LP2A: Skeletal System: Bone Histology & Physiology

Vocabulary flashcards generated from the skeletal system lecture notes covering anatomy, histology, cellular matrix, hormonal regulation, exercise principles, and skeletal pathologies.

Joints (Articulations)

Places where two or more bones come together or articulate.

Lever

A mechanical system consisting of a rigid rod, a pivot or fulcrum, an object moved against resistance, and a force that supplies energy for movement.

Third Class Lever

A lever system where the applied force is located between the fulcrum and the resistance; it represents the majority of anatomical levers in the human body.

Red Marrow

Soft connective tissue located in bone spaces that functions in the formation of red blood cells, white blood cells, and blood platelets.

Yellow Marrow

Connective tissue inside the medullary cavity that stores fat as an energy reserve and is inactive in blood cell formation.

Diaphysis

The long, straight shaft portion of a long bone, composed mainly of dense compact bone surrounding the medullary cavity.

Epiphysis

An expanded structure located at each end of a long bone that articulates with another bone.

Epiphyseal Disk (Plate)

A band of hyaline cartilage located between the diaphysis and epiphysis of an immature long bone that allows longitudinal growth to continue.

Trabeculae

Extensive networks of bony plates and rods within spongy bone that are oriented along stress lines to withstand forces from multiple directions.

Articular Cartilage

A layer of avascular and aneural hyaline cartilage covering the joint surface of an epiphysis to provide a frictionless surface.

Periosteum

A tough, vascular covering of fibrous connective tissue that surrounds a bone except for its articular surfaces, assisting in bone formation and repair.

Endosteum

A thin membrane lining the medullary cavity and spongy bone spaces, containing a single layer of bone-forming cells.

Osteoclasts

Giant multinucleated bone-destroying cells that resorb bone tissue by secreting lysosomal enzymes and acids at their ruffled border.

Osteoblasts

Bone-forming cells that produce new bone matrix components during osteogenesis.

Osteocytes

Mature bone cells located in lacunae that maintain the mineral and protein content of the matrix and participate in bone repair.

Osteoprogenitor Cells

Stem cells that divide and differentiate into osteoblasts.

Hydroxyapatite

Extremely hard, inflexible crystals formed by the interaction of calcium phosphate and calcium hydroxide, accounting for approximately $\frac{2}{3}$ of bone weight.

Canaliculi

Narrow passageways extending through the matrix between lacunae and blood vessels for the exchange of nutrients, waste, and gases.

Parathyroid Hormone (PTH)

A hormone released in response to low blood calcium levels that stimulates osteoclasts to resorb bone and release calcium into the bloodstream.

Calcitonin

A hormone secreted by the thyroid gland during high blood calcium conditions that inhibits osteoclasts and promotes bone matrix deposition.

Bone Remodeling

The continual process of bone resorption and deposition that replaces $10-30\%$ of an adult skeleton each year.

Bone Mass

The overall quantitative amount of bone tissue present in the body.

Bone Mineral Density (BMD)

The relative value or absolute amount of hydroxyapatite per measured bone area.

Weight-Bearing Exercise

Movement in which body weight is supported against gravity, imposing impact loading on the skeleton to stimulate bone deposition.

Osteopenia

A clinical condition of reduced bone mineral density defined as BMD between $1$ and $2.5$ standard deviations below values for young, normal adults.

Osteoporosis

A metabolic bone condition characterized by increased porosity and decreased bone mineral density exceeding $2.5$ standard deviations below values for young, normal adults.

Primary Amenorrhea

A state of altered menstrual function defined as late or delayed menarche.

Secondary Amenorrhea

The cessation of menstruation or menstrual periods occurring at intervals greater than $90\,days$ following established regular cycles.

Stress Reaction

A maladaptive area of bone hyperactivity caused by overuse where the balance between resorption and deposition is progressively lost such that resorption exceeds deposition.

Stress Fracture

A clinically symptomatic hairline break in bone occurring in the absence of acute trauma due to persistent uncoupling of bone remodeling.

Macrotrauma

Sudden, acute skeletal injuries resulting from a single traumatic impact.

Microtrauma

Overuse skeletal injuries resulting from chronic, repetitive overtraining.