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A&P Exam 2 > Chapter 6 - Part 3 - Osseous Tissue And Bone Structure > Flashcards

Chapter 6 - Part 3 - Osseous Tissue And Bone Structure Flashcards

1
Q

In order for bones to grow and be maintained, they require…..

A

An extensive blood supply

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2
Q

Is osseous tissue vascular or avascular?

A

HIGHLY vascularized

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3
Q

Why is osseous tissue highly vascularized?

A

Bones need an extensive blood supply to grow and be maintained

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4
Q

In a typical bone, ___(how many) major sets of blood vessels develop?

A

3

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5
Q

What are the 3 major sets of blood vessels that develop in bone?

A
  1. Nutrient artery and vein
  2. Metaphyseal Vessels
  3. Periosteal Vessels
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6
Q

The blood vessels that supply the diaphysis form by invading the…

A

Invading the cartilage model as endochondral ossification begins

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7
Q

How many nutrient arteries/ veins do typical bones have? What about other bones such as the femur?

A

Typical bones have only one nutrient artery and nutrient vein. Femur has more than one of each

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8
Q

The nutrient artery/vein enters the bone through round passageways called….

A

Nutrient foramina in the diaphysis

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9
Q

Where do the metaphyseal vessels supply blood to??

A

The inner (diaphyseal) surface of each epiphyseal cartilage (where that cartilage is being replaced by bone)

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10
Q

Where do the periosteal vessels provide blood to?

A

The superficial osteons of the shaft. Also enter the epiphyses during endochondral bone formation, providing blood to secondary ossification centers

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11
Q

The ____ and ____ components of the bone matrix are continuously being recycled and renewed through the process of ________

A

ORGANIC AND MINERAL, remodeling

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12
Q

When does bone remodeling occur?

A

Throughout a persons entire life. It’s part of normal bone maintenance

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13
Q

Remodeling can either change the ____ or the _____

A

Matrix or the bone itself

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14
Q

Bone remodeling involves interplay among the activities of _____,_____, and_____

A

Osteocytes, osteoblasts, osteoclasts

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15
Q

In adults, what bone cell is continuously removing and replacing the surrounding calcium salts?

A

Osteocytes

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16
Q

Normally, the activities of _____ and ______ are balanced

A

Osteoblasts and osteoclasts

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17
Q

As quickly as osteoblasts form one osteon, osteoclasts remove another by a process called…?

A

Osteolysis

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18
Q

The turnover rate of bone is….

A

High

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19
Q

In young adults almost ____of the skeleton is recycled and replaced every year

A

1/5

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20
Q

Is the rate of turnover the same everywhere? Give an example.

A

NO. The spongy bone in the head of the femur may be replaced 2 or 3 times a year while the compact bone of the shaft remains largely unchanged

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21
Q

Besides calcium, what other ions can be incorporated into the matrix of bone? Why?

A

Lead, strontium, cobalt, uranium, plutonium because they are biochemically similar to calcium

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22
Q

Can osteoblasts differentiate between calcium and heavy metal ions? What danger does this present?

A

Osteoblasts cannot differentiate between them. Therefore, these ions will be deposited into the bone matrix and can have detrimental health effects- they can be released into circulation after being absorbed and accumulated (remodeling process) over a period of years. Radioactive substances can cause thyroid cancer, leukemia, and other cancers

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23
Q

Describe bone remodeling

A

Bone remodeling refers to the process whereby old bone is continuously being destroyed by osteoclasts while new bone is being constructed by osteoblasts

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24
Q

What gives bone the ability to adapt to new stresses?

A

The turnover and recycling of minerals

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25
Q

What is theorized as the mechanism that controls the internal organization and structure of bone?

A

The sensitivity of osteoblasts to electrical events

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26
Q

Explain the process of osteoblasts reacting to a stressed bone.

A

When a bone is stressed, the mineral crystals generate small electrical fields. This attracts osteoblasts to the site and once they get to the area they produce new bone. Small electrical fields can thus stimulate bone healing

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27
Q

The shape of bones reflects….

A

The forces applied to them

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28
Q

The unique shape of each bone reveals that they are….

A

Adaptable

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29
Q

Bumps and ridges on the surface of a bone indicate…

A

Sites where tendons are attached

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30
Q

A muscle has bones with bumps and ridges, indicating that a tendon is attached. What happens to these ridges and bumps when muscles become more powerful?

A

They enlarge to withstand the increased forces

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31
Q

Heavily stressed bones become ___ and ___ whereas bones that are not subject to ordinary stresses become ___ and ___

A

Thicker and stronger, thin and brittle

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32
Q

Describe the bone structure of someone who is a champion weight lifter

A

Massive bones with thick, prominent ridges

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33
Q

“Couch potatoes” must do what to stimulate normal bone maintenance and strength?

A

Moderate amounts of physical activity and weight bearing activities

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34
Q

When can degenerative changes in the skeleton occur?

A

After relatively brief periods of physical activity

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35
Q

If you use a crutch to take the weight off of an injured leg, how much bone mass of that unstressed bone would be lost after a few weeks?

A

Up to 1/3 of its mass

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36
Q

Normal bone growth and maintenance cannot occur without a constant dietary source of ____ and ____. To a lesser degree, ___,____,____

A

Calcium and phosphate salts
To a lesser degree: iron, fluoride, manganese

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37
Q

Where is the hormone CALCITROL synthesized?

A

In the kidneys

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38
Q

What is calcitriol essential for?

A

Normal calcium and phosphate ion absorption

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39
Q

Calcitriol is synthesized from a related steroid called…..

A

Cholecalciferol (vitamin d3)

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40
Q

Cholecalciferol can be taken into the human body in which 2 ways?

A

Produced in the skin or absorbed from the diet

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41
Q

Besides vitamin d3, what other vitamins are essential for bone structure and strength?

A

Vitamin C, vitamin A, vitamin K, vitamin b12

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42
Q

Specifically, why is vitamin C important for bones?

A

Vitamin c is required for key enzymatic reactions in collagen synthesis and osteoblast differentiation

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43
Q

What is one of the signs of Vitamin C deficiency?

A

Scurvy - loss of bone mass and strength

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44
Q

Which vitamin is particularly important for bone growth in children?

A

Vitamin A

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45
Q

Which 2 vitamins are required for synthesis of protein in normal bone?

A

Vitamin B12 and Vitamin K

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46
Q

Which 2 hormones are essential for stimulating bone growth and what structures produce them?

A

Growth hormone - produced by pituitary gland
Thyroxine - produced by thyroid gland

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47
Q

Growth hormone stimulates…

A

Protein synthesis and cell growth throughout the body

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48
Q

Thyroxine stimulates…

A

Cell metabolism and increases the rate of osteoblast activity

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49
Q

Growth hormone and thyroxine maintain normal activity at ____ until____

A

At epiphyseal cartilages until puberty

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50
Q

At puberty, the levels of which hormones rise?

A

Sex hormones - estrogens in females and androgens in males

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51
Q

What do sex hormones do?

A

Stimulate osteoblasts to produce bone faster than the rate at which epiphyseal cartilage expands. Over time, the cartilage narrows and eventually closes

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52
Q

What accounts for variations in body sizes and proportions?

A

Differences in male and female sex hormones

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53
Q

Why are women generally shorter than men at maturity?

A

Estrogens cause faster epiphyseal closure than androgens

54
Q

What other 2 hormones (besides sex hormones, growth hormone, and thyroxine) help with bone?

A

Calcitonin and parathyroid hormone

55
Q

What produces calcitonin?

A

Thyroid gland

56
Q

What produces the parathyroid hormone?

A

Thyroid gland

57
Q

What do the parathyroid hormone and calcitonin do for the bone?

A

Homeostatic control of calcium and phosphate levels in body fluids

58
Q

Even after death, what information could be determined just by examining their skeleton?

A

Sex, lifestyle, environmental conditions,physical stresses, health and diet, hormonal deficiencies

59
Q

Why would you expect the arm bones of a weight lifter to be thicker and heavier than those of a jogger?

A

The larger arm muscles of the weight lifter would provide more mechanical stresses to the bones of the upper limbs. In response to that stress, bones would grow thicker

60
Q

A child who enters puberty several years later than the average age is generally taller than average as an adult. Why?

A

Growth continues throughout childhood. At puberty, a growth spurt occurs and is followed by closure of the epiphyseal cartilages. The later puberty begins, the taller the child will be when the growth spurt begins, so the taller the individual will be when the growth is completed

61
Q

A 7 year old child has a pituitary gland tumor involving the cells that secrete Growth Hormone, resulting in increased levels of growth hormone. How will this condition affect the child’s growth?

A

This will result in excessive bone growth (because the child is prepubescent) making the child taller

62
Q

A chemical analysis of bone reveals it is important as a ____ _____

A

Mineral reservoir

63
Q

What is the most abundant mineral in the human body?

A

Calcium

64
Q

Nearly 99% of calcium is deposited in the…

A

Skeleton

65
Q

Calcium ions are particularly important in which 2 kinds of cells?

A

Muscle cells and neurons

66
Q

In which muscle cells is calcium particularly important?

A

Cardiac muscle cells

67
Q

If the calcium concentration of body fluids increases by 30%, what happens to neurons and muscle cells??

A

They become unresponsive

68
Q

If calcium levels DECREASE by 35%, what happens to neurons?

A

They become so excited that convulsions can occur

69
Q

A 50% reduction in calcium concentration generally results in…

A

Death

70
Q

Which 2 hormones with opposing effects maintain calcium homeostasis?

A

Parathyroid hormone and calcitonin

71
Q

Parathyroid hormone and calcitonin coordinate the ____,_____, and ____ of calcium ions

A

Storage, absorption, and secretion

72
Q

What are the 3 target sites of the parathyroid hormone and calcitonin? What is the function of each in relation to calcium?

A

The bones (calcium storage)
Digestive tract (absorption)
Kidneys (excretion)

73
Q

What gland secretes calcitonin?

A

The thyroid gland

74
Q

What gland secretes the parathyroid hormone?

A

The parathyroid gland

75
Q

What causes the parathyroid gland to secrete the parathyroid hormone?

A

When plasma calcium ion concentration falls below 8.5mg/dL

76
Q

What effect does the parathyroid hormone have on the bones, intestines, and kidneys?

A

Parathyroid hormone is secreted when plasma calcium ion concentrations are low. Therefore, the hormone stimulates osteoclasts to release stored calcium ions, the intestines to increase their rate of absorption, and the kidneys to retain their calcium ions

77
Q

What causes the thyroid gland to secrete calcitonin?

A

When plasma calcium ion concentration rise above 11mg/dL

78
Q

What specific cells in the thyroid gland secrete calcitonin?

A

Parafollicular cells (C cells)

79
Q

What effect does calcitonin have on the bone, intestines, and kidneys?

A

Calcitonin is secreted due to high calcium ion concentrations. Therefore, it inhibits osteoclasts while osteoblasts continue to lock calcium ions into bone matrix. In the intestines, the rate of intestinal absorption decreases. Kidneys allow calcium ion loss through the urine

80
Q

Where in the body are parathyroid glands?

A

In the neck

81
Q

Does the parathyroid hormone stimulate activity of osteoclasts or osteoblasts?

A

Mostly stimulates osteoblasts to release stored calcium ions from bone, but it does stimulate osteoblast activity to a lesser degree

82
Q

How does the parathyroid hormone increase the rate of intestinal absorption when calcium levels are low?

A

By ENHANCING the action of calcitriol

83
Q

Calcitonin ______ osteoclast activity

A

Inhibits

84
Q

In both situations (when calcium ion concentration is low and high), what hormone controls intestinal absorption??

A

CALCITRIOL. When calcium ion concentration is low, calcitriol is ENHANCED to stimulate faster absorption. When calcium ion concentration is HIGH, LOW levels of calcitriol reduce the rate of absorption

85
Q

When calcium levels are high, calcitriol stimulates a ______ in the rate of intestinal absorption

A

Decrease

86
Q

When calcium levels are low, calcitriol stimulates a ______ in the rate of intestinal absorption

A

Increase

87
Q

When large numbers of calcium ions are mobilized in body fluids, do the bones become weaker or stronger?

A

Weaker

88
Q

When calcium salts are deposited, do bones become weaker or stronger?

A

Denser and stronger

89
Q

The bone matrix contains ___ ____as well as ___ ____

A

Protein fibers as well as mineral deposits

90
Q

Do changes in mineral content affect the shape of the bone? Why or why not?

A

No because the bone matrix doesn’t just contain mineral deposits but protein fibers as well

91
Q

What structure plays a primary role in the homeostatic maintenance of normal calcium ion concentration of body fluids?

A

The skeleton

92
Q

What is the condition called when bones appear normal but are weak and flexible due to poor mineralization?

A

Osteomalacia

93
Q

_____ is a form of _____ affecting children

A

Rickets is a form of osteomalacia affecting children

94
Q

Rickets is the result of….

A

Vitamin d3 deficiency caused by inadequate exposure to sunlight and dietary supplement of the vitamin

95
Q

Why are the bones of children with rickets so flexible?

A

Lack of sufficient mineralization

96
Q

In rickets, how do the bones bend? Why?

A

Laterally because the walls of the femur can’t resist the compression forces applied

97
Q

In the US, what drink is fortified with vitamin d3 specifically to prevent rickets

A

Homogenized milk

98
Q

Most fractures heal even after severe damage provided that….

A

The blood supply and the cellular components of the periosteum and endosteum survive

99
Q

In even small fractures, many ____ are broken and extensive _____ occurs

A

Many blood vessels are broken and extensive bleeding occurs

100
Q

Another name for “large blood clot”

A

Fracture hematoma

101
Q

What does a fracture hematoma (large blood clot) do?

A

Closes off the injured vessels and leaves a fibrous meshwork in the damaged area

102
Q

The disruption of circulation from a fracture does what?

A

Kills osteocytes around the fracture which broadens the area affected

103
Q

What does dead bone do in the 1st step of a fracture healing process?

A

Dead bone extends along the shaft in either direction from the break

104
Q

In adults, the cells of the periosteum and endosteum are generally ______

A

Inactive

105
Q

When a fracture occurs, what do cells of the intact endosteum and periosteum do?

A

They undergo rapid cycles of cell division and the daughter cells migrate to the fracture zone

106
Q

Where does an external callus form? What is it made of?

A

External callus is made up of an enlarged collar of cartilage and bone. It encircles the bone at the level of fracture

107
Q

Where does an internal callus form?

A

Within the medullary cavity and between the broken ends of the shaft

108
Q

At the center of the external callus, cells differentiate into ______ and produce blocks of _______

A

Osteoblasts and produce blocks of hyaline cartilage

109
Q

At the edges of both the internal and external callus, cells differentiate into ______ and begin creating a ______

A

Osteoblasts and begin creating a bridge between the bone fragments on either side of the fracture to temporarily stabilize the broken ends

110
Q

As the repair continues, osteoblasts replace the central cartilage of with external callus with…..

A

Spongy bone

111
Q

Osteoclasts and osteoblasts continue to remodel the region of the fracture for a period ranging from ___ to ____

A

4 months to well over a year

112
Q

In what stage of fracture repair can a cast be removed?

A

3rd stage

113
Q

At which point in fracture repair would you expect to find an external callus?

A

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.  

114
Q

The bones of the skeleton become _____ and _____ as a normal part of the aging process

A

Thinner and weaker

115
Q

Inadequate ossification is called _______

A

Osteopenia

116
Q

All of us become slightly _____ as we age

A

Osteopenic

117
Q

Between what ages does osteopenia (reduction of bone mass) begin?

A

30-40 years old

118
Q

Describe osteoblast/osteoclast activity changes as we age

A

Osteoblast activity begins to decline while osteoclasts activity continues at previous levels

119
Q

Once the reduction in bone mass begins, women lose about ____% of their skeletal mass per decade while men lose about ___%

A

Women - 8%/decade
Men - 3%/decade

120
Q

Are all parts of the skeleton equally affected by the reduction of bone mass with age? Explain.

A

NO-all areas are affected differently. Epiphyses, vertebrae, and the jaws lose more mass than other sites, resulting in fragile limbs, reduction of height, and loss of teeth

121
Q

When the reduction in bone mass is sufficient to compromise normal function, the condition is known as….

A

Osteoporosis

122
Q

____ hormones are important in maintaining normal rates of bone deposition.

A

Sex

123
Q

Over age 45, an estimated ____% of women and ____% of men have osteoporosis

A

Women - 29%
Men - 18%

124
Q

In women, when does osteoporosis accelerate?

A

After menopause due to a decline in circulating estrogens

125
Q

Why is severe osteoporosis less common in men under the age of 60 than in women of the same age group?

A

Men continue to produce androgens late in life while women essentially stop producing estrogen after menopause

126
Q

Osteoporosis can also develop as a secondary effect of many…?

A

Cancers

127
Q

Cancers of the bone marrow, breast, or other tissues releases a chemical called…

A

Osteoclast activating factor

128
Q

What does the chemical “osteoclast-activating factor” do?

A

Increases both the number and activity of osteoclasts and produces severe osteoporosis

129
Q

Define osteopenia

A

Osteopenia is inadequate ossification and is common in the aging process. It results as a consequence of decreasing osteoblast activity accompanied with normal osteoclast activity

130
Q

Why is osteoporosis more common in older women than older men?

A

After menopause, the levels of estrogen decrease dramatically. Estrogen is important in moving calcium to the bones. As a result, older women have difficulty replacing the calcium in bones that is being lost due to normal aging. In men, the level of sex hormones (androgens) does not decrease until much later in life.

131
Q

What is estrogen important for in relation to bones?

A

Moving calcium into bones

A&P Exam 2 (19 decks)

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