Bone and Muscle Systems

Get to know how the bone and muscle systems develop week by week, when to wait for teeth appearance.
Bone and Muscle Systems

Bone System
The newborn baby’s bone system contains relatively few saults; this is the reason why his bones are soft and elastic. They get broken more rarely, but if it happened, they get knitted more quickly and easier.

Baby’s skull consists of frontal bones, two parietal bones, two temporal bones, one occipital bone, one sphenoidal bone and one ethmoid bone. Facial bones are united firmly, but there are lamboid and coronal sutures between other skull bones. There is an anterior fontanelle of a size of about 1,5 x 1,5 inches on a baby’s skull between his  forehead and vertex. This fontanelle gets healed by the age of 14 months as a rule, but if a baby suffers from rachitis or other diseases, it happens later. Newborn babies have the mastoid fontanelle, which is situated on the level of parietal bones’ ocipital edges. About 25 % of newborns have it healed no later than by the 8th week after their arrival. Thanks to these fontanelles skull bones can get shifted during the baby’s arrival to make his head come out easier.

Newborn’s head occupies about 1/4 of his body length (the head of an adult person takes no more than 1/8 of his body length). The volume of a baby’s head is 13,4 inches and by the end of the first year of his life, it is 18,1 inches.

The spinal column of a newborn baby consists purely of a cartilage and it has no curves at all. Neck curve appears right after a baby learns to hold his head. Pectoral curve begins to form after the age of 6-7 months when a baby sits without any assistance and it gets completely formed by the 6-7 years of child’s life. Lumbar curve gets noticeable after 9-12 months and it develops completely during the child’s school age.
Baby’s thorax is wide and short. His ribs lie horizontally, and spaces between them are narrow.

Pelvis bones of newborn babies and of children during first several years of their life are relatively little. The pelvis is of a form of a funnel.

Teeth. Babies usually arrive without teeth. First teeth appear by the 6th – 8th month of a baby’s life-these are central teeth in mandible. By the 9th month central teeth in maxilla appear as a rule. By the age of 10 months a baby usually has 6-4 teeth on his upper jaw and 2 teeth on his lower one. When a baby is 12 months old, there are 8-4 teeth on the upper jam and 4 on the lower jam. By 15 months a baby has 12 teeth already; by 18-20 months- 16 months, and by the age of 20-30 months a healthy baby has 20 teeth.
 Teeth appearance is the physiological phenomenon. Baby’s condition should not change a lot, but there are kids, who may get nervous, their temperature may rise, and they may even have some digestion problems. But there is no need to give your baby any medicine, as all the above mentioned symptoms will disappear themselves.

Muscle System
The newborn babies’ muscle system condition and its further development are in tight dependence of the central nervous system functions. The movements’ perfection becomes able thanks to the movement reflexes under the regulating influence of the cortex formation. Newborn babies’ cortex is immature yet, that is why their movements are much different from the elder children’s’ movements. The extremities of a newborn baby are lightly bended and pressed to their body. During first weeks of his life a newborn baby moves his arms and legs quite slowly. It depends on the cortex’s immaturity.
Beginning from the age of 4th - 6th months, when the cortex begins its functioning, all baby’s movements become quick and energetic.
Baby’s deliberate movements are symmetrical as a rule, he takes everything with both his hands, and it is only later, when the habit to take something with his one hand gets acquired.