Human Development: Germinal and Embryonic Stages

What are the three stages of fetal development?

What is the first stage of fetal development called?

What structure is formed when a sperm fertilizes an egg?

What forms from the inner cell mass of the blastocyst?

What is the function of the placenta?

Which of the following are germinal layers formed during fetal development? (Select all that apply)

What occurs during the embryonic stage?

At what week does the heart start beating?

What is formed around the fifth to sixth week of pregnancy?

When does the fetal stage begin?

Germinal Stage

Begins at conception with fertilization of the egg by a sperm in the fallopian tube. This creates a zygote, which travels to the uterus.
The zygote divides mitotically (cell division) from 2-celled stage to 8-16 celled stage
The 8-16 cell stage is referred to as a morula.
The morula continues to divide and forms a blastocyst.
The outer layer of the blastocyst is called the trophoblast, which embeds into the uterine wall (endometrium). This begins in week one and completes in week two
The inner cell mass of the blastocyst forms the embryo
The trophoblast and uterine cells form the placenta.
The placenta acts as an endocrine gland and secretes hormones such as human chorionic gonadotropin (hCG), estrogen, and progesterone to support pregnancy.
Gastrulation is the development of the three primary germ layers: ectoderm, mesoderm and endoderm.
The germ layers give rise to every tissue and organ in the body.

Embryonic Stage

Occurs from the third to the eighth week
The blastocyst develops human characteristics and is referred to as an embryo.
Key structures and organs form during these weeks:
- Brain and spinal cord (from neural tube)
- Head, eyes, mouth
- Limbs
The fetal heart begins to beat around weeks 5-6
Arm and leg buds form around the sixth week.
By the end of the eighth week, most organs and systems have taken form.

Fetal Stage

Begins in the ninth week and continues until birth.

This quiz explores the germinal and embryonic stages of human development, beginning from the fertilization of the egg to the formation of the blastocyst and placenta. It highlights key processes such as cell division, gastrulation, and the role of trophoblast in embedding into the uterine wall. Test your knowledge on the critical early stages of human development!