Fallopian Tubes

What springs to mind when Fallopian tubes are mentioned?  That they “connect” the ovaries to the uterus which leads finally to the vagina and the outside of the body?  Perhaps you think about ectopic pregnancies, as most ectopic pregnancies are indeed “tubal” pregnancies.  Whatever you may think of when Fallopian tubes are brought up, they are some of the least considered and understood parts of a woman’s reproductive tract.  Besides connecting the uterus and ovaries, do they do anything else?  Are they homologous to any part of the male anatomy?  Let’s try to answer some of the most common questions about Fallopian tubes.

First, where does the name “Fallopian” come from?  Unlike most parts of a woman’s reproductive system, this name does not come from Latin or Greek.  The Fallopian tubes are named for Gabriele Falloppio, a 16th-century Italian anatomist.  The canal through which the facial nerve runs after leaving the auditory cochlear nerve is also named after him–the aquaeductus Fallopii.

Back to the subject, why are the Fallopian tubes so often ignored?  Perhaps it has something to do with the lack of pathology or disease associated with the Fallopian tubes.  The most common maladies associated with the Fallopian tubes are, indeed, tubal (ectopic) pregnancy and pelvic inflammatory disease (PID).  (To read about two cases of rare ectopic pregnancies, click here.)  Ectopic  pregnancies are estimated to account for less than two of every one-hundred pregnancies.  PID is estimated to occur in nearly one in seven women in the United States.  PID accounts for a large number of all ectopic pregnancies, especially tubal.  Other disease are very rare in the Fallopian tubes.  Cancer, for example, is extremely rare and when it occurs it is often the result of adjacent cancer (such as ovarian).

So, what does a Fallopian tube look like?

The above sketch shows the different parts of the Fallopian tubes.  The fimbriae are the fringe-like extensions from the ostium of the Fallopian tube.   During ovulation, hormones stimulate the fimbriae to make a gentle sweeping motion against the ovaries to pull the released egg (or ovum) into the Fallopian tube.  The ovary and Fallopian are not actually connected to each other.  The ostium is where the fimbriae end and the Fallopian tube begins.  The infundibulum is the wider end of the Fallopian tube that narrows into the ampulla, which is the twisting portion of the tube in the above sketch.  It is where most fertilizations occur.  The ampulla continues into the isthmus, the shortest and most narrow portion of the Fallopian tube.  The pars uterina is the place where the uterus and Fallopian tube connects.

This sketch indicates better how the Fallopian tubes, uterus, and ovaries are all connected (or, in fact, not connected).  Most human Fallopian tubes are between seven and fourteen centimeters in length. Once an egg has entered the Fallopian tube, the mucosal cilia of the Fallopian tube move the egg towards the uterus.  The cilia are finger-like projects that sweep or push.  (Cilia are also found in the windpipe and sweep mucus and dust away from the lungs.)  Finally, Fallopian tubes are not homologous to any structure in the male body, thus they are completely unique to the female body.  (The ovaries, for example, are homologous to testes in males.)

Now, hopefully you and I both know a little more about the Fallopian tubes.  Want to know more or already know more and want to share it?  Please, don’t be shy!

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Sperm

Sperm may seem an odd choice of subject for a “young woman’s guide to gynecology and obstetrics.”  But it is this last word, obstetrics, that makes sperm a good choice for an entry subject.  Arguably, without sperm, obstetrics would not exist.   This may not always be the case, but for the time being, each human pregnancy makes use of sperm somewhere in the process.  So, let’s talk about sperm, baby!

Sperm is the male counterpart to the female gamete, the ovum (or egg).  Technically, what we commonly refer to as a sperm should be considered more of a sperm cell called a spermatozoon (spermatozoa, plural).  Since virtually everyone refers to the spermatozoon as a sperm, I will continue to use the word sperm in its place.  The human sperm consists of, ostensibly, a head an a tail.  This simple-looking structure belies its key importance in creating life.  Stored within the sperm is a complex DNA code that will (usually)[1] determine the sex of the resultant child and influence its phenotypical appearance–short or tall, dark or light, thin or stout–and many other genetic factors.

Each sperm is about three micrometers at its widest and about fifty micrometers long.  The tail of the sperm powers it forward, almost like a propeller, at about 1 to 3 millimeters per minute.  The semen, the fluid in which sperm are expelled from the male, has a chemical balance that keeps the sperm mostly inert until it is neutralized by the acidic environment of a vagina.  The sperm, when entering the vagina, journey upward in search of an egg to fertilize.  If the sperm do find an egg they will attempt to penetrate the membrane.  A single  sperm will succeed in penetrating the egg and the fusion of the two begins the process of meiosis in which the DNA of the mother and the father are spliced together to form a new set of DNA.

At this point, the sperm has reached its goal and blends into the developing human.  However, the sperm has many variations and not all sperm conform to the usual model we have in mind.  Abnormal sperm are actually quite common and come in many varieties.  For example, there are sperm with two heads, two tails, both, neither, and various other extra and missing parts.  Most abnormally structured sperm do not pose a genetic complication or threat to a potential pregnancy.  Because of structural deficiencies these abnormal sperm are not likely to reach an egg in the first place.

In all, sperm are an interesting and integral part to creating life and without them, there would be little basis for obstetrics.  So, any time you are thinking about obstetrics keep in mind the “little swimmers” that help make it possible.  Comments, questions, otherwise?  Please bring them forward!

[1] I am careful to say that the sperm usually determines the sex of a child because certain genetic problems can preclude a child with XY sex chromosomes from developing male characteristics, including genitalia, thus the Y-sperm from the father in this case does not determine the sex of the child.