Post by misspsychotaku on Dec 12, 2015 10:10:50 GMT
*Human cells come in a variety of shapes and sizes, and carry out a wide range of different functions. But the largest and smallest cells in the human body are both gametes, or reproductive cells.
Males produce the smallest human cell — the sperm, which is only 5 micrometers by 3 micrometers in size, not including the sperm's "tail." By comparison, the red blood cell is about 8 micrometers in diameter, or about a tenth of the diameter of a human hair.
A female's ovum, or egg, is the largest human cell, coming in at about 120 micrometers in diameter.
*A huge difference exists between the number of gametes men and women produce. At birth, women have 1 million to 2 million eggs, but only about 300,000 eggs will be left by the time puberty hits, according to WebMD. Only 300 to 400 of these eggs will be ovulated before menopause.
Each man, on the other hand, produces more than 500 billion sperm cells in his lifetime. During ejaculation, a healthy man can release upward of about 1.2 million sperm cells — that's more gametes released in a single moment than some woman ever have.
*You might think contraception is a new invention, but birth control may have gotten its start nearly 4,000 years ago, according to a 2011 article in the Journal of Family Planning and Reproductive Health Care.
The earliest written record of contraception comes from the Egyptian Kahun Gynaecological Papyrus, which dates back to 1825 B.C. One birth control method mentioned in the document required a doctor to apply honey to the inside of the vagina while the woman lay on a bed of sodium carbonate.
Another contraceptive technique involved crocodile dung, which may have been packed against the cervix or burned as an incense (the text is unclear on the manure's exact use).
*Until the late 17th century and early 18th century, physicians held to the "one-sex" reproductive model of thinking, which was championed by Greek physician Galen of Pergamon almost 2,000 years ago. Though people noticed the obvious physical differences between the sexes, they viewed the male and female reproductive organs as being homologous counterparts to one another.
In Galen's view, for example, women's reproductive parts mirrored men's reproductive parts: The vagina is a female's inverted penis, the labia is her foreskin, the uterus is her scrotum and the ovaries are her testes.
In fact, the terms to describe the female reproductive organs, including vagina, uterus and ovaries, didn't emerge until at least the 17th century. (Before that time, male terms were used to describe both male and female parts.)
*The internal body systems of animals are often similar to ours, but there's a remarkable variation in reproductive systems in the animal kingdom.
For example, female kangaroos have three vaginas. The two lateral vaginas are used for accepting sperm during mating, and the central vagina is used for birthing. Male kangaroos have a two-pronged penis to inseminate the lateral vaginas.
Most birds, on the other hand, don't have penises or vaginas. Both sexes have what's called a cloaca — it's a single orifice used for waste and reproduction.
*During normal fetal development, the uterus starts off as two small tubes, which then join to create a single, hollow organ (the womb). But sometimes the tubes don't join completely, and instead develop into two separate structures, according to the Mayo Clinic. This condition is called uterus didelphys, or double uterus, and it reportedly affects about 1 in 2,000 women worldwide.
Remarkably, the two uteruses can both function normally. In 2011, a 24-year-old woman named Andreea Barbosa gave birth to twins, who each developed in their own private womb.
*Men with low-pitched voices are often thought of as being more "masculine," but research shows that these men don't necessarily have the best sperm.
In 2012, scientists looked at how the pitch of a man's voice is associated with his semen quality and women's perceptions of his virility. Though women found deeper voices more masculine and attractive, these low-pitched men had lower ejaculate sperm concentrations than their higher-pitched competition.
source: www.livescience.com/44076-reproductive-system-surprising-facts.html
note: just copied what surprised me...
Males produce the smallest human cell — the sperm, which is only 5 micrometers by 3 micrometers in size, not including the sperm's "tail." By comparison, the red blood cell is about 8 micrometers in diameter, or about a tenth of the diameter of a human hair.
A female's ovum, or egg, is the largest human cell, coming in at about 120 micrometers in diameter.
*A huge difference exists between the number of gametes men and women produce. At birth, women have 1 million to 2 million eggs, but only about 300,000 eggs will be left by the time puberty hits, according to WebMD. Only 300 to 400 of these eggs will be ovulated before menopause.
Each man, on the other hand, produces more than 500 billion sperm cells in his lifetime. During ejaculation, a healthy man can release upward of about 1.2 million sperm cells — that's more gametes released in a single moment than some woman ever have.
*You might think contraception is a new invention, but birth control may have gotten its start nearly 4,000 years ago, according to a 2011 article in the Journal of Family Planning and Reproductive Health Care.
The earliest written record of contraception comes from the Egyptian Kahun Gynaecological Papyrus, which dates back to 1825 B.C. One birth control method mentioned in the document required a doctor to apply honey to the inside of the vagina while the woman lay on a bed of sodium carbonate.
Another contraceptive technique involved crocodile dung, which may have been packed against the cervix or burned as an incense (the text is unclear on the manure's exact use).
*Until the late 17th century and early 18th century, physicians held to the "one-sex" reproductive model of thinking, which was championed by Greek physician Galen of Pergamon almost 2,000 years ago. Though people noticed the obvious physical differences between the sexes, they viewed the male and female reproductive organs as being homologous counterparts to one another.
In Galen's view, for example, women's reproductive parts mirrored men's reproductive parts: The vagina is a female's inverted penis, the labia is her foreskin, the uterus is her scrotum and the ovaries are her testes.
In fact, the terms to describe the female reproductive organs, including vagina, uterus and ovaries, didn't emerge until at least the 17th century. (Before that time, male terms were used to describe both male and female parts.)
*The internal body systems of animals are often similar to ours, but there's a remarkable variation in reproductive systems in the animal kingdom.
For example, female kangaroos have three vaginas. The two lateral vaginas are used for accepting sperm during mating, and the central vagina is used for birthing. Male kangaroos have a two-pronged penis to inseminate the lateral vaginas.
Most birds, on the other hand, don't have penises or vaginas. Both sexes have what's called a cloaca — it's a single orifice used for waste and reproduction.
*During normal fetal development, the uterus starts off as two small tubes, which then join to create a single, hollow organ (the womb). But sometimes the tubes don't join completely, and instead develop into two separate structures, according to the Mayo Clinic. This condition is called uterus didelphys, or double uterus, and it reportedly affects about 1 in 2,000 women worldwide.
Remarkably, the two uteruses can both function normally. In 2011, a 24-year-old woman named Andreea Barbosa gave birth to twins, who each developed in their own private womb.
*Men with low-pitched voices are often thought of as being more "masculine," but research shows that these men don't necessarily have the best sperm.
In 2012, scientists looked at how the pitch of a man's voice is associated with his semen quality and women's perceptions of his virility. Though women found deeper voices more masculine and attractive, these low-pitched men had lower ejaculate sperm concentrations than their higher-pitched competition.
source: www.livescience.com/44076-reproductive-system-surprising-facts.html
note: just copied what surprised me...