Introduction to the Skeletal System (Chapter 7) - Vocabulary Flashcards

A set of vocabulary flashcards covering major skeletal system terms, bone tissue architecture, cartilage, bone growth and ossification, bone remodeling, and aging-related changes.

Skeletal system components

Bones, cartilage, ligaments, and other connective tissues that stabilize or connect the bones.

Compact bone

Dense, cortical bone tissue; makes up about 80% of bone mass and appears white, smooth, and solid.

Spongy bone

Cancellous or trabecular bone; porous and located internal to compact bone; about 20% of bone mass.

Hyaline cartilage

Glassy cartilage that attaches ribs to the sternum, covers ends of some bones, and is the growth plate; avascular in adults.

Fibrocartilage

Weight-bearing cartilage that withstands compression; forms intervertebral discs, pubic symphysis, and knee cartilage pads.

Ligament

Dense regular connective tissue that connects bone to bone and stabilizes joints.

Tendon

Dense regular connective tissue that connects muscle to bone and transmits muscle force.

Periosteum

Tough outer covering of a bone with an outer fibrous layer and an inner cellular layer; anchors vessels and ligaments; growth in width.

Endosteum

Lining of the internal bone surfaces within the medullary cavity; contains osteoprogenitor cells and osteoblasts.

Medullary (marrow) cavity

Central hollow cavity in the diaphysis; contains red marrow in children and yellow marrow in adults.

Articular cartilage

Hyaline cartilage covering joint surfaces to reduce friction and absorb shock.

Epiphyseal plate (growth plate)

Hyaline cartilage plate in juvenile bones that enables growth in length; ossifies to form the epiphyseal line.

Epiphyseal line

Remnant of the epiphyseal plate in adults indicating completion of growth in length.

Perforating fibers (Sharpey’s fibers)

Collagen fibers that anchor the periosteum to the underlying bone.

Nutrient foramen

Opening through which a nutrient artery and vein enter/exit the bone.

Osteoprogenitor cells

Bone stem cells derived from mesenchyme; differentiate into osteoblasts.

Osteoblasts

Bone-forming cells that secrete osteoid; eventually become osteocytes.

Osteocytes

Mature bone cells housed in lacunae; maintain the bone matrix and sense mechanical stress.

Osteoclasts

Multinucleated cells that resorb bone; derived from fused bone marrow cells.

Osteoid

Organic bone matrix produced by osteoblasts; composed of collagen and ground substance.

Hydroxyapatite

Inorganic calcium phosphate crystals that harden the bone matrix and provide rigidity.

Osteon (Haversian system)

The structural unit of compact bone, centered on the Haversian canal.

Central (Haversian) canal

Cylindrical channel at the center of an osteon containing blood vessels and nerves.

Lamellae

Concentric rings of bone matrix around the central canal; orientation of collagen fibers alternates between rings.

Lacunae

Small spaces that house osteocytes within the bone matrix.

Canaliculi

Small channels connecting lacunae to each other and to the central canal for nutrient/waste exchange.

Perforating (Volkmann) canals

Canals that run perpendicular to the central canals, connecting osteons and distributing vessels/nerve supply.

Interstitial lamellae

Fragments of lamellae between osteons; remnants of remodeling.

Trabeculae

Skeletal rods/plates forming the open lattice of spongy bone; house bone marrow between them.

Perichondrium

Dense irregular connective tissue surrounding cartilage; supplies nutrients and supports cartilage growth; becomes periosteum during bone formation.

Chondroblast

Immature cartilage cell that produces cartilage matrix.

Chondrocyte

Mature cartilage cell residing in a lacuna in cartilage matrix.

Interstitial growth (cartilage)

Growth in length of cartilage from within; chondrocytes divide and push apart, expanding the cartilage length.

Appositional growth (cartilage)

Growth in width along the cartilage periphery by new chondroblasts from the perichondrium.

Intramembranous ossification

Bone formation from mesenchyme; produces flat bones of the skull and part of the clavicle.

Endochondral ossification

Bone formation from a hyaline cartilage model; forms most bones (limbs, vertebrae, pelvis).

Primary ossification center

First site of bone formation in the diaphysis during endochondral ossification.

Secondary ossification centers

Bone formation centers in the epiphyses that develop after birth.

Epiphysis

Ends of a long bone; composed of outer compact bone and inner spongy bone; articular cartilage on joint surfaces.

Diaphysis

Shaft of a long bone; cylindrical, compact bone surrounding the medullary cavity.

Metaphysis

Region between the diaphysis and epiphysis; contains the growth plate in youth.

Hematopoiesis

Blood cell production; occurs primarily in red bone marrow.

Red bone marrow

Hematopoietic tissue that forms blood cells; highly distributed in children; limited in adults.

Yellow bone marrow

Fatty marrow replacing red marrow in the medullary cavity of adults.

Bone remodeling

Continuous replacement of bone tissue by osteoblasts and osteoclasts; influenced by mechanical stress.

Osteoporosis

Disease with reduced bone mineral density; bones become fragile and prone to fracture.

Osteopenia

Lower-than-normal bone mineral density; precursor to osteoporosis.

Calcitonin

Thyroid hormone that inhibits osteoclasts and lowers blood calcium; more relevant in children.

Parathyroid hormone (PTH)

Hormone released in response to low blood calcium; increases blood calcium by promoting bone resorption and renal calcium reabsorption; stimulates calcitriol production.

Calcitriol (active vitamin D)

Active vitamin D; increases intestinal calcium absorption and renal calcium reabsorption; raises blood calcium.

Activation of vitamin D to calcitriol

UV converts 7-dehydrocholesterol to vitamin D3 in skin; liver converts to calcidiol; kidney converts to calcitriol; PTH enhances final step.

Fracture hematoma

Blood clot formed at fracture site from torn vessels.

Fibrocartilaginous (soft) callus

Initial soft bridging callus of collagen and fibrocartilage between fracture ends.

Bony (hard) callus

Hard callus of woven/primary bone deposited by osteoblasts bridging the fracture.

Remodeling (fracture repair)

Final phase; replacement of primary bone with mature compact bone and restoration of strength.