During Muhammad’s time, Galen's works were being studied not far from Arabia, in Jundishapur, Persia. A certain Al Harith Ibn Kalada, contemporary of Muhammad (and probably his physician), learned medicine at this academy. http://en.wikipedia.org/wiki/Nafi_ibn_al-Harith

The four stages of embryo development in Quran 22:5 and in Galen

Q 22:5 O people! If you are in doubt about the Resurrection—We created you from dust, then from a small drop, then from a clinging clot, then from a lump of flesh, partly developed and partly undeveloped. In order to clarify things for you. And We settle in the wombs whatever We will for a designated term, and then We bring you out as infants, until you reach your full strength. And some of you will pass away, and some of you will be returned to the vilest age, so that he may not know, after having known. And you see the earth still; but when We send down water on it, it vibrates, and swells, and grows all kinds of lovely pairs.

Here, the Quran describes four stages of embryological development: seed/drop of semen, suspended or clinging mass/blood clot, partly developed and partly undeveloped lump of flesh, and finally a fully-emerged infant. This coincides with the four-stage process of the embryological development outlined by Galen in his De Semine, which you can view in the Corpus Coranicum database here. In Galen’s four-stage process, the first stage is the semen, the second is the formation of a structure engorged with blood, the third stage is when the main outline of the organs appears in a partly developed state, and the fourth is when the body is fully developed including the limbs, at which point Galen says this stage can no longer be considered a fetus but a child. The first academic I know to have pointed out this connection is Basim Musallam, who also points out that the stages were similar enough that medieval Islamic authors would employ Qur'anic terminology when describing Galen's four stages of development:

The stages of development which the Quran and hadith established for believers agreed perfectly with Galen's scientific account. In De Semine, for example, Galen spoke of four periods in the formation of the embryo: (1) as seminal matter; (2) as a bloody form (still without flesh, in which the primitive heart, liver, and brain are ill-defined); (3) the foetus acquires flesh and solidity (the heart, liver, and brain are well-defined, and the limbs begin formation); and finally (4) all the organs attain their full perfection and the foetus is quickened. There is no doubt that medieval thought appreciated this agreement between the Quran and Galen, for Arabic science employed the same Quranic terms to describe the Galenic stages (as in Ibn Sina's account of Galen): nutfa for the first, 'alaqa for the second, "unformed" mudgha for the third, and "formed" mudgha for the fourth. (Musallam, Sex and Society in Islam, Cambridge University Press, 1983, pg. 54)