W28-L6: Histology of bones and joints

Question 1

What is hyaline cartilage made of?

Answer 1

Collagen type II and ground substance (GAGs etc.)

Question 2

What cell maintains hyaline cartilage?

Answer 2

Chondrocytes

Question 3

What is elastic cartilage?

Answer 3

Hyaline cartilage with the addition of elastin

Question 4

What is fibrocartilage?

Answer 4

Mixture of dense fibrous connective tissue and isolated islands of cartilage (Type 1 collagen)

Question 5

What is the structure of trabecular bone?

Answer 5

Open structure braces joints, which are continuous, constructed of lamellae

Question 6

What is the difference between yellow and red marrow?

Answer 6

Yellow is mainly fat cells, red marrow is mainly haemopoietic cells

Question 7

What are the blood vessels in the medullary cavity?

Answer 7

Sinusoids instead of capillaries

Question 8

What are the layers of the periosteum?

Answer 8

Outer fibrous layer and inner cellular layer (osteoprogenitor cells)

Question 9

What are sharpey’s fibres?

Answer 9

where there is no periosteum or endosteum
as tendon is actually
penetrating bone and interacts with bone ECM

Question 10

What is the blood supply of bone?

Answer 10

Arteries supply bones at a number of discrete points

Question 11

How do arteries supply the parts of bones?

Answer 11

Branch in marrow cavity, then separate supply to diaphysis, epiphysis and periosteum

Question 12

Where do nerves run in bones?

Answer 12

Follow blood vessels, bones are densely innervated

Question 13

What is the structure of articular cartilage?

Answer 13

No periosteum here, hyaline cartilage forms surface but there is no perichondirum (so damage causes issues with repairs)

Question 14

Is the synovial membrane an epithelium?

Answer 14

No as it lacks a basement membrane, tight junctions so very leaky

Question 15

What is the synovial surface layer?

Answer 15

two to three cells thick mix of fibroblast and macrophage like cells

Question 16

What is the sub-intimal layer?

Answer 16

where synovial fluid moves from through the synovial membrane (which is leaky) into synovial space

Question 17

What are Haversian canals?

Answer 17

Foramen that carry the blood vessel that is surrounded by a haversian system which is a metabolic system reliant on that vessel

Question 18

Where are osteoprogenitor cells?

Answer 18

In periosteum and endosteum, usually resting or quiescent

Question 19

How do osteoblasts make new bone?

Answer 19

Makes osteoid (collagen type I)

Question 20

What are osteocytes?

Answer 20

Cells that livewithin the bone, as osteoblast entombs itself with bone, maintains immediate bone around itself

Question 21

How do osteocytes gain nutrients?

Answer 21

connected to each other by tiny little tubes from one that is connected to a blood vessel

Question 22

How do osteoclasts break down bone?

Answer 22

Secrete H+, Cl- and proteases

Question 23

What is a marker of osteoclast activity?

Answer 23

Tartrate-resistant acid phosphatase

Question 24

During development how is bone laid down?

Answer 24

Membrane bone or endochondral bone

Question 25

How does membrane bone form?

Answer 25

Directly from mesoderm/mesenchyme eg skull and clavicle

Question 26

How do weight bearing bones and bones of extremities form?

Answer 26

Endochondral ossification

Question 27

How does endochondral ossification work?

Answer 27

Cartilage model is replaced by bone (not cartilage into bone though)

Question 28

How does cartilage get replaced by bone in endochonral ossification?

Answer 28

Bone collar forms around diaphysis, cartilage beneath then degenerates

Question 29

How do growth plates work?

Answer 29

on the edges of the growth plate cartilage is replaced by bone, most bone extension happens on diaphysis side

Question 30

What is woven bone?

Answer 30

New bone that is more cellular, more collagen and no haversian systems

Question 31

How are haversian systems built?

Answer 31

Osteoblasts lay layers of bone with the collagen alternating in direction