Chapter 7: Skeletal System

Comprehensive vocabulary flashcards covering the skeletal system, including bone cell types, anatomy, growth patterns, chemical composition, and fracture repair based on the lecture notes.

Hematopoiesis

The process of blood cell formation that occurs within the red marrow cavities of bone.

Triglyceride storage

Energy stored in the form of lipids within the yellow bone marrow.

-blast

A suffix referring to an immature cell that secretes a substance, such as an osteoblast.

-cyte

A suffix referring to a mature cell that maintains a substance, such as an osteocyte.

Osteogenic Cells

Stem cells derived from mesenchyme that are the only bone cells to undergo cell division; they give rise to osteoblasts.

Osteoblasts

Bone-forming cells that develop from osteoprogenitor cells and produce the organic bone matrix called osteoid.

Osteoid

The organic form of the bone matrix produced by osteoblasts, making up approximately $45\%$ of the matrix.

Osteocytes

Mature bone cells derived from osteoblasts that reside in lacunae and act as mechanosensory cells to regulate skeletal homeostasis.

Osteoclasts

Large, multinucleated phagocytic cells derived from monocyte/macrophage lineage that break down bone matrix through resorption.

Resorption

The process by which osteoclasts break down bone matrix using lysosomal enzymes and hydrochloric acid ($HCl$).

Compact Bone (Cortical Bone)

The strongest form of bone tissue found on the outside of bones, making up the bulk of the diaphysis in long bones.

Spongy Bone

Bone tissue located inside bones, usually at the epiphyses, made of trabeculae and filled with red or yellow marrow.

Trabeculae

"Little beams" of bone tissue found in spongy bone that are oriented along lines of stress.

Osteon

The basic functional unit of compact bone.

Lacuna

Tiny spaces within the bone matrix that house osteocytes.

Canaliculus

A tiny, hair-like channel that connects lacunae to provide pathways for nutrients between osteocytes.

Lamella

A thin, concentric layer of bone matrix that provides protection and resists stress.

Central Canal (Haversian Canal)

A cylindrical channel at the center of each osteon containing blood and nerve supplies.

Perforating Canal (Volkmann’s Canal)

A transverse or diagonal canal that connects blood and nerve supplies between adjacent central canals.

Diaphysis

The shaft or long main portion of a long bone.

Epiphysis

The ends of a long bone, categorized as proximal (closest to the trunk) or distal (farthest from the trunk).

Metaphysis

The region in a long bone between the diaphysis and the epiphysis containing the epiphyseal plate or line.

Epiphyseal plate

Also known as the growth plate; a layer of hyaline cartilage where growth in bone length occurs.

Epiphyseal line

The remnant of the epiphyseal plate in adults after longitudinal growth has ceased.

Articular cartilage

A layer of hyaline cartilage covering the epiphyses to reduce friction and absorb shock in joints.

Medullary cavity

A hollow space within the diaphysis containing red bone marrow in children and yellow bone marrow in adults.

Periosteum

A double-layered connective tissue surrounding the diaphysis, containing an outer fibrous layer and an inner cellular layer with bone cells.

Endosteum

A thin membrane lining the medullary cavity and trabeculae that contains osteoprogenitor cells, osteoblasts, and osteoclasts.

Diploë

The specific term for the endosteum-covered spongy bone found inside short, irregular, and flat bones.

Red marrow

Reticular connective tissue involved in blood cell development, found in most bones of children and specific areas of the adult skeleton.

Yellow marrow

Fatty tissue that no longer produces blood, found in the medullary cavities of adult long bones.

Nutrient foramen

An opening in the bone through which nutrient arteries and veins enter and exit.

Hydroxyapatites

Crystallized mineral salts consisting of $Ca_5(OH)(PO_4)_3$ that make up $55\%$ of the bone matrix and provide hardness.

Ossification (Osteogenesis)

The general process of formation and development of bone connective tissue.

Intramembranous Ossification

The process by which bone develops from a fibrous connective tissue membrane; produces flat bones of the skull, some facial bones, the mandible, and the clavicle.

Endochondral Ossification

The process by which bone develops by replacing hyaline cartilage; used for most bones in the body.

Interstitial Growth

An increase in the length of long bones occurring at the epiphyseal plate.

Appositional Growth

An increase in the thickness or width of bone through the action of osteoblasts beneath the periosteum.

Woven bone

Immature and unorganized bone tissue formed during the initial stages of intramembranous ossification.

Alkaline phosphatase

An enzyme produced by osteoblasts that is essential for the mineralization of bone matrix.

Wolff’s Law

The principle stating that bone will grow or remodel in response to the forces or physical demands placed on it.

Hypercalcemia

A condition characterized by high levels of calcium in the blood (above $10.3\,\text{mg/dL}$).

Hypocalcemia

A condition characterized by low levels of calcium in the blood (below $8.6\,\text{mg/dL}$).

Parathyroid hormone (PTH)

A hormone released by the parathyroid glands in response to hypocalcemia to increase osteoclast activity and raise blood calcium levels.

Calcitonin

A hormone released by the thyroid gland in response to hypercalcemia to inhibit osteoclasts and speed up calcium deposition in bone.

Calcitriol

The active form of Vitamin D produced by the kidneys that increases calcium absorption in the intestines.

Stress fracture

A thin break in the bone caused by a sudden increase in physical activity.

Simple fracture

A break in the bone where the bone ends do not penetrate the skin.

Compound fracture

A break where at least one end of the bone pierces through the skin.

Fracture hematoma

A mass of clotted blood that forms at the site of a bone fracture during the first stage of repair.