Chapter 6 The Skeletal System: Bone Tissue

Vocabulary flashcards covering the functions, structure, histology, formation, and homeostasis of bone tissue from Principles of Anatomy and Physiology, Chapter 6.

Bone

An organ made up of several different tissues including bone, cartilage, dense connective tissue, adipose, and nervous tissue working together.

Skeletal system

The entire framework of bones and their cartilages.

Support

A function of the skeletal system that provides a structural framework for the body.

Protection

A function of the skeletal system that shields internal organs like the brain and heart.

Mineral homeostasis

The storage and release of calcium and phosphorus by bone tissue to maintain critical balances.

Hemopoiesis

The process of blood cell production that takes place in bone tissue.

Yellow marrow

The site where triglycerides are stored in adipose cells within the skeletal system.

Diaphysis

The bone shaft of a long bone.

Epiphyses

The two ends of a long bone located at the joints.

Metaphyses

The regions in a long bone located between the diaphysis and the epiphysis.

Articular cartilage

A layer of cartilage covering both epiphyses where the bone forms a joint.

Periosteum

The connective tissue that surrounds the diaphysis of a long bone.

Medullary cavity

The hollow space within the diaphysis of a long bone.

Endosteum

The thin membrane that lines the medullary cavity.

Epiphyseal line

A structure found in the metaphysis of a sectioned humerus that represents the remnant of the growth plate.

Bone Extracellular Matrix

Materal surrounding bone cells containing approximately $15\%$ water, $30\%$ collagen, and $55\%$ crystallized mineral salts.

Osteoprogenitor cells

Bone stem cells that are able to differentiate into other types of bone cells.

Osteoblasts

Bone-building cells that secrete the organic extracellular matrix.

Osteocytes

Mature bone cells that maintain the bone tissue.

Osteoclasts

Cells derived from white blood cell lineage that remodel bones and function in resorption, the breakdown of bone extracellular matrix.

Compact bone

A type of bone tissue that is good at providing protection and support.

Spongy bone

A lightweight type of bone tissue that provide tissue support and contains trabeculae.

Osteons

The functional units of compact bone, also known as haversian systems.

Trabeculae

The structural lattice of thin columns found in spongy bone tissue.

Lacuna

Small spaces within the bone matrix that house osteocytes.

Canaliculi

Tiny channels that connect lacunae and provide routes for nutrients and oxygen.

Volkmann’s canals

Also called perforating canals; they allow periosteal arteries and nerves to enter the diaphysis.

Nutrient foramen

An opening in the center of the diaphysis through which the nutrient artery enters.

Ossification

The process of bone formation, also referred to as osteogenesis.

Intramembranous ossification

The process where a connective tissue membrane is replaced by bone, occurring in flat bones like the skull and mandible.

Endochondral ossification

The process of replacing cartilage with bone in the developing embryo and fetus.

Epiphyseal plates

Areas in long bones where endochondral ossification occurs to allow for growth in length.

Bone thickening

The cooperative action where osteoblasts deposit bone on the outer surface while osteoclasts widen the medullary cavity from within.

Fracture

A break in a bone.

Reactive phase

The early inflammatory phase of bone repair involving the formation of a fracture hematoma.

Reparative phase

The stage of bone healing that includes the formation of a fibrocartilaginous (soft) callus followed by a bony (hard) callus.

Bone remodeling phase

The final step in fracture repair where the bony callus is reshaped.

Parathyroid hormone (PTH)

A hormone produced by parathyroid gland cells when blood calcium levels drop, stimulating osteoclasts to increase bone resorption.

Calcitriol

The active form of Vitamin D produced by the kidneys that increases calcium absorption in the intestines.

Calcitonin (CT)

A hormone secreted by the thyroid gland that inhibits bone resorption by osteoclasts.

Magnesium

A mineral that helps form the bone extracellular matrix.

Fluoride

A mineral that helps strengthen the bone extracellular matrix.

Manganese

A mineral that activates enzymes involved in the synthesis of the bone extracellular matrix.

Vitamin A

A vitamin needed for the activity of osteoblasts during bone remodeling; deficiency stunts bone growth.

Vitamin C

A vitamin needed for the synthesis of collagen, which is the main bone protein.

Vitamin K and B12

Vitamins required for the synthesis of bone proteins; deficiency leads to decreased bone density.

Growth hormone (GH)

A hormone from the anterior pituitary that promotes general growth of body tissues including bone.

Insulin-like growth factors (IGFs)

Factors secreted by the liver and bones that promote normal bone growth by stimulating osteoblasts and protein synthesis.

Sex hormones

Estrogens and testosterone which stimulate osteoblasts, promote teenage growth spurts, and eventually shut down growth at epiphyseal plates around age $18-21$.

Osteoporosis

A condition where bone resorption outpaces bone deposition, leading to a decrease in bone mass and increased risk of fracture.