Ovulation, Conception and Implantation Flashcards
How many chromosomes do oocytes contain?
46
What is the primary oocyte contained within?
The pregranulosa cells, surrounded by the outer basal lamina layer.
What are the three layers of primary follicles?
- Primary oocyte in centre
- Zona pellucida
- Cuboidal shaped granulosa cells
What do granulosa cells secrete? (2)
- Material that becomes zona pellucida
2. Oestrogen
What is the name of the further surrounding layer that primary follicles develop as they grow?
Theca folliculi.
What is the inner layer of the theca folliculi called?
Theca interna.
What does the theca interna secrete?
Androgen hormones.
What is the outer layer of the theca folliculi called?
Theca externa.
What is the theca externa made up of?
Connective tissue cells containing smooth muscle and collagen.
What happens when primary follicles become secondary follicles? (2)
- Grow larger and develop small fluid-filled gaps between the granulosa cells.
- Develop FSH receptors
What happens to create antral follicles?
Secondary follicles develop a single large fluid-filled area within the granulosa cells.
Follicles expand rapidly.
What is the corona radiata in antral follicles?
Corona radiata is made of granulosa cells and surrounds the zona pellucida and oocyte.
What happens when there is a surge in LH from the pituitary? (2)
- Smooth muscle of the theca externa squeeze, and follicle bursts
- Follicular cells release digestive enzymes which puncture hole in wall of ovary.
Describe the location of the ovum immediately after it is released from the ovary.
Floating in peritoneal cavity but is quickly swept up by fimbriae of fallopian tubes.
In the corpus luteum, what do the granulosa and theca interna cells become?
Luteal cells
What do luteal cells secrete?
Steroid hormones (mainly progesterone).
How long after a failed fertilisation attempt does the corpus luteum degenerate?
10-14 days
When does the primary oocyte undergo meiosis?
Around time of ovulation.
Describe what happens when the primary oocyte undergoes meiosis.
Cell splits from diploid to haploid and the other 23 chromosomes float off to the side and becomes the first polar body.
When does a primary oocyte become a secondary oocyte?
When it undergoes meiosis
When does the second polar body form?
When a sperm enters the egg, the 23 chromosomes of the egg multiply into two sets. One set of 23 chromosomes combine with the 23 chromosomes from the sperm to form a diploid set of 46 chromosomes, and the other set of 23 chromosomes float off to the side and create the second polar body.
What does the combination of the 23 chromosomes from the egg and the 23 chromosomes from the sperm form?
Zygote
What does the zygote form after it divides rapidly?
Morula
Where does the morula form?
As the mass of cells travels along the fallopian tube.
What does the morula become when a fluid-filled cavity gathers within the group of cells as it travels along the fallopian tube?
Blastocyst.
What is a blastocyst composed of?
Embryoblast and fluid-filled cavity called blastocele.
Surrounding these is outer layer called trophoblast.
How many cells does the blastocyst contain when it enters the uterus?
100-150
How many days after ovulation does the blastocyst arrive at the uterus?
8-10 days after ovulation.
What is the outer layer of the tropholast called?
Syncytiotrophoblast
What does the syncytiotrophoblast do?
Forms projections into the stroma of the endometrium, the cells mix and so blastocyst is attached.
What do the cells of the stroma convert into when the blastocyst attaches.
Decidua that is specialised in providing nutrients to the trophoblast.
What produces HCG?
Syncytiotrophoblast
