Embryologi In The Qur'an: Description Of Izam

Human development from the gamete stage (nutfah) throughout pregnancy has been mentioned in the Holy Qur'an with elegant simplicity and clarity:

وَلَقَدْ خَلَقْنَا الْإِنْسَانَ مِنْ سُلَالَةٍ مِنْ طِينٍ - ثُمَّ جَعَلْنَاهُ نُطْفَةً فِي قَرَارٍ مَكِينٍ - ثُمَّ خَلَقْنَا النُّطْفَةَ عَلَقَةً فَخَلَقْنَا الْعَلَقَةَ مُضْغَةً فَخَلَقْنَا الْمُضْغَةَ عِظَامًا فَكَسَوْنَا الْعِظَامَ لَحْمًا ثُمَّ أَنْشَأْنَاهُ خَلْقًا آَخَرَ فَتَبَارَكَ اللَّهُ أَحْسَنُ الْخَالِقِينَ - ثُمَّ إِنَّكُمْ بَعْدَ ذَلِكَ لَمَيِّتُونَ - ثُمَّ إِنَّكُمْ يَوْمَ الْقِيَامَةِ تُبْعَثُونَ

And We (God) created man4 from a quintessence (gentle extraction) of clay.
We then placed him as a nuṭfah (drop) in a place of settlement, firmly fixed (i.e. the womb). alaqah (clinging form), and then We changed the clinging form into a mudghah (chewed-like form), then We made out of that chewed-like form, ‘iẓām (skeleton, bones), then We clothed the bones with laḥm (muscles, flesh); then We (ansha’ nahu), caused him to grow and come into being and attain the definitive (human) form. Blessed be God, the Perfect creator. Then you will surely die .and then, on the Day of Resurrection, you will be raised up again. Surah Al-Mu’minoon (The Believers) 23: 12-16

In this paper, the processes of embryonic osteogenesis and myogenesis are described in current biological terminology; then the From: Zindani, A. A., Ahmed, M. A., Tobin, M. B., & Persaud, T. V. N. (1994). Human Development as Described in the Qur'an and Sunnah: Islamic Academy for Scientific Research. First presented at an international conference in Riyadh, Saudi Arabia (September 1983).


Osteogenesis.
Development of both human bone and muscle has been well described and reported in contemporary scientific literature. Bone, of course, does not develop simultaneously throughout the body. Rather, there is a program or timetable of osteogenesis. For example, the ossicles of the inner ear are the first bones to fully ossify (during fetal life) whereas the growth centers in long bones of the leg do not close until 20 or more years after birth.

Note: The hands are rapidly changing after just seven weeks of pregnancy. And in three or four more days, free fingers!
Label Key:   1. digital rays    2. notching    3. liver    4. index digital ray    5. heart    6. facial profile    7. thumb digital ray    8. left hand

However, a distinct stage for bone formation is discernible in which cartilaginous skeleton begins to form with the spread of the cartilage in the 7th week. Bone develops in one of two ways (depending upon its locale), viz., as endochondral bone or as intramembranous bone. Both types of bone formation involve a precursor population of mesenchyme (embryonic connective tissue) cells.

Where intramembranous bone forms (e.g., mandible and maxilla), mesenchyme cells condense (form dense cell aggregates) and differentiate into osteoblasts. The osteoblasts secrete the collagenrich organic matrix of bone about themselves. Once surrounded by matrix, the cells are referred to as osteocytes. The organic matrix mineralizes as the bone ossifies.

Endochondral bone forms in a similar fashion except that the condensed mesenchymal cells first differentiate into chondroblasts that lay down the organic matrix of cartilage (Figure 5-1). So, a
cartilage model of the bone forms initially. Secondarily, the cartilage is replaced by bone. A layer of connective tissue called perichondrium surrounds the cartilage model (or periosteum around bone) and serves as a reservoir of progenitor cells (chondroblasts or osteoblasts) as these tissues grow.

Although precursor cells to muscle and bone may reside quite near one another (in the somites, for example), their histories begin to diverge as cells begin to migrate to various sites in the embryo (Figure
5-2). The long bones of the body are derived from embryonic mesenchyme. Mesenchymal cells in the limbs condense, i.e., aggregate in

Figure 5•1. In the histogenesis of cartilage, mesenchymal cells (A)withdraw their processes and become crowded together to form an area of precartilage (B). In newly formed embryonic cartilage (C) in the 'izam stage, the densely aggregated cells of the precartilaginous stage have been moved apart by deposition of clear hyaline matrix between them. The cells then become angular (D) and isolated in clearly demarcated lacunae. (Reprinted with permission from Fawcett, 1986)

Figure 5•2. Section through 2.9 mm human embryo (in early mudghah stage) showing somite cells prior to migration. (Reprinted with permission from Blechschimdt, 1961)

the region where osteogenesis is going to occur later. From this densely packed mass of cells begins the histogenetic process by which mesenchyme cells differentiate into chondroblasts. The chondroblasts, in turn, secrete around themselves the organic matrix of cartilage. The chondrification process results in the appearance of a cartilage model of the bone that is to form, resulting in a skeleton and human shape for the embryo. From the connective tissue of the perichondrium, cells differentiate and form a bony collar around the shaft of the cartilage model. As a consequence of this, the avascular cartilage is cut off from diffusing nutrients, becomes necrotic, and the chondrocytes die. This is followed by an invasion of connective tissue cells and vascular elements from the adjacent connective tissue.

Certain of these invading cells differentiate into osteoblasts, surround themselves with newly secreted bony organic matrix and thereby the osteocytes of newly developing bone (where previously there was a cartilage model). Formation of bone does not begin uniformly throughout the body. Rather, there is a sequential appearance of bony tissue. However, in the 7th week the spreading development of the skeleton occurs. Bone development in the limbs commences in the limb buds from mesochymal cells. Primary ossification centers appear in the femur during week 7 (Figure 5-3) and in the sternum and the maxilla in weeks 8-9 (Figures 5-4, 5-5).

Figure 5•3. Primary ossification centers in the human embryo during the seventh week. (Reprinted with permission from Patten, 1968)

In recent decades, the process of osteogenesis in the human embryo has been reasonably well documented. At the histological level, the role of the mesenchyme, osteoblasts, osteoclasts, and osteocytes has been studied. Staging of cartilage deposition and mineralization in the embryo has been facilitated by the application of staining procedures specific for cartilage and bone. Although precursor cells (myoblasts) are present adjacent to developing bone, differentiation into skeletal muscle attachments occur after the ossification process in the shaft and ends of the bones has begun (Figure 5-6).

Figure 5•4. Primary ossification centers in the sternum during weeks eight through nine. (Reprinted with permission from Patten, 1968)

Figure 5•5. Primary ossification centers in the maxilla during weeks eight through nine. (Reprinted with permission from Patten, 1968)

Figure 5•6. Section through 11 mm human embryo. Note precursor musculature forming adjacent to developing bone. (Reprinted with permission from Blechschmidt, 1961)

Izam stage.
"Then (fa) We made out of that mudghah, 'izam (skeleton, bones) ... "

This Qur'anic statement indicates that the bone stage is subsequent to the mudghah stage and that the mudghah has developed skeletal elements. Specific terms are used in the Qur'an to describe different stages. The shape of the embryo determines the selection of the term used for each stage, e.g. the nutfah changes to alaqah when it loses its drop-like appearance. Similarly, the alaqah changes to mudghah according to a change in its shape. Therefore, the stage which follows the mudghah is called the 'izam (bone) stage for the development of the skeleton spreads during this stage. The conjunction fa (then) of the Qur' anic ayah indicates that the 'izam stage develops after the mudghah stage without a long delay.

The mudghah stage lasts approximately until the 6th week, and the bones make their appearance by the beginning of the 7th week with the development of the cartilaginous skeleton in accordance with the hadith:

"when 42 nights have passed from the time of the nuifah (time of conception), Allah sends an angel to it, who shapes it and makes its hearing, sight, skin, muscles and bones .... " (Sahih Muslim, Kitab Al-
Qadar).

In the early part of the "izam stage, the embryo takes on a human appearance (taswir iidaml), and the hadith describes this with the word of "shapes." Before the 42nd day, it is difficult to distinguish the human embryo from the embryos of many animals, but at this time it becomes clearly distinguishable in its appearance (Figure 5-7).

Figure 5-7. A, Photograph of an embryo during the 'izam stage (44 to 46 days in age) in its amniotic sac, exposed by opening the chorionic sac (x 2.7). B, Higher magnification of the 14 mm (crown-rump length) embryo (x 4.8). Note the human appearance taswir adamij at this age. (Reproduced with permission from Moore, K.L., The Developing Human, Clinically Oriented Embryology, 4th ed., Philadelphia, Saunders, 1988)

Also, some of the generalized cells of the embryo begin to differentiate into various lines and modify into different functional moieties. This process results in straightening and the formation of organs necessary for viability. The body surface is becoming more even and attaining a straighter configuration at this stage, as described in the Qur'an:

"Who (God) created you, then (fa) made you even and straight (sawwak) and then (fa) modified you ('addalak)" (Surah Al-Infitar, 82: Ayah 7).1