Female Reproductive System: Structure and Functions
Female Reproductive System: Structure and Functions
Female Reproductive System. The dynamic range of functions to the extreme. Extreme performance. By design.
For each woman, a high–performance female reproductive system’s architecture is critical to her life. Especially for ‘tasks’ (functions) like producing and secreting steroidal sex hormones (estrogen and progesterone); preconfiguring the menstrual cycle and powering up its phases: the follicular phase, the ovulatory phase (ovulation), and the luteal phase; proceeding the ova or oocytes (the gametes necessary for reproduction); transferring the oocytes to the site of Fertilization (Fertilization of the oocyte by a spermatozoon normally occurs in the fallopian tubes); transferring the Fertilized oocyte (a zygote) down the fallopian tube and into the uterus; if Fertilization and/or implantation doesn’t occur — the system is designed to shed the uterine lining on the monthly basis (menstruating).
If the conception ‘session’ and Embryo Implantation ‘session’ happened successfully, the female reproductive system’s functions are to complete embryo development through the fetal stage until birth and to give birth.
The dynamic range of functions of the Female Reproductive System involves:
producing and secreting steroidal sex hormones
preconfiguring the menstrual cycle and powering up its phases
proceeding the oocytes (powering the oogenesis process)
transferring the oocytes to the site of Fertilization (1–2 oocyte(s) will be sent down the fallopian tube attached to its ovary in anticipation of Fertilization)
transferring the fertilized oocyte (a zygote) down the fallopian tube and into the uterus if the Fertilization session was successful
if Embryo Generation and Embryo Implantation ‘session’ happened successfully — completing embryo development through the fetal stage until birth and giving the birth
if Fertilization and/or implantation doesn’t occur — shedding of the uterine lining on the monthly basis through menstruation
non–fertilized oocyte is flushed out of the system through menstruation too
The menstrual cycle phases’ sophisticated algorithm is designed for prep. the uterine lining layer (endometrium) for the possible pregnancy and vs: if the pregnancy is not achieved, the extra sophisticated algorithm is powered up for shedding of the uterine lining (on the monthly basis). In any way, the sophisticated algorithm ‘installed’ in the female reproductive system brings more specifications and options to the woman’s cycle than ever.
The multitasking mode of the female reproductive system features an astonishing internal structure. It includes paired Fallopian tubes (or uterine tubes), paired Ovaries, the Uterus, and the Vagina.
Fallopian Tubes (uterine tubes)
The fallopian tubes (uterine tubes or oviducts) are two (bilateral) muscular tubes featuring considerable mobility, each measuring about 100–120 mm in length (but can be a little bit shorter or larger) and 50–12 mm in diameter. It is extremely narrow, being less than 1 mm at its opening into the uterine cavity. Each fallopian tube has a funnel–shaped end, opening into the peritoneal cavity next to the ovary, and a fringe of fingerlike extensions (fimbriae). They function as the channels for the released Oocyte Transfer to the site of Fertilization, Fertilization, and zygote (fertilized oocyte) transfer into the uterine cavity.
Each uterine (fallopian) tube features the following ‘core configuration’:
the infundibulum, a funnel–shaped opening near the ovary to which fimbriae are attached. Fimbriae catch the released oocytes during each menstrual cycle. The endings of the fimbriae extend over the ovary contacting close to the ovary’s surface during the ovulation phase guiding the released free oocyte to the site of fertilization,
the ampulla (a round circular vessel that curves over the ovary), the longest and expanded area of the fallopian tube where fertilization normally occurs (the released oocyte is penetrated by the single spermatozoon),
the isthmus, a narrower region of the fallopian tube connecting the ampulla to the uterine cavity,
and the uterine part of the fallopian tube, which passes through the wall of the uterus and opens into the interior of this organ.
The major functions of the Fallopian Tubes are:
catching the oocyte after its release from the ovary’s antral follicle
guiding the oocyte to the site of Fertilization
producing the tubal fluid secretions containing nutrients for oocytes, spermatozoa, and zygotes (fertilized oocytes)
the fallopian tubes’ inner layer is responsible for transporting gametes (oocytes and spermatozoa), embryos, and tubal fluid secretions
transferring the fertilized oocyte (a zygote) down the fallopian tube and into the uterus
4 Amusing Facts about Your Fallopian Tubes
You can get pregnant if you have one functional Fallopian tube and at least one functioning ovary and your menses are regular.
Fallopian tubes are mobile and active tubes.
If one uterine tube is ‘broken’ (cannot function), the other healthy tube can migrate to pick up the released oocyte from the opposite ovary.
Even if you have the only Fallopian Tube left after the surgery, this uterine tube can move over to the opposite ovary and ‘pick up’ the released oocyte from the opposite ovary.
The Ovaries
Ovaries are almond–shaped (oval–shaped) bodies featuring the following average sizing specifications: approximately 30–40 mm long, 15–30 mm wide, and 10–15 mm thick. It is essential to note that asymmetry is common, the ovarian size can be different for the right and the left ovary, and the right ovary usually being larger than the left.
Each ovary is covered by a simple cuboidal epithelium, the surface (germinal) epithelium, continuous with the mesothelium, and overlying a layer of dense connective tissue capsule. The most internal part of the ovary is the medulla, which contains loose connective tissue and blood vessels. There are no sharp limits between the ovarian cortical and medullary regions, but it should be noted that the ‘envisaged borders’ of the cortical regions are indicated by the ovarian follicles ‘launched’ inside it.
Most of the ovary consists of the cortex and many ovarian follicles located inside it. Ovarian follicles are preconfigured for holding the immature oocytes. Ovarian follicles are tiny sacs filled with follicular fluid designed for completing oocyte development. Each immature oocyte has its own ovarian follicle. The oocyte will eventually break free from the ovarian follicle and travel down the fallopian tube reaching the site of fertilization and continuing post–fertilization travelling through the fallopian tube reaching the uterus. Non–fertilized oocytes will follow the same way, but instead of implanting inside the uterus, they will be flushed out of the system through menstruation with the uterine lining.
A normal ovary consists of 8–10 follicles featuring different sizes: 2–30 mm (sometimes 32–36 mm). The antral follicles can be represented as follicular cohorts with further division by size criterion (in 5 cohorts): antral follicles’ cohort I < 5 mm (2–4 mm); antral follicles’ cohort II < 11 mm (5–10 mm); antral follicles’ cohort III < 20 mm (11–19 mm); antral follicles’ cohort IV <30 mm (20–29 mm); and antral follicles’ cohort V > 30 mm (30–36 mm).
The cohort of small follicles (with less than 18 mm in size) are called small antral follicles. The cohort of bigger follicles (18–30 mm in size) is called dominant antral follicles. A dominant ovarian follicle refers to the follicle that enlarges to release an oocyte during a menstrual cycle. Sometimes there can be two or more dominant follicles, and this number varies every month.
Very small antral follicles show a significant number of poor–quality oocytes and vs: the medium–sized antral follicles show better–quality oocytes, and the dominant follicles show the top–quality ones.
As the follicles grow with increasing oocyte size and numbers of granulosa cells surrounding the oocyte, they move deeper into the ovarian cortex. Small spaces develop within the granulosa layer as the follicular cells secrete follicular fluid. This fluid surrounds the oocytes inside their follicular sacs (antral follicles).
Ovaries are packed with configurations that allow the female reproductive system to run a greater range of functions like producing estrogen and progesterone, producing and hosting the immature oocytes, powering up and completing the oogenesis, and releasing the one (sometimes two) mature oocyte ready for fertilization each cycle (natural cycle).
Each ovary features the following ‘core configuration’:
the ovarian surface epithelium is formed by the layer of simple cuboidal epithelium featuring the underlying dense connective tissue capsule
ovarian cortex is formed by a connective tissue stroma and numerous ovarian follicles. Inside each follicle, there is an oocyte, surrounded by a single layer of follicular cells
ovarian medulla is the innermost layer of the ovary. It is formed by loose connective tissue and a rich neurovascular network.
The major functions of the Ovaries are:
producing and secreting the sex steroid hormones (estrogen and progesterone)
producing and hosting the immature oocytes
powering up and completing the oocyte maturation event each cycle (completing the oogenesis)
releasing the mature oocyte(s) (oocyte release event is called ovulation)
13 Stunning Facts about Your Ovaries
The fetal gender reveal won’t happen until you are 14 weeks pregnant, but gender identification happens..., yay, several moments after the conception (the oocyte has an X sex–chromosome while the sperm cells contain an X or Y sex–chromosome. If the X–sex–chromosome–carrying spermatozoon fertilizes the oocyte — the zygote will be labeled as female (XX) and vs. If the Y–sex–chromosome–carrying spermatozoon fertilizes the oocyte — the zygote will be labeled as male (XY), and you will have the dude.
Being just a one–month female embryo, she is starting to ‘build and code’ her reproductive system. In the first month of embryonic life, a small population of primordial germ cells migrates from the yolk sac to the gonadal primordia. In the gonads these cells divide extensively and rapidly, differentiating as oogonia.
In developing ovaries of a two–month embryo there are approximately... 600,000 oogonia which produce more than 6,000,000–7,000,000 six– (seven million) by the 5th month!
Ovaries’ generation event happens when your female fetus is only 11–12 gestational weeks old! From this timeline, there are more than 4 million oocytes in her ovaries, and this number is growing till the 20th gestational week! Tiny ovaries have so powerful ovarian reserve!
Starting from the 3rd month of fetal development (12th gestational week), the oogonia begin to enter the prophase of the first meiotic division but arrest after completing synapsis and recombination. The generated cells (arrested in meiosis) are called primary oocytes. Each primary oocyte has its own tiny sac (it is inside this sac, surrounded by flattened supportive cells called follicular cells) called the ovarian follicle.
Starting from gestational week 13, the fetal ovarian reserve is growing and growing, and being just 20 gestational weeks old, your tiny bundle of joy has more than 6,000,000 (6 million oocytes) in her tiny ovaries!
The fetal ovarian reserve will be decreasing starting from the 20th gestational week… And most of her oocytes will disappear before your girl is born.
When your newborn Bundle is born, only 2,000,000 (2 million) oocytes will be her tiny ovaries, the rest will just disappear.
By puberty, the ovarian reserve will decrease to 1,000,000 (1 million) oocytes...
Starting from the 1st menstrual cycle, your girl will lose not just 1 oocyte, but in total nearly 1,000...
Only about 400–500 mature oocytes go through ovulation (just imagine from 6,000,000–7,000.000 (six–seven million))!
It is impossible to predict when ovaries will kick off menopause, thus, it can be a shocking experience.
Ovaries are changing their shape and size over time.
Uterus
The normal uterus is a pear–shaped (upside–down pear) thick–walled mobile muscular organ capable of expansion while hosting a growing fetus. The normal non–pregnant uterus measures approximately 70–90 mm long, 45–60 mm wide, and 25–35 mm thick. It weighs approximately 30–60 grams (depending on its size). Pregnant uterus dramatically increases in size... 1,000 times, and features an advanced uteroplacental multitasking placental network, the adaptable and adjustive configurations preconfigured for each stage of the pregnancy, and much more sophisticated algorithms powered up for hosting the fetus (fetuses). Estrogens manage pregnancy by stimulating uterine growth and increasing uteroplacental blood flow making the uterus an ideal and safe ‘space’ for fetal development.
The largest part of the uterus is called the body. It is entered by the left and right uterine tubes and the curved, superior area between the tubes is called the fundus. The uterus narrows in the isthmus and ends in the cervix.
The Uterus features the following structure:
The fundus is the top of the uterus.
The body is the main part of the uterus, and it includes the uterine cavity.
The cervix is the lower, narrow part of the uterus. The normal cervix in non–pregnant women is approximately 40–50 mm long, approximately half of which extends into the vaginal canal
The Uterine wall features the following ‘core configuration’:
an outer uterine connective tissue layer is called the perimetrium. It is largely covered by mesothelium
the middle thick tunic of highly vascular smooth muscle uterine layer is known as myometrium (most of the uterine wall is composed of the myometrium)
the inner layer of the uterus a smooth and closely adherent to the subjacent tissue mucous membrane known as the endometrium (the inner layer of the uterus). The endometrium is a functional intrauterine layer that transforms histologically and functionally adjusting itself to estrogen levels. During each menstrual cycle, the endometrium grows to a thick, blood vessel–rich, glandular tissue layer prep. for a potential pregnancy with an embryo implantation event. If the pregnancy is not achieved, the shedding of the uterine lining through menstruation is powered up.
The major functions of the Uterus are:
directing the blood flow to the pelvis (the networks of nerves and blood vessels of the uterus direct the blood flow to the pelvis)
producing uterine secretions
passing the male sperm through to the fallopian tubes (fertilization site)
nurturing the blastocyst (fertilized oocyte, Day 5) if it successfully implants into the endometrial lining
generating placenta
hosts the developing embryo and fetus until the birth
4 Stunning Facts about Your Uterus
Your Uterus is Ultra–flexible, strong, and elastic. It expands to more than 1,000 times its original size when pregnant. And after the pregnancy, it takes around 6 weeks to contract back to the original size (70–90 mm long, 45–60 mm wide, and 25–35 mm thick) and weight (30–60 grams).
Some women have more than one uterus... Some women have two uteruses!
Some women are born without uterus... They have functional fallopian tubes and ovaries, powering up ovulation, but they don’t have menstruation.
Your Uterus generates placenta when you get pregnant!
Something to say in conclusion?
The female reproductive system is amazing. Sophisticated algorithms. Extreme performance. Power plus power. By design. Multitasking mode. Ideal synchronization of each ‘configuration’.