Human Skeletal Biology — Study Materials Flashcards

Front

Wolff's law

Back

Bone adapts its structure to the mechanical loads placed upon it, becoming stronger where stress is higher. This functional adaptation explains remodeling responses like increased cortical thickness at muscle attachment sites.

Front

Osteon

Back

The osteon (Haversian system) is the cylindrical structural unit of secondary compact bone composed of concentric lamellae around a central canal. It contains blood vessels and nerves that supply cortical bone and is delineated by a cement line.

Front

Osteoblast

Back

Osteoblasts are bone-forming cells that synthesize organic matrix (osteoid) and initiate mineralization. They may become embedded as osteocytes or remain on bone surfaces as lining cells.

Front

Osteoclast

Back

Osteoclasts are large, multinucleated cells responsible for bone resorption, releasing calcium and phosphate into extracellular fluid. Their activity is regulated by signals such as RANKL and inhibited by osteoprotegerin (OPG).

Front

Osteocyte

Back

Osteocytes are former osteoblasts trapped within lacunae that sense mechanical loading and coordinate remodeling. They communicate via canaliculi and regulate osteoblast and osteoclast activity through biochemical signaling.

Front

Periosteum

Back

The periosteum is a fibrous membrane covering bone surfaces except at joints, containing progenitor cells, blood vessels and nerves. It contributes to appositional growth and bone repair after injury.

Front

Endosteum

Back

The endosteum lines the inner surfaces of bone cavities and trabeculae, containing osteogenic cells involved in remodeling and marrow cavity maintenance. It is active in resorption and formation during growth and repair.

Front

Trabecular bone

Back

Trabecular (spongy) bone has a porous network of trabeculae optimized for metabolic exchange and shock absorption. It shows rapid turnover and is particularly affected by age-related loss and metabolic disease.

Front

Compact bone

Back

Compact bone forms dense outer layers of bones, organized into osteons that provide stiffness and resistance to bending. It contains fewer voids than trabecular bone and bears most of the structural loads.

Front

Endochondral ossification

Back

Endochondral ossification is the process by which most long bones develop from cartilage templates that are progressively mineralized and replaced by bone. It is essential for longitudinal growth of limbs and vertebrae.

Front

Intramembranous ossification

Back

Intramembranous ossification forms flat bones (e.g., parts of the skull and clavicle) directly from mesenchymal condensations without a cartilage intermediate. It contributes to cranial vault growth and fontanelle closure.

Front

RANK/RANKL/OPG

Back

This signaling system regulates osteoclastogenesis: RANKL from osteoblast-lineage cells binds RANK on osteoclast precursors to stimulate differentiation, while OPG acts as a decoy receptor inhibiting this interaction. The balance controls bone resorption rates.

Front

Bone matrix

Back

Bone matrix comprises organic components (mainly collagen type I and non-collagenous proteins) and inorganic minerals (primarily hydroxyapatite crystals). Organic matrix provides tensile strength; mineral provides stiffness and compressive resistance.

Front

Hematopoiesis

Back

Hematopoiesis is the production of blood cells occurring in bone marrow, especially in trabecular regions of axial skeleton and proximal limb bones. The marrow niche interacts with bone cells influencing both blood and bone physiology.

Front

Odontogenesis

Back

Odontogenesis is the complex developmental process of tooth formation involving reciprocal interactions between oral ectoderm and cranial neural-crest-derived mesenchyme. It results in formation of enamel, dentin, pulp and supporting tissues with precise chronological patterns.

Front

Fluctuating asymmetry

Back

Fluctuating asymmetry refers to small random deviations from bilateral symmetry in paired traits, often reflecting developmental instability or environmental stress during growth. It differs from directional asymmetry, which is consistent bias to one side.

Front

Epigenetic traits

Back

In osteology, epigenetic traits are minor nonmetric anatomical variations influenced by genetic and environmental factors. They serve as population-level markers for biological variability and can inform kinship and activity patterns when used cautiously.

Front

Saponification

Back

Saponification is the transformation of fatty tissues into adipocere under moist, anaerobic conditions, slowing decomposition and preserving body shape. It is an important tafonomic pathway affecting soft-tissue and bone preservation.

Front

Osteomalacia

Back

Osteomalacia is defective mineralization of bone matrix in adults, typically due to vitamin D deficiency, causing soft, weakened bones and bone pain. It is distinct from osteoporosis, which is characterized by reduced bone mass and microarchitectural deterioration.

Front

Secular trend

Back

A secular trend describes temporal changes in growth and morphology across generations, often seen as increased stature or altered cranial dimensions due to nutrition and socioeconomic shifts. It exemplifies skeletal plasticity in human populations.