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…
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…
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…
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…
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…
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,…
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…
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…
Articular cartilage, especially that found in weightbearing joints, is uniquely structured to withstand tremendous abuse. It can resist crushing by static loads considerably greater than those required to break a…
MUSCLES Characteristically, all living cells, including protozoa and slime molds, contain the contractile proteins actin and myosin. Thus, actin and myosin are present in all the cells of the human…
