Embryology Flashcards
Q: When does gamete formation occur in males and females?
Males: Starts at puberty and continues throughout life.
Females: Begins during fetal life, pauses, and resumes at puberty until menopause.
Q: What are the parts of a mature sperm?
Head: Contains the nucleus and acrosomal cap.
Neck: Connects the head and middle piece.
Middle piece: Contains mitochondria for energy.
Tail: Helps the sperm move toward the ovum.
Q: What is the function of the acrosomal cap in sperm?
A: It contains enzymes that help the sperm penetrate the ovum’s coverings.
Q: What are the coverings of the mature ovum?
Zona Pellucida: Glycoprotein coat with sperm receptors.
Corona Radiata: Outer layer of follicular cells.
Q: Where does fertilization occur?
A: In the ampulla of the uterine tube.
Q: What are the phases of fertilization?
Penetration of the corona radiata (hyaluronidase enzyme).
Penetration of the zona pellucida (acrosomal enzymes).
Fusion of sperm and oocyte plasma membranes.
Q: What are cortical and zona reactions?
Reactions that prevent polyspermy by:
Changing sperm-binding sites on the zona pellucida.
Making the oocyte membrane impenetrable to other sperm.
Q: What are the results of fertilization?
Formation of the zygote.
Restoration of the diploid chromosome number (46 chromosomes).
Determination of the zygote’s sex (XX or XY).
Initiation of cleavage and migration.
Q: What are the stages of early cleavage?
Day 1: 2-cell stage.
Day 2: 4-cell stage.
Day 3: 16-cell stage (morula).
Q: What is a blastocyst, and what are its components?
Outer cell mass (Trophoblast): Forms the placenta.
Inner cell mass (Embryoblast): Forms the embryo.
Blastocele: Fluid-filled cavity.
Embryonic pole: Near the embryoblast.
Abembryonic pole: Opposite side of the embryonic pole.
Q: What is in-vitro fertilization (IVF)?
A: Fertilization outside the body, with the embryo implanted into the uterus at the 8-cell stage.
Q: What is intracytoplasmic sperm injection (ICSI)?
A: Direct injection of a single sperm into the oocyte cytoplasm, used for low sperm count or penetration issues.
Q: What is gamete intrafallopian transfer (GIFT)?
A: Gametes are placed into the ampulla of the fallopian tube for natural fertilization.
Q: What is the size of a mature sperm?
A: A mature sperm is 55 microns long.
Q: What is the size of a mature ovum?
A: The diameter of a mature ovum is approximately 120 microns.
Q: What is the role of the zona pellucida?
A: The zona pellucida has sperm receptors that attract and bind sperms, facilitating fertilization.
Q: What enzyme helps the sperm penetrate the corona radiata?
A: The enzyme hyaluronidase dissolves hyaluronic acid between the corona radiata cells.
Q: What is the cortical reaction?
A: The cortical reaction prevents polyspermy by releasing lysosomal enzymes that alter sperm-binding sites on the zona pellucida.
Q: What are the pronuclei, and how are they formed?
A: The male and female pronuclei are formed when the sperm nucleus enlarges and fuses with the oocyte nucleus.
Q: How does the zygote migrate to the uterine cavity?
Peristalsis of the uterine tube muscles.
Motion of cilia lining the tube.
Mucus secretion providing nutrition and facilitating migration.
Q: When does the zona pellucida begin to degenerate?
A: At the end of the 5th day of development, allowing blastocyst formation.
Q: What are the key events of the first week of development?
Fertilization in the ampulla of the uterine tube.
Cleavage of the zygote.
Formation of the morula.
Migration to the uterine cavity.
Formation of the blastocyst.
Q: When does implantation occur?
A: It starts on the 7th day and is completed by the 11th day.
Q: Where does implantation usually occur?
A: In the endometrium of the upper part of the posterior wall of the uterus (near the fundus).
Note: It can also occur in the upper part of the anterior wall.