Lesson 10 Flashcards
What is the process of bone formation called?
Osteogenesis
Which cells are responsible for bone formation?
Osteoblasts
What is the process of mineralization in bone formation called?
Ossification
What type of ossification occurs in a membranous environment with fibroblasts, mesenchymal cells, and collagen fibers?
Intramembranous ossification
Which bones develop through intramembranous ossification?
Bones of the skull
What type of ossification occurs in an environment previously occupied by cartilage?
Endochondral ossification
Does cartilage transform into bone during endochondral ossification?
No, it is destroyed and replaced by bone.
Which bones develop through endochondral ossification?
Long bones like the femur and radius
What is the formation of bone in areas not normally occupied by bone tissue called?
Pathologic (metaplastic) ossification
Give an example of pathologic ossification.
Ossification of the tracheal and laryngeal cartilages
What is the accumulation of calcium salts in tissues due to persistent hypercalcemia called?
Metastatic calcification
What is the calcification of degenerative or dead tissues called?
Dystrophic calcification
Which type of ossification is responsible for the final shape of bones that are not preformed in cartilage?
Intramembranous ossification
Which type of ossification is responsible for the longitudinal growth of the body?
Endochondral ossification
How does bone growth occur after the initial deposition of bone?
By appositional growth
Which cells differentiate into osteoblasts in intramembranous ossification?
Mesenchymal cells
What do osteoblasts synthesize and secrete in early bone formation?
Organic matrix containing collagen
What is the incompletely mineralized matrix where collagen fibers are visible called?
Osteoid
Which mineral is deposited in the fibrous matrix during intramembranous ossification?
Calcium
What happens to osteoblasts that become surrounded by their secretory products?
They turn into osteocytes
What is the function of osteocytes?
Providing nourishment to the formed bone
What type of bone is formed during intramembranous ossification due to large spaces between bone spicules?
Cancellous or woven bone
What is the function of woven bone during development?
It serves as a temporary structure.
What are trabeculae made up of in woven bone?
Spider-like processes (spicules) radiating from the first bone formed.
What characterizes cancellous bone?
Large spaces between trabeculae.
What happens to cancellous bone as lamellae continue to be deposited?
It gradually converts into compact bone.
Which two processes are important in bone formation?
Bone growth and bone resorption.
Why must bone growth and resorption remain balanced?
To ensure that no cell in the newly formed bone is too far from a blood capillary.
How does the bone shaft grow wider while maintaining a marrow cavity?
New bone is added outside while bone is resorbed from the inside.
Which cells are responsible for bone resorption?
Osteoclasts
What are the little pits eroded by osteoclasts called?
Howship’s lacunae.
What is the first step in endochondral ossification?
Condensation of mesenchymal cells in areas where bone will develop.
What do mesenchymal cells differentiate into during endochondral ossification?
Chondroblasts.
What do chondroblasts form?
A cartilaginous model of the developing bone.
What structure forms around the cartilage model?
Perichondrium
What two types of growth contribute to the lengthening and thickening of the cartilage model?
Appositional and interstitial growth.
What happens to the perichondrium at the proximal and distal ends of the model?
It is lost and these sites become the articular surfaces.
What do chondroblasts become when they stop secreting matrix?
Chondrocytes
Which cells invade the middle of the cartilage model to form osteoblasts and osteoclasts?
Mesenchymal cells and blood vessels.
What does the perichondrium in the diaphysis transform into?
Periosteum
What is the woven bone that forms around the diaphysis called?
Collar or sleeve bone
What is the diaphysis now called after it begins ossification?
Diaphyseal ossification center.
This artery is responsible for bringing blood vessels, hemopoietic cells, and osteoprogenitor cells into the midsection of the cartilage model.
nutrient artery
How does bone formation proceed from the diaphysis?
It extends toward both ends of the cartilage model.
What process allows the bone to continue increasing in length?
Chondrocytes continue dividing at the proximal and distal ends.
What structure ensures that bone and cartilage grow proportionally in length?
The periosteum adds new bone to the diaphysis.
What is the name of the secondary ossification centers?
Epiphyseal ossification centers.
Which two areas of the bone do not ossify during development?
The articular surfaces and the epiphyseal plate.
What happens to the epiphyseal plate after postnatal bone growth is complete?
It is replaced by bone.
How many zones of cartilage cells are in the epiphyseal plate?
Five zones
Which zone is adjacent to the epiphyseal endplate and contains non-dividing cells?
Zone of resting chondrocytes
Which zone is responsible for bone elongation?
Zone of proliferative chondrocytes.
What is the key characteristic of the zone of proliferative chondrocytes?
Stacks of thin, wedge-shaped cells that are actively mitotic.
What do the stacks of proliferative chondrocytes represent?
Isogenous groups or cell nests.
What are the characteristics of the zone of maturing chondrocytes?
- Larger cells and lacunae
- more rounded lacunae
- obvious columnation of cells
Which zone contains larger cells and thin transverse septa?
Zone of hypertrophic chondrocytes.
Which zone consists of cells whose matrix undergoes calcification?
Zone of calcified cartilage.
What is found in the zone of calcified cartilage?
Blood capillaries.
A loss of continuity or structural integrity in bones?
Fracture
What are the two types of fracture healing?
Primary intention and secondary intention.
How does primary intention healing occur?
Direct bone formation without a cartilaginous support structure.
How does secondary intention healing occur?
Formation of a cartilaginous support structure (callus) during repair.
What is the first stage of fracture repair?
Impact stage
What occurs during the impact stage?
The manifestation of damage or trauma on the bone.
What happens in the induction stage?
Proliferation, differentiation, and modulation of new bone cells to replace damaged ones.
Which stage is characterized by redness, pain, swelling, and heat?
Inflammatory stage
What is removed during the inflammatory stage?
Devitalized tissue and hematoma.
What occurs during the reparative stage?
New cells and blood vessels migrate to the fracture site, forming fibrocellular tissue that later becomes bone.
What is the new osseous tissue derived from the endosteum called?
Internal callus
What is the external callus derived from?
Periosteum
Which stage involves bonding of the new bone to dead and live bone?
Remodeling stage
What is the final outcome of the remodeling stage?
The fractured portion of the bone returns to normal
What are the factors that influence the course and outcome of bone repair?
- Diet
- Age of the animal
- Presence of intercurrent disease
- Stability and immobilization of the fracture site
- Good vascular integrity
- Ability to return fragments to their original position (reduction)
Why is good vascular integrity important in bone healing?
It ensures sufficient blood supply for cell migration, nutrient delivery, and waste removal, promoting effective repair.
Which hormone is released when blood calcium levels fall below normal?
Parathormone (PTH)
Where is parathormone (PTH) secreted from?
Parenchymal cells of the parathyroid gland.
What effect does parathormone have on bone?
- Activates osteoblast receptors
- suppresses matrix formation
- stimulates osteoclast activity
- promotes bone resorption to release calcium ions
Which hormone is released when calcium levels are too high?
Calcitonin
Where is calcitonin secreted from?
Parafollicular cells of the thyroid gland
It inhibits osteoclast activity, preventing bone resorption and lowering blood calcium levels.
calcitonin
Which hormone influences bone development and epiphyseal plate growth?
Somatotropin (growth hormone)
Where is somatotropin secreted from?
Anterior lobe of the pituitary gland
Which factor is secreted by osteoblasts and activates osteoclast precursors?
Interleukin-1
Which factors function similarly to interleukin-1?
Tumor necrosis factor and colony-stimulating factor-1.
Which cells secrete colony-stimulating factor-1?
Bone marrow stromal cells.
What is the function of osteoprotegerin?
Inhibits osteoclast differentiation.
Which factor stimulates osteoclast formation?
Interleukin-6
Which immune cell secretes interferon-γ, and what is its effect on bone?
T-lymphocytes; it inhibits differentiation of osteoclast precursors.
Which factor is released from bone matrix during osteoclasia and promotes bone formation?
Transforming growth factor-β (TGF-β)
What are the effects of TGF-β on bone cells?
It induces osteoblasts to manufacture bone matrix, enhances matrix mineralization, and inhibits osteoclast differentiation.
