Embryonic Development

It is the meristem, that always differentiates, into ground tissue components, such as, cortex, endodermis and pith.

Hematopoiesis originates in the early yolk sac but as embryogenesis proceeds, this function is taken over by the fetal liver and spleen, then later by the bone marrow where it continues throughout life.

The placenta is an organ that connects the developing foetus to the uterine wall to allow nutrient uptake, provides thermo-regulation to the foetus, waste elimination and gas exchange via the mother's blood supply. It also fights against internal infection and produces hormones to support pregnancy.

 All cardiovascular systems including heart, blood vessels, lymph and blood cells have derived from mesoderm.

 Gastrulation is an early stage in human embryo, when the three germ layers are formed.

Primary meristem and secondary meristem are embryonic cells.

Periderm is composed of cork (phellem), the cork cambium (phellogen), and the phelloderm.

Implantation may be defined as the attachment of the fertilized egg to the uterine wall or in other words attaching the embryo with the uterus .It typically happens seven to ten days after ovulation, but it can happen a few days earlier or later as well.

The Polygonum type of embryo sac is the most common type in angiosperms. It is monosporic, meaning it develops from a single megaspore, and it contains eight nuclei.

In an ovule, the seed coat consists of two layers: the outer testa (from the outer integument) and the inner tegmen (from the inner integument).

   Radial Cleavage is found in Deuterostomes.

 None of the above mentioned structure is formed by Ectoderm.

 Central nervous system is formed by Ectoderm.

In gonadal development, undifferentiated primordial germ cells arise from the endoderm lining the yolk sac.

Mesenchyme arising beneath the germinal epithelium in the testes is the precursor to testicular interstitial cells or Leydig cells. In the ovaries it is the precursor to ovarian stroma or thecal cells.