Cells That Perform Various Functions

On the eighth day, the cells begin to differentiate and they arrange themselves into two distinct groupings, an inner and an outer one. The inner cell mass (embryoblast), forms the cells that the embryo will possess throughout its whole life. The outer group of cells (trophoblast), is composed of the cells that assist the human being in its life in the mother's womb, that is, for nine months until its birth.

The Attachment of the Embryo to the Uterus is a Miracle of the Qur'an When we examine the verses in the Qur'an that deal with the attachment of the embryo to the uterus, we see one of the greatest wonders of the Qur'an. In the Qur'an, while referring to the embryo's attachment to the uterus and the beginning of its development, God uses the word "alaq": Recite in the Name of your Lord Who created man from alaq. Recite: And your Lord is the Most Generous. (Qur'an, 96: 1-3) The word "alaq" in Arabic means "something that clings, a leech-like substance". The Qur'an came down to us 1400 years ago and the fact that God uses this word to describe the development of the embryo in the mother's womb is one if its wonders. The fact that this knowledge, which could not have been discovered by the science of that period, was revealed centuries ago in the Qur'an confirms once again that it is a revelation from God, the Lord of all the worlds. In the first picture, we see a one-week-old cell cluster looking for a place in the uterus. After finding a suitable place, the cell cluster dissolves the tissue of the uterine wall and embeds itself in it. (2-3) The embryo securely attaches itself to the uterine wall and begins to take from it the oxygen and other nutrients that it needs. (4)

The inner cell mass separates itself from the outer group of cells that will serve it throughout the nine months. The remaining region will become the umbilical cord providing the connection between the embryo and the placenta that will develop later.

At about the same time that the placenta begins to form, the inner cell mass flattens and develops into three layers of cells in what is called the "embryonic disc". The three types of cell layers are the ectoderm, the mesoderm, and the endoderm. In a process called differentiation, cells from each layer move to certain areas of the embryonic disc and then fold over to form tubes or clusters. These tubes and clusters develop into various tissues and organs of the body.23

Cells from the outermost layer, the ectoderm, form the brain, spinal cord, the sense organs and the lens of the eye. Moreover, this layer will form the epidermis, the sweat glands, tooth enamel, hair and nails. The innermost layer of the embryo (the endoderm) will cause the development of the organs that compose the digestive and respiratory systems (liver, lungs, pancreas, etc.) and the related glands (thyroid, thymus, etc.). The third layer (the mesoderm) is formed between these two layers. From this layer are formed the heart, muscles, bones, tendons, kidneys, glands, blood vessels, and reproductive organs. The lymphatic vessels and the epithelia (surface, or lining, tissues) which cover the most internal and external surfaces of the body and its organs also develop from this layer. The cells which compose all the tissues of the body are formed from these stem cells which develop from one of these layers.

From stem cells come all the approximately 200 kinds of cells in the human body. (1) Identical stem cells suddenly begin to differentiate from other cells. With this differentiation, the tissues of the body are formed from stem cells. Fat cells which provide energy (2), cells which heal wounds (3) and blood vessel cells (4) are a few of these tissues.

It is very important to think about the meaning of the last sentence of the above paragraph, and to consider well the significance of what it says, because only in this way can we begin to conceive of the extraordinary development of a human being. The fact that all the elements that constitute the human body (organs, tissues, systems, blood vessels, blood, etc.) develop from the three kinds of layers that make up the embryo will lead a thinking person to find the answer to the question: Where does this supreme intelligence that the cells possess come from?

In the meantime, there are some details that we must not lose sight of and that make these changes even more extraordinary. For example, in the course of the development of a human being, there is a perfect harmony among these three layers of cells. In order for the approximately 200 kinds of cells in the body to be produced from three kinds of cells, a definite sequence and timing is required. For example, the sequence of events in the differentiation of the blood cells and the skin cells is very different in each case. This is a remarkable phenomenon which raises a number of questions.

23. Gerard J. Tortora, Introduction to the Human Body: Essentials of Anatomy & Physiology, p. 556