Anatomy ch 6

• 1. Support
• 2. Protection
• 3. Assistance in Movement
• 4. Mineral homeostasis
• 5. Blood cell production (Red bone marrow)
• 6. Triglyceride storage (yellow bone marrow)

red bone marrow producing red blood cells, white blood cells, and platelets

• bone's shaft or body
• 

distal and proximal ends of the bone

regions in the mature bone where the diaphysis joins the epiphyses

part of the metaphysis - a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length

in a mature bone the cartilage of the epipyseal plate is replaced by bone

thin layer of hyaline cartilage covering the part of the eipihysis where the bone forms an articulation (joint) with another bone

• tough sheath of dense irregular CT that surround the bone surface wherever it is not covered by articular cartilage
• bone-forming cells of periosteum enable bone to grow in thickness but not length
• protect the bone, assists in fracture repair, helps nourish bone tissue, and serves as attachment point for ligaments and tendons

thick bundles of collagen fibers that extend from the periosteum into the extracellular bone matrix (attaches periosteum to bone)

marrow cavity - space within the diaphysis that contains fatty yellow bone marrow in adults

• thin membrane that lines the medullary cavity
• contains single layer of bone-forming cells and a small amount of CT

• mineralization - minerals form crystals in presence of collagen fibers
• crystals laid over collagen fibers
• crystals - hardness
• collagen fibers - tensile strength

resistance to being stretched or torn apart

• 1. Osteogenic cells
• 2. Osteoblasts
• 3. Osteocytes
• 4. Osteoclasts
• 

• stem cells (from mesenchymal cells)
• only bone cells to undergo cell division - produces osteoblasts
• located in the periosteum, endosteum, and in bony canals with blood vessels

• produce new bone matrix
• when they are completely surrounded by bone matrix, osteoblasts transform into osteocytes

• mature bone cells located in lacunae (little lake)
• maintain the bone tissue

• break down bone - resorption
• large, multinucleated cells - numerous monocytes joined
• located in endosteum
• ruffled border - plasma membrane is deeply folded - contains powerful lysosomal enzymes and acids to break down bone matrix

• performed by osteoclasts
• breakdown bone extracellular matrix - part of normal bone development, growth, maintenance, and repair

• contains few spaces - dense
• form superficial part of bones (right below periostium)
• 80% of all bones in body
• basic unit is an osteon

• 1. Volkmann's canals (Perforating canals) - run perpendicular to bone surface - house blood vessels, lymphatic vessels, & nerves
• 2. Central canal - parallel to bone surface (center of osteon) - surrounded by concentric lamellae
• 3. Concentric lamellae - rings of bony matrix
• 4. Lacunae - little lake - openings between concentric lamellae that house osteocytes
• 5. Canaliculi - tiny canals through which osteocyte extensions form different lacunae connect to each other and to the central canal
• 

• located in spaces between osteons
• remnants of broken down osteons

lamellae that encircles the bone just beneath the periosteum or encircle the medullary cavity

• Trabeculae - loose network of thin beams
• contain lacunae with osteocytes and canaliculi - no osteons
• make up most of short, fat and irregular bone (deep part- surface is compact bone)
• found in long bones in the epiphyses and around medullary cavity
• reduced weight of skeleton
• able to withstand stress form many directions
• protect and support red bone marrow - site of hemopoiesis (blood production)
• 

• 1. Periostial arteries - supply periosteum and superficial part of diaphysis
• 2. Nutrient arteries - enter through nutrient foramen and sends proximal and distal branches out (supplies deeper part of diaphysis and medullary cavity
• 3. Metaphyseal arteries - supply red bone marrow and metaphyses
• 4. Epiphyseal arteries - supply epiphyses

• process of bone formation
• 1. embryonic skeleton - template of CT and hyaline cartilage
• 2. ossification of template occurs - 6th or 7th week of embryonic development in one of two ways:

• A. Intramembranous ossification
• B. endochondral ossification

• bone building within membranes -bone forms in or on CT membranes
• results in flat bones
• 1. Ossification centers develop where osteoblasts are actively producing matrix
• 2. Osteocytes form and matrix calcifies with the arrival of minerals
• 3. Trabeculae develop and form spongy bone
• 4. Periosteum develops and compact bone replaces spongy bone at the surface

• within cartilage - hyaline cartilage template becomes ossified
• results in most bones
• 1. Development of cartilage model from mesenchymal cells - chondrocytes produce hyaline model surrounded by perichondrium (turns to perichondrium when produces bone)
• 2. Growth of cartilage model in length and width - chondrocytes enlarge and burst - release acids to foster calcification - other chondrocytes die leaving empty spaces (lacunae)
• 3. Development of primary ossification centers -a region where bone tissue replaces cartilage - osteoblasts lay down spongy bone - Osteoblasts develop in deep regions of periochondreum and produce the Periosteal Bone Collar
• 4. Development of medullary cavity - osteoclasts break down newly formed spongy bone leaving cavity in shaft
• 5. Development of secondary ossification center - branches of epiphyseal arteries grow into epiphyses and stimulates ossification
• 6. Formation of articular cartilage and epiphyseal plates - remnants of hyaline cartilage become articulating (joint) cartilage - hyaline cartilage remnents between diphysis and epiphyses form epiphyseal plate

• interstitial growth - growth from within - increase in length
• appositional growth - increase in thickness - addition of extracellular matrix material to the periphery by new chondroblasts that develop from the perichondrium

• layer of hyaline cartilage in the metaphysis of a growing bone
• Zones:
• 1. Zone of resting cartilage - layer nearest the epiphysis
• 2. Zone of proliferating cartilage - large chondrocytes undergo interstitial growth as they divide and secrete extracellular matrix
• 3. Zone of calcified cartilage - extracellular matrix calcifies and adds to diaphysis

• bone remodeling -ongoing replacement of old bone tissue by new bone tissue
• bone resorption - removal of minerals and collagen fibers from bone by osteoclasts
• bone deposition - addition of minerals and collagen fibers to bone by osteoblasts

• Fracture - any break in any bone
• 1. Open (Compound fracture) - protrudes through skin
• 2. Closed (simple) fracture - not protrude through skin
• 3. Comminuted fracture - bone splinters and produces fragments
• 4. Greenstick fracture - shaft is not completely broken (only in children - nones not fully ossified)
• 5. Impacted fracture - one broken end driven inside other broken end
• 6. Pott's fracture - at ankle - both tibia and fibula are involved
• 7. Colles' fracture - distal end of radius is displaced posteriorly
• 8. Stress fracture - minute tears - commonly tibia - due to exercise or osteoporosis

• 1. Formation of fracture hematoma - blood leaking from torn vessels clot around the fracture (6 to 8 hours) blood stops - nearby bone tissue dies - phagocytes and osterclasts remove damaged tissue (several weeks)
• 2. Fibrocartilaginous callus formation - a mass of repair tissue consisting of collagen fibers and cartilage that bridges the broken ends of the bone (3 weeks)
• 3. Bony callus formation - fibrocartilage is converted into spongy bone (called bony callus lasts 3 to 4 months)
• 4. Bone remodeling - bone remodeling of callus - spongy bone turned into compact bone around periphery.

• secreted by parathyroid gland
• hormone that increses the blood calcium level (negative feedback system)

hormone that promotes absorption of calcium from foods in the gastrointestional tract into the blood

the loss of calcium and other minerals from bone extracellular matrix

bones that lie around the longitudinal axis of the human body - skull, ribs, sternum, vertebral column

bones of upper and lower limbs plus the girdles that connect the limbs to the axial skeleton

• greater length than width
• consist of a shaft and variable number of extremities
• are curved for strength
• consist of mostly compact bone in diaphysis with spongy bone in epephises

• somewhat cube-shaped and are nearly equal in length and width
• spongy bone except at surface - thin layer of compact bone
• carpals, tarsals

thin and composed of two parallel layers of compact bone enclosing a layer of spongy bone

cranial bones, ribs

• shaped like a sesame seed
• develop in certain tendons where there is considerable friction, tension, and physical stress

patella

complex shapes - cant be grouped elsewhere - very in amount of compact and spongy bone

• vertebra
• hip bones
• facial bones

small bones located in sutures between cranial bones