Conception + Fertility Flashcards
1
Q
What is the uterine menstrual cycle?
A
- Involves changes in the endometrium (the inner layer of the uterine wall, to enable it to receive a fertilised ovum
- Extensive blood supply is needed to support tissue growth, implantation of a fertilised ovum and development of a placenta (the organ which nourishes the foetus).
2
Q
What is the endometrium?
A
- The endometrium is composed of two layers. The functional outer layer is the stratum functionalis and the deeper basal layer is the stratum basale
- If implantation of a fertilised ovum does not occur, the stratum functionalis is shed during menstruation (first phase of the reproductive cycle). The stratum basale is permanent and gives rise to a new stratum functionalis after each menstruation
3
Q
What is the ovarian cycle?
A
- The ovarian cycle is a series of events in the ovary, during and after the maturation of an oocyte
4
Q
What does the ovarian cycle involve?
A
- The ovarian cycle involves: oogenesis (formation of gametes) and folliculogenesis: maturation of the ovarian follicle. These processes occur simultaneously in the ovary before birth.
5
Q
What is an oocyte?
A
- An oocyte is an immature egg cell (female gamete).
6
Q
What is an ovarian follicle?
A
- An ovarian follicle is a fluid-filled sac containing an oocyre at various stages of development, plus surrounding follicular cells supporting oocyte growth.
7
Q
What are the two phases of the ovarian cycle?
A
- The ovarian cycle is split into two phases: follicular phase (day 1 -14) is where the growth of the ovarian follicles occurs. Correlates with the menstrual and pre-ovulatory phases of the overall reproductive cycle. The luteal phase (15-28) represents the action of corpus luteum ceels. Correlates with the post-ovuylatory phase of the overall reproductive cycle.
8
Q
What is oogenesis?
A
- Oogenesis is the formation of gametes in the ovaries.
- During oogenesis, various cell division events occur such as mitosis, meiosis I, meosis II and maturation.
9
Q
What is the foetal period?
A
- In foetal development primordial germ cells (from the embryonic yolk sac) migrate to the foetal ovary and differentiate into diploid (2n) stem cells called oogonia
- Oogonia divide by mitosis to produce millions of germ cells but most degenerate in a process called atresia
- The surviving cells continue to develop into diploid primary oocytes.
10
Q
What happens at birth to oocytes?
A
- Primary oocytes begin meiosis but are arrested (paused) in prophase of meiosis I.
- Around 200,000 to 2 million primary oocytes are present at birth. The primary oocytes do not continue their development until puberty
11
Q
What happens to oocytes between puberty to menopause?
A
- Around 40,000 primary oocytes remain at puberty
- From puberty to menopause each month hormones cause meiosis I to resume in several follicles
12
Q
What is the process of maturation of the secondary oocyte?
A
- Primary oocyte completes meiosis I and forms two haploid (n) cells of unequal size – the smaller cell, called the first polar body is discarded and the remaining secondary oocyte enters meiosis II.
- The secondary oocyte is arrested in metaphase of meiosis II by ovulation
- Penetration by the sperm causes the final stages of meiosis II to occur in the final stages of meiosis II to occur in the secondary oocyte. It splits into another two haploid cells of unequal size
- The smaller second polar body is again discarded, and the remaining large ovum remains.
13
Q
What is folliculogenesis?
A
- Follicular development (folliculogenesis) occurs at the same time as oogenesis in the ovary.
- Follicles develop and increase in size from the primordial (during the foetal period) through to monthly development during puberty to primary, secondary and mature stages. Full maturation takes several months however each month, one dominant follicles reaches full maturity.
14
Q
What are the stages of follicular development?
A
- Primordial follicle: primordial follicle houses a primary oocyte with a layer of surrounding follicular cells.
- Stromal cells (CT) are attached to the basement membrane.
- The primary follicle houses a primary oocyte with several layers of granulosa cells (differentiated follicular cells). At the end of this stage also a layer of theca cells (differentiated stromal cells).
- Secondary follicle: houses a primary oocyte and several layers of granulosa and theca cells. The innermost layer of granulosa cells surrounding the zona pellucide form the corona radiata.
- Mature follicle: houses a secondary oocyte and several layers of granulosa and theca cells.
- Ovulation: the mature follicle ruptures to release the secondary oocyte along with the zona pellucide and coronoa radiata.
- Corpus haemorrhagicum: after ovulation, the ruptured follicle is called the corpus haemorrhagicum due to the damage of small blood vessels and filing of the ruptured follicle with a blood clot. Only the granulosa cells and stroma remain. The stroma continues to secrete hormones after ovulation.
- Corpus luteum and corpus albicans: is the remnants of the follicle after the secondary oocyte is expelled.
15
Q
What is infertility?
A
- Infertility is the inability to conceive after 12 months or more of unprotected sex.
- There are many reasons why pregnancy does not occur: 1. 20% male factors, 2. 30% female factors and 3. 50% both partners.
