Skeletal System, Bone Homeostasis, and Muscular Physiology

Comprehensive vocabulary flashcards reviewing skeletal histology, ossification, bone calcium regulation, and muscular system neurophysiology.

Hemopoiesis

The production of blood cells occurring within the red bone marrow.

Proteoglycans

Molecules found in the extracellular matrix of cartilage that store water and allow the tissue to withstand compressive force.

Hyaline Cartilage

A type of cartilage located at the ends of long bones that provides firm support and creates a smooth articular surface.

Fibrocartilage

Cartilage located in the pubic symphysis and intervertebral discs that functions primarily as a cushion.

Osteoblasts

Bone-building cells that secrete collagen and lay down new bone tissue.

Osteocytes

Mature bone cells trapped within lacunae that maintain bone structure.

Osteoclasts

Bone-dissolving cells referred to as the demolition crew that remove worn-out bone by phagocytosis and secreting acids and protein-digesting enzymes.

Hydroxyapatite Crystals

Bone minerals composed of calcium and phosphate crystals that provide compressive, weight-bearing strength.

Intramembranous Ossification

A pattern of bone development occurring in the skull from eight weeks fetal to age two, where bone tissue forms directly within dense connective tissue.

Endochondral Ossification

A developmental process occurring from eight weeks to age 18 where a hyaline cartilage model is replaced by bone, forming long bones and most of the skeleton.

Interstitial Growth

Bone growth in length occurring at the epiphyseal plate via chondrocyte mitosis and subsequent ossification.

Appositional Growth

The process of bone growth in diameter regulated by the activity of osteoblasts and osteoclasts.

Parathyroid Hormone (PTH)

A hormone produced by the parathyroid glands that increases blood calcium levels when calcium is low.

Calcitonin

A hormone secreted by the thyroid gland that decreases blood calcium levels via a negative feedback mechanism.

Pituitary Dwarfism

A condition caused by the hyposecretion of growth hormone in childhood that leads to rapid calcification of the epiphyseal plates.

Cretinism

A condition characterized by dwarfism and mental retardation caused by hypothyroidism during childhood.

Bone Remodeling

The removal of existing bone by osteoclasts coupled with the deposition of new bone by osteoblasts to adapt to mechanical stress, repair fractures, and maintain mineral balance.

Excitability

The ability of a cell to respond to a stimulus by generating a membrane signal called an action potential.

Action Potential

An electrochemical signal conducted along an excitable cell's membrane without decreasing in magnitude.

Epimysium

The outermost connective tissue sheath that covers an entire skeletal muscle.

Perimysium

The connective tissue covering that surrounds a muscle fascicle.

Endomysium

The innermost connective tissue layer that surrounds individual muscle fibers.

Leak Channel

A membrane channel protein that is always open and continuously permeable to specific ions.

Voltage-Gated Channel

A membrane channel that opens or closes specifically in response to changes in membrane potential.

Resting Membrane Potential

The polarized state of a resting neuron axon, characterized by a more negative charge inside relative to the outside.

$Na^+/K^+$ Pump

An active transport mechanism that maintains resting membrane potential by pumping $3\,Na^+$ out of the cell for every $2\,K^+$ transported in.