Musculoskeletal System Developments | Lecture Note

University:
The University Of Western Ontario
Course:
Biology 2290F | Scientific Method in Biology
Academic year:

2022
Views:

294

Pages:

2
Author:

Kyuwon J.

Musculoskeletal system ● Embryologic basis ○ Intramembranous ■ direct formation on messenchym ■ does not need cartilage model ■ ex) flat bones, skulls, clavicles ○ Endochondral ■ bone formation on replacing hyaline cartilage templates ■ Long bones are formed in this methods ■ ex) femur, humerus ● limb buds forms on week 5 during the developments ● Chondrification => vascular invasions => primary ossification center (diaphysis) => Secondary center (epiphyses) ● growth plate is between diaphysis and epiphysis and will remain there ○ epiphysis for longitudinal growth Growth plate (physis) 1. Reserve (resting) a. quiescent of cartilage cells 2. Proliferative a. rapid cell division b. longitudinal stacking 3. Hypertrophic a. enlarging cells b. mineralization in prepared in this stage 4. Calcifications a. Calcification of matrix b. Chondrocytes will die at this point 5. Ossifications a. Osteoblasts deposit bone on calcified cartilage Site of pediatric fractures ● Salter-Harris classifications ● Growth arrest => limb lengths discrepancy + deformity Genetic molecular regulations ● Signaling molecules ○ Sonic Hedgehog (Shh) ○ BMPs ○ Wnt ○ FGFs ● Transcription factors ○ SOX9 ■ chondrocyte differentiations ○ RUNX2 ■ Osteoblast formations ● Hormonal control ○ Growth hormone IGF-1 => cartilage proliferation ○ Thyroxine => early bone maturations ○ Sex steroids => epiphyseal closures Postnatal Bone Growth ● Longitudinal growth => epiphyseal plate ● Appositional growth => periosteal bone depositions Imaging and Evaluations ● Radiographs ○ assessment on ossification centers and growth plate integrity ● Bone age ○ comparing hand-wrist radiographs ● MRI ○ showing early cartilage abnormalities upon mineralizations Integrations on Hematopoiesis ● Bone marrow cavities on developing bones ○ become primary site of blood formations (hematopoiesis) ● Red marrow predomination in childhood ○ replaces yellow marrow with age Critical Disorders ● Achondroplasia ○ FGFR3 mutations ■ inhibition chondrocyte proliferations ○ Short limbs, normal trunks ● Osteogenesis imperfecta ○ Collagen type 1 defects ○ Fragile bones ○ Blue sclerae ● Rickets/ Osteomalacia ○ Vitamin D deficiency ○ poor mineralizations ○ deformities ● Physeal injury ○ trauma to growth plates ○ growth arrest on angular deformity Embryologic patterning genetic control forms foundation on orthopedic pediatric practices