Bone Growth & Development

Bone Growth & Development Charles A Simanjuntak, dr, SpOT(K), FICS, MPd FKIK Universitas Jambi

Development of bone(1) • Lateral & paraxial plate (somatic layer) mesodermal from neural crest • Paraxial mesoderm tissue block lateral tu neural tube a k a somitomere • Somites caudally of occipital region • Somites  scleretome & dermomyotome • 4th week, sclerotome  mesenchyme (embronic connective tissue) • 6th week the limb buds becomes flattened  handplatesand footplates CharlesASjuntak, FKIK-Unja

CharlesASjuntak, FKIK-Unja

Development of bone(2) • Flattened limb buds becomes circular constriction • Later a second & third constriction divides the proximal portion into 2 or 3 segments, and the main parts of the extremities can be recognized • Fingers and toes are formed when cell death in the AER separates this ridge into five parts CharlesASjuntak, FKIK-Unja

Development of bone(3) • Development of the upper and lower limbs is similar but morphogenesis of the lower limb is 1 to 2 days behind that of the upper limb CharlesASjuntak, FKIK-Unja

Development of bone(4) • 7thweek of gestation the limbs rotate in opposite directions • Upper limb rotates 90◦ laterally so that the extensor muscles lie on the lateral and posterior surface and the thumbs lie laterally, • lower limb rotates approximately 90◦ medially, placing the extensor muscles on the anterior surface and the big toe medially. CharlesASjuntak, FKIK-Unja

Development of bone(5) • By the 6th week of development the first hyaline cartilage models, foreshadowingthe bones of the extremities, are formed by these chondrocytes • Joints are formed in the cartilaginous condensations when chondrogenesisis arrested and a joint interzone is induced. CharlesASjuntak, FKIK-Unja

Development of bone(6) • Embryoic connective tissue  fibroblast, chondroblast, osteoblast (bone-forming cells) • Formation of shoulder & pelvic girdles & long bones of the limbs • all long bones of the limbs differentiated by the 12th week. • Differentiated by • Intramembranous ossification • Endochondral ossification CharlesASjuntak, FKIK-Unja

Development of bone(7) • Primary center in the shaft or diaphysis of the bone, endochondralossification gradually progresses toward the ends of the cartilaginous model • At birth the diaphysis of the bone is usually completely ossified, but the two ends, the epiphyses, are still cartilaginous • Epiphyseal plate, plays an important role in growth in the length of the bones. CharlesASjuntak, FKIK-Unja

Development of bone(8) • Endochondral ossification proceeds on both sides of the plate • When the bone has acquired its full length, the epiphyseal plates disappear and the epiphyses unite with the shaft of the bone. • In long bones an epiphyseal plate is found on each extremity • In smaller bones, such as the phalanges, it is found only at one extremity • In irregular bones, such as the vertebrae, one or more primary centers of ossification and usually several secondary centers are present. CharlesASjuntak, FKIK-Unja

Growth of the Skeleton(1) • Development of the skeleton, especially the part played by bone growth, is closely related to the total development of the organism • Estimation, radiological examination plays a major diagnostic roleegestimating eventual body height • Skeletal age evaluated by fusion of the epiphyseal and apophyseal disks (growth disks) CharlesASjuntak, FKIK-Unja

Growth of the Skeleton(2) • Growth and developmentdepend on many factors • Body weight and especially growth in height depend on genetic influences, but external influences, such as the quality and quantity of the nutrients ingested with food, can also be demonstrated CharlesASjuntak, FKIK-Unja

Development of Bone Tissue • Reticular bone (woven bone) is formed in the embryonic period & during healing of a fracture • Reticular bone corresponds to a hardened connective tissue rich in fibers and can originate in two different ways: • membrane bone develops directly from the mesenchyme. This type of ossification is called membranous or desmalossification • cartilaginous bone precursor first forms in the mesenchyme is then rebuilt into bone (endochondral bone). This process is called endochondral or indirect ossification CharlesASjuntak, FKIK-Unja

Development of a Long Bone(1) • Most bones develop indirectly of a cartilaginous precursor. Only a few bones (some bones in the skull, theclavicle) develop directly by membranous ossification • Parts of a long bone can develop directly by membranous ossification even where it has been laid down in cartilage, e. g., the perichondral bone cuff that originates in the diaphysis and that provides the base from which the bone grows in thickness (perichondral ossification) CharlesASjuntak, FKIK-Unja

Development of a Long Bone(2) • Bony tissue is laid down indirectly, in that the cartilage is first removed by cartilage-absorbing cells (chondroclasts) and then replaced by chondral ossification. • Where the diaphysis meets the epiphysis, an epiphyseal plate develops, where growth in length takes place and in which the cartilage cells divide until growth stops CharlesASjuntak, FKIK-Unja

Development of a Long Bone(3) • The epiphyseal plate is visible in the radiograph by its lack of calcification. • Bone formation within the epiphyses (ossific centers) begins only at the time of birth. Many ossific centers develop only in the first years of life. • Special ossific centers that develop on bone for the attachment of muscles are called apophyses. CharlesASjuntak, FKIK-Unja

Vertebra • 4th week, sclerotome migrate medially  spinal cord & notochord  vertebral body & nucleus pulposus • Nucleus pulposus surrounded by circular fibers of anulus fibrosis  intervertebral disc CharlesASjuntak, FKIK-Unja

Question ? CharlesASjuntak, FKIK-Unja

Bone Growth & Development