Bone Tissue - BIOL 2401 Lecture 7

Flashcards covering the anatomy, physiology, and pathology of bone tissue, including functions of the skeletal system, bone shapes, cellular components, tissue types, development, remodeling, calcium homeostasis, fractures, and osteoporosis.

Skeletal System

Composed of bones, cartilages, and ligaments joined to form a framework for the body.

Osteology

The study of bone.

Cartilage

The forerunner of most bones and covers many joint surfaces; holds bones together at joints.

Ligaments

Connect bone to bone at joints.

Tendons

Attach muscle to bone.

Bone (osseous tissue)

Connective tissue with the matrix hardened by calcium phosphate and other minerals.

Mineralization (Calcification)

The hardening process of bone.

Flat Bones

Thin, curved plates that protect soft organs (e.g., parietal bones of skull, sternum, ribs).

Long Bones

Longer than wide; act as rigid levers for movement (e.g., humerus, femur, phalanges).

Short Bones

Approximately equal in length and width (e.g., bones of wrist and ankle).

Irregular Bones

Bones with elaborate shapes (e.g., vertebrae and some skull bones).

Articular Cartilage

A layer of hyaline cartilage that covers joint surfaces, allowing joints to move more freely.

Periosteum

External sheath covering most of bone; consists of an outer fibrous layer and an inner osteogenic layer for bone growth and repair.

Compact (Dense or Cortical) Bone

The dense outer shell of bone that encloses the marrow (medullary) cavity.

Spongy (Cancellous) Bone

Loosely organized bone tissue found in the center of bone ends and shafts, covered by compact bone.

Nutrient Foramen

A tunnel that penetrates the diaphysis and provides access for the nutrient artery and/or vein.

Bone Marrow

Soft tissue occupying marrow cavities of long bones and small spaces of spongy bone.

Red Marrow (Myeloid Tissue)

Hemopoietic tissue that produces blood cells, found in skull, vertebrae, ribs, sternum, pelvic girdle, and proximal humerus/femur in adults.

Yellow Marrow

Fatty marrow found in adults, primarily for triglyceride storage.

Endosteum

A thin reticular connective tissue layer that lines the marrow cavity, covers spongy bone surfaces, and lines canal systems; contains cells for bone dissolution and deposition.

Diaphysis

The shaft of a long bone, providing leverage.

Epiphysis

The enlarged end of a long bone that strengthens the joint and anchors ligaments and tendons.

Epiphyseal Line

The remnant of the childhood growth zone, the epiphyseal plate.

Diploe

The spongy middle layer of flat bones, which absorbs shock.

Osteogenic Cells

Stem cells found in the endosteum and inner layer of the periosteum that multiply continuously and give rise to osteoblasts.

Osteoblasts

Bone-forming cells that synthesize the soft organic matter of the matrix and promote its mineralization (osteogenesis).

Osteocytes

Former osteoblasts trapped in the matrix they deposited; reside in lacunae and act as strain sensors, regulating bone remodeling.

Lacunae

Tiny cavities where osteocytes reside within the bone matrix.

Canaliculi

Little channels that connect lacunae, allowing cytoplasmic processes of osteocytes to contact neighboring cells.

Osteoclasts

Bone-dissolving cells found on bone surfaces that perform osteolysis as part of bone remodeling.

Bone Matrix

Composed of about one-third organic matter (collagen, carbohydrate-protein complexes) and two-thirds inorganic matter (hydroxyapatite, calcium carbonate).

Hydroxyapatite

The crystallized calcium phosphate salt that makes up 85% of the inorganic matter of bone.

Rickets

A disease caused by mineral deficiency, resulting in soft, deformed bones.

Osteogenesis Imperfecta

Brittle bone disease that results from a defect in collagen deposition.

Osteon

The functional unit of compact bone, consisting of a central canal and its concentric lamellae.

Concentric Lamellae

Layers of matrix surrounding a central (haversian) canal in compact bone.

Perforating Canals (Volkmann's Canals)

Transverse or diagonal passages that connect central canals in compact bone.

Spicules

Slivers of bone found in spongy bone.

Trabeculae

Thin plates of bone found in spongy bone, often arranged along lines of stress.

Ossification

The formal term for the process by which bone forms.

Intramembranous Ossification

A process of bone formation that produces flat bones of the skull and clavicle in the fetus, and thickens long bones throughout life.

Endochondral Ossification

A process where bone develops from a hyaline cartilage model, producing most bones of the body (e.g., bones of limbs, vertebrae, ribs).

Chondroblasts

Cells that form the hyaline cartilage model during endochondral ossification.

Primary Ossification Center

The first region where bone tissue replaces cartilage in endochondral ossification, typically in the diaphysis.

Secondary Ossification Center

Ossification centers that appear in the epiphyses during endochondral ossification.

Metaphysis

A region of transition between cartilage and bone during endochondral ossification, particularly important for long bone elongation.

Interstitial (Longitudinal) Growth

The increase in length of long bones due to chondrocyte proliferation and hypertrophy at the epiphyseal plate.

Appositional Growth

The increase in bone thickness or diameter, occurring at the bone surface through deposition by osteoblasts of the inner periosteum.

Mineral Deposition (Mineralization)

The process in which calcium, phosphate, and other ions are taken from the blood and deposited into bone tissue by osteoblasts.

Mineral Resorption

The process of dissolving bone and releasing minerals into the blood, performed by osteoclasts.

Bone Remodeling

The continuous process of absorption and deposition of bone throughout life, repairing microfractures, releasing minerals, and reshaping bones in response to stress.

Wolff’s Law of Bone

States that the architecture of bone is determined by the mechanical stresses placed upon it.

Calcium Homeostasis

The regulation of calcium concentration in the blood, maintained by the balance of dietary intake, urinary/fecal losses, and exchanges with osseous tissue, controlled by hormones.

Calcitriol

The most active form of vitamin D, produced by actions of the skin, liver, and kidneys; primarily responsible for getting calcium into the body via intestines and bone deposition.

Parathyroid Hormone (PTH)

Secreted by the parathyroid glands when blood calcium levels are low; increases blood calcium by stimulating osteoclasts, enhancing calcitriol, and promoting calcium reabsorption in kidneys.

Calcitonin

Secreted by C cells of the thyroid gland when blood calcium levels rise too high; lowers blood calcium by inhibiting osteoclasts and stimulating osteoblasts to deposit calcium into bone.

Stress Fracture

A break caused by abnormal trauma to a bone.

Pathological Fracture

A break in a bone weakened by disease, usually caused by stress that would not break a healthy bone.

Simple Fracture

A completely internal bone break, not protruding through the skin.

Compound Fracture

A bone break where the bone projects through the skin.

Comminuted Fracture

A fracture where the bone is broken into three or more pieces.

Greenstick Fracture

A fracture common in children where one side of the bone shaft is broken and the other side is bent.

Compression Fracture

A fracture that occurs in vertebrae subjected to extreme stresses.

Spiral Fracture

A fracture produced by twisting stresses, spreading along the length of the bone.

Hematoma

A blood clot that forms at the site of a bone fracture due to torn blood vessels.

Soft Callus

Fibrous connective tissue and cartilage that forms after a fracture to bridge the broken bone ends, serving as a temporary repair tissue.

Bony Callus (Hard Callus)

The conversion of the soft callus into spongy bone, immobilizing the fracture site.

Osteoporosis

The most common bone disease characterized by severe loss of bone density, making bones brittle and susceptible to pathological fractures.

Estrogen

A hormone that helps maintain bone density and inhibits resorption by osteoclasts; its deficiency, such as during menopause, increases osteoporosis risk.