Fundamentals of Anatomy & Physiology: Chapter 6 - Bones and Bone Structure

Comprehensive vocabulary flashcards covering bone shapes, anatomical markings, microscopic structure, cell types, ossification pathways, calcium homeostasis, fracture classifications, repair, and aging processes from Chapter 6.

Sutural bones (Wormian bones)

Small, flat, irregularly shaped bones found between the flat bones of the skull, featuring borders like jigsaw puzzle pieces and ranging in size from a grain of sand to a quarter.

Irregular bones

Bones with complex shapes and short, flat, notched, or ridged surfaces, exemplified by the spinal vertebrae, pelvic bones, and several bones of the skull.

Short bones

Boxlike or boxy bones of roughly equal dimensions, exemplified by the carpal bones of the wrists and tarsal bones of the ankles.

Flat bones

Thin bones with parallel surfaces that provide protection for underlying soft tissues and offer an extensive surface area for muscle attachment, such as the roof of the skull, sternum, ribs, and scapulae.

Long bones

Relatively long and slender bones found in the limbs, palms, soles, fingers, and toes, exemplified by the humerus and the femur.

Sesamoid bones

Small, round, and flat bones that develop within tendons near the joints of the knees, hands, and feet, such as the patellae (kneecaps).

Process (bone marking)

Any projection or bump on a bone surface.

Ramus

A part of a bone that forms an angle with the rest of the structure.

Trochanter

A large, rough projection on a bone, such as those found on the proximal femur.

Crest (bone marking)

A prominent ridge on a bone where muscles, tendons, or ligaments attach.

Spine (bone marking)

A pointed process on a bone.

Line (bone marking)

A low, narrow ridge on a bone that serves as an attachment site.

Tubercle

A small, rounded projection on a bone surface.

Tuberosity

A rough, elevated projection on a bone that serves as an attachment site for muscles or ligaments.

Head (bone marking)

The expanded articular end of an epiphysis, often separated from the shaft by a narrower neck.

Neck (bone marking)

A narrow connection between the epiphysis and the diaphysis of a long bone.

Facet

A small, flat articular surface where two bones articulate.

Condyle

A smooth, rounded articular process that participates in forming a joint.

Trochlea

A smooth, grooved articular process shaped like a pulley.

Sinus (bone marking)

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

Foramen

A rounded passageway through a bone for the transmission of blood vessels and/or nerves.

Fissure (bone marking)

A deep furrow, cleft, or slit in a bone.

Meatus

A passage or channel through a bone, especially the opening of a canal.

Canal (bone marking)

A duct or channel passing through bone tissue.

Sulcus (bone marking)

A narrow groove on the surface of a bone.

Fossa

A shallow depression on a bone surface.

Diaphysis

The extended tubular shaft of a long bone, consisting of a wall of compact bone surrounding a hollow medullary cavity.

Epiphysis

The expanded, articulating end of a long bone, composed largely of spongy bone (trabecular bone).

Metaphysis

The narrow transitional zone connecting the diaphysis and the epiphysis in a long bone.

Medullary cavity

The central internal chamber within the diaphysis of a long bone that contains bone marrow.

Diploë

The central core of spongy bone situated between two protective layers of compact bone (cortex) within the cranium.

Hydroxyapatite

Hard, brittle mineral crystals formed from calcium phosphate, with the formula $\text{Ca}_{10}(\text{PO}_4)_6(\text{OH})_2$, that constitute approximately two-thirds of the bone matrix and resist compression.

Lacunae

Small pockets or chambers within the calcified matrix of bone that each house an osteocyte.

Canaliculi

Narrow passageways that penetrate the bone matrix, linking lacunae to one another and to blood vessels for the exchange of nutrients, wastes, and gases.

Osteogenic cells (osteoprogenitor cells)

Mesenchymal stem cells present in the cellular layers of the periosteum and endosteum that divide to produce daughter cells that differentiate into osteoblasts.

Osteoblasts

Immature bone cells that synthesize and secrete the organic components of the bone matrix during osteogenesis and promote the deposition of calcium salts.

Osteoid

The unmineralized organic matrix composed primarily of collagen fibers secreted by osteoblasts prior to calcification.

Osteocytes

Mature bone cells residing inside lacunae that maintain the protein and mineral content of the surrounding matrix and assist in bone repair; they do not divide.

Osteoclasts

Large, multinucleate cells that secrete acids and protein-digesting enzymes to dissolve bone matrix and release stored minerals in a process called osteolysis.

Osteolysis

The enzymatic resorption and breakdown of bone matrix carried out by osteoclasts.

Osteon

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

Central canal (Haversian canal)

A longitudinal channel located at the core of an osteon containing blood vessels and nerves that run parallel to the bone surface.

Perforating canals (Volkmann's canals)

Passageways extending perpendicularly to the bone surface that deliver blood vessels from the periosteum into osteons and the medullary cavity.

Concentric lamellae

Circular, concentric rings of calcified matrix that surround the central canal of an osteon.

Interstitial lamellae

Layers of bone matrix that fill the spaces between existing osteons, consisting of remnants of older remodeled osteons.

Circumferential lamellae

Broad sheets of bone matrix located on the inner and outer surfaces of the shaft produced during appositional growth.

Trabeculae

An interconnected network of struts and plates that forms the lattice-like architecture of spongy bone.

Red bone marrow

Specialized vascular tissue situated within the open spaces between spongy bone trabeculae responsible for blood cell production (hematopoiesis).

Yellow bone marrow

Adipose tissue found within the medullary cavity and certain spongy bone regions that functions primarily as an energy reserve storing lipids.

Periosteum

A membrane enveloping the outer surface of a bone (except at joints), comprising an outer fibrous layer and an inner cellular layer that functions in isolation, neurovascular transport, and growth/repair.

Perforating fibers (Sharpey's fibers)

Collagen fibers from the periosteum, tendons, and ligaments that penetrate directly into the bone matrix to firmly anchor them to the bone.

Endosteum

An incomplete cellular layer containing osteogenic cells, osteoblasts, and osteoclasts that lines the medullary cavity, spongy bone trabeculae, and central canals.

Calcification

The deposition of calcium salts into a tissue, which occurs during ossification as well as in other tissues under certain conditions.

Endochondral ossification

The biological process of bone formation in which an initial hyaline cartilage model is progressively replaced by osseous tissue.

Primary ossification center

The initial central region of a cartilage shaft where blood vessels invade, osteoblasts differentiate, and spongy bone formation begins during endochondral ossification.

Secondary ossification center

Sites of bone formation that develop in the epiphyses of long bones as capillaries and osteoblasts migrate into them.

Epiphyseal cartilage (epiphyseal plate)

A narrow region of hyaline cartilage located in the metaphysis that separates the epiphysis from the diaphysis and permits interstitial growth in bone length.

Epiphyseal closure

The completion of longitudinal bone growth occurring at puberty, when cartilage production slows and osteoblast activity accelerates until the epiphyseal plate disappears.

Epiphyseal line

A distinct, visible line of osseous tissue marking the former location of the epiphyseal cartilage after longitudinal growth has stopped.

Appositional growth

The growth process that increases bone diameter and wall thickness as osteoblasts of the periosteum deposit new circumferential lamellae on the outer bone surface.

Intramembranous ossification (dermal ossification)

The formation of bone that begins directly within mesenchymal or fibrous connective tissue in the deeper layers of the dermis, producing dermal bones such as the cranial roof, mandible, and clavicles.

Spicules

Small, needle-like struts of developing bone that radiate outward from the ossification center during intramembranous ossification.

Bone remodeling

The continuous, lifelong recycling and renewal of bone matrix involving coordinated balance between osteoclastic resorption and osteoblastic deposition.

Calcitriol

An active hormone synthesized by the kidneys from vitamin D that is essential for normal calcium and phosphate ion absorption across the digestive tract.

Pituitary growth failure

A condition resulting from inadequate production of growth hormone during development, leading to abnormally short bones and reduced stature.

Gigantism

A disorder resulting from excessive secretion of growth hormone prior to puberty and epiphyseal closure, causing extreme bone lengthening.

Acromegaly

A condition caused by overproduction of growth hormone after epiphyseal closure, resulting in abnormal bone thickening and altered facial structures.

Marfan syndrome

A genetic condition characterized by excessive cartilage proliferation at epiphyseal plates, resulting in tall stature and unusually long, slender limbs.

Parathyroid hormone (PTH)

A hormone secreted by the parathyroid glands in response to blood calcium levels below $8.5\,\text{mg/dL}$ that raises calcium levels by stimulating osteoclasts, enhancing renal reabsorption, and increasing calcitriol synthesis.

Calcitonin

A hormone secreted by thyroid C cells in response to blood calcium levels above $11\,\text{mg/dL}$ that lowers calcium by inhibiting osteoclast activity and stimulating renal calcium excretion.

Osteomalacia

A condition in which bones become weak and flexible due to inadequate mineralization of the bone matrix.

Rickets

A pediatric form of osteomalacia caused by nutritional deficiency of vitamin D, leading to poorly mineralized, bowed long bones.

Open (compound) fracture

A bone fracture in which the broken bone fragments pierce through the surrounding soft tissues and skin.

Closed (simple) fracture

A bone fracture that remains completely internal without breaking through the skin.

Transverse fracture

A break that crosses a bone shaft perpendicular to its long axis.

Displaced fracture

A fracture that produces new and abnormal anatomical alignment between bone fragments.

Nondisplaced fracture

A fracture in which the broken bone pieces retain their normal anatomical alignment.

Compression fracture

A fracture occurring when vertebrae are subjected to extreme vertical stresses, often associated with osteoporosis.

Spiral fracture

A bone fracture produced by twisting stresses that spread along the longitudinal axis of the bone shaft.

Epiphyseal fracture

A break that occurs along the metaphysis where the cartilage matrix is undergoing calcification and chondrocytes are dying, which can halt further longitudinal growth if untreated.

Comminuted fracture

A fracture that shatters the affected bone region into a multitude of small bony fragments.

Greenstick fracture

An incomplete break typically seen in children where only one side of the bone shaft fractures while the opposite side bends.

Colles fracture

A break occurring in the distal portion of the radius, commonly caused by extending an arm to cushion a fall.

Pott's fracture (bimalleolar fracture)

An ankle fracture that breaks both the medial malleolus of the distal tibia and the lateral malleolus of the distal fibula.

Fracture hematoma

A large blood clot that forms immediately following a bone fracture to seal off damaged vessels and create a fibrous framework.

External callus

A collar composed of cartilage and bone formed by dividing periosteal cells that encircles and stabilizes the outer perimeter of a fracture.

Internal callus

A bridging network of spongy bone formed by dividing endosteal cells that unites the inner edges of broken bone in the medullary cavity.

Osteopenia

Inadequate ossification and non-pathologic loss of bone mass that typically begins between ages $30$ and $40$, with women losing $8\%$ and men losing $3\%$ of bone mass per decade.

Osteoporosis

A severe reduction in bone mass sufficient to compromise normal bone function and make bones brittle, affecting $29\%$ of women and $18\%$ of men over age $45$.