The equine reproductive tract
Keywords: tract, equine, anatomy, reproductive
This is a dorsal view of the equine reproductive tract showing many clinically important structures.
Note: From the cervix caudally, the tract has been rotated counter-clockwise 90 degrees (viewed caudal to cranial; see arrow) on its longitudinal axis. This was done to afford a lateral view of the vagina and its vestibule. This explains why the rectum is situated on the left side of the vagina in this image.
This is a dorsal view of the equine reproductive tract showing many clinically important structures.
Note: From the cervix caudally, the tract has been rotated counter-clockwise 90 degrees (viewed caudal to cranial; see arrow) on its longitudinal axis. This was done to afford a lateral view of the vagina and its vestibule. This explains why the rectum is situated on the left side of the vagina in this image.
Image size: 1406 x 1250 px
Further notes:
The term "vestibulovaginal seal" may be foreign to some readers. The term "vestibular seal" is also used. This is one of three important barriers between the outside world and the sterile sanctum of the uterus. From caudal to cranial, they are the vulvar lips, the vestibulovaginal seal and of course, the cervix. Readers may recall that the vestibulovaginal seal is none other than the remnants of the hymen; the junction between endo- and ectodermal origins of the reproductive tract. In young mares especially, the vestibulovaginal seal may be so effective that it is difficult to completely insert a vaginal speculum. This may lead one to suspect the presence of a persistent hymen. A gloved hand examination will reveal that this is not the case and after having parted the "valves" of the seal, the speculum can be inserted to the level of the cervix.
The term vulva is a noun and vulvar is an adjective. Hence the use of vulvar lips, not vulva lips in this entry. The term vulva is often erroneously used as an adjective
Further notes:
The term "vestibulovaginal seal" may be foreign to some readers. The term "vestibular seal" is also used. This is one of three important barriers between the outside world and the sterile sanctum of the uterus. From caudal to cranial, they are the vulvar lips, the vestibulovaginal seal and of course, the cervix. Readers may recall that the vestibulovaginal seal is none other than the remnants of the hymen; the junction between endo- and ectodermal origins of the reproductive tract. In young mares especially, the vestibulovaginal seal may be so effective that it is difficult to completely insert a vaginal speculum. This may lead one to suspect the presence of a persistent hymen. A gloved hand examination will reveal that this is not the case and after having parted the "valves" of the seal, the speculum can be inserted to the level of the cervix.
The term vulva is a noun and vulvar is an adjective. Hence the use of vulvar lips, not vulva lips in this entry. The term vulva is often erroneously used as an adjective
| Although not part of the reproductive tract, the urethra and bladder deserves some comment in this entry: During routine transrectal ultrasonography of the reproductive tract, the bladder serves as one of several landmarks. In the image below, calcium carbonate crystals and cellular debris have been displaced by the less echogenic urine flowing into the bladder. The ureters enter the bladder cranially (green arrow). 
The equine cervix is more distensible than that in other species. With patience and a gentle approach, large structures can be retrieved from the uterus via the cervix. The author has even removed an unwanted normal five month fetus via the cervix. Like the cervix, the urethra and its sphincter are also highly distensible. The image above shows that urinary crystals are strongly echogenic on ultrasonography; not surprisingly, the same is true of uroliths. Using an approach similar to that for cervical dilation, even large uroliths can be removed from the bladder. One such urolith is shown below.
Image size: 2500 x 1797 px
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