Embryo Development

Embryo Development

While studying Biology, students would have come across the term embryo development for sure owing to the significance this topic holds in this domain. The term refers to the stages of development an embryo goes through. Such changes would vary from plants to animals viz. from species to species. Here we would be discussing the changes in human embryo in the following paragraphs.

2nd-week development:

During this time period the differentiation process would start for the cells of the embryo.  Different traits would be taken on by these cells of the zygote into nerve, muscle, bone, blood and different sorts of cells. The embryo would be positioned in such a way to take oxygen in along with the nutrients from mother’s blood and eject the waste products into the mother’s bloodstream.

3rd-week development:

Here the embryo would grow to a length of 0.08 inches and would have a shape of a pear with a round shaped head and tail end that is tapered. Also, there would be three types of distinctive cells viz. mesoderm cells for organs, bones, muscles; endoderm cells with the digestive tract; and ectoderm cells with skin formation.

4th-week development:

At this stage, the shape of the embryo would resemble the alphabet C with the forebrain being enlarged and the tail that is visible. The ear pits and eye stalks would be viewable by the time with the buds of limbs both upper and lower could be viewed simultaneously. The emergence of pancreatic, liver, gall bladder, lung and buds would happen mainly at this stage. The initial formation of the face along with the umbilical cord formation also occurs now and eventually, the embryo would resemble the shape of an oval.

5th-week development:

Once the fifth week is completed, the length of the embryo would be around 0.5 inches along with all internal organs being formed. The emergence of external ears would occur along with hands like paddle and buds of upper limbs would form in the same manner. In the meanwhile, the stomach, urinary bladder, and mouth will be present.

6th-week development:

The straightening of the trunks and the development of the upper limb would happen in this phase.  The elbow, the neck, and wrists would form along with the appearance of the buds of pituitary and mammary glands. Also, the buds of teeth would also be formed during this phase.

7th-week development:

At this stage, the hands would be with the yet to be formed thumbs and fingers.  Also, certain changes would happen like the disappearance of the tail, lengthening of the torso and the evolution of the primitive organs.

8th-week development:

The real development occurs in this stage where the nerve cells in the brain forms at the rate of 100,000 per minute with the head top resembling a round shape one and becomes well erected. The genital organs (external) would develop along with the disappearance of the tail and by the 56th day, the length of the embryo would be around 1 to 1.25 inches.

These developments discussed above are the major transformations that an embryo goes through on its way to becoming a human baby.  Being an interesting topic, students and researchers in the field of Biology are carrying out further studies presently and would do so in the years to come.

Stay tuned with BYJU’S to know more about the Embryo Development.


Practise This Question

Acrosomal reaction of the sperm occurs due to___________