Embryology and Prenatal Development

Practice questions covering human embryology including fertilization, germ layer derivatives, placental anatomy, and clinical conditions like spina bifida.

What are the three stages of prenatal development and their corresponding timeframes?

Pre-embryonic (weeks 1 and 2), embryonic (weeks 3 to 8), and fetal (week 9 to birth).

In what specific location does fertilization typically occur?

The ampulla of the fallopian tube.

What is the term for the fertilized egg as it moves toward the uterus?

Conceptus.

What is the name of the process where mitotic cell division produces daughter cells called blastomeres without increasing the overall size?

Cleavage.

What is a 'morula' and when does it typically arrive in the uterus?

A morula is a solid ball of cells shaped like a mulberry ($16$ cells) that arrives in the uterus approximately 3 days after fertilization.

What are the two parts of a blastocyst and what do they eventually become?

The trophoblast (outer layer that nourishes the embryo) and the inner cell mass or embryoblast (becomes the embryo).

What enzyme-secreting structure fuses with the endometrium to help the blastocyst implant?

The synctiotrophoblast.

Which hormone does the blastocyst secrete to instruct the corpus luteum to continue progesterone production?

HCG (Human Chorionic Gonadotropin).

During Week 2, the embryonic disc differentiates into which two layers?

The hypoblast and the epiblast.

What are the four embryonic membranes?

Amnion, allantois, yolk sac, and chorion.

What process occurs during Week 3 to turn a 2-layered disc into a 3-layered disc?

Gastrulation.

Which germ layer gives rise to the nervous system, epidermis, hair, and nails?

Ectoderm.

Which germ layer gives rise to the skeleton, muscles, heart, blood vessels, and kidneys?

Mesoderm.

Which germ layer gives rise to the gastrointestinal tract, liver, pancreas, and lungs?

Endoderm.

What are the two main types of cells produced during the differentiation of a spermatogonium?

One cell remains a germ cell (spermatogonium) and the other becomes a sperm cell.

What is the chromosomal difference between Meiosis I and Meiosis II in spermatogenesis?

Meiosis I converts primary spermatocytes ($23$ pairs of chromosomes) to secondary spermatocytes; Meiosis II produces spermatids with $23$ single chromatids.

At what stage does the oocyte enter mitotic arrest in females?

At birth, the primary oocytes are in meiotic arrest until puberty.

Which part of the sperm contains the DNA and is covered by the acrosome?

The head.

What is the purpose of the cortical reaction during fertilization?

It creates a block to polyspermy, preventing multiple sperm from binding to the egg.

In the umbilical cord, what is the function of the umbilical vein versus the umbilical arteries?

The umbilical vein carries oxygenated blood and nutrients to the fetus, while the two umbilical arteries carry deoxygenated blood away from the fetus.

What is 'Wharton's Jelly'?

The gelatinous substance found within the umbilical cord.

Which part of the placenta is associated with the mother and which is associated with the fetus?

The basal plate is the maternal side; the chorionic plate is the fetal side.

What structure forms under the primitive streak to induce the formation of the neural plate?

The notochord.

What are neural crest cells?

Cells that break off during the formation of the neural tube to form other structures.

What are the characteristics of Spina Bifida Occulta?

A small hole or dimple, often marked by a tuft of hair, with no symptoms.

What protein leaks into the amniotic fluid and maternal blood used to diagnose neural tube defects?

AFP (alpha-fetoprotein).

Which cranial nerve supplies the first pharyngeal arch?

Trigeminal nerve (Cranial Nerve V).

Which pharyngeal arch supplies the facial nerve (Cranial Nerve VII)?

The second arch.

The external auditory canal is a derivative of which pharyngeal structure?

The first pharyngeal cleft (groove).

Which organ is derived from the second pharyngeal pouch?

The palatine tonsil.