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Biol 223 Skin
Integumentary system
| Term | Definition |
|---|---|
| Integumentary System | Largest organ in surface area; ~3000 square inches; 16% of body by weight. Stores nutrients; regulates temperature; excretes waste; synthesizes vitamin D3; senses (temp, pain, tactile, etc.), protects. |
| Cutaneous Layer | Epidermis and dermis |
| Subcutaneous Layer | Deepest layer of dermis |
| Accessory Structures | Hair follicles (epidermal in origin); nails, exocrine glands. |
| Epidermis | Stratified squamous epithelium (keratinized = very strong); attached to dermis by basal lamina; contains no blood vessels |
| Keratinocytes | Main cell type of epidermis; keratinized cells |
| Melanocytes | Produce melanin/pigment; everyone has the same number |
| Langerhans Cells | Immune cells of epidermis |
| Merkel Cells | Sensory system/touch of epidermis |
| Dermis | Connective tissue proper; provides structural strength and elasticity to skin (collagen, reticular, elastic fibers); contains blood vessels and nerves of the skin. |
| Papillary Layer | Thin layer of loose areolar connective tissue (dermis). |
| Reticular layer | Thick layer of dense irregular connective tissue (dermis). |
| Subcutaneous Layer (Hypodermis, subQ) | Connects skin to underlying tissues; loose fibrous connective tissue for strength and elasticity; contains fat (adipose connective tissue) for padding and insulation; contains many blood vessels and nerves; aka: superficial fascia |
| Nutrient Storage | Meets body's requirement for constant supply of lipids; synthesizes membranes and lipid hormones; ATP production via breakdown of fatty acids. |
| Temperature Regulation | Blood vessels in dermis dilate for heat loss and contract for heat conservation; sweat glands cool body (secrete water which evaporates); subcutaneous layer insulates (fat). |
| Excretion | Removes waste from body through sweat glands; also secretes water, electrolytes, nitrogenous waste from protein breakdown (nitrogenous). |
| Vitamin D3 Synthesis | Cholecaciferol = D3 percursor; calcitrol = hormone to take up calcium/phosphate. UV light -> synthesize cholecalciferol -> calcitrol -> absorbs Ca2+ from gut/regulates levels |
| Sensory Detection | Pain: nociceptors = free nerve endings/ sensory dendrites. Temperature: thermoreceptors = free nerve endings Touch/pressure/vibration: lamellated (pacinian) corpuscles, tactile (Meisner's) corpuscles, tactile disks, hair root plexus. |
| Protection | Layers of keratinized cells - abrasion protection, water resistant (insensible perspiration), resistant to microbial invasion. Melanocytes - protect against UV radiation |
| Epidermal Keratinocytes | Stratified squamous epithelium; 4-5 layers depending on location. Corneum, lucidum (only thick skin), granulosum, spinosum, germinativum. |
| Keratinizatin of Epidermis | Stem cells in stratum germinativum (basale layer) -> new cells push up old cells -> oldest cells shed off; Process takes 30-45 days; accumulate large amounts of keratin in stratum granulosum before dying. |
| Epidermal Ridges | Ridges of stratum germinativum are interlocked with dermal papillae; improve gripping ability; make up fingerprints |
| Skin Color | Determined by color of melanin, how much melanin, how long melanocyte projections are; blood supply in dermis (hemoglobin in RBCs); carotene (dietary). |
| Hyperkaratosis | Thickening of the stratum corneum, often associated with the presence of an abnormal quantity of keratin. Calluses, corns; psoriasis |
| Xerosis | Abnormally dry skin |
| Herpes | Due to the herpes simplex virus - causes small, painful blisters commonly called cold sores or fever blisters |
| Warts | Painless growths on skin caused by human papillomavirus (HPV) infecting top layer of skin. |
| Basal Cell Carcinoma | Slow growing, rarely metastasizes or kills |
| Squamous Cell Carcinoma | Epidermis; can be deadly or aggressive (metastasize) if not treated. |
| Melanoma | Most dangerous; due to damaged DNA; malignant; often deadly if not caught early. |
| Neoplasm (Tumor) | Abnormal tissue growth, loss of normal control of cell division |
| Benign | Cells usually remain within a confined connective tissue capsule - not life threatening. |
| Malignant | Invasive, cancerous; cells spread into surrounding tissues or disperse to distant sites and establish secondary tumors (metastasis). |
| Carcinogens | Some mutagenic (damage DNA), radiation; 40% of cancers due to a single environmental factor (ex: cigarette smoke); primary carcinogen for skin cancer = UV light. |
| Elasticity of the Skin | Needs water (like dried up mud puddle); tolerates some stretching; excess causes stretch marks; reduced by aging, hormones, excess UV light. |
| Dermal Circulation | Provides nutrients and oxygen for all of skin (epidermis, dermis, accessory structures); cutaneous plexus, papillary plexus. |
| Accessory Structures | Hair follicles and hair; nails; exocrine glands |
| Hair Growth | Sensitive to changes in body chemistry, blood circulation, radiation, hormones, etc. |
| Vellus Hairs | Small, short, thin - peach fuzz |
| Terminal Hairs | Longer, darker - "normal" hairs/heavy |
| Club Hairs | No longer growing; balding |
| Hair Bulb | Matrix (germinative layer) produces karatinocytes, has cyclic growth pattern; melanocytes produce color |
| Hair Papillae | Dermal CT at base of follicle contains capillaries and nerves |
| Hair Shaft | Dead keratinized cells; medulla, cortex, cuticle |
| Hair Medulla | Dead cells with soft keratin and melanin |
| Hair Cortex | Dead cells with hard keratin and melanin |
| Cuticle | Superficial protective layer of overlapping, dead keratinized cells |
| Cutaneous Plexus | Vessels located at border between subcutaneous layer and dermis |
| Papillary Plexus | Vessels at dermis-epidermis border |
| Internal Root Sheath | Produced by cells at periphery of hair matrix |
| External Root Sheath | Extension of epidermis from surface of skin down to hair matrix |
| Glassy Membrane | Basal lamina connecting hair sheath (epidermis) to surrounding dermis |
| Arrector Pili Muscles | Extend from papillary layer of dermis to connective tissue sheath surrounding follicle - smooth muscle |
| Root Hair Plexus | Sensory nerves surrounding base of each hair follicle |
| Ceruminous Glands | Wax producing glads in ear canals; also sebaceous glands (modified merocrine glands). Produce secretions that combine with secretion of sebaceous glands to form waxy substance - cerumen (aka: earwax). |
| Mammary Glands | Milk producing glands; anatomically similar to apocrine sweat glands; maturation depends on hormones (estrogen) secreted at puberty and childbirth. |
| Sudoriferous Glands | Sweat glands; merocrine (eccrine); apocrine (armpits & pubic region) |
| Sebaceous Glands | Oil glands; discharge sebum onto hair shaft or epidermal surfaces; holocrine secretion |
| Sebum | Mixture of lipids, proteins, electrolytes; antibacterial; conditions hair and skin. |
| Merocrine (Eccrine) Sweat Glands | Sensible perspiration (evaporative cooling); open onto skin surface; most numerous on palms and soles. |
| Appocrine Sweat Glands | Secrete fluid containing lipids (bacterial = strong odor); open into hair follicles; armpits, pubic region; mostly active after puberty |
| Nail Root | Site of nail production; germinal matrix of stem cells; continuous growth; growth sensitive to changes in body metabolism, chemicals, diseases, disorders. |
| Nail Body | Dead, keratinized cells |
| Nail Bed | Sterile matrix; thin layer of epithelium underlying nail body; many nerve endings and blood vessels |
| Closed Wound | Contusion (bruise) |
| Open Wound | Abrasions, incisions, lacerations, punctures, avulsions (tears), burns (death) |
| Regeneration Process | Scab (blood clot) -> granulation tissue (rebuilds) -> scar tissue; positive feedback loop |
| 1st Degree Burn | Some epidermal damage |
| 2nd Degree Burn | Epidermal and some dermal damage (hair follicles fall out) |
| 3rd Degree Burn | Full thickness burn; loss of epidermis and dermis, extending into subcutaneous layer, loss of accessory structures |
| Burn Treatments | Skin grafts (split/full thickness); synthetic skin |
| Ulcer | Area of epithelial sloughing with damage to underlying connective tissue and blood vessels; loss of circulation leads to death of epidermal cells allowing bacteria to invade |
| Decubitus Ulcer | Bedsore; pressure on skin over underluing bone reduce blood flow in dermal vessels |
| Diabetic Ulcer | peripheral neruropathy and athlosclerotic peripher arterial disease |
Created by:
usillygoose93
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