Question

How does your anatomy change during pregnancy?

Answer 1

When a male gamete fuses with a female gamete to form a diploid zygote, it leads to development of embryo from the fertilised ovum. This embryo is further developed into a full fledged organism inside the uterus (womb) of the female body. This is called the gestation period which lasts up to 9 months in humans.

Complete answer:
During pregnancy, the female body undergoes various changes ranging from physical to anatomical. The development of embryo takes place in the uterus of the female. The uterus is located between the urinary bladder and the rectum and has the shape and size of an inverted pear. In females who have never been pregnant, the uterus is about 7.5 cm long, 2.5 cm thick, and 5 cm wide. The uterus becomes larger in females who have recently been pregnant. The wall of the uterus has three layers: internal glandular endometrium, middle muscular myometrium and outer membranous perimetrium.

During the embryonic development of embryo, it undergoes cleavage divisions to form a morula which is 8-16 cells (occasionally 32 cells). Morula enters the uterus, where endometrium secretes a nutrient fluid called uterine milk which helps in growth of morula. They form trophoblast which secretes a fluid and creates a cavity called blastocoel. Here, the morula is converted to blastocyst which gets embedded on the endometrium wall of the uterus; this process is called implantation. Implantation begins around the seventh day of fertilisation and takes around three days to be completed. Implantation causes nutrient enrichment, enlargement of cells and formation of the uterine part of the placenta called decidua.

The hormone human chorionic gonadotropin (hCG) is secreted after implantation which maintains corpus luteum beyond its life. They prevent menstruation, stimulate endometrium to grow and store nutrients and plug the passage to the cervix through viscous secretion. The uterus increases from its non-pregnant mass of 60–80 g to 900–1200 g at term because of hyperplasia of muscle fibers in the myometrium in early pregnancy and hypertrophy of muscle fibers during the second and third trimesters.

Note: Trophoblast covering secretes a hormone called human chorionic gonadotropin (hCG) which can be detected in the urine of females within a day or so after implantation.