The reproductive system or genital system is a system of sex organs within anorganism which work together for the purpose of sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system.Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals, which allows for the possibility of greater genetic fitness of theoffspring.
Most other vertebrate animals have generally similar reproductive systems consisting of gonads, ducts, and openings. However, there is a great diversity of physical adaptations as well as reproductive strategies in every group of vertebrates.
Vertebrate animals all share key elements of their reproductive systems. They all have gamete-producing organs or gonads. In females, these gonads are then connected by oviducts to an opening to the outside of the body, typically the cloaca, but sometimes to a unique pore such as a vagina or intromittent organ.
The human reproductive system usually involves internal fertilization by sexual intercourse. During this process, the male inserts his erect penis into thefemale’s vagina and ejaculates semen, which contains sperm. The sperm then travels through the vagina and cervix into the uterus or fallopian tubes for fertilization of the ovum. Upon successful fertilization and implantation,gestation of the fetus then occurs within the female’s uterus for approximately nine months, this process is known as pregnancy in humans. Gestation ends with birth, the process of birth is known as labor. Labor consists of the musclesof the uterus contracting, the cervix dilating, and the baby passing out the vagina (the female genital organ). Human’s babies and children are nearly helpless and require high levels of parental care for many years. One important type of parental care is the use of the mammary glands in the female breasts tonurse the baby.
The female reproductive system has two functions: The first is to produce egg cells, and the second is to protect and nourish the offspring until birth. The male reproductive system has one function, and it is to produce and deposit sperm. Humans have a high level of sexual differentiation. In addition to differences in nearly every reproductive organ, numerous differences typically occur in secondary sexual characteristics.
The male reproductive system is a series of organs located outside of the body and around the pelvic region of a male that contribute towards the reproduction process. The primary direct function of the male reproductive system is to provide the male sperm for fertilization of the ovum.
The major reproductive organs of the male can be grouped into three categories. The first category is sperm production and storage. Production takes place in the testes which are housed in the temperature regulatingscrotum, immature sperm then travel to the epididymis for development and storage. The second category are the ejaculatory fluid producing glands which include the seminal vesicles, prostate, and the vas deferens. The final category are those used for copulation, and deposition of the spermatozoa (sperm) within the male, these include the penis, urethra, vas deferens, and Cowper’s gland.
Major secondary sexual characteristics includes: larger, more muscular stature, deepened voice, facial and body hair, broad shoulders, and development of an adam’s apple. An important sexual hormone of males isandrogen, and particularly testosterone.
The testes release a hormone that controls the development of sperm. This hormone is also responsible for the development of physical characteristics in men such as facial hair and a deep voice.
The human female reproductive system is a series of organs primarily located inside of the body and around the pelvic region of a female that contribute towards the reproductive process. The human female reproductive system contains three main parts: the vulva, which leads to the vagina, the vaginal opening, to the uterus; the uterus, which holds the developing fetus; and theovaries, which produce the female’s ova. The breasts are involved during the parenting stage of reproduction, but in most classifications they are not considered to be part of the female reproductive system.
The vagina meets the outside at the vulva, which also includes the labia, clitorisand urethra; during intercourse this area is lubricated by mucus secreted by theBartholin’s glands. The vagina is attached to the uterus through the cervix, while the uterus is attached to the ovaries via the fallopian tubes. Each ovary contains hundreds of egg cells or ova (singular ovum).
Approximately every 28 days, the pituitary gland releases a hormone that stimulates some of the ova to develop and grow. One ovum is released and it passes through the fallopian tube into the uterus. Hormones produced by the ovaries prepare the uterus to receive the ovum. It sita her and awaits the sperm for fertilization to occur. When this does not occur i.e. no sperm for fertilization, the lining of the uterus, called the endometrium, and unfertilized ova are shed each cycle through the process of menstruation. If the ovum is fertilized by sperm, it attaches to the endometrium and the fetus develops.
Most mammal reproductive systems are similar, however, there are some notable differences between the non-human mammals and humans. For instance, most male mammals have a penis which is stored internally until erect, and most have a penis bone or baculum.Additionally, males of most species do not remain continually sexually fertile as humans do. Like humans, most groups of mammals have descended testicles found within a scrotum, however, others have descended testicles that rest on the ventral body wall, and a few groups of mammals, such as elephants, have undescended testicles found deep within their body cavities near their kidneys.
The reproductive system of marsupials is unique in that the female has two vaginae, both of which open externally through one orifice but lead to different compartments within the uterus; males usually have a two-pronged penis, which corresponds to the females’ two vaginae.Marsupials typically develop their offspring in an external pouch containing teats to which their newborn young (joeys) attach themselves for post uterine development. Also, marsupials have a unique prepenial scrotum. The 15mm (5/8 in) long newborn joey instinctively crawls and wriggles the several inches (15 cm), while clinging to fur, on the way to its mother’s pouch.
The uterus and vagina are unique to mammals with no homologue in birds, reptiles, amphibians, or fish.In place of the uterus the othervertebrate groups have an unmodified oviduct leading directly to a cloaca, which is a shared exit-hole for gametes, urine, and feces. Monotremes (i.e.platypus and echidnas), a group of egg-laying mammals, also lack a uterus and vagina, and in that respect have a reproductive system resembling that of a reptile.
In domestic canines, sexual maturity (puberty) occurs between the ages of 6 to 12 months for both males and females, although this can be delayed until up to two years of age for some large breeds.
The mare’s reproductive system is responsible for controlling gestation, birth, and lactation, as well as her estrous cycle and mating behavior. The stallion’s reproductive system is responsible for his sexual behavior and secondary sex characteristics (such as a large crest).
Male and female birds have a cloaca, an opening through which eggs, sperm, and wastes pass. Intercourse is performed by pressing the lips of the cloacae together, which is sometimes known as intromittent organ which is known as a phallus that is analogous to the mammals’ penis. The female lays amnioticeggs in which the young fetus continues to develop after it leaves the female’s body. Unlike most vertebrates female birds typically have only one functional ovary and oviduct. As a group, birds, like mammals, are noted for their high level of parental care.
Reptiles are almost all sexually dimorphic, and exhibit internal fertilization through the cloaca. Some reptiles lay eggs while others are ovoviviparous (animals that deliver live young). Reproductive organs are found within the cloaca of reptiles. Most male reptiles have copulatory organs, which are usually retracted or inverted and stored inside the body. In turtles and crocodilians, the male has a single median penis-like organ, while male snakes and lizards each possess a pair of penis-like organs.
Most amphibians exhibit external fertilization of eggs, typically within the water, though some amphibians such as caecilians have internal fertilization. All have paired, internal gonads, connected by ducts to the cloaca.
Fish exhibit a wide range of different reproductive strategies. Most fish, however, are oviparous and exhibit external fertilization. In this process, females use their cloaca to release large quantities of their gametes, calledspawn into the water and one or more males release “milt”, a white fluid containing many sperm over the unfertilized eggs. Other species of fish are oviparous and have internal fertilization aided by pelvic or anal fins that are modified into an intromittent organ analogous to the human penis.A small portion of fish species are either viviparous or ovoviviparous, and are collectively known as livebearers.
Invertebrates have an extremely diverse array of reproductive systems, the only commonality may be that they all lay eggs. Also, aside from cephalopods andarthropods, nearly all other invertebrates are hermaphroditic and exhibitexternal fertilization.
All cephalopods are sexually dimorphic and reproduce by laying eggs. Most cephalopods have semi-internal fertilization, in which the male places his gametes inside the female’s mantle cavity or pallial cavity to fertilize the ovafound in the female’s single ovary. Likewise, male cephalopods have only a single testicle. In the female of most cephalopods the nidamental glands aid in development of the egg.
The “penis” in most unshelled male cephalopods (Coleoidea) is a long and muscular end of the gonoduct used to transfer spermatophores to a modified arm called a hectocotylus. That in turn is used to transfer the spermatophores to the female. In species where the hectocotylus is missing, the “penis” is long and able to extend beyond the mantle cavity and transfer the spermatophores directly to the female.
Most insects reproduce oviparously, i.e. by laying eggs. The eggs are produced by the female in a pair of ovaries. Sperm, produced by the male in one testis or more commonly two, is transmitted to the female during mating by means of external genitalia. The sperm is stored within the female in one or morespermathecae. At the time of fertilization, the eggs travel along oviducts to be fertilized by the sperm and are then expelled from the body (“laid”), in most cases via an ovipositor.
Arachnids may have one or two gonads, which are located in the abdomen. The genital opening is usually located on the underside of the second abdominal segment. In most species, the male transfers sperm to the female in a package, or spermatophore. Complex courtship rituals have evolved in many arachnids to ensure the safe delivery of the sperm to the female.
Among all living organisms, flowers, which are the reproductive structures ofangiosperms, are the most varied physically and show a correspondingly great diversity in methods of reproduction.Plants that are not flowering plants (green algae, mosses, liverworts, hornworts, ferns and gymnosperms such asconifers) also have complex interplays between morphological adaptation and environmental factors in their sexual reproduction. The breeding system, or how the sperm from one plant fertilizes the ovum of another, depends on the reproductive morphology, and is the single most important determinant of the genetic structure of nonclonal plant populations. Christian Konrad Sprengel(1793) studied the reproduction of flowering plants and for the first time it was understood that the pollination process involved both biotic and abioticinteractions.
Fungal reproduction is complex, reflecting the differences in lifestyles and genetic makeup within this diverse kingdom of organisms.It is estimated that a third of all fungi reproduce using more than one method of propagation; for example, reproduction may occur in two well-differentiated stages within the life cycle of a species, the teleomorph and the anamorph.Environmental conditions trigger genetically determined developmental states that lead to the creation of specialized structures for sexual or asexual reproduction. These structures aid reproduction by efficiently dispersing spores or spore-containingpropagules.
Reproductive System: Facts, Functions & Diseases
The reproductive system is a collection of internal and external organs — in both males and females — that work together for the purpose of procreating, according to theCleveland Clinic. Due to its vital role in the survival of the species, many scientists argue that the reproductive system is among the most important systems in the entire body.
How reproductive systems work
The male reproductive system consists of two major parts: the testes, where sperm are produced, and the penis, according toMerck Manuals. The penis and urethra belong to both the urinary and reproductive systems in males. The testes are carried in an external pouch known as the scrotum, where they normally remain slightly cooler than body temperature to facilitate sperm production.
The external structures of the female reproductive system include the clitoris, labia minora, labia majora and Bartholin’s glands, according to the Cleveland Clinic. The major internal organs of the female reproductive system include the vagina and uterus — 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 fallopian tubes connect the uterus to the ovaries. In response to hormonal changes, one ovum, or egg — or more in the case of multiple births — is released and sent down the fallopian tube during ovulation. If not fertilized, this egg is eliminated during menstruation.
Fertilization occurs if a sperm enters the fallopian tube and burrows into the egg. While the fertilization usually occurs in the oviducts, it can also happen in the uterus itself. The egg then becomes implanted in the lining of the uterus, where it begins the processes of embryogenesis (in which the embryo forms) and morphogenesis (in which the fetus begins to take shape). When the fetus is mature enough to survive outside of the womb, the cervix dilates, and contractions of the uterus propel it through the birth canal.
Variations in the reproductive system
Around 49.5 percent of the world’s population is female, so there are slightly more men on the planet than women, according to World Bank. A person’s sex is determined by what reproductive system the person has, but it isn’t always so simple. Some humans are born with parts of both male and female reproductive systems or incomplete reproductive organs of one sex or the other. Those with both male and female reproductive parts are considered intersex. Sometimes children are labeled as male or female, depending on how complete or functional one sexual reproductive system is over the other. Then, the other organs are removed.
Today, many parents are opting to leave both sets of reproductive organs intact with the intent of letting the child decide to keep or remove the various parts when they are older. A baby is born atypical genitalia in one in about 1,500 to 2,000 births, according to Intersex Society of North America.
Females that are born without all of their reproductive system are labeled as having Mayer Rokitansky Kuster Hauser Syndrome. This occurs in one in 5,000 female births, according to the Center for Young Women’s Health.
Diseases of the female reproductive system
Many parts of the male and female reproductive systems can be affected by cancer. In females, cancer can attack the uterus, ovaries, breast and cervix, among other organs, according to the American Cancer Society.
Many experts have seen what they refer to as the “Angelina Jolie” effect, where women are taking proactive measures by having breasts and internal reproductive organs removed if they have a family history of cancer before there are signs of the disease. “With better genetic testing and screening, we have seen a number of women who are being more proactive about their reproductive health,” said Dr. Shana Wingo, who specializes on gynecologic oncology at Arizona Oncology.
Ovarian cancer tends to have a poorer outcome than other gynecological cancers, Ross noted, because it is not typically diagnosed until it has progressed significantly. “There is no standard screening available for ovarian cancer, so it is very difficult to identify it early.”
Tests to detect ovarian cancer, as well as cancer of the fallopian tube, and primary peritoneal cancer are currently being studied, according to the National Cancer Institute.
There are two tests used to screen for cervical cancer. The Pap test screens for cellular changes in the cervix called cytology, while the genital human papillomavirus (HPV) test identifies the presence of infection with high-risk HPV, the strains that are linked to cervical cancer, according to Dr. Charles Dubin, an OB/GYN in Santa Monica, Calif.
A recent study published by Cancer Cytopathology, found that HPV-only screening misses more cervical cancer in women than Pap-only or co-testing, based on approximately 8.6 million women ages 30 to 65. There is approximately a three-fold improvement in the cancer detection rate of co-testing compared to HPV only.
Current guidelines recommend that women first start getting the Pap test alone when they turn 21 and repeat every three years if the test is normal until age 30. A Pap-plus-HPV test, or co-testing, is recommended for women ages 30 to 65, and if both are negative repeated every five years, regardless of whether they have received HPV vaccination. “However, there is compelling scientific evidence that co-testing every three years misses less cases of cancer and pre-cancer than every five-year co-testing,” Dubin noted.
While genital HPV is typically associated with females, it is the most common sexually transmitted infection. The majority of sexually active people in the United States — male and female — will have HPV at some time in their lives, but most will not experience any symptoms. In a small portion of women, it can result in cervical cancer and genital warts; in men, it can cause penile and anal cancer and genital warts, according to the NIH.
Both genders can develop sexually transmitted diseases, including genital herpes, gonorrhea and syphilis, according to the National Institutes of Health (NIH). HIV/AIDS, a disease of the immune system, is not exclusively transmitted through sexual contact; sexual activity is one of the ways that the HIV virus is spread.
For females, severe menstrual cramping, or dysmenorrheal, is the most common disease of the reproductive system occurs with a woman’s monthly menstrual period, according to Dr. Sheryl Ross, OB/GYN and Women’s Health Specialist atProvidence Saint John’s Health Center.
“Severe pain before or during your period can last anywhere from one to seven days and disrupt your normal day-to-day routines at school, work and socially,” Ross noted. Diagnosis is made by the patient’s medical history and a pelvic exam. The best treatment includes medications that block the effects of prostaglandins and include ibuprofen and naproxen. The birth control pill also works well in treating dysmenorrhea by decreasing the blood flow, Ross noted.
Another common disorder of the female reproductive system is a vaginal yeast infection, which is caused by a yeast fungus in the vagina. Most can be successfully treated with over-the-counter medications, according to WebMD.
Endometriosis is a condition where that normally lines the inside of your uterus — the endometrium — ends up outside of uterus, most commonly in the ovaries, bowel or the tissue lining your pelvis. The endometrial tissue becomes trapped, causing pain, according to the Mayo Clinic.
Pelvic inflammatory disease can involve an infection of any of the female reproductive organs, including the uterus and ovaries. Sexually transmitted diseases, such as gonorrhea and chlamydia, are typical causes of pelvic inflammatory disease, according to the NIH. “Any of these STIs can cause serious and potentially long term reproductive problems that include chronic pelvic pain and infertility,” Ross said.
Diseases of the male reproductive system
Of male-specific diseases of the reproductive system, prostate cancer is the most common, but men can also suffer from testicular and penile cancer, according to the American Cancer Society.
Treatment for prostate cancer depends on the age, severity of the disease and other health conditions of the patient. The usual treatments for prostate cancer are surgery, radiation therapy, watchful waiting, and hormonal treatment, according to the Cleveland Clinic.
Erectile dysfunction is a common condition that affects about one in 10 males on a long-term basis, the Cleveland Clinic noted. It can be linked to vascular disease, neurological disorders such as Multiple Sclerosis, trauma and psychological episodes.
Prostatitis typically involves swelling or inflammation of the prostate gland, according to the Mayo Clinic, and can cause painful or difficult urination and ejaculation. Nearly half of all men experience symptoms of prostatitis at some point during their lives.
Defining and treating infertility
Infertility is defined as a couple’s inability to conceive after one year of unprotected intercourse. It can be caused by a condition in one partner or a combination of circumstances, according to the Mayo Clinic.
In males, infertility is a condition in which they produce no sperm cells (azoospermia) or too few sperm cells (oligospermia), or their sperm cells are abnormal or die before they can reach the egg. Causes range from chromosomal defects to hormonal imbalance to tumors. Lifestyle factors, such as drug and alcohol use, can also play role. In rare cases, infertility in men is caused by an inherited condition, such as cystic fibrosis, according to the Mayo Clinic.
In women, infertility is defined as a disorder of the reproductive system that hinders the body’s ability to ovulate, conceive, or carry an infant to term.
Reproductive conditions are treated by a variety of specialists. In women, many issues are treated by obstetricians/gynecologists and for males, urologists handle many disorders of their reproductive systems. There are also infertility experts that treat couples who are unable to conceive and endocrinologists who treat hormonal disorders.