Skeletal System: Bones and Bone Tissue
estrogen
a clss of female reproductive hormones that aids in bone growth
periosteum
a connective tissue membrane covering the outer surface of a bone
interstitial growth
chondrocytes in the center of the tissue divide and add more matrix in-between the existing cells
concentric lamellae
circular layers of bone matrix that surround the central canal
long, flat, short, irregular
classification of bone shape
epiphysis
part of a long bone that develops from a center of ossification distinct from that of the diaphysis
diaphysis
shaft composed primarily of compact bone, but it can also contain some spongy bone
zone of hypertrophy
the chondrocytes produced in the zone of proliferation mature and enlarge in this zone
articular cartilage
the end of a long bone covered with hyaline cartilage
centers of ossification
the locations in the membrane where ossification begins
collagen and proteoglycan
the matrix contains ___ and ___
bone remodeling
the process of removing old bone and adding new bone
osteoblasts, osteocytes, osteoclasts
three types of bone cells
hyaline cartilage, fibrocartilage, elastic cartilage
three types of cartilage
-blast
"seed" or "bud"
osteoclasts
- Bone-destroying cells - cells that perform reabsorption or breakdown
osteomalacia
- adult rickets - a softening of the bones due to calcium depletion.
interstitial lamellae
- between osteons - remnants of concentric or circumferential lamellae that were partially removed during bone remodeling
osteoblasts
- bone-forming cells - produces collagen and proteoglycans - also releases matrix vesicles
epiphyseal plate
- growth plate - located between the epiphysis and the diaphysis - where growth in the bone length occurs
long bones
- longer than they are wide - traditional model for overall bone structure
Type 1 osteogenesis imperfecta
- mildest and most common form of OI - caused by too little formation of normal type 1 collagen (collagen-deficiency)
circumferential lamellae
- outer surface of compact bone - thin plates that extend around the bone
perichondrium
- protective connective tissue sheath that covers most cartilage - double-layered outer layer of dense irregular connective tissue containing fibroblasts
osteoprogeterin (OPG)
- secreted by osteoblasts and other cells - inhibits osteoclast production by binding to RANKL
calcitonin
- secreted from thyroid gland when blood calcium ion levels are too high - inhibits osteoclast activity by binding to receptors on the osteoclasts
perforating fibers
- sharpey fibers - bundles of collagen fibers - strengthen the attachment of the tendons or ligaments to the bone
fontanels
- soft spots - larger, membrane-covered spaces between the developing skull bones that have not yet been ossified
ruffled border
- the osteoclast cell membrane then further differentiates into a highly folded form - reabsorption-specific area of the membrane
scurvy
- vitamin C deficiency - marked by ulceration and hemorrhage in almost any area of the body because normal collagen synthesis is not occurring in connective tissues
Gigantism
Abnormally increased body size due to excessive growth at the epiphyseal plates
Dwarfism
Abnormally small body size due to improper growth at the epiphyseal plates
greenstick fracture
An incomplete fracture on the convex side of the curve of the bone
every 10 years
BMU activity renews the entire skeleton
Osteogenesis imperfecta
Brittle bones that fracture easily due to insufficient or abnormal collagen
Rickets
Growth retardation due to nutritional deficiencies in minerals (Ca2+) or vitamin D; results in bones that are soft, weak, and easily broken
closed fracture
If the skin is not perforated
receptor activator of nuclear factor kappaB ligand
RANKL meaning
osteoporosis
Reduction in overall quantity of bone tissue
osteomalacia
Softening of adult bones due to calcium depletion; often caused by vitamin D deficiency
testosterone
a male reproductive hormone that aids in bone growth
callus
a mass of tissue that forms at a fracture site and connects the broken ends of the bone
autosomal dominant
a mutation in only one copy of the gene will cause OI, even if the other gene is normal
lacuna
a rounded cell that occupies a space within the matrix
endosteum
a single cell layer of connective tissue that lines th internal surfaces of all cavities within bones
secondary ossification centers
additional sites of ossification that are created in the epiphyses by osteoblasts
sinuses
air-filled spaces of some flat and irregular bones of the skull which are lined by mucous membranes
osteocyte
an osteoblast that has secreted enough bone matrix to become surrounded by it
spongy bone
appears porous, has less bone matrix and more space
approximately 6 months
average life span of a BMU
osteomyelitis, tuberculosis
bacterial infections
intramembranous ossification
begins approximately the eighth week of embryonic development and is completed by approximately 2 years of age
perforating canals (volkmann canals)
blood vessels from the periosteum or medullary cavity enter the bone through ___
appositional growth
chondroblasts in the perichondrium add new cartilage to the outside edge of the existing cartilage
osteomyelitis
bone inflammation often due to a bacterial infection that may lead to complete destruction of the bone
intramembranous ossification and endochondral ossification
bone patterns during fetal development
1. Hematoma formation 2. callus formation 3. callus ossification 4. Bone remodeling
bone repair steps (4)
bone remodeling
bone that becomes old is replaced with new bone
brittle
bone without collagen will be ___
flexible
bone without mineral will be ___
osteogenesis imperfecta
brittle bone disorder
chondrocyte
by the time the matrix has surrounded a chondroblast, the cell has differentiated into a ___
hyaline cartilage
cartilage mostly associated with bone
osteomalacia, osteoporosis
decalcification
connective tissue
developed embryologically from mesenchymal cells
medullary cavity
diaphyses of long bones tend to have a hollow center called ___
growth hormone
from the anterior pituitary increases general tissue growth, including overall bone growth, by stimulating interstitial cartilage growth and appositional bone growth
osteon or haversian system
functional unit of a long bone
1. Body support 2. Organ protection 3. Body movement 4. Mineral storage 5. Blood cell production
functions of skeletal system (5)
rickets
disease resulting from reduced mineralization of the bone matrix
incomplete fracture
does not extend completely across the bone
RANKL
expressed on the surface of the osteoblasts
nutrition, hormones
factors affecting bone growth
woven bone
first type of bone that osteoblasts form during ossification
ossification
formation of new bone by osteoblasts
external callus
forms a collar around the opposing ends of the bone fragments
internal callus
forms between the ends of the broken bone, as well as in the marrow cavity if the fracture occurs in the diaphysis of a long bone
gigantism, dwarfism, osteogenesis imperfecta, rickets
growth and developmental disorders
compact bone
has more matrix and is denser with fewer pores
irregular bones
have shapes that do not readily fit into the other three categories
creatingnew cartilage in the epiphyseal plate
how do long bones grow?
articular cartilage
hyaline cartilage that covers the ends of bones where they come together to form joints, has no perichondrium, blood vessels, or nerves
central canal
in a cross section, an osteon resembles a circular target (bull's eye)
Hairline fractures
incomplete fractures in which the two sections of bone do not separate
reproductive hormones
initially stimulate bone growth, which accounts for the burst of growth at puberty when production of these hormones increases.
hydroxyapatite
inorganic material that consists primarily of a calcium phosphate crystal
trabeculae
interconnecting rods or plates of bone
lamellae
lamellar bone sheets
hematoma
localized mass of blood released from blood vessels but confined within an organ or a space
Parathyroid hormone (PTH)
major regulator of blood calcium ion levels
proteoglycan
makes cartilage resilient by trapping water
lamellar bone
mature bone
35% organic, 65% inorganic
mature bone matrix material percentage ratio
increases osteoblast activity
mechanical stress applied to bone
yellow marrow
mostly adipose tissue
zone of resting cartilage
nearest the epiphysis and contains slowly dividing chondrocytes
vitamin C
necessary for collagen synthesis by osteoblasts
vitamin D
necessary for the normal absorption of calcium from the intestines
canaliculi
no blood vessels penetrate the trabeculae, so osteocytes must obtain nutrients through their ___
-blast to -cyte
once the immature cell has grown and differentiated into its mature form (suffix change)
Staphylococcus aureus
organism that causes osteomyelitis
epiphyseal line
ossified epiphyseal plate
diaphysis
primary ossification center
hyalin cartilage chondroblast
produces a matrix surrounding themselves
collagen
provides cartilage strength
flat bones
relatively thin shap, flattened shape and are usually curved
decreases osteoblast activity
removal of mechanical stress
thyroid hormone
required for normal growth of all tissues, including cartilage; therefore, a decrease in this hormone can result in a smaller individual
collagen and mineral components
responsible for the major functional characteristics of bone
short bones
round or nearly cube-shaped
red marrow
site of blood cell formation
bones, cartilage, tendons, ligaments
skeletal system components (4)
complicated fracture
soft tissues around a closed fracture are damaged
stem cells
some mesenchymal cells become ___
canaliculi
spaces occupied by osteocyte cell extensions
lacunae
spaces without matrix but occupied by the osteocyte cell bodies
endochondrial ossification
stars at approximately the eighth week of embryonic development, but this process might not begin in other cartilage until as late as 18-20 years of age
osteochondral progenitor cells
stem cells that can become osteoblasts or chondroblasts
tendons
strong bands of connective tissue that attaches skeletal muscles to bones
ligaments
strong bands of fibrous connective tissue that hold bones together
basic multicellular unit (BMU)
temporary assembly of osteoclasts and osteoblasts that travels through or across the surface of bone, removing old bone matrix and replacing it with new bone matrix
1. A hollow cylinder is lighter in weight than a solid rod 2. a hollow cylinder with the same height, weight, and composition as a solid rod, but with a greater diameter, can support much more without bending
two mechanical advantages of a long bone structure
appositional growth and interstitial growth
two types of cartilage growth
tuberculosis
typically, a lung bacterium that can also affect bone
zone of calcification
very thin and contains hypertrophied chondrocytes and calcified cartilage matrix
open fracture
when an open wound extends to the site of the fracture or when a fragment of bone protrudes through the skin
zone of proliferation
where chondrocytes produce new cartilage through interstitial cartilage growth
on the cell surfaces of osteoclast precursor stem cells
where to find RANK
inner layer of the perichondrium and in layers of connective tissue that cover bone
where you can find osteochondral progenitor