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Y1S2Anatomy > Gross and microstructure of bone tissue and growth part 2 > Flashcards

Gross and microstructure of bone tissue and growth part 2 Flashcards

1
Q

Why d we bleed a lot if we fractured a bone?

A

Because bones have a rich blood supply as it is an active tissue

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2
Q

Where is the bone matric found?

A

Between the cells of the bone

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3
Q

What surround the bone?

A

Periosteum

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4
Q

What is the difference between primary and secondary bone?

A

Primary bone are immature while secondary are mature

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5
Q

Describe a long bone

A
  • Composed of two epiphysis (proximal and distal) and a shaft (diaphysis)
  • Between a diaphysis and a epiphysis is a metaphysis
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6
Q

What is a metaphysis?

A

It is the junction between a epiphysis and a diaphysis

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7
Q

What is the main difference in the structure/composition between the epiphysis and diaphysis?

A

Epiphysis along with the metaphysis are made of spongy bone while the diaphysis are made of compact bone

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8
Q

What are the two linning found in long bones?

A

1) Periosteum (covers the outside of the diaphysis)

2) Endosteum (covers the canal from inside)

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9
Q

What binds the periosteum to the bone surface?

A

Sharpey’s fibers (strong collagen fibers) covers the external surface of the bone except in their synovial articulations

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10
Q

What is the main function of the periosteum?

A

Bone healing, without it there will be no bone regeneration

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11
Q

What is the medullary cavity?

A

A central cavity within the shaft (diaphysis), which is filled with yellow bone marrow

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12
Q

What are the different types of bone marrow?

A

1) Red bone marrow (site of RBC’s formation), found in spongy bone

2) Yellow bone marrow (site of cartilage, fat and bone formation), found in compact bone

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13
Q

Describe the periosteum

A

Composed of two layers:

1) Outer fibrous

2) Inner cellular (OSTEOGENIC) layer (osteoprogenitor cell) & osteoblasts for bone growth and repair

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14
Q

What are the functions of the periosteum/endosteum?

A

1) Distributes blood vessels to the bone

2) Important for the growth of bone in width (as the cellular layer in the periosteum adds bones from the periphery) and healing

3) Gives muscles attachment (dense sharpeys fibers)

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15
Q

What does the cellular layer of the periosteum contain?

A

Osteoblasts which are bone forming cells as they produce proteins, calcium, etc

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16
Q

What is the blood supply of long bones?

A
  • It has three sets of arteries

1) Epiphyseal artery

2) Periosteal artery

3) Nutrient artery

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17
Q

Where doe the epiphyseal artery enters from?

A

From the epiphysis

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18
Q

Describe the periosteal artery

A

1) Many small periosteal arteries penetrates the periosteum via foramen

2) Branches of these arteries form a rich sinusoidal plexus in the bone marrow, branches from the plexus enters the haversian canal via volkmann canals

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19
Q

Describe the nutrient/diaphyseal artery

A

Pierces the middle of the shaft within the marrow cavity dividing into ascending and descending branches

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20
Q

Describe the simple microscopic structure of the bone

A

1) Cells + 2) Extracellular ground substance = 1) Inorganic matric, 2) Organic matrix

  • 50% of bone is minerals
  • 25% Water
  • 25% Protein
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21
Q

What are the different types of bone cells?

A

1) Osteoprogenitor cells
2) Osteoblasts
3) Osteocytes
4) Osteoclasts

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22
Q

What is the function of the osteoprogenitor cells?

A
  • Spindle-shaped cells derived from embryonic undifferentiated mesenchymal cells
  • Stem cells whose division produces osteoblasts
  • Found in inner layers of the periosteum & endosteum
  • In low O2 tension they might change into chondrogenic cells (cartilage)
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23
Q

What is the function of Osteoblasts?

A
  • large cuboidal basophilic cells with large eccentric nuclei
  • Derived from osteogenic cells under bone morphogenic PROTEIN (BMP) & transforming growth factor-B influence
  • Immature bone cells that secretes organic components of the matrix
  • Found in periosteum and endosteum of active bone
  • Add more bone by the precipitation of proteins, minerals & calcium (trapped from blood), as bone synthesis proceeds the osteoblast becomes completely surrounded by matrix, now known as osteoid, but when that matrix becomes mineralized, it will be an osteocyte
  • Gradually they are surrounded by a newly formed matrix entrapped inside lacunae changing into osteocytes
24
Q

What is the function of osteocytes?

A
  • Mature, star-shaped bone cell that maintains the bone matrix
  • Their cytoplasmic processes communicate via narrow canals called canaliculi
  • Does not divide once locked in their lacuna
25
Q

What is the function of osteoclasts?

A
  • Giant, mobile, Multinucleate cell that secretes acids and enzymes to dissolve the bone matrix
  • Acidophilic cytoplasm (rich with proteolytic enzymes)
  • Present where bony resorption (osteolysis) is required
  • Lies at the bone surface, occupying pits called howships lacunae
  • Multinucleated (because they erode cells), responsible for bone resorption
  • The folds in its surface is called a ruffled membrane
26
Q

Describe the life cycle of bone cells

A

Osteogenic - Osteoblast - Osteocyte (maintains the already formed bone)

27
Q

Where does the osteoclast come from?

A

Blood, they are macrophages that resides in bone tissue

28
Q

What are the different functions of osteoblasts?

A

1) Synthesize bone matrix proteins (osteoid “uncalcified bone matrix”), like type 1 collagen, proteoglycans & glycoproteins

2) Synthesizes bone minerals during early bone formation in the embryo

3) Controls bone formation and mineralization through life

29
Q

What are the hormones that affects the function of osteoblasts?

A

1) Parathormone

2) Growth Hormone

3) Calcitonin

4) Sex hormone

30
Q

Describe the process of bone resorption

A
  • Performed by osteoclasts

1) Secretes:

A) Acids, which decalcify (dematerialize) the inorganic part of the bone

B) Proteolytic enzymes (acid hydrolases, collagenases), which degrades the organic portion of the bone

2) They resorb the organic and inorganic residues of the bone matrix and releases them into connective tissue capillaries

31
Q

What are the different types of bone matrix

A

1) Inorganic (calcified) part

2) Organic (osteoid) part

32
Q

Describe the composition of the inorganic “calcified” part of the matrix

A

1) Comprises 65%of the dry weight of the bone mass

2) Composed of calcium, phosphorus, bicarbonate, citrate, magnesium, potassium & sodium

33
Q

What is the main role of the inorganic matrix of the bone?

A
  • It provides rigidity to the bone
  • Acidity causes the dissolution of salts (decalcification of bone) and the bone becomes flexible
34
Q

Which bone cells secretes the matrix of the bone?

A

Osteoblasts

35
Q
A
36
Q

Describe the composition of the organic part of the matrix (osteoid part)

A

1) Collagen fibers (forms about 35% of the dry bone weight, of which 95% of it is type I collagen

2) Glycosaminoglycans (chondroitin sulfate & keratin sulfate), acts as a ground substance

3) Osteocalcin & osteopontin (glycoproteins)

4) Sialoprotein (matrix protein “glue”, binds bone cells to the bone matrix)

37
Q

How does diabetes/renal failure/chronic respiratory diseases result in bone resorption?

A

Because it causes acidity (low pH) of the blood, which results in bone resorption, as it mobilizes the calcium & phosphorus from the bone to the blood leaving only the protein behind making it soft and flexible (now called an osteoid)

38
Q

Describe bone remodeling

A

Bones are constantly remodeled for growth and to alter its structural makeup to adapt to environmental stresses throughout life, this phenomenon is controlled by several factors like hormones (calcitonin & PTH), age, nutrition, exposure to the sun, and physical activity

39
Q

Describe wolff’s law

A

Wolffs law states that bone grows/remodels in response to the factors which acts upon it, for example applying pressure results in bone resorption while applying tension results in bone formation

40
Q

What is the difference between osteoporosis and osteopetrosis?

A

Osteoporosis is and increase in resorption and decrease in deposition, while osteopetrosis is an increase in deposition while a decrease in resorption

41
Q

How are bones classified?

A

1) By shape (flat, irregular, long, short, sesamoid, pneumatic, etc)

2) By the amount of solid mass (compact, spongy “cancellous”)

3) By the microscopic observation (Primary “immature woven”, secondary “mature” lamellar bone)

42
Q

Describe a compact bone

A
  • Solid mass of bone tissue without spaces
  • Provides strength for weight bearing
  • Its cells are organized in osteons
  • Present in shafts of long bones, outer covering of flat bones and vertebrae & the outer and inner tables of the skull
43
Q

Describe a spongy (cancellous) bone

A
  • Consists of trabeculae (spicules) instead of osteons, which are lamellae that are arranged as rods containing red-bone marrow and blood vessels between the trabeculae
  • The trabeculae are formed of osteocytes and are surrounded by osteoblasts
  • Present in the end of long bones, ribs, sternum, bodies of vertebrae, and young embryonic bone
44
Q

Describe a primary bone that is classified microscopically

A
  • It is immature, temporary, developing, woven bone
  • It is the first temporary bone produced during fetal life and after bone repair
  • Contains randomly arranged osteocytes and type 1 collagen bundles
  • Contains low minerals
  • Replaced by secondary bone except in the teeth sockets, near suture lines in the skull bones and where tendons insert in bones
45
Q

Describe a secondary bone as classified by the microscope

A
  • Bone of adults being spongy or compact
  • Contains a calcified matrix arranged in regular osteons (in compact) and trabeculae (in spongy) bones
46
Q

What is the contents of the compact bone (like the diaphysis of long bones)

A

1) Haversian system (osteons), long cylinders that runs parallel to the long axis of the diaphysis, this system is composed of 4-20 lamellae surrounding a central haversian canal that contains blood vessels and loose connective tissue, they are interconnected horizontally by volkmans canals that also connects the periosteum and endosteum carrying the neurovascular supply

47
Q

Describe the process of bone development (ossification, osteogenesis, histogenesis of bone)

A
  • Bone develops by replacing preexisting connective tissue (meaning that it is derived from mesenchyme)
  • There are two ways of bone development:

1) Intramembranous

2) Endochondral ossification

  • The newly formed bone is called a primary bone which is later resorbed and replaced by secondary bone
48
Q

Describe the process of intramembranous ossification

A
  • Most flat bones

1) Mesenchymal cells

1a) osteoblasts

1b) beginning of ossification

1c) spongy bone

2a) fibroblasts

2b) collagen fibers

2c) membrane (model)

2) C.T on the surface of developing bones develops the periosteum

3) Ossification of the membrane begins in the center

4) Osteoblasts in the periosteal membrane forms 2 thin layers of compact bone covering the spongy bone

Mesenchyme - osteogenic - osteoblast - ossification then traps calcium

49
Q

What is the difference between the ossification process of intramembranous and endochondral?

A

Endochondral is in long bones, when the mesenchymal cells become hyaline cartilage and then bone via calcium precipitation while intramembranous is directly without hyaline from the mesenchyme

50
Q

What are the bones that develops via intramembranous ossification?

A

1) Bones forming the roof of the skull (vault)

2) Facial bones (maxilla & mandible)

3) Clavicle

4) Scapula

51
Q

Describe the process of intramembranous ossification in a different way

A
  • First laid bone is cancellous in nature, while later in life the bone becomes compact and there will be a reduction in the size of the marrow spaces and unwanted trabeculae

1) A 1yr ossification center appears in the fibrous connective tissue membrane

2) Bone matrix (osteoid) is secreted within the connective tissue membrane

3) Formation of immature bone and periosteum

4) Formation of bone collar of compact bone and appearance of red marrow

52
Q

describe the process of endochondral ossification

A

1) Undifferentiated mesenchymal cells will give:

1) Fibroblasts - collagen fibers - connective tissue remodeling

2) Chondroblasts - hyaline cartilage - connective tissue remodeling

3) Osteoblasts + blood vessels for ossification to begin

  • Osteoblasts develops beneath the perichondrium of pattern where their mineralization causes degeneration of cartilage tissue opening holes
  • Blood vessels invades the degenerating cartilage tissue to nourish the osteoblasts as they begin to ossify the model producing spongy bone
53
Q

Which cartilage is responsible for the growth in length pf the long bones?

A

Epiphyseal cartilage

54
Q

Which bone structure is responsible for the growth of the bone width?

A

Periosteum

55
Q

How does the bone grows in width?

A

1) Ridges in the periosteum creates a groove for the periosteal blood vessels

2) Periosteal ridges fuses forming an endosteum-lined tunnel

3) Osteoblasts in the endosteum build new concentric lamellae inwards and towards the center of the tunnel forming a new osteon

4) Bone grows outwards as the osteoblasts in the periosteum build new circumferential lamellae

Y1S2Anatomy (18 decks)

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