Human reproduction
Encyclopedia
Human reproduction is any form of sexual reproduction
resulting in the conception of a child
, typically involving sexual intercourse
between a man and a woman. During intercourse, the interaction between the male
and female reproductive systems
results in fertilization of the woman's ovum
by the man's sperm
, which after a gestation period
is followed by childbirth
. The fertilization of the ovum may nowadays be achieved by artificial insemination
methods, which do not involve sexual intercourse.
where sperm are produced, and the penis
. In humans, both of these organs are outside the abdominal cavity
. Having the testes outside the abdomen facilitates temperature regulation of the sperm, which require specific temperatures to survive about 2-3 °C less than the normal body temperature i.e. 37°C. If the testicles remain too close to the body, it is likely that the increase in temperature will harm the spermatozoa formation, making conception more difficult. This is why the testes are carried in an external pouch viz. scrotum rather than within the abdomen; they normally remain slightly cooler than body temperature, facilitating sperm production.
, which act as the receptacle for semen, and the ovaries
, which produce the female's ova. The vagina is attached to the uterus through the cervix
, while the uterus is attached to the ovaries via the Fallopian tube
s. At certain intervals, the ovaries release an ovum, which passes through the fallopian tube into the uterus.
The fertilization of the ovum with the sperm occurs at the ampullary-isthimic junction only that is why not all the intercourses result in pregnancy. The ovum meets with Spermatozoon
, a sperm may penetrate and merge with the egg, fertilizing it with the help of certain hydrolytic enzymes present in the acrosome . The fertilization usually occurs in the oviduct
s, but can happen in the uterus itself. The zygote
then becomes implanted in the wall of the uterus, where it begins the processes of embryogenesis
and morphogenesis
. When the fetus
is developed enough to survive outside the womb, the cervix dilates and contractions of the uterus propel it through the birth canal, which is the vagina.
The ova, which are the female sex cells, are much larger than the spermatozoon and are normally formed within the ovaries of the female fetus before its birth. They are mostly fixed in location with in the ovary until their transit to the uterus, and contain nutrients for the later zygote
and embryo
. Over a regular interval, in response to hormonal signals, a process of oogenesis
matures one ovum which is released and sent down the Fallopian tube. If not fertilized, this egg is flushed out of the system through menstruation
.
by sexual intercourse. During this process, the erect
penis of the male is inserted into the female's vagina until the male ejaculates semen, which contains sperm. This process is also known as "coitus", "mating" or "having sex". The sperm travels through the vagina and cervix into the uterus or Fallopian tubes for fertilization of the ovum. Upon fertilization
and implantation, gestation of the fetus then occurs within the female's uterus.
inside the female. During this time, the fetus receives all of its nutrition
and oxygenated blood from the female, filtered through the placenta
, which is attached to the fetus' abdomen
via an umbilical cord
. This drain of nutrient
s can be quite taxing on the female, who is required to ingest slightly higher levels of calorie
s. In addition, certain vitamin
s and other nutrients are required in greater quantities than normal, often creating abnormal eating habits. Gestation period is about 266 days in humans.
in humans, should typically begin respiration
on its own shortly after birth. Not long after, the placenta is passed as well. The end of the umbilical cord attached to the child's abdomen eventually falls off on its own.The mid-wife or nurse assisting the birth will usually detach the mother from the baby using a clamp, then cutting it off.
- feeding the baby milk from the mother's mammary gland
s in her breast
s.
promotes reproduction, while anti-natalism promotes birth control
as a solution to overpopulation
and its effects.
Sexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...
resulting in the conception of a child
Fertilisation
Fertilisation is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo...
, typically involving sexual intercourse
Sexual intercourse
Sexual intercourse, also known as copulation or coitus, commonly refers to the act in which a male's penis enters a female's vagina for the purposes of sexual pleasure or reproduction. The entities may be of opposite sexes, or they may be hermaphroditic, as is the case with snails...
between a man and a woman. During intercourse, the interaction between the male
Male reproductive system (human)
The human male reproductive system consists of a number of sex organs that are a part of the human reproductive process...
and female reproductive systems
Female reproductive system (human)
The female reproductive system contains two main parts: the uterus, which hosts the developing fetus, produces vaginal and uterine secretions, and passes the anatomically male person's sperm through to the fallopian tubes; and the ovaries, which produce the anatomically female person's egg cells...
results in fertilization of the woman's ovum
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
by the man's sperm
Sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
, which after a gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
is followed by childbirth
Childbirth
Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...
. The fertilization of the ovum may nowadays be achieved by artificial insemination
Artificial insemination
Artificial insemination, or AI, is the process by which sperm is placed into the reproductive tract of a female for the purpose of impregnating the female by using means other than sexual intercourse or natural insemination...
methods, which do not involve sexual intercourse.
The human male
The male reproductive system contains two main divisions: the testesTesticle
The testicle is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system...
where sperm are produced, and the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
. In humans, both of these organs are outside the abdominal cavity
Abdominal cavity
The abdominal cavity is the body cavity of the human body that holds the bulk of the viscera. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roof is the thoracic diaphragm , and its oblique floor is the pelvic inlet...
. Having the testes outside the abdomen facilitates temperature regulation of the sperm, which require specific temperatures to survive about 2-3 °C less than the normal body temperature i.e. 37°C. If the testicles remain too close to the body, it is likely that the increase in temperature will harm the spermatozoa formation, making conception more difficult. This is why the testes are carried in an external pouch viz. scrotum rather than within the abdomen; they normally remain slightly cooler than body temperature, facilitating sperm production.
The human female
The female reproductive system likewise contains two main divisions: the vagina and uterusUterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
, which act as the receptacle for semen, and the ovaries
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
, which produce the female's ova. The vagina is attached to the uterus through the cervix
Cervix
The cervix is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall...
, while the uterus is attached to the ovaries via the Fallopian tube
Fallopian tube
The Fallopian tubes, also known as oviducts, uterine tubes, and salpinges are two very fine tubes lined with ciliated epithelia, leading from the ovaries of female mammals into the uterus, via the utero-tubal junction...
s. At certain intervals, the ovaries release an ovum, which passes through the fallopian tube into the uterus.
The fertilization of the ovum with the sperm occurs at the ampullary-isthimic junction only that is why not all the intercourses result in pregnancy. The ovum meets with Spermatozoon
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...
, a sperm may penetrate and merge with the egg, fertilizing it with the help of certain hydrolytic enzymes present in the acrosome . The fertilization usually occurs in the oviduct
Oviduct
In non-mammalian vertebrates, the passageway from the ovaries to the outside of the body is known as the oviduct. The eggs travel along the oviduct. These eggs will either be fertilized by sperm to become a zygote, or will degenerate in the body...
s, but can happen in the uterus itself. The zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...
then becomes implanted in the wall of the uterus, where it begins the processes of embryogenesis
Embryogenesis
Embryogenesis is the process by which the embryo is formed and develops, until it develops into a fetus.Embryogenesis starts with the fertilization of the ovum by sperm. The fertilized ovum is referred to as a zygote...
and morphogenesis
Morphogenesis
Morphogenesis , is the biological process that causes an organism to develop its shape...
. When the fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
is developed enough to survive outside the womb, the cervix dilates and contractions of the uterus propel it through the birth canal, which is the vagina.
The ova, which are the female sex cells, are much larger than the spermatozoon and are normally formed within the ovaries of the female fetus before its birth. They are mostly fixed in location with in the ovary until their transit to the uterus, and contain nutrients for the later zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...
and embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
. Over a regular interval, in response to hormonal signals, a process of oogenesis
Oogenesis
Oogenesis, ovogenesis or oögenesis is the creation of an ovum . It is the female form of gametogenesis. The male equivalent is spermatogenesis...
matures one ovum which is released and sent down the Fallopian tube. If not fertilized, this egg is flushed out of the system through menstruation
Menstrual cycle
The menstrual cycle is the scientific term for the physiological changes that can occur in fertile women for the purpose of sexual reproduction. This article focuses on the human menstrual cycle....
.
Process
Human reproduction begins with sexual intercourse, followed by nine months of pregnancy before childbirth. Many years of parental care is required before a human child becomes independent.Sexual intercourse
Human reproduction takes place as internal fertilizationInternal fertilization
In mammals, internal fertilization is done through copulation, which involves the insertion of the penis into the vagina. Some other higher vertebrate animals reproduce internally, but their fertilization is cloacal.The union of spermatozoa of the parent organism. At some point, the growing egg or...
by sexual intercourse. During this process, the erect
Erection
Penile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal...
penis of the male is inserted into the female's vagina until the male ejaculates semen, which contains sperm. This process is also known as "coitus", "mating" or "having sex". The sperm travels through the vagina and cervix into the uterus or Fallopian tubes for fertilization of the ovum. Upon fertilization
Human fertilization
Human fertilization is the union of a humanoid egg and sperm, usually occurring in the ampulla of the uterine tube. The result of this union is the production of a zygote, or fertilized egg, initiating prenatal development...
and implantation, gestation of the fetus then occurs within the female's uterus.
Pregnancy
Pregnancy is the period of time during which the fetus develops, dividing via mitosisMitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
inside the female. During this time, the fetus receives all of its nutrition
Nutrition
Nutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with a healthy diet....
and oxygenated blood from the female, filtered through the placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
, which is attached to the fetus' abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
via an umbilical cord
Umbilical cord
In placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta...
. This drain of nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
s can be quite taxing on the female, who is required to ingest slightly higher levels of calorie
Calorie
The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule...
s. In addition, certain vitamin
Vitamin
A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
s and other nutrients are required in greater quantities than normal, often creating abnormal eating habits. Gestation period is about 266 days in humans.
Birth
Once the fetus is sufficiently developed, chemical signals start the process of birth, which begins with the fetus squeezing through the vagina, and eventually out of the mother. The newborn, which is called an infantInfant
A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...
in humans, should typically begin respiration
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
on its own shortly after birth. Not long after, the placenta is passed as well. The end of the umbilical cord attached to the child's abdomen eventually falls off on its own.The mid-wife or nurse assisting the birth will usually detach the mother from the baby using a clamp, then cutting it off.
Parental care
Human babies are nearly helpless and require high levels of parental care for many years. One important type of parental care is nursingLactation
Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, however it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing...
- feeding the baby milk from the mother's mammary gland
Mammary gland
A mammary gland is an organ in mammals that produces milk to feed young offspring. Mammals get their name from the word "mammary". In ruminants such as cows, goats, and deer, the mammary glands are contained in their udders...
s in her breast
Breast
The breast is the upper ventral region of the torso of a primate, in left and right sides, which in a female contains the mammary gland that secretes milk used to feed infants.Both men and women develop breasts from the same embryological tissues...
s.
Political and social
There are groups promoting more human reproduction and those who think reproduction ought to be limited. NatalismNatalism
Natalism is a belief that promotes human reproduction. The term is taken from the Latin adjective form for "birth", natalis. Natalism promotes child-bearing and glorifies parenthood...
promotes reproduction, while anti-natalism promotes birth control
Birth control
Birth control is an umbrella term for several techniques and methods used to prevent fertilization or to interrupt pregnancy at various stages. Birth control techniques and methods include contraception , contragestion and abortion...
as a solution to overpopulation
Overpopulation
Overpopulation is a condition where an organism's numbers exceed the carrying capacity of its habitat. The term often refers to the relationship between the human population and its environment, the Earth...
and its effects.