Female Reproductive System (Uterus/Ovaries) Functions

Female Reproductive System (Uterus/Ovaries)

Functions of the Female Reproductive System

The female reproductive system is an integral part of the human body. This is since it contains features that are important for the continuity of the human race.The female reproductive system comprises of the Ovaries, the uterus, the fallopian tubes and the vagina. The ovaries are a pair of endocrine glands that secrete eggs, or ova and produce endocrine hormones oestrogen and progesterone. A woman is born with about 60000 ova but only about 400 reach maturation. The ova are produced monthly in readiness and anticipation for fertilization in a process that is known as the menstrual cycle (Eaton,1976).

The uterus is the fibro-muscular organ that houses and nourishes the developing embryo during pregnancy. It also expels the foetus via forceful and rapid contracmtions during the process of childbirth.

The fallopian tubes are the site of fertilization. The tube is funnel shaped with one end divided into fingery projections that are known as fimbriae. These lie closest to the ovary..These projections beat in a synchronous manner and they force the ovum down into the uterus. The lining of the tube including its secretions nourish both the sperms and the ova.

The vagina is the passage that connects the uterus with the external genitals. It is about two and a half inches long with numerous blood vessels in its walls. These walls become erect when a woman is aroused. It has three cardinal functions. Its acts as the outlet of blood during menstruation as the passageway of the baby during birth and as the receptor of the male penis during coitus.

The vulva is the most external organ and it's comprised of the clitoris the labia majora and the labia minora. The clitoris is a small and sensitive organ that is aroused and becomes erect during sexual intercourse.

The other organs of the reproductive system are the mammary glands. They are designed to produce milk after pregnancy that acts as food for the nourishment of the neonate. They are composed of fifteen to twenty lobes that include the alveolar and the mammary ducts. The lead to the nipple that open to the outside. The nipples are also sensitive and may be aroused during the sexual act

THE UTERUS

Appearance

The uterus is a fibro muscular organ that is divided into an upper corpus or the uterine body and the lower cervix. In the normal state the uterus is flattened antero-posteriorly and is pear or pyriform shaped with the apex or the tip of the pear directed downwards and backwards. In dimensions the uterus measures 7.5cm in length, 5cm in width at its widest part and has a thickness of 2.5cm. Its weight is 30-40gms. Anatomically the uterus has been divided into two portions. The corpus uteri or Body and the Cervix Uteri or the Cervix. Midway between these two portions is the isthmus. The corpus uteri narrows downwards from the fundus to the isthmus. The fundus is that portion of the uterus that lies above the entry points of the fallopian tubes. It's covered by peritoneum that is continuous with that of the bladder and the intestines. The corpus ureteri is further divided into an anterior surface or vesicle surface, a posterior or intestinal surface and lateral margins. The anterior surface or facies vesicalis is flattened and covered by peritoneum that is reflected onto the bladder and form the vesicouterine pouch. The posterior surface is convex in outline and is covered in peritoneum that is continuous with the cervix and vagina. The lateral margins are penetrated at their upper portions by the fallopian tubes. Below the point of entry of the fallopian tubes the round ligament is attached while behind is the attachment of the ligament of the ovary. The fold of peritoneum that covers these three structures is the broad ligament. The cervix ureteri is conical in shape and is directed downwards and backwards. It is wider at its middle portion than it is both above and below. Its projects into the vagina dividing it into a supravaginal and vaginal portions.

Location

The uterus is located within the pelvis and lies between the bladder and the sigmoid colon and rectum behind. On its upper portions it's suspended by both the broad and round ligaments the uterus is composed of three layers a mucous layer, a muscular layer and a serous layer. The serous layer is the external layer and it is known as tunica serosa. Its origin is the peritoneum and it covers the fundus and the posterior surface of the uterus. It covers the anterior surface upto the junction of the body and the cervix. The muscular layer or tunica muscularis forms the bulk of the uterus and is composed of muscular fibres, blood vessels, lymphatics vessels and nerves. During parturition this muscular layer becomes highly developed. The tunica mucosa is smooth and extends upto the fimbriae of the fallopian tubes. In the body of the uterus the mucous membrane is lined bycolumnar ciliated epithelium. Within the mucous layer are uterine glands

Fuction

The uterus acts as the receptor of the male sperm. Its important for the transportation of the sperm from the site of deporzition to the fallopian tubes which are the site of implantation. It also provides an ideal microenviroment for the growth, nourishment, impalntationand development of the embryo and the fetus during pregnancy. Its also provides protection to the developing fetus and its strong contractive forces help in the expulsion of the fetus at the end of gestation (Vermon,1857).

Layers

The uterus is histologically divided into three layers. The endometrium, The Myometrium and the Perimetrium. The endometrium comprises of the mucosa and submucosa or tunica mucosa and tunica submucosa. The epithelium in the endometrium is simple columnar. Located within the endometrium are loose connective tissues full of neutrophils and lymphoctyes. The uterine glands are also located here. However some regions lack uterine glands but are highly vascularised. The myometrium of the uterus is the thick muscular layer of the uterus and is composed of a thick inner circular layer and a thin longitudinal layer of smooth muscle. The area between these two layers contains large blood vessels. The myometrium comprises of the bulk of the uterus about 90% (Silva,2003).

The perimetrium is also known as the tunica serosa. Its is composed of loose connective and a large no of lymphatic vessels.

Appearance

The ovaries are almond shaped structures, that are located on either side of the uterus and attached to the broad ligament and underneath the uterine tubes. They have a greyish -- pinkish colour and may either have a smooth or irregular surface. In dimensions they are 4cm in length, a breadth of 2cm and a thickness of 8mm. Their weight may range from 2-3.5gm.

Location

The ovaries are located within the ovarian fossa within the lateral wall of the pelvis. The fossae are bounded superiorly by the external iliac vessels. Anteriorly by the obliterated umbilical artery and posteriorly by the ureter. It is important to note that the position of the ovary varies and the above location describes their position in nulliparous women. After the initial pregnancy the ovary becomes displaced and never returns their initial location. The long axis of the ovary is vertical in the erect position. The end near the tube is located near the external iliac vein. At this end are attached the fimbriae and the suspensory ligament of the ovary containing the ovarian vessels. The uterine end is directed towards the pelvic floor and is attached at the lateral angle of the uterus by the ligament of the ovary. The lateral surface contacts the parietal peritoneum while the medial surface is covererd by the fimbriae of the fallopian tubes.

Layers

The histological structure of the ovary is such that it is covered with an epithelium. The germinal epithelium of Waldeyer. Beneath this epithelial layer is a connective tissue called tunica albuginea. The ovary is the further divided into an outer cortex and an inner medulla.

Nourishment and Waste Removal

The ovary is supplied and nourished by the ovarian arteries that are branches from the aorta. The arteries anastome with the uterine arteries and may give some branches to the fallopian tubes. The veins of the ovary emerge from the ovary in form of a plexus the pampiniform plexus. Formed from this plexus is the ovarian vein and this travels with the artery.

Function

The function of the Ovary is to produce the hormones oestrogen and progesterone and ova. The Hormone oestrogen is involved in regulation of female sexual characteristics, preparation of the endometrium for pregnancy and regulation of menstrual cycle. Progestrone is produced during the latter stages of the menstrual cycle and its main function is survival of a fertilized ovum and maintaing pregnancy throughout gestation

The Ovarian Follicle Stages

The Follicular phase

The ovarian cycle is divided into two phases. A follicular phase and a luteal phase. The follicular phase begins with the development of graafian follicles under the stimulation of the FSH hormone or follicle stimulating Hormone. These follicles gradually grow with the resultant release of oestrogen into the blood stream. At around the 10th day one of the follicles becomes distinctly larger than the others. This large follicle is known as the dominant follicle. The other follicle stop growing and become atretic and eventually die out. Oestrogen realeased by the follicle acts on the uterine endometrium making it to proliferate. This signifies the start of the uterine cycle. The dominant follicle reaches 18-20mm in size and ruptures on the 14th -- 16th day of the menstrual cycle. This process is known as ovulation and its signals the end of the follicular phase and the beginning of the luteal phase.

The Luteal phase

Once the ovum is released certain changes take place within the follicle. The follicular cells grow, fat is deposited in them and they assume a yellowish colour. They become known as luteal cells and the whole follicle is known as corpus luteum. These cells of the corpus luteum produce the hormone progesterone which in similarity to oestrogen acts on the uterine endometrium. The levels of these hormones peak around the 24th day of the menstrual cycle. If pregnancy occurs the corpus luteum enlarges in size and produces more progesterone that is used to maintain pregnancy. If pregnancy fails to occur the corpus luteum decreases in size and becomes atretic. Consequently progesterone levels fall. If progesterone is below a certain threshold level it is unable to maintain the proliferated uterine endometrium with resultant shedding and bleeding. This shedding of the uterine endometrium is what is known as menstruation.

The hormonal regulation of the menstrual cycle

The hormone regulation of the menstrual cycle is under control of what is known as the hypothalamic pituitary ovarian axis. The hypothalamus releases a decapeptide known as Gonadotropin releasing hormone or GnRH. This is released into the hypophyseal portal system where it acts on the anterior pituitary (Sherman et al.,1979). GnRH is a neurohoermone and its released in pulsatile nature. The action of GnRH is low during childhood but its activity increases during puberty The anterior pituitary the releases two hormones. The Luteinizing hormone and the follicle stimulating hormone. The LH and FSH are released into the systemic circulation where they act on the target organs. These Hormones are known as gonadotropins because they act on the testes and the ovaries. They are glycoproteins and they are comprised of an alpha and a beta subunit. Its is the beta subunit that is unique to each of these hormones. Luteinizing hormone stimulates the secretion of sex steroids from both the testes and the ovaries. In the testes LH stimulates the synthesis of testosterone. The theca cells of the ovary also produce the production of testosterone but this testosterone is eventually converted into estrogen by the granulosa cells. FSH is important for the maturation of ovarian follicles its is also important for sperm production and maturation by its action on the sertoli cells.