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Biology - Chapters 1 - 10 > Chapter 6 - Skeletal: Bone Tissue > Flashcards

Chapter 6 - Skeletal: Bone Tissue Flashcards

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0
Q

What process does bone tissue continually engage in?

A

Remodelling - construction of new bone tissue and breaking down of old bone tissue

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1
Q

What tissues is bone composed of? (6 kinds)

A
  1. Bone (osseous) tissue. 2. Cartilage
  2. Dense connective tissue. 4. Epithelium
  3. Adipose tissue. 6. Nervous tissue
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2
Q

What are the six main functions of the skeletal system?

A
  1. Support
  2. Protection
  3. Assistance in movement
  4. Mineral homeostasis (storage and release)
  5. Blood cell production (red bone marrow)
  6. Triglyceride storage (yellow bone marrow)
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3
Q

Describe the role of bones in blood cell production.

A

In certain bones, a connective tissue called red bone marrow produces red blood cells, white blood cells and platelets.

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4
Q

Which bones contain red blood marrow?

A

The hip (pelvic) bones, ribs, sternum (breastbone), vertebrae (backbone), skull and end of the bones in the humerus (arm) and femur (thigh) bones.

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5
Q

How do red bone marrow and yellow bone marrow differ in composition and function?

A

Yellow bone marrow consists mainly of adipose cells, which store triglycerides. The stored triglycerides are a potential chemical energy reserve. Red bone marrow produces red, white and platelet cells.

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6
Q

What 7 parts does a long bone consist of? Describe them.

A
  1. Diaphysis - bones shaft or body
  2. Epiphyses - proximal and distal ends of the bone
  3. Metaphyses - between the diaphysis and epiphyses. Contains a growth plate (epiphyseal plate). When a bones ceases to grow in length, the growth plate is replaced with bone resulting in an epiphyseal line.
  4. Articular cartilage - thing layer of hyaline cartilage covering the part of the epiphysis where the bone forms a joint with another bone.
  5. Periosteum - tough connective tissue sheath. Some of the cells allow the bone to grow in width but not length. Protects the bone, assist in fracture repair, help nourish bone tissue and serves as an attachment point for ligaments and tendons.
  6. Medullary cavity - a hollow cylindrical space within the diaphysis that contains fatty yellow bone marrow and numerous blood vessels
  7. Endosteum - thin membrane that lines the medullary cavity. Contains a single layer of bone forming cells and small amount of connective tissue
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7
Q

Why is bone tissue classified as a connective tissue?

A

Contains an abundant extracellular matrix that surrounds widely separated cells. (15% water, 30% collagen fibres, 55% crystallized mineral salts.

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8
Q

What is hydroxyapatite?

A

When calcium phosphate is combined with calcium hydroxide to form crystals of hydroxyapatite

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9
Q

What is calcification?

A

As hydroxyapatite crystals form they combine with other minerals (such as calcium carbonate, magnesium, fluoride, potassium and sulfate). Then these mineral salts are deposited in the framework formed by the collagen fibres of the extracellular matrix, they crystallize and harden.

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10
Q

What bone building cells initialize calcification?

A

Osteoblasts

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11
Q

What does the bones hardness depend on? It’s flexibility?

A

Hardness –> crystallized inorganic mineral salts

Flexibility –> collagen fibres, provide tensile strength

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12
Q

What four types of cells are present in bone tissue?

A
  1. Osteogenic cells
  2. Osteoblasts
  3. Osteocytes
  4. Osteoclasts
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13
Q

What are osteogenic cells?

A

Unspecialized bone stem cells derived from mesenchyme, only bone cells that undergo cell division - resulting cells develop into osteoblasts. Found along inner portion of the periosteum, in the endosteum and in the canals within bone that contain blood vessels

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14
Q

What are osteoblasts?

A

Bone building cells. Do NOT undergo cell division.
Synthesize and secrete collagen fibres and other organic components needed to build the extracellular matrix.
As osteoblasts surround themselves with extracellular matrix, they become trapped and become osteocytes.

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15
Q

What are osteocytes?

A

Mature bone cells. Main cells in bone tissue.
Maintains daily metabolism, such as exchange of nutrients and wastes with the blood.
Do NOT undergo cell division

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16
Q

What are osteoclasts?

A

Are huge cells derived from the fusion of as many as 50 monocytes (at type of white blood cell) and are concentrated in the endosteum. These cells breakdown the extracellular matrix (resorption) as a normal part of development, maintenance and repair

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17
Q

What is compact bone tissue?

A

The strongest form of bone tissue b/c it contains few spaces.
Found beneath the periosteum of all bones and makes up the bulk of the diaphyses of long bones.

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18
Q

What structural unit make up compact bone tissue?

A

Osteons (harvsian systems).

Each osteon consists of concentric lamellae arranged around a central canal. (Resembles growth rings on a tree)

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19
Q

What are concentric lamellae?

A

Circular plates of mineralized extracellular matrix of increasing diameter, surrounding a small network of blood vessels, lymphatics and nerves located in the central canal.

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20
Q

What are lacunae?

A

Small spaces between the concentric lamellae, which contain osteocytes.

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21
Q

What are canaliculi?

A

Small channels radiating from the lacune, which are filled with extracellular fluid. Inside the canaliculi are slender finger like projections of osteocytes

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22
Q

What are interstitial lamellae?

A

Areas between neighbouring osteons.
Also have lacunae with osteocytes and canaliculi
Fragments of older osteons that have been partially destroyed during bone rebuilding or growth.

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23
Q

What are perforating canals?

A

Canals that allow blood vessels, lymphatic vessels and nerves from the periosteum to penetrate the compact bone

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24
Q

What are circumferential lamellae?

A

Arranged around the entire outer and inner circumference of the shaft of a long bone.
Developed during initial bone formation.
Connected to the periosteum by perforating fibres.

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25
Q

What is spongy bone tissue?

A

Always located in the interior of a bone, protected by compact bone.
Does not contain osteons.
Consists of lamellae arranged in an irregular pattern of thin columns of trabeculae.
Between the trabeculae are tiny spaces filled with red bone marrow or yellow bone marrow.

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26
Q

What does each trabeculae consist of?

A

Concentric lamellae, osteocytes that lie in the lacunae and canaliculi that radiate outward from the lacunae

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27
Q

How is spongy bone different from compact bone?

A
  1. Spongy bone tissue is light

2. Trabeculae support and protect red bone marrow (where hemopoiesis occurs)

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28
Q

What are periosteal arteries?

A

Small arteries accompanied by nerves, enter the diaphysis through many perforating canals and supply the periosteum and outer part of the compact bone

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29
Q

What is the nutrient foramen?

A

A hole in compact bone through which the nutrient artery passes.

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30
Q

What happens to the nutrient artery once it enters the medullary cavity?

A

Divides into proximal and distal branches that course toward each end of the bone. These branches supply both the inner part of compact bone tissue of the diaphysis and the spongy bone tissue and red bone marrow as far as the epiphyseal plates (or lines). Some bones only have one nutrient artery (tibia) and some have many (femur).

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31
Q

Which arteries supply the ends of the long bones?

A

Metaphyseal and epiphyseal arteries.

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32
Q

How does the metaphyseal arteries enter the bone?

A

Enter the metaphyses of a long bone and together with the nutrient artery, supply the red bone marrow and bone tissue of the metaphyses.

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33
Q

How does the epiphyseal arteries enter the bone?

A

Enter the epiphyses of a long bone and supply the red bone marrow and bone tissue of the epiphyses.

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34
Q

Where are veins that carry blood away from the long bones evident?

A
  1. One or two nutrient veins that accompany the nutrient artery (diaphysis)
  2. Numerous epiphyseal veins and metaphyseal veins accompany their respective arteries
  3. Many small periosteal veins accompany their respective arteries and exit through the periosteum
35
Q

Why does it hurt to have a bone marrow needle biopsy?

A

There are many nerves and pain receptors in the periosteum that are especially sensitive to rips and/or tears

36
Q

What is ossification? (Also called osteogenesis)

A

The process by which bone forms

37
Q

In what 4 principal situations does bone grow?

A
  1. Initial formation of bones in an embryo and fetus
  2. Growth of bones during infancy, childhood and adolescence
  3. Remodelling of bone (replacement of old bone throughout lifetime)
  4. Repair of fractures
38
Q

What are the two kinds of bone formation in an embryo and fetus?

A
  1. Intramembranous ossification - bone forms directly within mesenchyme, which is arranged in sheet like layers that resemble membranes
  2. Endochondral ossification - bone forms within hyaline cartilage that develops from mesenchyme
    * both involve replacement of preexisting connective tissue with bone, do not lead to differences in the structure of mature bone
39
Q

What are the steps involved with intramembranous ossification?

A
  1. Development of the ossification center
  2. Calcification
  3. Formation of trabeculae
  4. Development of the periosteum
40
Q

Which bones are formed by intramembranous ossification?

A

Flat bones of the skull
Most facial bones
Mandible (lower jawbone)
Medial part of the cavicle (collar bone)

41
Q

What are the steps involved with endochondral ossification?

A
  1. Development of cartilage model
  2. Growth of cartilage model
  3. Development of primary ossification center
  4. Development of the medullary cavity
  5. Development of secondary ossification center
  6. Formation of articular cartilage and the epiphyseal (growth) plate
42
Q

What is appositional (exogenous) growth?

A

Growth at the outer surface.

Increase in thickness of bones during ossification

43
Q

What is interstitial (endogenous) growth?

A

Growth from within.

Increase in length of bones during ossification

44
Q

What is the main difference between the primary and secondary ossification centres?

A

Primary proceeds inward. Secondary proceeds outward.

Primary develops medullary cavity, secondary does not.

45
Q

The growth of long bones involves what two major events?

A
  1. Interstitial growth of cartilage on the epiphyseal side of the epiphyseal plate
  2. Replacement of cartilage on the diaphyseal side of the epiphyseal plate with bone by endochondral ossification
46
Q

The epiphyseal plate is a layer of hyaline cartilage in the metaphysis of a growing bone that consists of what 4 zones?

A
  1. Zone of resting cartilage (anchor plate to epiphysis)
  2. Zone of proliferating cartilage (interstitial growth)
  3. Zone of hypertrophic cartilage (maturing chondrocytes)
  4. Zone of calcified cartilage (dead chondrocytes, b/c the extracellular matrix has calcified. Osteoclasts dissolve the calcified cartilage and osteoblasts and capillaries from the diaphysis invade the area)
47
Q

What happens if a bone fracture damages the epiphyseal plate?

A

The fractured bone may be shorter than normal once adult stature is reached. This is b/c damage to cartilage, which is avascular, accelerates closure of the epiphyseal plate due to cessation of cartilage cell division

48
Q

Describe the four steps involved with bone growth (in thickness)?

A
  1. Ridges in periosteum create groove for periosteal blood vessel
  2. Periosteal ridges fuse, forming and endosteum-lined funnel
  3. Osteoblasts in endosteum build new concentric lamellae inward toward center of tunnel, forming a new osteon
  4. Bone grows outward as osteoblasts in periosteum build new circumferential lamellae. Osteon formation repeats as new periosteal ridges fold over blood vessels
49
Q

What is the difference between bone remodelling, bone resorption and bone deposition?

A

Bone remodelling - ongoing replacement of old bone tissue with new
Bone resorption - removal of minerals and collagen fibres from bone by osteoclasts
Bone deposition - addition of minerals and collagen fibres to bone by osteoblasts

50
Q

What are the renewal rates of compact and spongy bone tissue per year?

A

Compact - 4% per year

Spongy - 20% per year

51
Q

What are the other benefits of remodelling?

A

If newly formed bone is subjected to heavy loads, it will grow thicker and stronger.
The shape if a bone can be altered for proper support based on the stress patterns experienced during the remodelling process.
New bone is more resistant to fracture than old bone

52
Q

How does bone resorption occur?

A

An osteoclast attaches tightly to the bone surface at the endosteum or periosteum and firms a leakproof seal at the edge of the ruffled border.
It releases protein-digesting lysosomal enzymes and several acids into the sealed pocket.
The enzymes digest collagen fibres and other organic substances while acids dissolve bone minerals.
Carve out a small tunnel in the bone
Degraded bone proteins and extracellular matrix minerals enter an osteoclast by endocytosis, cross the cell in vesicles and undergo exocytosis on the side opposite the ruffled border.
Now in the interstitial fluid, the products of bone reabsorption diffuse into nearby blood capillaries.
Once a small area of bone has been resorbed, osteoblasts move in to rebuild the bone in that area.

53
Q

What is othodontics?

A

Branch of dentistry concerned with the prevention and correction of poorly aligned teeth.
Braces place artificial stress on teeth that osteoclasts and osteoblasts remodel the tooth to alleviate the stress.

54
Q

What is Paget’s disease?

A

An excessive proliferation of osteoclasts so that bone resorption occurs faster than bone deposition.
Osteoblasts attempt to compensate.
But new bone is weaker, b/c it has a higher proportion of spongy bone, mineralized is decreased and newly synthesized extracellular matrix contains abnormal proteins.
New bones are hard, brittle and fracture easily.

55
Q

What factors affect bone growth and remodelling?

A
  1. Minerals (calcium, phosphorus, magnesium, fluoride, and manganese)
  2. Vitamins (A stimulates osteoblasts, C needed for synthesis of collagen, D increases the absorption of calcium from food)
  3. Hormones (IGF’s [insulinlike growth factors], hGH [human growth hormone], thyroid hormones)
56
Q

What causes growth to shut down (in length)?

A

During puberty, estrogen and androgen are responsible for the “growth spurt”. Ultimately, sex hormones, especially estrogen in both sexes shut down growth at epiphyseal (growth) plates, causing elongation of the bones to cease.

57
Q

How does estrogen slow resorption?

A

By promoting apoptosis (programmed death) of osteoclasts

58
Q

What is giantism?

A

A person is much taller and heavier than normal. Caused by over secretion of hGH during childhood

59
Q

What is pituitary dwarfism?

A

A person with a short stature. Caused by an under-secretion of hGH during childhood. Can be treated with hGH until the epiphyseal plate closure. Proportionate sized limbs.

60
Q

What is acromegaly?

A

Over secretion of hGH during adulthood, cannot produce lengthening of bones b/c growth plates are sealed. It does cause the hands, feet and jaws to thicken and other tissues enlarge.

61
Q

What is achondroplasia?

A

Inherited condition in which the conversion of cartilage to bone is abnormal. Results in achondroplasic dwarfism. Results in short limbs, slightly enlarged head with a prominent forehead and flattened nose. Condition is untreatable.

62
Q

What is a fracture?

A

Any break in a bone

63
Q

What is a stress fracture?

A

A series of microscopic fissures in bone that forms without any evidence of injury to other tissues.
Result from repeated, strenuous activity such as running, jumping, or aerobic dancing.
Standard x-Rays often fail to reveal them, but bone scans show them.

64
Q

What are the different types of fractures? (6)

A
  1. Open (compound) - broken ends protrude through the skin, a closed (simple) does not break the skin
  2. Comminuted - bone is splintered, crushed
  3. Green stick - partial fracture, only occurs in children, one side is broken, the other side is bent.
  4. Impacted - one end of the fractured bone is forcefully driven into the interior of the other
  5. Pott - fracture of distal end of the lateral leg bone (fibula), with serious injury of the distal tibial articulation
  6. Colles’ - fracture of the distal end of the lateral forearm bone (radius) in which the distal fragment is displaced posteriorly
65
Q

How does treatment of fractures vary?

A

Vary according to age, type and bone involved.

Realignment, immobilization and restoration of function

66
Q

What is reduction?

A

Fractured ends are brought into alignment

“Setting the fracture”

67
Q

What is a closed reduction? An open reduction?

A

Closed - bones are brought into alignment by manual manipulation
Open - brought into alignment by a surgical procedure using internal fixation devices such as screws, plates, pins, rods and wires

68
Q

What are the steps involved in repairing a bone fracture?

A
  1. Formation of fracture hematoma
  2. Fibrocartilaginous callus formation
  3. Bony callus formation
  4. Bone remodelling
69
Q

Why does it take months for a bone to heal?

A

Calcium and phosphorus needed to strengthen and harden new bone are deposited only gradually and bone cells generally grow and reproduce slowly. The temporary disruption in their blood supply also helps explain the slowness of healing of severely fractured bones.

70
Q

How much calcium does bone store for the body?

A

99%

71
Q

How is calcium regulated in the body?

A

By controlling the rate of calcium resorption from bone into blood and of calcium deposition from blood to bone, to keep it in homeostasis

72
Q

What body functions rely on calcium to function properly?

A

Both nerve and muscle cells depend on a stable level of CA+2 in extracellular fluid, blood clotting also requires it.

73
Q

What can happen if the calcium levels go above or below 9-11 mg/100 mL?

A

Concentration too high - heart can stop

Concentration too low - breathing may cease

74
Q

What is the parathyroid hormone (PTH)?

A

Hormone increases calcium levels, secreted by the parathyroid glands, operates via a negative feedback system.

75
Q

Explain the negative feedback system for PTH. (When calcium levels are too low)

A
  1. Stimulus disrupts homeostasis by decreasing calcium level
  2. Parathyroid glands detect lowered calcium concentration
  3. Increased production of cyclic AMP
  4. PTH gene “turned on” by presence of cyclic AMP
  5. Increased release of PTH
  6. PTH increases activity of osteoclasts (bone resorption) and kidneys retain calcium in blood
  7. Increases calcium level in blood
76
Q

What happens if calcium levels are too high?

A

Parafollicular cells in the thyroid gland secrete CT, which inhibit the activity of the osteoclasts, speeds blood calcium uptake by bone and accelerates deposition to bone. CT promotes bone formation and decreases blood level calcium

77
Q

How does exercise and mechanical stress affect bone tissue?

A

When placed under stress, bone has the ability to become stronger through increased deposition of mineral salts and production of collagen fibres by osteoblasts.
Without mechanical stress, bone does not remodel normally b/c bone resorption occurs faster than than bone formation.

78
Q

What impacts bone growth more, walking or running?

A

Running, b/c high-impact intermittent strains more strongly influence bone deposition as compared with lower-impact strains

79
Q

What are the two main mechanical stresses on bones?

A
  1. Pull of skeletal muscles

2. Gravity

80
Q

Why do bones decrease in mass?

A

Bone resorption by osteoclasts outpaces bone deposition by osteoblasts.

81
Q

What are the two principal effects of aging on bone tissue?

A
  1. Loss of bone mass - results from demineralization

2. Brittleness - results from decreased rate of protein synthesis

82
Q

What is osteoporosis?

A

A condition of porous bones.
Bone resorption outpaces bone deposition.
Due to depletion of calcium from the body, more calcium is lost in urine, feces and sweat than is absorbed through diet.

83
Q

What is osteoarthritis?

A

Degeneration of articular cartilage such that bony end touch

84
Q

What is osteomyelitis?

A

An infection of bone characterized by high fever, sweating, chills, pain, nausea, pus formation, edema, and warmth over afflicted bone

85
Q

What is osteopenia?

A

Reduced bone mass due to a decrease in the rate of bone synthesis to a level too low to compensate for normal bone resorption

86
Q

What is osteosarcoma?

A

Bone cancer that affects osteoblasts, occurs most often in teenagers

Biology - Chapters 1 - 10 (10 decks)

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