Chapter 7 Flashcards
general components of the skeletal system (4)
bones, cartilage, ligaments, other connective tissues
ligaments vs. tendons
ligaments - connect bone to bone
tendons - connect muscle to bone
what is bone?
primary organs of the skeletal system
function of bone?
forms the rigid framework of the body and perform other functions
two types of bone
compact bone and spongy bone
compact bone
dense, cortical bone; 80% of bone mass
spongy bone
cancellous, trabecular bone; internal to compact bone; porous appearance; makes 20% of bone mass
cartilage
semirigid connective tissue that is more flexible than bone
two types of cartilage associated with the skeletal system?
hyaline cartilage and fibrocartilage
costal cartilage
hyaline cartilage that attaches ribs to sternum
articular cartilage
hyaline cartilage covering the end of the bone
epiphyseal plates
hyaline cartilage within growth plates
fibrocartilage
weight bearing cartilage that withstands compression
what does fibrocartilage form?
intervertebral discs, pubic symphysis, menisci
menisci
cartilage pads of knee joints
pubic symphysis
cartilage between pelvic bones
general functions of bone (4)
support and protection, levers for movement, hematopoiesis, storage of mineral/energy reserves
how do bones provide support and protection?
structural support; serves as framework for the whole body
bones also protect delicate tissues and organs from injury and trauma
how do bones serve as levers for movement?
skeletal muscle attached to bone contract and exert a pull on the skeleton, which then functions as a system of levers
what is hematopoiesis?
process of blood cell production
where does hematopoiesis occur?
within the red bone marrow connective tissue
what does the red bone marrow connective tissue contain that helps support blood cell synthesis?
stem cells that form blood cells and platelets
what minerals are stored within/released from bone?
calcium and phosphate
what is calcium?
essential mineral for body functions such as muscle contraction, blood clotting, and neurotransmitter release from nerve cells
what is phosphate?
structural component of ATP, other nucleotides, and phospholipids
long bones
length > width
examples of long bones
fingers/toes, femur, tibia, fibula
short bones
length = width
examples of short bones
carpals/tarsals, sesamoid bones (sesame seed-shaped bones along tendons of muscles)
flat bones
flat, thin slices that may have slight curve
examples of flat bones
roof of skull, scapulae, sternum, ribs
irregular bones
elaborate, complex shaped bones
examples of irregular bones
vertebrae/hip bones, ethmoid, sphenoid, maxilla
long bone regions (7)
diaphysis
medullary cavity
epiphysis (proximal/distal)
metaphysis
epiphysial plate/line
periosteum
endosteum
diaphysis
shaft of the long bone
medullary cavity
hollow space within the diaphysis
epiphysis
end(s) of the long bone
metaphysis
between diaphysis and epiphysis
epiphyseal plate
hyaline cartilage providing for lengthwise growth of bone
periosteum
bone covering; covers outer surface of bone except for articulated cartilage
endosteum
bone lining; thin layer of connective tissue containing osteoprogenitor cells, osteoblasts, and osteoclasts
what is the diaphysis composed of?
mostly compact bone, however a thin layer of spongy bone extends inward
what does the medullary cavity contain?
bone marrow
proximal vs. distal epiphysis
proximal - the end closest to the trunk
distal - the end farthest from the trunk
what is the epiphysis composed of?
thinner compact bone; more abundant in spongy bone and covered with articular cartilage
what function does the metaphysis provide?
transferring forces between the diaphysis and epiphysis
where is the epiphyseal plate located?
within the metaphysis
what does the epiphyseal plate become in adults?
epiphyseal line
(how? cartilage turns into bone, and can no longer grow in length)
what is the outer layer of the periosteum composed of?
dense irregular connective tissue
(blood vessels and nerves too, and is the site of tendon/ligament attachment)
what is the inner layer of the periosteum composed of?
(aka cellular layer) osteoprogenitor cells, osteoblasts, and osteoclasts
what growth type is the periosteum responsible for?
bone width
how is the periosteum anchored to bone?
by perforating fibers which run perpendicular to diaphysis
what does the endosteum cover?
all internal surfaces within the medullary cavity
anatomy of other bone classes? (not as complex as bone)
external surfaces are compact bone covered by periosteum; no medullary cavity
what is the interior of other bone classes aside from long bone?
spongy bone
(within flat bones? diploe)
is spongy bone vascular or avascular?
highly vascular; vessels enter from periosteum
small openings/holes in bones
nutrient foramens
function of nutrient foramens?
allows for arteries and veins to pass through, including nerves
bone marrow
softer connective tissue
function of red bone marrow
forms red blood cells
where can you find red bone marrow in children?
in medullary cavity + spongy bone of long bones
where can you find red bone marrow in adults?
select areas; skull, vertebrae, ribs, sternum, coxal bones, proximal epiphyses of humerus and femur
how is yellow bone marrow formed?
red bone marrow degenerates over life span; no longer functions in blood cell production
what is a characteristic of yellow bone marrow?
yellow bone marrow is fatty (composed of adipose)
osteoid
semisolid organic form of bone matrix
osteoprogenitor cells
stem cells derived from mesenchyme; divides and becomes “committed” cells, in which then they mature into osteoblasts
location of osteoprogenitor cells?
found in periosteum and endosteum
osteoblasts
synthesize + create osteoid that will eventually calcify; builds bone
what happens when osteoblasts get trapped in the matrix?
they become osteocytes
osteocytes
mature bone cells that maintain the bone matrix and detect bone stress
what happens if bone stress is detected?
osteoblasts are signaled, leading to formation of new bone
osteoclasts
large, multinuclear, phagocytotic cells that phagocytose bone; breaks down/resorbs bone
organic components of bone matrix?
osteoid - contains collagen proteins and semisolid ground substance of proteoglycans and glycoproteins
characteristics of organic components of the bone matrix
resistant to stretch - tensile strength; allows for some flexibility
inorganic components of bone matrix?
salt crystals made of calcium phosphate
what do salt crystals form when they interact with calcium hydroxide?
hydroxyapatite crystal
when crystals deposit around collagen fibers, what will it do to the matrix?
harden the matrix; make it more rigid
bone formation
occurs when osteoblasts secrete osteoid
what occurs during bone formation?
- osteoblasts secrete osteoid
- calcification occurs
- hydroxyapatite crystals are deposited into bone matrix
what initiates calcification in bone formation?
when calcium and phosphate ion concentration is high, thus it “leaks” out of the solution
requirements of bone formation
vitamin D, vitamin C, calcium, phosphate
vitamin D in bone formation
better calcium absorption
vitamin C in bone formation
collagen production
calcium and phosphate in bone formation
calcification
bone resorption
osteoclasts release substances that destroy bone matrix; proteolyotic enzymes released from lysosomes
osteon
small cyndrical structure; basic structural and functional unit of mature compact bone
osteon will always be parallel to what?
to the diaphysis
components of osteon
central canal
concentric lamellae
osteocytes
canaliculi
central canal
has blood vessels and nerves
concentric lamellae
surrounding rings of central canal; orientation of collagen fibers, provides strength and resilience
osteocytes
mature bone cells found in lacunae; maintain the bone matrix
canaliculi
interconnecting channels between lacuna; connect lacuna to central canal
trabeculae
lattice pattern of bone; bone marrow is in spaces, helps bone resist stress
hyaline cartilage histology
cells within matrix of protein fibers; gel-like ground substance of proteoglycans
characteristics of hyaline cartilage
- resilient; flexible
- avascular
- high water %
- no nerves
- compressible; shock-absorbing
chondroblasts
produce cartilage matrix
what happens when chondroblasts get trapped in the matrix?
they mature into chondrocytes
two methods of cartilage growth
interstitial and appositional
interstitial cartilage growth
increase in length that occurs within internal regions of cartilage
1st step of interstitial growth
chondrocytes housed within lacunae are stimulated to undergo mitosis
2nd step of interstitial growth
(after cell division) two cells occupy single lacuna; now called chondroblasts
3rd step of interstitial growth
chondroblasts synthesize + secrete cartilage matrix, making them push apart - each cell resides in their own lacuna; now called chondrocytes
4th (final) step of interstitial growth
cartilage continues to grow within internal regions as chondrocytes produce more matrix
appositional growth
increase in width along cartilage’s outside edge
1st step of appositional growth
stem cells within perichondrium begin to divide (perichondrium contains mesenchymal cells too)
2nd step of appositional growth
new undifferentiated stem cells + committed cells (chondroblasts) form; these chondroblasts are located in the outside of old cartilage and produce/secrete cartilage matrix
3rd (final) step of appositional growth
chondroblasts push apart and turn into chondrocytes (result of matrix formation), and cartilage continues to grow on periphery as more matrix is produced
ossification
(a.k.a. osteogenesis) formation and development of bone connective tissue
where does ossification begin?
in the embryo; continues throughout childhood-adolescence
what happens to the skeleton during the 8-12wks of embryonic development?
skeleton begins forming thickened condensations of mesenchyme (intramembranous) or hyaline cartilage model of bone (endochondral)
intramembranous ossification
bone growth within a membrane
what does intramembranous ossification produce?
flat bones of skull, some of the facial bones, central part of clavicle
when does intramembranous ossification begin?
when mesenchyme becomes thickened/condensed w/ dense supply of blood capillaries
step 1/4 of intramembranous ossification
ossification centers form within thickened regions of mesenchyme beginning @ 8th week of development
step 1/4 of intramembranous ossification
- ossification centers form within thickened regions of mesenchyme beginning @ 8th week of development
- some thickened/condensed mesenchyme divide
- committed cells turn into osteoprogenitor cells; some become osteoblasts and secrete osteoid
- ossification centers develop within thickened mesenchyme as osteoblast # increases
step 2/4 of intramembranous ossification
- osteoid undergoes calcification
- calcium salts are deposited onto osteoid then crystalize
- calcification entraps osteoblasts within lacunae in matrix; trapped cells become osteocytes
step 3/4 of intramembranous ossification
- woven bone + surrounding periosteum form
- woven bone = immature/disorganized bone connective tissue (primary bone)
- later replaced by lamellar bone (secondary bone)
- mesenchymal cells grow and develop to produce additional osteoblasts; new blood vessels branch from here
- trabeculae is calcified and becomes spongy bone
step 4/4 of intramembranous ossification
- lamellar bone replaces woven bone; compact bone and spongy bone are formed
- lamellar bone replaces trabeculae of woven bone
- external: spaces between trabeculae are filled; bone becomes compact
- internal: spaces between trabeculae are modified; bone becomes spongy
endochondral ossification
begins with hyaline cartilage model + produces most bones of the skeleton
what does endochondral ossification produce?
upper/lower limbs, pelvis, vertebrae, ends of clavicle; long bone development
step 1/6 of endochondral ossification
- fetal hyaline cartilage model develops during 8-12ws development
- chondroblasts secrete cartilage, forming hyaline cartilage
- chondrocytes are trapped within lacunae, perichondrium surrounds cartilage
