Chapter 6 – Bones and Bone Tissue

Vocabulary flashcards summarizing essential terms and definitions from Chapter 6: Bones and Bone Tissue.

Support (Skeletal Function)

Rigid bones and flexible cartilage provide the structural framework that supports the body.

Protection (Skeletal Function)

Bones such as the skull, ribs, sternum, and vertebrae shield vital organs from injury.

Movement (Skeletal Function)

Skeletal muscles pull on bones via tendons, while ligaments guide and limit joint motion.

Storage (Skeletal Function)

Bones store calcium and phosphate ions; marrow cavities store adipose tissue.

Blood Cell Production

Red bone marrow produces all blood cells and platelets.

Hyaline Cartilage

Most common cartilage; provides smooth surfaces at joints and supports respiratory structures.

Fibrocartilage

Cartilage rich in collagen; resists compression and tension (e.g., intervertebral discs).

Elastic Cartilage

Cartilage containing elastin fibers; flexible (e.g., external ear).

Chondroblast

Immature cartilage cell that secretes new cartilage matrix.

Chondrocyte

Mature cartilage cell located in a lacuna, maintaining the surrounding matrix.

Cartilage Matrix

Extracellular material of cartilage composed of collagen for strength and proteoglycans for resiliency.

Perichondrium

Double-layered connective tissue sheath surrounding cartilage (absent on articular cartilage).

Appositional Cartilage Growth

Addition of new cartilage matrix on the surface by perichondrial chondroblasts.

Interstitial Cartilage Growth

Expansion of cartilage from within as chondrocytes divide and secrete matrix.

Bone Organic Matrix

Approximately 35 % of bone; chiefly collagen and proteoglycans, providing flexibility.

Bone Inorganic Matrix

Approximately 65 % of bone; hydroxyapatite crystals supply hardness and strength.

Osteoblast

Immature bone cell that produces bone matrix during ossification.

Ossification (Osteogenesis)

Process of bone tissue formation by osteoblasts.

Osteocyte

Mature bone cell residing in a lacuna, maintaining bone matrix.

Lacuna

Small cavity within bone or cartilage housing a cell (osteocyte or chondrocyte).

Canaliculi

Tiny canals that connect osteocytes, allowing nutrient and waste exchange via gap junctions.

Osteoclast

Multinucleated bone-resorbing cell derived from monocytes; releases acids and enzymes to dissolve bone.

Mesenchyme (Osteochondral Progenitor)

Embryonic connective tissue cell that can differentiate into chondroblasts or osteoblasts.

Woven Bone

First, immature bone with randomly oriented collagen; formed during fetal development and fracture repair.

Lamellar Bone

Mature bone arranged in thin layers (lamellae) with parallel collagen orientation for greater strength.

Bone Remodeling

Continuous process wherein osteoclasts resorb old bone and osteoblasts deposit new bone.

Trabecular (Spongy) Bone

Lightweight bone of interconnecting rods/plates (trabeculae) filled with marrow; lacks osteons.

Trabecula

Rod or plate of spongy bone oriented along stress lines.

Endosteum

Thin connective tissue membrane lining internal bone surfaces and trabeculae.

Compact Bone

Dense outer bone layer composed of closely packed osteons.

Osteon (Haversian System)

Cylindrical structural unit of compact bone surrounding a central canal.

Central (Haversian) Canal

Longitudinal canal in osteon containing blood vessels and nerves.

Perforating (Volkmann’s) Canal

Transverse canal carrying vessels between osteons, connecting central canals.

Concentric Lamellae

Circular layers of bony matrix forming an osteon.

Interstitial Lamellae

Remnants of older osteons between newer osteons.

Circumferential Lamellae

Large rings of bone just deep to periosteum, encircling the entire bone shaft.

Long Bone

Bone whose length exceeds its width (e.g., femur).

Short Bone

Bone roughly equal in length and width (e.g., carpal bone).

Flat Bone

Thin, broad, often curved bone (e.g., parietal bone).

Irregular Bone

Bone with complex shape (e.g., vertebra, sphenoid).

Sesamoid Bone

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

Epiphysis

End of a long bone; spongy bone interior, outer compact layer, articular cartilage covering joint surface.

Articular Cartilage

Hyaline cartilage covering joint surfaces of bones, reducing friction.

Epiphyseal Plate

Hyaline cartilage growth plate where lengthwise bone growth occurs.

Epiphyseal Line

Remnant of the epiphyseal plate after growth ceases; indicates plate closure.

Diaphysis

Shaft of a long bone composed mainly of compact bone around medullary cavity.

Medullary Cavity

Central hollow of long bone; contains red marrow in children and yellow marrow in most adult limbs.

Periosteum

Dual-layered connective tissue membrane on bone exterior; outer fibrous layer and inner cellular layer.

Sharpey’s Fibers

Collagenous fibers anchoring periosteum to underlying bone and tendon attachments.

Intramembranous Ossification

Bone development directly within a connective tissue membrane (e.g., flat skull bones, mandible).

Endochondral Ossification

Bone development by replacing a cartilage model (e.g., limb bones).

Appositional Bone Growth

Increase in bone diameter via osteoblast activity beneath the periosteum.

Vitamin D

Nutrient essential for intestinal calcium absorption; deficiency causes rickets in children and osteomalacia in adults.

Vitamin C

Vitamin required for collagen synthesis; deficiency leads to scurvy and poor wound healing.

Growth Hormone (GH)

Anterior pituitary hormone stimulating cartilage and appositional bone growth.

Thyroid Hormones (T₃ & T₄)

Hormones necessary for normal growth of all tissues, including bone.

Estrogen & Testosterone

Sex hormones that accelerate growth at puberty and induce epiphyseal plate closure.

Rickets

Childhood disease of soft, bowed bones due to vitamin D deficiency.

Osteomalacia

Adult soft-bone condition from vitamin D deficiency or impaired mineralization.

Scurvy

Connective tissue disorder from vitamin C deficiency; causes brittle bones and tooth loss.

Acromegaly

Adult disorder of excess GH/IGF-1 causing enlarged bones of face, hands, and feet.

Gigantism

Excess GH secretion during childhood leading to abnormal height.

Dwarfism (GH Deficiency)

Short stature due to insufficient growth hormone during childhood.

Mechanical Stress (Bone)

Load on bone that stimulates remodeling and increases bone strength.

Closed Fracture

Bone break that does not penetrate the skin.

Open (Compound) Fracture

Bone break with skin perforation and soft-tissue damage.

Comminuted Fracture

Bone shattered into three or more fragments.

Greenstick Fracture

Incomplete fracture in children where bone bends and breaks on one side.

Calcitonin

Thyroid hormone that lowers blood calcium by inhibiting osteoclast activity.

Parathyroid Hormone (PTH)

Hormone that raises blood calcium by stimulating osteoclasts, renal reabsorption, and calcitriol activation.

Calcitriol

Active vitamin D form that increases intestinal calcium absorption.

Osteoporosis

Disease of porous, fragile bones due to loss of bone matrix.

Osteopenia

Moderate reduction in bone mass preceding osteoporosis.

Osteoarthritis

Degenerative joint condition from wear and tear of articular cartilage.

DEXA-Scan

Dual-energy X-ray absorptiometry test used to measure bone density for osteoporosis diagnosis.