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MSK > Bone tissue formation > Flashcards

Bone tissue formation Flashcards

1
Q

What is bone?

A

Specialised connective tissue

Complex organ with multiple functiones

Vasculatised - constant exchange with systemic cell population, GF and hormones

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2
Q

What are the roles of bones?

A

Protection and support

Locomotion

Calcium homeostasis and mineral storage

Stem cell niche and hosting of haematopoiesis

Storage of energy

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3
Q

How many bones does an adult skeleton have?

A

206 bones

80 - axial
126 - appendicular

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4
Q

Macroscopic structure of bones

A

Different bones have different specialised shapes according to their function

Living matrix - constant remodelling and adaptation

Variety of forms but similar architecture with varying degrees of specialisation according to mechanical requirements

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5
Q

What are the different types of macroscopic structures bones can have?

A

Flat

Sutural

Short

Irregular

Sesamoid

Long

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6
Q

What does the structure and composition of bones maximise?

A

Maximises strength, stiffness and flexibility of bones

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7
Q

What are the components of long bones?

A

Cortical and trabecular

Mantains stiffness in the longitudinal direction

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8
Q

What are bones covered by?

A

Periosteum

Highly vascularised connective tissue

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9
Q

Describe the cortical component of long bones

A

Dense layer of compact bone around the bone marrow cavity

Found in the middle section of the bone (diaphysis)

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10
Q

Describe the trabecular component of long bones

A

Mesh of intrconnected arches

Highly porous, spongy bone

Found at both ends of the bone (Epiphysis)

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11
Q

What are the epiphyses?

A

The two ends of the long bone

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12
Q

What ensures optimal load bearing in long bones?

A

Combination of cortical, lamellar bone and trabecullae bone

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13
Q

Microscopic structure of bone

A

Dynamic tissue with living composite material

Specialised cells and ECM

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14
Q

What do the organic and structural components of the ECM provide the bone?

A

Tensile strength

Around 10 kg/mm2

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15
Q

What do the inorganic and biomineral components of the ECM provide the bone?

A

Compressive strength

Aroung 15 kg/mm2

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16
Q

Describe the microscopic structure of compact bone

A

Osteon unit

Concentric organisation of lamellar bone

Blood vessels run though Canaliculi, Haversian canal and Volkmann’s canal

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17
Q

What is an osteon unit?

A

Fundamental functional unit of compact bone

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18
Q

What is the Haversian canal?

A

Contains the bone’s nerve and blood supplies

Found inside the osteon

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19
Q

What are bone canaliculi?

A

Microscopic canals that run through bone lacunae (gaps) which carries a structure

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20
Q

What are Volkmann’s canals?

A

Small channels that transmit bloof vessels from the periosteum into the bone

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21
Q

Describe microscopic structure of Trabecular bone

A

Greater surface area that cortical

Suitable for metabolic activity - exchange of calcium

Highly vascular

Frequently contains red bone marrow

Traberculae are aligned towards the distribution of mechanical load

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22
Q

What process happens in the red bone marrow?

A

Haematopoiesis

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23
Q

What cells make up the bone structure?

A

Osteobalsts

Osteocytes

Osteoclasts

24
Q

What is the origin of osteoblasts?

A

Mesenchymal stem cells

25
Q

What are the biomarkers for osteoblasts?

A

Alkaline-phosphatase

Osteocalcin

26
Q

What are the roles of osteoblasts?

A

Bone forming

Secrete organic bone matrix

Responsible for biomineralisation

Respond to multiple signaling cues and regulate osteoclasts

27
Q

What is another name for bone matrix?

A

Osteoid

28
Q

Why is it important that osteoblasts regulates osteoclasts?

A

To balance bone resorption and formation

29
Q

What is the appearance of osteoblasts?

A

Epithelia-like cell sheet at site of matrix deposition

Basophilic

30
Q

What is the source of osteocytes?

A

Osteoblasts

Terminally differentiated osteoblasts form osteocytes

31
Q

Where are osteocytes found?

A

Reside in lacunae

32
Q

What are characteristics of osteocytes?

A

Long-lived

Non-dividing

Project cytoplasmic processes in canaliculi

These cell-cell contacts allow communication + nutrient and waste exchange through gap junctions

33
Q

What is the role of osteocytes?

A

Resorb, synthesize AND mineralise matrix

At lower rate than osteoblasts and osteoclasts

Contribute to bone turnover

34
Q

The contribution of osteocytes to bone remodelling is at a lower rate than osteoblasts and osteoclasts

TRUE or FALSE

A

TRUE

35
Q

What triggers osteocyte bone turnover?

A

Osteocytes sense mechanical forces

They then respond and transduce signals

Affect bone structure and cellular components

36
Q

What is the source of osteoclasts?

A

Myeloid origin

Fused from precursor cells in bone marrow

37
Q

Why are osteoclasts multi-nucleated cells?

A

Formed by the fusion of precursor cells in the bone marrow

38
Q

Structural features of osteoclasts

A

Large

Motile

Macrophage-like - drive from the same precursors as macrophages

Polar

Eosinophilic

Acid cytoplasm

Highly secretory

39
Q

What are biomarkers for osteoclasts?

A

TRAP-positive

Tartate-resistant alkaline phosphatease

40
Q

What is the role of osteoclasts?

A

As new bone material is added peripherally from the internal surface of the periosteum, there is a hollowing out of the internal region to form the bone marrow cavity

Enter the bone through blood vessels

Dissolve both the inorganic anc protein portions of the bone matrix

41
Q

How do osteoclasts resorb bone?

A

Ruffled border secretes protons and matrix degrading enzymes

42
Q

What is the advantage of the ruffled border?

A

Increases resorptive surface area

43
Q

What is the pH of the resorptive pit?

A

pH≤4.5

44
Q

What do osteoclasts form when they resorb bone?

A

Howship lacunae - pits of eroded bone

45
Q

What triggers resorption of the bone by osteoclasts?

A

Osteoclasts respnond to multiple hormonal, growth factor and cell-cell contact mediated signals

46
Q

Which cell is the associated cellular components of the bone tissue?

A

Mesenchymal stem cells/ bone marrow stromal cells

Haematopoietic stem cells

47
Q

What is the bone marrow?

A

The medullary cavity - stem cell niche for haematopoiesis

48
Q

What is the medullary cavity replaced with as we age?

A

Adipocytes containing yellow marrow for energy storage

Starts in long bones

49
Q

What two lineages arise from the medullar cavity?

A

Myeloid lineage

Lymphoid lineage

50
Q

What are stromal cells of the bone marrow?

A

Additional cells

Support haematopoiesis structurally and physiologically

51
Q

Characteristics of mesenchymal stem cells

A

Sub-population of stroma

Trilineage potential: bone, cartilage, adipose tissue

Highly proliferative and regenerative capacity for musculoskeletal tissue regeneration

52
Q

What is haematopoiesis?

A

Formation of blood cellular components

Bone marrow’s primary function

53
Q

What is the origin of mesenchymal stem cells?

A

No consensus has been reached

Can be found in multiple tissues

54
Q

Ongoing questions about mesenchymal stem cells

A

Do they represent a bone fide stem cell population with discrete properties?

What are the definitive markers of MSCs?

Are they an activated form of pericytes?

Are they transfdifferentitating fibroblasts?

55
Q

What is the condition caused by too many osteoclasts?

A

Osteoporosis

56
Q

What is the condition caused by too many osteoblasts?

A

Osteopetrosis

MSK (22 decks)

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