Fertilization and Early Development - Anatomy and Physiology
- What happens during the acrosome reaction?
- The acrosome releases enzymes that digest a path through the zona pellucida so the sperm can reach the oocyte membrane.
- What does sperm entry trigger in the secondary oocyte?
- Completion of meiosis II, producing the ovum and a second polar body.
- Which part of the blastocyst gives rise to the embryo itself?
- The inner cell mass (embryoblast).
- What is cleavage in early development?
- Rapid mitotic divisions of the zygote without overall growth, so the cells (blastomeres) become smaller with each division.
- Which trophoblast layer invades the endometrium during implantation?
- The syncytiotrophoblast, a multinucleated layer that digests its way into the uterine wall.
- What does gastrulation produce?
- The three primary germ layers: ectoderm, mesoderm, and endoderm.
- About how many days after fertilization does implantation begin?
- About 6 to 7 days after fertilization, when the blastocyst attaches to the endometrium.
- What is a morula?
- A solid ball of about 16 or more blastomeres, reached about 3 to 4 days after fertilization.
- Which part of the blastocyst gives rise to the fetal portion of the placenta?
- The trophoblast, which forms the chorion.
- From which primary germ layer does the nervous system develop?
- Ectoderm, which also forms the epidermis.
- What is capacitation?
- The changes sperm undergo in the female tract, including loss of membrane cholesterol, that make them able to undergo the acrosome reaction and fertilize.
- What is the cortical reaction, and what does it prevent?
- Cortical granules release enzymes that alter the zona pellucida after sperm entry, blocking polyspermy (entry of additional sperm).