Up to 10 weeks
This is a time of very rapid and crucial development-your baby quadruples in size. The embryo is lying in the center of a large placental cocoon, and is still very tiny. As it develops, its cells are constantly changing to make new structures.
Your Baby’s Progress
Inside the tube that will eventually become your baby’s brain and spinal cord, the cells multiply at an amazing rate, then move away to the areas where they will become active. Nerve cells that will form the brain travel along pathways that are being laid down glial (glue) cells. These cells allow the nerve cells to move toward each other, connect, and become active.
Your baby’s head is growing rapidly in order to make room for the enlarging brain, and the body is becoming less curved. A neck begins to develop and the primitive tail disappears.
The skin now starts to develop into its two layers, and the sweat glands and sebaceous (oil-producing) glands begin to form. Hair then starts to grow from the hair follicles so that the skin becomes downy. All the major organs develop. The heart achieves its final form and beats strongly. The stomach, liver, spleen, appendix, and intestine develop. The intestine becomes so long it forms a loop the circulatory system is established, and most muscles begin take on their final form.
Facial features Under the skin on the baby’s face, a primitive bone structure has developed, and these bones are now fusing together. One of these goes down between the eyes and ends on either side of the nostrils, thus forming the nose and the middle of the upper lip. Two others appear under the eyes, forming the cheeks and sides of the upper lip. Two more grow under the mouth, fusing to form the lower lip and chin. All this provides the framework to which the facial muscles become attached, which then allows the face to move.
There’s already some pigment in the eyes, which are covered and very far apart. The inside and outside parts of the ears begin to form and the taste buds start developing. The tooth buds of all nonpermanent teeth are now in place.
Arms and legs Embryonic limbs continue to develop. Wrists and fingers appear on the arm buds, which become longer and project forward. The arms become bent at the elbow. Touch-pads form on the fingertips. Leg buds sprout, then develop three distinct sections-thigh, calf, and foot. Toes start to appear. At this stage, your baby’s arms and hands grow faster than her legs and feet.
This trend will continue after your baby’s been born-she’ll be able to grasp objects long before she’s starts walking.
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