Page 64 - كتاب تمريض نسا الاكتروني

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• The fertilized ovum “zygote” divides into 2,4,8……the cells called “blastomeres”,

this division “cleavage” starts within 24 hours of fertilization and occurs nearly

every 12 hours repeatedly, the resultant 16 cells mass is called morula and reach

the uterine cavity after about 4 days from fertilization.

 Morula is differentiated into two parts:

• The inner mass consists of embryonic cells

• Outer Layer is the trophoblast.

 The embryonic cells are differentiated into three layers:

1. ECTODERM which will form the skin, nervous system and the special sense

organs as eyes, ears, taste and smell organs.

2. MESODERM which will give muscles, bones, connective tissue, circulatory and

urogenital systems.

3. ENDODERM which will give the digestive and respiratory systems.

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