRECURSOR molecule: Vitamin D3 Cholecalciferol kidneys Calcitriol (active form of Vitamin D) Vitamin D Production Process UV Light Exposure When the skin is exposed to ultraviolet (U-V---) light from the sun, a precursor molecule known as 7-dehydrocholesterol (found in the skin) absorbs this UV radiation. Formation of Precursor Molecule The UV light converts 7-dehydrocholesterol into cholecalciferol (Vitamin D3). This process occurs primarily in the epidermis. Transport to the Liver The newly formed cholecalciferol is then carried by the bloodstream to the liver. Modification in the Liver In the liver, cholecalciferol undergoes a process called hydroxylation, where it is converted into 25-hydroxyvitamin D (calcidiol). This is the primary storage form of Vitamin D in the body. Transport to the Kidneys The 25-hydroxyvitamin D is then transported to the kidneys for further modification. Final Modification in the Kidneys In the kidneys, another hydroxylation occurs, converting 25-hydroxyvitamin D into 1,25-dihydroxyvitamin D (calcitriol), which is the active form of Vitamin D..

[Audio] Functions: 4. temperature regulation Thermoregulation (Homeostasis) the body temperature is within normal range even when environmental temperature varies. Radiation (infrared energy) Convection (air movement) Conduction (direct contact with an object) Perspiration Evaporation of water from your skin if it is wet (sweating). ... Radiation (similar to heat leaving a woodstove). ... Conduction (such as heat loss from sleeping on the cold ground). ... Convection (similar to sitting in front of a fan or having the wind blow on you)..

[Audio] 5. EXCRETION Small amount of waste products are lost through the skin in gland secretions. The integumentary system plays a minor role in excretion, the removal of waste products from the body. In addition to water and salts, sweat contains small amounts of waste products, such as urea, uric acid, and ammonia. Even though the body can lose large amounts of sweat, the sweat glands do not play a significant role in the excretion of waste products..

[Audio] S-K-I-N. [image]. SKIN.

[Audio] The illustration shows a cross section of the skin that has epidermis and dermis of the skin that is followed by subcutaneous tissue (hypodermis). The dermis has sebaceous gland, arrector pili (smooth muscle), hair follicle, nerve, vein, artery, and sweat gland. The subcutaneous tissue has adipose tissue..

[Audio] The skin is made up of two major tissue layers: the epidermis and the dermis. The epidermis is the most superficial layer of skin. It is a layer of epithelial tissue that rests on the dermis. The dermis is a layer of dense connective tissue. The skin rests on the subcutaneous tissue, which is a layer of connective tissue. The subcutaneous tissue is not part of the skin. Structure of the Skin Epidermis Description: Outermost layer. Tissue Type: Stratified squamous epithelial tissue. Function: Provides protection, regulates water loss, and contains sensory cells. Dermis Description: Beneath the epidermis, thicker layer. Tissue Type: Dense connective tissue. Function: Supports and nourishes the epidermis, contains blood vessels, nerves, hair follicles, and glands. Subcutaneous Tissue (Hypodermis) Description: Deepest layer, not part of the skin. Tissue Type: Loose connective tissue and adipose tissue. Function: Insulates, protects underlying structures, and stores energy..

[Audio] Epidermis And Dermis The illustration A shows a cross section of skin that has epidermis above the dermal papilla. The illustration B shows direction of cell movement from deep layer of stratum basale followed by stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum (superficial layer)..

[Audio] Epidermis The epidermis, known as the cutaneous membrane, is a keratinized stratified squamous epithelium. The epidermis prevents water loss and resists abrasion. The epidermis is composed of distinct layers called strata..

[Audio] Epidermis The most superficial stratum of the epidermis, consists of dead squamous cells filled with keratin. Keratin gives the stratum corneum its structural strength. Cells of the deepest strata perform mitosis. As new cells form, they push older cells to the surface, where they slough, or flake off. Excessive sloughing of stratum corneum cells from the surface of the scalp is called dandruff. In skin subjected to friction, the number of layers in the stratum corneum greatly increases, producing a thickened area called a callus. Over a bony prominence, the stratum corneum can thicken to form a cone-shaped structure called a corn..

[Audio] New cell formation by Mitosis Mitosis is essential for cell division in the integumentary system, occurring mainly in the stratum basale of the epidermis and the dermis. Process: Stem cells in the stratum basale divide to produce new keratinocytes, which migrate upward and differentiate. Functions: Wound Healing: Rapid cell division restores the epidermis after injury. Skin Renewal: Continuous shedding of dead cells requires ongoing new cell production. Regulation: Growth factors and hormones control mitosis to maintain skin health..

[Audio] Older cells are pushed to the surface New cell formation by Mitosis As new cells are formed through mitosis in the stratum basale, older cells are pushed towards the surface of the skin. Here's a brief overview: Process: New keratinocytes generated in the stratum basale move upward through the layers of the epidermis. As they migrate, they undergo changes, becoming more flattened and filled with keratin. Outcome: Older cells eventually reach the outermost layer, the stratum corneum, where they form a protective barrier. These cells are eventually shed through natural exfoliation..

[Audio] Cells change shape and chemical composition Changes in Skin Cells As keratinocytes move from the stratum basale to the skin surface: Shape Change: Cells transition from cuboidal to flattened, scale-like shapes. Chemical Composition Change: They produce keratin for strength and accumulate lipids for moisture barrier..

[Audio] Keratinization Cells change shape and chemical composition Keratinization is the process by which keratinocytes undergo transformation as they migrate from the deeper layers of the epidermis to the surface. Here's a brief overview: Process: As keratinocytes move upward, they begin to produce keratin, a tough, fibrous protein. Cells lose their nuclei and organelles, becoming more flattened and filled with keratin. Stages: Stratum Granulosum: Cells begin to accumulate keratohyalin granules, aiding in keratin formation. Stratum Corneum: Fully keratinized, dead cells form a protective, waterproof barrier. Function: Provides strength and resilience to the skin. Protects against environmental damage and prevents water loss..

[Audio] Outer layer of dead epithelial cells (resists abrasion and forms a permeability barrier) Cells change shape and chemical composition The outer layer of the skin, known as the stratum corneum, consists of dead keratinized epithelial cells. Here's a concise overview: Composition: Made up of multiple layers of dead, flattened keratinocytes filled with keratin. Functions: Resists Abrasion: Provides a tough barrier against physical damage. Permeability Barrier: Prevents water loss and protects against environmental contaminants..

[Audio] Keratinocytes Cells of the epidermis The body’s most abundant epithelial cells Contain large amounts of keratin Gives the Stratum Corneum structural strength.

[image] Direction of cell movement Stratum comeum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale Superficial Deep.

[Audio] Deepest Stratum Consist of cuboidal or columnar cells that undergo mitotic division about every 19 days..

[Audio] The cells in these layers have lots of desmosomes (spiny appearance). Desmosomes are specialized cell structures that play a crucial role in maintaining the integrity and strength of tissues, particularly in the skin. Here's a brief overview: Structure: Desmosomes are composed of protein complexes that connect adjacent cells. They consist of cadherins (adhesion proteins) and intermediate filaments, which provide mechanical stability. Function: Cell Adhesion: They anchor cells together, forming a strong bond that resists mechanical stress. Tissue Integrity: Essential for maintaining the structural integrity of the epidermis and other epithelial tissues.

[Audio] The thin layer of cells in the epidermis..

[Audio] A thin, clear layer of dead skin cells in the epidermis named for its translucent appearance..

[Audio] The most superficial stratum of the epidermis. Consists of dead squamous cells filled with Keratin. Coated and surrounded by Lipids Composed of 25 or more layers of dead squamous cells joined by desmosomes. In skin subjected to friction, the number of layers in the stratum corneum greatly increases, producing a thickened area called a callus. Over a bony prominence, the stratum corneum can thicken to form a cone-shaped structure called a corn..

[Audio] Dermis Collagen fibers, oriented in many directions, and elastic fibers are responsible for the structural strength of the dermis and resistance to stretch. The dermis is composed of dense collagenous connective tissue containing fibroblasts, adipocytes, and macrophages. Nerves, hair follicles, smooth muscles, glands, and lymphatic vessels extend into the dermis..

[Audio] Dermis Some collagen fibers are oriented in more directions than others, forming cleavage lines. Cleavage lines, or tension lines, in the skin, are more resistant to stretch. Collagen Fibers: Collagen fibers are arranged in various orientations, creating a network that provides strength and elasticity. Some fibers are oriented in specific directions, forming cleavage lines (or Langer's lines). Cleavage Lines: These lines indicate the natural orientation of collagen fibers in the skin. Understanding these lines is important for surgical procedures, as incisions made parallel to cleavage lines heal better and result in less scarring. The dermis is the layer of skin beneath the epidermis, composed of dense connective tissue. Within the dermis:.

[Audio] An incision made parallel with these lines tends to gap less and produce less scar tissue. If the skin is overstretched for any reason, the dermis can be damaged, leaving stretch marks. When making surgical incisions in the skin: Parallel Incisions: Incisions made parallel to the cleavage lines (or Langer's lines) tend to gap less. This alignment minimizes tension on the wound edges, promoting better healing. Benefits: Reduced gapping leads to less scar tissue formation. Results in finer, less noticeable scars post-healing. Stretch marks (striae) occur when the skin is overstretched, damaging the dermis. Causes: Rapid weight changes, pregnancy, growth spurts, hormonal changes. Mechanism: Overstretching tears collagen and elastin fibers. Appearance: Initially red or purple, they fade to lighter colors over time..

[Audio] Dermis Dermal papillae are projections toward the epidermis found in the upper part of the dermis. The dermal papillae contain many blood vessels. The dermal papillae in the palms of the hands, the soles of the feet, and the tips of the digits are arranged in parallel, curving ridges that shape the overlying epidermis into fingerprints and footprints. Dermal papillae are small, finger-like projections located in the upper part of the dermis, extending toward the epidermis. Function: They contain numerous blood vessels, providing nutrients to the epidermis. Enhance the connection between the dermis and epidermis, improving nutrient exchange. Special Features: In areas like the palms of the hands, soles of the feet, and tips of the digits, dermal papillae are arranged in parallel, curving ridges. These patterns shape the overlying epidermis, creating unique fingerprints and footprints..

[Audio] Subcutaneous Tissue Also called HYPODERMIS Made up of loose connective tissues, including adipose tissues Contains about half of the body’s stored lipids Functions as padding and INSULATION Responsible for some of the difference in appearance between men and women and of the same sex. The hypodermis, also known as the subcutaneous layer, is the deepest layer of skin. Composition: Made up of loose connective tissues, primarily adipose tissue. Contains about half of the body's stored lipids. Functions: Provides padding and insulation to protect underlying structures. Helps regulate body temperature. Appearance: Contributes to differences in body shape and appearance between men and women, as well as variations among individuals of the same sex..

[Audio] Skin Color factors that determine skin color: Pigments in the skin. Blood circulating through the skin. Thickness of the stratum corneum. Pigments in the Skin: Melanin: The primary pigment responsible for skin color, produced by melanocytes. Higher melanin levels result in darker skin tones. Carotene: A yellow-orange pigment found in certain foods that can influence skin color, particularly in areas like the palms and soles. Blood Circulating Through the Skin: The amount of blood flow can affect skin color. Increased blood flow (for example, during exercise or blushing) can give the skin a reddish hue, while decreased blood flow can lead to a paler appearance. Thickness of the Stratum Corneum: The thickness of the outermost layer of skin can influence how light is absorbed and reflected, affecting overall skin tone. Thicker layers may appear darker..

[Audio] Skin Color The two primary pigments are melanin and carotene. Melanin is the group of pigments primarily responsible for skin, hair, and eye color. Carotene is a yellow pigment found in plants such as squash and carrots. Melanin: Definition: Melanin is a group of pigments produced by specialized cells called melanocytes. It is primarily responsible for the coloration of skin, hair, and eyes. Types: There are different types of melanin, including: Eumelanin: The most common type, which can be brown or black. Higher levels of eumelanin result in darker skin tones. Pheomelanin: A lighter pigment that provides yellow to red hues, often found in individuals with lighter skin. Function: Melanin protects the skin from UV radiation by absorbing harmful rays, reducing the risk of skin damage and cancer. The amount and type of melanin produced are influenced by genetic factors, sun exposure, and hormonal changes. Carotene: Definition: Carotene is a yellow-orange pigment found in many fruits and vegetables, such as carrots, squash, and sweet potatoes. Sources: It is a dietary pigment that accumulates in the skin, particularly in the stratum corneum and fatty tissues. Function: While carotene contributes to skin color, its effect is generally less pronounced than that of melanin. It can impart a yellowish tint, especially in areas of thicker skin, such as the palms and soles..

[Audio] Melanin Melanin is produced by melanocytes and then packaged into vesicles called melanosomes, which move into the cell processes of melanocytes. (Epithelial cells phagocytize the tips of the melanocyte cell processes, thereby acquiring melanosomes.) Melanocytes: Specialized cells located in the basal layer of the epidermis responsible for producing melanin. Melanosomes: Once synthesized, melanin is packaged into vesicles called melanosomes. Transfer to Epithelial Cells: The melanosomes move into the cell processes (dendritic extensions) of melanocytes. Phagocytosis: Epithelial cells (keratinocytes) then phagocytize the tips of these melanocyte processes, effectively engulfing the melanosomes. This process allows keratinocytes to acquire melanin, contributing to skin pigmentation..

[Audio] Melanin Transfer to Epithelial Cells The illustration shows an enlarged view of melanocyte that has melanosomes, nucleus, and Golgi apparatus and surrounded by epithelial cell to which melanosomes are transferred. Large amounts of melanin form freckles or moles in some regions of the skin. Melanin production is determined by genetic factors, exposure to light, and hormones. Genetic factors are responsible for the amounts of melanin produced in different races. Since all races have about the same number of melanocytes, racial variations in skin color are determined by the amount, kind, and distribution of melanin. Exposure to ultraviolet light—for example, in sunlight— stimulates melanocytes to increase melanin production. The result is a suntan. Although many genes are responsible for skin color, a single mutation can prevent the production of melanin and cause albinism..

[Audio] Carotene Orange-yellow pigment. Found in plants such as squash and carrots (source of Vitamin A) Lipid-soluble; when consumed, it accumulates in the stratum corneum and in the adipocytes of the dermis and subcutaneous tissues. Carotene is an orange-yellow pigment that is a type of carotenoid, which is a class of pigments found in various plants. Sources: Carotene is abundant in a variety of fruits and vegetables, particularly: Squash Carrots Other sources include sweet potatoes, pumpkins, and leafy greens. It is a precursor to Vitamin A, an essential nutrient important for vision, immune function, and skin health. Properties: Lipid-Soluble: Carotene is soluble in fats, which means it can be stored in fatty tissues of the body. When consumed, carotene is absorbed through the digestive system and transported into the bloodstream. Accumulation: After absorption, carotene can accumulate in: Stratum Corneum: The outermost layer of the skin, where it can impart a yellowish tint, especially in areas with thicker skin, such as the palms and soles. Adipocytes: Fat cells located in the dermis and subcutaneous tissues, where it can be stored for later use..

[Audio] Accesory Structures H-A-I-R Glands Nails.

[Audio] H-A-I-R Found everywhere on the skin except on : Palms Soles Parts of the genitalia Distal segment of the fingers and toes Hair is a common feature of human skin, but it is notably absent in certain areas: Palms of the Hands: The skin on the palms is specialized for grip and tactile sensitivity, which is why it lacks hair. Soles of the Feet: Similar to the palms, the soles have a thickened epidermis that enhances durability and grip, resulting in a lack of hair. Parts of the Genitalia: Certain regions of the genital area are hairless, particularly in the inner aspects, where skin is more sensitive. Distal Segments of the Fingers and Toes: The tips of fingers and toes do not have hair, allowing for better tactile perception and sensitivity..

[Audio] Parts Of The Hair Each strand of hair is made up of : Medulla innermost layer of the hair shaft Cortex – surrounds the medulla *Contains most of the hair's pigment, melanin.* Cuticle – the outermost part of the hair that covers the Cortex. Each strand of hair consists of three main layers, each with distinct characteristics: Medulla: Description: The innermost layer of the hair shaft. Function: It is often a soft, spongy tissue that may be absent in finer hair. The medulla's role is not fully understood, but it may provide some structural support. Cortex: Description: The middle layer that surrounds the medulla. Function: The cortex contains the majority of the hair's pigment, which is primarily melanin. This layer provides strength, color, and texture to the hair. The arrangement of the cortex influences the hair's curliness or straightness. Cuticle: Description: The outermost layer of the hair shaft. Function: The cuticle consists of overlapping, scale-like cells that protect the inner layers of the hair. It acts as a barrier against environmental damage and helps retain moisture within the hair..

[Audio] Hair Shaft The hair that is visible. Protrudes above the surface of the skin. Definition: The hair shaft is the visible part of the hair that protrudes above the surface of the skin. Characteristics: Visibility: It is the portion of hair that can be seen and touched, extending from the hair follicle embedded in the skin. Structure: The hair shaft is composed of the three layers: medulla, cortex, and cuticle, which contribute to its strength, color, and texture. Growth: The hair shaft is formed as new cells are produced in the hair follicle, pushing older cells upward and outwards, where they harden and form the visible hair..

[Audio] H-A-I-R bulb Forms the base of the hair follicle that rests on the hHair Papilla. The hair bulb is the base of the hair follicle, a tube-like structure in your skin that produces hair. It's located deep within the dermis, the lower layer of your skin. Key Points about the Hair Bulb: Foundation for Hair Growth: The hair bulb is the starting point for hair growth. It's where new hair cells are constantly produced. Hair Papilla: Inside the hair bulb is the hair papilla, a small, nipple-shaped structure. It's crucial for providing essential nutrients and oxygen to the hair bulb, which is essential for healthy hair growth. Matrix: The hair matrix, a layer of cells surrounding the hair papilla, is where the actual hair cells are produced. These cells divide rapidly and then harden to form the hair shaft, the visible part of the hair. Melanin: Melanin, the pigment that determines hair color, is also produced in the hair bulb. The amount and type of melanin present will determine whether your hair is black, brown, blonde, or red. Think of the hair bulb as a tiny factory for hair production. It's where the building blocks of hair are created and assembled, and it's the health of this factory that ultimately determines the quality and appearance of your hair..

[Audio] H-A-I-R papilla A mass of connective tissue, nerve endings and blood capillaries at the base of the hair follicle. The hair papilla is a crucial component of the hair follicle, located at its base. It's a small, cone-shaped structure that plays a vital role in hair growth. Key Functions of the Hair Papilla: Nutrient Supply: The hair papilla is rich in blood capillaries, which deliver essential nutrients, oxygen, and hormones to the hair bulb, the area where new hair cells are produced. These nutrients are vital for healthy hair growth and development. Nerve Endings: The hair papilla also contains nerve endings. These nerve endings are sensitive to touch and can help regulate hair growth cycles. They may also play a role in hair loss and regrowth. Connective Tissue: The papilla is composed of connective tissue, which provides structural support and helps anchor the hair follicle to the surrounding skin. Think of the hair papilla as the "powerhouse" of the hair follicle. It's the engine that drives hair growth by providing the necessary fuel and support. A healthy hair papilla is essential for producing strong, healthy hair..

[Audio] Arrector Pili Smooth muscle cells Contraction causes a raised area of skin (goose bumps). The Arrector Pili: The Muscles Behind Goosebumps The arrector pili are tiny muscles attached to each hair follicle. They are composed of smooth muscle cells, which are involuntary muscles that contract without conscious effort. Function: Goosebumps: When these muscles contract, they pull the hair follicle upright, causing a raised area of skin. This is what creates the familiar "goosebumps" or "piloerection." Why do we get goosebumps? Cold: Goosebumps are often a response to cold temperatures. The contraction of the arrector pili helps to trap a layer of warm air close to the skin, providing insulation. Fear or Excitement: Goosebumps can also be a physiological response to strong emotions like fear, excitement, or surprise. This is a remnant of a primitive response that may have been helpful in our ancestors. Other Functions: Sensory Perception: The arrector pili may also play a role in sensory perception. By raising the hair follicles, they can increase the sensitivity of the skin to touch and vibrations. Defense Mechanism: In some animals, the erection of hair can make them appear larger and more intimidating to predators..

[image] Hair shaft (above skin surface) Hair root (below skin surface) Hair bulb (base of hair root) Altery Vein Adipose tissue (a) Medulla Cortex Cuticle Hair Arrector pili (smooth muscle) Sebaceous gland Hair follicle wall Hair papilla.

[Audio] GLANDS 2 Major Glands of the Skin : Sebaceous Glands produce sebum Sweat Glands Eccrine sweat glands Apocrine sweat glands Sebaceous glands are tiny structures found throughout the skin, except for the palms of the hands and the soles of the feet. Their primary function is to produce sebum, a natural oily substance that helps to moisturize and protect the skin. Key Functions of Sebum: Moisturization: Sebum forms a protective barrier on the skin, helping to prevent moisture loss and keep the skin hydrated. Protection: Sebum contains antimicrobial properties that can help to protect the skin from bacteria and other harmful microorganisms. Lubrication: Sebum helps to lubricate the skin, making it more flexible and less prone to cracking or dryness. Hair Conditioning: Sebum coats the hair, providing a natural conditioner that helps to keep it soft and healthy. Sebaceous glands are especially abundant on the face, scalp, chest, and back. This is why these areas tend to be oilier than other parts of the body. Overproduction of sebum can lead to acne, a common skin condition characterized by pimples, blackheads, and whiteheads. In contrast, underproduction of sebum can cause dry skin and excessive flaking..

[Audio] Eccrine Sweat Glands Are simple, coiled, tubular glands and release sweat by merocrine secretion. Most numerous in the palms and soles. Secretion mostly water with few salts. Eccrine (merocrine) Sweat Glands Coiled, tubular glands that discharge directly onto skin surface (sensible perspiration) Widely distributed on body surface specially on palms and soles.

[Audio] Apocrine Sweat Glands Simple, coiled, and tubular. Produces a thick secretion rich in organic substances released by Merocrine secretion. Open into hair follicles but only in ARMPITS and GENITALIA (becomes active at puberty). Found in armpits, around nipples and in pubic region. Secrete products into hair follicles via merocrine secretion. Produce sticky, cloudy secretion Nutrient source for bacteria, which cause odors.