Cartilage

Question 1

Why do cartilage grafts not have to be donor matched?

Answer 1

The perichondrium (seen in hyaline & elastic cartilage) is an immunoprivelaged area, which means that no antibodies can move into this area due to their size.

Question 2

List the five features of hyaline cartilage.

Answer 2

1. Ridgid & tough
2. Compressible (resists compression)
3. Has perichondrium
4. Little repairative capacity
5. Avascular & anuerogenic

Question 3

What are the locations of hyaline cartilage?

Answer 3

Fetal skeleton, ribs, larynx, tracheal & bronchial rings, nose, and articular surfaces of bones.

Question 4

List four features of elastic cartilage.

Answer 4

1. ridgid BUT FLEXIBLE
2. Has perichondrium
3. undergoes perichondrial repair
4. Avascular and anuerogenic

Question 5

What are four locations of elastic cartilage?

Answer 5

1. Larynx
2. External Ear
3. Auditory Tube
4. Epiglottis

Question 6

List seven features of fibrocartilage.

Answer 6

1. No perichondrium
2. Looks like dense connective tissue, but has lacunae
3. Mostly type I collagen (for strength), but also has some type II collagen
4. Some synnovial nutrients
5. Some innervation
6. Some repairative capacity
7. Very few isogenous groups

Question 7

List four locations to find fibrocartilage.

Answer 7

1. Intervertebral disks (annulus is 100% fibrocartilage, nuclues is fibrocartilage on its edges, mucoid like in the center)
2. Meniscuses (varying levels of vasculature, mean varying repairative capacity)
3. Symphis Pubis
4. Ligamentum of femur

Question 8

Describe the ground substance of hyaline and elastic cartilage.

Answer 8

Hylauronic acid (HUA) is th backbone of the matrix

The proteoglycan complex is attached to the HAU backbone, it is composed of:

Aggrecan is a core protein bound to HUA via link proteins

GAG’s (e.g. keratin sulfate & chondroitine) bind to the aggrecan

Question 9

Explain compressive loading force of hyaline cartliage.

Answer 9

The proteoglycan complex is the functional unit of resistance to compression by acting as a water sponge.

The GAG’s, which are anionic, bind H20 and cations (when uncompressed). This leads to expansion of cartilage, but expansion is limited by the collagen type II fibers.

When compression occurs, water is forced out until eequilibrium is reached. Once the load is released the water comes backs in.

Question 10

In regards to age, what happens to compressibility of the hyaline cartliage?

Answer 10

As you age, less proteoglycan complexes are produced by the chondrocytes to replaced the enyzmatically degraded complexes. So the load capacity would decrease.

Question 13

Distinguish interstitial and appositional growth

Answer 13

Interstitial (expands from within - bone length) and can only happen in cartilage, while appositional (adds to the surface - bone width) is able to occur in both.

Interstitial cartilage growth for bone length stops in endochondral cartilage after puberty

In adults, the perichondrium has a layer of flattened (chondrogenic layer) of cells that could become chondroblasts and continue appositional growth.

Question 14

Explain the repair of meniscus relative to its blood supply.

Answer 14

Red part, which is well vascularized, can repair easily.

Red-White part, is less vascularized, and may heal.

White part, your out of luck.

Question 15

What is osteoarthritis?

Answer 15

Thinning of fibrocartilage until it is bone-on-bone.

This may hurt.

Don’t be a fat old athletic woman who had a knee replacement.

Question 16

When does intramembranous ossification occur?

Answer 16

It occurs in the mesenchyme when it is near blood vessels, if there was not vessels present then it would form cartilage (chondrocytes).

An example of this is the formation of the bony collar, another is the formation of skull bones (flat bones)

Question 17

What are the steps in intramembranous bone growth?

Answer 17

1. Mesenchyme cells condense, but maintain their gap junctions.
2. They differentiate into osteoprogenator cells, which differentiate into osteoblasts.
3. The osteoblasts lay down the osteod, composed mainly of Type I Collagen fibers, and is then calcified to form bone spicules
4. Bone spicules grow together to form mass of spongy bone, which has osteoblasts on outside (i.e. inner layer of periosteom)/inside laying down compact bone.
5. Once the osteoblasts are entrapped, they become osteocytes because they can no longer divide (no interstitial growth potential).

Question 18

Osteoclasts are the fusion of _______, and they are responsible for:

Answer 18

Osteoblasts are the fusion of monocytes from bone marrow, and they are responsible for the continual remodeling (through macrophage-like activity) of forming bone.

Question 19

How do hormones regulate growth plate?

Answer 19

HGH promotes cartilage proliferation prior to puberty.

During puberty sex hormones surge, and causes the epiphyseal plate to close forming the epiphyseal line.

Prior to puberty, too much GH results in The Mountain and too little GH results in Tyrion.

Additional growth hormone after puberty results in acromegaly - super thick bones, but muscles too small :(

Question 21

What regulates bone remodeling?

Answer 21

Calcitonin secreted from the thyroid in response to high blood calcium, slows bone reabsorption by inhibiting osteoclasts.

PTH secreted from the thyroid in response to low blood calcium, increases bone reabsorption to increase calcium in blood.

Question 22

Compare periosteum and endosteum

Answer 22

Endosteum is going to be present on all marrow spaces, its thin, and it contains Reticular Type III Fibers.

Periosteum is present on the outside of the bone (in embryo there are two layers), Sharpys Fibers (Type I Collagen) connect the muscle to the bone.

Question 23

Explain the components of a bony matrix

Answer 23

Organic - Collagen fibers at right angles to those in adjacent lammelae, and has GAG’s, which makes bone tough.

INorganic - Hydroxyapatite (a form of Calcium Phosphate), is responsible for making bone hard.

Question 24

List the steps in bone fracture healing.

Answer 24

1. Clot formation, bone & periosteum cells die, neutrophils/macrophages/osteoclasts clean up.
2. Osteoprogenator cells from the periosteum and fibroblasts from the endosteum become activated and proliferate.
3. Osteoblasts lay down spongy bone to the fractured bone, which reattaches it (forming the internal callus). Fibro/chondroblasts lay down cartilage and DCT (forming the external callus), which surrounds fracture.
4. External callus cartilage ossified to form spongy bone, which requires new blood vessels
5. Remodeling

Question 25

What are the problems associated with the following bone diseases:

Osteomalacia

Osteoporosis

Osteopetrosis

Osteogenesis imperfecta

Answer 25

Osteomalacia - softening (rickets) due to Vitamin D Deficiency and hypocalcemia (also increase of AP firing).

Osteoporosis - augmented bone reabsorption (increased osteoclast activity) due to lack of estrogen.

Osteopetrosis - augmented bone reabsorption (lack of osteoclast activity) due to mutation of osteoclast channels,

Osteogenesis imperfecta - brittle bones due to Type I Collagen mutation.