Skeletal System: Osseous Tissue, Structure, Growth, and Development

Comprehensive vocabulary flashcards covering skeletal tissues, macroscopic and microscopic bone structure, ossification processes, longitudinal and appositional growth, and hormonal regulation.

Functions of the Skeletal System

Support, protection, attachment for muscle, energy and mineral reserves, and hemopoiesis.

Osteoid

The organic component of bone ground substance composed of protein fibers (collagen) that provides tensile strength and mineralizes later.

Hydroxyapatite

The inorganic component of osseous tissue made of calcium, phosphorus, and oxygen that provides compressive strength.

Osteoblasts

Bone cells that build bone by secreting osteoid, which mineralizes later.

Osteocytes

Mature osteoblasts trapped in matrix that maintain the matrix, repair damage, and sense mechanical stress.

Osteoclasts

Cells that break down bone matrix during bone remodeling.

Rickets & Osteomalacia

Disorders of the skeletal matrix marked by inadequate calcification of bone ECM (usually due to vitamin D deficiency), causing bones to become soft and easily deformed.

Osteogenesis Imperfecta

A congenital defect of collagen that results in bones that are brittle and easily fractured.

Cortical Bone

Dense outer shell of bone organized into osteons with concentric lamellae of ECM and central canals for neurovasculature, oriented parallel to compressive stress.

Osteon

The functional unit of cortical bone featuring alternating collagen fiber orientations between concentric lamellae to provide multidirectional stability and resistance to torsion.

Cancellous Bone

Loosely organized interior bone arranged in a strong but lightweight lattice without osteons; helps absorb and transmit forces and is sometimes filled with red bone marrow.

Periosteum

An external layer of dense irregular connective tissue that is highly innervated, functions in growth and repair, and produces osteoblasts.

Endosteum

An internal layer of dense irregular connective tissue that is highly innervated, functions in growth and repair, and produces osteoblasts.

Long Bones

Bones that are longer than they are wide, functioning primarily in support and movement.

Epiphyses

Enlarged ends of long bones containing cancellous bone internally (with red bone marrow) and covered by articular cartilage externally.

Diaphysis

The shaft of a long bone composed of cortical bone surrounding a medullary cavity filled with yellow bone marrow.

Flat Bones

Thin, often curved bones composed of cancellous bone surrounded by cortical bone without a medullary cavity; function in protection and shock absorption.

Short Bones

Cube-like shaped bones providing stability and movement.

Irregular Bones

Bones with complex shapes that provide support and protection.

Sesamoid Bones

Bones that form within tendons to aid movement.

Ossification

Bone formation, which begins around embryonic week 8.

Intramembranous Ossification

Bone formation beginning from a primary ossification center in fetal connective tissue to form trabeculae and exterior cortical bone; produces clavicles and some bones of the skull.

Endochondral Ossification

Bone formation that begins with a cartilaginous model covered by perichondrium, progressing to form a bony collar, calcified matrix, and marrow cavity.

Calcification

The deposition of mineral materials into the extracellular matrix other than osteoid.

Primary Bone

Immature bone quickly laid down with irregularly arranged collagen fibers and little organic matrix; eventually reabsorbed and replaced by secondary bone.

Secondary Bone

Mature bone produced slowly, characterized by fully formed osteons, parallel collagen orientation, and a higher percentage of inorganic material for greater strength.

Red Bone Marrow

Hematopoietic tissue found in every bone in children and restricted to the head and trunk in adults.

Yellow Bone Marrow

Fat storage tissue located in the medullary cavities of adult limbs.

Zone of Proliferation

The region of the epiphyseal plate where chondrocytes undergo rapid cell division.

Zone of Hypertrophy

The region of the epiphyseal plate where chondrocytes increase in size.

Zone of Calcification

The region of the epiphyseal plate containing dead chondrocytes and calcified extracellular matrix.

Zone of Ossification

The region of the epiphyseal plate where osteoblasts ossify calcified cartilage to form bone.

Epiphyseal Plate Closure

The fusion and complete ossification of the epiphyseal plate near the end of adolescence, marking the cessation of longitudinal growth.

Achondroplasia

A condition resulting from a spontaneous mutation that causes failure of cartilage growth in the epiphyseal plate, stopping long bone growth in childhood and causing disproportionately short limbs.

Apositional Growth

Bone widening occurring at the periosteal surface where periosteal osteoblasts secrete new cortical bone superficially while osteoclasts erode the medullary cavity.

Growth Hormone

Hormone that increases chondrocyte cell division at the epiphyseal plate, increases osteogenic cell activity, and stimulates osteoblasts in the periosteum.

Testosterone

Hormone that increases apositional growth and chondrocyte cell division.

Estrogen

Hormone that inhibits osteoclast activity and accelerates epiphyseal closure.