CT 3 A

Question 1

Most extracellular matrix in bone is _____.

Answer 1

calcified and packed with dense parallel collagen fibers

Question 2

Bone matrix also contains ____

Answer 2

negatively charged proteoglycans and other glycoproteins, but several of these are specific to bone.

Question 3

Unlike most connective tissues, bone matrix is unique in containing:

Answer 3

large amounts of a crystallized form of Ca2+ and PO4 called hydroxyapatite, the crystals are found on collagen fibers, and in the ground substance

i.e. the matrix is mineralized or calcified.

Question 4

Bone is _____

Answer 4

vascular and innervated.

Threading throughout the matrix of bone tissue are a large number of channels that contain both blood vessels and nerves.

Question 5

Thus, relatively short distances of diffusion are needed for _____

Answer 5

nutrients to reach osteocytes within the bone matrix, and for transport of mobilized Ca2+ from the matrix to the bloodstream.

Question 6

Haversian canals.

Answer 6

In long bones, channels that traverse the long axis through compact bone

Question 7

Bone _____ tend to surround a Haversian canal in _____;

Answer 7

lamellae

concentric rings (like the rings of a tree)

Question 8

Volkmann’s canals

Answer 8

link Haversian canals to each other and to the periosteum at the bone surface.

Question 9

lamellae and their canal are frequently referred to as a unit called the _____.

Answer 9

osteon

Question 10

The formation of cartilage and bone tissue are highly regulated processes that _____.

Answer 10

integrate cell proliferation and differentiation with the synthesis and transformation of extracellular matrix

Question 11

The formation of long bones is directly tied to _______

Answer 11

formation of cartilage,

Question 12

Both cartilage and bone formation begins in ____

Answer 12

embryogenesis.

Some complete bones are formed before birth.
Other bone tissue, particularly in the long bones of the extremities continue to be formed during post-natal growth.

Question 13

formation of new bone tissue continues through the ____

Answer 13

remodeling of existing bone, and can be stimulated following severe injury (bone fracture).

Question 14

Intramembranous ossification: occurs _____

Answer 14

In the absence of a pre-made cartilage tissue:

Question 15

Intramembranous ossification occurs first when:

Answer 15

Within a sheet of connective tissue, groups of mesenchymal cells come together (a process called condensation), transform into osteoprogenitors, which then differentiate into osteoblasts.

Question 16

The flat bones all form by

Answer 16

intramembranous ossification.

Question 17

These islands of osteoblasts secrete ___.

Answer 17

osteoid

Question 18

More cells at the periphery of these islands convert into ____

Answer 18

other osteoblasts adding to the mass of the developing bone; eventually “bone islands” join.

Question 19

Calcification of the matrix is ____.

Answer 19

delayed relative to its initial formation.
initially: trabecular
then vessels grow in

Question 20

Initially, the bone matrix is of _____.

Answer 20

woven bone

Question 21

remodeling by osteoclasts and new bone deposition by ____

Answer 21

osteoblasts converts some of this bone to a compact lamellar form.

Question 22

Endochondral ossification is made by:

Answer 22

In the embryo and fetus, cartilage tissue generates various structures of the skeleton that will become bone. Subsequently, some cells within the perichondrium are converted to osteoprogenitors. This sets in motion a series of events that cause the replacement of cartilage by bone.

Question 23

Formation of the cartilage model:

Answer 23

Mesenchymal cells undergo division and differentiate to generate a group of chondrocytes. Chondrocytes begin to secrete the matrix typical of hyaline cartilage. As they secrete their matrix individual chondrocytes become encased in their lacuna. Eventually an elongate structure in the relative proportion of a long bone is formed

Question 24

cartilage model then continues to grow in two different ways:

Answer 24

1. appositional growth

2. interstitial growth

Question 25

Appositional growth (growth at the surface):

Answer 25

In the perichondrium at the cartilage surface, mesenchymal and/or fibroblast-like cells proliferate and differentiate into more chondrocytes, which secrete more hyaline matrix.

Question 26

Interstitial growth (growth from within)

Answer 26

Chondrocytes embedded in matrix continue to proliferate within their lacunae and secrete the ECM, leading to internal growth of the tissue. Groups of chondroctyes within a lacuna or still close together are actually clones of cells derived from mitosis and are called isogenous groups

Question 27

isogenous groups

Answer 27

of clonal origin

Question 28

where is a collar of bone is formed?

Answer 28

On the surface of the diaphyseal shaft of the cartilage model (i.e. within the perichondrium),

Question 29

Mesenchymal cells develop into ___

Answer 29

osteoprogenitors, which in turn become osteoblasts.