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?