Development of Three Types of Synovial Joints
During vertebrate evolution, the head underwent changes related to the development of the special senses. The anterior end of the nerve cord became a brain, and the nerves passing to…
Remodeling: Maintenance of Basic Form and Proportions of Bone During Growth
The cells of the myotome, the mononucleated myoblasts, elongate in a direction parallel to the long axis of the embryo (see Plate 1-17) and undergo repeated mitotic divisions, subsequently fusing…
Growth in Width of a Bone and Osteon Remodeling
The dense concentration in cardiac muscle of orderly arrangements of interdigitating actin and myosin molecules, which could synchronously slide across each other throughout the atrial or ventricular muscle, resulted in…
Progressive Stages in Formation of Vertebral Column, Dermatomes, and Myotomes; Mesenchymal Precartilage Primordia of Axial and Appendicular Skeletons at 5 Weeks
The branchial arch skeleton is derived from the embryonic counterparts of the gill arches that support the mouth and pharynx of present-day adult fish and tailed amphibians. The most primitive…
Changes in Ventral Dermatome Pattern During Limb Development
The myeloid, or bone marrow, period of hematopoiesis begins during the fourth month. The bone marrow is the principal site of all blood cell formation during the last 3 months…
Fate of Body, Costal Process, and Neural Arch Components of Vertebral Column, With Sites and Time of Appearance of Ossification Centers
Once the appendicular skeleton starts to develop, the progress is rapid. Early in the sixth week, only vague concentrations of mesenchyme represent the primordia of future bones. By the end…
Skeleton of Full-Term Newborn
Although bone remodeling begins during the fetal period, it is not very active before birth but accelerates during the first year after birth. The annual rate of bone renewal during…
Early Development of Skull
BONE GROWTH Cartilage grows continually on the side of the epiphyseal plate facing the epiphysis of a long bone, while on the opposite side of the plate facing the diaphysis,…
Secondary Osteon (Haversian System)
Restriction of joint motion by permanent paralysis early in development can result in the loss of the joint cavity by having a permanent fusion occur between the apposed surfaces of…
Differentiation of Somites into Myotomes, Sclerotomes, and Dermatomes
The clustering of sclerotomal cells to form the bodies of the vertebrae establishes intervertebral fissures that fill with mesenchymal cells to become the intervertebral discs (see Plate 1-3). The notochord…
