deck_1854536 Flashcards
What are gametes produced from?
From germ cells which have been separated from somatic cells at a very early age. The germ cells proliferate by mitosis and undergo genetic reshuffling before being reduced to haploids by meiosis
Where do germ cells colonise in the female?
The gonadal cortex
What do germ cells become in females?
Oogonia
When do you find the highest number of oogonia?
In the middle of the gestation of that woman
How many oogonias enter meiosis before the birth of that individual?
2 million– started with 7 million
How far in meiosis will the oogonias progress?
The will only reach the prophase of the first division before they will stop.
Why does meiosis stop?
The release of oocyte maturation inhibitor prevents the further progression of meiosis.
What are the oogonias known as once they have started meiosis?
Primary oocytes
What is a primordial follicle?
Follicular cells surround the oocyte forming a multi-layered epithelium which are then known as granulosa cells. The granulosa cells secrete glycoproteins which form a zona pellucida. Connective tissue cells surrounding the follicle form a theca folliculi which is made up of two parts.
What are the two layers of theca folliculi?
Theca interna – is vascular and endocrineTheca externa – is a fibrous capsule
What do the theca and granulosa cells do?
They collaborate to secrete oestrogens
How is a gamete matured in order for it to be fertilised?
The follicle goes through three stages of development1. Pre-antral/primordial2. Antral3. Pre-ovulatory
What is ovulation?
The process through which an ovum is released. Begins the 36 hour period in which a woman is fertile per month.
What has to happen before ovulation can take place?
The ovum developsThe reproductive tract is prepared for sperm transport and conceptus implantationChanges also occur in the body that help to maximise conception
What happens to prevent the release of extra gametes?
Gamete production is stopped after the initial release of a gamete as a fertilised oocyte is not larger enough to signal its presence. This prevent the fertilisation of another gametes. The pregnancy is confirmed by the release of placental hormone. This is known as the period of waiting.
Why does menstruation occur?
It occurs at the end of an unsuccessful reproductive cycle.
Describe the menstrual cycle
is about 28 days long. The first day of bleeding signals the start of the cycle, initiating the preparatory phase (follicular or proliferative phase), ovulation occurs around days 12-14 and the waiting phase (luteal or secretory phase) occurs from days 14-28.
What are the different stages of menstrual cycle?
Preparatory phase (0-12 days)Ovulation (at around 12-14 days)Waiting phase (days 14-28)
How do primordial follicles develop into antral follicles?
Granulosa cells secrete a fluid which causes the formation of the antral space. Initially, it is independent of hormones, but in order to get to teh sizes required, FSH and LH will stimulate.
What cells does FSH bind to?
Granulosa cells
What cells do LH bind to?
Thecal cells
What does the binding of LH stimulate?
The release of androgens from thecal cells which are converted to oestrogen by granulosa cells, due to FSH
What stimulates ovulation?
An increase in LH levels which stimulate meiosis to being again.
What is produced after the first division of meiosis?
One daughter cell which receives all the cytoplasm and a polar body which only contains DNA.
What happens after ovulation to the follicle?
It reorganises to form a corpus luteum because of LH presence. It the secretes oestrogen and progesterone.
What is the purpose of the corpus luteum secreting oestrogen and progesterone?
It prevents the release of further oocytes. If pregnancy occurs, then it will continue to prevent further release. If pregnancy does not occur, then it undergoes apoptosis.
What is the rout of the released oocyte?
It travels from the pre-ovarian peritoneal cavity to the uterine cavity, via the fallopian tubes.
Describe the structure of the ovaries
– almond shaped and sized female glands – where the oocytes develop as well as endocrine glands which produce reproductive hormones. – — is suspended by a short peritoneal fold which contains the short ovarian ligament which connects the ovary to the uterus.
Describe the outer structure of the ovary
They have a connective tissue capsule, which is known as the tunica albuginea of the ovary. It is covered by a smooth layer of ovarian mesothelium, which has a dull, greyish appearance.
What can happen to ovaries as women age?
It becomes progressive more scarred over time due to the repeated rupture of ovarian follicles and discharge of oocytes during ovulation.
