Chapter 6

Front 1

Define surface feature.

Back 1

A surface feature is a characteristic of a bone's surface that has a certain functioin, such as forming a joint, serving as a site of muscle attachment, or allowing the passage of nerves and blood vessels.

Front 2

Identify the six broad categories for classifying a bone according to shape.

Back 2

The six broad categories for classifying bones accordingto shape are flat bones, irregular bones, long bones, sesamoid bones, short bones, and sutural (Wormian) bones.

Front 3

compare a tubercle with a tuberosity.

Back 3

A tubercle is a small, rounded projection on a bone, whereas a tuberosity is a small, rough projection that may occupy a broad area on the bone's surface.

Front 4

List the major part of a long bone.

Back 4

The major parts of a long bone are the epiphysis, diaphysis, metaphysis, and medullary cavity.

Front 5

Describe the function of the medullary cavity

Back 5

The medullary cavity-the space within a bone- contains a red bone marrow, the site of blood cell production and the yellow cell production and the yellow bone marrow, adipose tissue that is an important site for energy reserves.

Front 6

If articular cartilage is avascular, how is it nourished?

Back 6

Articular cartilage is nourished by diffusion from the synovial fluid within the joints.

Front 7

Define osteocyte, oseoblast, osteoprogenitor cell, and osteoclast.

Back 7

Osteocytes are cells responsible for the maintenance and turn-over of the mineral content of bone; osteoblasts are cells that produce the fibers and matrix of bone; osteoprogenitor cells are stem cells that differentiate into osteoblasts; and osteoclasts are cells that dissolve the fibers and matrix of bone.

Front 8

How would the compressive strength of a bone be affected if the ratio of collagen to hydroxyapatite increased?

Back 8

If the ratio of collagen to hydroxyapatite in a bone increased, the bone's compressive strength would decrease, and it would become more flexible.

Front 9

If osteoclast activity exceeds osteoblast activity in a bone, what would be the effect on the bone?

Back 9

If the activity of osteclasts(which demineralize bone) exceeded osteoblast activity(production of new bone), then the bone's mineral content(and thus its mass) would decline, making it weaker.

Front 10

Define osteon.

Back 10

An osteon is the basic functional unit of mature compact bone; it consists of osteocytes organized around a central canal and separated by concentric lamellae.

Front 11

Compare the structure and function of compact bone and spongy bone.

Back 11

Compact bone, which lies over spongy bone and makes up most of a bone's diaphysis, consists of compactly arranged osteons (Haversian systems); it protects supports, and resists stress. Spongy bone makes up most of the mass of short, flat, and irregular bones and is also found at the epiphyses of long bones; it stores marrow and provides some support.

Front 12

A sample of bone has lamellae that are arranged in osteons. is the sample more likely fromt the epiphysis or the diaphysis?

Back 12

The sample is likely from an epiphysis. The presence of lamellae that are not arranged in osteons is indicative of spongy bone, which occurs in epiphyses.

Front 13

Define appositional growth.

Back 13

Appositional growth is enlargment of a bone by the addition of bone matrix as its surface.

Front 14

Distinguish between the periosteum and the endosteum.

Back 14

The periosteum is the layer that surrounds a bone; it consists of an outer fibrouw region and an inner cellular region. The endosteum is an incomplete cellular lining on the inner (medullary) surfaces of bones.

Front 15

As a bone increases in diameter, what happens to the medullary cavity?

Back 15

As a bone increases in diameter, the medullary vacity also increases in diameter.

Front 16

Define endochondral ossification.

Back 16

Endochondral ossification is the replacement of a cartilaginous model to bone.

Front 17

In endochondral ossification, what is the original source of osteoblasts?

Back 17

In endochondral ossificatioin, the source of osteoblasts is the differentiatioin of cells in the inner layer of the perichondrium.

Front 18

How could x-rays of the femur be used to determine whether a person has reached full height.

Back 18

X-rays of long bones, such as the femur, can reveal the presence or absence of the epiphyseal cartilage, which separates the epiphysis from the diaphysis so long as the bone is still lengthening. If the epiphyseal cartilage is stilll present, growth is stiill occurring; if it is not, the bone has reached its full length.

Front 19

Define intramembranous ossification.

Back 19

Intramembranous ossification is the formation of bone within connective tissue without the prior development of a cartilaginous model.

Front 20

During intramembranous ossification, which type(s) of tissue is (are) replaced by bone?

Back 20

During intramembranous ossification, mesenchyme or fibrous connective tissue is replaced by bone.

Front 21

Explain the primary difference between endochondral ossification and intramembranous ossification.

Back 21

The primary difference between the two types of ossification is that in intramembranous ossification, bone develops from mesenchyme or fibrous connective tissue, whereas in endochondral ossification, bone develops from a cartilage model.

Front 22

Describe marfan syndrome.

Back 22

Marfan syndrome is a hereditary disorder of connectivetissue, resulting in abnormally long and thin limbs and digits. The condition usually causes life-threatening cardiovascular problems.

Front 23

Compare gigantism with acromegaly.

Back 23

Gigantism results from over-production of growth hormone before puberty, causing extreme height, whereas acromegaly results from overproduction of growth hormone after puberty, causing abnormally thick bones.

Front 24

Why is pituatary dwarfis less common today in the United States?

Back 24

Pituary dwarfism is less common today in the United States, because children can be treated with synthetic growth hormone, which will provide adequate or near adequate amounts for normal growth and development.

Front 25

Identify the hormones involved in stimulating and inhibiting the release of calcium ions from bone matrix.

Back 25

The hormones involved in stimulating and inhibiting the release of calcium ions from bone matrix are parathyroid hormone (PTH), which increase blood calcium levels by causing osteoclasts to release stored calcium from bone; calcitonin, which decreases blood calcium levels by inhibiting osteoclasts and causing osteoblasts to continue depositing calcium in bone; and calcitriol, which causes an increase in intestinal calcium resorption from bone, aids the effect of PTH on bone resorption, and increases kidney reabsorption of calcium so fewer calcium ions are lost in urine.

Front 26

What effect would increase PTH secretion have on blood calcium levels?

Back 26

Increased PTH secretion would increase blood calcium levels by stimulating osteoclasts to release calcium ions from bone.

Front 27

How does calcitonin lower the calcium ion concentration of blood?

Back 27

Calcitonin lowers blood calcium levels by inhibiting osteoclast activity and increasing the rate of calcium excretion at the kidneys.

Front 28

Define open fracture and closed fracture.

Back 28

An open fracture (also called a compound fracture) is a break in the bone in which bone pierces the skin; a closed fracture (also called a simple fracture) is a break in the bone in which no bone breaks the skin.

Front 29

List the steps involved in fracture repair, beginning just after the fracture occurs.

Back 29

Immediately following a fracture, extensive bleeding occurs at the injury site. After several hours, a large blood clot called a fracture hematoma develops. Next, an internal callus forms as a network of spongy bone unites the inner edges, and an external callus of cartilage and bone stabilizes the outer edges. The cartilaginous external callus is eventually replaced by bone, and the struts of spongy bone when unite the broken ends. With time, the swelling that innitially marked the location of the fracture site is remodeled, leaving little evidence that a break occurred.

Front 30

When during fracture repair does an external callus form?

Back 30

An external callus forms early in the healing process, when cells from the endosteum and periosteum migrate to the area of the fracture. These cells form an enlarged collar (external callus) that encircles the bone in the area of the fracture.