Chapter 6: Bones and Bone Tissue Vocabulary

Vocabulary flashcards covering bone classifications, tissue structures, cell types, matrix components, ossification pathways, growth mechanisms, remodeling, homeostasis, and fracture types from Chapter 6.

Skeletal System

The body system that includes the bones, joints, and supporting tissues, containing typical adult total of $206$ bones.

Hematopoiesis

The process of blood cell formation, occurring within the red bone marrow of bones.

Red Bone Marrow

A tissue consisting of a network of reticular fibers supporting islands of hematopoietic cells, which forms blood cells.

Yellow Bone Marrow

A tissue in bones consisting mostly of blood vessels and adipocytes storing triglycerides.

Long Bones

A classification of bones that are longer than they are wide, such as the humerus and other limb bones.

Short Bones

Bones that are about as long as wide or roughly cube-shaped, such as the carpal bones of the wrist and tarsal bones of the ankle.

Flat Bones

Bones that are thin and broad, including most skull bones, the sternum, and bones of the pelvis.

Irregular Bones

Bones whose shapes do not fit into other shape classes, such as vertebrae.

Sesamoid Bones

Small, flat, oval-shaped bones located within tendons, such as the patella.

Periosteum

An outer dense irregular connective tissue membrane rich in blood vessels and nerves that covers the external surface of bones.

Perforating Fibers

Collagen anchors that penetrate into the bone matrix to securely attach the periosteum to bone.

Diaphysis

The shaft of a long bone surrounding a medullary cavity lined by endosteum.

Medullary Cavity

The hollow space within the diaphysis of a long bone filled with bone marrow and lined by endosteum.

Endosteum

A tissue membrane lining the internal surfaces of bone, including the medullary cavity and trabeculae.

Epiphyses

The expanded ends of a long bone filled with red bone marrow and covered by articular cartilage.

Articular Cartilage

A layer of hyaline cartilage covering the epiphyses of long bones where they form joints.

Compact Bone

Hard, dense outer bone structure that resists linear compression and twisting forces.

Spongy Bone

An inner honeycomb-like bone framework composed of trabeculae that resists stress from multiple directions and houses bone marrow.

Epiphyseal Lines

Remnants of the hyaline cartilage epiphyseal growth plate visible after bone lengthening has ceased.

Epiphyseal Plate

A band of hyaline cartilage located between the epiphysis and diaphysis in growing children and adolescents where longitudinal bone growth occurs.

Diploë

The layer of spongy bone located between two layers of compact bone in flat bones.

Sinuses

Air-filled spaces found inside certain flat and irregular skull bones that decrease bone weight.

Nutrient Foramen

A small hole in the diaphysis of long bones allowing nutrient arteries to enter and supply internal tissue structures.

Bone Marrow Transplantation

A medical procedure in which donor red bone marrow or filtered hematopoietic stem cells are infused intravenously to replace damaged marrow cells.

Inorganic Matrix

The component of bone matrix accounting for about $65\%$ of total bone weight, composed mainly of hydroxyapatite crystals that provide compression resistance.

Hydroxyapatite Crystals

Large mineral crystals with formula $\left[\text{Ca}_{10}(\text{PO}_4)_6(\text{OH})_2\right]$ that give bone ECM its hardness and compressive strength.

Organic Matrix

The component of bone matrix (also called osteoid) making up about $35\%$ of bone weight, consisting of collagen fibers, proteoglycans, glycosaminoglycans, glycoproteins, and osteocalcin to resist tensile and twisting forces.

Osteocalcin

A bone-specific organic matrix protein that binds to calcium ions ($\text{Ca}^{2+}$) and hydroxyapatite crystals to organize the inorganic matrix.

Osteoblasts

Cuboidal to columnar bone-building cells derived from osteogenic cells that perform bone deposition in the inner periosteum and endosteum.

Bone Deposition

The process carried out by osteoblasts of secreting organic matrix components and assisting in inorganic matrix crystallization.

Osteocytes

Mature bone cells trapped in lacunae that maintain the bone extracellular matrix and signal osteoblasts to build bone under tension.

Lacuna

A small cavity in bone matrix housing an osteocyte surrounded by extracellular fluid.

Osteoclasts

Large, multinucleated cells with ruffled borders that carry out bone resorption.

Bone Resorption

The process performed by osteoclasts of breaking down bone ECM by secreting hydrogen ions ($\text{H}^+$) to dissolve minerals and enzymes to degrade organic matrix.

Osteopetrosis

An inherited disorder ("marble bone disease") caused by defective osteoclasts failing to degrade bone, leading to dense, weak, and brittle bone tissue.

Osteons

The basic structural units of compact bone (also called Haversian systems) containing concentric lamellae surrounding a central canal.

Trabeculae

Branching ribs or spicules of bone covered with endosteum that compose spongy bone tissue.

Concentric Lamellae

Rings of thin bone layers within an osteon with collagen fibers running in opposite directions to resist bending and twisting.

Central Canal

A central channel in an osteon lined with endosteum that carries blood vessels and nerves.

Canaliculi

Tiny channels connecting adjacent lacunae, through which cytoplasmic extensions of osteocytes communicate via gap junctions.

Interstitial Lamellae

Remnants of older remodeled osteons located between active osteons in compact bone.

Circumferential Lamellae

Rings of bone matrix running along the inner and outer circumferences of compact bone to add structural support.

Perforating Canals

Channels running perpendicular to central canals (also called Volkmann canals) that carry blood vessels and nerves into bone from the periosteum.

Ossification

The process of bone formation (also known as osteogenesis) starting in the embryonic period and continuing through childhood.

Primary Bone

Immature bone (woven bone) composed of irregularly arranged collagen fibers, abundant osteocytes, and little inorganic matrix.

Secondary Bone

Mature bone (lamellar bone) featuring parallel collagen fibers organized into lamellae with high inorganic matrix content.

Intramembranous Ossification

Bone formation occurring within a model of mesenchymal embryonic tissue, forming flat bones of the skull and clavicles.

Endochondral Ossification

Bone formation occurring within a model of hyaline cartilage, forming all bones below the head except the clavicles.

Calcification

The deposition of calcium salts and other inorganic matrix components into the bone matrix during ossification.

Fontanels

Unossified mesenchymal membrane "soft spots" in newborn skulls where cranial primary ossification centers have not fully fused.

Bone Collar

A ring of compact bone built by osteoblasts around the outer diaphysis surface of a hyaline cartilage model during early endochondral ossification.

Osteoporosis

A bone disease caused by inadequate inorganic matrix, leading to reduced bone density, brittle bones, and increased fracture risk.

Achondroplasia

A genetic condition causing dwarfism due to an abnormal growth factor receptor that inhibits endochondral ossification and epiphyseal plate cell division.

Longitudinal Growth

The process by which long bones lengthen through division of chondrocytes within the epiphyseal plate.

Zone of Reserve Cartilage

The layer of the epiphyseal plate closest to the epiphysis containing resting chondrocytes that can divide if necessary.

Zone of Proliferation

The epiphyseal plate layer where chondrocytes actively undergo mitosis inside lacunae to drive bone growth in length.

Zone of Hypertrophy and Maturation

The epiphyseal plate layer where dividing chondrocytes cease dividing, enlarge, and mature.

Zone of Calcification

The epiphyseal plate region where chondrocytes die and their surrounding matrix calcifies due to distance from blood vessels.

Zone of Ossification

The epiphyseal plate region closest to the diaphysis where osteoblasts invade calcified cartilage and lay down secondary bone.

Appositional Growth

The growth of bone in width accomplished by osteoblasts depositing new circumferential lamellae beneath the periosteum.

Growth Hormone

An anterior pituitary hormone that stimulates chondrocyte mitosis at the epiphyseal plate and increases osteoblast activity.

Gigantism

A growth disorder caused by hypersecretion of growth hormone during childhood prior to closure of the epiphyseal plates.

Acromegaly

A growth disorder caused by hypersecretion of growth hormone in adulthood after epiphyseal plates have closed, leading to thickened skull, face, hand, and foot bones.

Bone Remodeling

The continuous combined processes of bone deposition by osteoblasts and bone resorption by osteoclasts throughout life.

Rickets

A condition in children resulting from vitamin D deficiency, leading to poorly mineralized bones, deformities, weakness, and fractures.

Parathyroid Hormone

A hormone released by parathyroid glands in response to low blood calcium levels that stimulates osteoclast activity and increases blood calcium levels.

Calcitonin

A hormone produced by the thyroid gland that decreases blood calcium levels by inhibiting osteoclasts.

Hematoma

A mass of clotted blood filling the fracture gap following blood vessel disruption in bone injury.

Soft Callus

Temporary repair tissue composed of dense irregular connective tissue and hyaline cartilage formed during fracture healing.

Bone Callus

A collar of primary bone laid down by periosteal osteoblasts to bridge a fracture gap during repair.

Simple Fracture

A bone fracture in which the surrounding skin and soft tissue remain intact (closed fracture).

Compound Fracture

A bone fracture involving open damage to the surrounding skin and soft tissue (open fracture).

Closed Reduction

A nonsurgical procedure to realign broken bone ends into contact.

Open Reduction

A surgical procedure to align and fixate fractured bone fragments using plates, screws, or wires.

Spiral Fracture

A fracture resulting from twisting forces applied along the bone shaft.

Compression Fracture

A fracture in which bone tissue is crushed under weight load, common in osteoporotic or elderly bone.

Comminuted Fracture

A complex fracture in which the bone shatters into multiple small fragments.

Avulsion Fracture

A fracture in which a tendon or ligament tears off a fragment of bone at its attachment site.

Greenstick Fracture

An incomplete fracture common in children where one side of the bone breaks while the opposite side bends.

Epiphyseal Plate Fracture

A fracture involving part of the epiphyseal growth plate, occurring in children and adolescents, which can interfere with bone growth.