Cytology Week 11 Flashcards
Describe compact(cortical bones) and its location
-Dense and located near the surface of the bones
Explain where cancelous(trabecular ) bones are located
- Deeper within interconnecting cavities
What is the bulbous end of Long bones called
Epiphyses
What is the cylindrical part of Long bones called
Diaphysis
Explain what Epipyses are composed of
— Cancellous bone covered by a thin layer of compact bone
Explain the structure of Diaphysis
- Compact bone with thin layer of cancerous bone around the marrow cavity
Name examples of were short bones are located
In the wrists and ankles
Explain the structure of Short bones
- Contains a core of cancellous bone surrounded by compact bone
Explain the structure of flat bones
Two layers of compact bones separated by a thicker layer of cancellous bone around
At microscopic level: compact and cancellous bone show two what 2 types of Organization :
- Mature lamellar bone
-Woven bone
What is lamellar bone characterized by
- ## multiple layers of calcified matrix
What type of collagen fibers does lamellar bone contain
- Type 1 collagen fibers
What are Osteons
-What do central canals contain
-They are Cylindrical units with lamella surrounding a central canal
- Blood vessels,nerves
What is the outer boundary of the osteon and what does it contain
- Cement line
-Non collagen proteins, minerals and collagen
Name the 2 bone regions
- Interstitial lamellae
-Circumferential lamellae
-What is Woven bone -What does it contain
What are the characteristics/propeties of Woven bone
- Lower mineral content
- higher porportion of osteocytes than LAMELLAR bone
What is the first bone to appear during embryonic development and fracture repair
-Woven bone
Where are the areas thst Woven bone is retained
- Near the sutures of the calvaria
-Insertions of some tendons
Name the 2 main stages that occur in the bone development process
-Intramembranous Ossification
-Endochondral Ossification
Explain bone formation process very breifly
- It initally produces woven bone but this is then later replaced by stronger lamellar bone.
Explain briefly want happens in intramembranous ossification
Osteoblasts differentiate directly from mesenchyme and secrete osteoid.
Explain briefly what happens in Endochondral Ossification
A hyaline cartilage matrix is eroded and invaded by osteoblasts, which begin producing osteoid.
What type of bones does intramembraneous ossification form
+examples
- Flat bones such as :
-Skull
-Scapula
-Clavicle
Explain the key features in intramembranous ossification:include
-Osteprogenitor cells
-
- Osteoprogenitor cells proliferate(increase in number) and form osteoblasts
-Osteoblasts secrete osteoid which calcifies into woven bone. - woven bone is later replaced by compact and cancellous bone.
In intramembranous ossification what does Non-ossified mesenchymal regions become
-Periosteum and endosteum
What bones does Endochondral Ossification produce
-Most bones icluding long bones
Name the 4 main stages in Endochondral Ossification
- Bone collar formation
-Cartilage Calcification
-Primary Ossification center
-Secondary Ossification center
Explain the first and second step of enchondral ossification(Bone collar formation + Cartilage calcification)
- Osteoblasts form perichondrium and create the collar
-Chondrocytes hypertrophy, secrete matrix proteins and initiate calcification
Name the 2 cartilage regions that continue to remain in Endochondral Ossification
-Articular Cartilage
-Epiphyseal Growth plate
What happens in the 2nd+3rd step of Endochondral ossification(primary and secondary ossification)
- Osteoblasts invade the calcified cartilage, forming woven bone.
- Develop later at epiphyses, creating cancellous bone.
What does bone remodelling involve and function
-continuous bone resorption by osteoclasts and formation by osteoblasts.
-Maintains bone shape
Why does bone have an excellent repair capacity
-Due to osteoprogenitor cells
Name the 3 phase bone repair
Phases of repair:
-Formation of fibrocartilage.
-Replacement of fibrocartilage with a temporary woven bone callus.
-Remodeling into mature bone.
Where does the skeleton sotre 99% of the bodys calcium
- In the hydroxyapatite crystals
What is the function of the Parathyroid hormome in hormonal regulation of calcium
- Raises blood calcim levels
-Stimulates osteoclasts activity by acting on osteoblast
What is the funtion of the hormone Calcitonin in the regulation of calcium
- Lowers blood calcium levels
-Inhibits osteoclasts activity
Name the 2 hormones resposnible for the regulation of calcium
-Parathyroid hormone
-Calcitonin
What do joint types determine
The degree of movement between bones
Name the 4 different types of joints
-Synarthroses
-Synostoses
-Syndesmoses
-Symphyses
What are intervetberal disc composed of
- Fibrocartilage
What is the function of intevertebral discs
- Provide support and cushioning
What are joints connected and stabilized by
Connective tisues
What type of movement does synarthroses have
-Little or no movement
What are the synarthroses joints subdivided into
-Synostoses
-Syndesmoses
-Symphyses
Explain the strutcure and movement of synostoses joints
- Bones are fused allowing no movement
What are syndesmoses joints joined by
Dense connective tissue
What are symphyses joints joined by
- Fibrocartilage pad and thin articular cartilage
