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What you need to know about pregnancy and conception?

Human sexual reproduction involves the merging of the parent sex cells or gametes.  The male spermatozoa and the female egg or ova are the gametes.  When these gametes fuse together fertilization occurs and a new cell is formed which is called a zygote.  The zygote divides over and over until it develops into a fetus whose genetic information is different from his/her parents.

Gametes are made by a process called meiosis.  In the human male the male gametes are made in the testis whereas the human female is born with all the gametes or eggs she will ever have, which are approximately half a million eggs.

Gametes are made from cells in the body.  These cells contain 46 chromosomes.  Division by meiosis creates a new cell called a haploid cell.  This cell contains 23 chromosomes or half the number of chromosomes from the parent cell.

Male Reproductive System

As stated earlier the male reproductive organ that is responsible for producing spermatozoa or sperms is the testes or gonads.  This organ is situated outside the abdominal cavity in a sac of skin called the scrotum.  This is so because sperm production requires a temperature 2-4 F or 2-3 C below normal body temperature.

Each testis is made up of a seminiferous tubule and this is where sperms are made through a process called spermatogenesis.  There are cells between the seminiferous tubules called interstitial cells which produce the male sex hormone testosterone.

Sperms are collected by the vasa efferentia and then deposited in the epididymis where it is stored.

What you need to know about pregnancy and conception?

Female Reproductive System

The female reproductive system is internal with the exception of the vulva which is on the outside.  The ovaries are the female gonads and they are responsible for the release of the female gametes also known as eggs or ova.  Another function of the ovaries is the secretion of the female sex hormones estrogen and progesterone.

One egg is released every month by one of the two ovaries.  When the egg is released from the ovary ovulation is said to have occurred.  Ovulation occurs two weeks after a woman’s last menstruation. Ovulation can be determined by the use of ovulation monitor kits.

Once released the egg travels in the fallopian tube (also known as the oviduct or uterine tube).  Since eggs are not motile as sperms are, movement in the fallopian tube is facilitated by the cilia lining.    A peristaltic movement pushes the egg forward until it reaches the uterus.  An egg is viable for about 18-24 hours after which it dies.

Coitus/Sexual Intercourse

When the male is aroused, blood fills the spongy erectile tissue in his penis which becomes erect.  The erect penis can now be inserted into the vagina.  Through friction and the rhythmic movement of coitus a climax is reached by both sexes called an orgasm.  Fluid is ejaculated from the tip of the male’s penis called semen.  Semen is made of a mixture of approximately 300-500 million sperms and seminal fluids.  This is deposited in the vagina close to the cervix.  It should be note that only a few thousand sperms survive the journey from the vagina to the egg.  Also, sperms are viable for approximately 48 hours in the female.

The sperms then travel through the cervix and uterus to the fallopian tube.  If a viable egg is present fertilization occurs.  If not, the egg together with the corpus luteum will degenerate.  Additionally, the endometrium breaks down causing menstrual bleeding or a period.  Menstrual bleeding can last for about five days after which the cycle repeats itself.  The approximate time for a menstrual cycle is 28 days.

Fertilization/Implantation

Fertilization takes place when a viable sperm penetrates a viable egg.  The fusion of the male and female haploid cell creates a new cell called a diploid cell or zygote.  As soon as the zygote is formed, the egg membrane becomes impenetrable so as to prevent further entry of sperms.

The zygote continues to grow and it develops into a ball of cells called the blastocyst or embryo.  About 8-10 days after ovulation the blastocyst implants itself into the soft lining of the uterus.  The outer lining of the blastocyst termed the trophoblast secretes a hormone called human Chorionic Gonadotrophin (hCG).  hCG prevents the corpus luteum from breaking down therefore the corpus luteum continues to release estrogen and progesterone which in turn prevents the endometrium from degenerating.

Once these events are set in motion menstrual bleeding or the period would cease and this is an early indication of pregnancy.  hCG is present in the blood stream and urine at the time of conception and detection of this hormone forms the basis of a pregnancy test.

By the time pregnancy is discovered a mother to be could be about 3-5 weeks along.