--Felicia Ton 23:16, 4 August 2010 (UTC)
--Felicia Ton 23:05, 11 August 2010 (UTC)
--Felicia Ton 23:16, 18 August 2010 (UTC)
Individual Assessment - Lab Questions
1. What factor do the syncytiotrophoblast cells secrete to support the ongoing pregnancy?
Shortly after implantation of the blastocyst within the endometrium, the syncytiotrophoblast cells secrete the hormone human Chorionic Gonadotopin (hCG) which stimulates the corpus luteum. hCG supports the ongoing pregnancy by stimulating the corpus luteum to produce increased levels of the essential progesterone and estrogen hormones, thereby preventing menstruation and proliferation of the endometrium. hCG is continually secreted throughout the pregnancy however only at low levels for the final half of the pregnancy.
2. What does the corpus luteum secrete to prevent continuation of the menstrual cycle?
The corpus luteum secretes both progesterone and estrogen, however it is primarily the elevated levels of progesterone that maintain stimulation of the endometrial cells.
1. What Carnegie stages occur during week 3 and week 4?
Carnergie stage 7 to stage 13.
2. What is the change in overall embryo size form the beginning of week 3 to the end of week 4?
The overall change would be between 2.6mm and 4.6mm
3. Approximately when do the cranial (anterior) and caudal (posterior) neuropores close in the human embryo?
The cranial neuropore closes at carnegie stage 11 (23-26 days)
1. Name the vessels that drain into the sinus venosus
The umbilical and vitelline veins, and the cardinal vein
2. What is the fate of the vitelline artery and vitelline vein?
The vitelline artery forms part of the arteries of the GIT and the vitelline veins the portal system
3. Name the 4 layers that constitute the placental barrier
The syncytiotrophoblast, cytotrophoblast, villi connective tissues and fetal capillary endothelial layers
4. What stem cells are found in abundance, and may be harvested from the placenta for therapeutic uses?
Haematopoetic stem cells