1. The right answer is bone deposition.
During the formation of osteon, osteoblasts, embryonic bone cells, deposit around them ossein which is progressively mineralized. Thus become osteocytes, these immured cells nevertheless still receive nutrients and oxygen through the fine canalicles which connect them and which also serve for the elimination of waste.
2. The right answer is bone resorption.
Osteoclasts are the cells responsible for bone resorption by attaching to the bone matrix via the development of junctions: the podosomes consist of integrins, adhesion proteins, creating a tight zone where the action of proton pump decreases the pH , and the secretion of proteolytic enzymes, which leads to the degradation of the bone matrix, and the reabsorption of its components. The gaps left after the action of osteoclasts are called "Howship Gaps". They serve in particular to detect cases of hyper-resorption when they are too numerous.
This osteoclastic activity is permanent and necessary to maintain bone strength, in synergy with the activity of osteoblasts.
Osteoclasts are present in bone tissue being resorbed.
3. The right answer is bone remodeling.
Bone remodeling is the result of precise cooperation between osteoclasts and osteoblasts. Whether in the compact or trabecular bone, the bone tissue is constantly renewed. This permanent remodeling, in which the resorption and the formation of bone tissue take place, is carried out thanks to functional units of remodeling where the osteoclasts and osteoblasts are closely associated. The bone is thus formed of millions of functional units of remodeling, mobile and progressing in the bone tissue (the osteoclasts being at the front and the osteoblasts at the back). The metabolic activities of these 2 cell populations are coupled in space and time. A remodeling cycle lasts approximately 4 months in adults, the training phase being longer than that of resorption.
4. The right answer is periosteal.
The periosteum is a set of layers of the periphery of the long bones and flat bones outside the articular surfaces and which ensure the growth in thickness. We speak of "periosteal growth in width".
Composed of a fibrous outer layer, a fibroelastic intermediate layer and an osteoblastic (non-fibrous) inner layer, this connective tissue is able to ensure the insertion of tendons and ligaments on the bone. It is a predominantly fibrous, non-oriented connective tissue.
5. The right answer is endosteal.
The endosteum is a thin layer of connective tissue lining the surface of the medullary cavity of long bones1. This layer is resorbed during long periods of malnutrition, resulting in a decrease in cortical thickness. The outer surface of a bone is also bordered by a thin layer of connective tissue very similar in morphology and function to that of the endosteum, (called periosteum).
6. The right answer is 20%.
Living structure, our skeleton is renewed each year by 20%. This "bone remodeling" is essential to maintain the mechanical and metabolic functions of our framework.
At the heart of this process are two types of cells:
* Osteoclasts responsible for destroying old bone by digging holes (resorption);
* Osteoblasts responsible for making new bone partly thanks to calcium by filling the holes (formation) "dug" by osteoclasts.
Osteoblasts and osteoclasts work together to replace calcified cartilage with true bone tissue.
The bone undergoes a constant rearrangement (the bone is continuously resorbed and rebuilt).
7. The right answer is compact bone.
The compact bone constitutes the diaphysis of the long bones and the envelope of the flat and short bones.
The compact bone or cortical bone (80-85% bone) constitutes a resistant envelope composed by the juxtaposition of cylindrical osteons of 200 to 300 μm in diameter aligned parallel to the diaphysis, each osteon is composed of concentric lamellae. The collagen fibers are oriented to impart optimal mechanical strength to the cortical tissue. Each osteon is centered by a channel called "de Havers" of 50 microns in diameter. The Havers canals are interconnected by transverse channels called "Volkmann". Each channel is centered by an innervated vessel that communicates with both the periosteal vasculature and the vessels of the marrow.
8. The right answer is spongy bone.
Spongy bone or trabecular bone constitutes the epiphyses and metaphyses of long bones and the interior of flat bones and short bones. It consists of a network of plates and anastomosed cylinders. With age, the spans are rather cylinders. Each plate has the overall shape of a parallelepiped. The three-dimensional organization of these bone plates together is the trabecular architecture which has an important role in the mechanical strength of the bone. The orientation of the spans depends on the lines of mechanical forces to which the bone is subjected because the cells that manufacture them (the osteoblasts) have the capacity to perceive these mechanical forces.
