Internal structure of a leech
If we examine the anatomy of the leech we find that the appearance of its internal structures is also similar to that of the human embryo.
Prevention of blood-clotting
A striking similarity between the leech and the embryo is the way in which enzymes are released to facilitate easy blood-flow and the prevention of the clotting of blood. As the embryo draws nourishment [leech-like] from the mother’s blood, the anticoagulant enzyme, Thrombomodulin, [TM] prevents the blood clotting. In the leech, the protein that serves the same function is called Hirudin.
Summary of ‘Alaqah stage
The Qur’anic term ‘alaqah is a comprehensive expression for the second stage of embryonic development that descriptively encompasses the primary external and internal features. In this one word, the general shape of the embryo as a leech is described, the internal events such as the formation of blood and closed vessels are described, and the attachment of the embryo to the placenta is also brought to mind.
The similarity between the embryo and leech is remarkable:
• the external shape of the leech resembles an embryo at 22-25 days,
• the internal structure of the leech resembles an embryo of 22-26 days,
• the embryo clings to the lining of the uterus in a similar way to a leech that clings to the skin,
• the embryo obtains nourishment from the blood of the mother, like the leech which feeds on the blood of others,
• the embryo has a segmented body like a worm or leech,
• the early embryo further resembles a leech in that it has a tube-like gut running from one end to the other.
The Qur’anic term ‘alaqah refers to the embryo when it is extremely small. The ‘alaqah is just 0.7-3.0mm in length. Due to the small sizes involved, scientists could not have recognised the detailed features of the ’alaqah stage until the second half of the 19th century and the beginning of the 20th.
Prof. Keith L. Moore concludes that it is, “remarkable how much the embryo of 23-24 days resembles a leech. As there were no microscopes or lenses available in the 7th century, doctors would not have known that the human embryo had this leech-like appearance. In the early part of the fourth week, the embryo is just visible to the unaided eye because it is smaller than a kernel of wheat.” 
The embryo at 24-25 days is finishing the ‘alaqah stage. It changes into the mudghah stage at 26-27 days. The transformation from ‘alaqah to mudghah is in fact very rapid, and during the last day or two of the ‘alaqah stage, the embryo is beginning to develop some of the characteristics of the mudghah, e.g. the somites begin to appear and become a distinct feature of this stage.
One of the meanings of the word mudghah is “something that is chewed by teeth.” If one were to take a piece of gum and chew it in his or her mouth and then compare it with an embryo at the mudghah stage, we would conclude that the embryo at the mudghah stage acquires the appearance of a chewed substance. This is because of the somites at the back of the embryo that “somewhat resemble teeth-marks in a chewed substance.”
The embryo at mudghah stage acquires the appearance of a chewed substance, because the somites at the back of the embryo somewhat resemble teeth marks in a chewed substance. The actual size of the embryo is 4 mm.
The appearance of the somites or “imprints” changes continuously, just as the teeth imprint changes on a chewed substance with each act of chewing. The embryo changes its overall shape, but the structures derived from the somites remain. Just as a substance acquires furrows, swellings and a corrugated surface as it is being chewed, so does the appearance of the embryo.
The embryo turns in its position due to the modifications in its centre of gravity with new tissue formation, similar to the turning of a substance with chewing.
The embryo looks somewhat like a chewed lump. The chewed appearance results from the somites which resemble teeth marks. The somites [cuboidal blocks of mesodermal tissue] represent the beginnings or primordia of the vertebrae. By the 3rd week of human embryonic development, about 38 pairs somites form. By the 5th week there are 42-44 pairs of somites. Most of the axial skeleton [skull, vertebral column, ribs, and sternum] and skeletal muscles will be derived from these somites.
As there were no microscopes available in the 7th century C.E., people would not have known that the human embryo had this chewed-like appearance. Professor Marshall Johnson states:
“You have to be really careful on what is the definition of ‘seeing’. I can see a piece of dandruff on this tabletop; I can just barely make it out because this is a nice black surface [but] I can see no detail in it. If I want to see detail in it then I need some sort of visual aid, something to aid my vision, I need a magnifying glass, I need a microscope. So I might be able to see a piece of dandruff, but to see any detail in it as is described in the Qur’an, I need an instrument that wasn’t developed until the 1700s.”
Stage 4: Bone Formation [Idham]
God continues, “...and We made [from] the lump [mudghah], bones, and We covered the bones with flesh” [23:14]. The mudghah or somite embryo is fashioned into bones which are clothed with flesh. Hamilton, Boyd and Mossman write that “the somites are the bases from which the greater part of the axial skeleton and musculature develop.”
The timing of this phase has been mentioned in the following statement of the Prophet Muhammad,
“When 42 nights [i.e. 6 weeks] have passed from the time of the nutfah [time of conception], God sends an angel to it, who shapes it and makes its ears, eyes, skin, muscles and bones…” 
“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.” 
The formation of the skeleton gives the embryo its human shape.
In the 6th week the cartilaginous skeleton begins to form and the embryo acquires a soft skeleton.
“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 centres appear in the femur during week 7 and in the sternum [breast bone] and the maxilla [upper jaw] in weeks 8-9.” 
Stage 5: Clothing the Bones with Flesh [Lahm]
“...We covered the bones with [lahm] flesh” [Surah Al-Mu'minun, 23:14]. In the Fundamentals of Human Embryology, it is noted that, “Soon after the cartilaginous models of the bones have been established, the myogenic cells, which have now become myoblasts, aggregate to form muscle masses on the ventral [front] and dorsal [back or posterior] aspects of the limbs.”  Although precursor cells [myoblasts, or primitive muscle cells] 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.” 
It is clear from the preceding pages that God, in the Qur’an, gives a detailed account of the development of the human embryo. Firstly, it accurately describes the main stages of development.
Each word describes the characteristic of a specific stage and its morphological and physiological identity. Secondly, it describes the sequence of these events in the same chronological order as discovered by the electron microscope.
 Moore, K. L., A Scientist’s Interpretation of References to Embryology in the Qur’an.
 Moore and Persaud, The Developing Human, 5th ed., p. 8.
 Moore and Persaud, The Developing Human, 5th ed., p. 82 – from Professor Hideo Nishimura, Kyoto University, Japan.
 This section is an edited version of Kareem, E., Embryology in the Qur’an: The Mudghah Stage and Some observations on the mudghah (chewed-like) stage of human development.
 As quoted in Kareem, E., Some observations on the mudghah stage of human development.
 Hamilton, Boyd, Mossman, Human Embryology, 4th Edition, as quoted in Albar, M. Ali, Human Development as revealed in the Holy Qur’an and Hadith, p. 79.
 Sahih Muslim, Kitab al-Qadr.
 G.C. Goeringer, A. A. Zindani, M. A. Ahmed, Embryology in the Qur’an: Bone and Muscle Development, www.islampapers.com.
 Allan, J., and Kramer, B., The Fundamentals of Human Embryology, 2nd Edition, Wits University Press, 2010, p. 148.
 G.C. Goeringer, A. A. Zindani, M. A. Ahmed, Embryology in the Qur’an: Bone and Muscle Development, www.islampapers.com
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