Bone Tissue

Yellow Bone Marrow

Triglyceride storage [fat storage] -consists of mainly adipose cells, which store triglycerides; the stored triglycerides are a potential chemical energy reserve.

Osteoblast

"bone builders" bone-forming cells; initiate calcification Synthesis and secrete collagen fibers and compounds needed to build the extracellular matrix of bone tissue. They also initiate calcification; as osteocytes surround themselves with extracellular matrix, they become trapped in their secretion and become osteocytes. Undergo cell division, become Osteocytes.

Osteoclast

"breakdown and absorb matrix" bone resorbing cells; form from monocytes. Huge cell derived from 50 monocytes (WBCs), concentrated in the endeosteum. They break down bone extracellular matrix (resorption). Reabsorbs bony matrix.

Osteon (Haversian system)

Basic unit of structure in an adult compact bone consists of a central (haversian) canal with concentrically arranged lamallae, lacunae, osteocytes, and canaliculi.

Red Bone Marrow

Blood cell production produces red blood cells, white blood cells, and platelets; this CT producing cells takes part in hemopoiesis. Develops blood cells, adipocytes, fibroblasts, and macrophages within a network of reticular fibers. Present at birth.

Endochondral ossification

Bone forms by replacing hyaline cartilage Forms most of the rest of the skeleton Development of hyaline cartilage model Perichondrium surrounds cartilage model Growth of cartilage model - chondroblasts mature into chondrocytes Bone grows in length - interstital (endogenous) growth (via epiphyseal growth plate) Bone grows in thickness - appositional (exogenous) growth Ossification begins: traps chondrocytes & some die, leaving behind holes = lacunae Primary ossification center develops Osteoblasts become active - periosteum forms Development of medullary cavity Development of 2° ossification centers in epiphyses. Formation of articular cartilage & the epiphyseal plate (growth plate) Development of most of long bones.

Endeosteum

Inner lining of the medullary cavity, covers trabecullae. composed of osteoclasts, osteoblasts, and a small amount of connective tissue.

Intramembranous ossification

Membrane bone develops from fibrous membrane Forms flat bones (clavicles and cranial bones) Development of ossification center - osteoblasts secrete organic extracellular matrix of bone until they are surrounded by it Calcification - cells are now called osteocytes and lie in lacunae; mineral salts deposited within few days Formation of trabeculae - spongy bone is formed; red bone marrow develops Development of periosteum - thin layer of compact bone replaces surface layers of spongy bone Spongy bone remains in center [one type of ossification]

Canaliculi

Small channels or canals, as in bones, where they connect lacunae.

Lacunae

are small spaces between the lamellae which house osteocytes.

Interstitial lamellae

between osteons are left over fragments of older osteons; fragments of older osteons that have been partially destroyed during bone rebuilding or growth. (in areas between neighboring osteons).

Concentric lamellae

circular plates of mineralized extracellular matrix arranged in tube-like units. -Surrounded by collagen fibers which contribute to the flexibility and tensile strength Circular planes of mineralized extracellular matrix of increasing diameter, surrounding a small network of blood vessels and nerves located in the central canal. (rings of calcified matrix)

Central (Haversian) Canal

contains blood vessels, lymphatics, and nerves. A circular channel running longitudinally in the center of an osteon (haversian system)( of a mature compact bone, containing blood vessels and lymphatic vessels and nerves.

Calcitonin

decreases blood Ca2+ level when it gets too high (From thyroid gland) (+) Stimulates osteoblasts (-) Inhibits osteoclasts

Parathyroid hormone

increases blood CA2+ level to help maintain bones (+) increase in osteoclasts (-) decrease in osteoblasts Demineralizing of bones

Vitamin D

increases the absorption of calcium, strengthens bones.

Volkmann's (Perforating) canals

its vessels and nerves connect with the nerves and vessels of the medullary cavity, periosteum, and central canals. Connect osteons together.

Spongy Bone

lightweight and provides tissue support; allows bone to move readily when pulled by skeletal muscle. (Epiphysis, Internal cavity of long bones). Cancellous or trabecular bone Makes up most of the interior bone tissue of flat, short, sesamoid, and irregularly shaped bone; protected by a covering of compact bone. Located where bones are heavily stressed, or where stress comes from many directions. Site of red bone marrow - site of blood cell production Differs from compact (1) light weight, reducing overall weight of bone and (2) trabeculae support and protect red bone marrow Lamellae are arranged in a lattice of thin columns called trabeculae Trabeculae support and protect the red bone marrow and are oriented along lines of stress Helps bones resist stresses without breaking Hematopoiesis (blood cell production) Within each trabecula are lacunae Contain osteocytes that nourish the mature bone tissue from the blood circulating through the trabeculae. Consists of lamellae arranged in an irregular pattern of columns (trabeculae); spaces between lamellae are filled with red bone marrow in bones that produce cells.

Osteocyte

mature bone cells; form when osteoblasts are trapped within their own secretions. Mature bone cells (main bone tissue cells) that maintain the exchange of nutrients and wastes in the blood; don't undergo cell division. Stuck in lacuna.

Vitamin B12 and K

needed for synthesis of bone proteins

Vitamin C

needed for synthesis of collagen, the main bone protein

Vitamin A

stimulates osteoblasts, bone growth.

Periosteum

tough sheath of dense, irregular connective tissue proper on the bone surface. Attached to underlying bone by Sharpey's fibers. Blood vessels and nerves enter through nutrient foramina. -contains osteoblasts that help the bone grow in THICKNESS, but NOT in length. -assists with FRACTURE REPAIR and serves as an attachment point for tendons and ligaments. Dense CT proper that thickens and repairs bones.