Research Paper Example on Female Reproductive Structures

Part 1) Describe either human male or the human female reproductive structures and their functions.

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The female reproductive system consists of both internal and external organs. Its basic purpose includes the reproduction of the human species. For the entire system to fully take part in supporting pregnancy and giving birth, it has to undergo sexual maturation. The uterus or the womb is part of the female internal reproductive organs. It refers to the hollow organ that is centrally placed in the pelvis. The womb holds the developing baby during the gestation period. The uterus consists of two parts that include the cervix and the corpus. The corpus makes part of the large section of the uterus that expands such that a baby is able to grow. The cervix makes part of the lower part of the uterus such that it unseals into the birth canal (Waters). The opening present in the cervix enables the movement of sperm up to the uterus and allows the removal of the menstrual blood. The opening tends to dilate when a woman is in labor such that it becomes easier for the baby to move across the birth canal. Other organs present in the internal female reproductive system are fallopian tubes. The tubes emanate from the upper section of the uterus from all sides whereby they allow the movement of eggs from the ovaries for them to reach the uterus. The fertilization process whereby the sperm fertilizes the egg takes place in the fallopian tubes whereby the fertilized egg flows into the womb and then gets implanted (Mawhinney and Mariotti 232-251). On each side of the uterus and almost close to the opening of the fallopian tubes, there are small and oval ovaries. The ovaries are in charge of producing hormones and hold the eggs. It is important to note that during birth, the female reproductive system has about one to two million eggs which are located in the ovaries. However, about three hundred of the eggs will undergo maturation throughout the lifetime of a female.

The external female reproductive system consists of the labia majora. The labia majora are two projections which are fleshy in nature that acts as shields and cover the external female organs. They are also referred to as large lips and quite similar to the scrotum that is present in the male reproduction system. The labia are also surrounded with hair when individuals reach puberty. The labia have glands whose purpose is to produce oils and sweat. The labia minora is found inside the labia majora and refer to tiny projections of flesh that cover the openings that lead to the vagina and the urethra. They are also referred to as small lips. The urethra enables the movement of urine. The Bartholin glands are also parts of the external female body which are found close to the vaginal opening and produce a fluid discharge or mucus. The clitoris is found next to the intersection of the labia minora. The clitoris is shielded by the prepuce which presents itself as skin fold and is comparable to the foreskin present in males. It is important to note that the clitoris tends to be very sensitive and is comparable to the penis in males. It responds to stimulation similarly to the penis.

It is important to note that the female reproductive system is designed to perform various functions. It releases the egg cells, the oocytes or the ova, that are important for reproduction to take place. The system is structured to allow the movement of the ova to the location that fertilization takes place. Conception takes place at the fallopian tubes whereby the sperm fertilizes the egg. After fertilization takes place, the fertilized egg implants itself into the uterine wall and hence resulting in the first steps regarding pregnancy. When the implantation does not take place or if the fertilization does not occur, the system shifts to menstruation which refers to the monthly release of the uterine wall. It is important to note that the female system releases sexual hormones that preserve the reproductive phase (V. Sirotkin 325-336).

Part 2) Define the hormones involved and the events that take place during the human female menstrual cycle.

The menstrual cycle refers to the cycle that takes place every month in the female reproductive system whereby the egg and the follicle mature, ovulation takes place, and the uterine wall is prepared for pregnancy. If a woman is not pregnant or rather if the egg is not fertilized, the shedding of the uterine wall takes place and then flows as menstrual blood. It is important to note that the cycle mostly takes place for twenty-eight days. The period in which the menstrual cycle begins or rather when the adolescence period begins and the female body begins shedding menstrual blood is referred to as menarche. The periods tend to take place until the woman reaches menopause.

A regular menstrual cycle occurs because of the hormonal path that is directed from the hypothalamus up to the pituitary gland and then flows to the ovary then shifts to the uterus. The associated organs release particular hormones that have impacts on the organs present in the path. The path, in this case, refers to the hypothalamic-pituitary-gonadal axis. The twenty-eight day menstrual cycle period is divided into three sections. The three phases include follicular, ovulation and luteal phases.

The follicular phase takes place from the first to the thirteenth day. It is viewed as the first phase which takes part half of the whole cycle. In this phase, the oocytes develop on the ovaries. The length of the follicular phase varies in regards to the complete duration of the cycle. The idea is that a regular cycle with twenty-eight days will have fourteen days of the follicular phase while for a cycle that has thirty-two days, the follicular phase will take about eighteen days. The phase is also referred to as the proliferative stage as the uterine lining develops during this stage. The ovulation phase takes place in the middle of the cycle whereby the mature egg from a follicle will be released at this stage. The stage takes place to form the fourteenth day of the cycle in a regular cycle of twenty-eight days (Sheu 258-259).

The luteal phase is viewed as the second section of the cycle and its stage where the embryo either implants on the uterine wall or does not implant on the wall. If the implantation of the embryo takes place, the initial stages of the pregnancy began. However, if the implantation does not take place, the level of hormones will decrease such that a new cycle will develop. The luteal phase is also identified as the secretory phase due to the production of progesterone. The release of progesterone fuels the growth of the arteries and the glands that are part of the endometrium such that it becomes spongy and thick.

The follicular stage of a new cycle will initialize due to a significant drop in progesterone and estrogen levels in the blood. The drop in the levels of hormones will take place at the final stages of the luteal phase when embryo implantation does not take place. Also, the drops in the levels of hormones will marsh the uterine wall and hence causing the flow of menses resulting at the beginning of a new cycle. The low hormone levels in the blood tend to send a positive response to the hypothalamus which is found in the brain such that the gonadotropin releasing hormone is released. The hypothalamus secretes the GnRH hormone such that it moves to the receptor that is present in the pituitary gland.

The pituitary gland is present in the brain, and thus when the GnRH connects itself to its receptor that is present on the pituitary, the pituitary gland starts to release the follicle stimulating hormone (FSH) and the luteinizing hormone (LH). The follicle stimulating hormone and the luteinizing hormone then flow to their receptors which are present in the ovaries. The receptors of the LH and the FSH are found on the eggs surface that is covered by follicles. When the LH and the FSH attach themselves to the receptors, the follicles start developing while the eggs start to mature. When the follicles develop during the whole follicular phase, they tend to release estrogen. The estrogen which is produced by the ovaries works on the uterus such that a new uterine lining is formed. It is important to note that the uterine lining develops when the follicular phase is taking place for the purpose of getting ready for the implantation of the embryo (Bharadwaj, Kulkarni and Shen 245-255).

The follicles present in the ovary have eggs (each follicle with an egg) such that it takes shape in the form of a sphere. The theca cells and the granulosa cells are found on the surface of each follicle. At the beginning of the follicular phase, the granulosa cells have the FSH receptor cells while the theca cells have only the LH receptor cells. The egg in each follicle tends to have a nucleus which is referred to as a germinal vesicle. The germinal vesicle supports the chromosomal structure of the egg. Also, the egg is covered by a shell known as the zona pellucida which is thin and hard.

At the entire early phase of the follicular phase that takes place between the first and the sixth day, the ovaries will begin to stimulate the growth of various follicles. At the middle of the phase which is the seventh day, a single follicle will expand in size such that it becomes larger than the rest which is present in the ovaries. The follicle, which is perceived to be naturally selected, is then identified as the Graafian follicle or rather the dominant follicle. When the dominant follicle reaches a diameter of about 19-22 millimeters, the inside of the egg matures such that the ovulation phase commences.

At the fourteenth day of the cycle, the ovulation begins whereby the Graafian follicle ruptures and then the egg that has matured is released. The ruptured Graafian follicle, therefore, contains no egg and instead changes into a temporary endocrine organ which is identified as the corpus luteum. The development of the of the corpus luteum results in the start of the luteal phase that takes place between the fifteenth day and the twenty-eighth day of a normal menstrual cycle. Its main purpose is to releases the estrogen and progesterone hormones. The purpose of the progesterone hormone is to sustain the endometrium which is the uterine wall. The hormone is also essential for the implantation of the embryo and pregnancy (V. Sirotkin 325-336).

After the egg has been released, it will be then pushed by the fimbria into the fallopian tube. The fimbria, in this case, refers to fingerlike projections that are found at the end of the tube. The push marks the beginning of the journey of the egg across the fallopian tube until it reaches the uterus. When sexual intercourse took place at the ideal time, the sperm will begin piercing the outer part of the egg for about twelve to twenty-four hours after ovulation. When the egg arrives in the middle of the fallopian tube, on sperm would have managed to fully penetrate the shell such that fertilization or the replication of the DNA takes place. After ovulation has taken place and thirty hours have already passed, the egg which s newly fertilized then becomes a zygote. The zygote, in this case, is an embryo with two cells. After three days, the embryo develops to a zygote with eight cells. After five days, the embryo develops into a blastocyst whereby the cells are about seventy to eighty, and after six days whereby the cycle is at its twenty-first day, the blastocyst may either implant on the uterine wall or fail to implant. When the implantation takes place, the embryo starts to release a hormone which is identified as the human chorionic gonadotropin or the HCG (V. Sirotkin 325-336).

The HCG present in blood will stimulate the corpus luteum to continue performing its role of releasing estrogen and progesterone until the period in which the...