Lecture 15: Reproduction in females Flashcards
Describe the vagina structure and function
This is the muscular 7.5-9 cm long tube that extends from the cervix to the exterior of the body.
It has 3 main functions: receives the penis, holds spermatozoa before they pass into the uterus and forms the lower portion of the birth canal
Describe the Uterus function
Function is to provide mechanical protection, nutritional support and waste removal for the developing fetus.
Describe the layers of ‘metrium’ in the uterus
Outermost layer is the stratum functionalis which contains the uterine glands and is lost throughout menstruation. Then the stratum basalis which stays constant and is attached to the myometrium. Myometrium is a smooth muscle wall thats contractions help expel the fetus.
Describe the Fallopian (uterine) tubes structure (basic)
The tube is lined by epithelium made up of cilliated and non cilliated secretory columnar cells. The mucosa is surrounded by concentric layers of smooth muscle.
Describe the Fallopian (uterine) tubes function
Function: transport of spermatozoa, oocyte and embryo by cillary movement and peristaltic contractions. As well as having lipids and glycogen for a nutritive environment.
Describe the Ovaries structure and function
Oval organ about 5-10g comprising of 3 regions.
Outer ovarian cortex containing all ovarian follicles, the central ovarian medulla (which contains ovarian stroma and steroid producing cells) and the inner hilum which allows blood vessels and nerves to enter.
What is ovarian stroma
A dense irregular connective tissue
What does an anteflexion or retroflexion mean
Most women have an anteflexed uterus which is perpendicular to the vagina but 20% have a retroflexed uterus which is kind of straight, following the vaginal tube
Describe the structure of the Uterus
Pear shaped organ 30-40g. The top part is called the Fundus and the bottom is called the Cervix.
What is the function of cervical mucus
Most of the time cervical mucus becomes thick plugging the cervix so no bacteria or sperm can enter the uterus from the vagina. Only a few days prior to ovulation does the mucus change to allow the entry of sperm
How was fetal growth predicted in the old days
The height of the fundus from the pubic bone was used to predict the number of weeks a fetus had gestated. With 1cm = 1 week. It could be also used to check for twins, gestational diabetes, wrong position, intrauterine growth restriction
Describe the 4 kind of regions of the fallopian tube
Closest to the uterus is the Isthmus.
Middle where fertilisation occurs: Ampulla
End Closest to the ovary :infundibulum.
Fingerlike projections at end : fimbriae. These are covered in cillia that are beating constantly and increase frequency to collect the oocyte when ovulated.
Define ectopic pregnancy
When fertilised embryo is implanted in any tissue other than uterine wall
List the 5 steps of follicular development in order and the two possible outcomes
Primordial follicle, primary follicle, secondary follicle, Mature (Graafian/pre-ovulatory follicle)
Ovulation, Corpus Luteum (luteinisation)
OUtcomes:
Fertilisation & futile
Describe the primordial follicle stage
The ovaries are filled with millions of primordial follicles from birth. These are oocytes surrounded by a single layer of squamous follicular cells.
Describe the Primary- Pre antral follicle stage
Some follicles grow and others die. The ones that start to grow, follicular cells become one layer of cuboidal granulosa cells
- FSH stimulates the oocyte to get bigger and then get more layers of granulosa cells.
- Oocyte secretes glycoproteins which form a translucent layer called the Zona pellucida.
- Ovarian stroma cells called Thecal cells begin to form around the follicle
Describe the main events at the Secondary follicle stage
As granulosa cells proliferate, they produce a viscous follicular fluid that coalesces to form a single follicular antrum (lake).
- Granulosa cells specialise
- Theca develops into 2 layers
What happens to the granulosa cells at secondary follicle stage
The corona radiata is made from the inner most 2-3 layers of granulosa cells becomes firmly attached to the zona pellucida.
The rest of the loosely associated granulosa cells are called cumulus oophorus
What does the theca develop to at the secondary follicle stage
The thecal cells move from the medulla to form the inner glandular and highly vascularised theca interna ( involved with the increased production of estradiol) and the fibrous outer capsule called theca externa
Descrube main events in the mature (Graafian or preovulatory) follicle stage
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
Descrube main events in the ovulation stage
The follicle starts to bulge out the ovarian surface bc it gets larger and its at the cortex of the ovarian stroma.
- The follicle then ruptures and this slowly releases the oocyte+ surrounding mass of cumulus cells.
- The oocyte is collected by cillia on the fimbria which sweep the cumulus mass into the uterine tube
Descrube main events in the Corpus luteum (luteinisation) stage of the ovary
After ovulation, the antrum breaks down and the basement membrane between the granulosa and thecal layers breaks down and blood vessels invade.
2. The granulosa cells form lutein (yellow) cells, this is associated with increasing secretion of progestagens
Describe what happens to corpus luteum in a futile cycle
Corpus luteum will only stay for 2 weeks. After which no fertilisation will lead to degeneration, forming the corpus albicans which is absorbed back into the stromal tissue of the ovary over weeks to months.
Describe what happens to corpus luteum in a fertile cycle
The corpus luteum will persist if the zygote survives and divides. hCG produced by chorion of the embryo 8days after fertilisation stops deterioration of the corpus luteum. This allows it to keep producing progesterone + estrogen to support pregnancy
What is the difference between a futile cycle and fertile cycle
Futile will lead to corpus luteum degenerating and therefore no more progesterones to prepare stable secretory endometrium for implantation as in a fertile cycle. Instead it is shed in menstruation.
Name and compare the phases of the ovarian cycle vs the endometrial cycle
The ovarian cycle has 2 phases, follicular phase (day 1 to ovulation) and luteal phase (ovulation to menstruation).
In contrast, the uterine menstrual cycle has 3 phases: Menstruation (0-5) proliferative in response to estradiol and secretory in response to progestrone
what cells produce what estrogens in the ovaries
The granulosa cells around the chosen oocyte. This is estradiol
What is the fixed phase of the menstrual cycle - how long and therefore how can menstrual cycle length vary
luteal phase is a fixed 14 days, however as a women ages the length of the follicular phase changes
Why does a human need a menstrual
The female reproductive tract has 2 main functions. To produce oocyte and reproductive hormones. And as well to incubate embryo
What is the first 2 key events of menstrual cycle ( starting at just before the menstrual bleed)
- The corpus luteum regresses with oestrogen and progesterone levels low. There is a slight increase of FSH
- FSH stimulation leads to increase follicular growth
What is the #3,4 key events of menstrual cycle ( starting at day 6/7)
- The dominant follicle has been selected. it has lots of thecal and granulosa cells that produce a rise in oestradiol
- Oestradiol suppress FSH and LH production in the pituitary
The levels of Progesterone and oestrogens increase and decrease oppositely to which two other hormones
FSH and LH
What is the #5,6,7 key events of menstrual cycle ( starting at around day 12)
- Oestrogen levels by the nearly mature follicle rise by ~day 12, a theshold concentration of oestradiol is exceeded. If this is maintained for around 3 days, there is a temporary switch from a negative to positive feedback.
- Oestrogen mediated positive feedback triggers a rise in GnRH, leading to a surge in LH
- The rapid rise of LH induces ovulation- release of the oocyte
What does the positive feedback switch caused by oestrodial mean
Instead of oestrodial increasing causing a decrease in GnRH and LH/ FSH, instead it helps to stimulate both the hypothalamus and anterior pituitary to produce MORE GnRH and LH/FSH
What is the #8,9,10 key events of menstrual cycle (starting at around day 17)
- Corpus Luteum develops and this increases progesterone.
- Elevated progesterone levels inhibit GnRH, leads to decreased FSH + LH as it reinstates the negative feedback loop
- The Corpus luteum demises and therefore progesterones start to decrease
