CT 2 B

Question 1

If one makes a longitudinal section through a bone, there are two distinct areas:

Answer 1

1. The outer, or cortical region, is solid and is composed of compact bone.
2. The inner portion contains spongy bone which has thin anastomosing spicules called trabeculae

Question 2

At a gross level, there are two general types of bone:

Answer 2

1. the flat bones (e.g. the skull, mandible)

2. the long bones (e.g. tibia, femur, humerus).

Question 3

A long bone consists of a

Answer 3

1. central shaft
2. the diaphysis
3. two expanded ends, each called an epiphysis.

Question 4

The outer, or cortical region, is:

Answer 4

solid and is composed of compact bone.

Question 5

The inner portion contains:

Answer 5

spongy bone which has thin anastomosing spicules called trabeculae (spongy bone is also called cancellous or trabecular bone).

Question 6

Compact and trabecular bone contain:

Answer 6

the same types of cells and the same matrix but different relative activities of bone cells lead to different structural arrangements.

Question 7

compact bone provides:

Answer 7

most of the strength of the bone for support

Question 8

trabeculae provides:

Answer 8

extensive surface area for metabolism.

Question 9

Within the spaces between the trabeculae of the inner spongy bone is:

Answer 9

soft tissue called bone marrow.

Question 10

Bone marrow consists of:

Answer 10

either hematopoietic tissue (red bone marrow) or adipose cells (white bone marrow) surrounded by loose connective tissue containing numerous blood vessels.

Question 11

The outer surface covering the bone called the ____

Answer 11

periosteum, which contains dense connective tissue containing fibroblasts, bone precursors and bone cells.

Question 12

The inner surface where trabeculae contact internal soft tissue is called the _____

Answer 12

endosteum, which is where most calcium mobilization and storage occurs.

Question 13

there are tunnel-like channels through bone that also contain _____

Answer 13

small amounts of soft connective tissue, blood vessels, and nerves.

Question 14

Bone cells:

Answer 14

1. osteoprogenitor
2. osteoblasts
3. osteocytes
4. osteoclasts

Question 15

Osteoprogenitor cells are ____

Answer 15

stem cells that are capable of cell division to generate the osteoblasts and osteocytes that comprise most of the cells of bone.

Question 16

Osteoprogenitors are present in both _____

Answer 16

the periosteal and endosteal surfaces, and in the soft connective tissue of the channels.

Question 17

Osteoblasts line _____

Answer 17

the inner layers of both periosteal and endosteal surfaces where bone growth or remodeling is occurring.

Question 18

Osteoblasts actively secrete _____.

Answer 18

the initial un-mineralized extracellular matrix of bone, which is called osteoid

Question 19

Osteoblasts also pinch off _____.

Answer 19

membrane-enclosed vesicles, the matrix vesicles, which contain enzymes that initiate bone calcification (mineralization)

Question 20

Osteoblasts are connected to each other and to nearby osteocytes by ____

Answer 20

gap junctions.

Question 21

Osteoblasts are also capable of _____

Answer 21

cell division

Question 22

Osteocytes are directly derived from ____.

Answer 22

osteoblasts

Question 23

Osteocytes arrest in___.

Answer 23

Go

Question 24

canaliculi

Answer 24

osteocytes extend long processes through tiny channels in the calcified matrix

form gap junctions with processes from other osteocytes

Question 25

the cells of bone form a_____.

Answer 25

living interconnected lattice of cells, which can communicate directly, and are surrounded by abundant calcified matrix

Question 26

Osteocytes retain a limited ability to ______.

Answer 26

modify bone matrix, but they do not secrete much matrix material

Question 27

the ____ are the secretory engines that make bone matrix.

Answer 27

osteoblasts

Question 28

The role of osteocyte activity in bone maintenance is to ___

Answer 28

signals to each other and to osteoblasts at the surface through their gap junctions

Question 29

Osteoclasts are derived from ____

Answer 29

monocytes in the blood, which themselves originate from hematopoietic stem cells in the bone marrow.

Question 30

Osteoclasts resemble and are related to _____.

Answer 30

macrophages

Like macrophages, osteoclasts are phagocytic cells.

Question 31

osteoclasts specifically _____

Answer 31

degrade bone or cartilage matrix.

Question 32

Osteoclast roles in bone dynamics:

Answer 32

1. degrade cartilage or bone matrix to allow inward growth of blood vessels during bone formation.
2. resorb already made bone to promote remodeling of the bone matrix.
3. resorb bone for the purpose of mobilizing Ca2+ into the bloodstream
   (critical for maintaining proper Ca2+ concentrations in blood)