Chapter 06 - Skeletal System: Bones and Bone Tissue

Vocabulary practice flashcards covering bone anatomical features, microscopic histology, ossification processes, remodeling mechanisms, calcium homeostasis, and skeletal pathologies from Chapter 6.

Diaphysis

The shaft of a long bone, composed primarily of compact bone surrounding the medullary cavity.

Epiphysis

The expanded end of a long bone, primarily consisting of spongy bone covered by an outer layer of compact bone.

Medullary Cavity

The internal cavity within the diaphysis containing red bone marrow in children and yellow bone marrow in adults.

Epiphyseal Plate

A growth plate composed of hyaline cartilage located between the epiphysis and diaphysis, present until bone growth in length stops.

Epiphyseal Line

The ossified remnant of the epiphyseal plate that forms when bone stops growing in length.

Periosteum

A double-layered connective tissue membrane covering the outer surface of a bone, containing blood vessels, nerves, and bone cells.

Perforating Fibers

Collagen bundles, also known as Sharpey's fibers, that penetrate into the bone matrix to firmly attach the periosteum and tendons to bone.

Endosteum

A single cellular layer of connective tissue lining internal bone surfaces, including cavities in spongy bone and the medullary cavity.

Osteoblasts

Bone-forming cells derived from osteochondral progenitor cells that secrete osteoid matrix and facilitate hydroxyapatite deposition.

Osteocytes

Mature, stellate bone cells located within lacunae that maintain the bone matrix and communicate via canaliculi.

Osteoclasts

Large, multinucleated cells derived from monocytes that resorb bone by pumping ions and releasing enzymes across a ruffled border.

Hydroxyapatite

The primary inorganic mineral constituent of bone matrix, consisting of calcium phosphate crystals with the formula $\text{Ca}_{10}(\text{PO}_4)_6(\text{OH})_2$, providing compression resistance.

Osteon

The functional structural unit of compact bone, consisting of concentric lamellae surrounding a blood vessel-filled central canal.

Central Canal

A longitudinal channel running parallel to the long axis of an osteon containing blood vessels and nerves.

Perforating Canals

Channels, also called Volkmann's canals, that run perpendicular to the long axis of bone to deliver blood from the periosteum to central canals.

Trabeculae

Interconnecting rods or plates of bone matrix forming scaffolding in spongy bone, oriented along lines of stress.

Chondroblasts

Cells that actively produce cartilage matrix.

Chondrocytes

Mature cartilage cells embedded in lacunae within the extracellular matrix.

Perichondrium

A double-layered connective tissue sheath covering cartilage, except at joint articulations.

Appositional Growth

Growth in diameter or thickness caused by the deposition of new matrix onto the periphery or surface of existing tissue.

Interstitial Growth

Growth from within tissue caused by cell division and secretional addition of matrix between existing cells.

Endochondral Ossification

The process of bone formation in which a pre-existing hyaline cartilage model is broken down and replaced by bone tissue.

Intramembranous Ossification

The process of bone formation that occurs within embryonic connective tissue membranes derived from mesenchyme.

Fontanels

Large, unossified membrane-covered soft spots between developing cranial bones in fetuses and infants.

Zone of Resting Cartilage

The epiphyseal plate region nearest the epiphysis containing slowly dividing chondrocytes.

Zone of Proliferation

The region of the epiphyseal plate where chondrocytes rapidly divide and arrange into columns on the epiphyseal side.

Zone of Hypertrophy

The region of the epiphyseal plate where chondrocytes mature and enlarge significantly.

Zone of Calcification

The region of the epiphyseal plate where the cartilage matrix calcifies and chondrocytes undergo apoptosis.

Rickets

A pediatric condition caused by Vitamin D deficiency that causes soft, flexible, and deformed bones due to poor calcium absorption.

Osteomalacia

An adult condition resulting from Vitamin D deficiency that causes softening of bones due to impaired mineralization.

Scurvy

A nutritional deficiency of Vitamin C that impairs collagen synthesis by osteoblasts, leading to soft bones, weak skin, and loose teeth.

Parathyroid Hormone

A hormone released by parathyroid glands when blood calcium drops below $8.5\text{\text{ mg/dL}}$, raising calcium levels by activating osteoclasts and conserving calcium in kidneys.

Calcitonin

A hormone secreted by thyroid C cells when blood calcium rises above $11\text{\text{ mg/dL}}$, lowering calcium levels by inhibiting osteoclasts and promoting kidney excretion.

Calcitriol

The active hormone produced from Vitamin D3 in the kidneys that increases calcium absorption in the small intestine.

Osteoporosis

A disorder marked by severe loss of bone mass and matrix density, leading to porous, brittle bones prone to fracture.

Gigantism

An abnormally tall stature resulting from excessive growth hormone secretion during childhood growth years.

Foramen

A rounded opening or passageway through a bone for nerves and blood vessels.

Fossa

A shallow depression on a bone surface.

Condyle

A smooth, rounded articular surface on a bone that joins with another bone.

Trochlea

A smooth, grooved articular process shaped like a pulley.

Sinus

An air-filled cavity within a skull bone lined by a mucous membrane.

Comminuted Fracture

A fracture where the bone breaks into three or more pieces or fragments.

Greenstick Fracture

An incomplete fracture where one side of the bone breaks while the opposite side bends, typical in children.

Hematoma

A mass of clotted blood confined within an organ or tissue space formed following vascular injury during a fracture.

Callus

A connective tissue mass formed at a bone fracture site that connects and stabilizes the broken ends during repair.