The Anatomy of the Fallopian Tubes
The fallopian tubes carry eggs from the ovaries to the uterus
Medically reviewed by Keri Peterson, MD
The fallopian tubes transport eggs from the ovaries to the uterus. They are important parts of the female reproductive system. Fertilization normally happens in the fallopian tubes.
The fallopian tubes are also known as oviducts or uterine tubes. Medical procedures that block the fallopian tubes can be used as a form of permanent contraception, or sterilization.
Anatomy
The fallopian tubes are muscular tubes that sit in the lower abdomen/pelvis, alongside the other reproductive organs. There are two tubes, one on each side, that extend from near the top of the uterus, run laterally and then curve over and around the ovaries. Their shape is similar to an extended J.
The open ends of the fallopian tubes lie very near the ovaries but they are not directly attached. Instead, the fimbriae (Latin for fringe) of the fallopian tubes sweep ovulated eggs into the tubes and towards the uterus.
Takeaway
Contrary to many drawings, while the fallopian tubes are both attached to the uterus, they are not directly attached to the ovaries. They are instead connected by a piece of tissue called the mesosalpinx.
In an adult, the fallopian tubes are around 10 to 12 centimeters (cm) long, although this can vary substantially from person to person. They are generally considered to consist of four sections:
Interstitial section, which connects through the wall of the uterus to the interior of the uterus
Isthmus, a narrow section that is about one-third of the length of the tube
Ampulla, which is thin-walled like the isthmus and makes up about half the length of the tube
Infundibulum, where the tube broadens into a fringed funnel that lies near the ovary. The fringes are known as the fimbriae and are sometimes considered a fifth segment. The longest fimbria, and the one that lies closest to the ovary, is the ovarian fimbria.
The fallopian tubes are made up of several layers. The outer layer is a type of membrane known as the serosa. Inside this are layers of muscle, known as the myosalpinx (myo- is a prefix referring to muscle). The number of layers depends on the portion of the tube.
Finally, inside of the fallopian tubes is a deeply folded mucosal surface. This layer also contains cilia. Cilia are hair-like structures. They move to propel the ovulated egg from the ovary towards the uterus. They also help distribute tubal fluid throughout the tube.
The cilia of the fallopian tubes are most numerous at the ovarian end. They also change throughout the menstrual cycle. The beating movement of the cilia increases near the time of ovulation. This is regulated by estrogen and progesterone production. Interestingly, some women with a condition known as Kartagener's syndrome remain fertile even though their cilia movement is impaired.
Anatomical Variations
In rare cases, an accessory fallopian tube can form during development, which can affect fertility. This extra tube generally has an end that is near the ovary but does not extend into the uterus. Therefore, if an egg is picked up by the accessory fallopian tube, although rare, it can be a contributor to infertility and possibly an ectopic pregnancy.
This anatomical variation is rare, but not unheard of, affecting 5% to 6% percent of women in some small studies. Therefore, gynecologists may screen for an accessory fallopian tube in women experiencing infertility.
Other variations include extra openings, closed sacs, and functional changes to the fimbria. There are also cases where one or both fallopian tubes fail to develop.
Function
The primary function of the fallopian tubes is to transport eggs from the ovary to the uterus. The eggs are picked up by the fimbriae and then swept towards the uterus. This movement is directed both by the beating of the cilia and by peristalsis, which is rhythmic contractions of the muscles of the tubes.
When fertilization occurs, it is generally in the fallopian tubes. The sperm travel from the uterus into the tubes, where they may encounter and fertilize an egg. The fertilized egg then continues its movement towards the uterus. If a fertilized egg implants in the uterus, and continues to develop, it becomes a uterine pregnancy.
Successful transport of eggs through the fallopian tubes is necessary for someone to get pregnant without medical intervention. This is why tubal sterilization, which interrupts the function of the tubes, is an effective form of permanent contraception. This is sometimes referred to as getting one's "tubes tied."
Associated Conditions
A few medical conditions are associated with the fallopian tubes. These conditions can impair fertility. Some may also be life-threatening.
Ectopic Pregnancy
Ectopic pregnancy is the condition most commonly associated with the fallopian tubes. It occurs when there is a delay in the transport of the fertilized egg towards the uterus.
In such cases, the fertilized egg may implant and cause an ectopic pregnancy inside the tube. There is also a risk of an ectopic pregnancy in an accessory tube.
Ectopic pregnancy can be very dangerous, with a risk of rupture and even death. For this reason, an ectopic pregnancy cannot be safely carried to term. It may be treated medically or surgically.
Takeaway
Without treatment, ectopic pregnancy can be fatal. It is the second leading cause of pregnancy-related death in the United States. The risk is that the tube may rupture and lead to bleeding and shock.
Salpingitis
Salpingitis refers to an inflammatory disease that leads to the thickening of the tubes. There are two types of salpingitis.
Salpingitis isthmica nodosa involves formation of nodules inside the isthmus section of the tubes. These nodules make it more difficult for eggs to pass through the tubes and increase the risk of ectopic pregnancy. They also reduce fertility. This type of salpingitis is more common in women over 35 and African Americans and doctors do not understand its cause.
In contrast, non-nodular salpingitis (just called salpingitis) is usually caused by an infection, such as those associated with pelvic inflammatory disease. Either acute or chronic salpingitis can also cause tubal blockages and scarring, but not the characteristic nodules of salpingitis isthmica nodosa.
Tubal Infertility
Tubal infertility is a generic term that describes when someone is unable to conceive a pregnancy due to issues with their fallopian tubes. It may be due to a number of causes, from congenital abnormalities to infectious complications.
One of the most common causes of tubal factor infertility is complications of chlamydia. Tubal factor infertility is responsible for a large portion of cases of female infertility. Tubal infertility can also be the result of, intentional, tubal sterilization procedures.
Tubal Torsion
Tubal torsion occurs when the fallopian tube gets twisted, possibly affecting its blood supply. Although this usually happens alongside ovarian torsion (twisting of the ovary), it can happen on its own. Left untreated, tubal torsion can affect fertility.
Hydrosalpinx
Hydrosalpinx describes when one or both fallopian tubes become swollen and filled with fluid. This can be the result of an infection. It can also be caused by an obstruction of one or both ends of the fallopian tube.
Cancer
Primary cancer of the fallopian tube is very rare, but can happen. Less than 1 percent of gynecologic cancers are thought to originate in the fallopian tubes. When cancer occurs in the fallopian tubes it is far more likely to be the result of metastasis from another site, such as ovarian cancer, uterine cancer, cervical cancer. Fallopian tube metastases can also occur from non-gynecologic cancers.
Tests
Problems with the fallopian tubes can be diagnosed with a few different tests.
Hysterosalpingogram
A hysterosalpingogram is a special type of X-ray used to examine the fallopian tubes. During this test, dye is injected through the cervix. That dye flows through the uterus and into the fallopian tubes. Then an X-ray takes a picture of the dye-filled organs to look for any blockages or problems.
Ideally, the hysterosalpingogram will show that fluid can flow easily through the tubes. If not, this is consistent with a tubal obstruction or occlusion, which can be a factor in fertility. This test is done as an outpatient procedure.
Laparoscopy
Laparoscopy is a type of surgery that can be used to examine the reproductive organs. Small incisions are made and a camera is inserted into the abdomen. This allows the healthcare provider to physically see the outside of the fallopian tubes and whether there appear to be any blockages or damage.
This type of surgery is often referred to as minimally invasive surgery. It has the advantage that if abnormalities are found during the procedure, the doctor may be able to treat them immediately.
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