Chapter 6: Osseous Tissue and Bone Structure

Comprehensive vocabulary flashcards covering skeletal divisions, bone shapes, surface markings, microscopic anatomy, growth mechanisms, calcium homeostasis, and fracture types from Chapter 6.

Axial Skeleton

The skeletal division consisting of $80$ bones, including the skull, thorax, and vertebral column, which form the longitudinal axis of the body.

Appendicular Skeleton

The skeletal division consisting of $126$ bones, comprising the limbs and the pectoral and pelvic girdles that attach them to the axial skeleton.

Flat Bones

Bones characterized by thin, parallel surfaces, exemplified by the parietal bones of the skull.

Sutural Bones

Small, flat, irregularly shaped bones found between the flat bones of the skull along suture lines.

Long Bones

Relatively long and slender bones featuring a shaft and two ends, exemplified by the humerus and femur.

Irregular Bones

Bones with complex shapes and short, flat, notched, or ridged surfaces, exemplified by vertebrae.

Sesamoid Bones

Small, flat bones shaped somewhat like a sesame seed that develop inside tendons, exemplified by the patella.

Short Bones

Boxlike bones with approximately equal length and width dimensions, exemplified by the carpal bones of the wrist.

Diaphysis

The elongated, tubular shaft of a long bone whose walls are composed of a thick layer of compact bone surrounding the central medullary cavity.

Epiphysis

The expanded area at each end of a long bone, consisting largely of spongy bone covered by a thin outer layer of compact bone.

Metaphysis

The narrow zone of a long bone that connects the epiphysis to the diaphysis.

Articular Cartilage

Avascular cartilage covering epiphyseal surfaces that form joints; it relies on diffusion from synovial fluid for nutrient delivery and waste elimination.

Medullary Cavity

The central space within the diaphysis of a long bone that houses red bone marrow and yellow bone marrow.

Red Bone Marrow

A type of marrow situated within the medullary cavity and between spongy bone trabeculae that is actively involved in blood cell production.

Yellow Bone Marrow

Marrow composed predominantly of adipose tissue that serves as an important energy reserve in bones.

Nutrient Foramen

A tunnel penetrating the diaphysis that allows the nutrient artery and nutrient vein to enter the marrow cavity and vascularize compact bone osteons.

Process

Any prominent projection or bump on a bone surface.

Tubercle

A small, rounded elevation or projection on a bone.

Tuberosity

A rough projection on a bone surface that occupies a broad area.

Trochlea

A smooth, grooved articular process shaped like a pulley.

Condyle

A smooth, rounded articular process located at a joint.

Trochanter

A large, rough projection found exclusively on the femur.

Facet

A small, flat articular surface where adjacent bones articulate.

Crest

A prominent ridge on a bone surface.

Fossa

A shallow depression or recess on the surface of a bone.

Sulcus

A deep, narrow groove on a bone surface.

Foramen

A small, rounded passageway through a bone for the transmission of blood vessels or nerves.

Canal (Meatus)

A large passageway or duct extending through the substance of a bone.

Sinus

A chamber or cavity within a bone, normally filled with air.

Osteocytes

Mature bone cells residing in lacunae that cannot divide; they maintain the protein and mineral content of the surrounding matrix.

Osteoblasts

Cells that produce new bone matrix through osteogenesis (ossification) by secreting organic osteoid and aiding in calcium salt deposition.

Osteogenic Cells

Mesenchymal stem cells located in the periosteum, endosteum, and vascular canals that divide to produce daughter cells that differentiate into osteoblasts.

Osteoclasts

Giant multinucleated cells with $50$ or more nuclei derived from macrophage stem lines that dissolve and remodel the bone matrix.

Osteolysis

The enzymatic and acidic breakdown of bone matrix by osteoclasts to release stored mineral ions into body fluids.

Osteon

The basic functional unit of mature compact bone, consisting of concentric lamellae arranged around a central canal.

Central Canal

A longitudinal channel running parallel to the bone surface at the center of an osteon that contains blood vessels.

Perforating Canals

Passageways extending perpendicular to the bone surface that carry blood vessels from the periosteum into central canals and the medullary cavity.

Canaliculi

Narrow, branching micro-canals through the calcified matrix that connect lacunae with each other and with the central canal.

Trabeculae

The branching network of bony struts and plates formed by lamellae that constitute spongy bone.

Appositional Growth

The process by which bones increase in diameter through the successive addition of circumferential lamellae beneath the periosteum.

Endochondral Ossification

The developmental process wherein a preexisting hyaline cartilage model is progressively replaced by bone tissue.

Epiphyseal Closure

The developmental event wherein osteoblast activity outpaces chondrocyte proliferation, eliminating the epiphyseal cartilage and leaving an epiphyseal line.

Intramembranous Ossification

The formation of bone directly from mesenchymal stem cells within fibrous or embryonic connective tissue without a prior cartilaginous model.

Pituitary Growth Failure

A condition caused by inadequate secretion of growth hormone, resulting in reduced epiphyseal cartilage activity and abnormally short bones.

Achondroplasia

A disorder in which the epiphyseal cartilage of long bones grows abnormally slowly and closes early, causing short, stocky limbs with a normal-sized trunk.

Marfan's Syndrome

An inherited condition characterized by excessive cartilage formation at epiphyseal plates, producing extremely tall individuals with long, slender limbs and cardiovascular complications.

Gigantism

An endocrine disorder caused by hypersecretion of growth hormone before puberty, often resulting from a pituitary tumor, leading to heights over $2.7\,\text{m}$.

Acromegaly

A condition caused by growth hormone overproduction occurring after epiphyseal plate closure, causing bones to thicken in the face, jaw, and hands.

Fibrodysplasia Ossificans Progressiva (FOP)

A rare genetic mutation that causes abnormal bone deposition within skeletal muscles and other soft tissues.

Congenital Talipes Equinovarus

A developmental abnormality (clubfoot) where abnormal muscle development twists growing feet medially and inverts them.

Parathyroid Hormone (PTH)

A hormone secreted by the parathyroid glands when blood calcium drops below $8.5\,\text{mg/dL}$; it stimulates osteoclasts, increases calcitriol synthesis, and enhances kidney calcium reabsorption.

Calcitriol

A hormone produced in the kidneys that increases the rate of calcium and phosphate absorption across the intestinal epithelium.

Calcitonin

A hormone secreted by thyroid C cells when blood calcium exceeds $11\,\text{mg/dL}$; it inhibits osteoclast activity and accelerates renal calcium excretion.

Fracture Hematoma

A large blood clot that forms within hours of a bone break to seal off damaged vessels at the fracture site.

Internal Callus

A healing network of spongy bone that forms within the marrow cavity to unite the inner margins of a fractured bone.

External Callus

A temporary stabilizing collar composed of cartilage and bone that encircles and bridges the outer edges of a bone break.

Transverse Fracture

A bone fracture that breaks across the long axis of a bone shaft.

Spiral Fracture

A bone fracture produced by twisting stresses that spreads along the longitudinal length of the shaft.

Displaced Fracture

A fracture in which the broken bone ends are forced out of alignment, producing abnormal anatomical arrangements.

Greenstick Fracture

A fracture typical of children in which one side of the shaft breaks while the opposing side bends due to incomplete ossification.

Comminuted Fracture

A fracture in which the affected bone shatters into a multitude of small fragments.

Epiphyseal Fracture

A break that occurs along the zone of calcifying cartilage between the epiphysis and diaphysis, which may halt future growth if not properly monitored.

Pott's Fracture

A bimalleolar fracture at the ankle joint that damages both the medial malleolus of the tibia and the lateral malleolus of the fibula.

Colles Fracture

A common fracture of the distal radius of the forearm, often sustained when reaching out to break a fall.