Flashcards in Fertilisation & Conception Deck (24):
Name FOUR factors which can influence fertility
Environmental & Lifestyle
Name the NINE stages of conception
Cervical Mucus Changes
Penetration of Zona Pellucida
Fusion of the Oocyte and Sperm
Following fertilisation (day 0), describe the changes that occur through to the end of day 9
The fertilised egg or zygote undergoes cleavage
It has developed to the 2-cell stage
It has developed to the 4-cell stage
Changes from an 8-cell UNcompacted morula to an 8-cell COMPACTED morula
Has developed into an early blastocyst with an inner cell mass
Developed into a late-stage blastocyst and zona pellucida falls away
Implantation of the blastocyst occurs
When does the Acrosome Reaction occur?
As the sperm contacts the Zona Pellucida
Which reactions block any additional sperm from entering the oocyte?
The Cortical Reaction and the Zona Reaction
What is capacitation?
The process of maturation of sperm when glycoproteins are removed from the surface of the acrosome cap while it travels through the uterus or uterine tubes
Describe the Acrosome Reaction
The lytic (digestive) enzymes from many sperm disperse the corona radiata allowing the head of one sperm to make contact with the zona pellucida
Describe the Cortical Reaction
This process consists of the secretion of cortical granules into the space between the plasma membrane and the zona pellucida This renders the membrane of the oocyte impermeable for other sperm cells.
Describe the Zona Reaction
The reaction that occurs following the Cortical Reaction, which prevents other sperm cells from penetrating the membrane of the oocyte
How often do cell divisions occur?
Every 12-15 hours
Name the FOUR components of a blastocyst
1. Zona pellucida – thick glycoprotein membrane
2. Trophoblast – one cell thick, outer layer of cells
3. Inner cell mass – 1-2 cell thick, crescent shaped cluster of cells
4. Fluid filled cavity
What is Gastrulation?
Inner cell mass differentiates into 3 layers after implanting when individual organs develop within the newly formed gem layers
What does the ECTODERM develop into?
The skin, nails, the epithelium of the nose, mouth and anal canal; the lens of the eye, the retina and the nervous system
What does the ENDODERM develop into?
The inner linings of the digestive tract, as well as the linings of the respiratory passages. It also forms many glands, such as the liver and pancreas.
What does the MESODERM develop into?
The somites, the notochord, and the mesenchyme, which give rise to the muscles, circulatory and excretory systems of the body.
When does the fetal heart start to beat?
At 22 days
When is the embryonic period?
From 2-8 weeks
When is the fetal period?
From 8 weeks to full term
From which week is the fetus fully formed?
At 29 weeks
What is the syncytiotrophoblast?
Inner layer of the trophoblast
What is the cytotrophoblast?
Outer layer of the trophoblast
By when is the placenta fully formed and functioning?
By when has the placenta reached full thickness?