Cartilage and bone

Question 1

What is the most common type of cartilage?

Answer 1

Hyaline

Question 2

What cell types are in cartilage? What aren’t

Answer 2

Only one! The chondrocyte

No blood vessels, nerves, or lymphatic vessels

Question 3

What is the perichondrium?

Answer 3

The envelope of dense connective tissue surrounding the cartilage tissue.

Question 4

What type of collagen fibers make up the perichondrium envelope?

Answer 4

Mostly Type I

Question 5

What are the holes in the solid matrix? What resides there?

Answer 5

Lacunae which occur in isogenous groups.

Chondrocytes reside there.

Question 6

What is the major collagen type of bone?

Answer 6

Type I

Question 7

What are Haversian canals?

Answer 7

Neurovascular channels that run parallel to the axis of the bone. Carry nerves and blood vessels.

Question 8

What are Volkman’s canals (aka perforating canals)?

Answer 8

Canals that branch off Haversian canals and run perpendicular to the long axis of the bone to carry blood vessels inward.

Question 9

What are lamellae?

Answer 9

Circles of type I collagen in the bone matrix. Those that encircle haversian canals constitute osteons/”haversian systems.”

Question 10

What is the periosteum?

Answer 10

A dense connective tissue envelope that is attached to the outside surface of the whole bone (except on its articular surfaces).

Question 11

What two layers comprise the periosteum?

Answer 11

1. Fibrous layer (dense connective tissue)

2. Inner cellular layer (aka cambium layer) which is just 1 or 2 cells thick.

Question 12

What is the endosteum?

Answer 12

The cellular monolayer that lines the marrow cavity. Can be made of bone lining cells (dormant) or osteoblasts.

Question 13

How are osteocytes connected to neighboring osteocytes?

Answer 13

Via canaliculi gap junctions

Question 14

What is osteoid bone and how does it stain?

Answer 14

Premineralized bone. Stains very pale.

Question 15

How do osteoblasts change?

Answer 15

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.

Question 16

How many nuclei do osteoclasts have?

Answer 16

Up to 1 dozen

Question 17

Where do osteoclasts reside?

Answer 17

Small depressions called Howship’s lacuna or subosteoclastic compartments.

Question 18

What do osteoprogenitor cells do?

Answer 18

Stem cells! Make osteoblasts. Reside mostly in the cellular layer of the periosteum.

Question 19

How does cartilage cause osteoarthritis?

Answer 19

With age, chondrocytes have decreased ability for mitotic and synthetic activity.

Question 20

What type of collagen makes up hyaline cartilage?

Answer 20

Type II

Question 21

How does hyaline cartilage appear on histology?

Answer 21

Glassy and smooth

Question 22

Cartilage is ___% collagen (type II) and _____% proteoglycans (aggrecan) and adhesive glycoproteins

Answer 22

50/50

Question 23

On hyaline cartilage staining, the darker regions are called what? paler?

Answer 23

Darker = territorial
Light = interterritorial

Question 24

Hyaluronic acid acts as a back bone for what?

Answer 24

Proteoglycan aggregates covered in GAGs

Question 25

Why does hyaluronic acid provide turgor?

Answer 25

So many negative sulfates attracts Na+ which sucks in water.

Question 26

What special places do you find fibrocartilage?

Answer 26

Intervertebral discs and transitions into tendons. Increased tensile strength and stiffness! *no perichondrium

Question 27

Where do you find elastic cartilage?

Answer 27

Ears and epiglottis (increased flexibility and elasticity!)

Question 28

In what two ways can cartilage grow?

Answer 28

1. Apposition - adding on to the surface at edge of perichondrium 2. Interstitial growth - mitosis

Question 29

The _____ of helical layers of collagen alternates to increase strength of bone.

Answer 29

pitch

Question 30

What are the mineral crystals of bone made of?

Answer 30

Hydroxyapatite

Question 31

Does mineral impregnate the collagen as the matrix becomes calcified?

Answer 31

Yes

Question 32

Osteocyte processes extend into ______ and recognize changes in ______ to direct bone remodeling.

Answer 32

cannaliculi, pressure

Question 33

Can bone lining cells be reactivated into osteoblasts if needed?

Answer 33

Yes

Question 34

How does osteoclast size change?

Answer 34

They will fuse if the demand for resorbing bone increases (asynchronus fusion). Up to 25 nuclei.

Question 35

What is the purpose of the ruffled border?

Answer 35

Increase the number of transmembrane proteins (namely to pump H+ into subosteoclastic compartment)

Question 36

What are the 3 membrane domains of an osteoclast?

Answer 36

1. Ruffled border 2. Sealing zone 3. Basal zone

Question 37

What does the osteoclast basal zone do?

Answer 37

Antiresorptive surface (Cl/HC30 exchanger)

Question 38

Describe how the bone eating acidic environment in the subosteoclastic environment is created.

Answer 38

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.

Question 39

What enzymes released by the lysosomes degrade the organic component of bone?

Answer 39

Cathepsins Collagenases Metalloproteinases

Question 40

In intramembranous bone formation, bone builds up _______ between capillaries as mesenchyme is condensed.

Answer 40

equidistant

Question 41

How is woven bone different than lamellar bone?

Answer 41

More cellular More ground substance/less collagen Grows and resorbs more rapidly Mineralizes more rapidly but less completely.

Question 42

How do chondrocytes change as they switch from making collagen to mineralization?

Answer 42

They hypertrophy and then secrete type X collagen, alkaline phosphatase, pyrophosphatase, and matrix vesicles.

Question 43

How does type X collagen appear?

Answer 43

Bent tight angle bits so that they can interact with mineral.

Question 44

In the absence of a blood supply, osteoprogenitor cells will become ______.

Answer 44

Chondroblasts