🦴 | Chapter 6: Skeletal System and Bone Physiology

Vocabulary flashcards covering major terms and concepts from Chapter 6 on the skeletal system, including bone structure, cells, growth processes, hormonal regulation, disorders, and fracture repair.

Axial Skeleton

Skeletal division including skull, vertebral column, and thoracic cage.

Appendicular Skeleton

Skeletal division of limbs and girdles (pectoral/pelvic).

Structural Support (Skeletal Function)

Provides body framework and attachment for soft tissues/organs.

Protection (Skeletal Function)

Encloses and safeguards vital organs such as the brain, heart, and lungs.

Leverage (Skeletal Function)

Muscles use bones as levers to produce movement.

Blood Cell Production

Formation of blood cells in red bone marrow (hematopoiesis).

Mineral and Lipid Storage

Reservoir for calcium, phosphate, and lipid reserves (yellow marrow).

Sutural Bone

Small, flat bone found between the flat bones of the skull.

Irregular Bone

Bone with complex shape, e.g., vertebrae and pelvic bones.

Short Bone

Small, boxy bone such as carpal and tarsal bones.

Flat Bone

Thin, parallel surfaces; forms roof of skull, ribs, sternum, scapulae.

Long Bone

Elongated bone; found in limbs such as femur, humerus, tibia.

Sesamoid Bone

Small, seed-shaped bone that develops in tendons; example: patella.

Bone Tissue (Osseous Tissue)

Connective tissue composed of cells and an organic-inorganic extracellular matrix.

Collagen Fibers

Organic component (≈35%) that provides tensile strength and flexibility to bone.

Hydroxyapatite

Inorganic mineral salts (≈65%) that give bone its hardness and compressive strength.

Osteogenic Cell

Bone stem cell producing osteoblasts; found in periosteum/endosteum.

Osteoblast

Bone-forming cell; secretes osteoid for bone mineralization.

Osteocyte

Mature bone cell in lacuna; maintains matrix via canaliculi.

Osteoclast

Dissolves bone matrix via osteolysis, releasing calcium and phosphate.

Compact Bone

Dense outer bone layer composed of osteons; provides strength for weight bearing.

Spongy (Cancellous) Bone

Internal lattice of trabeculae; lighter and houses red or yellow marrow.

Osteon (Haversian System)

Structural unit of compact bone consisting of concentric lamellae around a central canal.

Lamellae

Concentric rings of calcified matrix in an osteon.

Lacuna

Small cavity housing an osteocyte within bone matrix.

Canaliculi

Microscopic canals that connect lacunae and allow nutrient/waste exchange.

Central (Haversian) Canal

Channel in the center of an osteon containing blood vessels and nerves.

Trabecula

Thin struts or plates forming the lattice of spongy bone.

Diaphysis

Shaft of a long bone composed mainly of compact bone surrounding the medullary cavity.

Metaphysis

Narrow region connecting diaphysis to epiphysis; contains growth plate in children.

Epiphysis

Expanded end of long bone, mostly spongy bone.

Epiphyseal Line

Adult bone mark from epiphyseal plate, indicating ceased growth.

Articular Cartilage

Hyaline cartilage covering epiphyses where bones articulate, reducing friction.

Medullary Cavity

Central cavity within diaphysis containing red or yellow marrow.

Periosteum

Fibrous membrane covering bone (except joints), containing osteogenic cells and vessels.

Endosteum

Thin membrane lining medullary cavity and trabeculae; site of bone growth and remodeling.

Nutrient Artery

Major vessel entering the diaphysis to supply bone tissue.

Endochondral Ossification

Process in which hyaline cartilage is replaced by bone; forms most skeletal bones.

Intramembranous Ossification

Bone development from mesenchymal tissue; forms flat bones like skull and clavicle.

Ossification

General process of bone formation by osteoblasts.

Appositional Growth

Bone growth in diameter via addition of new bone at the periosteal surface.

Interstitial Growth

Lengthwise growth of long bones occurring at the epiphyseal plates.

Pituitary Growth Failure

Short stature due to insufficient growth hormone during childhood.

Marfan Syndrome

Genetic disorder causing excessive cartilage formation; results in tall stature and long limbs.

Gigantism

Excess growth hormone before puberty leading to extreme height.

Acromegaly

Excess growth hormone after epiphyseal closure causing bone thickening in face, jaw, hands.

Internal Callus

Spongy bone and cartilage bridge forming inside the medullary cavity during repair.

External Callus

Cartilage and bone collar forming around the outside of a fracture site.

Parathyroid Hormone (PTH)

Hormone that raises blood calcium by stimulating osteoclasts, kidneys, and intestines.

Calcitonin

Thyroid hormone lowering blood calcium through osteoclast inhibition

Calcitriol

Active form of vitamin D that increases intestinal absorption of calcium.

Red Bone Marrow

Hematopoietic tissue producing red and white blood cells and platelets.

Yellow Bone Marrow

Adipose-rich marrow serving as an energy reserve.

Osteoid

Unmineralized organic matrix secreted by osteoblasts.

RANKL (Receptor Activator of Nuclear factor κB Ligand)

Signal from osteoblasts promoting osteoclast differentiation.

Bone Remodeling

Continuous bone turnover for structural adaptation and calcium balance.