Bones: Structure, Function, and Bone Markings (Vocabulary Flashcards)

Vocabulary flashcards covering bone structure, tissue types, cell types, bone growth/remodeling, marrow, long/flat/irregular bones, and bone markings.

Skeletal system

The organ system comprising bones, joints, cartilages, and ligaments that provides support, protection, movement, attachment sites for muscles, hematopoiesis, and mineral storage.

Bones

Rigid organs that form part of the skeletal system; composed of osseous tissue along with nerves, cartilage, ligaments, and blood vessels.

Compact bone

Dense outer layer of bone (also called cortical bone); smooth, solid, and strong for weight-bearing.

Spongy bone

Cancellous or trabecular bone with a honeycomb network of trabeculae, often containing red or yellow marrow.

Osteon (Haversian system)

Structural unit of compact bone consisting of a central Haversian canal surrounded by concentric lamellae and osteocytes in lacunae.

Central (Haversian) canal

Vertical canal in an osteon that houses blood vessels and nerves.

Lamellae

Concentric rings of bone matrix within an osteon.

Canaliculi

Small channels through which osteocytes communicate and exchange nutrients and wastes.

Osteoblast

Bone-forming cell responsible for bone synthesis and mineralization.

Osteoclast

Bone-resorbing cell that breaks down bone tissue during remodeling.

Osteocyte

Mature bone cell embedded in a lacuna within the mineralized matrix; maintains bone tissue.

Osteogenic cell

Stem cell that differentiates into osteoblasts and contributes to bone growth and repair.

Endosteum

Membrane lining the inner surfaces of bone, including the medullary cavity and trabeculae; contains osteoblasts and osteoclasts.

Periosteum

Outer fibrous membrane covering bone; contains an inner osteogenic layer with osteoblasts and osteoclasts; rich in blood vessels and nerves; attaches to bone via Sharpey’s fibers.

Sharpey’s fibers

Collagen fibers that attach periosteum to the underlying bone.

Medullary (marrow) cavity

Central cavity within the diaphysis; in adults contains yellow marrow and is lined by endosteum.

Red bone marrow

Hematopoietic tissue found in certain bones of infants and in some bones of adults, responsible for blood cell formation.

Yellow bone marrow

Fatty marrow that replaces red marrow in the diaphysis of many adult bones.

Diaphysis

The tubular shaft forming the long axis of a long bone; surrounds the medullary cavity.

Epiphysis

The expanded ends of a long bone; exterior compact bone with interior spongy bone.

Metaphysis

Region between the diaphysis and each epiphysis; contains the growth plate in developing bones.

Epiphyseal line/plate

Line in adults that marks where the epiphyseal plate used to be; in children, the plate is the hyaline cartilage responsible for bone growth.

Articular cartilage

Hyaline cartilage covering the ends of bones in joints to reduce friction and absorb shock.

Medullary cavity

See central cavity within the diaphysis housing marrow; lined by endosteum.

Diploë

In flat bones, the sandwich of two thin plates of compact bone with spongy bone (diploë) in between.

Trabeculae

Thin beam-like elements of spongy bone forming the lattice of cancellous bone.

Red marrow distribution

Hemopoietic tissue found in certain bones (e.g., femur, ribs, pelvis, vertebrae in adults); active in blood cell formation.

Bone matrix composition

Inorganic component mainly calcium phosphate crystals (65%); organic component including osteoid and collagen (35%).

Osteoid

Non-mineralized organic part of the bone matrix produced by osteoblasts, primarily collagen.

Bone markings

External features of bones such as projections (for muscle/ligament attachment), depressions, and openings that form joints or conduits for vessels and nerves.

Projection (bone marking)

Raised area on a bone for tendon/ligament attachment (e.g., head, trochanter, tuberosity, condyle, crest, line, tubercle, epicondyle, spine).

Depression (bone marking)

Indentations on bone surfaces, such as notches, fossae, sinuses, and grooves.

Foramen

Hole through a bone that allows passage of nerves or vessels.

Meatus

Canal-like passageway in a bone.

Fossa

Shallow, basin-like depression on a bone surface.

Groove

Furrow or elongated channel on a bone surface.

Notch

Indention at the edge of a bone.

Head

Elongated end of a bone that articulates with another bone, typically on a narrow neck.

Condyle

Rounded articular projection that forms a joint with another bone.

Sesamoid bone

Small, round bone embedded within a tendon; example: patella; functions to alter tendon mechanics and protect joints.

Long bones

Bones longer than they are wide, with a diaphysis and two epiphyses; mostly compact bone with marrow in the medullary cavity.

Flat bones

Bones with two parallel compact bone layers separated by a middle spongy (diploë) layer; no diaphysis or epiphysis; e.g., skull bones, sternum, ribs.

Short bones

Bones that are as wide as they are long, with thin compact bone surrounding spongy interior; e.g., carpals and tarsals.

Irregular bones

Bones that do not fit standard shapes, such as vertebrae and many facial bones.

Structure of a typical long bone

Diaphysis (shaft) with compact bone surrounding a medullary cavity; epiphyses at each end with spongy bone; articular cartilage on joint surfaces; periosteum on exterior; endosteum lining internal surfaces.