Lecture 2/3 - Bone and Cartilage Flashcards
What is the characteristic of the CT cartilage?
Specialized w/ abundance of ECM
What is the composition of ECM in cartilage?
Firm, w/ GAG’s, proteoglycans, and collagen fibers
Why is the ECM of cartilage firm?
Bears a lot of mechanical stress
What do PG’s interact with?
the collagen fibers
What are the three type of cartilages?
Hyaline, Elastic, and Fibrocartilage
What kind of blood support does cartilage have?
Avasular, relies heavily on CT for diffusion
What is missing (2 things) from cartilage?
Lymphatics and innervation
What are present in lacunae?
Chondrocytes
What do chondrocytes do?
secrete ECM
What are the layers of the perichondrium?
Outer fibrous layer and inner cellular layer
What are the characteristics of the fibrous layer?
Dense CT, collagen, fibroblasts, and avascular
What type of collage is in the fibrous layer?
Type 1 collagen
What is the perichondrium?
CT surrounding elastic and SOME hyaline cartilage
What is present within the cellular layer?
Chondrogenic cells
What are chondrogenic cells?
cartilage stem cells
Why is the perichondrium important?
appositional growth, maintenance, and some repair
What can chondrocytes form?
Isogenous groups since they are mitotic
What cells secrete ECM in cartilage?
Chondrocytes and chondroblasts
What type of collagen do ALL cartilage types contain?
Type II
What other collagen type does fibrocartilage have?
Type I collagen
What other collagen type does elastic cartilage have?
elastic
What do PG’s do?
Shock absorbers, resist compression
Why is it beneficial that they interact with Type II fibers?
Combines strength with resiliency
What do adhesive glycoproteins do?
Help bind cells to ECM
What are the two ways cartilage can grow?
Appositional or Interstitial
What is Appositional growth?
Growth on surface, chondrogenic cells differentiate into chondroblasts (secrete ECM)
NEED perichondrium
What is interstitial growth?
Growth from within
Chondrocytes mitosis/ECM secretion
What limits cartilage growth?
Avascular, can’t grow beyond capability of diffusion
What are the downsides of cartilage?
Size limited and poor regenerative capacity
What limit s cartilage repair?
avascular and chondrocyte immobility
What can limited repair be intiated by?
Perichondrium
What occurs with cartilage repair?
Scarring = dense CT
Where is hyaline cartilage found?
Nose, articular cart., larynx, costal cart., etc
What is the function of hyaline cartilage?
Structural support (resist compression), bone growth, and repair
How does hyaline cartilage aid in bone growth?
Long bone template and growth plates
What type of growth occurs with hyaline cartilage?
Appositional and interstitial
What hyaline cartilage doesn’t have perichondrium?
Articular and Epiphyseal growth plates
In what state are chondrocytes in hyaline cartilage?
Isogenous groups
What are the matrixes in hyaline cartilage?
Capsular, territorial, and interterritorial
What is in the capsular matrix?
Many PG’s (very dark staining)
Where is the capsular matrix?
around chondrocytes
Where is the territorial matrix?
near chondrocytes
What is in the territorial matrix?
Type II fibrils and PG’s (dark staining)
Where is the interterritorial matrix?
Away from chondrocytes
What is in the interterritorial matrix?
very few PG’s (light staining)
Where is elastic cartilage found?
External ear, external auditory meatus, auditory tube, epiglottis, and larynx
What is the function of elastic cartilage?
Flexible structural support
Has resiliency but is pliable
Is there perichondrium in elastic cartilage?
yes
What is the structure of the chondrocyte in elastic cartilage?
Abundant, isogenous groups present
What makes up the ECM in elastic cartilage?
Type II collagen, elastic fibers, and PG’s
Where is fibrocartilage found?
Ligament insertions and w/i some joints
What is the function of fibrocartilage?
Rigid structural support, resists tension and compression (very tough)
Why is hyaline a transitional tissue?
combines features of hyaline cartilage and dense CT
Does hyaline have a perichondrium?
No
What is the structure of chondrocytes in hyaline cartilage?
Isogenous groups lined up with type I collagen
What does the ECM of fibrocartilage contain?
type I and II collagen w/ less ground substance
How is bone a specialized CT?
bones cells and mineralized ECM
What does bone contribute to the body?
framework, hematopoiesis, lever for muscles, and reservoir for minerals
What is the periosteum?
Contains the blood supply for the bone
What specialized structure is within the periosteum?
Sharpey’s fibers
What are sharpey’s fibers made out of?
type 1 collagen
What do Sharpey’s fibers do?
adhere periosteum firmly to bone (tendon/ligament to bone)
What is the endosteum?
Monolayer of stem cells on internal surface of marrow cavity
What are the two portions of the bone ECM?
organic and inorganic
What makes up the organic portion of the bone ECM?
Mostly type I collagen and ground substance
What is ground substance?
PG’s and glycoproteins
What does the organic portion of bone ECM give the bone?
flexibility and tensile strength
What makes up the inorganic portion of bone ECM?
Hydroxypatite crystals w/ type I collagen fibers
What does the inorganic portion of bone provide to the bone?
rigidity and compressive strength
What are the types of bone cells?
Osteocytes, osteoclasts, and osteoblasts
What are osteoblasts?
Bone forming cells
What does osteoblast organelle profile say about it?
extensive rER and golgi - makes ECM
What is an osteoid?
initial organic component
What makes the osteoid?
Osteoblasts
What happens to the osteoid?
calcified later on in development
What can effect the processing of the osteoid?
low in vitamin D
Where does an osteocyte come from?
Osteoblast
Where are osteoblasts located?
lacunea
What is different about osteoblast growth?
Amitotic
What is osteoblast’s job?
maintain the ECM
Why do osteoblast’s have long cytoplasmic processes?
mechanosensitive
Where do osteoclasts come from?
Monocytes
Where are osteoclasts?
in resorption bays (Howship’s lacunae)
What is a ruffled border? What cell does this describe?
Osteoclast. Portion in direct contact with bone cause infolding of the plasma membrane
What is the function of an osteoclast?
Resorption of bone
What organelles do osteoclasts have more of due to it’s function?
lysosomes, mitochondria, and increased surface area
What is the clear zone?
ring of cytoplasm around resorptive compartment
What purpose does the clear zone have?
prevent damage to surrounding tissues
What hormones affect bone?
PTH and calcitonin
Where does PTH come from?
Parathyroid gland
What does PTH promote?
resorption, leads to an increase in bone calcium levels
How does PTH affect bone?
receptors located on osteoblasts, lead to production of osteoblast stim. factor
What is the end result of PTH?
osteoclast stimulation
Where does calcitonin come from?
Thyroid gland
How does calcitonin affect bone?
Receptors on osteoclasts
What does calcitonin do?
inhibit osteoblast
What are the processes in bone remodeling?
resorption and formation
What regulates bone remodeling?
hormones and mechanically
What occurs with too much resorption?
osteopenia and osteoporosis
What occurs with too much formation?
osteosclerosis and osteopetrosis
What are macroscopic bone structure?
compact and trabecular bone
What is compact bone?
Cortical, dense
What is trabecular bone?
Cancellous, spongy (marrow)
Where is trabecular bone oriented?
toward stress lines
What are microscopic bone structures?
woven (immature) and lamellar (mature)
When is woven bone present?
initial bone formation and fracture repair
What is the cellular component of woven bone?
Poorly organized type I collagen, weak
What happens to woven bone?
replaced by lamellar bone
What is the cellular component of lamellar bone?
very strong, well-organized type-1 collagen
At what points does lamellar bone replace woven bone?
Primary and secondary bone formation
What is primary bone formation?
Primary osteons
What is secondary bone formation?
remodeling of primary bone
What are cement lines?
outer border of osteon, where bones tend to fracture
What is another name for osteons?
Haversian system
What is an osteon?
basic unit of bone, rings of lamellar bone around central canal
What is within the central canal?
blood vessels and nerves, diffusion through canaliculi
What is a perforating canal?
connect central canals with each other
connect blood vessels in periosteum to marrow
