Chapter 6 Skeletal System – Vocabulary Flashcards (VOCABULARY)

Vocabulary-style flashcards covering key terms and definitions from the Skeletal System lecture notes.

Skeletal system

The body system composed of bones, cartilage, ligaments, and bone marrow that provides support, protection, movement, and mineral storage.

Cartilage

Connective tissue; precursor to most bones in development and covers joint surfaces.

Ligaments

Fibrous tissues that connect bones at joints to provide stability.

Bone marrow

Soft tissue inside bones; red marrow forms blood cells and platelets, yellow marrow stores fat.

Osteogenic cells

Stem cells on bone surfaces that differentiate into osteoblasts.

Osteoblasts

Bone-forming cells that synthesize bone matrix and promote mineralization.

Osteocytes

Mature bone cells derived from osteoblasts; reside in lacunae and communicate via canaliculi.

Lacunae

Small cavities within bone matrix that house osteocytes.

Canaliculi

Microscopic channels that connect lacunae, enabling nutrient and signal exchange between osteocytes.

Osteoclasts

Bone-dissolving cells; large with multiple nuclei; resorb bone at the ruffled border.

Osteon

The structural unit of compact bone, consisting of concentric lamellae around a central canal.

Compact bone

Dense bone tissue; forms outer layer and encloses spongey bone in an osteon-rich matrix.

Spongy bone

Porous interior bone tissue with trabeculae; houses bone marrow and vessels.

Bone matrix

The extracellular material of bone composed of organic collagen and inorganic calcium phosphate.

Osteoid (organic matrix)

Part of the bone matrix rich in collagen that becomes mineralized.

Calcium phosphate

Inorganic mineral salt in bone matrix providing rigidity.

Rickets and osteomalacia

Bone softening diseases due to mineral deficiencies in the diet or metabolism.

Medullary cavity

Central cavity within a bone shaft that contains bone marrow.

Articular cartilage

Hyaline cartilage covering the ends of long bones to ease joint movements.

Epiphysis

Expanded end of a long bone that participates in joints and is filled with spongy bone.

Diaphysis

Shaft or long, cylindrical part of a long bone.

Endosteum

Thin connective tissue lining the internal surfaces of all bone tissue.

Periosteum

Fibrous, vascular sheath covering the outer bone surface; collagen fibers connect with tendons.

Fontanels

Soft spots in the infant skull where font material has not yet ossified; allow skull compression during birth.

Red bone marrow

Marrow that produces blood cells; abundant in children.

Yellow bone marrow

Fat-containing marrow that predominates in adults within long bones.

Ossification

The process of bone formation.

Intramembranous ossification

Bone develops directly from mesenchyme; forms flat bones like the skull; fontanels indicate unossified regions in infants.

Endochondral ossification

Bone replaces hyaline cartilage model; forms most bones except flat bones of the skull.

Perichondrium

Dense connective tissue that envelops cartilage and contributes to bone formation in endochondral ossification.

Periosteum vs Endosteum

Periosteum covers outer bone; endosteum lines internal bone surfaces.

Epiphyseal plate (growth plate)

Cartilaginous zone in long bones where growth occurs; becomes an epiphyseal line in adults.

Osteoclast activity

Resorption of bone minerals into the blood, often increased during calcium needs.

Calcitriol

Active vitamin D; increases calcium absorption and mobilizes calcium from bone.

Parathyroid hormone (PTH)

Raises blood calcium by stimulating bone resorption, kidney reabsorption, and calcitriol synthesis.

Calcitonin

Lowers blood calcium by promoting bone deposition and reducing calcium reabsorption.

Growth hormone

Stimulates bone growth and ossification.

Estrogen

Promotes bone deposition and maintenance; important for bone density, especially post-menopause.

Testosterone

Promotes ossification and bone growth in males.

Vitamins D, A, C

Vitamins that support bone deposition, repair, and overall bone health.

Ossification centers

Sites where bone formation begins; primary forms in endochondral ossification and intramembranous ossification sites.

Growth plate closure

End of bone elongation when the epiphyseal plate is depleted of cartilage and replaced by bone.

Joints

Connections between bones; classified structurally as fibrous, cartilaginous, or synovial.

Fibrous joints

Joints bound by collagen fibers; little mobility (e.g., skull sutures).

Cartilaginous joints

Joints connected by cartilage; allow limited movement (amphiarthrosis).

Synovial joints

Freely movable joints with a joint cavity and synovial fluid (diarthrosis).

Synovial joint anatomy

Contains joint cavity, synovial fluid, articular cartilage, joint capsule, synovial membrane, and sometimes discs or menisci.

Menisci

Crescent-shaped cartilage in the knee that improves fit and absorbs shock.

Bursae

Fluid-filled sacs that cushion tendons and reduce friction.

Six types of synovial joints

Ball-and-socket, hinge, pivot, plane (gliding), saddle, and condylar joints.

Ball-and-socket joint

Sphere-like head fits into cuplike socket; allows multiaxial movement (e.g., shoulder, hip).

Hinge joint

Convex surface into a concave surface; movement mainly in one plane (e.g., elbow, knee).

Pivot joint

Bone spins around a longitudinal axis (e.g., radioulnar joints; atlas–axis).

Condylar (ellipsoid) joint

Oval convex surface fits into a depressions allowing two-plane movement (e.g., knuckles).

Saddle joint

Saddle-shaped surfaces permit two-plane movement; enables thumb opposition.

Plane (gliding) joint

Flat or slightly curved surfaces that glide; movement in two planes (e.g., intercarpal).

Cartilage wear diseases

Osteoarthritis: wear of articular cartilage; Rheumatoid arthritis: autoimmune synovial inflammation.

Gouty arthritis

Joint inflammation due to uric acid crystal deposition.

Rheumatism

Broad term for musculoskeletal pain; rheumatologist treats these conditions.

Vertebral column components

33 vertebrae and 23 intervertebral discs; cervical, thoracic, lumbar, sacral, coccygeal.

Spinal curvatures

Cervical, thoracic, lumbar, and pelvic curvatures; contribute to bipedal posture.

Atlas (C1) and Axis (C2)

First two cervical vertebrae; atlas supports the head, axis provides rotation via the dens.

Intervertebral discs

Nucleus pulposus surrounded by annulus fibrosus; can herniate.

Paranasal sinuses

Air-filled cavities named for the bones they reside in: frontal, sphenoid, ethmoid, maxillary.

Auditory ossicles

Three tiny bones (malleus, incus, stapes) in each middle ear.

Hyoid bone

A unique bone that does not articulate with another bone; anchor for tongue muscles.

Cranial vs facial bones

Cranial bones form the cranium; facial bones shape the face and support cavities.

Infant skull anatomy

Fontanels are soft spots where intramembranous ossification is incomplete, allowing birth compression.

Sutures

Fibrous joints between skull bones; appear as seams.

Cranial cavities

Includes the cranial cavity, orbits, nasal cavity, and oral cavity.

Vertebral foramen and canal

Opening for the spinal cord (vertebral foramen) and the spinal canal (formed by all vertebral foramina).