Cartilage and bone Flashcards
What is the most common type of cartilage?
Hyaline
What cell types are in cartilage? What aren’t
Only one! The chondrocyte
No blood vessels, nerves, or lymphatic vessels
What is the perichondrium?
The envelope of dense connective tissue surrounding the cartilage tissue.
What type of collagen fibers make up the perichondrium envelope?
Mostly Type I
What are the holes in the solid matrix? What resides there?
Lacunae which occur in isogenous groups.
Chondrocytes reside there.
What is the major collagen type of bone?
Type I
What are Haversian canals?
Neurovascular channels that run parallel to the axis of the bone. Carry nerves and blood vessels.
What are Volkman’s canals (aka perforating canals)?
Canals that branch off Haversian canals and run perpendicular to the long axis of the bone to carry blood vessels inward.
What are lamellae?
Circles of type I collagen in the bone matrix. Those that encircle haversian canals constitute osteons/”haversian systems.”
What is the periosteum?
A dense connective tissue envelope that is attached to the outside surface of the whole bone (except on its articular surfaces).
What two layers comprise the periosteum?
- Fibrous layer (dense connective tissue)
2. Inner cellular layer (aka cambium layer) which is just 1 or 2 cells thick.
What is the endosteum?
The cellular monolayer that lines the marrow cavity. Can be made of bone lining cells (dormant) or osteoblasts.
How are osteocytes connected to neighboring osteocytes?
Via canaliculi gap junctions
What is osteoid bone and how does it stain?
Premineralized bone. Stains very pale.
How do osteoblasts change?
As osteoblasts become less active they become smaller and flatter. They become fully squamous when they cease activity. Then they are called bone lining cells.
How many nuclei do osteoclasts have?
Up to 1 dozen
Where do osteoclasts reside?
Small depressions called Howship’s lacuna or subosteoclastic compartments.
What do osteoprogenitor cells do?
Stem cells! Make osteoblasts. Reside mostly in the cellular layer of the periosteum.
How does cartilage cause osteoarthritis?
With age, chondrocytes have decreased ability for mitotic and synthetic activity.
What type of collagen makes up hyaline cartilage?
Type II
How does hyaline cartilage appear on histology?
Glassy and smooth
Cartilage is ___% collagen (type II) and _____% proteoglycans (aggrecan) and adhesive glycoproteins
50/50
On hyaline cartilage staining, the darker regions are called what? paler?
Darker = territorial Light = interterritorial
Hyaluronic acid acts as a back bone for what?
Proteoglycan aggregates covered in GAGs
Why does hyaluronic acid provide turgor?
So many negative sulfates attracts Na+ which sucks in water.
What special places do you find fibrocartilage?
Intervertebral discs and transitions into tendons. Increased tensile strength and stiffness!
*no perichondrium
Where do you find elastic cartilage?
Ears and epiglottis (increased flexibility and elasticity!)
In what two ways can cartilage grow?
- Apposition - adding on to the surface at edge of perichondrium
- Interstitial growth - mitosis
The _____ of helical layers of collagen alternates to increase strength of bone.
pitch
What are the mineral crystals of bone made of?
Hydroxyapatite
Does mineral impregnate the collagen as the matrix becomes calcified?
Yes
Osteocyte processes extend into ______ and recognize changes in ______ to direct bone remodeling.
cannaliculi, pressure
Can bone lining cells be reactivated into osteoblasts if needed?
Yes
How does osteoclast size change?
They will fuse if the demand for resorbing bone increases (asynchronus fusion). Up to 25 nuclei.
What is the purpose of the ruffled border?
Increase the number of transmembrane proteins (namely to pump H+ into subosteoclastic compartment)
What are the 3 membrane domains of an osteoclast?
- Ruffled border
- Sealing zone
- Basal zone
What does the osteoclast basal zone do?
Antiresorptive surface (Cl/HC30 exchanger)
Describe how the bone eating acidic environment in the subosteoclastic environment is created.
Carbonic anhydrase produces H+ and HCO3-. H+ is used at surface to resorb and bicarb is kicked out in exchange for Cl-. Cl- also moves into subosteoclastic environment.
What enzymes released by the lysosomes degrade the organic component of bone?
Cathepsins
Collagenases
Metalloproteinases
In intramembranous bone formation, bone builds up _______ between capillaries as mesenchyme is condensed.
equidistant
How is woven bone different than lamellar bone?
More cellular
More ground substance/less collagen
Grows and resorbs more rapidly
Mineralizes more rapidly but less completely.
How do chondrocytes change as they switch from making collagen to mineralization?
They hypertrophy and then secrete type X collagen, alkaline phosphatase, pyrophosphatase, and matrix vesicles.
How does type X collagen appear?
Bent tight angle bits so that they can interact with mineral.
In the absence of a blood supply, osteoprogenitor cells will become ______.
Chondroblasts
