Endochondral Bone Growth and Skeletal Muscle Physiology

Vocabulary flashcards summarizing essential terms from the lecture on fetal cartilage ossification, growth-plate dynamics, and skeletal muscle structure and function.

Endochondral Bone Growth

Process in which bone develops by replacing a cartilage template, typical of long bones.

Hyaline Cartilage

Smooth, glassy cartilage that forms the fetal skeleton and persists at articular surfaces and growth plates.

Primary Osteogenic Center

First region in a cartilage model where osteoblasts begin forming bone tissue.

Growth Plate (Epiphyseal Plate)

Strip of hyaline cartilage between epiphysis and metaphysis that enables longitudinal bone growth until closure.

Epiphysis

The enlarged end of a long bone, located beyond the growth plate.

Metaphysis

Flared region of a long bone just below the growth plate, rich in blood supply.

Diaphysis

The shaft of a long bone, housing the medullary (marrow) cavity.

Chondrocyte

Cartilage cell that resides in a lacuna within the cartilage matrix.

Proliferative Zone

Region of the growth plate where chondrocytes rapidly divide, forming columns of cells.

Hypertrophic Zone

Growth-plate region where chondrocytes enlarge (hypertrophy), driving bone lengthening.

Resting Cartilage

Quiescent layer of chondrocytes on the epiphyseal side of the growth plate.

Apoptosis

Programmed cell death; in growth plates, hypertrophic chondrocytes die by apoptosis.

Calcification Zone

Area of the growth plate where cartilage matrix calcifies after chondrocyte death.

Angiogenesis

Growth of new blood vessels; invades the calcified cartilage bringing in osteoprogenitor cells.

Osteoblast

Bone-forming cell derived from fibroblasts; secretes osteoid and later mineralizes it.

Osteocyte

Mature bone cell derived from an osteoblast after it becomes surrounded by mineralized matrix.

Osteoid

Unmineralized organic matrix secreted by osteoblasts prior to calcification.

Hydroxyapatite Crystals

Calcium-phosphate crystals that harden osteoid, giving bone its rigidity.

Growth Hormone

Pituitary hormone that stimulates chondrocyte proliferation in growth plates.

Thyroid Hormone

Hormone that can also stimulate cartilage growth and maturation in growth plates.

Medullary Cavity

Central hollow region of a long bone containing bone marrow.

Myocyte (Muscle Fiber)

Multinucleated skeletal muscle cell extending from one tendon to another.

Endomysium

Thin connective-tissue layer surrounding each individual myocyte.

Perimysium

Connective-tissue sheath bundling groups of muscle fibers into fascicles.

Epimysium

Outer connective-tissue covering encasing an entire skeletal muscle.

Myofibril

Cylindrical sub-unit within a myocyte composed of repeating contractile filaments.

Myofilament

Protein filament (actin or myosin) that slides to produce muscle contraction.

Sarcolemma

Excitable plasma membrane of a myocyte capable of conducting action potentials.

Transverse (T) Tubule

Invagination of the sarcolemma that carries action potentials deep into the muscle fiber.

Sarcoplasmic Reticulum

Specialized smooth ER in muscle that stores and releases calcium to trigger contraction.

Neuromuscular Junction

Synapse where a motor neuron communicates with a skeletal muscle fiber.

Voltage-Gated Channel

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

Action Potential

Rapid change in membrane voltage that propagates along the sarcolemma and T-tubules.

Satellite Cell

Quiescent myoblast located on a muscle fiber surface; fuses for growth or repair.

Myoglobin

Oxygen-binding pigment in muscle cells, providing an O₂ reserve and giving meat its red color.

Creatine Phosphate

High-energy phosphate reservoir that rapidly regenerates ATP in skeletal muscle.

Beta-Oxidation

Metabolic process by which fatty acids are broken down in mitochondria to generate ATP in muscle.

Glycogen (Carb Loading)

Storage form of glucose within muscle; can be increased before endurance events for rapid energy.