Phase 1a revision - Bone Anatomy & Phsyiology Flashcards

1
Q

What are osteogenic stem cells?

A
  • Cells derived from mesenchymal stem cells and have the capacity to differentiate into osteoblasts and chondroblasts
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2
Q

What are the 5 types of bone?

A
  • Flat bones
  • Long bones
  • Irregular bones
  • Short bones
  • Sesamoid bones
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3
Q

Where does red marrow reside in?

A
  • Cancellous bone
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4
Q

What are osteocytes?

A
  • Osteocytes are mature osteoblasts that have been enveloped within the bone matrix
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5
Q

Where do osteocytes reside?

A
  • Osteocytes reside within the lacuna and communicates with surroundings by canaliculi
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6
Q

What are the main functions of osteocytes (3)?

A
  • Capable of bone deposition and resorption involved in bone deformation caused by muscular activity
  • Strengthens bone in response to additional stresses
  • Continue to form bone to an extent (maintain strength of the bone matrix)
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7
Q

What is the function of the osteoblasts?

A
  • Responsible for the catalysing and synthesising the mineralisation of osteoid during bone formation and remodelling
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8
Q

Which cells do osteoblasts arise from?

A
  • Arise from the differentiation of osteogenic cells in the periosteum – the tissue that covers the superficial surface of bone and in the endosteum (marrow cavity)
    • Differentiation requires constant supply of blood
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9
Q

What is the periosteum?

A
  • The tissue that covers the superficial surface of bone
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10
Q

What do osteoblasts secrete (5)?

A
  • Alkaline phosphatase
  • Colleganase
  • Growth factors
  • Collagen
  • Osteocalcin
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11
Q

What are osteoclasts?

A
  • Osteoclasts are large multinucleated cells responsible for the dissolution and absorption of bone – mediators of bone destruction by phagocytosis
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12
Q

Where do osteoclasts reside?

A
  • Within Howship Lacunae - caused by their erosion of bone by osteoclast derived enzymes
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13
Q

What are the 2 main types of bone?

A
  • Immature woven (primary) bone
  • Mature lamellar (secondary) bone
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14
Q

How are the collagen fibres organised within woven bone?

A
  • In a haphazard organisation
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15
Q

What is the first type of bone formed in embryonic development and fracture healing?

A
  • Primary bone - immature woven bone
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16
Q

What are the two forms of mature bone?

A
  • Cortical (compact) bone
  • Cancellous (cancellous) bone
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17
Q

Which type of bone ensheathes the bony medulla?

A
  • Cortical bone
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18
Q

How is cortical bone organised?

A
  • Lamellar configuration
    • Densely arranged osteons (Haversian systems)
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19
Q

What is an osteon?

A
  • The chief structural unit of compact (cortical) bone consisting of:
    • Contain a central canal that is surrounded by concentric rings (lamella) of the matrix
    • Osteocytes located between lamellae within the small cavities - lacunae
    • Canaliculi radiate from the launcae to the Haversian canal to provide passageways through the hard matrix
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20
Q

How do the blood vessels interconnect within bone?

A
  • By Volkmann’s canal
21
Q

Which cells mediate bone resorption through phagocytosis?

A
  • Osteoclasts
22
Q

How do osteoclasts mediate bone resorption (3 steps)?

A
  1. Ruffled border (invaginations of the plasma membrane) is formed by osteoclasts, which define the active region where acid phosphatase enzymes are secreted to dissolve the organic collagen and inorganic calcium & phosphate of the bone
  2. Attach to the bone by osteopontin and sialoprotein forming a sealing zone between the osteoclast and bone
  3. Calcium hydroxyapatite crystals are removed from the bone by acidification – the osteoid is protected against osteoclastic resorption
23
Q

How is calcium stored within bone?

A
  • Calcium hydroxyapetite crystals
24
Q

Which cells are predominantly found within immature woven bone?

A
  • Osteocytes
25
Q

What type of bone is the humerus?

A
  • Long bone
26
Q

What type of bone is patella?

A
  • Sesamoid bone
27
Q

Which type of collagen forms the bone?

A
  • Type I bone (90%) + Type V bone
28
Q

How is cancellous bone organised?

A
  • Cancellous bone is characterised by a trabecular structure that is comparatively less dense, softer, weaker and less stiff than cortical bone
29
Q

Where does cancellous bone reside?

A
  • Within the epiphysis of the bone and within the medullary canal
30
Q

What is the function of cancellous bone (2)?

A
  • Greater surface area is ideal for metabolic activity - exchange of calcium ions
  • High vascular and red bone marrow support haemopoiesis
31
Q

What is the function of flat bones?

A
  • Protects internal organs
32
Q

What type of bone is the cranial cavity?

A
  • Flat bone
33
Q

What is the function of long bones?

A
  • Support & facilitate movement
34
Q

What is the function of irregular bones?

A
  • Vary in shape and structure
35
Q

What is the function of short bones?

A
  • No diaphysis, as wide as they are long, provide stability and some movement
36
Q

What is the function of sesamoid bones?

A
  • Embedded within the tendons potentially protects tendons from stress or wear
37
Q

What is the diaphysis?

A
  • A tubular shaft that traverses between the proximal and distal ends of the bone
    • The hollow region within the diaphysis is considered to be the medullary cavity
38
Q

What does the medullary cavity encapsulate?

A
  • Yellow marrow
39
Q

What are the walls of the diaphysis composed of?

A
  • Dense and hard compact bone
40
Q

What is the membranous lining of the medullary cavity?

A
  • Endosteum
41
Q

What is the outer surface of the medullary cavity?

A
  • Periosteum
42
Q

Where does the red marrow occupy?

A
  • The cavities of the trabeculae within the epiphysis
43
Q

What is the epiphysis?

A
  • Wider terminal ends of bone that are filled with cancellous bone
44
Q

What is the point at which the epiphysis meets the diaphysis?

A
  • Metaphysis
45
Q

What is the metaphysis?

A
  • Narrow segments that contain the epiphyseal growth plates - a layer of hyaline in a growing bone
46
Q

What is intramembranous ossification (8 steps)?

A
  1. Mesenchymal cells undergo differentiation and specialises into osteogenic cells and ultimately osteoblasts
    • Clusters of osteoblasts form an ossification centre
  2. Osteoblasts secrete osteoid, uncalcified matrix consists of collagen precursors and organic proteins which calcifies due to mineralisation - therefore entrapping osteoblasts
  3. Osteoblasts that are entrapped within the matrix become osteocytes
  4. As osteoblasts transform into osteocytes, osteogenic cells in the surrounding connective tissue differentiate into osteoblasts at the edges of growing bone
  5. Clusters of osteoid unite around capillaries → Forms a trabecular matrix
  6. Osteoblasts on the surface of newly formed spongy bone become the cellular layer of the periosteum
  7. The periosteum secretes compact bone superficial to the cancellous bone
  8. Cancellous bone aggregates near blood vessels condensing into red bone marrow
47
Q

What is endochondral ossification?

A
  • The bone develops through hyaline cartilage replacement - Behaving as a template to be completely replaced by new bone
48
Q

Compare the rate at which intramembranous and endochondral ossification occur.

A
  • Endochondral ossification is longer than intramembranous ossification
49
Q

What is the process of endochondral ossification (7 steps)?

A
  1. Formation of matrix increases cartilaginous model size - blood vessels in the perichondrium brings osteoblasts to the edges of the structure
  2. Arriving osteoblasts deposit osteoid in concentric formation around the diaphysis
    • Bony edges of the developing structure prevent nutrients from diffusing into the centre of the hyaline cartilage → Chondrocyte death
  3. Periosteal bud invasion: Without cartilage inhibiting blood vessel invasion, blood vessels penetrate the resulting space - enlarging the cavities and transferring osteogenic cells with them - forming osteoblasts
    • The enlarged spaces become the medullary cavity
  4. Chondrocytes and cartilage continue to grow at the epiphyses, increasing length
  5. Continued growth is accompanied by remodelling inside the medullary cavity, and overall lengthening of the diaphysis
  6. Cartilage remains at the epiphyses and at joint surfaces as articulate cartilage
  7. Secondary ossification centre forms