Flashcards in Anatomy and physiology Deck (28):
What is the development of eggs in the fetus -> birth?
1. 4th week gestation - primordial germ cells appear in yolk sac
2. 16th week gestation - clumped cells become primary follicles
3. They undergo mitotic division and by 20 weeks gestation, there are 7 million oogonia. After this, no further cell division occurs and no more ova are produced.
4. By birth, the oogonia have begun the first meiotic division and are primary oocytes
5. From birth onwards, the number of primary oocytes falls progressively
By birth, how many rounds of meiosis have the primary oocytes been through?
How many chromosomes do the primary oocytes have?
What does an oocyte undergo its 2nd round of meiotic division?
After fusion of the sperm and the egg occurs
Before the 23 chromosomes of the male gamete joins the 23 chromosomes of the female game within the nucleus of the cell
What are the 4 phases of meiosis?
What phase of meiosis are primary oocytes suspended in?
What is the sequence of follicular development?
1. Enlargement of ovum with aggregation of stromal cells to form thecal cells
2. When a dominant follicle is selected at day 6 of cycle, the inner layers of granulosa cells adhere to the ovum and form the corona radiata
What is the role of FSH?
Where does it bind to?
1. Stimulates follicular growth and development
2. Binds exclusively to granulosa cells in the growing follicle
What is the action of hormones in follicular development and ovulation?
-Stimulates follicular growth and development, binding exclusively to granulosa cells in the growing follicle
2. Granulosa cells produce oestrogen which feeds back on the pituitary to suppress FSH release, with only the dominant follicle then getting enough FSH to continue development. At the same time, FSH stimulates receptors for LH
3. LH stimulates the process of ovulation, the reactivation of meosis 1 and sustains development of corpus luteum
Where are receptors for FSH?
Granulosa cells in growing follicle
Where are receptors for LH?
On theca and granulosa cells and in the corpus luteum
What hormone initiates the hormonal events associated with ovulation?
Gonadotrophin-releasing hormone (GnRH) is produced by the hypothalamus
It results in the release of FSH and LH from the pituitary
Describe the hormonal events associated with ovulation regarding:
1. GnRH is released in episodic fluctuations
2. Levels of FSH are slightly higher during menses to stimulate development of the next follicles and subsequently decline due to negative feedback effect of oestrogen production by the dominant follicle
3. LH remains constant in the first half of the cycle but there is a marked surge of LH just before ovulation
4. LH and FSH levels are slightly lower in the 2nd half of the cycle than in pre-ovulatory phase, but continued LH release by the pituitary is necssary for normal corpus luteum function
5. Oestrogen production increases in the first half of the cycle, falls to about 60% of its follicular phase peak following ovulation and a 2nd peak occurs in luteal phase.
6. Progesterone levels are low prior to ovulation but are elevated throughout most of the luteal phase
What are the 4 phases of the endometrial cycle?
1. Menstrual phase
2. Phase of repair
3. Follicular or proliferative phase
4. Luteal or secretory phase
What are the 2 layers of the uterus?
1. Inner layer of endometrium
-made up of 3 layers
2. Outer myometrium
What are the 3 layers of the endometrium from out to in?
1. Zona basalis
2. Zona spongiosa
3. Zona compacta
Of the 3 zones of the endometrium, which ones are shed in menstruation?
The outer 2
What are the features of the menstrual phase of the endometrial cycle?
1. Occurs in the first 4 days
2. Shedding of the outer 2 layers of the endometrium
3. Associated with fall in both oestrogen and progesterone levels
What are the features of the phase of repair of the endometrial cycle?
1. Day 4-7
2. Formation of a new capillary bed arising from arterial coils and regeneration of epithelial surface
What are the features of the follicular or proliferative phase of the endometrial cycle?
1. Day 7-ovulation (day 14)
2. Period of maximal growth of endometrium and expansion of glands and stromal development
What are the features of the luteal or secretory phase of the endometrial cycle?
1. From ovulation and continues until 14 days later when menstruation starts again
2. Endometrial glands become convoluted and 'saw-toothed' in appearance
3. Epithelial cells secrete fluid which becomes thick by mid-luteal phase (around day 20 of a 28 day cycle)
4. As menstruation approaches, there is oedema of the stroma and a pseudodecidual reaction
Is the mucus in the endometrium more receptive to sperm during the follicular or luteal phase?
What is capacitation?
When sperm travel through the Fallopian tubes, the sperm undergo the final stage of maturation (capacitation), which are enzyme-induced, enabling penetration of the zona pellucida
Where in the fallopian tube do the sperm and egg meet?
What is the sequence of fertilsation and implantation?
1. Adherence of sperm and egg initiates the acrosome reaction, involving the loss of plasma membrane over the acrosomal cap. this allows the release of lytic enzymes which facilitates penetration of the oocyte membrane
2. The sperm head decondenses to form the male pronucleus and eventually becomes apposed to the female pronucleus in the female egg to form the zygote
3. 36 hours after fertilisation, the conceptus is transported through the tube by musclar peristaltic action
4. The zygote undergoes cleavage and at the 16-cell stage, it is a solid ball of cells known as a morula
5. A fluid-filled cavity develops in the morula to form the blastocyst
6. Six days after ovulation, the embryonic pole of the blastocyst attaches itself to the endometrium, near the mid-portion of the uterine cavity.
7. By the 7th day post-ovulatory day, the blastocyst has penetrated deeply into the endometrium
8. Decidual reaction of the endometrium occurs
What is the decidual reaction?
After implantation, the endometrial cells are destroyed by the cytotrophoblast and the cells are incorporated by fusion and phagocytosis into the trophoblast. The endometrial stromal cells become large and pale
Qs to ask in gynae history?
Menstruation - how long cycle is/how long they bleed for/when their period started/any intermenstrual or post-coital bleeding/heavy/LMP
Obstetric - been pregnant/had children/ectopics/miscarriages
Sexual - contraception/partners/STDs/when they were last checked
Smear - had it/up to date/ever had abnormal