An STL model of the equine uterus
Keywords: model, 3D, STL, equine, uterus.
The author has used a stereolithographic (STL) file to view and print equine uteruses and pelvic structures in 3D.
NEW:
This, small file can even be downloaded on a cell phone. Pay no attention to dialog alluding to processing of the file. Go ahead and
download it. With the App "
Fast STL viewer" (see Google play store)
already downloaded on your phone, click on this downloaded file (
not the App itself!) and the uterus will appear on your phone as shown in the thumbnail above. Incidentally, the same file can be downloaded and viewed on your laptop.
Viewing the model:
For STL viewing alone on your laptop the author suggests that you
download this file. Click on it and your laptop (PC or Apple) will bring up a suitable program for viewing. An example of such an interface is shown below.
Printing the model:
Custom STL printing can be done through
Axis Prototypes in Montreal after contacting the author. Axis holds the right to a digitally engineered model of the tract and pelvis that is ready for printing. High quality prints
such as those seen here are not inexpensive. Printing a 25 cm model (caudal to cranial) printed from STS nylon will cost approximately $600 Can. ($460 US).
Manipulating the model:
In the absence of a real uterus or a printed tract, this digital model serves to remind one of many practical aspects of equine reproduction A short list comes to mind immediately. Some may wish to print this list so that it can be referred to as the model is manipulated. Better still, manipulate the model on a cell phone while reading the learning points on a laptop.
1.Rotate the tract for a view of the vulva lips and clitoris. Be reminded of its "winking" appearance often, but not exclusively, seen during estrus. Note the importance of the clitoris in diagnosis of CEM and the conformation of the vulva lips in infertility.
2.Enter the vagina and move cranially until the external urethral orifice is encountered. Note that the hymen is normally found just cranial to the orifice but is absent here because this tract was modeled from that of a pluriparous mare. At this point, one should also contemplate the potential problem of urine pooling in the cranial vagina in older mares due to splanchnoptosis.
3.Traveling further cranial in the vagina, one can see the opening of the cervix, showing its dorsal frenulum. Consider the simple nature of the equine cervix compared to that in other species i.e. there are no transverse cervical rings and the cervix is easily dilated for artificial insemination, embryo collection and is even distensible enough to remove fetuses that are three or four months old. The same distensibility is certainly not encountered in ruminants and other domestic animals.
4.Turning to the left and right at a point just caudal to the cervix, one should be reminded that the vagina lies completely within the peritoneal cavity at this point. This is important because it permits one to penetrate the cranial vagina for standing ovariectomy in mares. It also means that if the cranial vagina is torn during foaling, evisceration can occur from this site.
5.Withdraw from the vagina and rotate the model so that the cervix is visible from within the peritoneal cavity. Note that the cranial portion of cervix is firmly suspended between the ilial shafts on either side, by the mesocervix i.e. the caudal portion of the mesometrium. This is significant because the cervix of a mare cannot be grasped, elevated and manipulated as it can in a cow.
6.Rotate and tilt the model so that the mesometrium, containing the uterine artery (middle uterine artery) can be seen clearly. Be reminded that a uterine artery can be forced back against the shaft of the ileum during foaling, rupturing the vessel, causing severe hemorrhage within the mesometrium. Unlike the situation in cows, there is no fremitus in this artery during pregnancy.
7.Rotate the model so that the attachment of the mesometrium the uterus along its lateral borders can be appreciated. Note in turn, how the mesometrium is attached to the abdominal wall on either side. This firm attachment affords substantial stability to the equine uterus and explains in part why uterine torsion is less common in mares than it is in cows. It also means that the equine uterus cannot be retracted during palpation as is done in cattle.
8.Rotate the uterus so that the intercornual ligament is visible. Although it is fairly well-developed. It is never used to retract the uterus for reasons just mentioned.
9.Tilt the uterus so that its dorsal surface is visible, showing how the bifurcation of the uterine horns provides a T-shaped structure instead of the Y-shape characteristic of the bovine uterus.
10.Rotate the uterus up and down on it's transverse axis, noting the length of the uterine body in a mare compared to the very short body in ruminants. This has many implications. For example, in cattle is very important to enter a particular uterine horn for insemination or embryo collection. In mares by contrast, the long uterine body means that semen is simply deposited anywhere in the body and during embryo collection, the embryo is collected from the uterine body.
11.Rotate the tract and pan in and out over the ovaries, noting their large size in comparison to those of cows. Be reminded that although equine corpora lutea are three or four times the diameter of bovine corpora lutea, they cannot be detected by transrectal ovarian palpation. This is because equine ovaries are surrounded by thick tunica albugineae, disguising the presence of corpora lutea. Therefore, to determine if a mare is ovulating (in the absence of progesterone assay) one must use ultrasonography
12. Noticeably absent from this model are the ovarian bursae. The author apologizes for that oversight and time allowing, will add that in his next life.
