W35 L1 - Embryonic Development: Fertilization to

Flashcards covering key concepts from the lecture on embryonic development, focusing on sperm maturation, fertilization and early embryonic development

What is the state of sperm taken directly from the testes?

Morphologically complete but not yet competent to fertilize an egg.

Where do the final stages of sperm maturation occur?

Within the epididymis and even within the female tract itself.

What supports the reproductive tract and helps protect sperm DNA from damage?

A fluid mixture secreted by the prostate gland and the seminal vesicles that meet with the sperm upon ejaculation.

What are the cellular components of semen?

Mature sperm, epithelial cells sloughed from the urogenital tract, and round cells (leukocytes or dead immature germ cells).

What do the fluid components of semen provide to the sperm?

Antioxidants to protect DNA, a buffer to maintain the correct pH, and nutrition (fructose, sorbitol).

How is the vagina initially hostile to sperm?

Low pH (around pH 4), acting as a barrier to infection and selecting healthy sperm.

How does cervical mucus act as a barrier to sperm?

In the fertile period, estrogen stimulates watery mucus that sperm can swim through; progesterone inhibits this, forming thick mucus.

What is capacitation?

Changes in the plasma membrane of the sperm, entry of bicarbonate and calcium, and shedding of cholesterol, preparing the sperm to fuse with the egg.

What are the key enzymes released from the acrosome to digest a way through the corona radiata and zona pellucida?

Hyaluronidase and acrosine.

What event is triggered as the sperm enters the egg to prevent polyspermy?

The cortical reaction, where granules are released to harden the zona pellucida and prevent further sperm entry.

What specific chemical signal does the sperm bring into the egg to trigger its activation?

PLC zeta (phospholipase C zeta), an enzyme released by the sperm that triggers cyclical calcium release in the egg and initiates meiosis.

What is visible in the zygote after the sperm has entered the egg and the chromatin has decondensed?

Two pronuclei (one containing the female chromosomes and one containing the male chromosomes).

What happens during compaction at the morula stage?

Cells start to express cell adhesion molecules, sticking together tightly and making it harder to dissociate.

What two groups of cells differentiate during the blastocyst stage?

Trophectoderm (becomes the placenta) and the inner cell mass (becomes the embryo).

Which structures primarily provide hormonal support (estrogen and progesterone) during the different trimesters of pregnancy?

First trimester: corpus luteum; Second and third trimesters: placenta.

What hormone produced by the developing placenta tells the Corpus Luteum to remain active?

Human Chorionic Gonadotropin (hCG)

How does hCG prevent degeneration of the corpus luteum?

It is chemically equivalent to LH.

What hormone is used to detect a pregnancy?

Detecting hCG in the mother's urine.

What hormone is important in late pregnancy to help prepare the mother's body for lactation and birth, and what are its other names?

Human Placental Lactogen (hPL) / Human Chorionic Somatomammotropin.

What triggers uterine contractions during the birthing process?

Mechanical signaling due to the fetus dropping head down into the pelvis, hormonal signals, and feedback loops involving factors like relaxin, oxytocin, and prostaglandins.