AP1 M 4.3 Bone developments and cells

Question 1

Bone

Answer 1

Bone is a living tissue that continually renews itself. A longitudinal section of a typical long bone (Figure 4.35) shows that it is not solid but has a medullary cavity filled with bone marrow

Question 2

Yellow bone marrow

Answer 2

Yellow bone marrow is a fat storage tissue found mainly in long bones.

Question 3

Red bone marrow

Answer 3

Red bone marrow is found primarily in short and flat bones, primarily to produce red blood cells. Newborns have all red bone marrow, and over time it is converted to yellow bone marrow in long bones.

Question 4

diaphysis

Bone length section

Answer 4

center length of the bone (Figure 4.35)
The diaphysis ( pl. : diaphyses) is the main or midsection (shaft) of a long bone. It is made up of cortical bone and usually contains bone marrow and adipose tissue (fat).

Question 5

medullary or marrow cavity

Answer 5

The medullary or marrow cavity extends throughout the diaphysis, or center length of the bone (Figure 4.35)

Question 6

compact bone

Answer 6

Surrounding the cavity is a layer of spongy bone that is thickest at the ends of the bone. The solid outer layer of the bone is called compact bone.

Question 7

spongy bone

Answer 7

Surrounding the cavity is a layer of spongy bone that is thickest at the ends of the bone.

Question 8

epiphysis

Answer 8

On the ends of each long bone are called proximal and distal epiphysis.

Question 9

articular cartilage

Answer 9

Within the joints, there is a layer of articular cartilage to help cushion joints and enable them to move freely. Articular cartilage is cartilage found specifically at joint articulations.

Question 10

Cartilage

Answer 10

Cartilage is another type of connective tissue, but the matrix is flexible.

Question 11

Compact bone

Answer 11

Compact bone (Figure 4.36) contains many **osteons **(formerly called Haversian systems) in which osteocytes (bone cells) in tiny chambers called lacunae are arranged in concentric circles around center canals.

Question 12

osteons

(formerly called Haversian systems)

Answer 12

osteons (formerly called Haversian systems) in which osteocytes (bone cells) in tiny chambers called lacunae are arranged in concentric circles around center canals

Question 13

osteocytes

Answer 13

many osteons (formerly called Haversian systems) in which osteocytes (bone cells) in tiny chambers called lacunae are arranged in concentric circles around center canals.

Question 14

lacunae

Answer 14

many osteons (formerly called Haversian systems) in which osteocytes (bone cells) in tiny chambers called lacunae are arranged in concentric circles around center canals.

Question 15

center canals

Answer 15

The center canals contain blood vessels and nerves. The blood vessels bring the nutrients that allow the bone to renew itself. The lacunae are separated by a matrix that contains protein fibers of collagen and mineral deposits, primarily of calcium and phosphorus salts. Compact bone is usually found on the surface of the bone and surrounds an interior of spongy bone (Figure 4.36).

Question 16

Spongy bone

Answer 16

Spongy bone (Figure 4.36) contains numerous bony bars and plates separated by irregular spaces. Although lighter than compact bone, spongy bone is still designed for strength. Just as braces are used for support in buildings, the solid portions of spongy bone follow lines of stress.

Question 17

Bone Cells

Answer 17

In the adult, bone is continually being broken down and built up again.

Question 18

osteoclasts

Answer 18

Bone absorbing cells, called osteoclasts, break down bone, remove worn cells, and deposit calcium in the blood (Figure 4.37).

Question 19

osteoblasts

Answer 19

The destruction caused by the work of osteoclasts is repaired by osteoblasts. As they form new bone, osteoblasts take calcium from the blood. Eventually, some of these cells get caught in the matrix they secrete and are converted to osteocytes, the cells found within the lacunae of osteons. Thus, through a process of remodeling, old bone tissue is replaced by new bone tissue. Because of continual remodeling, the thickness of bones can change. Physical use and hormone balance can also affect the thickness of bones. Adults and children alike require regular calcium in the diet to promote the work of osteoblasts.

Question 20

osteocytes

Answer 20

osteocytes, the cells found within the lacunae of osteons.
Maintain bone tissue structure

Question 21

Bone Formation

Answer 21

Most of the bones of the human skeleton are cartilaginous during prenatal development. Since the cartilaginous structures are shaped like the future bones, they provide models of these bones.

Question 22

ossification

Answer 22

The cartilaginous models are converted to bones (called ossification) when calcium salts are deposited in the matrix, first by precursor cartilaginous cells and later by bone-forming cells, called osteoblasts.

Question 23

Endochondral ossification

Answer 23

Endochondral ossification is the ossification of long bones from hyaline cartilage. Endochondral ossification begins at the primary ossification center in the middle of the bone. Once the cartilage cells begin to die, blood vessels start to penetrate the bone to deliver osteoblasts, forming the medullary cavity. Later, secondary centers form at the ends of the bones. A cartilaginous disk remains between the primary ossification center and each secondary center, which can increase in length. This area is commonly referred to as the growth plate.

Question 24

growth plate

Answer 24

The rate of growth is controlled by hormones, such as growth hormones and sex hormones. During puberty, the disks become completely ossified and the bone stops growing. The individual attains full adult height when this occurs.

Question 25

Bone Pathophysiology

Answer 25

Bone is a living tissue and able to repair itself when damaged. There are several types of common bone fractures that can be categorized based on how the bone breaks (Figure 4.38)

Question 26

Closed

bone break

Answer 26

Closed (or simple) fractures occur when the bone breaks but remains within the skin

Question 27

open

bone break

Answer 27

An open (or compound) fracture occurs when the bone breaks, but part of the bone shaft breaks out of the skin.

Question 28

greenstick

bone break

Answer 28

A greenstick fracture occurs when the bone bends and breaks, but not all the way across. This type of fracture occurs commonly in children because the bone tissue is still developing and soft.

Question 29

comminuted

bone break

Answer 29

A comminuted fracture happens when a bone is broken into more than two segments. Comminuted fractures typically are repaired surgically.

Question 30

impacted fracture

bone break

Answer 30

An impacted fracture occurs when one end of the broken bone shaft is pushed inside the other part of the bone

Question 31

Synovial joints

Answer 31

Synovial joints are subject to arthritis.

Question 32

rheumatoid arthritis

Answer 32

In rheumatoid arthritis, the synovial membrane becomes inflamed and thickens. Degenerative changes take place that make the joint almost immovable and painful to use.

Question 33

osteoarthritis

Answer 33

osteoarthritis, the articular cartilage at the ends of the bones disintegrates (Figure 4.39). The two bones of the joint become rough and irregular so that it becomes painful to move the joint. This type of arthritis is apt to affect the joints that have received the greatest use over the years.

Question 34

Osteoporosis

Answer 34

Osteoporosis is a bone tissue disease (Figure 4.40). When bone tissue degenerates faster than is replaced, the bones become weak. Brittle bones cause increased pain and are more likely to fracture.