University:
MacEwan University
Course:
HLSC 120 | Human Anatomy
Academic year:

2023
Views:

149

Pages:

3
Author:

Arthur M.

II. Bone Development tymai Ustodies Outboid Ostsoryte •Osteogenisis & Ossification refer to the process of bone tissue formation, which leads to! - The formation of bony skeletons in embryos - Bone growth until early adulthood *Bone remodeling è Repair Formation of Bony Skeleton in Embr40s ) Intramembranous Ossification: bone develops from a fibrous membrane formed by mesenchymal cells - Begins at week 8 of embryo dev. - Forms the cranial bones of the skull & clavicles Stages 1) Ossification center appears in fibrous connective tissue membrane (mesenchymal cells cluster form. osteoblasts) 2) Bone matrix (osteoid) secreted in fibrous membrane - Osteoblasts secrete osteoid • Trapped osteoblasts become osteocytes 3) Woven (spongy) bone & periosteum form • Osteoid laid down between blood vessels forming random network of trabeculae - Mesenchyme on external surface forms periosteum 4) Bone collar of compact bone forms, red marrow appears - Trabeculae deep in periosteum thicken l replaced w/ compact bone - Spongy b. remains in center l vesseis become red marrow hylaine 2) Endochondral Ossification: replacing cartilage w/ bone - Starts in second month of dev. - Forms long bones & other skeletal bones Steps: 1) Formation of bone collar around prim. ossification center in the diaphysis 2) Cavitation of hyaline cartilage 3) Invasion by periosteal bud (surface tissue), spongy bone forms 4) Form, of medullary cavity; appearance of secondary. ossification centers in the epiphyses 5) Ossification of epiphyses, w/ hyaline cartilage remain. in epiphyseal plates and articular cartilage