Chapter B-2

 

 

FEMALE

REPRODUCTIVE SYSTEM

 

Reproduction is the production of offsprings. ‘Re’ is Latin word. It means ‘again’. Reproductive system is the system responsible for formation of progeny of sons and daughters and their proper brought up till they are capable to reproduce.

 

A sagittal section through female pelvis showing parts of female reproductive system

 

 

 

 

 

The female reproductive system consists of internal and external reproductive organs.

Internal reproductive organs are situated within lesser pelvis. They include:

1. Two ovaries, right and left.
2. Two uterine tubes, right and left.
3. One uterus
4. One vagina

 

Ovaries are the primary sex organs. Here the female gametes are formed.

Uterine tubes transport mature male and female gametes. These are sites where male and female gametes unite to form a fertilized ovum or zygote. Zygote is converted into morula and shifted to uterine cavity.

Uterus. Here morula is converted into blastocyst. It is the site of implantation of blastocyst. This blastocyst matures into fetus. The fetus grows and remains in uterus for nine months. 

Vagina is the organ of copulation. The fetus is also born through this canal.

 

The external reproductive organs are usually called external genitalia. They are antero-inferior to the pubic arch and they include the mons pubis, the labia majora, labia minora, clitoris, the bulb of the vestibule, the greater vestibular glands, and the vestibule itself.

 

Parts of female reproductive system

 

 

 

 

 

 

OVARY

 

Ovaries are paired almond-shaped structures situated one on each side of uterus close to the lateral pelvic wall. They are attached to the posterior aspect of broad ligament of uterus near its upper limit by a double fold of peritoneum, behind and below the lateral part of uterine tubes. This double fold of peritoneum is called mesovarium.

 

Ovaries, like testes, develop from genital ridge. In embryonic and early fetal life the ovaries are, like the testes, situated in the lumbar region near the kidneys, but they gradually descend into the lesser pelvis.

 

Ovaries are grayish-pink in the living. The surface is smooth before regular ovulation begins, but after the start of reproductive life surface of the ovaries become distorted by the scaring which follows the degeneration of successive corpora lutea.

 

Each ovary is about 3 cm long, 1.5 cm wide and 1 cm thick.

 

Ovarian position varies much in women who have borne children; the ovaries are displaced in the first pregnancy and usually never return to their original location.

 

My dear students we will now describe the ovary of a nulliparous woman (who has not yet borne children).

 

Each ovary occupies the ovarian fossa, on the lateral pelvic wall, bounded anteriorly by the obliterated umbilical artery and posteriorly by the ureter and internal iliac artery.

 

Attached to its upper, tubal extremity, are the ovarian fimbria of the uterine tube. The uterine (inferior) extremity is attached to the lateral angle of the uterus by a rounded ovarian ligament.

 

 

 

 

 

 

 

 

 

 

 

 

MICROSTRUCTURE OF THE OVARY

Ovarian surface epithelium

The covering of the ovary is composed mainly of cuboidal cells bearing microvilli, although there is also a scattered group of flattened epithelial cells with fewer microvilli, which may represent cells reacting to epithelial injury caused by ovulation. So before reproductive life the surface epithelium is simple cuboidal epithelium. As the reproductive life begins patches of simple squamous epithelium replace.

 

This gives the ovary a dull gray surface, contrasting with the shining, smooth peritoneum of the mesovarium. A white line around the anterior or mesovarian border usually marks the transition between peritoneum and ovarian epithelium.

 

 

The epithelium appears to take an active part in the repair of the ovarian surface after ovulation by reforming the epithelial rent and reconstituting the underlying matrix.

 

 

Microscopic picture of ovary. Stained with Hematoxyline and Eosin. X100. 

 

 

 

 

Surface epithelium is very delicate and easily damaged by manipulation. About 85% of ovarian cancers arise from neoplastic changes in the surface epithelium.

 

 

Tunica albuginea

Immediately beneath the epithelium, there is a tough collagenous coat called tunica albuginea.

 

 

The mass of the ovary is divisible into cortex and medulla. The medulla forms the central core and the cortex surrounds the medulla except at the hilum. The hilum is on the uterine extremity and is continuous with rounded ovarian ligament. The hilum receives the vessels and nerves.

 

Ovarian Cortex.

It is cellular connective tissue. It means loose connective tissue with abundant cells. It contains primordial follicles only before puberty. After puberty it contains the ovarian follicles of various sizes and corpora lutea and their degenerative remnants called albicans, depending on the stage of menstrual cycle or age. The follicles and their products are embedded in a dense fibrocellular stroma composed of interwoven, thin collagen fibers and many fusiform, fibroblast-like or mesenchymal cells arranged in characteristic swirls.

 

Medulla.

It is vascular connective tissue. It means loose connective tissue with lot off vessels. This central zone is highly vascular, consisting of numerous veins and spiral arteries set in a loose connective tissue stroma, with many elastin fibers, pericytes and some smooth muscle fibers. The vessels enter the hilum from the mesovarium. The medulla is much more vascular than the cortex.

The Postmenopausal ovary

With the change in hormonal state at the menopause (usually in 45-55 years), ovulation ceases and various microscopic changes ensue within the ovarian tissues. The stroma becomes denser, the tunica albuginea thickens and the ovarian surface epithelium thins out. However, many follicles persist within the cortex, some of them without oocytes, but others apparently normal, providing the possibility of ovulation if the hormonal changes were to be reversed. Some abnormal follicles may become cystic as age progresses. This is quite a common feature in later years.

 

 

 

 

Vessels

The ovaries and uterine tubes are supplied by the ovarian arteries, which are branches of the abdominal aorta.

The veins emerge from the ovarian hila as a pampiniform plexus, which form the ovarian veins. The right ovarian vein opens in inferior vena cava and left drains into left renal vein.

 

Lymph vessels drain primarily to the lumbo-aortic and pelvic lymph nodes, although it is reported that after the menopause the flow of lymph is reduced and it drains mainly to the lumbo-aortic nodes.

Nerves

The innervation, is derived from the ovarian plexuses. Postganglionic sympathetic, parasympathetic fibers and autonomic afferent fibers innervate ovaries. but little is known of their actual distribution or function, particularly in humans.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ovarian follicles

 

Primordial follicles.

At birth, the cortex contains a superficial zone of primordial follicles; these consist of primary oocytes (about 25 mm in diameter) surrounded by a single layer of flat follicular cells. Primary oocyte is in dictyotene phase. Many primordial follicles degenerate during childhood. Their remnants are visible as atretic follicles. After puberty, relatively small numbers of primordial follicles undergo a series of developmental changes. Only one follicle from either ovary comes to full maturity and releases its oocyte (ovulation) for transport into the uterine tube potentially for fertilization.

 

 

 

 

Primary follicle.

The primary oocyte surrounded by zona pellucida and a single layer of cuboidal cells is called primary follicle.

They are never present before puberty. After puberty in each menstrual cycle 5-12 primordial follicles start maturing. The primary oocyte (still in dictyotene phase) begins to increase in size, while the single continuous layer of flattened follicular cells surrounding it becomes the single continuous layer of cuboidal follicular cells.

The primary oocyte secretes a thick layer of deeply staining acellular homogeneous membrane of glycoproteins, between its surface and the surrounding follicular cells. This homogeneous membrane is called zona pellucida.

When the follicular cells have become cuboidal and the zona pellucida has formed the follicle is now known as primary follicle.

Also small finger-like processes of the follicular cells extend across the zona pellucida and interdigitate with the microvilli of the primary oocyte cell membrane. These processes are thought to be important for the transport of materials from the follicular cells to the oocyte.

 

 

 

 

 

 

Secondary follicle.

As the follicles continue to grow, the cuboidal follicular cells multiply and proliferate and form a stratified cuboidal epithelium resting on a basement membrane. The cells constituting the epithelium are now given the name granulosa cells. These cells are in functional contact with each other through gap junctions. Theca folliculi is forming around the developing follicle. The follicle is now known as secondary follicle.

 

 

 

Tertiary follicle.

A cavity or antrum develops in granulosa cells. 

The granulosa cells continue to proliferate and multiply. As the mass of cells continues to increase, spaces appear between them. These spaces are filled with clear fluid called liquor folliculi. The fluid contains hyaluran, growth factors and the hormonal secretions of the granulosa cells.

These spaces coalesce with one another and a crescent shaped cavity or antrum is formed in such a way that the primary oocyte, along with some granulosa cells, is pushed to one side. The follicle is now given the name tertiary follicle or vesicular follicle.

The follicle is now about 200 mm. With the passage of time the cavity enlarges. Theca folliculi is now clearly defined. It consists of an inner layer called theca interna and an outer layer called theca externa.

 

Granulose cells and theca cells produce estrogens.

 

 

 

 

 

Gra’afian follicle.

The fluid continues to increase and the follicle increases. The fully mature tertiary follicle is called Gra’afian follicle. The antrum is very large. At maturity, the follicle may be 10 mm or more in diameter.

Theca folliculi is well developed. It is composed of cells having characteristics of steroid secretion, rich in blood vessels, and the theca externa, which gradually merges with the ovarian stroma.

The primary oocyte and its surrounding granulosa cells form a bump in the antrum. This bump is known as cumulus oophorus or ovaricus.  Primary oocyte shows spindle formation of first meiotic division.

Gra’afian follicle forms a bump on the surface of the ovary.

 

The Gra’afian follicle, highly diagrammatic.

 

 

Atretic follicles.

Atresia (ah-tre’ze-ah) [a neg. + Gr. tresis a hold + -ia] congenital absence or closure of a normal body orifice or tubular organ.

 

Atretic (ah-tret’ik) [Gr. atretos not perforated] spacing without an opening; pertaining to or characterized by atresia.

 

 

 

 

 

 

 

 

Schematic diagram showing the development of follicles, ovulation and formation of corpus luteum and albicans.

 

 

Atresia occurs at all stages of follicles.

 

Primary oocytes and primordial follicles are maximum in number at 5 months gestation. They are nearly 7 million. They are reduced to about 2 million at birth. Postnatally, further degeneration occurs so that by puberty only about 40,000 oocytes remain.

 

Of the 40,000 oocytes remaining at puberty only about 400 become secondary oocytes and undergo ovulation during the reproductive years. The rest, after being activated to the primary follicle, degenerate before Gra’afian follicle at any stage as atretic follicles.

 

The first sign of atresia is the appearance of pyknotic nuclei in the granulose cell. The remnant of the follicle is invaded by blood vessels, macrophages and connective tissue, which ultimately replaces the follicle, converting it into a small white fibrous body.

 

 

STRUCTURE OF THE UTERUS

 

 

 

Regarding uterus and intrauterine life The Creator says in Qur’an that:

 

 

 

HE created you from a single person (Adam), then from that HE created his mate (wife Hawwa) and HE sent down for you eight pairs of cattle, male and female. HE shapes you in your mother’s wombs, giving you one form after the other, under three dark veils. This is ALLAH, your RAB: sovereignty is HIS: there is no ILAH but HE. Whence are you, then, being turned away?

 

Az-Zumar. Surah 39. Ayah 6. Para 23.

 

 

The embryo passes from one stage of development to another within three covers which have been expressed in Qur’an as three dark veils.

 

These may be:

1. Abdominal wall
2. Uterine wall
3. Placenta with its chorionic and amniotic membranes

 

 

 

 

 

 

 

 

 

 

 

The wall of the uterus also consists of three layers:

1. Perimetrium. It is the serosa of the uterus. It consists of a single layer of flattened cells with loose connective tissue.
2. Myometrium. A thick layer of smooth muscle cells, consisting of inner longitudinal layer (stratum subvascularae), middle circular layer (stratum vascularae) and outer longitudinal layer (stratum supravascularae).
3. Endometrium. It consists of simple columnar epithelium, lamina propria and glands.

 

During secretary phase of menstrual cycle, three layers of endometrium are distinguished.

1. A thin superficial compact layer consisting of densely packed, stromal cells around the straight necks of the glands;
2. A thick sponge layer composed of edematous stroma containing dilated tortuous bodies of the glands. The arteries are also highly tortuous here.
3. A thin basal layer containing the blind ends of the glands. This basal layer has its own blood supply also. This layer is not sloughed off during menstruation.

 

The compact and sponge layers, disintegrate and are shed off during menstruation and parturition (delivery of a baby), and so together they are commonly called functional layer.

 

Microscopic Picture of Endometrium in secretary phase.

 

 

Blood supply of the uterus:

The two uterine arteries run along the lateral border of uterus and give regularly branches, which enter the myometrium of the uterus. These branches reach the stratum vascularae of mymetrium. Here they anastomose and form a circular network of blood vessels throughout this stratum. This circular network of blood vessels now gives rise to vessels supplying supravascular and subvascular layers of myometrium.

 

This circular network also gives rise to two different sets of vessels supplying the endometrium.

 

One set consists of long spiral arteries and run through the whole thickness of endometrium. These arteries are under hormonal control. They are highly coiled in spongy layer and relatively straight in basal and compact layers. These supply all three layers of endometrium.

 

The other set consists of short straight arteries and supply basal layer of endometrium only. These arteries remain in basal layer and never go beyond the basal layer.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

UTERINE TUBES

Uterine tubes are also called Fallopian tubes. There are two uterine tubes, right and left, situated in the upper margins of the broad ligaments of the uterus. Each tube is 10 cm long. Its medial end opens into the superior angle of the uterine cavity. Its lateral end opens into the peritoneal cavity close to the ovary.

 

 

A sagittal section through female pelvis showing parts of female reproductive system

 

The uterine ostium or opening is very small, and admits only a fine bristle, the opening into the peritoneal cavity is named the abdominal ostium and when its muscular wall is relaxed has a diameter of about 3 mm.

 

The abdominal opening is situated at the bottom of the trumpet-shaped expansion of the uterine tube, the infundibulum, the circumference of which is prolonged by a varying number of irregular processes, called fimbriae, and therefore this extremity of the tube is also called fimbriated end. One fimbria is longer and more deeply grooved than the others. It is closely applied to the tubal extremity of the ovary and is named as ovarian fimbria.

 

 

 

 

The infundibulum leads to the ampullary part of the tube which is thin walled and tortuous and forms rather more than one-half of the tube. The ampulla is succeeded by the isthmus, which is rounded and cord like. The isthmus constitutes approximately the medial one-third of the tube. Then the uterine tube enters the wall of uterus, runs through it and opens at the superior angle of the cavity of the uterus. It is 1 cm long and is named the uterine part or intramural part of the uterine tube.

 

 

Parts of female reproductive system

 

Uterine tubes transmit ova from the ovaries to the cavity of the uterus. They are also the sites of fertilization, which occurs in the ampullary part. In the uterine tube, ova fertilized on non-fertilized, travel medially towards the uterus while sperms travel laterally from the uterus towards the infundibulum.