Chapter 7 Skeletal System Vocabulary

Vocabulary flashcards defining key structures, cell types, growth mechanisms, hormones, and conditions related to the skeletal system.

Compact bone

Dense or cortical connective tissue that appears white, smooth, and solid, accounting for 80% of total bone mass.

Spongy bone

Cancellous or trabecular bone located internal to compact bone that appears porous and constitutes 20% of bone mass.

Long bones

The most common bone shape, characterized by having a length greater than width and an elongated, cylindrical shaft called the diaphysis.

Diaphysis

The elongated, cylindrical shaft of a long bone.

Central canal

A cylindrical channel at the center of and parallel to an osteon through which blood vessels and nerves extend.

Concentric lamellae

Rings of bone connective tissue surrounding the central canal with collagen fibers oriented 90 degrees from adjacent lamellae to give bone strength and resilience.

Osteocytes

Mature bone cells found in small spaces (lacunae) between concentric lamellae that maintain the bone matrix.

Lacunae

Small spaces located between concentric lamellae that house osteocytes.

Canaliculi

Tiny, interconnecting channels within bone connective tissue extending from lacunae that house osteocyte projections to allow intercellular contact and exchange of nutrients, minerals, gases, and wastes.

Perforating canals

Canals (also called Volkmann canals) running perpendicular to central canals that contain blood vessels and nerves to connect central canals within different osteons.

Circumferential lamellae

Rings of bone running the entire circumference of the bone, classified as external (immediately internal to the periosteum) or internal (internal to the endosteum).

Interstitial lamellae

Incomplete components of compact bone with no central canal located between osteons, representing left-over or partially resorbed osteons.

Trabeculae

An open lattice of narrow rods and plates of bone in spongy bone that forms a crisscrossing meshwork resistant to stress, with spaces filled by bone marrow.

Chondroblasts

Cells within cartilage connective tissue that produce the cartilage matrix.

Chondrocytes

Matrix-encased cartilage cells occupying lacunae that maintain the cartilage matrix.

Perichondrium

A layer of dense irregular connective tissue covering cartilage that helps maintain its shape.

Ossification

The process of bone connective tissue formation and development (also called osteogenesis), which begins in the embryo and forms the skeleton by the 8th through 12th weeks.

Interstitial growth

Bone growth in length that occurs specifically within Zone 2 (proliferating cartilage) and Zone 3 (hypertrophic cartilage) of the epiphyseal plate.

Appositional growth

Bone growth in diameter or thickness occurring within the periosteum through the deposition of external circumferential lamellae.

Epiphyseal line

An internal thin line of compact bone that remains as a remnant of the epiphyseal plate after interstitial growth ceases at maturity.

Bone remodeling

The continuous process of bone replacement occurring at periosteal and endosteal surfaces throughout adulthood, renewing 20% of the skeleton yearly.

Growth hormone

A hormone (somatotropin) produced by the anterior pituitary gland that stimulates the liver to produce somatomedin, directly stimulating cartilage growth in the epiphyseal plate.

Calcitriol

A hormone produced via kidney conversion that increases blood calcium levels by stimulating absorption of calcium ions from the small intestine into the blood.

Parathyroid hormone

A hormone secreted by parathyroid glands in response to reduced blood calcium that accelerates calcitriol conversion and acts synergistically with calcitriol to increase osteoclast activity.

Calcitonin

A hormone released by the thyroid gland in response to high blood calcium levels or exercise that lowers blood calcium by inhibiting osteoclasts and increasing urinary calcium loss.

Osteopenia

An age-related decline in bone mass due to insufficient ossification, beginning around age 35–40 as osteoblast activity declines while osteoclast activity remains steady.

Osteoporosis

A condition characterized by a reduction in bone mass sufficient to compromise normal function.