A&P OpenStax Chapter 6: Bone Tissue and the Skeletal System

Vocabulary flashcards generated from lecture notes covering functions, classifications, microscopic and gross structures, formation processes, fractures, hormone interactions, and disorders of bone tissue and the skeletal system.

Axial skeleton

The division of the adult skeleton consisting of 80 bones, including the skull, hyoid, sternum, rib cage, vertebral column, sacrum, and coccyx.

Appendicular skeleton

The division of the adult skeleton consisting of 126 bones, including the limbs and the pectoral and pelvic girdles.

Osteon

The basic structural and functional unit of compact bone consisting of bone cells organized around a central canal and separated by concentric lamellae.

Central canal

Also known as the Haversian canal, it runs parallel to the axis of bone in the middle of each osteon and contains an artery, vein, lymph vessel, and nerve.

Perforating canals

Passageways that extend perpendicular to the axis of the bone and connect the central canals of adjacent osteons.

Lamellae

Nested, concentric rings of matrix surrounding the central canal of an osteon.

Lacunae

Open spaces within the bone matrix in which mature bone cells (osteocytes) are trapped.

Canaliculi

Narrow crevices that penetrate the lamellae and connect the lacunae to the central canal, housing processes of osteocytes.

Osteocytes

Mature bone cells that maintain the protein and mineral content of the surrounding matrix and participate in the repair of damaged bones.

Osteoblasts

Immature bone cells located on the surface of bone that produce new bone matrix in a process called osteogenesis or ossification.

Osteoid

The organic bone matrix produced and released by osteoblasts before calcium salts are deposited.

Osteoprogenitor cells

Mesenchymal stem cells located within the periosteum and endosteum that divide to produce daughter cells that differentiate into osteoblasts.

Osteoclasts

Giant bone-digesting cells with 50 or more nuclei that remove and recycle bone matrix by secreting acids and proteolytic enzymes.

Endochondral Ossification

The formation of long bones using a hyaline cartilage model, beginning approximately 6 weeks after fertilization.

Periosteal bud

A collection of migrating fibroblasts, lymph vessels, nerve fibers, and red marrow elements that invades the central region of hyaline cartilage along with penetrating blood vessels.

Intramembranous Ossification

The formation of bone without a cartilage model, typical in flat bones, mandible, clavicles, and patella, beginning approximately 8 weeks after fertilization.

Epiphyseal line

The bony structure formed when the hyaline cartilage at the epiphyseal plate is completely replaced by bone, signaling the end of height growth.

Simple (closed) fracture

A bone fracture where the bone breaks cleanly without penetrating the skin.

Compound (open) fracture

A bone fracture where the broken ends of the bone protrude through the tissue and skin.

Transverse fracture

A bone break occurring perpendicular to the long axis of a bone.

Linear fracture

A bone break occurring parallel to the long axis of the bone.

Calcitriol

The active form of vitamin D produced by the kidneys that stimulates the absorption of calcium and phosphate from the digestive tract.

Parathyroid hormone (PTH)

A hormone secreted by the parathyroid gland when blood calcium levels are low to increase blood calcium levels via bone, intestinal, and kidney responses.

Calcitonin

A hormone secreted by the C cells of the thyroid gland when blood calcium levels are too high, acting to lower blood calcium levels.

Dwarfism

A condition resulting from inadequate production of growth hormone, leading to reduced epiphyseal cartilage activity and abnormally short bones.

Achondroplasia

A disorder resulting from abnormal hyaline cartilage development, causing short, stocky limbs with a normal-sized torso and head.

Marfan syndrome

A condition causing excessive cartilage formation at the epiphyseal plates, resulting in very tall individuals with long, slender limbs and potential cardiovascular defects.

Gigantism

A condition resulting from an overproduction of growth hormone before puberty, commonly caused by a pituitary tumor.

Acromegaly

A condition caused by excess growth hormone production after epiphyseal plates close, resulting in thicker bones, especially in the face, hands, and jaw.

Fibrodysplasia ossificans progressiva (FOP)

A rare gene mutation causing the deposition of bone around skeletal muscles and other soft tissues of the body.

Paget's Disease

A disorder characterized by overactive osteoclasts causing pores and weakening in long bones, compensated by osteoblasts laying down weak, brittle bone prone to fractures.