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Keywords:

  • ovarian vasculature;
  • uterine vasculature;
  • goat uterine vessels;
  • multiple pregnancy adaptation;
  • tissue clearing

Abstract

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. LITERATURE CITED

Arteries of the reproductive tracts of nonpregnant does and does at 4, 7, 10, 13, 16, and 18 weeks of gestation were injected in situ with Microfil®. The tracts were fixed, dehydrated, and rendered transparent to reveal the paths of arteries. The tortuous ovarian artery lay in close apposition to the uterine tributary of the ovarian vein, an arrangement that may serve as a local utero-ovarian pathway for the corpus luteum (CL) luteolysis at the end of nonfertile estrous cycle. During pregnancy, this arteriovenous arrangement might transfer luteotropic substances from uterus to ovary, which might serve in maternal recognition of pregnancy and fit the fact that the goat is CL-dependent throughout gestation. In some cases of triplets, the size of the uterine branch of the ovarian artery was equal to or even larger than that of its parent artery and/or the ipsilateral uterine artery, and the vaginal artery contributed a connecting branch to the uterine artery. These physiological adaptations of the ovarian and/or vaginal arteries, which have not previously been described, correlate well with the increasing nutrient demands of the growing multiple fetuses. Anat Rec, 2007. © 2007 Wiley-Liss, Inc.

The placenta is one of the most important transient organs and has been the subject of extensive research in many species. Probably one of the most important aspects of placental studies is the morphology and development of the vasculature since this directly relates to the principal placental function (gas, nutrient, and waste exchange between the mother and fetus) and of course to the survival of the fetus to term.

According to the traditional classification, the goat placenta is regarded as chorioallantoic (Kaufmann and Burton,1994; Leiser and Kaufmann,1994). Goats develop a partially adeciduate, cotyledonary, and villous type placenta. The interhemal barrier is classified as epitheliochorial (Kaufmann and Burton,1994), and syndesmochorial in older literature. The term “synepitheliochorial” is used in recent literature (Wooding,1992; Leiser and Kaufmann,1994) because of the fusion of the binucleate trophoblasts with the uterine epithelium.

The importance of understanding the distribution of blood vessels in female reproductive organs has long been recognized. By the early 1970s, studies of the control of the lifespan of the corpus luteum (CL) by the uterus itself had led to an entirely new concept: that of the internal regulation of physiological process through local venoarterial pathways. This concept was explored by Del Campo and Ginther (1973) and the evidence for it was extensively reviewed by Ginther (1974). The presence or absence of an embryo is the ultimate factor that controls the maintenance or regression of the CL; hence, the uterus terminates the life of the corpus luteum at the end of a nonfertile estrous cycle. This may be via a systemic pathway in some species and through a local utero-ovarian pathway in others. In this process, PGF produced by the endometrium leaves via the uterine tributary of the ovarian vein, passing directly into the adjacent ovarian artery causing CL regression. Understanding this mechanism was the key to the optimization of the minimal effective dose of exogenous prostaglandin that could be given systemically to different species of farm animals, so the knowledge had immediate practical use. Empirical work has shown that the minimum effective dose of a single systemic injection of PGF was 6.0 mg in ewes and 1.25 mg in pony mares. The efficacy of the dose of PGF can be attributed to several factors, including the bioactivity of the PGF of the different species; but it is equally possible that it may be due to the presence of a local utero-ovarian pathway in sheep versus a mainly systemic pathway in horses (Ginther,1974).

The angioarchitecture of the utero-ovarian vasculature in most nonpregnant farm animals has been described (Ginther,1976), but no reports exist on the distribution of these vessels in goats. Surprisingly, none are available on the vasculature at different stages of pregnancy in any common farm animal. Furthermore, the detailed angioarchitecture of the uterine vessels has been ignored for years, and currently no adequate data are available about their distribution and/or nomenclature. These knowledge gaps complicate studies on reproduction and reproductive organs and introduce variability of interpretation and hence possible misunderstanding of the results of different experiments.

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. LITERATURE CITED

Experimental Groups

The experimental protocol and all procedures used in this work were reviewed and approved by the Virginia Tech Animal Care and Use Committee. The procedures described below were applied to a group of nonpregnant doe goats, and another of timed pregnant does. Does were Boer X Spanish, all aged between 2.5 and 3 years. All came from the same flock, had a previous history of successful pregnancies, and were brought to the college at the same time and housed under the same conditions in identical quarters. Pregnant does were euthanized at 4, 7, 10, 13, 16, and 18 weeks of pregnancy.

The number of specimens examined at each stage is shown in Table 1. With the exception of one specimen at the 7-week stage, all specimens had multiple fetuses. Six cleared specimens had triplets and five had twins. Incompletely injected or missing vessels in any particular specimen were excluded from the study and the supply of the area was reported as missing. We calculated the percentage of specimens showing a particular pattern of vessel distribution by dividing the number of specimens showing that pattern by the number of total specimens used to study the pattern in question. Radiographs were taken from all cleared specimens to show the vascular pathways.

Table 1. Number of specimens examined at each stage
Stage of pregnancy# of specimens examinedaSpecimens used to study origin of main vesselsSpecimens used to study pattern of fine vessels
Tissue clearingCorrosion casting
  • a

    Three teaching specimens from non-pregnant does previously prepared in our laboratory using conventional embalming/latex injection, were also used.

  • b

    An additional specimen was used to study origin of the uterine arteries.

  • c

    An additional specimen was used to study origin of the uterine arteries.

Non-pregnant326b3
4222c2
72242
102222
133232
162222
182232

Animal Preparation

Doe goats received an intramuscular (IM) injection of xylazine (0.2 mg/kg of body weight) and atropine (0.04 mg/kg) 10 min after administration of an IM injection of acepromazine (0.05 mg/kg). The does were then anesthetized by intravenous injection of ketamine (5.0 mg/kg) 10 min after sedative injection. They were injected intravenously with 10 ml of heparin (1,000 IU) to suppress coagulation. Animals were exsanguinated via a cannula placed in the common carotid artery, then the cannula was subsequently used as an inflow port for perfusion with heparinized physiologic saline (1.0 ml heparin per liter). Saline was infused at about 40°C (normal range of body temperature of the goat is 39–40°C). Blood and saline were allowed to flow out of a cannula placed in the external jugular vein. Blood washout was performed using a Portiboy embalming pump, Model PE10 (Portiboy Company, Westport, CT) at a rate of 90 ml/min and 34.5 kPa pressure. The abdominal wall was opened along a ventral midline incision. The esophagus and rectum were ligated, and the digestive organs were removed to expose the abdominal aorta and reproductive organs. All vessels supplying nonreproductive organs were ligated. The reproductive tract was injected through the abdominal aorta via a high-density polyethylene cannula placed just cranial to the origin of the ovarian arteries. A three-way stopcock was placed in line between the cannula and the syringe to permit change of syringes.

Tissue Clearing

The tissue-clearing technique consists of the injection of a casting medium into the vascular system, fixation, dehydration, clearing of the surrounding tissues, followed by observation and photography of the resulting cleared specimen. The tract was infused with physiological saline (40°C) at a rate of 5 ml/min using a Harvard infusion pump, Model 22 (Harvard Apparatus, Holliston, MA), then with white Microfil MV series (Flow Tech, Carver, MA) at the same rate using the same infusion pump. Red Microfil was used in a few specimens. Microfil compound was mixed with an equal quantity (by weight) of a mixture of MV and HV diluents followed by the addition of 5% of the curing agent. The filling of the vasculature was considered complete when Microfil was visible to the naked eye in the fine vessels of the caruncles. The whole hindquarters were immersed in physiological saline during and after injection to allow free flow of Microfil in the vasculature. The specimen was left in place for 4 hr at room temperature, then refrigerated overnight to ensure complete polymerization of Microfil.

The entire reproductive tract with its mesenteries was removed intact, pinned to a dissecting pad, and fixed in AFA (300 cm3 95% alcohol, 100 cm3 10% buffered formalin, 100 cm3 glacial acetic acid, 500 cm3 distilled water) for 24–48 hr (Orsini,1962). At least one tract at each stage was cleared using the alcohol-methyl salicylate clearing sequence and another one using glycerin clearing (Orsini,1962; Del Campo et al.,1974). When alcohol-methyl salicylate sequence was intended, the tract was dehydrated after fixation in an ascending ethanol series. The time interval between ethanol changes depended on the size of the specimen; it ranged from 24 to 72 hr to ensure proper dehydration. Hydrogen peroxide was added to the 70% and 80% alcohols (1 ml of 30% hydrogen peroxide per 1 L of alcohol) for bleaching. The dehydrated tract was then immersed in methyl salicylate (VWR, West Chester, PA), where it was stored and studied.

For glycerin clearing, the tract was immersed in decreasingly dilute glycerin/distilled water baths beginning at 50% at 10% increments. The time interval between glycerin changes depended on the size of the specimen, ranging from 48 to 96 hr. These specimens were stored and studied in 100% glycerin (VWR).

Specimens prepared by both of these methods can be stored indefinitely and studied while immersed in the clearing agents. Because Microfil is radio-opaque, we were able to confirm our visual observations using X-ray images.

RESULTS

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. LITERATURE CITED

The uterus is supplied by branches of the ovarian arteries (aa. ovarica), uterine arteries (aa. uterina), and vaginal arteries (aa. vaginalis; Fig. 1). The data given here apply to all stages of pregnancy except when an adaptation of the ovarian and/or vaginal arteries was observed. No difference was observed in the origin and distribution of the ovarian, uterine, and vaginal arteries between pregnant and nonpregnant does, but differences existed within specimens from pregnant and/or nonpregnant does.

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Figure 1. Dorsal view of methyl salicylate-cleared uterus from a pregnant doe at 7 weeks. Note the main blood supply to the uterus by branches of the ovarian arteries (right ovarian artery, ROA; left ovarian artery, LOA), uterine arteries (right uterine artery, RUA; left uterine artery, LUA), and vaginal arteries (right vaginal artery, RVA; left vaginal artery, LVA). The ovarian artery arises from the aorta (not shown). The uterine artery arises from the internal iliac artery together with the umbilical artery (shown on the right side). The vaginal artery arises from the internal iliac artery (shown on both sides). RUma, right umbilical artery; LUmA, left umbilical artery; RL, round ligament of the uterus; RIIA, right internal iliac artery; LIIA, left internal iliac artery; LH, left uterine horn; RH, right uterine horn; BU, body of the uterus; CR, cervix; VG, vagina; UB, urinary bladder; RO, right ovary; LO, left ovary.

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Ovarian Arteries

The ovarian arteries arose from the dorsolateral surface of the abdominal aorta (aorta abdominalis). Both arteries originated at the same level in 59.1% of the specimens studied. The right ovarian artery (a. ovarica dextra) arose cranial to the left artery in 18.2%. The left ovarian artery (a. ovarica sinistra) arose cranial to the right one in 22.7% (Fig. 2). Figures 3–6 show the course and branching patterns of the right and left ovarian arteries. The ovarian artery was tortuous and lay in close apposition to the ovarian vein in all specimens studied. This arrangement was maintained throughout gestation. The pattern of branching of the right and left ovarian arteries was similar. The ovarian artery ran caudally in a straight course for a short distance (about 1.5 cm), then coiled around the ovarian vein (v. ovarica). It gave off both a uterine branch (ramus uterinus) and a uterine tube branch (ramus tubarius), then continued to enter the ovary. The pattern of origin of the uterine tube and uterine branches of the right and left ovarian arteries is summarized in Table 2.

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Figure 2. Anatomical variations in the origin of main vessels supplying the uterus. A and B are glycerin-cleared specimens. C: Methyl methacrylate corrosion-cast specimen. D: Methyl salicylate-cleared specimen. The ovarian arteries arise from the aorta, showing some variation in the level of origin among specimens, as illustrated. Both right and left ovarian arteries (ROA and LOA) may arise at the same level (A), the right ovarian artery may arise slightly caudal to the left artery (B), or the right ovarian artery may arise cranial to the left one (C). The uterine artery (RUA, right uterine artery; LUA, left uterine artery) arises as a common truck with the umbilical artery (RUmA, right umbilical artery; LUmA, left umbilical artery) from the internal iliac artery (RIIA, right internal iliac artery; LIIA, left internal iliac artery) in most cases (A–C), but the uterine artery arises separately from the internal iliac artery in a few cases (D). IIAA, right and left internal iliac arteries; CdMA, caudal mesenteric artery; REIA, right external iliac artery; LEIA, left external iliac artery; R and L are right and left sides, respectively in A–C; arrowhead in B points at the median sacral artery.

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Figure 3. Methyl salicylate-cleared specimen showing branches of the ovarian artery. In A, the uterine branch of the ovarian artery (UBOA) is given off the ovarian artery before it gives the uterine tube branch (TBOA). In B, the uterine tube branch is given off the ovarian artery after it gives rise to the uterine branch. In C, both the uterine and uterine tube branches of the ovarian artery originate together as a common trunk (at the tip of the outlined arrow). D: High-magnification image of C. OA, ovarian artery; OBOA, proper ovarian branch of the ovarian artery; UA, uterine artery; O, ovary; UH, uterine horn.

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Figure 4. Glycerin-cleared specimens showing examples of adaptation of the ovarian artery to multiple pregnancies. In A, the diameter of the uterine branch of ovarian artery (UBOA) is nearly equal to that of the continuation of its parent artery (the ovarian artery, OA). In B, the diameter of the uterine branch of the ovarian artery is larger than that of its parent artery. UH, uterine horn; O, ovary.

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Figure 5. A: Dorsal view of a portion of the uterine horn (UH) of a methyl salicylate-cleared specimen showing an example of the adaptation of the uterine branch of the ovarian artery to multiple pregnancies. Note that the uterine branch of the ovarian artery (UBOA) gives rise to an additional branch (delineated between the two arrowheads) that joins a branch of the uterine artery (UA) to supply the uterine horn (UH). B: Ventral view of A. O, ovary.

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Figure 6. Glycerin-cleared specimen showing an example of the adaptation of the ovarian artery to multiple pregnancies. In this case, the ovarian artery gives an additional branch (BOA), which is larger than the ipsilateral uterine artery (UA) and supplies the entire dorsal surface of the uterine horn. This branch also anastomoses (arrowheads in D) with subdivisions of the uterine branch of the ovarian artery and uterine branch of the vaginal artery (not shown). A: Dorsal view showing the origin of the additional branch of the ovarian artery (BOA). B: Ventral view showing the course of this branch to the dorsal surface of the uterine horn. C: Dorsal view of an area of the uterine horn showing the supply of the dorsal surface of the uterine horn by the additional branch of the ovarian artery. The arrowheads in D show the anastomosis of the additional branch of the ovarian artery with the uterine branch of the ovarian artery. UH, uterine horn.

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Table 2. Pattern of origin of the branches of the ovarian arteries and area supplied by each
Pattern of branchingR ovarian arteryL ovarian artery
  • a

    No information about the supply of the ampulla was obtained in 33% of the specimens due to incomplete injection of the area.

  • b

    Information about the supply of the ampulla was lost in 26% of the specimens studied.

The uterine branch came off the ovarian artery after the uterine tube branch50%18%
The uterine tube branch arose from the ovarian artery after the uterine branch43%73%
Both the uterine and uterine tube branches came off the ovarian artery together as a common trunk7%9%
Area of the uterine tube suppliedUterine tube branchUterine branchUterine tube branchUterine branch
Infundibulum100% 100% 
Ampulla47%a20%54%b20%
Isthmus and uterotubal junction13%100%13%100%

The uterine tube branch ran cranial to the ovary in a serpentine pattern until it reached the abuterine pole of the ovary. It gave branches to the mesosalpinx and mesovarium. Those branches ran straight and almost parallel to each other in most specimens. The uterine branch ran caudal to the ovary toward the uterus, then it continued and, before reaching the uterine horn, divided to supply the dorsal and ventral surfaces of the area close to the tip of the uterine horn in 87% of the specimens. Information about the supply of this area by the uterine branch of the ovarian artery was missing in 13% of the specimens studied due to incomplete injection of the area. There was an anastomosis between branches of the uterine branch of the ovarian artery and branches of the cranial branch (in some cases with the caudal branch) of the uterine artery. The area of the uterine tube supplied by the uterine tube and uterine branches of the right and left ovarian arteries is summarized in Table 2.

The branches of the ovarian artery were smaller than the parent artery, except that in 66.7% of triplet pregnancies, the diameter of the uterine branch of the right ovarian artery was almost equal to that of the continuation of its parent artery. In 16.7% of triplets and 16.7% of all pregnant tracts, the diameter of the uterine branch of the left ovarian artery was larger than that of its parent artery.

In half the triplet pregnancies, the uterine branch of the right ovarian artery gave off a branch that joined a branch of the uterine artery to supply the uterine horn; the uterine branch of the right ovarian artery also gave off an additional branch that supplied the dorsal surface of the area adjacent to the tip of the uterine horn.

In 33.3% of triplets and 25% of all pregnant tracts, the uterine branch of the left ovarian artery gave off a branch that joined a branch of the uterine artery and supplied the dorsal surface of the area adjacent to the tip of the uterine horn, or supplied the ventral surface of the area adjacent to the tip of the uterine horn in 8.3% of specimens from pregnant does. The uterine branch of the left ovarian artery also gave off additional branches to supply the uterine horn in 50% of triplets and 33.3% of specimens from pregnant does. In a doe pregnant at 18 weeks with triplets, the left ovarian artery gave rise to an additional branch to supply the uterus; this branch was larger than the ipsilateral uterine artery and supplied the entire dorsal surface of the left uterine horn. It anastomosed with both the uterine branch of the ovarian artery and uterine branch of the vaginal artery.

Uterine Arteries

Figures 7–9 show the course and branching patterns of the uterine arteries (aa. uterina). The right (a. uterina dextra) and left (a. uterina sinistra) uterine arteries had the same origin. The uterine artery arose together with the umbilical artery (a. umbilicalis) as a common trunk from the internal iliac artery (a. iliaca interna) in 96% of the specimens examined, or alone directly from the internal iliac artery in 4% (Fig. 2). The uterine artery ran caudally toward the uterus and divided within the mesometrium into caudal and cranial branches. This occurred at about the level of the bifurcation of the uterine body into horns in 91% of the specimens, and at a level cranial to the bifurcation in 9%. In some specimens (5.6%), the right uterine artery gave off a branch before dividing into its main cranial and caudal branches. This less-common branch supplied the ventral surface of the uterine horn from the middle portion to the tip. The distribution of the caudal and cranial branches of the uterine artery was consistent in most of the specimens. The cranial and caudal branches of the right and left uterine arteries divided into two or more primary branches, which in turn divided into secondary branches. Primary and/or secondary branches of the caudal and cranial branches of the uterine arteries gave rise to arcuate arteries, which formed an arch that followed the contour of the lesser curvature of the uterus. Radial arteries arose from arcuate arteries. These arteries were longer than the areas of the uterus through which they traveled; therefore, they followed a helical course. As gestation advanced and the size of the uterus increased, these arteries were drawn out straight. Each radial artery could supply more than one caruncle, and individual caruncles could be supplied by more than one radial artery. The distribution of the subdivisions of the cranial and caudal branches of the right and left uterine arteries is summarized in Table 3 and shown in Figure 10. There was an anastomosis between subdivisions of the branches of the right and left uterine arteries in the area between the two uterine horns at the vicinity of the intercornual ligament.

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Figure 7. Ventral view of a methyl salicylate-cleared uterus from a pregnant doe showing the branching pattern of right and left uterine arteries (RUA, LUA). Panel A is a closer view of the specimen providing the nomenclature of the branches of the uterine artery. The uterine artery (UA) divides into cranial (CrB) and caudal (CdB) branches. The cranial and caudal branches of the uterine artery further divide into primary branches (PB), which in turn give rise to secondary branches (SB). Primary and/or secondary branches of the cranial and caudal branches of the uterine artery give rise to arcuate arteries (AA; arrowheads). Arcuate arteries follow the contour of the lesser curvature of the uterine horn, where they give rise to radial arteries (RA). Panel B shows the dorsal view of a portion of the uterine horn. Radial arteries (black arrows) arise or radiate from arcuate arteries (light arrowheads). Caruncles are supplied by branches (black arrowheads) of radial arteries. Panel C shows internal view (light arrows are radial arteries).

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Figure 8. Methyl salicylate-cleared uterus. A: Ventral view of the uterus showing the anastomosis between subdivisions of the caudal branches of the right and left uterine arteries (CdRUA and CdLUA, respectively) and branches of the vaginal arteries (VA) on the ventral surface of the caudal area of the uterine horns and uterine body. B: Dorsal view showing the anastomosis between subdivisions of the caudal branches of the uterine arteries (CdUA) and of vaginal arteries (VA) on the dorsal surface of the caudal part of the uterine horns and uterine body.

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Figure 9. Methyl salicylate-cleared pregnant uteri. A: Early pregnant (4 weeks). B: Late pregnant (16 weeks). The radial arteries (RA) radiate from arcuate arteries (arrowheads). Radial arteries are longer than the areas of the uterus they travel through; therefore, they follow a helical course in early pregnancy (A). As the gestation advances and size of the uterus increases, these arteries are drawn out straight (B).

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Figure 10. Schematic diagram of the uterus (horns and body) showing the regional arterial supply of the dorsal and ventral surfaces of different parts of the right (A) and left (B) sides of the uterus. The percentage shown is the percentage of specimens supplied by each artery (i.e., the yellow-shaded area on the dorsal surface of the right side of the uterus is supplied by the cranial branch of the uterine artery in 86.7% of the specimens studied, and by the caudal branch of the uterine artery in 13.3% of the specimens studied). The dorsal and ventral surfaces of the area close to the tip of the uterine horn are supplied by the uterine branch of the ovarian artery (not shown), which anastomoses with either the cranial branch (in most cases), or the caudal branch of the uterine artery, or the additional branch of the ovarian artery to the uterus in the left side in 16.7% of triplets. The ovarian artery gave off an additional branch, which supplied the entire dorsal surface of the left uterine horn in 16.7% of triplets (this is not included on the diagram). Cr, cranial branch of the uterine artery; Cd, caudal branch of the uterine artery; ub, a branch given by the uterine artery before dividing into its main two branches (the cranial and caudal branches). VA, uterine branch of vaginal artery.

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Table 3. The distribution of the subdivisions of the cranial and caudal branches of the uterine arteries
Area suppliedR uterine arteryL uterine artery
Caudal branchCranial branchCaudal branchCranial branch
  • a

    Information about the supply of this area on the left side was not available in 6.7% due to incomplete injection of this area.

Ventral surface of the caudal part of the uterine horn100 100 
Dorsal surface of the caudal part of the uterine horn93.36.786.713.3
Ventral surface of the uterine body80 86.7 
Dorsal surface of the uterine body606.740 
Ventral surface of the middle part of the uterine horn73.326.786.713.3
Dorsal surface of the middle part of the uterine horn406053.346.7
Ventral surface of the uterine horn from the middle part to the tip6.786.713.393.3
Dorsal surface of the uterine horn from the middle part to the tipa13.386.7 86.7

The caudal branches of the right uterine artery anastomosed with branches of the uterine branch of the vaginal artery on the ventral surface of the caudal area of the uterine horn and uterine body in 86.7% of the specimens and on the dorsal surface in 60%. The caudal branches of the left uterine artery anastomosed with branches of the vaginal artery on the ventral surface of the caudal part of the uterine horn in 66.7% and on the dorsal surface in 40%.

Vaginal Arteries

The vaginal artery arose from the internal iliac artery at the level of the vagina, giving caudal and cranial branches. The caudal branches ran along the lateral border of the vagina to supply the vagina, vestibule, and perineal area. The cranial or uterine branch (ramus uterinus) ran from the lateral to the ventral surface of the vagina, cervix and uterine body. During its course to the uterus, it gave off branches to the vagina and the dorsal surface of the cervix at various levels.

The uterine branch of the right vaginal artery supplied the dorsal surface of the uterine body in 73.3% of the specimens studied and the ventral surface in 86.7%. It anastomosed with subdivisions of the caudal branches of the uterine artery on the dorsal surface of the uterine body in 46.7% and on the ventral surface in 80%. There was a connecting branch between the right uterine artery and the right uterine branch of vaginal artery in 16.7% of triplets (Fig. 11).

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Figure 11. Ventral view of a methyl salicylate-cleared uterus from an 18-week-pregnant doe showing an example of the adaptation of the right vaginal artery to multiple pregnancies. Note the connecting branch (connecting branch of vaginal artery, CBVA) between the right uterine artery (RUA) and the uterine branch of the right vaginal artery (UTRVA). ROA, right ovarian artery; LUA, left uterine artery; UTLVA, uterine branch of the left vaginal artery.

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The uterine branch of the left vaginal artery gave branches to the dorsal surface of the uterine body in 73.3% of the specimens and to the ventral surface in 66.7%. It anastomosed with subdivisions of the caudal branches of the uterine artery on the dorsal surface of the uterine body in 46.7% of the specimens and on the ventral surface in 66.7%. There was a connecting branch between the left uterine artery and the left uterine branch of vaginal artery in 16.7% of triplets (Fig. 12). Figure 10 shows the supply of the dorsal and ventral surfaces of different parts of the uterus by ovarian arteries, uterine arteries, and vaginal arteries.

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Figure 12. Ventral view of a methyl salicylate-cleared uterus from a 13-week-pregnant doe showing an example of the adaptation of the left ovarian artery to multiple pregnancies. Note the connecting branch (connecting branch of vaginal artery, CBVA) between the left uterine artery (LUA) and the uterine branch of the left vaginal artery (UTLVA). LOA, left ovarian artery; UB, urinary bladder.

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Radiography

Radiographs showed the path of vessels supplying the reproductive tract (Fig. 13). However, they did not provide any more information than was obtained from the cleared specimens.

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Figure 13. A radiograph of a Microfil-injected reproductive tract from pregnant doe showing the vascular pathways of its supplying arteries. A, aorta; LOA, left ovarian artery; UBOA, uterine branch of the ovarian artery; RUA, right uterine artery; LUA, left uterine artery; Cd, caudal branch of the left uterine artery; Cr, cranial branch of the left uterine artery; AA, arcuate artery; RIIA, right internal iliac artery; LIIA, left internal iliac artery, RUTVA, uterine branch of the right vaginal artery; LVA, left vaginal artery; O, ovary; UB, urinary bladder. Arrowheads denote radial arteries. The straight dense radio-opaque line is a metal pin used to hold the tract in position.

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DISCUSSION

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. LITERATURE CITED

Techniques Employed

Clearing technique.

Injection of the reproductive tract vasculature with subsequent clearing (rendering transparent) of tissues allowed visualization and studying of the reproductive tract's vascular system in relation to the tissues it supplies. The technique was adopted from Orsini (1962) and Del Campo et al. (1974), with modifications as follows. Blood washout was performed with physiological saline at approximately the normal goat body temperature as a way to maintain the normal physiological state of vessels, including their diameter to facilitate injection, and to avoid extravasation of the injection medium. The use of an infusion pump instead of hand injection provides better control of intraarterial pressure, is documentable, and is reproducible. Microfil rather than latex was injected into the vasculature of the reproductive tracts. Microfil provides complete filling with minimal shrinkage of the vasculature, is easy to prepare, is available in many colors, does not require an acidic environment for curing, and is radio-opaque. Using equal quantity of Microfil and MV diluent resulted in a medium of very low viscosity with the ability to cross capillaries. Since capillary crossing was not desirable in this study, we used a mixture of MV and HV diluents to increase viscosity of the final product to avoid crossing of capillaries. We tried the clearing agents (benzol and benzyl benzoate) used by Orsini (1962) and Del Campo et al. (1974), but no satisfactory results were obtained. Methyl salicylate and glycerin were each used in our experiment as clearing agents, and both gave satisfactory results. Alcohol-methyl salicylate clearing produced a stiffer tissue, which, from an aesthetic point, provides a pleasing view for gross observation, but it is difficult to manipulate. Also, extended exposure to the strong smell of methyl salicylate was unavoidable (even under a fume hood) during the long study time required to examine such a complex vascular system as that of the reproductive tract. Glycerin clearing produced a more flexible tissue, allowing easier manipulation for a given area. Glycerin has a more pleasant smell than that of methyl salicylate, but from an aesthetic point, it does not provide such a pleasing view as that of methyl salicylate.

Radiography.

Because radiography was to be used to study the distribution of the reproductive tract vasculature, Microfil was chosen because of its radio-opacity. However, while radiographs were useful to study vessels' distribution, no more information was obtained from studying them than was available from studying cleared specimens examined with the naked eye. In other words, studying cleared specimens provided enough information to render radiographs unnecessary except perhaps to confirm visual impressions by a second visualization method. Further, due to the inherent disadvantage of radiographs in the form of superimposition of vessels in two-dimensional views, determining the definitive supply of certain area by certain branch was difficult.

Data Obtained

The ovarian artery's tortuousity and close apposition to the uterine branch of the ovarian vein, seen in all specimens in this study, was discussed by Del Campo and Ginther (1973), though they did not examine goats. The higher effective dose of PGF in sheep is due to the presence of mainly a local utero-ovarian pathway in sheep versus a mainly systemic pathway in horses (Ginther,1974). Our study showed that goats are similar to sheep and therefore can be expected to have this local utero-ovarian pathway as well. Substances (such as PGF) can pass from the ovarian vein to the ovarian artery and affect the ovary.

Our work demonstrated that the architecture of the ovarian artery and vein was maintained throughout pregnancy. Maintenance of luteal function during early pregnancy in ewes (Mapletoft et al.,1976) and cows (Del Campo et al.,1980) occurs by local vascular transport of a luteotropic substance from the gravid uterus to the ipsilateral ovary. The nature and chemical properties of this substance were not investigated. The transport of luteotropic substance occurs by means of the close apposition of the ovarian artery to the ovarian vein. This physiological supposition is supported by the anatomic architecture of the utero-ovarian vasculature demonstrated in early pregnancy in ewe and cow, and by the anatomy revealed here for goats as well. Maternal recognition of pregnancy occurs around day 13–14 after ovulation in ewe and 15–16 in cows (Senger,2003). It is achieved by production of certain proteins between days 13 and 21 after ovulation. These include ovine trophoblastic protein 1 (homologous to interferon-α), or bovine trophoblastic protein 1, and pregnancy-specific protein B (pregnancy-associated glycoproteins; PAGs). Ovine and bovine trophoblastic proteins inhibit oxytocin receptor synthesis by endometrial cells and promote protein synthesis by endometrial glands. These proteins are not luteotropic. Pregnancy-specific protein B is produced by binucleate giant cells and has a luteotropic effect. Maternal recognition by means of production of trophoblastic protein 1 does not require a local venoarterial pathway between the uterus and ovary because it is produced in the uterus and acts on the uterus; however, the other protein (pregnancy-specific protein B) is produced in the uterus but acts on the CL so it does require a pathway to reach the ovary. Study by Bridges et al. (1999) proved that there was no luteal source of pregnancy-specific protein B in ewes. Pregnancy-specific protein can reach the ovary by either a local or a systemic pathway. We hypothesize that the predominant mechanism in ewes, cows, and does is the local one between the uterus and ovary. We base this hypothesis on the presence of the intimate arteriorenous approximation and its potential functionality as a local venoarterial pathway. More physiological studies are needed to test this hypothesis. Also, the molecular weight and possible mechanisms of transfer of PAGs should be considered in future studies. Pregnancy-specific protein B has a clinical importance. It can be used for pregnancy diagnosis in goats (Humblot et al.,1990).

Ewes are CL-dependent till 50 days of pregnancy; thereafter, the placenta produces sufficient amounts of progesterone to support pregnancy. Cows are CL-dependent till 6–8 months of gestation. Does are CL-dependent throughout the entire period of pregnancy (Senger,2003). Progesterone is produced almost entirely by the CL in goats, and ovarioectomy at any time causes abortion. The presence of this anatomic arrangement of utero-ovarian vessels has only been demonstrated in nonpregnant (Ginther,1976) and early stage pregnant ewes (Mapletoft et al.,1976) and cows (Del Campo et al.,1980). Whether this arrangement is present at later stages of pregnancy in ewes or cows has not been studied. This work shows that in the goat, this arrangement was in fact maintained throughout pregnancy, which fits the fact that the goat is CL-dependent throughout pregnancy. Factors produced by the placenta could be transported via this anatomic arrangement to maintain the CL throughout pregnancy. Whether CL maintenance is the only function of this anatomic arrangement cannot be elucidated without further studies on the presence of this anatomic arrangement of the ovarian artery and ovarian vein at later stages of pregnancy in ewes and cows, as well as further work coordinating the physiological and anatomic interrelationships in all ruminant species.

Special adaptations of the ovarian and/or vaginal arteries were noted in multiple pregnancies. First, in 66.7% of triplets, the size of the uterine branch of the right ovarian artery was about equal to that of the continuation of its parent artery. Second, in 16.7% of triplets, the size of the uterine branch of the left ovarian artery was actually larger than that of its parent artery. Third, in half of triplet pregnancies in the right side and 33.3% in the left side, the uterine branch of the ovarian artery gave off a branch that joined a branch of the uterine artery and supplied the uterine horn. Fourth, the uterine branch of the ovarian artery also gave off an additional branch that supplied the dorsal surface of the area adjacent to the tip of the uterine horn in half of the triplets. Fifth, in one doe with triplet pregnancies at 18 weeks of pregnancy, the left ovarian artery gave rise to an additional branch to the uterus; this branch was larger than the ipsilateral uterine artery. It supplied the entire dorsal surface of the left uterine horn and anastomosed with the uterine branch of the ovarian artery and uterine branch of the vaginal artery. Sixth, a connecting branch was present between the right uterine artery and the uterine branch of right vaginal artery in 16.7% of triplets. Seventh, a connecting branch was present between the left uterine artery and the uterine branch of left vaginal artery in 16.7% of triplets. These adaptations were observed in triplet pregnancies mainly at later stages. This physiological adaptation to multiple pregnancies has not been noted before in the literature. This may be due to lack of anatomical studies on uterine vessels during pregnancy in all animals. These adaptations presumably serve to provide an additional blood supply to the uterus in the case of multiple pregnancies due to the increasing demand of the growing fetuses.

No difference was observed in the origin and distribution of the ovarian, uterine, and vaginal arteries between pregnant and nonpregnant does; however, differences in these aspects existed within specimens from pregnant and/or non-pregnant does. The ovary is supplied by the ovarian artery. The infundibulum and the area of the uterine tube adjacent to the ovary are supplied by the uterine tube branch of the ovarian artery. The isthmus and area adjacent to the uterus are supplied by the uterine branch of the ovarian artery. The supply of the ampulla is mainly via the uterine tube branch, but in some cases via the uterine branch of the ovarian artery.

The uterus is supplied by branches of the ovarian arteries, uterine arteries, and vaginal arteries. The supply of different parts of the dorsal and ventral surfaces of the uterus is provided in Figure 12. This will be helpful to other researchers performing studies on the caprine reproductive organs. The dorsal and the ventral surfaces of the uterine tip and the adjacent area are supplied by the uterine branches of the ovarian arteries, which anastomose with branches of the uterine artery. The distribution of the caudal and cranial branches of the uterine artery was consistent in most of the specimens; however, in some specimens the cranial or caudal branch dominated to supply most of the dorsal or ventral surface, respectively, of the ipsilateral uterine horn. The dorsal and ventral surfaces of the area between the middle portion of the uterine horn to the tip were supplied mostly by the branches of the cranial branch of the uterine artery. The supply of the ventral surface of the middle area of the uterine horn was mainly by branches of the caudal branch of the uterine artery. The dorsal surface of the middle portion of the uterine horn was supplied about equally by either the cranial or caudal branch of the uterine artery. The ventral surface of the caudal part of the uterine horn was supplied by the caudal branch of the uterine artery in all specimens studied. The dorsal surface of the caudal part of the uterine horn was supplied by the caudal branch of the uterine artery in most specimens. The dorsal and ventral surfaces of the uterine body were supplied by both the caudal branches of the uterine arteries and uterine branches of the vaginal arteries.

The anastomosis between branches of the right and left uterine arteries introduces the possibility of mixing of substances between the two horns. Substances produced in or introduced into one horn can possibly move to the other horn, i.e., substances produced in a gravid horn may move to the nongravid horn or vice versa.

The uterine branch(es) of the right and/or left vaginal arteries anastomoses with branches of one or both caudal branches of the uterine arteries on the ventral surface and/or dorsal surfaces of the uterine body and caudal part of the uterine horn. The anastomosis was not ipsilateral in all cases; it was with the contralateral artery and/or both arteries (right and left) in some specimens. The size of the right and left vaginal arteries was not equal in some specimens; one or the other dominated to supply both the ventral and dorsal surfaces of the uterine body, while the other supplied just one surface.

Acknowledgements

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. LITERATURE CITED

The authors thank their colleague Dr. Marcelo Gomez for help and especially for the initial drawing of Figure 12, as well as John Strauss and Pam Arnold at the College of Veterinary Medicine, Virginia Tech, for excellent technical support. Supported by the Egyptian Cultural and Educational Bureau.

LITERATURE CITED

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. LITERATURE CITED
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