Bone

Question 1

What are the two types of bone, on a microscopic level?

Answer 1

Lamellar and woven

Question 2

What is the primary mineral in bone?

Answer 2

Calcium hydroxyapatite

Question 3

What is the major type of collagen in bone?

Answer 3

Type I

Question 4

What is the microstructure of lamellar bone?

Answer 4

Sheets arranged in layers, with each layer oriented a different direction, similar to plywood. This optimizes stress resistance

Question 5

What is woven bone?

Answer 5

Embryonic bone, and the initial form of bone made during fracture repair

Question 6

What is the epiphysis?

Answer 6

The ends of the bone

Question 7

What is the diaphysis?

Answer 7

The shaft of the bone

Question 8

What is the periosteum?

Answer 8

The fibrous material that covers bone, connects to muscle, tendon, and ligament, and contains osteoblasts

Question 9

What is the endosteum?

Answer 9

The inner surface of bone that contains cells capable of bone digestion and bone synthesis

Question 10

What are osteons?

Answer 10

long cylinders of bone that run parallel to the long axis of bone. They consist of a central channel containing nerves and vessels, surrounded by concentric rings of lamellar bone

Question 11

How do osteoblasts form new bone?

Answer 11

They secrete type I collagen and factors/enzymes that catalyze calcium hydroxyapatite formation

Question 12

What is the effect of PTH on osteocytes?

Answer 12

It makes them resorb bone and release calcium

Question 13

How do individual osteocytes communicate with one another and vasculature?

Answer 13

Through filopodia which extend through canalculi in the bone crystals

Question 14

How do osteoclasts degrade bone?

Answer 14

They secrete proteases (for collagen) and H+ (for calcium hydroxyapatite) into the space between themselves and bone. Dissolved material endocytosed

Question 15

What is periosteal apposition?

Answer 15

The process by which bone is added to the periosteal surface and degraded from the endosteal surface, increasing diameter and limiting thickness of compact bone. This serves to reduce the weight

Question 16

What is the progenitor cell for osteoclasts? What triggers the maturation?

Answer 16

monocytes; factors on osteoblasts trigger differentiation, particularly the secreted Macrophage colony stimulating factor (M-CSF) and Receptor Activator for NFkB ligand (RANKL)

Question 17

RANKL increases differentiation from proosteoclasts to osteoclasts. What compounds increase its expression?

Answer 17

PTH and Leptin

Question 18

What compuound inhibits RANK-RANKL interaction?

Answer 18

OPG (osteoprotegerin). OPG is secreted by osteoblasts in response to estrogen

Question 19

What are the three stages of bone remodelling?

Answer 19

1Activation of Osteoclasts
2Reversal (inactivation/apoptosis of osteoclasts, activation of osteoblasts)
3Bone formation

Question 20

What is Howship’s lacuna?

Answer 20

The space between an osteoclast and the bone it is working on

Question 21

What is osteoid?

Answer 21

The unmineralized matrix composed of type I collagen and glycosaminoglycans (GAGs). This forms part of bone along with calcium hydroxyapatite

Question 22

Where is the epiphyseal growth plate?

Answer 22

the interface between the shaft and the epiphysis

Question 23

What are the perpindicular channels that connect Haversian canals called?

Answer 23

Volkmann’s canals

Question 24

What are the two methods by which bone is produced from mesenchymal tissue?

Answer 24

Endochondral ossification is the process by which cartilage is progressively replaced by bone at the epiphyseal growth plates. This occurs in long bones, the vertebrae, and the pelvis. Intramembranous ossification is the process by which mesenchymal tissue is
directly replaced by bone without an intermediate cartilage step. It occurs most
notably in the bones of the skull.

Question 25

What is the effect of estrogen on bone growth?

Answer 25

Estrogen causes osteoblasts to increase the production of OPG and decrease production of RANK ligand
Therefore in the production of estrogen, the bone will not activate osteoclasts. This is why in older women, lower estrogen leads to too much osteoclast activation and therefore osteoporosis