Bio 2140 Ch 6

sharpey's fibers

secure to bone matrix

the closure of the epiphyseal plate; this plate is a zone of hyaline cartilage between the epiphysis and diaphysis of a long bone. When the cartilage is replaced with bone and the plate closes (becoming an epiphyseal line), the bone has reached its maximum length

what indicates the full maturation of a long bone?

endochondral ossification

what process converts hyaline cartilage "bone" models into true bones (i.e., hyaline cartilage serves as a template for bone formation); forms most of skeleton

osteomalacia

when bones are poorly mineralized, osteoid is produces, but calcium salts are not adequately deposited making the bones frail and soft; caused by a deficiency in vitamin D

interstitial growth occurs when chondrocytes divide and form new matrix, thereby expanding the cartilage tissue from within. (Note: the word inter means between, and stitial means space; these are common roots for anatomical terms.)

when chondrocytes in lacunae divide and form new matrix, it leads to an expansion of the cartilage tissue from within. This process is called ________.

epiphyseal line

where bones lengthened before adulthood

epiphyseal plate; a layer of hyaline cartilage between the epiphyses and diaphysis of long bones

where does long bone lengthening occurs

osteogenic cell

also called osteoprogenitor cells, mitotically active stem cells in periosteum and endosteum, can transform into osteoblasts or bone lining cells

rickets

analogous disease in children; more severe than osteomalacia, bowed legs, deformities, etc.; also caused by deficiency in vitamin D

osteogenic layer of periosteum

anchoring point for tendons and ligaments

steps in endochondrial ossification

begins at primary ossification center in shaft; blood vessel infiltration of perichondrium converts it to periosteum -> underlying cells change to osteoblasts bone collar forms around diaphysis of cartilage model central cartilage in diaphysis calcifies, then develops cavities periosteal bud invades cavities -> formation of spongy bone diaphysis elongates & medullary cavity forms epiphyses ossify

greenstick

bone breaks incompletely, only one side of the shaft breaks, common in children

comminuted

bone fragments into three or more pieces

calcium and phosphate

bone is reservoir for what two elements...

periosteal cells

bone lining cells on external bone surface, help maintain matrix

endosteal cells

bone lining cells that line internal surfaces; help maintain matrix

osteoclast

bone-resorbing cell, derived from hematopoietic stem cells that become macrophages, when active rest in resorption bay and have ruffled edges (basically destroy bone)

proliferation (growth) zone

cartilage cells undergo mitosis; cartilage on diaphysis side of e plate, rapidly divide pushing e away from d --> lengthening

resting zone (quiescent)

cartilage on the epiphyseal side of epiphyseal plate, relatively inactive

ossification zone

chondrocyte deterioration leaves long spicules of calcified cartilage at epiphysis-diaphysis junction; spicules eroded by osteoclasts, covered w new bone by osteoblasts, finally replaced with spongy bone

spiral

common sports fracture resulting from a twisting force

irregular

complicated shapes; vertebrae & coxal bones

perforating or Volkmann's canals

connects periosteum to central canal

periosteum

covers external surfaces except joint surfaces; outer layer fibrous layer of dense irregular connective tissue (1st layer), osteogenic layer contains primitive stem cells called osteogenic cells (2nd layer)

short

cube-shaped bones (in wrist and ankle), sesamoid bones (within tendons, e.g. patella), vary with the individual

endosteum

delicate connective tissue membrane covering internal bone surface, covers trabeculae of spongy bone, lines canals that pass through compact bone, contains osteogenic cells that can transform into other cells

epiphyses

ends of bone-expanded; exterior is compact bone, interior is spongy bone, covered with hyaline cartilage

intramembraneous ossification

forms in frontal, parietal, temporal bones & clavicle, begins with fiber connective tissue created by mesenchymal cells, ossification centers appear, osteoid is secreted, woven bone and periosteum form, lamellar bone replaces woven bone & red marrow appears

red bone marrow

found within the trabecular cavities of spongy bone in both flat bones and some long bones, in medullary cavities and spongy bone of newborns; adults have little of this (heads of femurs only), yellow can convert if necessary

parathyroid hormone

functions to stimulate the activity of osteoclasts in bone tissue

canaliculli

hairlike canals that connect lacunae to each other and the central canal

blood cell formation; red bone marrow found within certain regions of spongy bone is the site of blood cell formation from the differentiation of hematopoietic stem cells

hematopoiesis is a term for what physiological process?

fibrocartilage

hick collagen fibers—has great tensile strength; menisci of knee; vertebral discs

lamellae

hollow tubes of bone matrix

spongy bone (cancellous or trabecular)

honeycomb of flat pieces of bone deep to compact called trabeculae

growth arrest lines

horizontal lines on bones; proof of illness- when bones stop growing so nutrients can help fight disease

medullary cavity

in adults, filled with yellow marrow, and during anemia, red marrow

long bones

include all limb bones except the patella, tarsals and carpals; longer than they are wide

vitamin D metabolites

intestinal absorption requires....

circumferential lamallae

located around entire shaft

osteoblast

matrix synthesizing cell responsible for bone growth, secrete unmineralized osteoid, includes collagen (90%) and calcium binding proteins, actively mitotic

osteocyte

mature bone cell that monitors and maintains the mineralized bone matrix; found in lacunae, act as stress sensors; respond to and communicate mechanical stimuli to osteoblasts and osteoclasts (cells that destroy bone) so that bone remodeling can occur

hyaline cartilage

most abundant type; provides support & flexibility; collagen fibers only, articular, costal, respiratory, nasal cartilage; also known as articular cartilage

functions of calcium

nerve impulse transmission, muscle contraction, blood coagulation, secretion by glands and nerve cells, cell division

bone remodeling

occurs continuously, but regulated by genetic factors & two control loops

calcium salts crystalize and fractures more easily

older bones become more brittle because....

hypertrophic zone

older cells enlarge; older chondrocytes closer to diaphysis and their lacunae enlarge and erode --> interconnecting spaces

canaliculi formation

osteoblasts secreting bone matrix maintain contact w each other & osteocytes via cell projections with gap junctions; when matrix hardens and cells are trapped canaliculi form -> allow communication and permit nutrients and wastes to be relayed from one osteocyte to another throughout the osteon

bone homeostasis

recycle 5-7% of bone mass each week; spongy bone replaced- every 3-4 years; compact bone replaced every 10 years; consists of bone remodeling and bone repair- both bone deposit and bone resorption, occurs at both periosteum and endosteum

hematopoietic tissue

red blood cells made in red marrow

osteocalcin

regulates bone formation, protects against obesity, glucose intolerance, diabetes

interstitial growth

requires presence of epiphyseal cartilage, epiphyseal plate maintains constant thickness (rate of cartilage growth on one side balance by bone replacement on other), concurrent remodeling of epiphyseal ends to maintain proportion; chondrocytes divide and secrete new matrix, expanding cartilage from within; result of 5 zones within cartilage

trabeculae

resist stress, irregularly arranged lamellae, osteocytes connected by canaliculli; no osteons, capillaries in endosteum supply nutrients

the five zones within cartilage (result of interstitial growth)

resting (quiescent) zone, proliferation (growth) zone, hypertrophic zone, calcification zone, and ossification (osteogenic) zone

central (haversian) canal

runs through the core of osteon, contains blood vessels and nerve fibers

elastic cartilage

similar to hyaline cartilage, but contains elastic fibers; external ear and epiglottis

lacunae

small cavities that contain osteocytes

bone functions

support, protection, movement; mineral and growth storage factor, blood cell formation, fat storage (triglycerides), & hormone production

calcification zone

surrounding cartilage matrix calcifies, chondrocytes die and deteriorate; cartilage cells die, matrix begins deteriorating, blood vessels invade cavities

the exceptional hardness of bone, which allows it to resist compression, is attributed to the presence of mineral salts called hydroxyapatites; the hydroxyapatites, mainly calcium phosphates, form the inorganic matrix of bone

the notable hardness of a bone is attributed to what...

osteoid

the organic part of the matrix

appositional growth

the process of bones increasing in width, occurs throughout life, osteoblasts beneath periosteum secrete bone matrix on external bone, osteoclasts remove bone on endosteal surface

diaphyses

the shaft; thick collar of compact bone; central medullary cavity filled with yellow bone marrow

interstitial lacanue

these fill gaps between osteons

flat

thin, flat, slighty curved; examples include sternum, scapula, ribs, and most skull bones

interstitial and appositional growth

two types of postnatal bone growth

hematoma formation, fibrocartilaginous callus formation, bony callus formation, and bone remodeling; use the pneumonic HFBR (His Femur Better Repair!)

what are the steps (in order) of a repair fracture?

osteoclasts out-pace osteoblasts due to low hormone production of the ovaries

what causes osteoporosis?

spongy bone of long bones (femur and humerus), diploe of flat bones, hip bone

where is hematopoietic tissue found?

adipose (fat)

yellow bone marrow within the medullary cavity is composed primarily of what?