Fertilization, Pregnancy Changes, Fetus Development, Placenta Importance, And Essay On Birth.

Describe fertilization and explain the changes that occur in females during pregnancy.

Explain the development of the foetus in the womb, including the importance of the placenta.

Explain the events of birth.

Explain the role of hormones in maintaining pregnancy, initiating birth and lactation.

Male Reproductive System

The male reproductive system is found outside the body. Its functions include reproduction, transportation of sperms and semen, then discharging the male reproductive cells in to the female sex organ and production and secretion of male sex hormones. The external structure of the male reproductive system include the scrotum, testicles and penis. The penis is the organ used during sex and is made up of three parts, the root, the shaft and the glans (Cleverland Clinic, 2016). The urethra, opens at the tip of the penis and is responsible for transportation of semen and urine outside the body. The scrotum is a skin pouch like and hangs below the penis. It houses the testicles, blood vessels and nerve endings. The scrotum maintains the appropriate temperature for the production of sperms.

The testicles also called the testes, are two ball like structures found inside the scrotum. The testes manufacture sperms and secrete testosterone, the male sex hormone. Inside the testes are the seminiferous tubules where spermatogenesis occurs. The epididymis is connected to the vas deferens and carries and store sperms. The seminal vesicles produce substances like fructose which provide energy to sperms. Prostate gland found just below the bladder secrete fluid that acts as a nourishment to the sperms during ejaculation. The Cowper’s gland, found after prostate gland secretes a basic fluid which neutralizes any acidity along the urethra. The fluid also lubricates the urethra.

According to Lumen (2018), the female reproductive system is made up of two key parts, the uterus and the ovaries. Other internal parts include the cervix, fallopian tube, vagina and ovary. The external parts of a female reproductive system are vulva, pudendal cleft, mons pubis. Labia majora and minora, clitoris and the Bartholin’s gland. The uterus produces uterine secretions and also the vaginal fluids, it is in the uterus where the fertilized egg develops in to a foetus. The uterus also allows passage of the male gametes to the fallopian tube. The uterus can be anatomically into four parts, the corpus, cervix, fundus and internal os.  The ovaries produce the ova, the female reproductive cells. The ovaries are usually two. They are also responsible for secretion of progesterone and estrogen hormones.

Libia majora (large lips) encloses and provides protection to the female reproductive parts. Libia minora (small lips) surround the vagina and just inside libia majora. Bartholin’s gland, found besides the vagina, secretes a fluid that used for lubrication during sex. The clitoris is a small and sensitive organ in the female reproductive system. It is where the labia minora meet and is covered with the prepuce (Web MD, 2017). Vagina, also called the birth canal, connects the cervix.. The fallopian tube or the oviduct connects the uterus with the ovaries. It is the passage through which the ova travels to the uterus from the ovaries. Fertilization and conception occurs at the oviduct (Zimmermann, 2018).

Through oogenesis, approximately every month an ovum is released by the ovaries and send through the oviduct. If the ovum is not fertilized, it then flushes out through menstruation. Menstruation is the shedding of the uterine wall (endometrium) that occurs almost every month in women above puberty stage except when pregnant. Menstruation stops after reaching menopause. The menstruation cycle ranges between 25 to 36 days. This cycle is regulated by two hormones, the luteinizing hormone and the follicle stimulating hormone. These hormones are secreted by the pituitary glands and stimulate the ovaries to secrete the progesterone and estrogen (Knudtson, 2016).

Female Reproductive System

The menstruation cycle has four stages, namely the menstruation, the follicular phase, ovulatory phase and then luteal phase (Wangari, 2009). The cycle begins with menses where the women experience nausea, abdominal and back pains. After menses, the pituitary glands start secreting the follicle stimulating hormone (FSH). The FSH causes the development of the Graafian follicles and stimulates the secretion of oestrogen which brings about repair and healing of the uterine wall. Accumulation of the oestrogen stimulates the release of lutenising hormone (LT) which initiates maturity of the Graafian follicle (Mayo clinic, 2016). The mature Graafian follicle releases the ovum (a process called ovulation) then turns into a yellow body, the corpus luteum. The LT stimulates secretion of progesterone which functions to increase the blood supply and thickening of the endometrium in preparation for implantation of the blastocyst (Health line, 2018). If fertilization occurs, level of progesterone increases, blocking the FSH from stimulating maturity of another Graafian follicle. In no fertilization, the corpus luteum disintegrates and menses occurs (Hawkins & Matzuk, 2008).

Monroy (2017) describes fertilization as the process of union nucleus of paternal and maternal origin to form a zygote. This process occurs in the fallopian tube after copulation. A single ejaculation contains millions of sperms but only one fertilizes the ovum. As the ovum moves in the oviduct, it secretes chemical substances which are neutralized by enzymes produced by the acrosome before fertilization. The acrosome bursts open as soon as the sperm comes into contact with the ovum, releasing lytic enzyme which digests the ovum membrane (Albert, Johnson &Lewis, 2002). The acrosome turns into a filament for penetrating into the ovum, then the vitelline membrane undergoes changes which hinders any other sperm from penetrating. The cytoplasm of the sperm cell burst to release the nucleus which fuses with the female nucleus to form a diploid zygote (Dale, 2013).

During pregnancy, a woman is faced with many changes, physical, known and others come as a surprise (Nierenberg, 2015). According to Nierenberg 2015 some changes which come by surprise are enlargement of breasts and varicose veins in the genitals. Women may experience bleeding gums during pregnancy which exposes them to infections. The increased level of oestrogen may lead to growth of thicker and healthier hair on the body of the woman. Some women tend to have stretch marks on their skin. The breasts become more tender and full with the nipples becoming more sensitive to touch and also darken. There is change in their body temperature due to increased metabolic reactions.

After fertilization, the zygote undergoes a couple of mitotic divisions as it moves down and implants on the uterine wall. During the first month of the embryo, the amniotic sac forms around it. The placenta also develops. Blood vessels and the heart also develop. By the third month, the foetus has arms and legs. The reproductive organs begin to develop too. The baby is about 6 inches by the fourth month. The baby has grown muscles and its movements could be felt by fifth month. Hair starts growing on its head. By the ninth month, the lungs are almost fully grown, the foetus can blink and respond to any stimuli (Cleverland clinic, 2014). The placenta is the point of association between the foetus and the mother. It allows a selective movement of materials, including nutrients, oxygen, antibodies, antigens, carbon dioxide and metabolic waste, between the mother and the baby. It also allows passage of drugs and other chemicals in to the system of the foetus, hence it is prohibited to abuse drugs and substances during pregnancy.

Menstruation Cycle

The reduction of progesterone in the mother’s system stimulates release of oxytocin hormone by the posterior pituitary gland. This is the onset of birth. Oxytocin allows the myometrium muscles to contract, which occurs in wave to expel the foetus (Kumar & Magon, 2012). The waves lead to labour pains which are accompanied by dilation of cervix and rapture of amnion, releasing the amniotic fluid. Contraction of the urine wall spreads throughout the uterus, pushing the foetus out through the birth canal. After the baby is out, the umbilical cord is cut to separate the baby from the placenta, which is expelled later (Beck & Huffman, 2017).

After implantation has occurred, human chorionic gonadotropin, stimulates release of ovum its development and also it is associated with early pregnancy symptoms like fatigue, nausea and missing of menses, is produced. The corpus luteum produces large amounts of progesterone until the tenth week of gestation (Kumar & Magon, 2012). Almost 100 grams of progesterone are produced between the sixth and eight weeks to support pregnancy. The progesterone helps prevent preterm labour. It also maintains the functionality of the placenta. It also causes breast tenderness, heartburns and the pains of the pubic bone.  Oestrogen also is produced by the placenta and helps stimulate the release of progesterone in the last month of pregnancy (Kafeel, 2011). Other protein hormones such as the placental lactogen, growth hormone variant, calcitonin and relaxin are used in maintenance of pregnancy.

Conclusion

Therefore, the sperms are the male gametes while ova are the female gametes. They fuse during fertilization to form a zygote. This fertilization takes place at the fallopian tube or the oviduct. The zygote is then implanted on the uterine wall where it divides meiotically. It develops from a zygote to a full grown foetus and is born after nine months. If fertilization does not take place, the ovum and the uterine wall are shed as blood.

References

Alberts B., Johnson, A. & Lewis J. 2002. Molecular Biology of the Cell. 4th edition. New York: Garland Science. Available from: https://www.ncbi.nlm.nih.gov/books/NBK26843/

Beck, A. C. & Huffman, J. W. 2017. Parturition. Encyclopedia Bratannica. Retrieved from: https://www.britannica.com/science/parturition

Cleverland Clinic. 2016. Male reproductive system. Retrieved from: https://my.clevelandclinic.org/health/articles/9117-male-reproductive-system

Cleverland Clinic. 2014. Fetal development: stages of growth. Retrieved from: https://my.clevelandclinic.org/health/articles/7247-fetal-development-stages-of-growth

Dale, B. 2013. Mechanism of fertilization: Plants to Humans. Berlin: Springer Publishers

Hawkins, S. M., & Matzuk, M. M. 2008. Menstrual Cycle: Basic Biology. Annals of the New York Academy of Sciences, 1135, 10–18. https://doi.org/10.1196/annals.1429.018

Kumar, P., & Magon, N. 2012. Hormones in pregnancy. Nigerian Medical Journal?: Journal of the Nigeria Medical Association, 53(4), 179–183. https://doi.org/10.4103/0300-1652.107549

Knudtson, J. 2016. Menstrual cycle. Retrieved from: https://www.msdmanuals.com/home/women-s-health-issues/biology-of-the-female-reproductive-system/menstrual-cycle

Kafeel, B. 2011. Role of hormones during pregnancy. Retrieved from: https://www.onlymyhealth.com/role-hormones-during-pregnancy-1310534790

Lumen. 2018. Female reproductive system. Retrieved from: https://courses.lumenlearning.com/boundless-ap/chapter/the-female-reproductive-system/

Monroy, A. 2017. Fertilization. The Encyclopedia Britannica, Inc. retrieved from: https://www.britannica.com/science/fertilization-reproduction

Mayo Clinic. 2016. Women’s health. Retrieved from: https://www.mayoclinic.org/healthy-lifestyle/womens-health/in-depth/menstrual-cycle/art-20047186

Nierenberg, C. 2015. Body changes during pregnancy. Retrieved from: https://www.livescience.com/50877-regnancy-body-changes.html

Wangari, M. 2009. Secondary Biology, Form 3. Nairobi: KLB.

Web MD. 2018. Guide to female reproductive system. Retrieved from: https://www.webmd.com/sex-relationships/guide/your-guide-female-reproductive-system#2

Zimmermann, K. A. 2018. Reproductive system: Facts, functions and diseases. Retrieved from: https://www.livescience.com/26741-reproductive-system.html