Chapter 6: Skeletal System: Bones and Bone Tissue
ruffled border
areas where the plasma membrane of osteoclasts contacts the bone matrix
zone of calcification
is very thin and contains hypertrophied chondrocytes and calcified cartilage matrix. The hypertrophied chondrocytes die, and blood vessels from the diaphysis grow into the area.
bone matrix
composed of 35% organic and 65% inorganic material
bone growth
only occurs via appositional growth; new bone on the surface of older bone or cartilage
four basic bone shapes
1. long bone - longer than they are wide (upper and lower limbs) 2. short bone - round or nearly cubed-shaped (wrist bone and ankle bone) 3. flat bone - relatively thin, flattened shape and usually curved (skull bones, ribs, sternum, shoulder blades) 4. irregular bone - does not fit readily into the other 3 categories (vertebrae and facial bones)
calcified cartilage
Cartilage tissue in which inorganic calcium salts are deposited in the matrix, which occurs prior to replacement by osseous tissue, and sometimes in aging cartilage.
perichondrium
Dense irregular connective tissue membrane covering cartilage. blood vessels penetrate outer layer, but do not enter the cartilage matrix
periosteum
a dense fibrous membrane covering the surface of bones (except at their extremities) and serving as an attachment for tendons and muscles;
fontanels
a soft, membrane-covered space between the bones at the front and the back of a newborn's skull
woven bone
immature bone present during fetal development or in the early stages of bone repair (after a fracture); collagen fibers are randomly distributed and have crisscross pattern
hematoma
localized mass of blood released from blood vessels, but confined in an organ or space; usually forms a clot that stops the bleeding; adjacent tissue to the bone fracture site dies
compact bone
dense and thick bone matrix; lamellae are oriented around blood vessels that enter the bone
interstitial growth
type of cartilage growth where chondrocytes within the tissue divide and add more matrix between the existing cells.
endosteum
vascular membrane that lines the inner surface of long bones
factors affecting bone growth
1. nutrition - vitamin d is necessary for the normal absorption of calcium from the intestines; vitamin c is necessary for collagen synthesis by osteoblasts 2. hormones - growth hormone stimulates cartilage growth and appositional bone growth, thyroid hormone necessary for growth of all tissues including cartilage; estrogen and testosterone stimulate bone growth.
five major functions of skeletal system
1. support - strong bone sutied for bearing weight. cartilage provides firm yet flexible support. ligaments are strong bands of fibrous connective tissue that attach to bone 2. protection - protects organs 3. movement - muscles attach to bones via tendons 4. storage - mineral in blood are taken into bone and stored. if blood levels of these minerals decrease, minerals released from bone 5. blood cell production - bones contain cavities filled w/ red bone marrow which gives rise to blood cells and platelets
zone of proliferation
2nd region of epiphyseal plate; made of a column of flattened cells. Region of rapid proliferation of chondroblasts from isogenous group. Actively makes cartilage via intersititial growth
center of ossification
A location in a developing bone where osteoblasts produce and secrete bone matrix
haversian system
A unit of compact bone consisting of a tube (haversian canal) with the laminae of bone that surrounds it
growth at articular cartilage
Increases size of bones with no epiphyses: e.g., short bones; chondrocytes near the surface of the articular cartilage similar to those in zone of resting cartilage
central canal
The hollow center of an osteon, also known as a Haversian canal. The central canal contains blood vessels, lymphatic vessels, and nerves. Bone is laid down around the central canal in concentric rings called lamellae.
osteon
The unit of combact bone, also called a Haversian system. Osteons are essentially long cylinders of bone; the hollow center is called the central canal, and is where blood vessels, nervs, and lymphatic vessels are found. Compact bone is laid down around the central canal in rings (lamellae). cut in cross section it resembles a bullseye
sinuses
air filled spaces inside flat and irregular bones that are lined with mucous membranes
zone of resting cartilage
anchors growth plate to bone
osteoblasts
bone-forming cells; produce collagen and proteoglycans
articular cartilage
cartilage covering the ends of bones where they come together to form joints. has no perichondrium
epiphyseal plate
cartilaginous area at the ends of long bones where lengthwise growth takes place in the immature skeleton; separates the epiphysis from the diaphysis
medullary cavity
cavity within the shaft of the long bones; filled with bone marrow
chondroblasts
cells that produce cartilage matrix
volkmann's canals aka perforating canals
channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal
zone of hypertrophy
chondrocytes mature and enlarge
three types of lamellae
concentric - circular layers of bone matrix that surround a common central canal circumferential - thin plates that extend around the bone (outer surfaces of central canal) interstitial - between osteaons; remnants of concentric or circumferential lamellae that were partially removed during bone remodling
spongy bone
consists of interconnecting rods or plates of bone called trabeculae; the spaces are filled with bone marrow and blood vessels
bone remodling
converts old woven bone to new lamellar bone. is involved in bone growth, changes in bone shape, adjustment of bone to stress, bone repair, and calcium ion regulation in the body. causes the diameter of the medullary cavity to increase as the bone increases in length and width
callus ossification
during bone repair callus replaced by woven, cancellous bone through endochondral ossification
ossification
formation of bone by osteoblasts
function of collagen fibers in bone
gives bone flexible strength (like steel bars)
function of mineral matrix in bone
gives bone weight-bearing strength
three types of cartilage
hyaline - precursor of most bones in the body fibrocartilage elastic cartilage
lamellar bone
mature bone that is organized into thin sheets or layers approximately 3-7 micrometers thick called lamellae. collagen fibers lie parallel to one another but at an angle to the collagen fibers in adjacent lamellae
calcium homeostasis
minerals are deposited in the skeleton and withdrawn when they are needed for other purposes; depends on a balance btwn dietary intake, urinary and fecal loses, and exchanges btwn osseous tissue
callus formation
osteoclasts digest into the hematoma as bone stem cells differentiate into osteoblasts and chondrocytes
bone remodling
process of removing old bone and adding new bone
red marrow vs. yellow marrow
red - site of blood cell formation yellow - mostly adipose tissue
osteoclasts
responsible for the reabsorption or breakdown of bone. large cells that contain several nuclei.
lacunae
small cavities in the bone or cartilage that hold individual bones or cartilage cells
canaliculi
spaces occupied by the osteocyte cell processes
osteochondral progenitor cells
stems cells that can become osteoblasts or chondroblasts - located in inner layer of perichondrium and inner layers of connective tissue that covers bone (periosteium/endosteum)
trabeculae
supporting bundles of bony fibers in cancellous (spongy) bone; oriented along the lines of stress within the bone
intramembranous ossification
takes place in connective tissue membranes; begins when mesenchymal cells in the membrane become osteochondral progenitor cells
osteocyte
term for an osteoblast once it becomes surrounded by bone matrix
interstitial lamellae
the areas between osteons that are fragments of older osteons that have been partially destroyed during bone rebuilding or growth
epiphysis
the end of a long bone (knobby ends); develops from a center of ossification distinct from the diaphysis
hydroxyapatite
the inorganic calcium phosphate in bone
endochondral ossification
the most common bone formation process, which involves the replacement of hyaline cartilage (developed by mesenchyme) with bone, occurs in postcranial skeleton (except clavicle) and in bones of cranial base 1. mesenchyme condenses to form hyaline cartilage precursor 2. A bone collar forms around the circumference of cartilage model--this is periosteal bone 3. At primary center of ossification (forms first): cartilage matrix becomes calcified, erodes and forms spicules; then, bone forms on spicules 4. Ossification repeats in secondary centers of ossification in epiphyses
bone collar
the osteoblasts produce compact bone on the surface of the cartilage model.
diaphysis
the shaft of a long bone
appositiional growth
type of cartilage growth. chondroblasts in the perichondrium add new cartilage to the outside of the existing cartilage. chondroblasts lay down new matrix and add new chondrocytes to the outside of the tissue
chondrocyte
when cartilage surrounds a chondroblast, it becomes a _______, a rounded cell that occupies a space called a lacunae within the matrix