Some causes of the high fertility of the population of developing countries. Selected papers and summaries: New York, UN,
Transcript Ovulation is the release of an egg from one of the ovaries. It often happens about midway through the menstrual cycle, although the exact timing may vary. In preparation for ovulation, the lining of the uterus, or endometrium, thickens. The pituitary gland in the brain stimulates one of the ovaries to release an egg.
The wall of the ovarian follicle ruptures at the surface of the ovary. The egg is released. Finger-like structures called fimbriae sweep the egg into the neighboring fallopian tube. The egg travels through the fallopian tube, propelled in part by contractions in the fallopian tube walls.
Here in the fallopian tube, the egg may be fertilized by a sperm. If the egg is fertilized, the egg and sperm unite to form a one-celled entity called a zygote. As the zygote travels down the fallopian tube toward the uterus, it begins dividing rapidly to form a cluster of cells called a blastocyst, which resembles a tiny raspberry.
When the blastocyst reaches the uterus, it implants in the lining of the uterus and pregnancy begins. About two weeks later, the lining of the uterus sheds through the vagina.
This is known as menstruation. Male reproductive system Male reproductive system The male reproductive system makes, stores and moves sperm.
Fluid from the seminal vesicles and prostate gland combine with sperm to make semen. The penis ejaculates semen during sexual intercourse. Fertilization and implantation Fertilization and implantation During fertilization, the sperm and egg unite in one of the fallopian tubes to form a zygote.
Then the zygote travels down the fallopian tube, where it becomes a morula. Once it reaches the uterus, the morula becomes a blastocyst. The blastocyst then burrows into the uterine lining — a process called implantation.
Female reproductive system Female reproductive system The ovaries, fallopian tubes, uterus, cervix and vagina vaginal canal make up the female reproductive system. All of the steps during ovulation and fertilization need to happen correctly in order to get pregnant.
Sometimes the issues that cause infertility in couples are present at birth, and sometimes they develop later in life. Infertility causes can affect one or both partners. In about one-third of cases, there is an issue with the male.
In about one-third of cases, there is an issue with the female. In the remaining cases, there are issues with both the male and female, or no cause can be identified. Causes of male infertility These may include: Abnormal sperm production or function due to undescended testicles, genetic defects, health problems such as diabetes or infections such as chlamydia, gonorrhea, mumps or HIV.
Enlarged veins in the testes varicocele can also affect the quality of sperm.
Problems with the delivery of sperm due to sexual problems, such as premature ejaculation; certain genetic diseases, such as cystic fibrosis; structural problems, such as a blockage in the testicle; or damage or injury to the reproductive organs. Overexposure to certain environmental factors, such as pesticides and other chemicals, and radiation.
Cigarette smoking, alcohol, marijuana or taking certain medications, such as select antibiotics, antihypertensives, anabolic steroids or others, can also affect fertility.
Frequent exposure to heat, such as in saunas or hot tubs, can raise the core body temperature and may affect sperm production.
Damage related to cancer and its treatment, including radiation or chemotherapy. Treatment for cancer can impair sperm production, sometimes severely. Causes of female infertility Causes of female infertility may include: Ovulation disorders, which affect the release of eggs from the ovaries.
These include hormonal disorders such as polycystic ovary syndrome.By definition replacement is only considered to have occurred when the offspring reach 15 years of age. The replacement fertility rate is roughly live births per woman for most industrialised countries.
Due to increased mortality rates, the approximate average for developing regions of the world is Potential causes of anovulation include the following.
Polycystic ovary syndrome (PCOS). PCOS is a condition that causes women to not ovulate, or to ovulate irregularly. Some women with PCOS have elevated levels of testosterone, which can cause acne and excess hair growth. PCOS is the most common cause of female infertility.
Examines the interrelations between European government policies and demographic trends and behaviour, and assesses which policies can prevent or mitigate the adverse consequences of current low fertility and population ageing.
The Demographic Republic of Congo has a total fertility rate of and doctors per people. Availability of contraceptives for couples with knowledge and desire to use it e.g. Rwanda, where 10% of women practice modern methods of family planning and where the total fertility rate is Some Causes of Fertility Rate Movements - 5 - Table 1 shows the fertility rate for several countries of the world and changes from the period to It can be observed that while some countries maintain high fertility rates (like Nigeria at or Pakistan at ); Italy and Germany have fertility rates of and respectively.
Some Causes of Fertility Rate Movements - 5 - Table 1 shows the fertility rate for several countries of the world and changes from the period to It can be observed that while some countries maintain high fertility rates (like Nigeria at or Pakistan at ); Italy and Germany have fertility rates of and respectively.