A&P - Bone Tissue

Bone

Highly vascularized C.T. with a hard, mineralized extracellular matrix.

Compact bone

Dense, hard outer layer of bone tissue that provides support for the diaphysis.

Spongy bone

Less organized tissue that is lightweight and provides tissue support, forming much of the epiphysis and internal cavity of long bones.

Cartilage

Poorly vascularized C.T. with a matrix composed of chondroitin sulfate and other fibers, like hyaline cartilage, fibrocartilage, and elastic cartilage.

Articular cartilage

The thin layer of hyaline cartilage covering the epiphysis of long bones. Found where for bone forms a joint.

Articular (joint) surface

Where one bone moves against another bone.

Periosteum

Tough sheath of dense, irregular connective tissue on the outside of the bone. Has osteoblasts, repairs, and serves as an attachment point.

Diaphysis

Shaft or body of a long bone

Epiphyses

Distal and proximal ends of a long bone

Metaphyses

Areas where the epiphyses and diaphysis join.

Epiphyseal growth plate

Hyaline cartilage at the epiphysis of long bones in adolscents, actively dividing and causing the bone to elongate from each end.

Epiphyseal line

Comes from the epiphyseal growth plate in adults, where growing cartilage is replaced by calcified bones.

Medullary cavity

Space within the diaphysis of long bones that contain fatty bone marrow in adults.

Endosteum

A membrane that lines the medullary cavity, composed of osteoclasts, osteoblasts, and connective tissue.

Perichonrium

Dense irregular connective tissue membrane that surrounds cartilage.

Chondrocytes

Cells that form cartilage.

Osteoblasts

Bone building cells that synthesize and secrete collagen fibers and other organic components.

Osteocytes

Mature osteoblasts that maintain bone tissue.

Osteoclasts

Large bone breakdown cells, coming from white blood cells that migrate from the bone marrow to become fixed macrophages.

Tissues of the skeletal system

Epithelium, Nerves, Red marrow, Yellow marrow.

Organic constituents of the bone

Collagen fibers provide flexibility and tensile strength

Inorganic hydroxyapatite crystals in the bone

Calcium Phosphate and Calcium Carbonate

Osteons (Haversian system)

Functional and structural unit of the compact bone, formed from concentric lamellae.

Concentric lamellae

Rings of calcified matrix

Intersititial lamellae

Leftover fragments of older osteons.

Outer circumferential lamellae

Circle the bone beneath the periosteum

Inner circumferential lamellae

Encircle the medullary cavity.

Lacunae

Small spaces between the lamellae which houses osteocytes

Canaliculi

Small channels filled with extracellular fluid connecting the lacunae.

Osteon central canal

Contains blood and lympatic vessels in the bone.

Perforating (Volkmann’s) canals

Allow transit of these vessels to the outer cortex of the bone.

Trabeculae

Lamellae arranged in a lattice of thin columns that make up the lack in osteons for spongy bone.

They support and protect the red bone marrow along lines of stress and help produce blood cells.

Hematopoiesis

Blood cell production that occurs in the spongy bone.

Ossification

The process of forming new bone. Occurs in: bone formation in embryos, growth of bones until adulthood, remodeling of bone, and repair of fractures.

Intramembranous ossification

Produces spongy bone where bone may subsequently be remodeled to form compact bone.

Endochondral ossification

Process whereby cartilage is replaced by bone, forming both compact and spongy bone.

Development of ossification center

First step of Intramembranous ossification.

Osteoblasts secrete organc extracellular matrix.

Calcification

Second step of Intramembranous ossification.

Calcium and other mineral salts are deposited and extracellular matrix hardens.

Formation of trabeculae

Third step of Intramembranous ossification.

Extracellular matrix develops into trabeculae that fuse to form spongy bone.

Development of the periosteum

Fourth step of Intramembranous ossifcation.

Mesenchyme at the periphery of the bone develops into the periosteum.

Development of cartilage model

First step of Endochondral ossification

Mesenchymal cells develop into chondroblasts, which form the cartilage model.

Growth of cartilage model

Second step of Endochondral ossification

Growth occurs by cell division of chondrocytes.

Development of primary ossification center

Third step of Endochondral ossification

In this region of the diaphysis, bone tissue replaced most of the cartilage.

Development of the medullary (marrow) cavity

Fourth step of Endochondral ossification

Bone breakdown by osteoclasts forms the medullary cavity.

Development of secondary ossification centers

Fifth step of Endochondral ossification

Occur in the epiphyses of the bone.

Formation of articular cartilage of epiphyseal plate

Sixth step of Endochonral ossification

Both structures consist of hyaline cartilage.

Vitamin A

Stimulates activity of osteoblasts

Vitamin C

Needed for synthesis of collagen

Vitamin D

Essential to healthy bones because it promotes the absorption of calcium from foods in the gastrointestinal tract into the blood.

Vitamins K and B12

Needed for synthesis of bone proteins.

hGH and IGFs

Hormones that stimulate osteoblasts, promote cell division at the epiphyseal plate, and enhance protein synthesis.

Thyroid hormones

Promote bone growth by stimulating osteoblasts and protein synthesis.

Parathyroid hormone and calcitonin

Critical for balancing the levels of calcium and phosphorus between blood and bone.