Skeletal System - Cartilage and Bone Histology & Growth

Vocabulary flashcards defining structural components, tissue types, cells, and developmental processes of the skeletal system.

Axial Skeleton

The skeletal division comprising the skull, ribs, and vertebral column, located at the head and center of the body.

Appendicular Skeleton

The skeletal division comprising the limbs and pelvis, responsible for body movement.

Lacunae

Compartments in supporting connective tissue where cells reside and remain even after the cells die.

Appositional Growth

Tissue growth that occurs by adding new layers of matrix to the outside surface.

Interstitial Growth

Tissue growth that occurs by cell division and matrix deposition expanding the tissue from within.

Perichondrium

Dense irregular connective tissue surrounding most cartilage that provides support, protection, and stem cells for cartilage growth.

Chondroblasts

Cartilage-forming cells derived from stem cells in the inner perichondrium that lay down new matrix and mature into chondrocytes when trapped in lacunae.

Chondrocytes

Mature cartilage cells residing in lacunae that divide and secrete matrix during interstitial cartilage growth.

Hyaline Cartilage

The most common but weakest cartilage type with the least fibers, found in the embryonic skeleton, articular surfaces, respiratory passages, nasal septum, and between ribs and sternum.

Elastic Cartilage

The most elastic cartilage type containing the highest concentration of elastic fibers, found in the auricle, tip and lateral walls of the nose, and epiglottis.

Fibrous Cartilage

The most stress-resistant cartilage type containing the highest concentration of collagen fibers, found in intervertebral discs, pubic symphysis, and articular cartilage in the knee.

Osteoprogenitor Cells

Mesenchymal stem cells that mature to become osteoblasts.

Osteoblasts

Bone-building cells that secrete new bone tissue matrix and mature into osteocytes upon becoming trapped in their own matrix.

Osteocytes

Mature bone cells residing in lacunae that repair existing bone tissue and connect to neighboring cells via canaliculi.

Osteoclasts

Large bone-resorbing cells derived from the merger of multiple macrophages that break down bone matrix.

Canaliculi

Tiny canals in bone matrix through which osteocytes connect to one another to transfer nutrients and wastes.

Osteoid

The organic material of bone matrix composed of flexible collagen fibers, glycoproteins, and proteoglycans.

Hydroxyapatite

The inorganic brittle calcium salt component of bone matrix with the chemical formula $\text{Ca}_{10}(\text{PO}_4)_6(\text{OH})_2$.

Osteons

The primary structural units of compact bone consisting of concentric lamellae surrounding a central (Haversian) canal.

Concentric Lamellae

Concentric layers of bone matrix arranged around the central canal of an osteon.

Circumferential Lamellae

Outer layers of compact bone laid down around the outer perimeter beneath the periosteum during appositional growth.

Interstitial Lamellae

Remaining fragments of old bone matrix situated between newly formed osteons.

Trabeculae

A latticework of thin spines or beams of bone in spongy bone oriented along lines of stress to resist compression.

Myeloid Tissue

Tissue found in red bone marrow where all types of blood cells develop.

Periosteum

Connective tissue surrounding compact bone consisting of an outer fibrous layer and an inner cellular layer of stem cells for appositional growth.

Endosteum

A single cell layer lining spongy bone trabeculae, medullary cavities, and central/perforating canals that functions in bone remodeling and marrow cavity expansion.

Red Bone Marrow

Tissue composed of areolar and myeloid tissue that produces blood cells, found in infant medullary cavities and adult spongy bone.

Yellow Bone Marrow

Tissue composed of areolar and adipose connective tissue located in long bone medullary cavities for energy storage.

Intramembranous Ossification

The formation of bone directly within sheets of embryonic connective tissue proper, forming flat bones like the embryonic skull.

Endochondral Ossification

The formation of bone replacing a pre-existing hyaline cartilage model.

Fontanelles

Unossified fibrous membrane areas ("soft spots") remaining in infant skull bones at birth.

Diaphysis

The central elongated shaft of a long bone.

Epiphysis

The expanded end region of a long bone.

Metaphysis

The region of active growth and new bone formation situated between the diaphysis and epiphysis.

Primary Ossification Center

The initial site of spongy bone formation within the cartilage shaft (diaphysis) during endochondral ossification.

Secondary Ossification Center

The site of spongy bone formation within the cartilage ends (epiphyses) during endochondral ossification.

Epiphyseal Plate

A band of hyaline cartilage remaining between the primary and secondary ossification centers that allows long bones to elongate until puberty.

Bone Remodeling

The ongoing process of osteoclast breakdown and osteoblast rebuilding that continually redistributes bone matrix along lines of mechanical stress.