Chapter 6 - Bone Tissue

Vocabulary flashcards covering skeletal tissues, bone cells and matrix, ossification, bone growth and remodeling, calcium regulation, fracture types, and clinical bone disorders.

Compact Bone

Dense, cortical bone tissue that looks smooth and solid in appearance, forming the outer shell of bones.

Spongy Bone

Cancellous or trabecular bone tissue located deep to compact bone, characterized by a porous structure made of a mesh of bony spines called trabeculae.

Trabeculae

A mesh of bony spines that forms the structural framework of spongy bone.

Hyaline Cartilage

Semirigid, avascular connective tissue with chondrocytes in lacunae and a smooth, glassy-appearing matrix that provides flexible support and smooth articulating surfaces.

Fibrocartilage

Semirigid connective tissue featuring thick, visible collagen fibers and chondrocytes in lacunae, providing strong resistance to compression and tension.

Ligaments

Connective tissue structures composed of dense regular connective tissue that connect bone to bone.

Tendons

Connective tissue structures composed of dense regular connective tissue that connect muscle to bone.

Hematopoiesis

The production of blood cells, which takes place in red bone marrow.

Red Bone Marrow

Soft connective tissue containing reticular connective tissue, developing blood cells, and adipocytes that serves as the primary site of hematopoiesis.

Yellow Bone Marrow

Soft connective tissue containing proportionally more adipose tissue that replaces red marrow with age and stores lipids as an energy reserve.

Osteoprogenitor Cell

A stem cell derived from mesenchyme that differentiates into an osteoblast.

Osteoblast

A matrix-synthesizing bone cell responsible for bone growth that secretes osteoid.

Osteocyte

A mature bone cell residing in a lacuna that monitors and maintains the mineralized bone matrix.

Osteoclast

A large, multinucleated bone-resorbing cell originating from white blood cell lineage that features a ruffled border.

Osteon

The functional unit of compact bone tissue consisting of concentric lamellae surrounding a central canal.

Central Canal

A longitudinal channel in the center of an osteon containing blood vessels and nerves.

Canaliculi

Tiny channels connecting adjacent lacunae and central canals, allowing osteocytes to communicate and share nutrients.

Periosteum

A sheath of dense connective tissue covering the outer surface of bone, consisting of an outer fibrous layer and an inner cellular layer.

Endosteum

An incomplete cellular layer lining the internal bony canals and covering the trabeculae of spongy bone.

Osteoid

The organic component of bone matrix secreted by osteoblasts, primarily composed of collagen fibers, providing tensile strength and resistance to stretching and twisting.

Hydroxyapatite

Inorganic mineral crystals in bone matrix formed primarily from calcium and phosphate, providing hardness and resistance to compression.

Intramembranous Ossification

Bone development process where ossification centers develop directly within a fibrous connective tissue membrane.

Endochondral Ossification

Bone formation process in which a hyaline cartilage model is calcified and systematically replaced by bone tissue.

Proliferation Zone

The region of the epiphyseal plate where cartilage cells undergo mitosis.

Hypertrophic Zone

The region of the epiphyseal plate where older cartilage cells enlarge.

Calcification Zone

The region of the epiphyseal plate where the cartilage matrix calcifies, cartilage cells die, and the matrix begins deteriorating.

Ossification Zone

The region of the epiphyseal plate where new bone tissue is actively being formed by osteoblasts on calcified cartilage spicules.

Appositional Growth

Increase in bone diameter or width achieved when osteoblasts beneath the periosteum deposit new bone on the external surface while osteoclasts resorb bone internally.

Interstitial Growth

Growth in bone length occurring through cartilage division and replacement within the epiphyseal plate.

Bone Remodeling

The ongoing process of bone deposition by osteoblasts and bone resorption by osteoclasts to maintain bone strength, adapt to mechanical loading, and regulate mineral homeostasis.

Parathyroid Hormone

A hormone released by the parathyroid glands when blood $Ca^{2+}$ is low that promotes processes raising blood $Ca^{2+}$ by increasing osteoclast activity and decreasing urinary calcium excretion.

Calcitriol

The active hormone form of vitamin $D_3$ produced via conversions in the liver and kidney that acts to increase intestinal absorption of calcium and phosphate.

Calcitonin

A hormone that can lower blood calcium levels by reducing osteoclast activity.

Osteopenia

An age-related condition marked by reduced bone mass.

Osteoporosis

A severe form of bone loss that substantially increases bone fragility and fracture risk.

Closed Fracture

A bone fracture in which the overlying skin remains intact.

Open Fracture

A compound fracture where the broken bone penetrates through a break in the skin.

Greenstick Fracture

An incomplete break where one side of the bone shaft breaks while the other side bends, common in children.

Comminuted Fracture

A fracture where bone fragments into three or more pieces, common in older adults with brittle bones.

Compression Fracture

A fracture in which bone is crushed, common in porous or osteoporotic vertebrae subjected to trauma.

Spiral Fracture

A ragged break occurring when excessive twisting forces are applied to a bone, common in sports injuries.

Pathologic Fracture

A bone fracture caused by disease processes that weaken the bone structure.

Fracture Hematoma

A mass of clotted blood that forms at the fracture site during stage 1 of bone repair.

Osteomalacia

A metabolic bone disorder known as 'disease of soft bones' caused by impaired osteoid mineralization, leading to soft and weak bones.

Osteogenesis Imperfecta

An inherited connective tissue disorder known as 'brittle bone disease' caused by mutations affecting type I collagen, resulting in weak organic matrix and frequent fractures.