Human development after the  forty second day

 

        Prophet Mohammad (peace and blessings be upon him) mentioned the developmental events of embryo after the 42nd  day and their timing in the following hadith which was narrated by Hudhaifah Ibn Usiad  El-Ghifari  : " When 42 nights have passed over the nutfah ( a drop of mingled fluid ), God sends an angel to it, who shapes it (into human form) and makes its hearing, sight, skin, muscles and bones. Then he says, "O Lord, is it male or female?" and your Lord decides what He wishes and the angel records it .  Then the angel goes out with  this document of destiny of this nutfah in his hand  and does not add to the received orders or subtract from them  " (Sahih Muslim : Book of destiny , in Arabic called  Kitab Al-Qadar).

 

        This hadith determines the importance of the 42nd day , as embryological studies have shown that prior to the 42nd  day, it is difficult to distinguish the human embryo's appearance from the appearance of embryos of many other species such as the chicken, fish, or rabbit and that acquiring the human appearance occurs exactly after the 42nd  day in the intrauterine prenatal development.

 

      The 7th  week of development (after the 42nd day) marks a time of several eventful changes in the external and internal features of the embryo : 

 

      With the beginning of the 7th  week ( about the time of the 42nd  day ) , an osteocartilaginous skeleton is formed in the embryo. The trunk of the embryo becomes straight and the embryo now has a relatively large and rounded head .The eyes move to the front of the face in their specific position and the face acquires a human shape, i.e. it has been formed . The internal and external parts of the ear are formed after the 42nd  day in a shape similar to that of the human, and the nose is also recognizably human.  Limb buds which made their appearance towards the end of the 4th  week are now (after the 42nd  day) longer and show clearly defined fingers and toes which were not present before. The prominent tail bud has regressed, leaving a rudiment that is barely conspicuous. 

 

       The previous features are exactly in accordance with the description of the previous hadith in that it describes what happens to the nutfah  ( a drop of mingled fluid) after the 42nd  day gives where it changes into an embryo having a characteristic human form, and this was described in the hadith by the  Arabic  word swaraha that mean  shaping into  a recognizable  human being...

 

       The reference to hearing and sight in the hadith ,  indicates  that the development of their organs ,  the ears  and eyes respectively , and the initial changes necessary for their functioning occur after the 42nd  day. Scientifically , the eyes and ears continue to develop advanced features after the 42nd  day :

The eye ; the optic stalk between the eye and brain undergoes changes which result in the formation of the optic nerve between the 6th  and 8th  weeks . At 11 weeks of development, even though the size of the eye is the size of a small bean, it shows more advanced features such as the cornea. By the 7th  month, the retina is light sensitive, but perception of form and color develops only shortly after birth.

The ear ; by the end of the 7th  week,( or 49th  day), the cochlea coils of the ear are already established and to a large extent resemble the adult form. Chondrification of the precartilage ear ossicles begins about this time and the auricle is formed from three pairs of tubercles . It has been suggested that the fetus can hear sounds after the 24th  week. .Thus the external, middle and internal parts of the ear are not formed until after the 42nd  day and then acquire their function and recognizable shape. This explains why  the 7th  and 8th weeks are critical periods for the embryonic development of the ear , supporting this view is that rubella infection at this time can cause maldevelopment of the organ of Corti and a resulting defect in hearing .

 

      The reference to formation of the skin in the hadith ,  indicates  that the development of the skin  and completion of its  necessary  structure for its function occur after the 42nd  day. Scientifically , the formation of skin involves its differentiation into its layers, sebaceous and sweat glands, and  hair, and it also includes the development of its sensory functions through innervation. The process of differentiating into layers begins in the 7th  week and formation of the glands and hair occur a few weeks later. Sensitivity to touch, pain, and temperature, which would indicate that innervation has occurred, is present after the 42nd  day.

 

        Moreover , the hadith  refers to the formation of muscles and bones after the 42nd day  . This is in accordance with the fact that the cartilaginous skeleton is formed, and ossification begins, in the 7th  week, and myogenesis, which results in muscle formation around the bones, begins in the 8th  week. These processes serve to straighten and smooth the embryo's body and contribute to the development of the human shape. A fetus between the age of 6 and 7 weeks will show an entire body response if the lip area is gently stroked. Spontaneous movements such as squinting and swallowing appear much later between the 9th  and 10th  week.

 

       With regard to the sex of the embryo, this hadith states that the angel asks for Allah's permission to shape the conceptus into a male or a female once ears, eyes, flesh, bones and skin develop. Then Allah grants him the permission to do so. The most probable explanation to the question of the angel  about  shaping the fetus into  a male or a female,  is about the shaping of the  external genital organs of this fetus, as the fetus at this developmental stage could  have external genital organs that contradict the sex determined by the sex chromosomes .  An evidence supporting this opinion  is that the development of external genital organs of the fetus sometimes occur opposite to the sex determined by the sex chromosomes i.e. the fetus could be a male (XY) according to sex chromosomes but has a female external genital organs , or oppositely the fetus could be a female (XX) according to sex chromosomes but has a male external genital organs .This defective development occurs either due to defective receptors to male hormones in male fetus (XY) which prevents the effects of these hormone and keeps its genitals feminine or due to absence of an inhibitory factor to male hormones in female fetus (XX) which  makes its genitals to appear masculine.   

    

        It is well-known scientifically that  the external genital organs begin their development  during the 4th week i.e. before the 42nd day. Their  primordia  are the same in both male and female , where the genital tubercle, labioscrotal swellings and urogenital folds do not evolve into distinguishing sexual characteristics until the 9th  week. However, the external genitalia are not clearly distinguishable as male or female until the 12th week . According to these data , it is clear that use of the conjunction "then"  “thumma in Arabic”   indicates  a delay in the occurrence of this sexual differentiation for  a period of time after the development of "ears, eyes, skin, flesh and bones " , and this delay in the sequence of external sexual differentiation  , as we described above , is in accordance with  its order of frequency in  modern embryology . Who taught our sir Mohammad , peace and blessings be upon him , all these data ??  Who told him all these accurate details about embryological development ?? He is Allah , the -Al-mighty , and no one except Him , Allah said in Qura'n : chapter 67 ; verse 14 : Should He not Know what He created ? He is the knower  of all Subtleties, the All-Aware"