Reproduction

What is Reproduction?

Reproduction is how organisms give birth to new life or offspring. There are two types of reproduction – sexual and asexual. To put it in simple terms, sexual reproduction is when the male and female of a species come together to produce offspring, whereas, in asexual reproduction, a single organism by itself tends to produce offspring with simple cell division processes like mitosis, etc.

Reproduction in Humans

The human reproductive system consists of complex system organs and signalling molecules that interact and aid in the human ability to give rise to offspring. Distinguished from all the other organ systems, with two anatomically different organ systems in male and female, it is a slow-developing system, obtaining a proper maturity with the onset of adolescence in human beings. The seven essential features in human reproduction are –

• Release of an ovum or egg during the reproductive cycle.

• Internal fertilisation of the ovum by sperm cells.

• Transportation of fertilized ovum to the uterus.

• Implantation of the blastocyst, the early embryo development from fertilised ovum in the wall of the uterus.

• Formation of the placenta in the womb.

• Birth of child and expulsion of the placenta.

• Care of the child with the eventual return of maternal organs to virtually their original state.

Specific organs in both male and female reproductive systems are required for these biological processes to occur. These are explained in detail down below,

The Male Reproductive System 

• The testes are the reproductive organ of the male reproductive system, which are the sources of sperms and androgens, the male sex hormones.

• The sperm consists of head and tail and consists of genetic substances called chromosomes, that carry the genetic information to be imprinted to the offspring. They carry 23 chromosomes, including both X and Y chromosomes.

• The other genital organs are the epididymis; the ductus, or vasa, deferential; the seminal vesicles; the ejaculatory ducts; and the penis. The accessory organs include the prostate and the bulbourethral (Cowper) glands. 

• The production of sperms or spermatogenesis occurs in seminiferous tubules, and their maturation or spermatogenesis occurs in the epididymis.

• The accessory organs – prostate glands and Cowper’s glands secrete Plasmin and flush urethra of residual substances, respectively.

The Female Reproductive System

• The ovaries are the reproductive organ of the female reproductive system, which are the sources of ova (eggs) and estrogens and progestogens, the female sex hormones.

• The female ova contains 23 chromosomes of (X, X).

• The internal organs of the female reproductive system include – ovaries, fallopian tubes, uterus, cervix, and vagina.

• The ovaries function as the source of ova through ovulation and is a part of the menstrual cycle, and also produce sex hormones that facilitate childbirth and other essential functions.

• The fallopian tubes act as the passages carrying the ova to the uterus.

• The uterus, commonly known as the womb, consists of muscular walls and lining where the embryo gets implanted upon successful fertilisation of the ova.

• The cervix is a narrow structure below the uterus that allows fluids to pass out of the body.

The Process of Reproduction

• The reproduction process begins with intercourse, where sperm cells from the male body enter the female reproductive tract due to copulation.

• The ovum consists of a central nucleus containing the female’s genetic material. Once fertilised, it undergoes a series of cell divisions and leads to the formation of the primary nucleus of an embryo.

• After combining male and female chromosomes, the ovum gets fertilized, which is termed the zygote.

• After about 72 hours of fertilisation, the zygote reaches the uterine cavity and after a week or so, the zygote forms a hollow bubble-like structure known as the blastocyst.

• Then implantation occurs, which is the process of adherence of blastocyst to the uterine wall.

• These blastocyst cells slowly grow into an embryo and then a foetus.

• Subsequently, the development of the umbilical cord and placenta is an exchange track of nutrients and waste between the mother and foetus.

• As the foetus grows, it stretches the uterine wall and thins as this progresses, the uterus rises out of the pelvis and fills the abdominal cavity.

• There are 3 periods of gestation – 

• Pre-Embryonic period: Weeks 2-4

• Embryonic period: Weeks 4-8

• Foetal period: Week 9

• The whole period of pregnancy is divided into 3 trimesters –

• First trimester – conception to 12 weeks.

• Second trimester – 12 to 24 weeks.

• Third trimester – 24 to 40 week

• After approximately 9 months past conception, the female body prepares itself for delivery of the baby as the baby may turn into a head-down position for birth. The delivery involves 3 significant stages as follows:

• Stage-1: is characterised by the baby (foetus) dropping further into the pelvic cavity, placing pressure on the cervix. Following this pressure, the cervix begins to expand.

• Stage-2: This stage is characterised by full dilatation of the cervix and delivery of the newborn baby

• Stage-3: This stage is characterised by hematoma formation and delivery of the placenta. During this stage, fundus massage helps cause the uterus to contract upon itself, creating its pressure dressing to stop uterine bleeding.

Conclusion:

Thus, we can see how modern Science has helped us to decipher the whole process of human reproduction by concentrating on the elucidation of the basic cellular activities that contribute to human embryological development and the day-to-day function of the reproductive organs.