Review Questions

Question 1

What are the two principal agents in bone matrix, and how do they each affect the properties of bone tissue?

Answer 1

The two substances are a calcium/phosphorus mineral call hydroxyapatite and collagen. The hydroxyapatite gives the bones their hardness and compressive strength, and the collagen gives the bones some flexibility and tensile strength.

Question 2

A bone cell is completely surrounded by bone matrix. what kind of bone cell is it?

Answer 2

If the cell is completely surrounded by bone matrix, it is a mature bone cell. Therefore it is an osteocyte.

Question 3

A bone cell has more than one nucleus. What kind of bone cell is it?

Answer 3

Only an osteoclast has more than one nucleus.

Question 4

Looking at bone tissue under a microscope, you see no osteons. Is this compact or cancels bone tissue?

Answer 4

Compact bone tissue is made of osteons. So, this is cancellous bone tissue.

Question 5

What kind of bone tissue contains trabeculae? What do you often find in the spaces between trabeculae?

Answer 5

Cancellous bone tissue is made of trabeculae. You often find red bone marrow in the spaces between.

Question 6

What is the term for the layers of bone tissue that form an osteon? What is the term for the layers of bone between osteons?

Answer 6

Osteons are made of layers of tissue that form cylinders. These are called concentric lamellae. Between osteons, you find interstitial lamellae.

Question 7

What are canaliculi

Answer 7

Canaliculi are microscopic passageways through which the extensions of osteocytes run. This allows the cells in bone tissues to communicate with one another.

Question 8

There are at least six reasons bone must be continually remodeled. Can you list at least five of them.

Answer 8

First, all new bone tissue is cancellous bone. Some new bone tissue must be compact bone, so cancellous tissue often needs to be remodeled into compact bone tissue. Second, bones increase and decrease in Mass based on the stress they experience. Third, bone is remodeled in order to reshape the bone as needed. Fourth, bone is remodeled to repair broken bones. Fifth, bone is remodeled to replace Worn collagen or hydroxyapatite. Sixth, bone is remodeled to regulate the calcium levels in your body.

Question 9

Bone growth occurs when new cartilage is added to the bone’s epiphyseal plate. Why doesn’t the epiphyseal plate it get thicker as the bone grows.

Answer 9

The epiphyseal plate does not thicken because cartilage is ossified at the same rate at which is it added. As a result the diaphysis gets longer, but the epiphyseal plate does not get wider.

Question 10

The epiphyseal plate separates the diaphysis from the epiphysis. On what side of the plate does the tissue ossify?

Answer 10

The epiphyseal plate ossifies on the diaphysis end.

Question 11

If a long bone has no epiphyseal plates because they have become epiphyseal lines, is there any way that a bone can grow?

Answer 11

The bone can still grow but only in width.

Question 12

What is appositional growth

Answer 12

Appositional bone growth occurs when osteoblasts lay new bone tissue on the surface of old bone tissue

Question 13

What is the purpose of external callus. What is the purpose of internal callus?

Answer 13

The external callus helps hold the broken pieces of bone together. The internal callus ossifies to become the new bone tissue.

Question 14

Which gland secretes calcitonin. Which glands secrete PTH?

Answer 14

Calcitonin is secreted by the thyroid gland and pth is secreted by the parathyroid glands.

Question 15

What is the effect of calcitonin on bone cells? What is the effect of PTH on bone cells?

Answer 15

Calcitonin decreases osteoclast activity, while PTH increases osteoclast activity.

Question 16

A person’s medical test shows a large increase in the calcitonin levels of the body. What does that tell you about the calcium level in the person’s blood?

Answer 16

The blood calcium level is too high.

Question 17

Which gland secretes a growth hormone and what effect does this hormone have on bone tissue

Answer 17

The anterior pituitary gland secretes GH. GH stimulates bone growth by increasing osteoblast activity.

Question 18

What effects do the sex hormones have on bone growth?

Answer 18

The sex hormones increase osteoblast activity which, first stimulates bone growth. However at the same time they stimulate ossification of the epiphyseal plates, which eventually halts bone growth in terms of length in long bones.

Question 19

What are the three major types of joints in the body and which type is associated with the most movement in the skeleton

Answer 19

Fibrous joints, cartilaginous joints, and synovial joints. Synovial joints are responsible for most of the skeletons movement.

Question 20

What is the purpose of the articular cartilage in a synovial joint.

Answer 20

Articular cartilage cushions the ends of the bones with a “hard plastic” finish. This makes the bones rub against each other more smoothly with no bone damage.

Question 21

What is the purpose of the synovial fluid in a synovial joint

Answer 21

Synovial fluid lubricates the joint it also supports the chondrocytes in the articular cartilage and acts as a shock absorber.

Question 22

What produces synovial fluid

Answer 22

The cells in the synovial membrane produce it.

Question 23

56 major types of synovial joints in order of decreasing range of motion assume the pivot joints offer slightly more motion than hinge joints.

Answer 23

Ball-and-socket, saddle, ellipsoid, pivot, hinge and gliding (plane)

Question 24

What type of motion does a ballet dancer on tiptoes use

Answer 24

Plantar flexion of the feet

Question 25

A person does push-ups his elbows are bent so that his body is close to the ground he then lifts up his body by straightening his arms at the elbow what kind of motion does he use

Answer 25

This is extension of the forearms

Question 26

A gymnast who is already standing on just one leg begins to twirl the lower limb that is in the air in circles what kind of motion is this

Answer 26

This is circumduction because the person is twirling the thought using the hip ball and socket joint

Question 27

A person is holding his palms up and then turns his hand so that the palms point down what motion is this

Answer 27

Pronation of the forearms

Question 28

A person holds his arms down at his sides then lifts them both up so that they are horizontal to the ground pointing out to each side what motion is this

Answer 28

This is abduction because the arms are moving away from the midline.