Chapter 7 – Skeletal System: Bone Structure and Function

Vocabulary flashcards covering key terms from Chapter 7 on bone structure, cell types, matrix components, growth, remodeling, hormones, and common disorders.

Skeletal System

The body system composed of bones, cartilages, and ligaments that supports, protects, and enables movement.

Osseous Tissue

Connective tissue whose matrix is hardened by calcium phosphate and other minerals; commonly called bone tissue.

Cartilage

Resilient connective tissue that precedes most bones in development and covers many joint surfaces in adults.

Ligament

Band of dense regular connective tissue that anchors bone to bone at joints.

Tendon

Dense regular connective tissue that attaches muscle to bone.

Compact Bone

Dense, outer shell of bone that makes up roughly three-fourths of the skeleton’s weight.

Spongy (Cancellous) Bone

Loosely organized bone tissue found in the interior of most bones; contains trabeculae and marrow spaces.

Diaphysis

The shaft of a long bone that provides leverage and encloses the medullary cavity.

Epiphysis

Expanded end of a long bone that strengthens the joint and anchors ligaments and tendons.

Medullary (Marrow) Cavity

Central cavity within the diaphysis of a long bone that houses bone marrow.

Articular Cartilage

Thin layer of hyaline cartilage covering the joint surface of an epiphysis; reduces friction.

Periosteum

Fibrous outer sheath covering bone except at articular surfaces; contains osteogenic layer.

Endosteum

Thin reticular connective tissue lining internal bone surfaces and marrow cavities.

Epiphyseal Plate

Hyaline cartilage plate between epiphysis and diaphysis in children; site of longitudinal growth.

Epiphyseal Line

Remnant of the epiphyseal plate in adults after cartilage is replaced by bone.

Osteogenic Cell

Bone stem cell found in periosteum and endosteum that divides to produce osteoblasts.

Osteoblast

Bone-forming cell that secretes osteoid and promotes mineralization; becomes an osteocyte when trapped.

Osteocyte

Mature bone cell residing in lacunae; maintains bone matrix and senses mechanical stress.

Lacuna

Tiny cavity within bone matrix housing an osteocyte.

Canaliculi

Microscopic channels that connect lacunae and allow osteocytes to exchange nutrients and signals.

Osteoclast

Large, multinucleate cell derived from hematopoietic stem cells that resorbs bone.

Resorption Bay (Howship’s Lacuna)

Depression on bone surface where an active osteoclast resides.

Hydroxyapatite

Crystallized calcium phosphate salt (Ca10(PO4)6(OH)2) that forms the inorganic component of bone matrix.

Collagen

Primary organic protein fiber in bone that provides tensile strength and flexibility.

Osteoid

Unmineralized organic portion of bone matrix produced by osteoblasts.

Osteon (Haversian System)

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

Lamella

Layer of bone matrix in an osteon.

Central (Haversian) Canal

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

Trabecula

Thin plate or strut of bone within spongy bone; oriented along lines of stress.

Bone Marrow

Soft tissue occupying marrow cavities and spongy bone spaces; can be red (hemopoietic) or yellow (fatty).

Hemopoietic Tissue

Blood-forming tissue found chiefly in red bone marrow.

Intramembranous Ossification

Bone development within fibrous membranes; forms flat skull bones and clavicles.

Endochondral Ossification

Bone formation by replacing a hyaline cartilage model; produces most bones below the skull.

Interstitial Growth

Lengthwise growth of long bones occurring at the epiphyseal plate.

Appositional Growth

Increase in bone thickness by addition of new layers under the periosteum.

Bone Remodeling

Continuous process of bone resorption and deposition carried out by osteoclasts and osteoblasts.

Mineralization (Deposition)

Process by which osteoblasts deposit minerals onto collagen fibers, hardening the matrix.

Mineral Resorption

Osteoclast-mediated process of dissolving bone and releasing minerals into the bloodstream.

Wolff’s Law

Principle that bone grows or remodels in response to mechanical stress.

Calcitriol

Active form of vitamin D that raises blood calcium by increasing intestinal absorption and stimulating osteoclasts.

Calcitonin

Thyroid hormone that lowers blood calcium by inhibiting osteoclasts and stimulating osteoblasts.

Parathyroid Hormone (PTH)

Hormone released by parathyroid glands that raises blood calcium mainly by stimulating osteoclast activity.

Osteoporosis

Bone disease characterized by decreased bone mass and increased fracture risk due to resorption exceeding deposit.

Osteomalacia

Adult condition of inadequate mineralization leading to soft bones; often due to vitamin D deficiency.

Rickets

Childhood form of osteomalacia causing bowed legs and skeletal deformities.

Achondroplastic Dwarfism

Genetic disorder where long bones stop growing in childhood; normal torso, short limbs.

Pituitary Dwarfism

Short stature with normal body proportions caused by growth hormone deficiency.

Osteogenesis (Ossification)

General term for the formation of new bone tissue.

Fracture – Displaced

Break in which bone ends are out of normal alignment.

Fracture – Nondisplaced

Break in which bone ends retain their normal position.

Fracture – Open (Compound)

Fracture in which bone pierces the skin.

Fracture – Closed (Simple)

Fracture that does not penetrate the skin.

Inorganic matter

85% hydroxyapatite.

Organic matter

Mostly collagen and carbohydrate