Highison: Cartilage and Bone Flashcards
Functions of cartilage
Provides shape and flexibility
Shock absorber
Facilitates smooth movements of joints
What does cartilage consist of?
cells
ground substance
fibers
What surrounds cartilage?
dense CT layer, called the perichondrium
Does cartilage contain vessels or nerves?
No
Cartilage is nourished by (blank) of gases and nutrients through the ECM. Cartilage is rather (blank) in the adult humans, but it is very important during development because of its firmness and its ability to grow (blank). In developing humans, most of the bones of the skeleton are preceded by a temporary cartilage “model”. Cartilage is also formed very early during the repair of (blank).
diffusion; rare; rapidly; bone fractures
In adult, cartilage has rather (blank) access to nutrients. Water content decreases and small cavities arise in the matrix, which often leads to the (blank) of the cartilage further compromising nutrition. (blank) cannot keep pace with the repair requirements after acute damage to hyaline or articular cartilage. If these cartilages are injured after the period of active growth, the defects are usually filled by (blank) or fibrous cartilage. The extracellular matrix of these “repair tissues” is only poorly integrated with the matrix of the damaged cartilage
poor; calcification; chondrocytes; connective tissue
Fortunately, cartilage is rather well suited for (blank) - the metabolism of the chondrocytes is rather slow, the antigenic power of cartilage is low, and it is difficult, if not impossible, for antibodies or cells of the immune system to diffuse through the (blank) into the cartilage
transplantation; matrix
Where is hyaline cartilage located?
fetal skeletal tissue epiphyseal plates articular surface of synovial joints costal cartilages of the rib cage cartilages of nasal cavity larynx rings of the trachea and plates in the bronchi
Hyaline cartilage is resistant to (blank), provides cushioning, has smooth and low-friction surface for (blank), provides structural support in (blank), forms foundation for development of (blank) and further endochondral bone formation and bone growth.
compression; joints; respiratory system; fetal skeleton
Does hyaline cartilage have a perichondrium?
Yes, except articular cartilage and epiphyseal plates
Does hyaline cartilage undergo calcification?
Yes
Cell types present in hyaline cartilage
chondroblasts; chondrocytes
Characteristic features of extracellular matrix of hyaline cartilage
type II collagen fibrils, aggrecan
Location of elastic cartilage
pinna of external ear
external acoustic meatus
auditory tube
cartilages of larynx
Function of elastic cartilage
provides flexible support
Does elastic cartilage have a perichondrium?
Yes
Does elastic cartilage undergo calcification?
No
Cell types present in elastic cartilage?
chondroblasts; chondrocytes
Characteristic features of extracellular matrix of elastic cartilage
type II collagen fibrils and elastic fibers, aggrecan
Location of fibrocartilage
intervertebral disks symphysis pubis articular disks (sternoclavicular) menisci (knee joint) triangular fibrocartilage complex (wrist joint) insertion of tendons
Function of fibrocartilage
resists deformation under stress
Does fibrocartilage have a perichondrium?
Noo
Does fibrocartilage undergo calcification?
Yes
Cell types present in fibrocartilage
chondrocytes; fibroblasts
Characteristic features of extracellular matrix of fibrocartilage
type II AND I collagen fibers, versican (proteoglycan secreted by fibroblasts)
Hyaline cartilage is highly (blank); components of hyaline matrix are not evenly (blank); hyaline cartilage provides a model for developing (blank) in the fetus
hydrated; distributed; skeleton
What is one way to distinguish hyaline and elastic cartilage from fibrocartilage?
Fibrocartilage has Type I collagen fibers, while the others do not
Hyaline cartilage is highly (blank) which allows for its compressibility. Is the hyaline matrix evenly distributed? Why is hyaline cartilage useful?
hydrated; no; provides a model for developing skeleton in the fetus
Grouping of cells in hyaline cartilage that represents the mitosis of chondrocytes
isogenous groups
CT sheath on the outside of cartilage - consisting of an outer fibrous layer and an inner chondrogenic layer made up of chondroblasts.
perichondrium
How can you distinguish territorial vs inter-territorial matrices in hyaline cartilage?
territorial matrices tend to be darker, while interterritorial cells tend to be lighter
Cartilage can grow interstitially or appositionally. What does this mean?
Interstitial growth is on the inside, or within the cartilage, and is represented by isogenous groups.
Apositional growth occurs on the outside, toward the perichondrium, and increases the girth of the cartilage.
A subtype of hyaline cartilage that transforms the articulating ends of the bones into lubricated, wear-proof, slightly compressible surfaces, that exhibit very little friction.
articular cartilage
Is articular cartilage surrounded by a perichondrium? Is it well vascularized?
no; poorly vascularized
Four zones that articular cartilage is divided into
- tangential layer
- transitional zone
- radial zone
- calcified cartilage layer
Layer furthest from the bone; chondrocytes are rather small and flattened to the surface. Collagen fibers run parallel to the surface of the cartilage.
tangential layer
Layer in which chondrocytes slightly larger, round and occur both singly and in isogenous groups. Collagen fibers take an oblique course through the matrix of the transitional zone
transitional zone
In this zone, fairly large chondrocytes form radial columns oriented perpendicular to the articulating surface. The course of the collagen fibers follows the orientation of the chondrocyte columns.
radial zone
This zone rests on the underlying cortex of the bone and stains slightly darker than the matrix of the other layers.
calicified cartilage layer
Two fibers notable in elastic cartilage slide
elastic fibers that stain with Verhoeff stain and type II collagen fibers
Chondrocytes in elastic cartilage retain a fairly high mitotic rate throughout life. As a result, there are more cells than you would see in (blank) cartilage.
hyaline
Does elastic cartilage calcify?
No
A form of connective tissue transition between dense connective tissue and hyaline cartilage
fibrocartilage
Which type of collagen fiber is dominant in fibrous cartilage?
type I and type II
Is there a perichondrium in fibrocartilage?
no
Fibrocartilage contains parallel columns of (blank)
chondrocytes
Origin of cartilage
mesenchymal cells
What do chondroblasts give rise to? What do fibroblasts give rise to?
cartilage proper; perichondrium
Two layers of perichondrium
inner chondrogenic layer
outer fibrous layer
Cartilage exhibits two types of growth. What are they and which types of cartilage do they apply to?
appositional growth –> hyaline and elastic cartilage
interstitial growth –> all cartilages
In appositional growth, chondrogenic cells from inner layer of perichondrium become (blank).
chondroblasts
In newly forming cartilage, what type of growth typically occurs? In older cartilage there are very few chondrogenic cells, so what type of growth mainly occurs?
appositional; interstitial
This is the only growth that occurs in articular and fibrocartilage because both lack a perichondrium
interstitial growth
Interstitial growth is important for the growth of (blank)
long bones at the epiphyseal plate
Is cartilage easily repairable?
No, cartilage has a very limited ability to repair
What is the precursor tissue of all types of cartilage?
the mesenchyme
Mitotic proliferation of mesenchymal cells gives rise to (blank)
highly cellular tissue
What separates chondroblasts from one another?
a great amount of matrix
What does multiplication of cartilage cells give rise to? What are they surrounded by?
isogenous groups; surrounded by a condensation of territorial matrix
Functions of bone: protects (blank), support and movement, hemopoieses in the (blank) marrow, energy storage in the (blank) marrow, and a (blank) reservoir
internal organs; red; yellow; mineral
Major components of bone
extracellular matrix
cells
What percentage of the cellular matrix of bone is organic? What is the organic component made by? What are three things found in this component?
35%; osteoblasts; type I collagen, proteoglycans, and glycoproteins
The proteoglycans in the extracellular matrix are composites of (blank). Three glycoproteins of extracellular matrix
aggrecan; osteocalcin, osteopontin, osteonectin
What percentage of the bone matrix is inorganic? What is it made up of?
65%; made up of hydroxyapatite crystals (calcium and phosphorus)
5 bone cells. List them!
osteoprogenitor cells osteoblasts osteocytes bone lining cells osteoclasts
What are these: cells derived from mesenchymal cells
osteoprogenitor cells
What are these: cells that develop from osteoprogenitor cells that line the inner periosteum, the endosteum and lining the Haversian canal
osteoblasts
Osteoblasts synthesize the (blank) components of bone matrix. What happens to some osteoblasts when they become surrounded by matrix?
organic; some osteoblasts become surrounded by matrix and become osteocytes
What are these: cells that lie in a lacuna within the matrix; involved in exchange of nutrients and waste with blood via canaliculi.
osteocytes
What are these: cells that remain on the bone surface when there is no active growth
bone lining cells
What are these: cells derived from a bone marrow precursor. They secrete enzymes and biochemically concentrate H+ ions to dissolve bone and calcium salt crystals thereby releasing minerals into blood.
osteoclasts
What do osteoclasts have receptors for?
various hormones, including calcitonin
Osteoclasts come from the same bone marrow precursor as (blank)
monocytes
Where are osteoclasts found?
In Howship’s lacunae
Lysosomal enzymes packaged in the Golgi complex are responsible for the resorption of calcium from bone. What enzyme is missing from the lysosomes? Where does it collagenase come from?!
collagenase; collagenase is present as procollagenase that is already embedded in the matrix when osteoblasts are laying down bone!
The osteoblast responsible for producing collagen also produces (blank), thereby setting the matrix up for degradation even while laying it down
collagenase (procollagenase)
What cells does PTH target? What does this result in?
osteoblasts; release of osteoclast stimulating factor which increases osteoclast activity
What do parafollicular cells secrete to inhibit resorption by osteoclasts?
calcitonin
Components of long bones
proximal and distal epiphysis, metaphysis, and diaphysis
Examples of short bones
capitate bone (carpal) talus
Examples of flat bones
scapula
sternum
Examples of irregular bones
sphenoid
vertebra
Bone is covered on its external surface (except at synovial articulations) with a (blank), which consists of an outer layer of (blank) and an inner cellular layer containing what cell types?
periosteum; dense fibrous connective tissue; osteoprogenitor cells and periosteal cells
The central cavity of a bone is lined with (blank), a specialized thin connective tissue composed of a monolayer of osteoprogenitor cells, osteoblasts, and endosteal cells. Following injury, cells in these layers differentiate into (blank) which become involved in the repair of damage to the bone.
endosteum; osteoblasts
What three things make up the thin CT of the endosteum?
monolayer of osteoprogenitor cells
osteoblasts
endosteal cells
Where is compact bone best seen?
In the diaphysis of long bones and the outer bone table of flat bones
Component of compact bone: concentrically arranged lamella of bone surrounding canal containing capillaries. Has lacunae containing osteocytes all of which are interconnected by canaliculi.
haversian system or osteon
What joins the osteocytes that are surrounding the haversian canals in compact bone?
canaliculi
Component of compact bone: horizontal channels containing blood vessels from bone marrow and periosteum. These interconnect the Haversian canals.
Volkmann’s canals
Different kinds of lamellae make up compact bone. What types?
inner and outer circumferential (run along the outside and along the bone marrow) and interstitial
Finally compact bone has a (blank) on the outside and a (blank) on the inside
periosteum; endosteum
Where is cancellous or spongy or trabeculated bone found? What is it covered by?
found within long, short, flat, or irregulat bones and in the bone marrow cavity of diaphysis and epiphysis; an endosteum
Cancellous/spongy/trabeculated bones have lamellae? Do they have osteons?
yes; no
There are two processes of bone formation. What is this: occurs in most flat bones, direct mineralization of matrix secreted by osteoblasts, doesn’t require a cartilage model.
intramembranous bone formation
There are two processes of bone formation. What is this: occurs for short and long bones, deposition of bone matrix on a preexisting cartilage matrix
endochondral bone formation
Most flat bones are formed by (blank)
intramembranous bone formation
Intramembranous bone formation occurs in a richly (blank) mesenchymal tissue, whose cells make contact with each other via long processes
vascularized
In trabeculated or spongy bone: Mesenchymal cells differentiate into (blank) that secrete bone matrix, forming a network of spicules and trabeculae. Collagen fibers of these developing spicules and trabeculae are randomly oriented.
Calcification quickly follows osteoid formation, osteoblasts trapped in their matrices become (blank). They retain their contacts establishing a system of (blank).
-Continuous mitotic activity of mesenchymal cells provides a supply of undifferentiated (blank) cells, which form more osteoblasts.
osteoblasts; osteocytes; canaliculi; osteoprogenitor
In compact bone: Other mesenchymal cells form outer (blank) and inner (blank). Osteoprogenitor cells from these areas will form the outer and inner plates of compact bone.
periosteum; endosteum
Most long and short bones of the body are developed by (blank)
endochonral bone formation
Endochondral bone formation is a (blank) model of bone
hyaline cartilage
How do bones grow in length?
interstitial growth of cartilage at the epiphyseal plate
How do bones growth in girth?
appositional growth at the periosteum
During bone growth at the epiphysel plate, new cartilage is formed on the epiphyseal side of the plate at the same rate as new bone is formed on the diaphyseal side of the plate. So, what happens to the epiphyseal plate and the length of the diaphysis?
The plate remains the same thickness, but the length of the diaphysis increases
5 zones of epiphyseal plate
zone of resting cartilage zone of proliferation zone of hypertrophy of cartilage zone of calcification of cartilage zone of ossification
- In endochondral bone remodeling, the perichondrium at the midriff of the (blank) of cartilage becomes (blank). This becomes the the primary ossification center.
diaphysis; vascularized
- The chondrogenic cells become osteoprogenitor cells forming (blank), and the overlying perichondrium becomes a (blank).
osteoblasts; periosteum
- The newly formed osteoblasts secrete bone matrix, forming the subperiosteal (blank) by intramembranous bone formation.
bone collar
- The hypertrophied chondrocytes within the core of the cartilage model die resulting in future marrow cavity.
- Holes etched in the bone collar by osteoclasts permit a (blank) (osteogenic bud) to enter the concavities within the cartilage model
periosteal bud
- Osteoprogenitor cells divide to form osteoblasts. producing bone matrix on the surface of the calcified cartilage. The bone matrix becomes calcified to form a calcified (blank).
cartilage/calcified bone complex.
- subperiosteal bone becomes thicker and grows in each direction from the midriff of the diaphysis toward the (blank)
- osteoclasts begin resorbing the calcified cartilage/calcified bone complex, enlarging the (blank)
epiphysis; marrow cavity
- Where do secondary ossification centers appear?
in the epiphysis
List the steps in healing of a bone fracture
- hematoma formation
- formation of granulation tissue
- soft callus formation
- hard callus formation
- remodeling
Fracture breaks blood vessels of bone and periosteum and endosteum causing bleeding and formation of a clot.
hematoma formation
Granulation tissue is a soft, fibrous tissue produced as a hematoma is infiltrated by blood capillaries and fibroblasts. Macrophages, which eat up the blood clot, osteoclasts, and osteogenic cells invade tissue from the periosteal and endosteal sides of the fracture. Osteogenic cells build up numbers within 48hrs.
formation of granulation tissue
Fibroblasts deposit collagen in granulation tissue, while some osteogenic cells become chondroblasts and produce patches of fibrocartilage called soft callus tissue.
soft callus formation
Osteogenic cells build and differentiate into osteoblasts that produce a bony collar. The hard callus that acts as a temporary splint- cements to the dead bone around injury (takes 4 to 6 weeks). Need for immobilization during this period.
hard callus formation
The hard callus persists for 3 to 4 months as osteoclasts dissolve small fragments of bone. Osteoblasts bridge the gap between the broken ends with spongy bone. This is subsequently remodeled into compact lamellar bone. Usually leaves a thickening of the bone. In adults 80% strength at 3 months
remodeling
(blank) is produced when osteoblasts produce osteoid rapidly which occurs initially in all fetal bones (but is later replaced by more resilient lamellar bone). In adults woven bone is created after (blank) or in Paget’s disease. Woven bone is (blank), with a smaller number of randomly oriented collagen fibers, but forms quickly; it is for this appearance of the fibrous matrix that the bone is termed woven.
woven bone; fractures; weaker
At what age does human bone mass peak?
age 20-30
Does spongy or cortical bone turn over at a higher rate?
spongy
This is the most common metabolic disease of bone - it is a disease in which bone volume decreases, but the bone that is present is normally calcified.
osteoporosis
In which patients is osteoporosis most commonly seen?
postmenopausal women when estrogen drops a lot
in patients with long term glucocorticoid use
patients with hyperthyroidism and hyperparathyroidism
In postmenopausal women, the drop in estrogen slows bone deposition
by (blank). Osteoclast activity is greater than (blank) resulting in a decrease in bone mass.
osteoblasts; bone deposition
the first clinical signs of underlying osteoporosis in post-menopausal women.
Kyphosis (due to compression fractures of the vertebrae), hip and wrist fractures
Which bones have high concentrations of cancellous bone, thus are among the first bones to show signs of thinning and fracture?
vertebrae and the epiphysis of the femur
