NEET Biology Notes Animal Reproduction day and Reproductive Health Fertilisation
The process of fusion of a sperm with an ovum is called fertilisation. During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum and induces changes in the membrane that blocks the entry of additional sperms. The secretions of tne acrosome help the sperm to enter into the cytoplasm of the ovum through the zona pellucida and the plasma membrane.
• Important sperm lysins are hyaluronidase (that acts on ground substance of follicle cells), corona penetrating enzyme (that dissolves corona radiata) and zona lysine or acrosin (that helps to digest the zona pellucida).
• Optimum pH, Ca and Mg2+ ions concentration and temperature are essential for acrosomal reaction.
• This induces the completion of the meiotic division of secondary oocytes. The second meiotic division is also unequal and results in the formation of second polar body and a haploid ovum. Soon the haploid nucleus of the sperm and that of ovum fuses together and form a diploid zygote. Zygote is the result of fertilisation. It has 46 chromosomes in contrast to haploid sperm (23 chromosomes) and ovum (23 chromosomes).
Various stages of human pregnancy can be divided into prenatal period (before birth of baby) and postnatal period (after birth of baby).
Embryo Development and Pregnancy
The gestation period of human pregnancy is about 9 months. The delivery of foetus or child birth is called parturition. In parturition, vigorous contraction of the uterus at the end of pregnancy causes delivery of the foetus.
Complex neuroendocrine mechanisms are involved with parturition. The signals for parturition originate from the fully developed foetus and the placenta, which induce mild uterine contraction is called foetal ejection reflex. This triggers release of oxytocin from the maternal pituitary. Oxytocin induces stronger contractions resulting in to expulsion of the baby outside of the uterus through the birth canal, Relaxin hormone increases the flexibility of pelvic ligaments, dilates the uterine cervix mother for child birth.
Lactation helps mother in feeding the new born baby. The mammary glands undergo differentiation during pregnancy and start producing milk towards the end of pregnancy by the process of lactation.
It causes milk ejection whereas, prolactin causes milk production. The milk produced in initial days of pregnancy is called colostrum, which develops resistance for the new born baby. Colostrum also acts as a laxative, removing foetal wastes, called meconium.
World Health Organisation (WHO) states that reproductive health is a total well-being in all aspects of reproduction, i.e. physical, emotional, behavioural and social.
Reproductive health programmes are important in the areas of better awarness about sex-related matters, increased number of medically assisted deliveries and better postnatal care leading to decreased maternal and infant mortality rates, increased number of couples with small families, better detection and cure of STDs and overall increased medical facilities for all sex-related problems, etc. All these aspects indicate improved reproductive health of the society.
India first initiated the action plans and programmes in 1957 at the national level to attain total reproductive health. These programmes are called Family Planning Programmes. Currently, they are called as Reproductive and Child Health Care (RCH) Programmes.
Some Objectives of Reproductive Health
The objectives and requirement of RCH programmes are
- Create awarness among people for reproduction related aspects.
- Provide facilities and support for building up a reproductively healthy society.
- Introduction of sex-education in schools to give right information.
Educating infertile couples and those in marriageable age group about the following :
- Birth control options
- Care of pregnant woman
- Postnatal care of mother and child
- Importance of breast feeding.
- Various assisted reproductive technologies available for infertile couple.
Uncontrolled increase in population leads to high pressure on resources and food. Therefore, birth control is required. .
The increased medical facilities and improved technologies resulted in better living conditions, which have explosive impact on the growth of population.
The reasons for population explosion are
- Decline in death rate, materaaf and infant mortality rate.
- Increase in the number of people in the reproductive age.
Therefore, control of population explosion is necessary.
Birth Control or Contraception
The population growth can be controlled only by adopting suitable contraceptive methods.
Some other ways include
- Raising the marriageable age to 18 for females and 21 for males.
- Incentives given to couples with small families.
- Methods of Birth Control
Natural methods of contraception work on the principle of avoding chances of meeting between the gametes. This can be done by following periodic abstinence, coitus interruptus and lactational amenorrhoea.Barrier methods for fertilisation is based on preventing ovum and sperm coming closer. This is done with the help of condoms, diaphragms,’cervical caps, spermicidal creams, etc. Intra-Uterine Devices (IUDs), are introduced into the uterus. The IUDs in use are Lippes loop, Cu-T, Cu-7, multiload 375, LNG 20, etc. The Cu ions released by IUDs suppress sperm motility.
Oral contraceptives are hormonal prepartions used as pills, e.g. Saheli (once a week pill). Injections and implants are progesterone-estrogen combination. Their effective period is longer than pills. Surgical methods block the transport of gametes and thereby prevent conception. Vasectomy is used in males and tubectomy in females. Vasectomy and tubectomy is permanent method of contraception.
- Medical Termination of Pregnancy (MTP)
Voluntary or intentional termination of pregnancy before full term is called Medical Termination of Pregnancy (MTP) or induced abortion. MTP has been legalised by the government of India in 1971 with strict conditions to avoid its misuse, especially in case of illegal female foeticide.
MTPs are safe during first trimester (up to 12 weeks of pregnancy) after that MTPs are riskier.
Prevention of Sexually Transmitted Diseases (STDs)
Diseases or infections, which are transmitted through sexual contact are called Sexually Transmitted Diseases (STDs) or Veneral Diseases (VDs) or Reproductive Tract Infections (RTI).
The infections could be avoided/prevented by the following practices
- Avoiding sex with unknown partner or multiple partners.
- Using condoms during coitus.
- Seeking medical help in case of doubt and getting it completely cured.
e.g. Syphilis, gonorrhoea, chlamydiasis, trichomoniasis, AIDS, hepatitis-B, genital herpes, etc.
There are special techniques called Assisted Reproductive Technologies (ART) to help couple produce children. These techniques are
- In Vitro Fertilisation
In Vitro Fertilisation (IVF) or test-tube programme is the method in which ova from the wife or a donor female and the sperms from the husband or a donor allowed to fuse under simulated conditions in the laboratory.
- Zygote Intra Fallopian Transfer (ZIFT)
In this method, zygote or embryo up to eight blastomeres stage is transferred into the Fallopian tube.
- Intra Uterine Transfer (IUT)
Embryos with more than eight blastomeres are transferred directly into the uterus in this method.
- Gamete Intra Fallopian Transfer (GIFT)
It is a method in which transfer of an ovum collected from a donor female into another female is done, who cannot produce ova but can provide suitable conditions for fertilisation and further development of the foetus up to parturition.
- Intra Cytoplasmic Sperm Injection(ICSI)
It is a method in which a sperm is directly injected into the ovum to form an embryo in the laboratory and then embryo transfer is carried out. It is used in case of male infertility or low sperm count.
- Artificial Insemination
It is- the method in which semen is collected from the husband or a healthy donor and artificially introduced into the vagina or into the uterus.
This method is used in such cases, where infertility is due to the inability of the male partner to inseminate the female or due to very low sperm counts in the ejaculates.
Amniocentesis is a prenatal diagnostic technique, in which a sample of amniotic fluid from the womb of a pregnant woman is taken during the early stages of foetal development and the cells are cultured and analysed.
This technique helps in diagnosis of chromosomal abnormalities, the sex of the foetus and the development disorders could be detected. However, it is being misused by some people for destroying the female foetuses.