Chapter 7: Skeletal System - Cartilage and Bone

Vocabulary practice flashcards covering the components, structure, growth, histology, and gross anatomy of bone and cartilage from Chapter 7: Skeletal System.

Skeletal System Components

The four main tissues and structures that make up the skeletal system: bones ($206$ in adults), cartilage, ligaments, and tendons.

Skeletal Cartilage

A semi-rigid, smooth, and slippery connective tissue that reduces friction, is more flexible than bone, and contains no blood vessels or nerves.

Perichondrium

A layer of dense irregular connective tissue surrounding cartilage that helps maintain its shape and supplies nutrients and oxygen to cartilage by diffusion.

Hyaline Cartilage

A highly compressible shock-absorbing cartilage with cells scattered in a collagen-rich matrix and high water percentage; forms articular, nasal, and costal cartilages as well as epiphyseal plates.

Fibrocartilage

A type of cartilage located in weight-bearing regions including the pubic symphysis, intervertebral discs, and menisci.

Chondroblasts

Immature cartilage cells derived from mesenchymal stem cells that synthesize and produce cartilage matrix.

Chondrocytes

Mature cartilage cells that become encased within matrix lacunae and function to maintain the cartilage matrix.

Lacunae

Small spaces or cavities within the extracellular matrix occupied by chondrocytes in cartilage or osteocytes in bone.

Interstitial Growth

A pattern of cartilage growth that occurs within the internal region, allowing the tissue to increase in length as chondrocytes divide and push apart.

Appositional Growth

A pattern of cartilage growth occurring along the outer edge beneath the perichondrium, in which dividing stem cells produce chondroblasts that increase cartilage width.

Compact Bone

Also called cortical bone; a solid, white, and smooth bone tissue superficial to spongy bone that accounts for $80\%$ of total bone mass.

Spongy Bone

Also called trabecular bone; a porous bone tissue located deep to compact bone that accounts for $20\%$ of total bone mass.

Diaphysis

The elongated, cylindrical shaft of a long bone that provides leverage and major weight support.

Medullary Cavity

The hollow, cylindrical space within the diaphysis containing red bone marrow in children and yellow bone marrow in adults.

Epiphysis

The knobby region at each end of a long bone, classified as proximal (closest to trunk) or distal (farthest from trunk).

Articular Cartilage

A thin layer of hyaline cartilage covering the joint surface of an epiphysis to reduce friction and absorb shock in movable joints; lacks a perichondrium.

Metaphysis

The region of mature long bone between the diaphysis and epiphysis that houses the epiphyseal plate.

Epiphyseal Plate

A growth plate consisting of a thin layer of hyaline cartilage in the metaphysis that provides tissue for lengthwise bone growth.

Epiphyseal Line

The defined line of bone tissue in adults that replaces the hyaline cartilage of the epiphyseal plate after lengthwise growth stops.

Nutrient Foramen

A small opening in the bone through which blood vessels and sensory nerves enter and exit.

Red Bone Marrow

Hematopoietic (blood-cell-forming) myeloid tissue containing reticular tissue, immature blood cells, and fat; found in spongy bone and medullary cavities of children, and selected areas of the axial skeleton in adults.

Yellow Bone Marrow

A fatty tissue filled with adipocytes resulting from red bone marrow degeneration as children mature; can convert back to red marrow during severe anemia.

Periosteum

A tough sheath covering the outer surface of bone, consisting of an outer fibrous layer of dense irregular connective tissue and an inner cellular layer.

Perforating Fibers

Numerous collagen fibers that firmly anchor the periosteum to the underlying bone matrix.

Endosteum

An incomplete cellular layer covering internal bone surfaces within the medullary cavity, containing osteoprogenitor cells, osteoblasts, and osteoclasts.

Osteoprogenitor Cells

Mesenchymal stem cells located in the periosteum and endosteum that divide to yield another stem cell and a committed cell that differentiates into an osteoblast.

Osteoblasts

Bone-forming cells with abundant rough endoplasmic reticulum and Golgi apparatus that synthesize and secrete osteoid.

Osteoid

The initial semisolid organic form of bone matrix produced by osteoblasts that subsequently calcifies via salt crystal deposition.

Osteocytes

Mature bone cells derived from osteoblasts entrapped in lacunae that detect mechanical stress and maintain the surrounding matrix.

Osteoclasts

Large, multinucleated, phagocytic cells derived from fused macrophages with a ruffled border that dissolve and resorb bone matrix.

Resorption Lacuna

A pit or depression on the bone surface within or adjacent to which an active osteoclast resides during bone breakdown.

Osteon

The basic microscopic structural and functional unit of mature compact bone, consisting of concentric lamellae oriented parallel to the diaphysis.

Central Canal

A cylindrical channel at the center of an osteon parallel to the diaphysis, transmitting blood vessels and nerves.

Concentric Lamellae

Rings of bone matrix in an osteon surrounding the central canal, featuring collagen fibers aligned at approximately $90^\circ$ from adjacent rings to provide strength and resilience.

Circumferential Lamellae

Rings of compact bone that run the entire outer or inner circumference of the bone shaft directly deep to the periosteum or endosteum.

Interstitial Lamellae

Remnants of older, partially resorbed osteons found in the spaces between existing intact osteons in compact bone.

Perforating Canals

Canals containing blood vessels and nerves that run perpendicular to central canals, connecting multiple central canals across different osteons.

Canaliculi

Tiny interconnecting channels within compact bone that house osteocyte cytoplasmic projections, allowing intercellular contact and nutrient exchange.