| Define ossification | ossification is another word for osteogenesis and is bone tissue formation |
| What forms membrane bones? | Membrane bones are formed directly from mesenchyme
- they undergo intramembranous ossification |
| What forms other bones (not membranous bones)? | Other bones are developed initially from hyaline cartilage
- undergo endochondral ossification |
| Describe what is occuring in this photo, why is it important. | This photo shows the very beginning of bone formation, the mesenchymal cells differentiate into osteoblasts and create an ossification center. We also see the formation of collagen fibers |
| Desribe what is occuring in this photo, why is it important? | This photo shows the 2nd step in the bone formation process. The ossification center allows for the osteoblast to start secreting bone; new bone matrix. Some osteoblast become trapped inside the new bone and thus become osteoclasts. |
| Describe what is occuring in this photo, why is it important? | This photo shows the third step of bone formation, the bone has been secreted but blood vessels begin to weave in and out + osteoids are laid in a random manner and this combination creates the trabeculae. Also the remaining mesenchyme cells condense and form the periosteum. |
| Describe what is occuring here, why is it important? | some of the trabeculae hardens forming compact bone, however, some trabecula remains and the vascular tissue becomes red bone marrow
- also in this particular picture |
| What bones go through Endochondral Ossification? | All bones except some bones of the skill and clavicles go through endochondral ossification |
| Desribe Endochondral ossification? | In endochondral ossification
- the bones are modeled in hyaline cartilage
- the bone begins to form late in the 2nd month of embryonic development
- continues forming until early adulthood |
| What is occuring in this phase of Endochondral ossification? | Because Endochondral ossification is where bones are modeled from hyaline cartilage, we see a bone collar form around the cartilage and an ossification center is created. |
| What is occuring in this phase of Endochondral ossification? | The ossification center begins to form bone in the diaphysis region, cavities are developed |
| What is occuring in this phase of Endochondral ossification? | Blood vessels begin to grow into the cavities and spongy bone begins to form |
| What is occuring in this phase of Endochondral ossification? | Ossification continues and the diaphysis begins to elongate and the medullary cavity forms. |
| What do the epiphyseal plates allow? | The epiphyseal plates allows for osteoblasts to continue producing bone, thus it is a growth plate.
- pushes the epiphysis away from the diaphysis |
| What allows the epiphyseal plates to grow | cartilage cells form tall stacks (chondroblasts are located at the top of these stacks and divide quickly), the cartilage is organized for quick efficient growth |
| What signals the growth plate to produce more bone? | Older chondrocytes send signals surrounding the matrix to calcify
- they then die and disintegrate |
| What area is shown here | Resting zone of bone |
| What area is shown here? What occurs here? | Proliferation zone
- cartilage cells are undergoing mitosis |
| What area is shown here? What occurs here? | The Hypertrophic zone
- older cartilage cells enlarge |
| What area is shown here? What occurs here? | Calcification zone
- matrix becomes calcified
- older cartilage cells die
- matrix begins deuterating |
| What area is shown here? What occurs here? | Ossification zone
- new bone is forming |
| During childhood and adolesence, what occurs to the new cartilage cells that were produced by the epiphyseal plate? | The cartilage is replaced with bone connective tissue as quickly as it grows |
| What occurs to the epiphyseal plates as adolecence comes to an end? | the epiphyseal plates become thinner
- chondroblasts divide less often
- cartilage stops growing, is replaced by bone tissue |
| When do long bones stop lengthening? | Long bones stop lengthening when diaphysis and epiphysis fuse |
| How do bones widen (growing bones widen as they lenghten) ? | Osteoblasts add bone tissue to the external surface of the diaphysis
Osteoclasts remove bone from the internal surface of the diaphysis |
| Define appositonal growth | appositional growth is the growth of a bone by addition of bone tissue to its surface. |
| What stimulates the growth at the epiphyseal plates? | a growth hormone produced by the pituitary gland |
| What ensures that the skeleton retains its proper proportions? | Thyroid hormone |
| What are the different types of fractures? | Simple and compound fractures |
| How can one treat a fracture | through reductions
- either through closed reductions or open reductions |
| What first begins the healing process of a fracture? | A fracture also causes not only the bone to break but the vessels thus the vessels bleed into the area and create a hematoma. |
| What occurs after a hematoma is created in the fractured area? | Fibrous tissue and cartilage grows into the area (a internal and external callus is formed)
New blood vessels are formed |
| What occurs to the fibrocartilageinous callus? | the callus hardens... becomes a bony callus due to the osteoblasts |
| What occurs after the bony callus forms? | Bone remodeling..... fracture is healed |
| What is a comminuted fracture? | The fracture results in 3+ bone fragments
-is common in elderly |
| What is a compression fracture? | The fracture results in the bone being crushed
- common in porous bones subjected to extreme trauma |
| What are the 2 fractures shown here? | left picture: comminuted fracture (multiple pieces)
right picture: compressed fracture (spine is tilting) |
| What is a spiral fracture? | A spiral fracture is a ragged break that occurs when excessive twisting forces are applied to a bone
- a common sports fracture |
| What is a epiphyseal fracture? | an epiphyseal fracture is when the epiphyses separates from the diaphysis along the epiphyseal plate
- tends to occur where cartilage cells are dying and calcification of the matrix is occurring |
| What 2 fractures are shown here? | left picture: spiral fracture (caused by twisting)
right picture: epiphyseal fracture (epiphyses seperates) |
| What is a depressed fracture? | a depressed fracture typically occurs in the skull and is when the broken bone is pressed inward |
| What is a greenstick fracture? | A greenstick fracture is when the bone breaks incompletely, one side of the shaft breaks and the other side is bended
- common in children whose bones are more flexible |
| What are the 2 fractures shown here? | left picture: depressed fracture (pressed inward)
right picture: Greenstick fracture (not completely broken) |
| What is osteoporosis? Who does it affect the most? Where does it most often occur? | A disease of aging
- the weakening of the bone by the bone having a long bow mass
- bone reabsorption is greater than bone deposition
- occurs most often in women after mesopause
- affects the trabecular bone the most |
| What occured to the bone on the bottom? | the normal bone was affected by osteoporosis |
| When is the peak of bone mineral density? | 30 |
| What occured to this person? Why did they become shorter? | Osteoporosis caused compressing of the spine thus the spine bends |
| Define Osteomalacia | osteomalacia occurs in adults and is caused by bones being inadequately mineralized |
| Define Rickets | Rickets occurs in children, caused by a vitamin D deficiency |
| What is this child suffering from? | Vitamin D defiency so Ricketts |
| What does mesenchyme produce? | mesenchyme produces membranes and cartilage which then ossifies |
| Explain the ration of bone formation and bone reabsoprtion in different age groups | Children and adolescents: Bone formation > bone reabsorption
Young adults: bone formation = bone reabsorption
Old age: bone reabsorption > bone formation |
