Chapter 07 Skeletal System: Bone Structure and Function - Vocabulary

Vocabulary flashcards covering key terms from the lecture notes on bone structure, function, growth, and remodeling.

Skeletal system components

Bones, cartilage, ligaments, and other connective tissues that provide support, protection, movement, hematopoiesis, and mineral storage.

Compact bone

Dense or cortical bone; 80% of bone mass; forms the outer layer and provides stiffness and protection.

Spongy bone

Cancellous or trabecular bone; 20% of bone mass; located internal to compact bone; appears porous and houses bone marrow.

Long bone

Bones with greater length than width; examples include the femur and humerus; function as levers for movement.

Short bone

Bones with length nearly equal to width; examples include carpals and tarsals; provide stability with little movement.

Flat bone

Flat, thin surfaces (often curved) such as cranial bones; typically with two compact bone layers separated by spongy bone.

Irregular bone

Bones with elaborate shapes (e.g., vertebrae) that do not fit other categories.

Diaphysis

The shaft of a long bone; cylindrical, provides leverage and weight support; contains a medullary cavity.

Epiphysis

Knobby ends of a long bone; outer compact bone with an inner region of spongy bone; covered by articular cartilage.

Metaphysis

Region where bone widens and transfers weight between the diaphysis and epiphysis; contains the epiphyseal plate in growing bones.

Epiphyseal plate

Growth plate of hyaline cartilage that allows lengthwise bone growth; in adults, it becomes the epiphyseal line.

Periosteum

Tough membrane covering the outer surface of bone; has an outer fibrous layer and an inner cellular layer with osteoprogenitor cells and osteoblasts; attached by perforating fibers.

Endosteum

Innermost lining of bone within the medullary cavity; contains osteoprogenitor cells and osteoblasts.

Osteoprogenitor cells

Bone stem cells derived from mesenchyme; differentiate into osteoblasts; located in periosteum and endosteum.

Osteoblasts

Bone-forming cells that synthesize osteoid; may become entrapped and differentiate into osteocytes.

Osteocytes

Mature bone cells that maintain the bone matrix and sense mechanical stress.

Osteoclasts

Large, multinucleate cells that resorb bone; originate from fused bone marrow cells; have a ruffled border and a resorption lacuna.

Osteoid

Organic component of the bone matrix produced by osteoblasts; contains collagen and ground substance; later mineralizes.

Hydroxyapatite

Inorganic calcium phosphate crystals that harden the bone matrix; intermingle with collagen.

Hematopoiesis

Blood cell production, occurring in red bone marrow.

Red bone marrow

Hematopoietic tissue; in children located in spongy bone and medullary cavities; in adults mostly in axial skeleton.

Yellow bone marrow

Fatty marrow formed from red marrow degeneration; can convert back to red marrow in severe anemia.

Nutrient foramen

Opening in bone through which arteries enter and veins exit to supply the bone.

Osteon

Structural unit of compact bone consisting of concentric lamellae around a central (Haversian) canal; contains osteocytes in lacunae and canaliculi.

Central (Haversian) canal

Channel within an osteon that contains blood vessels and nerves.

Lacuna

Small spaces between lamellae that house osteocytes.

Canaliculi

Tiny channels that connect lacunae with each other and with the central canal to allow exchange of nutrients and wastes.

Trabeculae

Open lattice of rods/plates in spongy bone; spaces fill with bone marrow; provides structural support.

Intramembranous ossification

Bone formation within a thickened region of mesenchyme (dermal ossification); forms flat bones like skull; steps include ossification centers, calcification of osteoid, woven bone formation, periosteum formation, and replacement by lamellar bone.

Endochondral ossification

Bone formation from a hyaline cartilage model; forms most bones (limbs, pelvis, vertebrae); involves periosteal bone collar, primary and secondary ossification centers, and epiphyseal plates.

Epiphyseal plate zones

Five zones: resting cartilage, proliferating cartilage, hypertrophic cartilage, calcified cartilage, and ossification; collectively govern lengthwise growth of bone.

Appositional growth

Growth in width; occurs at the periosteum with bone deposition outward and resorption along the medullary cavity to widen the shaft.

Interstitial growth

Growth in length; occurs at the epiphyseal (growth) plate via zones 2 and 3, pushing resting cartilage toward the epiphysis and forming mature bone.

Calcitriol

Active form of vitamin D; increases calcium absorption from the small intestine; production enhanced by PTH.

Parathyroid hormone (PTH)

Hormone that raises blood calcium by stimulating osteoclasts, increasing renal calcium reabsorption, and, with calcitriol, promoting intestinal calcium absorption.

Calcitonin

Thyroid hormone that lowers blood calcium by inhibiting osteoclasts and increasing calcium loss in urine; has a minor role compared to PTH/calcitriol.

Osteoporosis

Significant loss of bone mass with aging, leading to weakened bones and higher fracture risk; assessed by bone mineral density (DEXA).

Osteopenia

Lower-than-normal bone mineral density that precedes osteoporosis; common with aging, more pronounced in women.

Rickets

Vitamin D deficiency in childhood causing defective calcification of osteoid and bowing of bones.

Achondroplasia

Most common form of dwarfism; abnormal endochondral ossification leading to short limbs despite normal torso; due to failure of chondrocyte growth in the epiphyseal plate.

Fracture

A break in a bone; types include stress fracture, pathologic fracture, simple (closed), and compound (open) fractures.

Fracture healing steps

Hematoma formation; fibrocartilaginous (soft) callus formation; hard (bony) callus formation; remodeling to replace primary bone with stronger bone.