Chapter 6 – Bones and Skeletal Tissues (A&P 11e)

Vocabulary flashcards covering major structures, cell types, functions, and components of bones and skeletal cartilages from Chapter 6, Part A.

Skeletal cartilage

Highly resilient, molded connective tissue that is mostly water and lacks blood vessels and nerves.

Perichondrium

Dense connective tissue girdle surrounding cartilage; resists outward expansion and supplies nutrients via blood vessels.

Chondrocyte

Cartilage cell housed in a lacuna within a jelly-like extracellular matrix.

Hyaline cartilage

Most abundant cartilage; collagen-only matrix providing support, flexibility, and resilience (articular, costal, respiratory, nasal).

Elastic cartilage

Cartilage similar to hyaline but with elastic fibers; found in external ear and epiglottis.

Fibrocartilage

Cartilage with thick collagen fibers for great tensile strength; found in knee menisci and intervertebral discs.

Appositional growth

Cartilage growth in which new matrix is secreted on the surface by perichondrial cells.

Interstitial growth

Cartilage growth from within as chondrocytes divide and secrete new matrix.

Calcification of cartilage

Hardening of cartilage during normal growth or aging; not the same as bone.

Support (bone function)

Rigid framework for body and soft organs.

Protection (bone function)

Bone shields brain, spinal cord, and vital organs.

Movement (bone function)

Bones act as levers for muscle action.

Mineral storage

Reservoir for calcium, phosphorus, and growth factors.

Hematopoiesis

Blood cell formation occurring in red marrow cavities of certain bones.

Triglyceride storage

Energy reserve stored as fat in bone cavities.

Osteocalcin

Bone-secreted hormone that regulates insulin secretion, glucose levels, and metabolism.

Axial skeleton

80 bones forming the long axis: skull, vertebral column, rib cage.

Appendicular skeleton

126 bones of upper & lower limbs plus girdles attaching them to the axial skeleton.

Long bone

Bone longer than it is wide (e.g., humerus, femur).

Short bone

Cube-shaped bone (wrist, ankle); includes sesamoid bones like the patella.

Flat bone

Thin, flat, slightly curved bone (sternum, ribs, scapulae, skull bones).

Irregular bone

Complicated-shaped bone (vertebrae, hip bones).

Compact bone

Dense outer bone layer that appears smooth and solid.

Spongy bone

Honeycomb-like internal bone with trabeculae filled with red or yellow marrow.

Diploë

Thin plates of spongy bone between layers of compact bone in flat bones.

Diaphysis

Tubular shaft of a long bone surrounding the medullary cavity.

Epiphysis

End of a long bone; compact bone outside, spongy inside; covered by articular cartilage.

Epiphyseal line

Adult remnant of the childhood growth (epiphyseal) plate between diaphysis and epiphysis.

Medullary cavity

Central cavity of long bones containing yellow marrow in adults.

Periosteum

White, double-layered membrane covering external bone surfaces except joints; contains osteogenic cells.

Endosteum

Delicate connective tissue lining internal bone surfaces, trabeculae, and canals; also osteogenic.

Red marrow

Hematopoietic tissue in trabecular cavities; active in diploë and some irregular bones in adults.

Yellow marrow

Fat-rich marrow in medullary cavities that can revert to red marrow if severe anemia occurs.

Bone marking – Projection

Outward bulge of bone for muscle/ligament attachment or joint formation.

Bone marking – Depression

Bowl- or groove-like cut-out serving as passageway or joint surface.

Bone marking – Opening

Hole or canal in bone for blood vessels and nerves.

Osteogenic cell

Mitotically active bone stem cell in periosteum and endosteum.

Osteoblast

Bone-forming cell that secretes unmineralized matrix (osteoid).

Osteocyte

Mature bone cell residing in a lacuna; monitors and maintains bone matrix.

Bone-lining cell

Flat cell on bone surfaces that helps maintain matrix; called periosteal (external) or endosteal (internal) cell.

Osteoclast

Giant multinucleate cell responsible for bone resorption; sits in a resorption bay with ruffled border.

Osteon (Haversian system)

Structural unit of compact bone—an elongated cylinder of concentric lamellae.

Lamella

Ring of bone matrix within an osteon with collagen fibers oriented in alternating directions.

Central (Haversian) canal

Canal running through the osteon’s core containing blood vessels and nerves.

Perforating (Volkmann’s) canal

Channel perpendicular to the central canal, connecting blood vessels of periosteum and medullary cavity.

Lacuna

Small cavity in bone housing an osteocyte.

Canaliculi

Tiny hair-like canals connecting lacunae and central canal, enabling cell-to-cell communication.

Interstitial lamellae

Incomplete lamellae filling gaps between osteons or remnants of cut osteons.

Circumferential lamellae

Lamellae extending around entire diaphysis just deep to periosteum; resist twisting.

Trabecula

Rod or plate of spongy bone aligned along stress lines; contains lamellae and osteocytes but no osteons.

Osteoid

Organic part of bone matrix (ground substance + collagen) secreted by osteoblasts; gives tensile strength.

Hydroxyapatite

Inorganic mineral salt (calcium phosphate crystals) making bone hard and compression-resistant.