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Finally, in adults, the head represents approximately 12% of the body length. The cephalocaudal trend is also the trend of infants learning to use their upper limbs before their lower limbs. The proximodistal trend, on the other hand, is the prenatal growth from 5 months to birth when the fetus grows from the inside of the body outwards.
The proximodistal trend is the tendency for more general functions of limbs to develop before more specific or fine motor skills. It comes from the Latin words proxim- which means "close" [ 1 ] and "-dis-" meaning "away from", [ 2 ] because the trend essentially describes a path from the center outward.
Like physical growth, motor development shows predictable patterns of cephalocaudal (head to foot) and proximodistal (torso to extremities) development, with movements at the head and in the more central areas coming under control before those of the lower part of the body or the hands and feet. [90]
Arm and hands are more developed than feet and legs (cephalocaudal development); hands appear large in proportion to other body parts. Legs may continue to appear bowed. "Baby fat" continues to appear on thighs, upper arms and neck. Feet appear flat as arch has not yet fully developed. Both eyes work in unison (true binocular coordination).
This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and anatomical axes. The meaning of terms that are used can change depending on whether an organism is bipedal or quadrupedal.
Biological rules and laws are often developed as succinct, broadly applicable ways to explain complex phenomena or salient observations about the ecology and biogeographical distributions of plant and animal species around the world, though they have been proposed for or extended to all types of organisms. Many of these regularities of ecology ...
As a result of the cephalocaudal and lateral folding of the embryo, a portion of the endoderm-lined yolk sac cavity is incorporated into the embryo to form the primitive gut. In the cephalic and caudal parts of the embryo, the primitive gut forms a tube, the foregut and hindgut, respectively.
The face and neck development of the human embryo refers to the development of the structures from the third to eighth week that give rise to the future head and neck.They consist of three layers, the ectoderm, mesoderm and endoderm, which form the mesenchyme (derived form the lateral plate mesoderm and paraxial mesoderm), neural crest and neural placodes (from the ectoderm). [1]