Chapters 7 & 8 – Skeletal System and Joints

Vocabulary flashcards covering key terms and definitions from lecture chapters on the skeletal system, bone development, and joint structure and function.

Skeletal System

Organ system composed of bones and connective tissues that support, protect, enable movement, store minerals, and form blood cells.

Axial Skeleton

Division of the skeleton consisting of the skull, vertebral column, and thoracic cage.

Appendicular Skeleton

Division of the skeleton made up of the upper and lower limbs and their girdles.

Long Bone

Bone that is longer than it is wide and has expanded ends; e.g., femur.

Short Bone

Cube-like bone whose length equals its width; includes sesamoid bones.

Flat Bone

Plate-like bone with broad surfaces; e.g., sternum.

Irregular Bone

Bone of varied shape that does not fit other categories; e.g., vertebra.

Sesamoid Bone

Round bone embedded in a tendon, such as the patella.

Epiphysis

Expanded end of a long bone.

Diaphysis

Shaft of a long bone.

Metaphysis

Widening region between diaphysis and epiphysis.

Articular Cartilage

Hyaline cartilage covering epiphyses where bones articulate.

Periosteum

Dense irregular connective tissue membrane that encloses bone.

Compact Bone

Solid, weight-bearing cortical bone forming the outer layer.

Spongy Bone

Cancellous bone with trabeculae and spaces, reducing weight.

Trabeculae

Branching plates that form the framework of spongy bone.

Medullary Cavity

Hollow chamber in diaphysis that houses marrow.

Endosteum

Thin membrane lining the medullary cavity and trabeculae surfaces.

Red Bone Marrow

Tissue within certain bones that carries out hematopoiesis.

Yellow Bone Marrow

Fat-storing marrow that replaces some red marrow with age.

Osteocyte

Mature bone cell located in a lacuna; maintains bone matrix.

Osteoblast

Bone-forming cell that secretes bone matrix.

Osteoclast

Multinucleated cell that resorbs and dissolves bone matrix.

Lacuna

Small chamber housing an osteocyte.

Canaliculi

Tiny channels allowing osteocytes to exchange nutrients and waste.

Osteon

Cylindrical structural unit of compact bone surrounding a central canal.

Collagen Fibers

Protein strands in bone matrix providing strength and resilience.

Hydroxyapatite

Calcium phosphate salt that hardens bone matrix.

Hematopoiesis

Process of blood cell formation occurring in red marrow.

Intramembranous Ossification

Bone development from mesenchymal sheets; forms flat skull bones and clavicles.

Endochondral Ossification

Bone development by replacing hyaline cartilage models; forms long bones and most skeleton.

Mesenchyme

Primitive connective tissue whose cells can differentiate into osteoblasts.

Chondrocyte

Cartilage cell found in lacunae of cartilage matrix.

Primary Ossification Center

First region in diaphysis where bone replaces cartilage in endochondral bones.

Secondary Ossification Center

Region in each epiphysis where spongy bone forms later in development.

Epiphyseal Plate

Band of cartilage allowing lengthwise growth of long bones.

Epiphyseal Line

Remnant of epiphyseal plate indicating bone has stopped lengthening.

Zone of Resting Cartilage

Layer of epiphyseal plate anchoring it to the epiphysis.

Zone of Proliferating Cartilage

Region of rapidly dividing chondrocytes in epiphyseal plate.

Zone of Hypertrophic Cartilage

Layer where older chondrocytes enlarge, lengthening the bone.

Zone of Calcified Cartilage

Thin layer of dead, calcified cartilage replaced by bone.

Bone Resorption

Breakdown of bone matrix by osteoclasts.

Bone Deposition

Addition of bone matrix by osteoblasts.

Vitamin D

Nutrient (formed with sunlight) that promotes calcium absorption; deficiency causes rickets or osteomalacia.

Vitamin A

Vitamin stimulating osteoblast and osteoclast activity; deficiency slows bone development.

Vitamin C

Vitamin required for collagen synthesis; deficiency produces fragile bones.

Growth Hormone

Pituitary hormone stimulating cartilage cell division in epiphyseal plates.

Calcitonin

Thyroid hormone that lowers blood calcium by inhibiting osteoclasts and promoting deposition.

Parathyroid Hormone (PTH)

Hormone that raises blood calcium by stimulating osteoclasts.

Pituitary Dwarfism

Short stature due to childhood growth hormone deficiency.

Gigantism

Excessive height from childhood growth hormone overproduction.

Osteoporosis

Condition of severe bone mineral loss leading to weak, porous bones.

Fragility Fracture

Break occurring after a minor fall, indicating low bone density.

Simple (Closed) Fracture

Bone break protected by uninjured skin.

Compound (Open) Fracture

Fracture where bone is exposed through the skin.

Hematoma

Large blood clot that forms immediately after a fracture.

Soft (Cartilaginous) Callus

Fibrocartilage and spongy bone mass bridging broken bone ends.

Hard (Bony) Callus

Replaces soft callus with woven bone during fracture healing.

Remodeling

Final fracture-repair phase restoring bone shape via osteoclasts and osteoblasts.

Synarthrotic Joint

Immovable joint.

Amphiarthrotic Joint

Slightly movable joint.

Diarthrotic Joint

Freely movable joint; all synovial joints.

Fibrous Joint

Joint united by dense connective tissue; includes syndesmosis, suture, gomphosis.

Syndesmosis

Amphiarthrotic fibrous joint bound by interosseous membrane or ligament (tibia–fibula).

Suture

Synarthrotic fibrous joint between skull bones.

Gomphosis

Peg-in-socket fibrous joint; tooth in alveolar socket.

Cartilaginous Joint

Joint united by cartilage; includes synchondrosis and symphysis.

Synchondrosis

Hyaline cartilage joint; synarthrotic; e.g., first rib–sternum.

Symphysis

Fibrocartilage joint; amphiarthrotic; e.g., pubic symphysis, intervertebral disc.

Synovial Joint

Diarthrotic joint with a fluid-filled cavity, articular cartilage, and capsule.

Joint Capsule

Two-layer covering of synovial joint; outer fibrous layer plus inner synovial membrane.

Synovial Fluid

Viscous fluid secreted by synovial membrane that lubricates joints.

Meniscus

Fibrocartilage disc dividing a synovial joint cavity and improving fit.

Bursa

Synovial fluid-filled sac reducing friction between structures.

Ball-and-Socket Joint

Multiaxial synovial joint with spherical head in cup socket; hip, shoulder.

Condylar Joint

Ellipsoidal biaxial joint between oval condyle and elliptical cavity; knuckles.

Plane (Gliding) Joint

Nonaxial joint with flat surfaces; wrist and ankle bones.

Hinge Joint

Uniaxial joint allowing flexion and extension; elbow, interphalangeal joints.

Pivot Joint

Uniaxial joint permitting rotation around a central axis; atlas–axis.

Saddle Joint

Biaxial joint with concave-convex surfaces; thumb carpal-metacarpal.

Flexion

Bending that decreases the angle between body parts.

Extension

Straightening that increases the angle between parts.

Hyperextension

Extension beyond anatomical position.

Abduction

Movement away from the midline.

Adduction

Movement toward the midline.

Dorsiflexion

Upward movement of the foot at the ankle.

Plantar Flexion

Downward movement of the foot at the ankle.

Circumduction

Cone-shaped circular movement of a limb.

Rotation

Turning a bone around its longitudinal axis.

Supination

Forearm rotation so palm faces anteriorly/upward.

Pronation

Forearm rotation so palm faces posteriorly/downward.

Inversion

Turning sole of foot medially.

Eversion

Turning sole of foot laterally.

Protraction

Anterior movement of a body part (e.g., jaw forward).

Retraction

Posterior movement of a body part (e.g., jaw backward).

Elevation

Lifting a body part superiorly.

Depression

Moving a body part inferiorly.

Arthritis

Inflammation of a joint causing pain and swelling.

Osteoarthritis

Degenerative joint disease associated with aging.

Rheumatoid Arthritis

Autoimmune disorder in which immune system attacks joint tissues.