Pre embryonic development

Pre embryonic development of the embryo during pregnancy

1. Pre-embryonic Development Vihari Vichakshana Rajaguru 1 st year 2 nd semester KURSK State Medical University 1

2. Context Introduction Human Gestation First trimester Second trimester Third trimester After birth 2

3. Introduction  The fetal period extends from weeks 9–38, and is a time of rapid growth of body structures established in the embryo.  During the first half of the fetal period, cells are still differentiating into specific cell types to form the body’s distinctive tissues. 3

4. Human Gestation Gestation  is the carrying of an embryo or fetus inside female viviparous animals, including mammals, as well as some non-mammalian species. Mammals during pregnancy can have one or more gestations at the same time 4

5. Human gestation is divided into three trimesters. Each of about 3 months duration First trimester Second trimester Third trimester 5

6. First trimester Main period of organogenesis ( development of organs ) After eight weeks the embryo develops into the fetus and possesses all organs of the adult in rudimentary form. The fetus is 5cm long at the end of the 1 st trimester. By the end of the trimester fetus is recognizably human. 6

7. 7 8 weeks fetus ultrasound

8. The external genital structures have differentiated, indicating the sex of the fetus. Ears and eyes approach their final positioning. Some of the skeleton becomes distinct, and the notochord has been replaced by the developing vertebral column. 8

9. The fetus performs breathing movements, pumping amniotic fluid into and out of its lungs, and even carries on sucking movements. By the end of the third month, the fetus is almost 56mm long and weighs about 14g. 9

10. Second trimester Rapid growth occurs and the fetus is very active. Fetus grows rapidly about 30cm in length. Uterus grows sufficiently for the pregnancy to become obvious. The fetal heart beat can be heard with a stethoscope. Fetus moves freely through the amniotic cavity. 5 th month, the mother usually becomes aware of fetal movements. 10

11. 11 End of 5 th month ultrasound End of 6 th month fetus

12. Third trimester Growth is rapid and fetal activity decrease. Fetus grows to about 50cm in length and 3 to 3.5 kg in weight. Maternal abdominal organs become compressed and displaced. Final differentiation of tissues and organs occurs. 12

13. If born prematurely during this stage, the fetus attempts to breath and is able to move and cry but almost always dies because its brain is not sufficiently developed to sustain vital functions such as rhythmic breathing and regulation of body temperature. Cerebrum grows rapidly and develops convolutions. Grasp and sucking reflexes are evident, and the fetus may suck its thumb. 13

14. 14 8 months old fetus

15. After birth…. After birth the average full-term baby weighs about 3kg and measures about 52 cm in total length. Any infant born before 37 weeks gestation is considered as premature. 15

16. Thank you !! 16