Bio Anthro: Skin and Melanin Types

Chunk 10: Pancreas and Blood Sugar Chunk 11: Pineal Gland and Melatonin

A&P Honors: Ch. 5.4 — Melanin, Carotene, and Hemoglobin

Anatomy and Physiology Chapter 5 Etymological Breakdown of the Term Integumentar y System: • Integument-: Derived from the Latin root integumentum, which means "a covering," "disguise," or "cloak" (stemging from integere, meaning to cover or protect). • -ary: A standard adjectival suffix meaning "pertaining to" or "relating to.” • System: Derived from the Greek systēma, meaning a "organized whole" or a "combination of parts" working together. Put it all together, and the integumentary system literally translates to the system relating to the body's covering (the skin, hair, nails, and associated glands that protect the body as an organized unit). Overview of the Integumentary System The Skin and Beyond: • While commonly called the skin, the integumentary system is actually a complex organ system. • Includes the skin (cutaneous membrane) plus its accessory structures: hair, nails, and sweat and sebaceous (oil) glands. Scale & Importance: • The skin is the largest organ of the body, accounting for about 16 percent of body weight (16 to 20 pounds average adult) and covering a surface area of 1.5 to 2 square meters. Primary Functions: • Acts as the immediate barrier protecting the body from pathogens, chemicals, and mechanical injury. • Prevents fluid loss and regulates body temperature and sensation. Clinical Significance: • Often reflects overall health; changes in color, texture, or integrity can indicate underlying systemic diseases (e.g., cardiovascular, respiratory, or liver conditions). https://www.researchgate.net/ Overview of Skin Layers Dual-Layered Organ: • The skin consists of two main, distinct layers resting on a supportive subcutaneous layer. 1. Epidermis: • The superficial, outermost layer of the skin. • Composed of keratinized stratified squamous epithelium. • Avascular (receives nutrients via diffusion from the dermis below). 2. Dermis: • The deeper layer lying directly beneath the epidermis. • Composed of connective tissue (areolar and dense irregular). • Vascularized; houses blood vessels, lymphatic vessels, nerves, hair follicles, and sweat glands. Overview of Skin Layers 3. Hypodermis (Subcutaneous Layer / Superficial Fascia): • Technically not part of the skin itself, but closely associated. • Composed of loose areolar and adipose tissue; anchors skin to underlying muscle and bone while providing insulation and cushioning. https://quizlet.com/ Thick Skin vs. Thin Skin (Epidermal Layers) Classification Criteria: • Skin is categorized as either "thick" or "thin" based on the number of epidermal layers and the depth of the stratum corneum, not the total thickness of the skin organ as a whole. Thin Skin: • Contains four layers (stratum basale, spinosum, granulosum, and corneum). NOTE: These are listed from deep to superficial • Lacks the stratum lucidum. • Covers the vast majority of the body surface and contains hair follicles and sebaceous glands. Thick Skin: • Contains five layers (features the translucent stratum lucidum). • Found only on areas subject to heavy friction and abrasion: the palms of the hands and the soles of the feet. • Features a much thicker stratum corneum and lacks hair follicles and sebaceous glands. https://med.libretexts.org/ Cells of the Epidermis 1. Keratinocytes: • The most abundant cells in the epidermis (approx. 90%). • Synthesize keratin, a tough, fibrous protein that gives skin its hardness, durability, and water-resistant properties. • Continuously produced by stem cells in the deepest layer, pushing upward and eventually shedding. 2. Melanocytes: • Located in the deepest epidermal layer. • Produce the pigment melanin, which absorbs UV radiation and protects deeper cell DNA; transferred to keratinocytes. 3. Langerhans Cells: • Dendritic cells functioning as macrophages in the epidermis. • Engulf bacteria, foreign particles, and damaged cells to trigger an immune response. 4. Merkel Cells: • Receptor cells located in the deepest layer that function as touch receptors, associating with sensory nerve endings. Cells of the Epidermis Layers (Strata) of the Epidermis Layers (Strata) of the Epidermis 1. Stratum Basale (Basal Layer / Stratum Germinativum): • Deepest single layer; attached to the basement membrane and underlying dermis. • Forms a wavy boundary by interlocking with upward projections of the dermis called dermal papillae, increasing surface area and strengthening the epidermal-dermal bond to prevent shearing (enhancing grip). • The stratum basale is a single layer of cells primarily made of basal cells. • Site of continuous mitotic cell division (cuboidal stem cells) that continually produce new keratinocytes. • Houses melanocytes (pigment producers) and Merkel cells (touch receptors). 2. Stratum Spinosum ("Spiny Layer"): • 8 to 10 layers of keratinocytes connected by strong desmosomes, giving a spiny appearance under a microscope. • Contains maturing keratinocytes and Langerhans cells. • Keratinocytes in the stratum spinosum begin the synthesis of keratin and release a water-repelling glycolipid. https://www.flickr.com/photos/187096960@N06/51172620298 Layers (Strata) of the Epidermis 1. Stratum Basale (Basal Layer / Stratum Germinativum): • Deepest single layer; attached to the basement membrane and underlying dermis. • Forms a wavy boundary by interlocking with upward projections of the dermis called dermal papillae, increasing surface area and strengthening the epidermal-dermal bond to prevent shearing (enhancing grip). • The stratum basale is a single layer of cells primarily made of basal cells. • Site of continuous mitotic cell division (cuboidal stem cells) that continually produce new keratinocytes. • Houses melanocytes (pigment producers) and Merkel cells (touch receptors). 2. Stratum Spinosum ("Spiny Layer"): • 8 to 10 layers of keratinocytes connected by strong desmosomes, giving a spiny appearance under a microscope. • Contains maturing keratinocytes and Langerhans cells. • Keratinocytes in the stratum spinosum begin the synthesis of keratin and release a water-repelling glycolipid. https://www.flickr.com/photos/187096960@N06/51172620298 Layers (Strata) of the Epidermis 3. Stratum Granulosum ("Granular Layer"): • 3–5 layers deep; cells flatten and fill with keratin, keratohyalin granules, and lamellar granules (waterproofing glycolipids). • Organelles disintegrate and cell death occurs as cells are pushed further from the blood supply. 4. Stratum Lucidum ("Clear Layer"): • Thin, translucent layer of dead, flattened cells packed with eleidin. • Found only in thick skin (palms of hands and soles of feet). 5. Stratum Corneum ("Horny Layer"): • Superficial layer consisting of 15–30 layers of flat, dead, keratin-filled cells. • Provides a durable, waterproof barrier against microbes, dehydration, and mechanical abrasion; continuously sloughed off. Layers (Strata) of the Epidermis The Dermis: Regions & Structure General Characteristics: • The "core" of the cutaneous system; houses blood vessels, sweat glands, oil glands, hair follicles, and nerve endings. • Consists of two layers of connective tissue that compose an interconnected mesh of elastin and collagenous fibers, produced by fibroblasts. 1. Papillary Layer: • Upper 20% of the dermis; composed of loose areolar connective tissue with a loose meshwork of collagen and elastic fibers. • Features dermal papillae that project upward into the epidermis, forming unique epidermal ridges (fingerprints) that enhance grip. • Contains rich capillary loops that nourish the avascular epidermis via diffusion and help regulate body temperature and lymphatic capillaries. • Packed with sensory nerve endings, including Meissner corpuscles (receptors sensitive to light touch) and free nerve endings that detect pain and temperature. • 2. Reticular Layer: • Deeper, thicker 80% of the dermis; composed of dense irregular connective tissue. • Packed with thick bundles of collagen fibers (for structural strength and tensile resilience) and elastic fibers (for skin stretch and recoil). • Contains larger blood vessels, sweat/sebaceous glands, and Pacinian corpuscles (deep pressure receptors). Papillary layer also contains fibroblasts, some fat cells (adipocytes), and phagocytes. Meissner corpuscles https://neuroscientificallychallenged.com/glossary/meissners-corpuscles https://histology.siu.edu/intro/Meissners2.htm The Dermis: Regions & Structure • Papillary layer also contains fibroblasts, some fat cells (adipocytes), mast cells, and phagocytes. https://www.enhance-me-training.com/topic/the-dermis/ The Hypodermis (Subcutaneo us Layer) Position & Anatomy: • Located directly beneath the reticular layer of the dermis. • Technically not part of the skin proper, but rather a connective tissue layer that anchors the skin to underlying bone and muscle. • Composed primarily of loose areolar connective tissue and adipose tissue (fat cells). Vascular Supply: • Highly vascularized; contains large blood vessels that supply the skin and serve as a common site for subcutaneous injections (hypodermic needles). Primary Functions: • Energy Storage: Adipocytes store triglycerides as an energy reserve. • Insulation & Protection: The fat layer provides thermal insulation against heat loss and acts as a shock-absorbing cushion to protect underlying structures from mechanical trauma. Skin Pigmentation & Color Determinants 1. Melanin: • Produced by melanocytes; primary pigment determining skin color. • Exists in two primary forms: eumelanin (brown/black) and pheomelanin (red/yellow). • UV exposure stimulates tyrosinase enzyme activity, increasing melanin production (tanning) to shield cell nuclei from DNA damage. • Freckles and moles represent localized accumulations of melanin. 2. Carotene: • A yellow-orange pigment obtained from plant-based foods (e.g., carrots, sweet potatoes) that can accumulate in the stratum corneum and hypodermis. 3. Hemoglobin: • The red oxygen-transporting protein in red blood cells. • Imparts a pinkish or red tint to the skin as blood flows through the dermal capillaries, particularly visible in lighter-skinned individuals when oxygenated. Carotenodermia https://www.nejm.org/doi/abs/10.1056/NEJMicm950425 https://en.wikipedia.org/wiki/Jaundice https://www.azolifesciences.com/ Integumentary System Disorders Overview of Accessory Structures Definition: • Structures that originate from the epidermis and extend down into the dermis or hypodermis. Key Components: • Hair • Nails • Sweat (Sudoriferous) Glands • Sebaceous (Oil) Glands General Function: • While embedded in the skin, these structures play critical roles in protection, sensory input, thermoregulation, and excretion. https://www.mayoclinichealthsystem.org/ https://www.harleystreethairtransplants.org/ Hair Structure and Growth Anatomy of a Hair: • Shaft: The portion of the hair exposed above the skin surface (completely dead, keratinized cells). • Root: The portion of hair anchored within the follicle below the skin surface. • Hair Bulb: The expanded base of the root surrounding the hair papilla (which contains blood vessels and nerves). Layers of the Hair: • Medulla: The central core of the hair. • Cortex: The middle layer providing strength and pigment. • Cuticle: The outermost layer of overlapping, single cells protecting the inner layers. Follicle & Arrector Pili: • Surrounded by a root sheath and connected to an involuntary smooth muscle called the arrector pili, which contracts to pull hair upright ("goosebumps" in response to cold or fear) and is controlled by the sympathetic nervous system. • This traps a layer of air to add insulation https://www.toppik.com/ Internal Root Sheath Layers of the Hair Follicle External Root Sheath • Structure: Surrounds the growing hair root up to the hair shaft. • Origin: Derived from the basal cells of the hair matrix. Wall • Structure: Encloses the hair root as a direct extension of the epidermis. • Characteristics: Composed of basal cells at the base; becomes increasingly keratinous toward the upper regions. Glassy Membrane • Structure: A thick, clear connective tissue sheath covering the hair root. • Function: Connects the hair follicle directly to the surrounding dermal tissue. Root Hair Plexuses (Hair Follicle Receptors) • Histological Definition: Specialized networks of unmyelinated sensory nerve fibers that wrap intricately around and entwine within the external root sheath of hair follicles. • Anatomical Position: Located in the dermal portion of the hair follicle wall, typically positioned just inferior to the entrance of the sebaceous gland ducts. • Functional Role: Act as rapid-adapting mechanoreceptors (tactile receptors) responsible for detecting fine, light-touch stimuli. • Mechanism of Action: • Deflection of the hair shaft (from wind, clothing, or a crawling insect) acts as a mechanical lever. • Movement physically shifts the follicular wall and deforms the entwined nerve endings. • Mechanical deformation opens mechanically- gated ion channels, triggering action potentials that travel via sensory neurons to the central nervous system. • Clinical/Physiological Significance: Highly sensitive to initial directional movement, providing early cutaneous awareness of external environmental contact before deeper touch receptors are engaged. https://quizlet.com/ca/443370620/hair-and-nails-flash-cards/ https://www.nisenet.org/catalog/scientific-image-human-hair Hair Growth Cycle & Dynamics • Anagen Phase (Growth): Rapid cell division at the root pushes the hair shaft upward at ~0.3 mm/day; lasts 2 to 7 years. • Catagen Phase (Transition): A brief 2 to 3 week transitional period marking the end of active follicular growth. • Telogen Phase (Resting): Lasts 2 to 4 months with no new growth, culminating in a new anagen phase that sheds the old hair. • Shedding & Loss: Average daily loss is 50 hairs; excessive loss exceeding replacement results from aging, hormonal fluctuations, or dietary changes. https://www.pinterest.com/pin/halloween-hair--417638565445540250/ Sweat (Sudoriferous) Glands Function: • Produce sweat to cool the body via evaporative cooling and excrete metabolic wastes. 1. Eccrine (Merocrine) Sweat Glands: • More common; distributed across nearly the entire skin surface (especially palms, soles, and forehead). • Produce a hypotonic fluid (water, salts, metabolic wastes) released via exocytosis directly onto the skin surface for thermoregulation. 2. Apocrine Sweat Glands: • Confined to areas with hair follicles (e.g., armpits and genital regions). • Larger glands that release a thicker, organic-rich (in addition to water and salts) secretion into hair follicles, which is metabolized by bacteria to produce body odor; become active starting at puberty. • The release of this sweat is under both nervous and hormonal control https://en.wikipedia.org/wiki/Apocrine_sweat_gland Sebaceous (Oil) Glands Definition: • Exocrine glands associated with hair follicles found all over the body except on the palms and soles. Secretion (Sebum): • Produce sebum, a mixture of lipids, cholesterol, and proteins. Functions of Sebum: • Lubricates and waterproofs the skin and hair, preventing them from drying out. • Possesses antibacterial properties to inhibit the growth of microorganisms on the skin surface. Mode of Secretion: • Holocrine secretion: cells accumulate sebum until they rupture and destroy themselves, releasing their product (replaced by mitotic division of basal cells). https://quizlet.com/ca/443370620/hair-and-nails-flash-cards/ Nails Structure & Composition: • Specialized accessory structures composed of densely packed, dead, heavily keratinized epidermal cells. Key Anatomical Features: • Nail Body (Plate): The visible hard plate covering the dorsal surface of the fingertip/toe. • Nail Bed: The specialized skin underlying the nail body, richly supplied with blood vessels (giving it a pink color). • Nail Root: The deep epidermal fold under the skin where nail production begins. • Eponychium (Cuticle): The fold of epithelial tissue that overlaps the proximal edge of the nail body. • Lunula: The thick, crescent-shaped whitish area at the base of the nail body overlying the thick nail matrix. Primary Functions: • Protects the distal tips of fingers and toes from trauma and enhances precision grip for picking up small objects. Overview of Integumentary Functions Primary Role: • The skin and its accessory structures function as an integrated organ system that maintains homeostasis and protects the body. Core Physiological Functions: • Protection: Acts as a physical and chemical barrier against external elements. • Sensation: Detects environmental stimuli via specialized receptors. • Thermoregulation: Modulates body temperature through sweat and blood vessel adjustments. • Vitamin D Synthesis: Produces a crucial hormone essential for calcium absorption. Protection (The Body's Armor) Physical & Chemical Barrier: • Protects underlying vital organs from mechanical injury, UV radiation, wind, and water. Dehydration Prevention: • Layers of tough keratin and water-resistant glycolipids in the stratum corneum prevent excessive fluid loss. Microbial Defense: • Acts as a first line of defense against pathogens, abrasive grit, and harmful chemicals. • Sweat contains dermcidin, which possesses antibiotic properties to deter microbe over-colonization. Immune Protection: • Langerhans (dendritic) cells patrol epidermal layers to intercept foreign invaders and trigger immune responses. https://uen.pressbooks.pub/anatomyphysiology/chapter/epidermis/ Langerhan s (Dendritic) Cells (APC’s) https://courses.lumenlearning.com/wm-biology2/chapter/antigen-presenting-cells/ Sensation (Sensory Function) Environmental Awareness: • The integumentary system contains a rich network of specialized nerve endings and receptors across the epidermis, dermis, and hypodermis. Key Sensory Receptors: • Meissner (Tactile) Corpuscles: Highly concentrated in fingertips; respond to light touch. • Pacinian (Lamellated) Corpuscles: Detect deep pressure and vibration. • Merkel Cells & Hair Root Plexuses: Detect fine touch and minor hair disturbances (e.g., sensing an insect crawling on the skin). Pain & Temperature: • Free nerve endings distributed throughout the skin monitor noxious stimuli, temperature shifts, and physical trauma. Sensation (Sensory Function) • Merkel cells (Tactile discs): Located in the deep layer of the epidermis (stratum basale), these are slow-adapting receptors that excel at detecting sustained touch, fine detail, texture, and edges. When pressed, they release signaling molecules that excite adjacent nerve endings, providing high-resolution tactile feedback (like reading Braille or feeling a smooth surface). • Meissner corpuscles (Tactile corpuscles): Situated in the dermal papillae of hairless (glabrous) skin, such as your fingertips and lips, these are rapid-adapting receptors. They fire intensely when skin first makes contact with an object and when it loses contact, making them exceptionally sensitive to light touch, low-frequency vibration, and slippage (helping you adjust your grip on a moving object). • Pacinian corpuscles (Lamellar corpuscles): Found deep in the dermis and subcutaneous layer, these large, onion-shaped receptors are rapidly adapting and exquisitely sensitive to deep pressure and high-frequency vibration. Because of their layered capsule, steady pressure is filtered out, allowing them to fire only when vibration or sudden mechanical shifts occur (such as feeling a drill vibrate or walking on a rough surface). • Hair root plexus (Hair follicle receptors): A web of sensory nerve fibers wrapped around the base of hair follicles. These rapid-adapting mechanoreceptors detect the bending or movement of hairs. Even a light breeze or an insect crawling across your arm displaces a hair, triggering the surrounding nerve plexus and providing an early warning system for tactile movement across hairy skin. Pacinian Corpuscle (Sensory Organ) Pacinian Corpuscle Anatomy: Encapsulated, onion-like mechanoreceptor for deep pressure and vibration. • The Capsule & Outer Lamination: Dense connective tissue outer envelope and flattened lamellar cells that filter out steady pressure. • Viscous Gel: Interstitial fluid between layers that shifts hydraulically to dampen sustained forces, driving rapid adaptation. • Inner Lamination: Tightly packed, specialized modified Schwann cells forming a core around the central nerve terminal. • Terminal Non-Myelinated Axon: Bare, uninsulated nerve tip at the center with stretch-sensitive channels that trigger action potentials when compressed. • Myelinated Axon: Insulated nerve fiber exiting the corpuscle to rapidly transmit electrical impulses toward the central nervous system via saltatory conduction. Thermoregulation Sympathetic Nervous System Control : The integumentary system works closely with the autonomic nervous system (involuntary bodily control) to continuously monitor and adjust core body temperature. Response to Overheating (Cooling): • Sweating: Eccrine sweat glands secrete water and electrolytes; evaporative cooling dissipates body heat. (Note: insensible perspiration secretes ~500 mL/day even without noticeable sweating). • Vasodilation: Dermal blood vessels dilate to bring warm blood closer to the body surface, releasing heat into the environment. Response to Cold (Heat Retention): • Vasoconstriction: Dermal arterioles constrict to minimize blood flow to the skin surface, trapping core heat internally (can cause a pale/whitish hue). • Shivering: Involuntary muscle contractions generate metabolic heat (assisted by the contraction of arrector pili muscles). Vitamin D Synthesis The Pathway: • 1. Skin Activation: When epidermal cells are exposed to ultraviolet (UV) radiation, a cholesterol derivative in the skin converts into cholecalciferol (Vitamin 3). • 2. Liver Processing: The liver converts cholecalciferol into an intermediate compound called calcidiol. • 3. Kidney Activation: The kidneys convert calcidiol into calcitriol, which is the active, functional hormone form of Vitamin D. Physiological Importance: • Calcitriol is essential for the normal intestinal absorption of calcium and phosphorus, which are strictly required for bone health, growth, and remodeling. https://www.researchgate.net/ Effects of Aging on the Integumentary System Epidermal & Dermal Changes: • Mitotic activity in the stratum basale slows down, causing the epidermis to thin. • The dermis exhibits a reduced ability to regenerate, leading to a loss of structural elasticity and flexibility (manifesting as wrinkles). • Fibroblast activity declines, resulting in decreased production of collagen and elastic fibers. Vascular & Glandular Decline: • Blood supply to the skin decreases, reducing the skin's capacity to heal quickly and impairing thermoregulation (leading to increased sensitivity to cold). • Functional activity of sweat (sudoriferous) and sebaceous (oil) glands drops, causing dry, scaly skin and a reduced ability to sweat effectively. Subcutaneous & Accessory Alterations: • The hypodermis loses fat storage over time, contributing to a loss of padding, insulation, and a sunken appearance. • Melanocyte and hair follicle activity slows down, resulting in graying or thinning hair and a reduced capacity to protect against UV radiation. • Immune responsiveness declines as the number of Langerhans cells drops, increasing susceptibility to skin infections and damage. Overview of Skin Cancer Definition & Cause: • Cancer caused by abnormal, uncontrollable cell division in the skin. • Primary culprit is overexposure to ultraviolet (UV) radiation from the sun or tanning beds, which damages cellular DNA. The Danger of Metastasis: • Metastasis is the process where cancer cells break away from the primary tumor, enter the bloodstream or lymphatic vessels, and spread to secondary sites (such as lymph nodes, lungs, or liver), making treatment significantly more difficult. Types of Skin Cancer: • Basal Cell Carcinoma (BCC): Starts in the stratum basale and spreads along that boundary; the most common form of skin cancer, highly curable with early treatment (common in areas exposed to the sun). • Treatments include surgery, freezing (cryosurgery), and topical ointments • Squamous Cell Carcinoma (SCC): Affects keratinocytes of the stratum spinosum; presents as lesions on the scalp, ears, and hands; more aggressive than BCC and can metastasize if left untreated. • Surgery and radiation are used to cure SCC • Melanoma: Uncontrolled growth of melanocytes, typically developing from a mole; the most fatal form of skin cancer due to high rates of metastasis. • Treatment typically involves surgical excision and immunotherapy Basal Cell Carcinoma Squamous Cell Carcinoma Melanoma Early Detection of Melanoma (The ABCDE Rule) Clinical Screening Guidelines: • A – Asymmetry: The two sides of the mole or lesion do not match. • B – Borders: The edges are irregular, ragged, notched, or blurred. • C – Color: The color is not uniform and may include different shades of brown or black, or patches of pink, red, white, or blue. • D – Diameter: The lesion is larger than 6 mm (about the size of a pencil eraser), though melanomas can sometimes be smaller. • E – Evolving: The mole is changing in size, shape, color, or elevation, or begins to bleed/itch. Common Skin Disorder s Introduction to Skin Disorders: • Skin disorders range from minor localized irritations to chronic systemic conditions, often involving inflammation, immune responses, or blocked glands. • Disorders include psoriasis, cold sores, impetigo, scabies, hives, and warts. Eczema: • An inflammatory, allergic condition that presents as dry, red, itchy patches resembling rashes. • Often accompanied by swelling, flaking, and skin cracking; managed with moisturizers, corticosteroid creams, and immunosuppressants. Acne: • A skin disturbance involving the overproduction of sebum and keratin that blocks hair follicles. • Most common during puberty due to hormonal surges (androgens) that stimulate sebaceous glands, leading to bacterial infection and inflammation. Skin Injuries & The Healing Process Types of Injuries: • Cuts, punctures, scrapes, and burns caused by physical trauma, heat, chemicals, or electricity. • Step-by-Step Wound Healing Stages: 1. Hemostasis & Clotting: A blood clot forms immediately to stop bleeding and eventually dries into a protective scab. 2. Inflammation: White blood cells (macrophages) clear out debris and fight potential infection. 3. Proliferation: Fibroblasts migrate into the wound bed to produce new collagen and blood vessels (granulation tissue). 4. Remodeling & Scarring: Epithelial cells regenerate across the wound under the scab, while scar tissue (dense collagen) replaces normal tissue depending on the depth of the injury. https://www.shieldhealthcare.com/ https://jetem.org/thermal_burns/ Burns and Classification s Nature of Burns: • Caused by intense heat, radiation, electricity, or chemicals, resulting in massive cell death and fluid loss. Severity Classifications: • First-Degree (Superficial): Affects only the epidermis; results in redness and minor pain (e.g., mild sunburn) that heals within days. • Second-Degree (Partial-Thickness): Damages both the epidermis and upper dermis; results in blistering and significant pain. • Third-Degree (Full-Thickness): Destroys the full thickness of the skin (epidermis and dermis), charring tissue and destroying nerve endings (often requiring skin grafts). • Fourth-Degree (Full-Thickness with Deep Tissue Damage): Extends completely through the skin down to underlying muscle, tendons, and bone; requires extensive surgical intervention and often amputation. Major Systemic Risks: • Severe dehydration, electrolyte imbalance, renal/circulatory failure, and rampant secondary infections due to lost skin barrier function. Fourth degree Burn https://burncenters.com/burns/evaluate-a-burn/ Common Integumentary Abnormalities and Injury Responses Scars & Keloids: • Scars: Formed when the skin repairs deep dermal damage using collagen-rich connective tissue rather than regenerating normal tissue. • Lacks accessory structures (e.g., hair follicles, sweat glands, and sebaceous glands) • Keloids: Result from an overproduction of scar tissue (collagen) that extends beyond the original boundaries of the wound. Bedsores (Decubitus Ulcers): • Caused by constant, long-term pressure on bony areas that cuts off blood supply to the skin, leading to tissue necrosis and breakdown. Stretch Marks (Striae): • Occur when the dermis is stretched beyond its elastic limits (e.g., during rapid growth, weight gain, or pregnancy), causing collagen and elastin fibers to tear. Calluses & Corns: • A protective response where the stratum basale increases mitotic activity in areas subjected to constant friction or pressure, resulting in a thickened, hardened layer of dead cells. https://www.healthline.com/health/keloid-ear https://www.mayoclinic.org/diseases-conditions/corns-and- calluses/multimedia/callus/img-20007285 https://myexpertmidwife.com/blogs/my-expert-midwife/stretch-marks-101 https://blog.xoxoday.com/empuls/get-to-know-you-questions-for-coworkers/

Topic Set 5: Melanin & Skin Pigmentation

Chapter 4 Skin and Body Membranes Body Membranes Functions of body membranes Cover body surfaces Line body cavities Form protective sheets around organs Classified according to tissue types Body Membranes Two major categories Epithelial membranes Cutaneous membranes Mucous membranes Serous membranes Connective tissue membranes Synovial membranes Epithelial Membranes Epithelial membranes are simple organs Also called covering and lining membranes These membranes contain both: Epithelial tissue layer Connective tissue layer Epithelial Membranes Cutaneous membrane = skin Dry membrane Outermost protective boundary Consists of two layers Epidermis is composed of keratinized stratified squamous epithelium Dermis is mostly dense (fibrous) connective tissue Epithelial Membranes • Mucous membranes (mucosae) • I Moist membranes Some mucosae secrete protective, lubricating mucus Line all body cavities that open to the exterior body surface • Adapted for absorption or secretion • ' Consists of two layers • Epithelium type depends on site • Loose connective tissue (lamina propria) Epithelial Membranes Serous membranes (serosae) Line compartments in the ventral body cavity that are ciosed to the exterior of the body Occur in pairs, separated by serous fluid, with a visceral and parietal layer Consists of two layers Simple squamous epithelium Areolar connective tissue Epithelial Membranes Specific serous membranes Peritoneum Cover organs in the abdominal cavity Pleurae Surround the lungs Pericardia Surround the heart Connective Tissue Membranes Synovial membranes Loose areolar connective tissue only (no epithelial tissue) Line fibrous capsules surrounding joints Line bursae Line tendon sheaths Secrete a lubricating fluid to cushion organs moving against each other during muscle activity Integumentary System Integumentary system consists of the: Skin (cutaneous membrane) Skin appendages Sweat glands Oil glands Hair Nails Functions of the Integumentary System Insulates and cushion deeper body organs Protects the entire body from: Mechanical damage (bumps and cuts) Chemical damage (acids and bases) Thermal damage (heat or cold) Ultraviolet (UV) radiation (sunlight) Microbes (bacteria) • Water loss Functions of the Integumentary System Regulates heat loss as controlled by the nervous system Acts as a mini-excretory system; sweat aids in the loss of Urea Salts Water Synthesizes vitamin D Secretions create a protective acid mantle Structure of the Skin Two kinds of tissue compose the skin Epidermis Dermis Subcutaneous tissue (hypodermis) Anchors the skin to underlying organs Not technically part of the integumentary system Composed mostly of adipose tissue Serves as a shock absorber and insulates deeper tissues Structure of the Skin Epidermisouter layer Composed of stratified squamous epithelium Most cells are keratinocytes which produce a fibrous protein called keratin Keratinization makes the epidermis tough Desmosomes connect keratinocytes together Avascular Composed of five layers (strata) Structure of the Skin Summary of strata (layers) of the epidermis from deepest to most superficial Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum (thick, hairless skin only) Stratum corneum Structure of the Skin Stratum basale (stratum germinativum) Deepest layer of epidermis Lies next to dermis Wavy borderline with the dermis anchors the two together Cells undergoing mitosis Daughter cells are pushed upward to become the more superficial layers Stratum spinosum Cells become increasingly flatter and more keratinized Structure of the Skin Stratum granulosum Stratum lucidum Formed from dead cells of the deeper strata Occurs only in thick, hairless skin of the palms of hands and soles of feet Stratum corneum Outermost layer of epidermis Shingle-like dead cells are filled with keratin (protective protein prevents wat loss from skin Structure of the Skin Melanin Melanin is a pigment produced by melanocytes Melanocytes are mostly in the stratum basale of the epidermis Color is yellow to brown to black Structure of the Skin Epidermal dendritic cells Alert and activate immune cells to a threat (bacterial or viral invasion) Merkel cells Associated with sensory nerve endings Serve as touch receptors called Merkel discs Structure of the Skin Dermis Connective tissue Underlies the epidermis Two regions Papillary Reticular Structure of the Skin Two regions of the dermis Papillary layer (upper dermal region) contain projections called dermal papillae Areolar connective tissue Indent the epidermis above Many projections contain capillary loops, and others house pain and touch receptors On palm and sole surfaces, papillae increase friction and gripping ability Fingerprints are identifying films of sweat Structure of the Skin Two regions of the dermis Reticular layer (deepest skin layer) Dense irregular connective tissue Blood vessels Sweat and oil glands Deep pressure receptors (lamellar corpuscles) Structure of the Skin Other dermal features Cutaneous sensory receptors Phagocytes Collagen and elastic fibers Blood vessels I Nerve supply Skin Color • Three pigments contribute to skin color 1. Melanin • Yellow, reddish brown, or black pigments 2. Carotene • Orange-yellow pigment (also found in some vegetables) 3. Hemoglobin Red coloring from blood cells in dermal capillaries Oxygen content determines the extent of red coloring Skin Color Redness (erythema) due to embarrassment, inflammation, hypertension, fever, or allergy Pallor (blanching) due to emotional stress (such as fear), anemia, low blood pressure, impaired blood flow to an area Jaundice (yellow cast)-indicates a liver disorder • Bruises (black and blue marks)-hematomas Appendages of the Skin Cutaneous glands are all exocrine glands Sebaceous glands Sweat glands Hair and hair follicles Nails Appendages of the Skin Sebaceous (oil) glands Located all over the skin except for palms and soles Produce sebum (oil) Makes skin soft and moist Prevents hair from becoming brittle Kills bacteria Most have ducts that empty into hair follicles; others open directly onto skin surface Glands are activated at puberty with increased androgens Appendages of the Skin Sweat (sudoriferous) glands Produce sweat Widely distributed in skin Two types of sudoriferous glands Eccrine glands Apocrine glands Appendages of the Skin Eccrine glands More numerous, located all over the body Open via duct to sweat pores on the skin's surface Produce acidic sweat Water, salts, vitamin C, traces of metabolic waste Function in body temperature regulation Appendages of the Skin Apocrine glands Ducts empty into hair follicles in the armpit and genitals Begin to function at puberty Release sweat that also contains fatty acids and proteins (milky or yellowish color) • Play a minimal role in body temperature regulation Appendages of the Skin Hair Located body-wide except for palms, soles, nipples, lips Produced by hair follicle Root is enclosed in the follicle Shaft projects from the surface of the scalp or skin Consists of hard keratinized epithelial cells Melanocytes provide pigment for hair color Hair grows in the matrix of the hair bulb in stratum basale Appendages of the Skin Hair anatomy Central medulla Cortex surrounds medulla Cuticle on outside of cortex Most heavily keratinized region of the hair Melanin provides color Appendages of the Skin Associated hair structures Hair follicle Composed of an inner epithelial root sheath andan outer fibrous sheath Dermal region provides a blood supply to the hair bulb (deepest part of the follicle) Arrector pili muscle connects to the hair follicle to pull hairs upright when we are cold or frightened Appendages of the Skin Nails Heavily keratinized, scalelike modifications of the epidermis Stratum basale extends beneath the nail bed, which is responsible for growth Lack of pigment makes nails colorless Appendages of the Skin Parts of a nail Free edge Body is the visible attached portion Nail folds are skin folds that overlap the edges of the nail; the cuticle is the proximal edge Root of nail is embedded in skin Growth of the nail occurs from nail matrix of nail bed Homeostatic Imbalances of Skin Infections and allergies Athlete's foot Caused by fungal infection (Tinea pedis) Itchy, red peeling skin between the toes Boils (furuncles) and carbuncles Caused by inflammation of hair follicles Carbuncles are clusters of boils caused by bacteria Cold sores (fever blisters) Caused by human herpesvirus 1 Blisters itch and sting Homeostatic Imbalances of Skin Infections and allergies Contact dermatitis Caused by exposure to chemicals that provoke allergic responses Itching, redness, and swelling of the skin Impetigo Caused by bacterial infection Pink, fluid-filled raised lesions around mouth/nose Psoriasis Triggered by trauma, infection, hormonal changes, or stress Red, epidermal lesions covered with dry, silvery scales that itch, burn, Crack, or sometimes bleed Homeostatic Imbalances of Skin • Burns Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals Associated dangers Protein denaturation and cell death Dehydration and electrolyte imbalance Circulatory shock Result in loss of body fluids and infection from the invasion of bacteria Homeostatic Imbalances of Skin Extent of a burn is estimated using the rule of nines Body is divided into 11 areas for quick estimation Each area represents about 9 percent of total body surface area The area surrounding the genitals (the perineum) represents 1 percent of body surface area Homeostatic Imbalances of Skin . First-degree burn (superficial burn) Only epidermis is damaged Skin is red and swollen Second-degree burn (superficial partial-thickness burn) Epidermis and superficial part of dermis are damaged Skin is red, painful, and blistered Regrowth of the epithelium can occur Homeostatic Imbalances of Skin Third-degree burn (full-thickness burn) Destroys epidermis and dermis; burned area is painless Requires skin grafts, as regeneration is not possible Burned area is blanched (gray-white) or black Fourth-degree burn (full-thickness burn) Extends into deeper tissues (bone, muscle, tendons) Appears dry and leathery Requires surgery and grafting May require amputation Homeostatic Imbalances of Skin Criteria for deeming burns critical (if any one is met): Over 30 percent of body has second-degree burns Over 10 percent of the body has third-or fourth-degree burns Third-or fourth-degree burns of the face, hands, feet, or genitals Burns affect the airways Circumferential (around the body or limb) burns have occurred Homeostatic Imbalances of Skin Skin cancer Most common form of cancer in humans Most important risk factor is overexposure to ultraviolet (V) radiation in sunlight and tanning beds Cancer can be classified two ways Benign means the neoplasm (tumor) has not spread Malignant means the neoplasm has invaded other body areas Concept Link Recall that mitosis gone wild is the basis for cancer (Chapter 3, pp. 82-83). These cells lack normal control of cell division and divide quickly, resulting in errors during DNA replication, mitosis, or both. Cells experiencing rapid, uncontrolled growth become cancerous and can metastasize (spread) to other parts of the body. Homeostatic Imbalances of Skin . First-degree burn (superficial burn) Only epidermis is damaged Skin is red and swollen Second-degree burn (superficial partial-thickness burn) Epidermis and superficial part of dermis are damaged Skin is red, painful, and blistered Regrowth of the epithelium can occur Homeostatic Imbalances of Skin Third-degree burn (full-thickness burn) Destroys epidermis and dermis; burned area is painless Requires skin grafts, as regeneration is not possible Burned area is blanched (gray-white) or black Fourth-degree burn (full-thickness burn) Extends into deeper tissues (bone, muscle, tendons) Appears dry and leathery Requires surgery and grafting May require amputation Homeostatic Imbalances of Skin Criteria for deeming burns critical (if any one is met): Over 30 percent of body has second-degree burns Over 10 percent of the body has third-or fourth-degree burns Third-or fourth-degree burns of the face, hands, feet, or genitals Burns affect the airways Circumferential (around the body or limb) burns have occurred Homeostatic Imbalances of Skin Skin cancer Most common form of cancer in humans Most important risk factor is overexposure to ultraviolet (V) radiation in sunlight and tanning beds Cancer can be classified two ways Benign means the neoplasm (tumor) has not spread Malignant means the neoplasm has invaded other body areas Concept Link Recall that mitosis gone wild is the basis for cancer (Chapter 3, pp. 82-83). These cells lack normal control of cell division and divide quickly, resulting in errors during DNA • One or more of the ABCD characteristics is evolving Developmental Aspects of Skin and Body Membranes Lanugo, a downy hair, covers the body by the fifth or sixth month of fetal development but disappears by birth Vernix caseosa, an oily covering, is apparent at birth Milia, small white spots, are common at birth and disappear by the third week Acne may appear during adolescence Pimples, scales, and dermatitis are more common with aging skin Developmental Aspects of Skin and Body Membranes In youth, skin is thick, resilient, and well hydrated With aging, skin loses elasticity and thins Skin cancer is a major threat to skin exposed to excessive sunlight Balding (alopecia) and/or graying occurs with aging; both are genetically determined other factors that may contribute include drugs and emotional stress

04 Melatonin

Melanin and Skin Color

Melanin Storyline: Lessons 1-2

Melanin Storyline: Introduction to Genetics

Study Guide Module 2 MODULE 2 STUDY GUIDE The Integumentary System ⸻ CHAPTER 1: OVERVIEW OF THE INTEGUMENTARY SYSTEM Components of the Integumentary System The integumentary system consists of: * Skin * Hair * Nails * Sweat glands * Sebaceous glands The skin is the largest organ in the body. Functions of the Integumentary System 1. Protection 2. Sensation 3. Thermoregulation 4. Vitamin D synthesis 5. Communication ⸻ CHAPTER 2: LAYERS OF THE SKIN The skin has two major layers: Epidermis * Superficial layer * Keratinized stratified squamous epithelium * Avascular Dermis * Deeper layer * Connective tissue * Contains blood vessels, nerves, glands, and hair follicles Hypodermis * Not technically part of the skin * Also called subcutaneous layer * Contains adipose tissue Functions: * Energy storage * Cushioning * Insulation * Anchoring skin ⸻ CHAPTER 3: EPIDERMIS Cell Types Keratinocytes * Most abundant cells * Produce keratin Melanocytes * Produce melanin * Protect against UV radiation Tactile (Merkel) Cells * Touch receptors Dendritic Cells * Immune defense * Phagocytize pathogens ⸻ EPIDERMAL LAYERS Deep → Superficial Stratum Basale * Deepest layer * Single layer of cuboidal cells * Contains stem cells * Contains melanocytes * Contains tactile cells * Site of mitosis Stratum Spinosum * 8–10 layers thick * Contains dendritic cells * Connected by desmosomes Stratum Granulosum * 3–5 layers * Keratinization begins * Cells flatten * Organelles begin breaking down Stratum Lucidum * Only in thick skin * Palms and soles * Dead transparent cells Stratum Corneum * 15–30 layers * Dead keratinized cells * Protection from abrasion * Prevents dehydration ⸻ THICK VS THIN SKIN Thick Skin Found on: * Palms * Soles Contains: * Stratum lucidum Thin Skin Found everywhere else Does not contain: * Stratum lucidum ⸻ EPIDERMAL WATER BARRIER Located between: * Stratum spinosum * Stratum granulosum Functions: * Waterproofing * Prevents dehydration * Prevents excess water entry Components: 1. Filaggrin 2. Lamellar proteins 3. Lamellar lipids 4. Tight junction proteins ⸻ CHAPTER 4: DERMIS Made of connective tissue. Papillary Layer Contains: * Areolar connective tissue * Dermal papillae * Capillaries * Tactile corpuscles (Meissner corpuscles) Function: * Light touch sensation Reticular Layer Contains: * Dense irregular connective tissue * Hair follicles * Sweat glands * Sebaceous glands * Arrector pili muscles * Lamellated (Pacinian) corpuscles Function: * Deep pressure * Vibration sensation ⸻ DERMAL FIBERS Collagen Provides: * Strength * Support * Water retention Elastin Provides: * Elasticity * Stretching ability ⸻ CHAPTER 5: PIGMENTATION Melanin Produced by: * Melanocytes Functions: * Skin color * UV protection Effects of UV Exposure UV stimulates: * Keratinocytes * Melanocytes Result: * Increased melanin production * Tanning ⸻ Disorders of Pigmentation Albinism Cause: * Lack of melanin production Effects: * Pale skin * Light sensitivity * Increased skin cancer risk Vitiligo Cause: * Loss of melanocyte activity Effects: * White patches on skin ⸻ CHAPTER 6: FUNCTIONS OF THE SKIN Protection Protects against: * Microorganisms * Chemicals * UV radiation * Water loss * Physical trauma Dermicidin: * Antimicrobial substance in sweat ⸻ Sensory Function Skin detects: * Touch * Pain * Temperature * Pressure * Vibration Receptors Meissner Corpuscles * Light touch Pacinian Corpuscles * Deep pressure * Vibration Tactile Cells * Touch Hair Root Plexus * Detects hair movement ⸻ Thermoregulation When Body Is Hot Blood vessels: * Dilate Sweat glands: * Increase secretion Result: * Cooling When Body Is Cold Blood vessels: * Constrict Result: * Conserves heat Can lead to: * Frostbite ⸻ Vitamin D Synthesis UV exposure stimulates vitamin D production. Vitamin D helps: * Calcium absorption * Bone health * Immune function Deficiency causes: Rickets Children Osteomalacia Adults ⸻ Communication Examples: * Facial expressions * Goosebumps * Sweating * Hair patterns ⸻ CHAPTER 7: HAIR Hair Structure Hair Shaft Visible portion Hair Root Embedded portion Hair Follicle Surrounds root Hair Bulb Growth region Hair Matrix Mitotic cells Hair Papilla Blood supply ⸻ Hair Layers 1. Medulla 2. Cortex 3. Cuticle ⸻ Hair Functions * Protection * Thermoregulation * Sensation * Communication ⸻ Hair Growth Average: * 0.3 mm/day Normal loss: * About 50 hairs/day ⸻ Hair Color Determined by: * Melanin Gray hair: * Reduced melanin production ⸻ Arrector Pili Muscle Functions: * Causes goosebumps * Helps retain heat Controlled by: * Sympathetic nervous system ⸻ Alopecia Definition: * Hair loss Pattern baldness: * Hormonal and genetic ⸻ CHAPTER 8: NAILS Functions: * Protection * Support for grasping Structures: * Nail body * Nail root * Nail matrix * Nail bed * Lunula * Cuticle (eponychium) * Hyponychium ⸻ CHAPTER 9: GLANDS Eccrine Sweat Glands Location: * Most of body Functions: * Thermoregulation Secrete: * Water * Salt * Waste products ⸻ Apocrine Sweat Glands Location: * Armpits * Genital regions Characteristics: * Empty into hair follicles * Produce odor after bacterial breakdown ⸻ Sebaceous Glands Produce: * Sebum Functions: * Lubricates skin * Waterproofs skin * Prevents drying * Antibacterial effects ⸻ CHAPTER 10: SKIN CANCER Basal Cell Carcinoma Origin: * Stratum basale Characteristics: * Most common * Least likely to metastasize ⸻ Squamous Cell Carcinoma Origin: * Stratum spinosum Characteristics: * More aggressive * Can metastasize ⸻ Melanoma Origin: * Melanocytes Characteristics: * Most deadly * Highly metastatic ABCDE Rule A = Asymmetry B = Border irregularity C = Color variation D = Diameter > 6 mm E = Evolving ⸻ CHAPTER 11: SKIN DISORDERS Eczema Symptoms: * Dry skin * Itching * Rash * Inflammation Treatment: * Moisturizers * Corticosteroids ⸻ Acne Cause: * Excess sebum * Keratin buildup * Bacterial infection Common locations: * Face * Chest * Back ⸻ CHAPTER 12: WOUND HEALING Steps: 1. Clot Formation Stops bleeding 2. Scab Formation 3. Fibroblast Activity Produces collagen 4. Capillary Growth 5. Epidermal Repair ⸻ CHAPTER 13: BURNS First-Degree Burn Damage: * Epidermis only Symptoms: * Redness * Pain ⸻ Second-Degree Burn Damage: * Epidermis + part of dermis Symptoms: * Blisters * Swelling * Pain ⸻ Third-Degree Burn Damage: * Epidermis * Dermis * Hypodermis Characteristics: * Nerve destruction * Often painless initially * Requires grafting ⸻ Rule of Nines Head and neck = 9% Each arm = 9% Each leg = 18% Trunk = 36% Genitalia = 1% ⸻ CHAPTER 14: SCARS Scar Tissue Produced by: * Fibroblasts Contains: * Collagen Lacks: * Hair follicles * Sweat glands * Sebaceous glands ⸻ Keloid Raised scar due to excessive collagen Atrophic Scar Sunken scar Examples: * Acne scars * Chickenpox scars ⸻ CHAPTER 15: PRESSURE AND FRICTION INJURIES Bedsores Cause: * Prolonged pressure Result: * Reduced blood flow * Tissue death ⸻ Stretch Marks Cause: * Rapid growth * Pregnancy * Weight gain ⸻ Calluses Cause: * Repeated friction Result: * Thickened epidermis ⸻ Corns Specialized calluses ⸻ Blisters Cause: * Friction Result: * Fluid accumulation between skin layers ⸻ CHAPTER 16: AGING AND THE INTEGUMENTARY SYSTEM Changes: Epidermis * Thinner * Slower cell division Dermis * Less collagen * Less elastin * Slower healing Hypodermis * Fat redistribution * Less cushioning Hair * Thinner * Grayer Nails * Slower growth * More brittle Glands * Less sweat * Less sebum Skin * Wrinkles * Sagging * Dryness ⸻ HIGH-YIELD EXAM FACTS Epidermal Layers Basale → Spinosum → Granulosum → Lucidum → Corneum Touch Receptors * Meissner = Light touch * Pacinian = Pressure/Vibration Pigment Cell * Melanocyte Immune Cell * Dendritic Cell Touch Cell * Merkel (Tactile) Cell Cancer Origins * Basal Cell Carcinoma = Stratum Basale * Squamous Cell Carcinoma = Stratum Spinosum * Melanoma = Melanocytes Sweat Glands * Eccrine = Cooling * Apocrine = Odor Burn Depths * 1st = Epidermis * 2nd = Epidermis + Dermis * 3rd = Epidermis + Dermis + Hypodermis Vitamin D Deficiency * Rickets * Osteomalacia This should cover essentially all of the major concepts from the four readings and is the type of material most likely to appear on a Module 2 Anatomy & Physiology exam

1. Cell Transport Brownian Movement Definition: Random movement of particles caused by their inherent kinetic energy. Occurs above freezing temperatures. Passive process (requires no energy/ATP). Responsible for constant molecular motion. Diffusion Definition: Movement of molecules or ions from an area of higher concentration to lower concentration. Passive transport Moves down the concentration gradient No energy required Facilitated Diffusion Definition: Diffusion through a selectively permeable membrane using membrane proteins. Passive transport High → Low concentration Only certain substances can pass Filtration Definition: Movement of water and dissolved substances through a membrane from higher pressure to lower pressure. Driven by pressure differences Dialysis Definition: Separation of small molecules from larger molecules. Used in dialysis machines Not a normal transport process in the body 2. Active Transport Active Transport Definition: Transport requiring cellular energy (ATP). Endocytosis ("Into the Cell") Phagocytosis Cell Eating Engulfs solid particles Example: White blood cells engulfing bacteria Pinocytosis Cell Drinking Engulfs fluids Exocytosis Definition: Movement of substances out of the cell. 3. Epithelial Tissue Characteristics Covers body surfaces Lines organs and cavities Cells are tightly packed High mitotic rate Connected to connective tissue by a basement membrane Classification by Shape Shape Name Flat Squamous Cube-shaped Cuboidal Tall/elongated Columnar Classification by Layers Layers Name One layer Simple Two or more layers Stratified Example: Simple Columnar Epithelium = One layer of elongated cells 4. Connective Tissue Components Connective tissue contains: Cells Fibers Ground substance Fibers + Ground Substance = Matrix Loose Connective Tissue Areolar Tissue Supports organs Widely spaced fibers Adipose Tissue Fat tissue Insulation Energy storage Reticular Tissue Found in lymph nodes and spleen Acts as a filtering framework Dense Connective Tissue Dense Regular Fibers run in one direction Found in: Tendons Ligaments Aponeuroses Dense Irregular Fibers run in multiple directions Found in: Dermis of skin Elastic Connective Tissue Allows stretching Found in: Walls of arteries Elastic structures 5. Cartilage Hyaline Cartilage Found in: Articular cartilage (joint surfaces) Costal cartilage (ribs) Fibrocartilage Strongest cartilage Found in: Intervertebral discs Pubic symphysis Meniscus of knee Elastic Cartilage Provides flexibility Found in: External ear 6. Skin (Integumentary System) Epidermal Cells Keratinocytes Produce keratin Waterproofing protein Melanocytes Produce melanin Protect from UV radiation Langerhans Cells Immune defense Fight infection Merkel Cells Touch receptors 7. Layers of the Epidermis Deepest → Most Superficial Stratum Basale Stratum Spinosum Stratum Granulosum Stratum Lucidum (only thick skin) Stratum Corneum Thick Skin Found on: Palms Soles Contains: Stratum Lucidum Dead Layers Stratum Lucidum Stratum Corneum Filled with keratin. 8. Skin Glands Sudoriferous Glands Sweat glands Eccrine glands Apocrine glands Sebaceous Glands Produce sebum (oil) Ceruminous Glands Produce earwax Mammary Glands Modified sweat glands Produce milk 9. Skeletal System Upper Extremity Humerus Arm bone Radius Lateral forearm bone Thumb side Ulna Medial forearm bone Forms elbow joint Carpals Wrist bones 8 bones Metacarpals Hand bones Phalanges Finger bones Thumb: 2 phalanges Other fingers: 3 phalanges Pelvis Ilium Superior portion Pubis Anterior portion Ischium Posterior/inferior portion "Sit bones" Lower Extremity Femur Thigh bone Tibia Shin bone Medial Fibula Lateral lower leg bone Tarsals Ankle bones Metatarsals Foot bones Phalanges Toe bones Big toe: 2 phalanges Other toes: 3 phalanges High-Yield Exam Questions 1. What is Brownian movement? Random movement of particles caused by kinetic energy. 2. Does diffusion require energy? No. It is passive transport. 3. Difference between diffusion and facilitated diffusion? Facilitated diffusion requires a selectively permeable membrane protein. 4. What is phagocytosis? Cell eating (engulfing solids). 5. What is pinocytosis? Cell drinking (engulfing fluids). 6. Which epithelial tissue has one layer of column-shaped cells? Simple columnar epithelium. 7. What is the matrix of connective tissue? Fibers + ground substance. 8. Which cartilage is found in intervertebral discs? Fibrocartilage. 9. Which epidermal cells produce melanin? Melanocytes. 10. What are the five epidermal layers? Basale → Spinosum → Granulosum → Lucidum → Corneum. 11. Which bone is on the thumb side of the forearm? Radius. 12. Which bone forms the shin? Tibia. 13. What are the wrist bones called? Carpals. 14. What are the ankle bones called? Tarsals. 15. What are the hand and foot bones called? Metacarpals and Metatarsals. Quick Memorization Tips Pino = Sip → Pinocytosis = cell drinking Phago = Eat → Phagocytosis = cell eating Radius = Radio to Thumb → Radius is lateral Simple = One Layer Stratified = Many Layers Melanocytes = Melanin Keratinocytes = Keratin Sebaceous = Sebum (Oil) Sudoriferous = Sweat Carpals = Wrist Tarsals = Ankle This covers the major concepts your instructor specifically reviewed for the exam

Melanin

Exam 1 Concepts: Integumentary System: Know the importance of pressure injury prevention strategies i.e.. Q2 turns (pressure redistribution), moisture barrier cream (reduce moisture), pillows under bony prominences (limits friction/shearing), smooth and wrinkle-free linen (reduce bed irritation), adequate protein intake (improve wound healing) Normal skin findings vs abnormal findings Importance of each skin layer: epidermis (melanin, keratin), dermis (glands, vessels, nerves), hypodermis (fat, anchors skin) How to assess for early signs of pressure injury: redness, blanching, moist vs dry ​Dark skin tones: use palpation to detect tissue consistency Early signs of pressure injury: Q2 turns/repositioning= priority, never massage area, apply heat, or use alcohol Increase protein intake to help wound healing Musculoskeletal System: ROM: active vs passive. Always compare both sides of body for accurate assessment Body mechanics when transferring a patient: bend at knees, not waist, use leg muscles, avoid twisting, stand on patient’s stronger side to optimize support Cane=one point of contact for unilateral weakness; standard walker= four points of contact for bilateral weakness; crutches= three points of contact for non-weight bearing injury (crutches should be 6 inches from sides of feet to ensure stability and prevent tripping) Post-op joint replacement: cold therapy reduces swelling How to prevent contractures (splints, ROM) Osteoarthritis and Rheumatoid arthritis: encourage ROM after pain medication given, use assistive devices as needed to protect joints, apply warm compress before activity to reduce pain/stiffness, take breaks to conserve energy, perform low impact exercises to maintain mobility and strength, quit smoking Function of bone marrow Neurologic System: Correct sequence of a nerve impulse: action potential moves down axon terminal → neurotransmitter released → neurotransmitter binds to receptor → Sodium and potassium ions move to generate new action potential Cranial nerves: CN III = oculomotor, CN VII = facial, CN IX = glossopharyngeal, CNXII = hypoglossal (know what these 4 cranial nerves control) Cerebellum = coordination. Tested with finger-to-nose test Aphasia = difficulty communicating (receptive or expressive). Provide calm, slow speaking/direction, allow extra time, face patient directly, do not rush, do not ask multiple questions at once, do not talk over them Dysphagia = difficulty swallowing. High risk of aspiration. Stop oral intake and notify provider. If able, proceed with thickened liquids, sit patient up 90 degrees, observe for further signs of choking, monitor weight/hydration/nutrition Autonomic nervous system= involuntary (automatic) functions like digestion and heart rate Stroke prevention: adequate blood pressure control = priority Eye/Ear: Eye structures: cornea-bends light; lens-focuses light; retina-photoreceptors; iris-controls light entry PERRLA = pupils equal, round, reactive to light and accommodation Outer ear = pinna, canal; middle ear = ossicles, ET, tympanic membrane, amplifies sound, equalizes pressure, transmits sound; inner ear = cochlea, vestibular apparatus, converts sound to electrical nerve impulse Tympanic membrane: normal = pearly gray, shiny, translucent, visible cone of light Respiratory System: Abnormal lung sounds: Wheezes =high-pitched, often associated with asthma. Crackles = rattling sound, fluid in alveoli/bronchioles, common in pneumonia and heart failure. Ronchi = low pitched, snoring, caused by airway obstruction, common in COPD. Stridor = high pitched sound in the larynx or trachea, medical emergency, common in foreign body obstruction or anaphylaxis Diaphragm = breathing muscle Alveoli = gas exchange Pleura = serous membrane surrounding lungs and chest cavity; reduces friction, allows smooth expansion and contraction of lungs Incentive spirometry: smoking can affect results Chest Xray: patient should inhale fully and hold breath for best view Pulmonary function test (PFTs): avoid caffeine before test Bronchoscopy: post-op encourage coughing and deep breathing exercises Laryngoscopy: NPO for 8 hours prior ETCO2, capnography monitoring = measurement of CO2 being expired. Gas Exchange: Normal pH= 7.35-7.45; < 7.35 = acidosis, > 7.45 = alkalosis Normal CO2= 35-45; <35 = alkalosis, > 45 = acidosis Normal HCO3= 22-26; <22 = acidosis, >26= alkalosis CO2 = respiratory HCO3 = metabolic Dosage Calculation/Miscellaneous: Nursing process: always assess first before intervention There are 5 mL in 1 teaspoon There are 2.2 lbs per kg. ​Pounds to kilograms: divide by 2.2 ​Kilograms to pounds: multiply by 2.2 Know how to read a 24 hour clock (military time…ex. 2000 hours is 8pm) Fahrenheit to Celsius formula: F = (C x 9/5) + 32…….(9/5 = 1.8 in decimal form) ​Example: convert 38.3 C to F ​F = (38.3 x 9/5) + 32 OR (38.3 x 1.8) + 32 ​F = (68.94) + 32 ​F = 100.94 (round to nearest tenth—100

medication and use Calcium + Vitamin D – Bone strength / prevent osteoporosis Ipratropium–Albuterol (Duoneb) – Opens airways for breathing (COPD/asthma) Pantoprazole (Protonix) – Reduces stomach acid / GERD Baclofen – Muscle relaxer (spasms) Senna – Stimulant laxative (constipation) Ascorbic Acid (Vitamin C) – Supplement / wound healing support Potassium Chloride – Replaces low potassiumia im m N kJqz Furosemide (Lasix) – Diuretic; removes excess fluid (heart failure/edema) Thiamine (Vitamin B1) – Prevent/treat deficiency (often in malnutrition/alcohol use) Apixaban (Eliquis) – Blood thinner (prevents clots/stroke) Folic Acid – Vitamin supplement (red blood cell production) Levothyroxine – Thyroid hormone replacement (hypothyroidism) Magnesium Oxide – Magnesium supplement / helps constipation Milk of Magnesia – Laxative / antacid Bisacodyl (Dulcolax) – Stimulant laxative Melatonin – Sleep aid Ferrous Sulfate (Iron) – Treat/prevent anemia Multivitamin – General nutritional support Acetaminophen (Tylenol) – Pain / fever relief Trelegy Ellipta – Long-term inhaler for COPD/asthma control Docusate (Colace) – Stool softener Metoprolol Tartrate – Lowers heart rate/BP; heart protection Gabapentin – Nerve pain / sometimes seizures Lactulose – Laxative; also lowers ammonia (liver disease) Tamsulosin (Flomax) – Improves urination (enlarged prostate)

Melanin/Sickle Cell/UV

Biology Test - Melanin, Genetics, Protein Synthesis, and Evolution

Lecture 15 - Melatonin and Erythropoietin

Melanin unit

answers for Chapters 5, 6, and 7 based on your study guide: ⸻ ✅ Chapter 5 – Skeletal System 1. Functions of the Skeletal System • Support • Protection • Movement (with muscles) • Mineral storage (calcium, phosphorus) • Blood cell production (hematopoiesis) • Fat storage (yellow marrow) ⸻ 2. Axial vs Appendicular Skeleton Axial (80 bones) • Skull • Vertebral column • Ribs • Sternum • Hyoid Appendicular (126 bones) • Pectoral girdle (clavicle, scapula) • Upper limbs • Pelvic girdle • Lower limbs ⸻ 3. Bone Components • Compact (cortical) bone • Spongy (trabecular) bone • Periosteum • Endosteum • Bone marrow (red & yellow) • Articular cartilage ⸻ 4. Cortical vs Trabecular Bone • Cortical (compact): Dense, outer layer, strength • Trabecular (spongy): Porous, inside bone, reduces weight, houses marrow ⸻ 5. Bone Classification by Shape • Long (femur) • Short (carpals) • Flat (sternum) • Irregular (vertebrae) • Sesamoid (patella) ⸻ 6. Structure of a Long Bone • Diaphysis (shaft) • Epiphysis (ends) • Medullary cavity • Periosteum • Compact bone • Spongy bone ⸻ 7. Microscopic Bone Structure • Osteon (Haversian system) • Central canal • Lacunae (contain osteocytes) • Canaliculi (nutrient pathways) ⸻ 8. Osteoblast vs Osteoclast • Osteoblast: Builds bone • Osteoclast: Breaks down bone ⸻ 9. Three Types of Joints • Fibrous: Immovable (skull sutures) • Cartilaginous: Slight movement (intervertebral discs) • Synovial: Freely movable (knee) ⸻ 10. Osteoporosis & Arthritis • Osteoporosis: Bone thinning • Arthritis: Joint inflammation ⸻ ✅ Chapter 6 – Muscular System 1. Three Muscle Types • Skeletal: Voluntary, striated, attached to bones • Cardiac: Involuntary, heart only • Smooth: Involuntary, organs ⸻ 2. Connective Tissue Coverings • Endomysium → around muscle fiber • Perimysium → around fascicle • Epimysium → around whole muscle ⸻ 3. Fascicle Bundle of muscle fibers (covered by perimysium) ⸻ 4. Sarcomere Functional unit of muscle Boundaries: Z discs ⸻ 5. Bands • I band → thin only • A band → thick (and overlap) ⸻ 6. Filaments • Thick → Myosin • Thin → Actin, Troponin, Tropomyosin ⸻ 7. During Contraction • Sarcomere shortens • Z discs move closer • I band shortens • A band stays same ⸻ 8. Role of Calcium & ATP • Calcium: Exposes binding sites • ATP: Powers contraction & releases myosin ⸻ 9. Cross Bridge Myosin head binding to actin ⸻ 10. Neuromuscular Junction • Nerve releases acetylcholine (ACh) • ACh binds receptors • Muscle action potential starts ⸻ 11. Steps of Skeletal Muscle Contraction 1. Nerve impulse 2. ACh release 3. Muscle action potential 4. Ca²⁺ released from SR 5. Cross bridge formation 6. Power stroke 7. ATP binds & detaches 8. Relaxation when Ca²⁺ removed ⸻ 12. Three Ways Muscles Produce ATP • Direct phosphorylation (creatine phosphate) • Anaerobic glycolysis • Aerobic respiration ⸻ 13. Oxygen & Lactic Acid • Aerobic: Requires oxygen • Anaerobic glycolysis: Produces lactic acid ⸻ 14. Fastest Energy System Direct phosphorylation ⸻ 15. Isotonic vs Isometric • Isotonic: Muscle shortens (lifting weight) • Isometric: Tension, no movement (holding weight) ⸻ ✅ Chapter 7 – Nervous System 1. CNS Brain + spinal cord Function: control center ⸻ 2. PNS Cranial nerves + spinal nerves ⸻ 3. Afferent vs Efferent • Afferent: Sensory → to CNS • Efferent: Motor → from CNS ⸻ 4. Three Parts of Neuron • Dendrites (receive) • Cell body • Axon (send signal) ⸻ 5. Synapse Junction between neurons Synaptic cleft = gap between them ⸻ 6. Neurotransmitters Chemical messengers between neurons ⸻ 7. Three Neuron Types • Sensory • Motor • Interneurons ⸻ 8. CNS Neuroglia • Astrocytes • Oligodendrocytes • Microglia • Ependymal cells ⸻ 9. Action Potential Phases • Resting (-70mV) • Depolarization (Na⁺ in) • Repolarization (K⁺ out) • Hyperpolarization ⸻ 10. Myelinated Axons Faster Because Saltatory conduction (jumps between nodes) ⸻ 11. Reflex & Components Automatic response 5 parts: 1. Receptor 2. Sensory neuron 3. Integration center 4. Motor neuron 5. Effector ⸻ 12. Four Lobes of Cerebrum • Frontal → movement • Parietal → sensation • Temporal → hearing • Occipital → vision ⸻ 13. Thalamus, Hypothalamus, Epithalamus • Thalamus → sensory relay • Hypothalamus → homeostasis • Epithalamus → melatonin ⸻ 14. Brainstem Parts • Midbrain → reflexes • Pons → breathing control • Medulla → heart rate ⸻ 15. Cerebellum Balance & coordination ⸻ 16. Meninges • Dura mater • Arachnoid mater • Pia mater Protect CNS ⸻ 17. CSF Cerebrospinal fluid Found in ventricles & around brain/spinal cord ⸻ 18. Spinal Cord Structure: gray center, white outside Function: reflexes & signal pathway ⸻ 19. Sympathetic vs Parasympathetic • Sympathetic → fight or flight • Parasympathetic → rest and digest ⸻ 20. Effects on Organs Sympathetic: • ↑ heart rate • Dilates pupils • Stops digestion Parasympathetic: • ↓ heart rate • Constricts pupils • Stimulates digestion ⸻ 21