The Skeletal System: Bone Tissue (Chapter 6)

A set of vocabulary flashcards summarizing essential terms and definitions from Chapter 6—The Skeletal System: Bone Tissue, covering bone structure, cell types, growth, remodeling, calcium regulation, and common disorders.

Bone (Osseous Tissue)

A connective tissue whose hardened matrix forms the structural component of bones.

Skeletal System

The entire framework of bones and their cartilages that supports and protects the body.

Axial Skeleton

Portion of the skeleton forming the long axis of the body (skull, vertebral column, thoracic cage).

Appendicular Skeleton

Bones of the limbs and girdles that are appended to the axial skeleton.

Long Bone

Bone with greater length than width (e.g., femur, humerus).

Short Bone

Nearly equal in length and width (e.g., carpals, tarsals).

Flat Bone

Thin, flattened bone (e.g., sternum, cranial bones).

Irregular Bone

Complex-shaped bone (e.g., vertebra, facial bones).

Sesamoid Bone

Small bone embedded in a tendon (e.g., patella).

Diaphysis

The shaft or long main portion of a long bone.

Epiphysis

The enlarged end of a long bone at a joint.

Metaphysis

Region between diaphysis and epiphysis; contains the epiphyseal plate/line.

Articular Cartilage

Hyaline cartilage covering epiphyses that reduces friction at joints.

Periosteum

Connective tissue membrane surrounding the bone’s exterior except at joints.

Medullary Cavity

Hollow space within the diaphysis containing yellow marrow in adults.

Endosteum

Thin membrane lining the medullary cavity and internal bone surfaces.

Extracellular Matrix (Bone)

Material surrounding bone cells; ~15 % water, 30 % collagen fibers, 55 % mineral salts.

Collagen Fibers

Protein fibers that give bone flexibility and tensile strength.

Hydroxyapatite

Crystallized calcium phosphate salts that make bone hard and rigid.

Osteoprogenitor Cell

Bone stem cell that differentiates into an osteoblast.

Osteoblast

Bone-building cell that secretes bone matrix.

Osteocyte

Mature bone cell that maintains bone tissue.

Osteoclast

Large cell that resorbs and breaks down bone matrix.

Compact Bone

Dense outer layer of bone composed of osteons; provides strength and support.

Spongy (Cancellous) Bone

Lightweight bone with trabeculae; houses red bone marrow.

Trabeculae

Lattice-like plates of spongy bone oriented along lines of stress.

Osteon (Haversian System)

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

Central (Haversian) Canal

Channel in an osteon containing blood vessels and nerves.

Concentric Lamellae

Rings of calcified matrix in an osteon.

Lacuna

Tiny cavity between lamellae housing an osteocyte.

Canaliculi

Microscopic channels connecting lacunae for nutrient and waste exchange.

Perforating (Volkmann’s) Canal

Transverse canal carrying blood vessels from periosteum into bone.

Periosteal Artery

Blood vessel that supplies the periosteum and outer compact bone.

Nutrient Foramen

Opening through which the nutrient artery enters the diaphysis.

Intramembranous Ossification

Bone development directly from mesenchyme; forms flat bones of skull, mandible, clavicle.

Endochondral Ossification

Bone formation replacing a hyaline cartilage model; produces most bones.

Interstitial Growth

Lengthwise bone growth at the epiphyseal plate.

Appositional Growth

Increase in bone diameter via osteoblasts in periosteum and osteoclasts in endosteum.

Wolff’s Law

Principle that bone remodels according to the mechanical stresses placed upon it.

Bone Remodeling

Ongoing replacement of old bone tissue by osteoclasts and osteoblasts.

Fracture Hematoma

Blood clot that forms at the site of a bone break during the reactive phase.

Fibrocartilaginous Callus

Soft callus bridging broken bone ends in the reparative phase.

Bony (Hard) Callus

Spongy bone replacing the soft callus during fracture repair.

Hemopoiesis

Blood cell production occurring in red bone marrow.

Parathyroid Hormone (PTH)

Hormone that raises blood calcium by stimulating osteoclast activity and calcitriol formation.

Calcitriol

Active vitamin D produced by kidneys; increases intestinal calcium absorption.

Calcitonin

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

Osteoporosis

Disease characterized by decreased bone mass and increased fracture risk.

Rickets

Childhood disorder caused by vitamin D deficiency leading to soft, deformed bones.

Osteomalacia

Adult soft-bone condition due to inadequate mineralization (often vitamin D deficiency).

Growth Hormone

Pituitary hormone stimulating overall growth and IGF production for bone development.

Insulin-Like Growth Factors (IGFs)

Liver- and bone-derived proteins that promote osteoblast activity and bone growth.

Weight-Bearing Exercise

Physical activity that stimulates osteoblasts, increasing bone mass and strength.

Aging (Bone)

Process in which bone resorption outpaces deposition, leading to reduced bone mass, especially after menopause.