Integumentary, Skeletal, Joint & Muscular Systems – Core Vocabulary

Vocabulary flashcards covering key terms from the integumentary, skeletal, joint, and muscular system lecture notes.

Organ

A structure composed of two or more tissue types that work together to perform specialized functions.

Organ System

Two or more organs working together toward the same overall function.

Integumentary System

The skin plus its accessory structures (hair, nails, glands, receptors, muscles).

Skin

Largest organ by weight; outer protective covering of the body.

Epidermis

Superficial, avascular layer of stratified squamous epithelium.

Dermis

Thick inner layer of connective tissue containing collagen, elastic fibers, nerves, and vessels.

Subcutaneous Layer (Hypodermis)

Areolar + adipose tissue beneath skin; insulates, stores fat, anchors skin.

Basal Cells

Mitotically active cells in stratum basale that give rise to keratinocytes.

Keratinization

Process by which epidermal cells produce keratin, die, and form a tough, waterproof layer.

Stratum Basale

Deepest epidermal layer; single row of dividing cells and melanocytes.

Stratum Spinosum

Epidermal layer above basale with many keratin-producing cells and desmosomes.

Stratum Granulosum

Thin epidermal layer where cells accumulate keratohyalin granules and begin to die.

Stratum Lucidum

Clear layer between granulosum and corneum found only in thick skin of palms and soles.

Stratum Corneum

Outermost layer of dead, flattened, keratinized cells that are continuously shed.

Callus

Localized thickening of epidermis on palms/soles due to friction.

Corn

Cone-shaped, hardened mass of thickened skin on toes from pressure.

Psoriasis

Chronic skin disorder where epidermal cells divide 7× faster, producing red patches with silvery scales.

Intradermal Injection

Drug administration into the dermis.

Subcutaneous Injection

Drug administration into the hypodermis.

Intramuscular (Hypodermic) Injection

Drug administration deep into muscle tissue.

Transdermal Patch

Device that delivers medication across the skin into dermal blood vessels over time.

Pressure Ulcer (Bedsore)

Localized skin & tissue necrosis caused by prolonged pressure that blocks blood flow.

Keratinocyte

Most abundant epidermal cell; produces keratin for protection and waterproofing.

Dendritic (Langerhans) Cell

Antigen-presenting cell in stratum spinosum that initiates immune responses.

Tactile (Merkel) Cell

Sensory cell in stratum basale that detects light touch via tactile discs.

Melanocyte

Pigment-producing cell in stratum basale that synthesizes melanin.

Melanin

Brown-black or red-yellow pigment that protects DNA from UV radiation.

Eumelanin

Brown-black form of melanin giving dark skin and hair color.

Pheomelanin

Red-yellow melanin found in lighter hair and lips.

Albinism

Genetic absence of melanin resulting in pale skin, hair, and eyes.

Cyanosis

Bluish skin coloration due to low oxygenated blood.

Jaundice

Yellow skin tint from bilirubin accumulation, often due to liver issues.

Carotene

Orange pigment from diet that can accumulate in skin and act as antioxidant.

Dermal Papilla

Upward projection of dermis that increases surface area and forms fingerprints.

Papillary Layer

Superficial dermal layer of areolar connective tissue supporting the epidermis.

Reticular Layer

Deep dermal layer of dense irregular connective tissue providing strength and elasticity.

Fingerprint

Pattern created by epidermal ridges over dermal papillae; unique to each individual.

Arrector Pili Muscle

Smooth muscle that elevates hair and causes goosebumps when contracted.

Sebaceous Gland

Holocrine gland releasing oily sebum into hair follicles for lubrication and waterproofing.

Sebum

Oily mixture of lipids and cell debris that moisturizes skin and hair.

Sudoriferous (Sweat) Gland

Exocrine gland producing perspiration for thermoregulation and waste removal.

Merocrine (Eccrine) Sweat Gland

Most numerous sweat gland secreting watery sweat directly to skin surface for cooling.

Apocrine Sweat Gland

Sweat gland of axilla/groin active at puberty; secretes protein-rich fluid that bacteria convert to body odor.

Ceruminous Gland

Modified apocrine gland of ear canal producing cerumen (earwax).

Mammary Gland

Modified apocrine gland in breast that produces milk.

Nail Plate

Visible hard, keratinized part of the nail.

Nail Bed

Skin surface under nail plate formed by specialized epidermis.

Nail Matrix

Proximal thickened region that produces the nail plate.

Lunula

Pale half-moon at nail base where vessels are obscured by thick matrix.

Hair Follicle

Tubelike depression in dermis where hair develops from stem cells.

Hair Bulge

Stem-cell-rich region of follicle that can regenerate hair or epidermis.

Hair Papilla

Vascular projection into hair bulb supplying nutrients to growing hair.

Hair Shaft

Dead, keratinized cells that extend above skin surface as visible hair.

Growth Phase (Anagen)

Active hair-growing period lasting 2-6 years for most scalp hairs.

Resting Phase (Telogen)

Hair cycle stage when growth stops for ~2-3 months before shedding.

Goosebumps

Skin elevation caused by arrector pili contraction raising hairs.

Protection (Skin Function)

Barrier role preventing mechanical, chemical, microbial, and UV damage.

Thermoregulation

Skin-mediated control of body temperature via blood flow and sweating.

Vitamin D Synthesis

Skin converts dehydrocholesterol to cholecalciferol which becomes active calcitriol for calcium absorption.

Skeleton

Framework of bones, cartilage, ligaments, and tendons supporting and protecting the body.

Axial Skeleton

Skull, vertebral column, and thoracic cage; central supportive axis.

Appendicular Skeleton

Bones of limbs and girdles attaching them to axial skeleton.

Long Bone

Bone with elongated shaft and expanded ends (e.g., femur).

Short Bone

Cube-like bone with roughly equal length and width (e.g., carpal).

Flat Bone

Broad, thin bone such as ribs or cranial plates.

Sesamoid Bone

Small, round bone embedded in tendon, e.g., patella.

Irregular Bone

Complex-shaped bone like vertebra or facial bone.

Epiphysis

Expanded end of a long bone containing spongy bone and red marrow.

Diaphysis

Shaft of a long bone composed mainly of compact bone.

Metaphysis

Region between diaphysis and epiphysis containing growth plate.

Periosteum

Fibrous, vascular membrane covering bone except at articular surfaces.

Compact (Cortical) Bone

Dense outer bone layer organized into osteons for strength.

Spongy (Cancellous) Bone

Porous bone inside epiphyses made of trabeculae housing marrow.

Medullary Cavity

Hollow chamber within diaphysis containing marrow and lined by endosteum.

Osteocyte

Mature bone cell residing in a lacuna and maintaining bone matrix.

Osteon (Haversian System)

Structural unit of compact bone consisting of concentric lamellae around a central canal.

Trabecula

Thin bony plates forming spongy bone lattice.

Hematopoiesis

Blood cell formation occurring chiefly in red bone marrow.

Red Marrow

Marrow type producing red cells, white cells, and platelets.

Yellow Marrow

Marrow largely composed of fat; can convert to red marrow if needed.

Hydroxyapatite

Inorganic calcium phosphate crystals giving bone its hardness.

Parathyroid Hormone (PTH)

Hormone that raises blood calcium by stimulating osteoclast activity.

Calcitonin

Thyroid hormone that lowers blood calcium by stimulating osteoblasts.

Intramembranous Ossification

Bone formation within sheets of mesenchyme producing flat bones.

Endochondral Ossification

Bone development by replacing a hyaline cartilage model; forms most bones.

Epiphyseal Plate

Growth plate of hyaline cartilage enabling lengthwise bone growth.

Zone of Resting Cartilage

Epiphyseal plate layer anchoring cartilage to epiphysis; no growth activity.

Zone of Proliferating Cartilage

Growth plate layer with rapidly dividing chondrocytes lengthening bone.

Zone of Hypertrophic Cartilage

Layer where chondrocytes enlarge and lacunae expand.

Zone of Calcified Cartilage

Thin layer of dead cells and calcified matrix invaded by osteoblasts.

Bone Remodeling

Continuous resorption and deposition of bone by osteoclasts and osteoblasts.

Osteoblast

Bone-building cell that secretes bone matrix.

Osteoclast

Large multinucleated cell that breaks down bone tissue.

Osteogenic (Stem) Cell

Bone stem cell that can differentiate into osteoblasts.

Fontanel

Soft membranous gap between infant cranial bones allowing growth and birth.

Foramen Magnum

Large opening in occipital bone for passage of spinal cord.

Sella Turcica

Depression in sphenoid bone housing the pituitary gland.

Crista Galli

Vertical projection of ethmoid bone for dura mater attachment.

Zygomatic Arch

Cheekbone arch formed by zygomatic and temporal bones.

Alveolar Process

Bony ridge containing tooth sockets in maxilla or mandible.