Cartilage and Bone Flashcards
What are the 3 types of cartilage?
hyaline, elastic, fibrocartilage
What is the most abundant type of cartilage?
hyaline
Where is hyaline found?
in embryo as the early skeleton, articular surfaces of joints, epiphyseal plates, respiratory system
Where is elastic cartilage found?
in auricle, epiglottis, auditory tubes
Does fibrocartilage contain a perichondrium?
NO
What do chondrocytes produce in hyaline cartilage?
type 2 collagen
What do chondrocytes produce in fibrocartilage?
type 1 collagen
What is the strongest type of cartilage?
fibrocartilage
Where is fibrocartilage found?
intervertebral discs, joints, menisci, and symphosis pubis
What type of collagen is important for bone development?
collagen type 2 produced by chondrocytes
The extracellular matrix includes what types of collagen in smaller quantities?
9,10,11
What is hyaline composed of?
chondrocytes contained within lacunae and surrounded by glassy appearing extracellular matrix
What is the perichondrium?
- dense irregular connective tissue that contain chondroblasts
- surrounds hyaline and elastic cartilage
What do chondrocytes produce in elastic cartilage?
elastic fibers and type 2 collagen
What makes up elastic cartilage?
chondrocytes, lacunae; possess a perichondrium
Where is elastic cartilage found?
ears, epiglodys
What does hyaline cartilage form?
the precursor skeleton for the formation of bone
What is considered the “ground substance” in cartilage?
glycosaminoglycans + glycoproteins + PG
What are the 2 types of growth in cartilage?
appositional and interstitial
What is appositional growth?
growth to the cartilage surface using chondroblasts that secerete matrix to grow cartilage
What is interstitial growth?
growth via division on chondrocytes that secrete matrix
In what direction does cartilage grow in appositional and interstitial growth?
- appositional: grows out
- interstitial: grows up
What is compact bone?
- diaphysis (shaft) of long bones and outer surface of flat bones
- made of osteons
What is spongy bone?
- interior of long bones and diploe of flat bones
- trabeculae + NO osteons
What are the functions of bone?
- structural support
- anchoring of muscle
- protection of underlying organs
- storage site for Ca
What does the bone matrix contain?
- type 1 collagen
- glycoaminoglycans
- glycoproteins
- Ca phosphate
What does it mean if the matrix is mineralized (calcified)?
made up of Ca phosphate (hydroxyapatite crystals)
What cells are contained in the lacunae in the matrix?
osteocytes
What is the epiphyseal line?
plate of compact bone that is formed by replacing the final hyaline cartilage during growth
What is an epiphyses and what does it contain?
- the end of long bones
- red marrow: production of red blood cells
What is the medullary cavity?
site of marrow
What is the periosteum?
double layer of dense irregular connective tissue covering bone
What is contained in bone marrow?
- red: RBC
- yellow: adipose cells (in adults only)
What is the blood supply like in bone?
highly vascularized which leads to calcification
What is the diaphysis?
- shaft of long bones
- made up of compact bone
- contains medullary cavity: site of bone marrow
What are the layers of the diaphysis?
- periosteum with an outer dense connective layer and an inner cellular layer of periosteal
- bone with outer circumferential lamellae and Haversian systems with canals/lamellae
- inner circumferential lamellae
- either red or yellow bone marrow
What is the basic unit of compact bone?
Haversian (osteon) system
What is the Haversian canal and what does it contain?
- canal that runs through middle of the Haversian system
- contains vessels and nerve fibers
- runs parallel to axis of bone
What are Volkmanns’ (perforating) canals?
perpendicular channels that provide channels for blood vessels and nerve fibers to connect adjacent Haversian systems
How can you tell the difference between periosteum and endosteum?
- periosteum will be beside muscle
- endosteum will be beside bone marrow
As the bone matures, what system becomes more organized?
Haversian System
What are lamellae?
rings of thin bone
What results in areas of partial lamelae?
as bone remodels and parts of the Haversian system is reabsorbed and replaced by new systems
What makes up the bulk of the mature bone?
osteons
What are the cells within the haversian canal?
- osteoprogenitor cells
- osteoblasts
- osteoclasts (if bone is remodeling)
How is the lamellar pattern created?
from osteocytes that are in the lacunae
Osteocytes posses processes contained where?
canaliculi
The osteocyte processes help to what?
- cells communicate
- nutrients diffuse
What junction do the processes contain?
gap junctions
What are canaliculi?
small tunnels connecting lacunae to allow osteocytes to share a transport system
What is a mature bone cell?
osteocyte
What are the precursor/immature cells for osteocytes?
osteoblasts
What do osteoblasts secrete for the bone matrix?
collagen 1 and proteoglycans
What are osteocytes responsible for?
- maintaining bone matrix
- limited reabsorption to maintain blood Ca
What is the major resorptive cell in bone?
osteoclasts
Osteoclasts are active in what?
bone remodeling and the uptake of Ca
What hormone stimulates osteoclasts?
parathyroid -> increases blood Ca
What inhibits osteooclasts?
Calcitonin -> decreases blood Ca
What is Howship’s lacunae?
where osteoclasts rest and posses a ruffled border
What is released into the lacunae?
- lysosomes that release hydrolytic enzymes to digest the matrix
- organic acids that lower pH and aids in decalcification
What bone remodels faster?
bones under constant stress
What happens in intramembranous bone formation?
- mesenchymal cells differentiate into osteoblasts
- osteoblasts secrete bony matrix (osteoid)-> creates bony spicules
- bony spicules become interconnected and form trabeculae
What happens in endochondral bone formation?
- hyaline cartilage is developed
- cartilage model increases in size by appositional and interstitial growth
- bony collar is developed around the middle of the diaphysis and osteoblasts are formed
- chondrocytes die
What is the order of zones (top to bottom)?
- zone of ossification: acidophilic because new bone is forming
- zone of calcification: basophilic because cartilage calcified
- zone of hypertrophy: chondrocytes grow in size
- zone of proliferation: isogenous groups formed
- zone of reserve: no isogenous groups
What causes calcification of the cartilaginous matrix?
when hypertrophic cells secrete alkaline phosphate
What is the internal bone?
spongy bone
Spongy bone is composed of what?
meshed network of trabeculae
Where does spongy bone line up?
along lines of stress and help provide strength
What does spongy bone consist of?
osteocytes connected with canalicili and surrounded by lamellae
When is the process of endochondral ossification?
- blood vessels enter the perichondrium
- membrane becomes vascularized
- nutrients allowed to reach the mesenchymal cells surrounding hyaline cartilage which differentiate into osteoblasts
- osteoblasts surround diaphysis which mineralizes and becomes boney collar
What happens when chondrocytes lack nutrition?
they die and gaps are created in the calcified cartilage
Osteoclasts break down what cartilage?
calcified
Once the cartilage is calcified, what do osteoclasts allow?
arteries, veins, lymphatics, nerve fibers, red marrow elements, and osteoblasts to form periosteal bud
Osteoblasts secrete what to surround the remaining hyaline cartilage?
osteoid, which leads to development of trabeculae
What is the last stage in endochondrial ossification?
the appearance of secondary ossification centers
What are the steps to fracture healing?
- hematoma formation
- fibrocartilaginous callus forms
- boney callus forms
- bone remodeling
What are the 4 cells involed in bone formation and remodeling?
- osteoblasts
- osteocytes
- osteoclasts
- osteoprogenitor cells
