Flashcards in Prefertilization Events - HY Deck (57):
What are the gametes and what is their origin, and where do they migrate?
1. Descendants of primordial germ cells.
2. Originate in the wall of the yolk sac of the embryo.
3. Migrate into the gonad region.
What processes are involved in the production of gametes?
Either oogenesis or spermatogenesis --> Involve meiosis.
What are the 2 cell divisions of meiosis?
Meiosis I and II --> Formation of gametes containing 23 chromosomes and 1N amount of DNA (23, 1N).
During meiosis I or meiosis II does crossover between the maternal and paternal chromosome occur?
During meiosis I.
In female gametogenesis, when do primordial germ cells (46, 2N) from the wall of the yolk sac, arrive in the ovary?
Week 6 of embryonic development.
To what do these primordial germ cells (46, 2N) differentiate, when they arrive in the ovary? (female gametogenesis)
Oogonia (46, 2N).
What process do oogonia undergo subsequently?
Enter meiosis I and undergo DNA replication to form primary oocytes (46, 4N).
During what month of the fetal life are primary oocytes formed?
By the 5th month of fetal life.
Until what period remain the primary oocytes dormant?
In prophase (dictyotene stage) of meiosis I UNTIL PUBERTY.
What happens during a woman's ovarian cycle regarding a primary oocyte?
Complete meiosis I to form a secondary oocyte (23, 2N) and a 1st polar body --> which probably degenerates.
What is the fate of the secondary oocyte?
Enters meiosis II --> ovulation occurs when the chromosomes align at metaphase.
Until when does the secondary oocyte remain arrested in metaphase of meiosis II?
Until fertilization occurs.
What happens during fertilization regarding the secondary oocyte?
Completes meiosis II to form a mature oocyte (23, 1N) and a second polar body.
What is the effect of FSH on female reproductive cycle?
Stimulates the development of a secondary follicle to a Graafian follicle within the ovary.
What do the granulosa cells of the secondary and Graafian follicle secrete?
What is the effect of estrogen to the endometrium of the uterus?
To enter PROLIFERATIVE phase.
What is the effect of LH?
Following ovulation, what do granulosa lutein cells of the corpus luteum produce?
What is the effect of progesterone on the endometrium of the uterus?
To enter the SECRETORY phase.
What happens during day 1-4 of the menstrual cycle?
Characterized by necrosis and shedding of the functional layer of the endometrium --> MENSTRUAL PHASE.
What happens during day 4-15 of the menstrual cycle?
Regeneration of the functional layer of the endometrium and a LOW basal body temperature --> PROLIFERATIVE PHASE.
What happens during day 14-16 of the menstrual cycle?
Ovulation of a secondary oocyte and coincides with the LH surge --> OVULATORY phase.
What happens during day 15-25?
Secretory activity of the endometrial glands and an ELEVATED basal body temperature - Implantation of the conceptus occurs during this phase --> SECRETORY PHASE.
What happens during day 25-28?
Ischemia due to reduced blood flow to the endometrium --> Premenstrual phase.
What are the 3 phases of male gametogenesis?
What is the fate of the primordial germ cells (46, 2N) during spermatogenesis?
1. Origin from the wall of the yolk sac.
2. Arrive in the testes at week 6.
3. Remain dormant until puberty.
What happens in puberty regarding the primordial germ cells (male gametogenesis)?
Differentiate into type A spermatogonia (46, 2N).
What happens during spermatocytogenesis?
Type A spermatogonia undergo mitosis to provide a continuous supply of stem cells throughout the reproductive life of the male.
What happens to some type A spermatogonia?
Differentiate into type B spermatogonia.
What is the fate of type B spermatogonia?
Enter meiosis I and undergo DNA replication to form PRIMARY SPERMATOCYTES (46, 4N).
What is the fate of primary spermatocytes?
Complete meiosis I to form 2 secondary spermatocytes (23, 2N).
What is the fate of secondary spermatocytes?
Complete meiosis II to form 4 spermatids (23, 1N).
What happens during spermiogenesis?
Spermatids undergo a POSTMEIOTIC series of morphological changes to form SPERM (23, 1N).
What process must the newly ejaculated sperm undergo in order to be fertile?
Where does capacitation take place?
In the female reproductive tract.
What does capacitation involve?
The unmasking of sperm glycosyltransferases and removal of proteins coating the surface of the sperm.
What may be the reason for the high incidence of chromosomal abnormalities in offspring of older women?
Prolonged dormancy of primary oocytes.
What is the primary cause of Down syndrome?
Maternal meiotic nondisjunction.
Mention some clinical findings of Down syndrome?
1. Severe mental retardation
2. Epicanthal folds
3. Brushfield spots
4. Simian creases
5. Decrease in AFP
What conditions are associated with increased age of the MAN?
What is the range for a physiologic sperm count?
20-100 million/mL of semen.
What percentage of sperm may be grossly deformed (2 heads, or 2 tails)?
Normally up to 10%.
Can the grossly abnormal sperm fertilize?
No, due to lack of motility.
What happens in hypogonadotrophic hypogonadism?
A condition where the hypothalamus produces reduced levels of GnRF leading to reduced levels of FSH/LH --> reduced levels of testosterone.
What happens in Kallmann syndrome?
A genetic disorder characterized by hypogonadotropic hypogonadism + anosmia.
Mention some drugs that may result in male infertility?
1. Cancer chemo
2. Anabolic steroids
3. Cimetidine (H2 blocker)
7. Nitrofurantoin (antibiotic used to treat UTI)
Mention other conditions that may result in male infertility?
10. Ductus deferens obstruction
Give a definition of anovulation.
Absence of ovulation in some women due to inadequate secretion of FSH and LH.
With what is anovulation usually treated?
With clomiphene citrate.
What is the action of clomiphene citrate?
Competes with estrogen for binding sites in the adenohypophysis --> Suppressing the normal negative feedback loop of estrogen on the adenohypophysis --> Stimulates FSH and LH secretion and induces ovulation.
What happens in primary ovarian insufficiency (premature ovarian failure)?
Loss of function of the ovaries before age 40 --> resulting in infertility.
What is the etiology of premature ovarian failure (primary ovarian insufficiency)?
Generally idiopathic, but also:
2. Fragile X syndrome
What is the age of onset of premature ovarian failure (primary ovarian insufficiency)?
Can be seen in early teenage years, but varies widely.
How is it called if a girl never begins menstruation?
Primary ovarian failure.
What are the clinical findings of primary ovarian failure?
2. Low estrogen levels
3. High FSH levels
4. Ultrasound may show small ovaries without follicles
To what is PID referred?
To infection of the uterus, uterine tubes, and/or ovaries leading to inflammation and scar formation.