: By the fourth month, the placenta grows in parallel with the uterus, eventually becoming a spongy, disc-shaped organ about 20 cm in diameter. Core Functions of the Placenta
The fertilized egg divides as it moves toward the uterus. By day 5, it becomes a blastocyst.
—the only organ that is grown by one person to support another, then discarded after its job is done. 1. The Early Spark: Implantation and Trophoblasts Development Of Placenta Ppt
Blood vessels develop within the mesodermal core, establishing a connection to the fetal heart. 5. Development of the Intervillous Space
The placenta is a unique, temporary organ that acts as the primary life-support system for a developing fetus : By the fourth month, the placenta grows
As the placenta establishes itself, it creates "villi"—finger-like projections that maximize the surface area for nutrient exchange. Primary Villi: Simple columns of cytotrophoblast cells. Secondary Villi:
: Produces hormones like hCG, progesterone, and estrogen that are necessary to maintain the pregnancy. —the only organ that is grown by one
Click to show Tertiary Villus. – By day 21, the most important event happens: the mesoderm differentiates into fetal capillaries. Now the villus contains fetal blood. This is the functional exchange unit. This is when the placenta truly becomes a life-support system for the embryo."
A single slide with a simple timeline graphic:
Extraembryonic mesoderm grows into the primary villi.