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Histology Block 3 > Bone > Flashcards

Bone Flashcards

1
Q

What types of tissues does a bone contain?

A

Bone tissue, connective tissues, hematopoietic tissue, adipose, blood vessels and nerves

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2
Q

What are the classifications of bones by shape?

A

Long, short, flat, and irregular bones

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3
Q

What is the endosteum?

A

The layer of osteoprogenitor bone cells lining the marrow cavity

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4
Q

What is the layer of dense fibrous connective tissue lining the outer surface of bone?

A

Periosteum

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5
Q

What are Sharpey’s fibers?

A

Where ligaments and tendons attach to a bone, the collagen fibers of the periosteum extend into the circumferential lamellae

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6
Q

What makes up the bone matrix?

A

Inorganic- mainly crystalline mineral salts and calcium in the form of hydroxyapatite; organic- mainly composed of Type I collagen

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7
Q

How is inorganic bone matrix laid down?

A

Initially laid down as unmineralized osteoid. Mineralization begins with the secretion of alkaline phosphatase

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8
Q

How are collagen fibers arranged within bone tissue? Why is this important?

A

Arranged in a twisting spiral column– important because the column is the strongest structure that can be built, and the spiral nature makes it stronger and able to resist twisting force

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9
Q

What are the two structural types of bone?

A

Compact and spongy (trabecular)

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10
Q

What are the different bone cells?

A

Osteoprogenitor cells, osteoblasts, osteoclasts, and osteocytes

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11
Q

What are lacunae?

A

The holes osteocytes live in

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12
Q

What structures connect lacunae?

A

Canaliculi

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13
Q

From what cells are osteoprogenitor cells derived? Where can the osteoprogenitors be found? What activates their differentiation in to osteoblasts?

A

Mesenchymal stem cells in the marrow; Found in innermost layer of periosteum and the endosteum; CBFA1 transcription factor

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14
Q

What type of bone cells produce type I collagen and bone matrix proteins and respond to mechanical stimuli to mediate bone growth and remodeling?

A

Osteoblasts

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15
Q

What is the name of newly formed bone matrix secreted by osteoblasts?

A

Osteoid

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16
Q

Which are the mature cells of bone tissue? How do they communicate with one another?

A

Osteocytes- have long processes that pass through canaliculi and form gap junctions with other osteocytes

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17
Q

Which bone cells are responsible for bone matrix resorption? From what cells are they derived?

A

Osteoclasts; Formed by the fusion of mononuclear hemopoietic progenitor cells that forms a syncitium

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18
Q

How will bone undergoing resorption appear?

A

Ruffled border with a clear zone

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19
Q

How do osteoclasts mediate bone resorption?

A

They are filled with hydrolytic enzyme-containing lysosomes; first demineralize the matrix by secreting H+ ions, release carbonic anhydrase to break down the fibrous portion; resorption releases calcium and phosphorus through the basolateral membrane and into circulation

20
Q

How is compact bone structurally organized?

A

Organized into Haversion systems connected via Volkman’s canals

21
Q

What is an osteon?

A

A unit of compact bone structure consisting of concentric lamella surrounding a Haversion canal

22
Q

What is contained within the Haversian canals?

A

Blood vessels, lymphatics, and connective tissue

23
Q

What fills compact bone in between adjacent osteons?

A

Interstitial lamellae

24
Q

What type of lamellae surround the entire bone?

A

Circumferential lamellae

25
Q

Which hormones increase bone resorption?

A

Parathyroid hormone, glucocorticoids, and thyroid hormone

26
Q

Which hormones decrease bone resorption?

A

Calcitonin and gonadal steroids

27
Q

Which hormones increase bone formation? Decreae?

A

Growth hormone, vitamin D metabolites, gonadal steroids, calcitonin; Decreased by glucocorticoids

28
Q

What is the basic process of endochondral bone formation? In what type of bone is this process more likely to occur?

A

Blood vessels bring osteoprogenitor cells to hyaline cartilage. The cells calcify the cartilage, killing the chondrocytes, and replacing the cartilage with bone tissue; Most frequently happens with long bone growth

29
Q

What zones form during endochondral ossification and what is happening at each zone?

A

Zone of prolifration– cartilage cells undergoing division, organized into columns; Zone of hypertrophy- chondrocytes are metabolically active and secreting VEGF; Zone of calcified cartilage- chondrocytes begin to degenerate and cartilage matrix is calcified; Zone of resportion- calcified cartilage is resorped and replaced with osteoprogenitor cells

30
Q

True or False: Growth occurs on both sides of the growth plate?

A

True

31
Q

Where does primary ossification occur?

A

In the diaphysis

32
Q

What is the epiphyseal plate?

A

The cartilage zone left at each end of the marrow cavity

33
Q

In which direction does appositional growth occur?

A

Circumferentially– makes bone thicker

34
Q

Where does intramembranous ossification occur? What is the basic process?

A

Occurs in flat bones; embryonic mesenchyme condenses and ossification occurs in numerous sites simultaneously

35
Q

True or False: Only spongy bone can be formed via intramembranous ossification?

A

False- both compact and spongy can

36
Q

What is the effect of the mechanical stress of exercise on bone density?

A

Increases

37
Q

What are the general steps of fracture repair?

A

Hematoma formation, fibrocartilagenous callus formation, bony callus formation, bone remodeling

38
Q

What cellular activity occurs in fracture repair?

A

1) neutrophils and macrophages clean up 2) fibroblasts and capillaries proliferate 3) loose connective tissue is formed 4) cartilage forms in parts 5) dense ct and cartilage form callus 6) osteoprogenitors within the periosteum divide and differntiate, 7) callus is replaced with bone

39
Q

What is a stress fracture?

A

A tiny fracture in a bone caused by overuse or repetitive activity

40
Q

What bone disease is charecterized by low bone mass and deterioration of both the inner and outer parts of bone, which can lead to bone fragility and fractures?

A

Osteoporosis

41
Q

What are the potential consequences of osteoporosis?

A

Vertebral fractures that can lead to decreased height or scoliosis, hip fractures, minimal stress fractures, loss of bone in the jaw (teeth loss or movement)

42
Q

What are the risk factors for osteoporosis?

A

Female, caucasian/asian, post menopause, thin and small body frames, family history, smoking, EtOH comsumption, lack of exercise, low calcium

43
Q

How do bisphosphonates work?

A

They are antiresorptive agents that bind to hydroxyapatite crystals and inhibit osteoclasts

44
Q

What is the cause of osteogenesis imperfecta?

A

Mutations affecting the synthesis or structure of collagen type I

45
Q

What are the classic symptoms of osteogenesis imperfecta?

A

Blue tint to eye sclera, multiple bone fractures, early hearing loss

Histology Block 3 (5 decks)

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