Human Reproduction

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Sex is a phenomenon of life that sustains life forms on the planet earth. The life cycle of every living kind (a sexual population) spreads the advantageous traits in a way that it makes the next generation more capable of meeting the challenges of survival in different conditions. Sexual reproduction involves combining specialized cells (gametes) to form offspring that inherit genetic traits from both parents. Each cell has half the chromosomes of the mother and half of the father.

Human sexuality has many aspects. It involves building up personal identity in a social evolution of individuals in a society. Sociocultural aspect casts human sexuality as asocial norm under moral, ethical, philosophical and religious or spiritual framework. Medically, it deals with the physiological or even psychological aspects. Sexuality is also now viewed in the cultural, political, and legal context in a society.

The construction of sexual meanings, is an instrument by which social institutions, religion, the educational system, psychiatry, the legal system, human rights, etc. control and shape relationships. Therefore, sexuality is, generally, framed within the context of the institution of marriage.

A home is an environment that provides nourishment for the growth of young ones and guarantees mutual care and safety for all. It instills a moral obligation and individual responsibility for the partners’ sexual behaviors. In some countries, sex functions, behaviors, and feelings are expressed without any binding relationship among them. Deviant sexual practices are limited by laws in many countries. In some societies, mostly those where religion has a strong influence on social policy, marriage laws serve the purpose of encouraging people to only have sex with one partner within marriage. The underlying factor is that mature individuals engage in actions for which they own the responsibility and work towards a condition where harmony is established in the society.

Laws also ban adults from committing sexual abuse, committing sexual acts with anyone under-aged, performing sexual activities for money (prostitution). Though these laws cover both opposite-sex sexual activities and same-sex, they may differ with regard to punishment.

sperm-and-egg

Pregnancy

In medicine, pregnancy is caused by the merging of the female gamete with the male gamete, in a process referred to as fertilization, or commonly known as conception. Human pregnancy or gestation is generally divided into three trimester period. Human pregnancy averages 266 days (38 weeks) from conception, or 40 weeks from the start of the last menstrual period.

 Week 1

Fertilization:  Cleavage to form a blastocyst 4-5 days after fertilization. More than 100 cells are involved at this stage. Implantation takes place 6-9 days after fertilization.

Week 2

The three basic layers of the embryo development are ectoderm, mesoderm and endoderm. No research allowed on human embryos beyond this stage.

Week 3

Neutral tube develops, along with the beginnings of the brain and spinal cord (first organs). The embryo at this stage is 2 mm in size.

Week 4

Heart, blood vessels, blood and gut start forming. The size of the embryo is about 5 mm at this stage.

Week 5

Brain starts developing along with the limb buds (small swellings which are the beginnings of the arms and legs). Heart is a large tube and starts to beat, pumping blood. This can be seen on an ultrasound scan. The embryo is 8 mm in size.

Week 6

Eyes and ears start to form.

Week 7

All major internal organs start to develop along with the face. Eyes get their color and mouth and tongue are formed. Hand and feet continue to grow and the fetus is now 17 mm long.

By week 12

Fetus fully formed, with all the organs, muscles, bones, toes, fingers and sex organs. Fetus starts moving and for the rest of the gestation period, it is mainly growing in size. Fetus is 56mm long from head to bottom. Pregnancy may be beginning to show.

By week 20

Hair begins to grow, including eyebrows and eye lashes. Fingerprints, fingernails and toenails develop. A firm hand grip develops completely. Between 16 and 20 weeks baby is usually felt moving for first time. Baby is 160 mm long from head to toe.

Week 24

The baby’s eyelids begin to open and the legal limit for abortion in most circumstances.

By week 28

Baby starts moving vigorously. It responds to touch and loud noises. It starts swallowing amniotic fluid and urinating.

By week 30

Usually the baby lays head down ready for birth. It is now 240 mm from head to bottom.

40 weeks

9 months, the baby is born.

Symptoms

Symptoms signify pregnancy. The symptoms include nausea and vomiting, excessive tiredness and fatigue, craving for certain foods not normally considered a favourite and frequent urination particularly during night.

Medical signs associated with pregnancy include the presence of human chronic gonadotropin (HCG) in the blood and urine, implantation bleeding that occurs at implantation of embryo in the uterus during the 3rd or 4th week after last menstrual period, increased basal body temperature sustained for over 2 weeks after ovulation, softening of the uterus isthmus, and darkening of the mid line of the abdomen, caused by hyper pigmentation resulting from hormonal changes, usually appearing around the middle of the pregnancy.

Detection Tests

Pregnancy tests detect hormones generated by the newly formed placenta. Clinical blood and urine tests can detect pregnancy soon after implantation, which is as early as 6 to 8 days after fertilization. Blood pregnancy tests are more accurate than urine tests, which cannot detect pregnancy until at least 12 to 15 days after fertilization.