Biological Process Offspring Production

Introduction

Reproduction is referred to the biological process through which new individuals from the parents are produced. This is a natural process which involves complex sequence of hormones and physiological changes of the body to develop the offspring. In this essay, the reproductive organs and hormones involved in reproduction are to be described along with the physiological changes and stages of birth related to reproduction are to be explained.

Description of structure and function of uterus and testis

The uterus is referred to as the hollow muscular organ which is located in the pelvic region of the female positioned between the urinary bladder and the rectum. The lower end of the uterus in human female opens in the form of vagina and the upper end which is known as fundus is connected with the fallopian tube. The key function of the uterus is to nourish the egg released through the fallopian tube and arranges the uterine wall for implantation of the fertilised egg to form the embryo (Mayo et al. 2016; Menon et al. 2016).

The testis is the reproductive glands of the male and they are two in number in male. Each of the testes is covered by a fibrous tough tissue known as tunica. The testis is divided on the inside in the form of lobules and each lobule contains U-shaped tubes that are tiny in nature known as seminiferous tubules. These tubules open in the form of rete testis where the ducts or tubes are tightly coiled to form epididymis that joins the vas deferens. The function of testis is to produce testosterone hormone and the sperm which is produced by the seminiferous tubules of the testis (Urahama et al. 2016; Li et al. 2015).

Description of happening when fertilisation occurs

The event of fertilisation initiates with the attachment of the sperm with the egg membrane. The acrosome reaction of the spermatozoa is required for the association of a sperm with the egg as in this reaction plasma membrane of the sperm and egg are fused. After this reaction, when the acrosome of the spermatozoa which is the anterior tip of the sperm undergoes structural changes the vesicle of the acrosome bursts open. This is followed by the plasma membrane of the spermatozoon fuse at acrosomal tip along with the membrane which is surrounding the acrosomal vesicle in order to form the opening with the egg. The formation of the opening causes the acrosomal granule to dissolve which forms a substance named lysin that is effective to break the vitelline coat of the egg creating passage for spermatozoon to meet the egg. The acrosomal region of the membrane which is opposite to the opening adhere to the spermatozoon nuclear envelop and develop a shallow pocket which later elongates into a thin tube which is acrosomal tubule extending from the egg. Thus, the tubule helps the spermatozoa nucleus to be drawn into the egg nucleus to fertilise it. After the entry of the nucleus of the sperm, which is now known as pronucleus, it is seen to initiate swelling by dispersing its chromosomal material to form similar in structure to the female nucleus. The male pronucleus then rotates 180º and meets the female pronucleus to initiate cell division for forming blastocyst. The blastocyst then makes contact with the endometrial wall of the uterus where they get implanted with the action of high level of progesterone and estrogen (Scarselli et al. 2018; Pera, 2017; Esterhuizen et al. 2015; Ahmed et al. 2018).

The FSH and LH are key hormones involved in managing menstruation cycle. The key role of FSH during the cycle is to cause egg maturation in the ovary so that it can be prepared for fertilisation. The role of the LH is to stimulate the release of egg from the ovary so that it can be exposed for fertilisation (Oduwole et al. 2018; Sacchi et al. 2016). During the initial stage of the menstrual cycle, the estrogen levels are low and the pituitary releases FSH in high amount for the maturation of the egg. As the egg gets matured with the effect of FSH, the estrogen levels are also increased in the blood on the 7th day. This high level of estrogen indicates the sudden release of LH from the pituitary gland. The high level of LH creates complex events in the follicles to prepare the egg for final maturation and later follicular collapse for release of the egg into the ovary on 14th day. The cells of the follicle left after the release of the egg transforms into corpus leutum. This leads to indicate the production of high level of progesterone production along with estrogen to prepare the wall of the uterus to form endometrium for the implantation of the egg. In case the egg did not get fertilised, it is not implanted and released from the uterus in the form of menstrual flow by 28th day. After the release of the egg into the ovary from its follicle the level of LH as well as FSH decreases and with the initiation of new cycle the FSH again increases (Farland et al. 2017).

Human chronic gonadotropin: Human chronic gonadotropin (hCG) hormone is a form of placental hormone which is produced by syncytiotrophoblasts cells after the implantation embryo during the second week of pregnancy. The function of hCG hormone is to interact with LHCG receptor present in the ovary to offer support to the corpus leutum which secretes progesterone to supports the endometrial lining for maintaining pregnancy (Korevaar et al. 2017).

Progesterone: The Progesterone is produced by the corpus leutum present in the ovaries and by the adrenal glands. The function of progesterone is to regulate the proper formation of endometrium within the uterus so that a perfect environment is created for the implantation of the fertilised egg (Arendt and Kuperwasser, 2015).

Oxytocin: The Oxytocin is produced in the hypothalamus which is later secreted into the body by the pituitary gland present at the base of the brain. It is neurotransmitter and the key function of the hormone is to stimulate the relaxation of the uterine smooth muscles during birth and stimulation of milk into the breast in mother after birth (Xu et al. 2017).

Describing the changes that occur in woman’s body after pregnancy

The three vital and visible changes that occur to the woman’s body after pregnancy are as follows:

The breasts of the women are enlarged after pregnancy making them feel fuller and tender. The nipple also becomes sensitive to touch and the areolas which are the skin surrounding the nipples are seen to be darkened and enlarged in this phase. In the third trimester, the women breasts are also seen to initiate leaking colostrum which is milky fluid. This occurs because during pregnancy the rising hormone levels such as oxytocin, progesterone and others indicates the breast cells to be prepared for milk production. The rising hormone levels also indicate the breast cells to be produced in more amounts so that they are prepared for milk production which makes the breast size get increased and become tender (Żelaźniewicz and Pawłowski, 2019).

After pregnancy, the cardiac output of the woman increases with usually reaching 30-35% increase in the third trimester. The increase is mainly caused by estrogen which raises the cardiac output by increasing stroke volume mainly through high overall blood volume. The heart rate also increases but not more than 100 beats/min. The changes in the cardiac output occur during pregnancy because more blood has to be pumped to the uterus to let the foetus grow properly along with maintaining blood flow for normal function of the woman’s body (Meah et al. 2016).

The blood volume increases by 30-50% gradually in pregnant woman and the blood plasma volume also increases by 40-50% during pregnancy. This is because increased amount of blood flow is required to deliver nutrient and oxygen through the placenta to the growing foetus (De Haas et al. 2017).

Explaining the three stages of birth

First stage: In the first stage, during the latent phase the mother receives uterine contractions on regular intervals which are followed by active phase in which the mother perceives painful uterine contraction on regular basis with cervical effacement of substantial degree along with rapid cervical dilation up to 5 cm until full dilation in the second stage. During the process of effacement, the cervix is incorporated into the uterine lower segment and during contraction, the uterine muscles shorten the upper segment by contracting at the same time drawing the uterine lower segment downwards in the form of a gradual expulsive motion (Trevathan, 2017).

Second stage: The second stage includes fetal expulsion which initiates when full dilation of the cervix is achieved and ends with the baby being born. As the pressure increases on the cervix, the mother feels pressure in the pelvic region and an urge to push. During initiation of the normal second stage of birth, the head of the foetus is fully seen to be engaged in the pelvis with the widest head diameter passed below the pelvic inlet. After this process, the head of the foetus descends into pelvis reaching the pubic arch and released through the introtius of the vagina. The appearance of the head of the foetus at the orifice of the vagina is termed as crowing and this stage ends with the expulsion of the baby outside (Trevathan, 2017).

Third stage: The third stage initiates just after the foetus is expelled of the vagina and end after the placenta is totally expelled. The expulsion of the placenta initiates as an indication for the physiological separation of the foetus from the uterine wall. The average time taken after the foetus is expelled until the complete expulsion of the placenta is 10-12 minutes (Trevathan, 2017).

Conclusion

The above discussion informs that uterus and testis is the key reproductive organ of female and male. The egg gets fertilised with sperm that gets implanted in the uterus causing pregnancy during which women blood cells and cardiac output increases with enlargement of breast.

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References

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