Skeletal System Flashcards
what is the primary function of bone and cartilage
support and locomotion
what is the secondary function of bone and cartilage
protection, mineral storage, and hemopoiesis
what are bone and cartilage derived from
mesenchymal cells
describe bone vs cartilage
bone- rigid
cartilage- semi-rigid
what are the relative strength of bone and cartilage due to
properties of ground substance and extracellular fibers
what is cartilage a precursor for
bone
explain cartilage formation
-begins with stellate mesenchymal cells that differentiate into chondroblasts that grow and make ground substance and fibrous ECM trapping chondroblasts in lacunae
- further mitotic divisions produce mature chondrocytes referred to as isogenous groups separated by ECM
what is the difference between territorial matrix vs interterritorial matrix
territorial matrix is ECM inside the cell
interterritorial matrix is ECM between cells
what surrounds cartilage
perichondrium
what makes up perichondrium
dense CT containing fibroblasts, collagen and immature chondroblasts
what is interstitial growth
new cartilage forms within mass and chondrocytes retain ability to divide
what is apositional growth
new cartilage forms at surface of pre-existing cartilage; more common (occurs at periphery)
what are new chondrocytes derived from
mesenchymal cells of inner perichondrium - differentiate first into chondroblasts
where are more mature chondrcytes located
center of cartilage mass
does cartilage have blood vessles
no it is avascular
how does exchange of metabolites in cartilage occur
via diffusion through ground substance
where does thick cartilage contain blood vessels
in secondary cartilage canals
describe the ECM of amorphous ground substance in cartilage
-contains collagen
- 60-80% water bound to proteoglycans such as hyaluronic acid, chondroitin sulfate, and heparin sulfate
what gives matrix flexibility and incompressibility
water and proteoglycans in the matrix
is hyaluronic sulfated
NO
what is the most common glycoprotein
chonronectin
what are the 3 types of cartilage
-hyaline
- fibrocartilage
- elastic
where is hyaline cartilage found
articular surfaces, growth plates, nasal septum, costal cartilages, tracheal and bronchial rings
what is the precursor for bone in most of skeleton
hyaline cartilage
what is hylaine cartilage characterized by
aggregates of chondrocytes in amorphous matric of ground substance, reinforced with type 2 collagen fibers
what makes up fibrocartilage
alternating layers of hyaline cartilage and dense CT (contains type 1 and 2 collagen) , less cellular than other cartilage types
what does fibrocartilage lack
periochondrium
where is fibrocartilage found
knee, mandible (TMJ), shoulder, sternum - ligaments, tendons, joint capsules, pubic symphsis
what makes up elastic cartilage
type 2 collagen with large numbers of elastic fibers in ECM
where is elastic cartilage found
external ear, auditory and eustacian canals, epiglottis and larynx
why is repair in cartilage limited and what does repair result in
repair requires blood flow, results in production of dense CT (fibrosis)
what does the invasion of the repair site by blood vessels result in
death of chondrocytes and formation of bone
which cartilage calcifies with age and how
hyaline, via deposition of calcium phosphate crystals within matrix that is eventually replaced with bone
what is bone and how does it get its function
specialized support tissue
- extracellular components are mineralized giving bone rigidity and strength
what are the main forms of bone
woven and lamellar
describe woven bone
immature form characterized by random orientation of collagen fibers
what is lamellar bone
woven bone gets remodeled into lamellar bone
- contains concentric layers called circumferential lamellae with parallel collagen fibers
describe the types of lamellar bone and where can each be found
can be dense and compact (cortex of long bones) or cancellous ( spongy at the ends of bone)
what does cancellous bone contain
network of thin, bony trabeculae and open spaces
what are the open spaces in cancellous bone
marrow cavity
what is another word for trabeculae
spicules
where are long bones found
in limbs
explain the diaphysis of long bones
the shaft
- made of dense compact bone in cortex and spongy cancellous bone in medullary cavity (marrow)
what does the marrow contain
red marrow or yellow marrow
where are epiphyses located and what are they made of
ends of bones
-made of spongy, cancellous bone, covered with hyaline articular cartilage
what is the metaphysis
flared region between epiphysis and diaphysis
what does the metaphysis contain
epiphyseal plate of long bones
what does the periosteum cover
external surface of bone
what is the periosteum made of
layer of fibrous connective tissue containing fibroblasts and osteoprogenitor cells
what does the endosteum cover
internal marrow cavity
what are sharpey’s fibers and where are they located
parallel bundles of collagen fibers, extend from periosteum or muscle tendon and insert into superficial layers of bone
what is the function of sharpeys fibers
provide anchorage and support of periosteum to bone
what are osteoprogenitor cells and where are they found
resting mesenchymal cells, reside in periosteum and endosteum
what can osteoprogenitor cells differentiate into
osteoblasts and osteocytes
describe osteoblasts
roughly polygonal, mesenchymal cells derived from osteoprogenitor cells
- basophilic due to synthesis of large amount of protein and proteoglycans
what are osteoblasts responsible for
- synthesis of ECM and collagen (osteoid)
- calcification of matrix via secretion of matrix vesicles
what is osteoid
ECM and collagen, similar to cartilgae later mineralized to form new bone
what do matrix vesicles contain and what do they do
alkaline phosphatase, bud off osteoblasts into matrix causing precipitation of mineral salts (Ca and PO4)
what do osteoblasts mature into and where
mature into osteocytes within lacunae after matrix mineralizes
describe osteoclasts
large multinucleate cells, probably derived from monocyte macrophage lineage, phagocytic
what do osteoclasts do
resorption and remodeling of bone
where are osteoclasts found
on endosteal/ periosteal surface in depressions called howship’s lacunae or resporption bays
how do osteoclasts function in Ca homeostasis
by producing organic acids and lysozymes that digest bone- secreted into ECS by ruffled border
what is the ruffled border
modified folded plasma membrane containing microvilli like structures
what hormones regulate calcium homeostasis
parathormone and calcitonin
what secretes parathormone
parathyroid gland
what does the parathormone do
stimulates osteoclast activity -> bone resorption
- increase blood Ca levels
- decrease renal excretion by kidneys
what secretes calcitonin
thyroid gland
what does calcitonin do
-stimulates osteoblast activity and inhibits osteoclasts -> bone deposition
- decreased blood Ca levels
what secretes somatotropin
pituitary
what does somatotropin do
-stimulates growth, epiphyseal cartilage and bone
- decreases blood Ca
what does oversecretion of somatotropin lead to
gigantism or acromegaly
what does undersecretion of somatotropin lead to
pituitary dwarfism
what is mature compact bone made of
70% inorganic salts and 30% organic matrix
what is most of the organic matrix in compact bone made of and what makes it
type 1 collagen made by osteoblasts
what are the GAGs in mature compact bone
mostly hyaluronic acid and chondroitin sulfate, also has keratin sulfate
what are the non-collagenous molecules in the bone matrix
-osteocalcin
- osteonectin
- sialoproteins
what does osteocalcin do
binds intracellular Ca during mineralization
what does osteonectin do
bridges/binds collagen and minerals
what do sialoproteins contain
rich in sialic acid; concentrated from plasma
what is the mineralized component of bone formed by
inorganic salts
-primarily Ca and P in the form of hydroxyapatite crystals
what does bone have an affinity for
heavy metals (Pb and Hg) and radioactive isotopes
