Reproductive L2 Flashcards
How many oocytes are released in woman’s lifetime?
~400
How many oocytes are released in woman’s lifetime?
~400
how is uterus connected to the ovary?
fallopian tube/ oviduct
What is the position of the uterus in respect to vagina?
90 degrees ( anteflexed uterus)- normal
retroflexed uterus
~20 % of women have it
can cause pain during menstruation
Vagina
-elastic muscular tube 7.5-9 cm extending from the cervix to the exterior of the body
what are the 3 main functions of the vagina?
- Through menstruation the endometrium comes off. Serves as a passageway for the elimination of menstrual fluid
- it receives the penis during sexual intercourse, and holds spermatozoa before they pass into the uterus
- Forms the lower portion of the birth canal through which the fetus passes during delivery
what are the 3 main functions of the vagina?
- Through menstruation the endometrium comes off. Serves as a passageway for the elimination of menstrual fluid
- it receives the penis during sexual intercourse, and holds spermatozoa before they pass into the uterus
- Forms the lower portion of the birth canal through which the fetus passes during delivery
Uterus structure
Fundus at the top, at the bottom-cervix. A plug of mucus blocks the entry of the sperm into the uterus. Cervix holds the baby in the uterus to avoid premature release into the vagina
uterus functions
-a pathway for sperm transport
-provides mechanical protection, nutritional support, and waste removal for the developing embryo and fetus. (through the placenta)
endometrium provides the optimal environment for embryo implantation
-Contractions in the muscular wall (myometrium) of the uterus are important in ejecting the fetus at the time of birth.
-Source of menstrual fluid
What is the name of the layer lost during menstruation?
stratum functionalis of endometrium
2 layers of the endometrium
Inner functional zone: stratum functionalis. Contains most of the uterine glands
Outer basilar zone: stratum basalis, adjacent to the myometrium. The basilar zone attaches the endometrium to the myometrium.
The uterine(fallopian) tubes
~ diameter of a drinking straw
-provides a rich, nutritive environment containing lipids and glycogen for spermatozoa, oocytes, and developing embryo
Sperm go up the uterine tube (by cilia and sperm tail).
The oocyte is picked up by Fimbriae( projections at the end of uterine tube-infundibulum). Cilia on fimbriae. The oocyte is then carried through the uterine tube.
The uterine tube is covered in cilia. Provide the ability to oocytes to move down. More cilia at the infundibulum end than closer to the uterus. Non-ciliated secretory cells provide nutrients to keep oocytes and sperm alive.
The uterine tube has concentric layers of smooth muscle. Peristaltic contractions allow movement of the oocyte.
What is the optimal place for fetilization to occur?
Ampulla of the uterine wall
Ectopic(tubal) pregnancy
embryo implanted into the uterine tube
what are the risk factors for ectopic pregnancy?
Smoking, advanced maternal age and prior tubal damage are risk factors
What is the weight of ovaries?
5-10 g
3 layers/regions of the ovary
Outer ovarian cortex- containing the ovarian
follicles
Central ovarian medulla- consisting of ovarian stroma
and steroid-producing cells
Inner hilum (hilus) which acts as a point of entry for nerves and blood vessels
Primordial follicle
oocytes with some cells around it(granulosa cells, squamous)
Sit in ‘nests’
Most stay in this form in the ovaries. Dormant for a long time
Primary follicles
As the follicles grow, they are called primary or
pre-antral follicles. Immature primary follicles consist of
only one layer of granulosa cells.
Squamous cells -> cuboidal.
Become mitotically active, hormonal activity
The oocyte secretes glycoproteins, which form a translucent
acellular layer (zona pellucida).
Condensation of ovarian stromal cells, known as
thecal cells, begin to form around the follicle.
Zona pellucida
secreted by oocytes.
Allows entry of 1 sperm only
What is the importance of thecal cells?
Created from stroma cells
together with granulosa cells produce reproductive hormones
Follicle development
In response to FSH once a month, some follicles grow larger( primarily the number of granulosa cells surrounding the oocyte)
Secondary follicle
granulosa cells start producing a viscous fluid, which coalesces to form a single follicular antrum. It provides nutrients to the developing oocyte.
It is now referred to as an antral follicle.
The innermost layer of granulosa cells becomes firmly attached to the zona pellucida and is called the corona radiate
Mass of loosely associated granulosa cells is known as the cumulus oophorus
The theca develops to become the inner
glandular, highly vascular theca interna,
and the surrounding fibrous capsule, the theca externa
Mature (Graafian or pre-ovulatory) follicle
As the follicular antrum grows, the oocyte
becomes suspended in fluid. It is connected to
the rim of peripheral granulosa cells by a thin
stalk of cells.
What happens to the follicle during ovulation?
The increasing size of the follicle and its position in the
cortex of the ovarian stroma causes it to bulge out from the
ovarian surface.
The follicle ruptures, carrying with it the oocyte
and its surrounding mass of cumulus cells.
The oocyte is collected by cilia on the fimbria, which
sweep the cumulus mass into the uterine tube.
Corpus Luteum formation
The antrum breaks down, the basement membrane between the granulosa and thecal layers breaks down, and blood vessels invade.
The granulosa cells form large lutein (yellow pigment) cells (Corpus luteum =yellow body)
This transformation is referred to as luteinisation and is associated with increased secretion of progestagens-progesterone after ovulation.
Corpus Albicans
Corpus Luteum disintegrates
The whitish scar tissue remaining, the corpus Albicans (white body), is
absorbed back into the stromal tissue of the ovary over weeks to
months.
If fertilization does not occur, then the cycle starts all over again.
The process of fertilization
If the oocyte is fertilized and begins to divide, the corpus
luteum persists past its normal 2 week life span.
It is rescued from degeneration by human chorionic
gonadotropin (hCG). The hormone is produced by the
chorion of the embryo beginning about 8 days after
fertilisation.
The presence of hCG in maternal blood or urine is an
indicator of pregnancy and is the hormone detected by
home pregnancy tests
what is the function of Corpus Luteum?
produces progesterone, allowing the endometrium layer to stay stable and ready to support embryo implantation.
Usually lasts for 2 weeks, if no hCG-> Corpus Luteum degrade-> endometrium sheds
If hCG is present-> corpus luteum is maintained for longer to prolong endometrium
How long does an avergae menstrual cycle last?
28 days
Phases of menstrual cycle
Two phases in the ovarian cycle: follicular phase (day 1 to ovulation) and luteal phase (ovulation to menstruation)
Three phases in the uterine/menstrual cycle: menstruation, proliferative and secretory
The length of what phase in the menstrual cycle varies between women?
follicular phase
What happens to the follicular phase as the woman gets older?
it shortens
Main events of the menstrual cycle
1.After no fertilization has occurred there is a degression in progesterone and estrogen
2.Small rise in FSH-> increased activity of primary and secondary follicles. This leads to increased growth in the follicles
3. By day 6-7 dominant follicle( large amounts of granulosa cells). High production of estrogen.
4. Oestradiol suppress FSH (and LH) production in the
pituitary. This stops the production of more follicles and limits the number of follicles to one
5.Oestrogen levels
rise, by ~day 12, a threshold concentration of
oestradiol is exceeded. If this is maintained for ~36
hours, there is a temporary switch from a negative to positive feedback
6. Oestrogen mediated positive
feedback triggers a rise in GnRH leading
to an LH surge
7. LH surge induces ovulation
8. Corpus luteum develops, see
increased progesterone
9. Elevated progesterone levels inhibit GnRH, lead
to decreased FSH and LH
10. Demise of the corpus luteum
