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BONE AND CARTILAGE-2

Explore the microscopic formation of bone in the developing skull of a 20-day rabbit foetus, identifying key cell types and processes. Understand the stages of intramembranous ossification and bone strengthening.

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BONE AND CARTILAGE-2

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  1. BONE AND CARTILAGE-2 This resource is licensed under the Creative Commons Attribution Non-Commercial & No Derivative Works License

  2. Objectives For both Bone & Cartilagesessions Describe the microscopic appearance of the different histological types of cartilage. Identify the cell types found in bone and describe the microscopic organisation of cortical and trabecular bone. Consolidate the information on bone development gained in lectures by observing the microscopic appearance of developing bones.

  3. INTRAMEMBRANOUS OSSIFICATION

  4. SLIDE 129 Developing skull (20 day rabbit foetus) View of whole slide. Identify the region of the skull in which bone development is taking place; outside the meninges covering the brain. 1.0 cm

  5. SLIDE 129 Developing skull (20 day rabbit foetus) View of whole slide. Identify the region of the skull in which bone development is taking place; outside the meninges covering the brain. 1.0 cm

  6. SLIDE 129 Developing skull (20 day rabbit foetus) Examine the site at one end of the forming bone where committed osteogenic and fibrogenic cells are closely associated : this is a region undergoing intramembranous bone formation. 250 µm

  7. SLIDE 129 Developing skull (20 day rabbit foetus) Examine the site at one end of the forming bone where committed osteogenic and fibrogenic cells are closely associated : this is a region undergoing intramembranous bone formation. developing bone 250 µm skin surface

  8. SLIDE 129 Developing skull (20 day rabbit foetus) Examine the site at one end of the forming bone where committed osteogenic and fibrogenic cells are closely associated : this is a region undergoing intramembranous bone formation. 250 µm

  9. SLIDE 129 Developing skull (20 day rabbit foetus) Identify : bone matrix, active osteoblasts, preosteoblasts, undifferentiated fibroblasts and blood vessels. 100 µm

  10. SLIDE 129 Developing skull (20 day rabbit foetus) M : bone matrix O : osteoblasts P : preosteoblasts Identify : bone matrix, active osteoblasts, preosteoblasts, undifferentiated fibroblasts and blood vessels. O F M F : fibroblasts BV BV : blood vessel O P F 100 µm

  11. SLIDE 129 Developing skull (20 day rabbit foetus) Consider why this region would be devoid of both lining cells and osteoclasts. 100 µm

  12. SLIDE 129 Developing skull (20 day rabbit foetus) Consider why this region would be devoid of both lining cells and osteoclasts. Because in this area there is active bone formation. Lining cells are only found on quiescent bone surfaces (few here). Osteoclasts only found in areas of bone remodelling. 100 µm

  13. SLIDE 129 Developing skull (20 day rabbit foetus) Identify in an adjacent region of this skull bone, areas where bony trabeculae are taking shape. 100 µm

  14. SLIDE 129 Developing skull (20 day rabbit foetus) trabeculae Identify in an adjacent region of this skull bone, areas where bony trabeculae are taking shape. matrix blood vessel 100 µm

  15. SLIDE 129 Developing skull (20 day rabbit foetus) Identify : all stages of the intramembranous ossification process. fibroblasts, preosteoblasts, osteoblasts, osteocytes, matrix and blood vessels. 50 µm

  16. SLIDE 129 Developing skull (20 day rabbit foetus) BV : blood vessel F : fibroblasts M : matrix osteoblasts Identify : all stages of the intramembranous ossification process. fibroblasts, preosteoblasts, osteoblasts, osteocytes, matrix and blood vessels. osteocytes M M BV osteoblasts preosteoblasts F 50 µm

  17. SLIDE 129 Developing skull (20 day rabbit foetus) How is this bone subsequently strengthened? 50 µm

  18. SLIDE 129 Developing skull (20 day rabbit foetus) How is this bone subsequently strengthened? By consolidation of the trabecular structure. 50 µm

  19. SLIDE 10 Developing mandible (17 day rat foetus) This is a transverse section through a developing head. At this low magnification identify the developing oral cavity (which will have the forming tongue on its ventral floor). 1.0 mm

  20. SLIDE 10 Developing mandible (17 day rat foetus) This is a transverse section through a developing head. At this low magnification identify the developing oral cavity (which will have the forming tongue on its ventral floor). oral cavity developing tongue 1.0 mm

  21. SLIDE 10 Developing mandible (17 day rat foetus) Scan the area ventral to the oral cavity and identify the developing mandible. 250 µm 1.0 mm

  22. SLIDE 10 Developing mandible (17 day rat foetus) oral cavity developing tooth Scan the area ventral to the oral cavity and identify the developing mandible. M mandible 250 µm M : Meckel’s cartilage (do not confuse with mandible) 1.0 mm

  23. SLIDE 10 Developing mandible (17 day rat foetus) Osteogenesis is more advanced than in the skull bone. Identify bone adjacent to the position of tooth primordium. 100 µm

  24. SLIDE 10 Developing mandible (17 day rat foetus) tooth primordia Osteogenesis is more advanced than in the skull bone. Identify bone adjacent to the position of tooth primordium. bone 100 µm

  25. SLIDE 10 Developing mandible (17 day rat foetus) Examination of this area will disclose the presence of osteoclasts. 50 µm

  26. SLIDE 10 Developing mandible (17 day rat foetus) M : bone matrix O : osteoblasts Bv : blood vessel Os : osteoclast M Bv Examination of this area will disclose the presence of osteoclasts. Os M O O Bv 50 µm

  27. SLIDE 10 Developing mandible (17 day rat foetus) What is the function of these cells? 25 µm

  28. SLIDE 10 Developing mandible (17 day rat foetus) What is the function of these cells? The osteoclasts are remodelling the mandible in the area of tooth development. Note these cells are large and multinuclear. Os : osteoclasts Os 25 µm

  29. ENDOCHONDRAL OSSIFICATION

  30. SLIDE 127 Early changes in the limb’s cartilage model, longitudinal section. Inspect this slide at low magnification and establish the position of individual developing cartilage models (elements or bones) of the limb. In addition confirm your view by successfully recognising the developing articular surfaces and joint spaces. These individual bones develop in a proximal-distal sequence (most mature is proximal). 1.0 mm

  31. SLIDE 127 Early changes in the limb’s cartilage model, longitudinal section. B Inspect this slide at low magnification and establish the position of individual developing cartilage models (elements or bones) of the limb. In addition confirm your view by successfully recognising the developing articular surfaces and joint spaces. These individual bones develop in a proximal-distal sequence (most mature is proximal). A C D bones A-D articular surfaces arrowed 1.0 mm

  32. SLIDE 127 Early changes in the limb’s cartilage model, longitudinal section. Selected from previous image is a more mature example to examine in greater detail. 250 µm

  33. SLIDE 127 Early changes in the limb’s cartilage model, longitudinal section. A A : articular surface R R : resting cartilage cells Selected from previous image is a more mature example to examine in greater detail. R 250 µm

  34. SLIDE 127 Early changes in the limb’s cartilage model, longitudinal section. Examine the various stages of chondrocyte maturation. Resting - see previous picture P : Proliferating M : Maturing H : Hypertrophic C : Calcifying D : Dying 100 µm

  35. SLIDE 127 Early changes in the limb’s cartilage model, longitudinal section. P M Examine the various stages of chondrocyte maturation. Resting - see previous picture P : Proliferating M : Maturing H : Hypertrophic C : Calcifying D : Dying H C D 100 µm

  36. SLIDE 127 Early changes in the limb’s cartilage model, longitudinal section. View of selected area showing the transition of cells from the maturing to the hypertophic stage. 50 µm

  37. SLIDE 127 Early changes in the limb’s cartilage model, longitudinal section. mature View of selected area showing the transition of cells from the maturing to the hypertophic stage. hypertrophic 50 µm

  38. SLIDE 127 Early changes in the limb’s cartilage model, longitudinal section. collar of bone View of mid-diaphyseal region showing hypertrophic, calcifying and dying cartilage cells and the collar of bone formation surrounding the cartilage. 50 µm

  39. SLIDE 136 Growing femur (rat)Ossification of the epiphysis, longitudinal section. View of whole slide. Identify the region of the epiphyseal growth plate. 1.0 mm

  40. SLIDE 136 Growing femur (rat)Ossification of the epiphysis, longitudinal section. Epiphyseal growth plate View of whole slide. Identify the region of the epiphyseal growth plate. 1.0 mm

  41. SLIDE 136 Growing femur (rat)Ossification of the epiphysis, longitudinal section. Low magnification view of area. 1.0 mm

  42. SLIDE 136 Growing femur (rat)Ossification of the epiphysis, longitudinal section. D : diaphysis M : metaphysis E : epiphysis Low magnification view of area. GP D M GP : epiphyseal growth plate E 1.0 mm

  43. SLIDE 136 Growing femur (rat)Ossification of the epiphysis, longitudinal section. Identify the following sequence of events. 1. Proliferation of cartilage cells. 2. Hypertophy of chondrocytes. 3. Calcification of cartilage matrix (purple). Deposition of bone (pink) on cartilage ‘template’ (blood vessels, osteoblasts and osteocytes). Organisation of bony trabeculae and their osteoclastic resorption. 250 µm

  44. SLIDE 136 Growing femur (rat)Ossification of the epiphysis, longitudinal section. Identify the following sequence of events. 1. Proliferation of cartilage cells. 2. Hypertophy of chondrocytes. 3. Calcification of cartilage matrix (purple). Deposition of bone (pink) on cartilage ‘template’ (blood vessels, osteoblasts and osteocytes). Organisation of bony trabeculae and their osteoclastic resorption. 5 2 4 1 3 250 µm

  45. SLIDE 136 Growing femur (rat)Ossification of the epiphysis, longitudinal section. Proliferation of cartilage cells. Hypertrophy of chondroctes. Calcified cartilage (purple). Deposition of bone (pink) on cartilage ‘template. 100 µm

  46. SLIDE 136 Growing femur (rat)Ossification of the epiphysis, longitudinal section. Proliferation of cartilage cells. Hypertrophy of chondroctes. Calcified cartilage (purple). Deposition of bone (pink) on cartilage ‘template. 100 µm 3 2 1 4

  47. SLIDE 136 Growing femur (rat)Ossification longitudinal section. diaphyseal region It may be valuable to consider how much of the bone derived from the epiphyseal growth plate is incorporated into the bone’s cortex. 50 µm

  48. SLIDE 136 Growing femur (rat)Ossification longitudinal section. diaphyseal region bone marrow It may be valuable to consider how much of the bone derived from the epiphyseal growth plate is incorporated into the bone’s cortex. osteocytes bone matrix osteoblasts calcified cartilage (remnants) 50 µm

  49. SLIDE 135 Growing femur (rat) Growth in length. This section is similar to slide 136. 1.0 mm

  50. SLIDE 135 Growing femur (rat) M : metaphysis A : articular surface E : epiphysis D : diaphysis Growth in length. This section is similar to slide 136. A A E M M D E 1.0 mm

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