**5.1 Arterial blood supply**

The arterial blood supply is provided by three different sources: the *uterine artery*, the *utero-ovarian artery,* and the *vaginal arteries.*

a. *The uterine artery* is the primary blood supply source for a uterus in a reasonable condition. During pregnancy, the utero-ovarian artery becomes the second significant source, doubling its diameter. In non-pregnant women, the diameter of the left uterine artery is 1.6 mm, and for the right artery, it is 1.4 mm. The diameter of the uterine artery may vary for large uteri, up to 5 mm.

The origin of the uterine artery can be encountered most often in a common trunk with the umbilical artery, which arises as to the terminal branch from the previous division of the hypogastric artery. However, there is also the anatomic variant of direct origin from the hypogastric artery. From its origin, the uterine artery follows a 3–5 cm intrapelvic trajectory, approaching the cervix at a constant distance of approximately 2–2.5 cm without coming into contact.

The level where the uterine artery enters the uterine body, regardless of the shape or size of the uterus, corresponds to the level of the internal cervical orifice (**Figure 6**).

In its trajectory, the uterine artery has three distinct segments: *a parietal segment*, a *transversal one*, and a *lateral-uterine* one*.*

In the *parietal segment*, the uterine artery is in contact with the pelvic wall and is located on the side of the ureter, which crosses it in places, underneath and medially. In this segment, the artery is rectilinear and is accompanied by the uterine veins, which can be injured during maneuvers to identify its original ligation.

The *transversal segment* or (intra-parametrial segment) of the uterine artery is approximately 3 cm long. In this segment, the artery has the most important relation to the ureter, which is located outside of it. There is a cleavage space between

**Figure 6.**

*The point where the uterine artery reaches the uterus is constant at the level of the internal cervical orifice. ICO = internal cervical orifice, UP = uterine point. 1 = main uterine artery, 2 = ascending branch of the uterine artery, three = descending branches of the uterine artery. 4 = Beliaeva triangle.*

the ureter and the artery. At this level, the uterine artery emits a nutritional branch for the corresponding ureteral segment. During maneuvers to release the uterus in case of radical hysterectomy, this branch "holds" the ureter in the surgeon's attempt to move it caudally. The ligation or coagulation of this vessel is necessary because subserosa ureteral hematoma may appear, which can compromise the viability of the ureter on this segment.

The uterine artery reaches the uterus in a triangular zone near the isthmus (Beliaeva triangle) situated at the base of the broad ligaments at three o clock for the right side and nine o clock for the left side (from the vaginal point of view). The descending uterine artery supplies the isthmus, cervix, and upper vagina. The ascending uterine artery supplies the body of the uterus. The ascending uterine artery is tortuous and gives rise to 10–12 arcuate arteries that course between the outer and middle thirds of the myometrium.

The crossing point of the uterine artery with the ureter is located sideways, approximately 20 mm away from the cervix and 10–12 mm cranially from the lateral vaginal fornix. At this level, there are two venous currents, one in front and another in the back of the ureter, which is predisposed to bleed during maneuvers to unroof the parametrial ureter (**Figure 7**).

The *lateral-uterine segment* of the uterine artery starts from the crossing point and emits an *ascending branch* that borders the whole uterine edge up to the horn, as well as a *descending branch*, from which the cervicovaginal (superior vaginal branch) arteries arise. The ascending branch is tortuous and intimately adhered to the uterine edge-front-side and is accompanied by the uterine veins.

Between the right and left sides of the uterine body, the arcuate arteries are anastomosed by collateral and small, direct branches. At the uterine fundus, approximately 15 mm away from the insertion of the tube, the ascending uterine artery divides into two branches: *the fundic artery*, which supplies the fundus of the uterus on each side, and the *internal tubal artery*, which is routed under the utero-ovarian ligament, into the mesosalpinx.

a. *The ovarian artery* included in the *infundibulopelvic* ligament*,* after crossing the external iliac artery and vein, emits two branches, a tubal and an ovarian one, which is anastomosed between them by short arteries. The uterine artery provides the primary blood flow, but in particular conditions, such as after uterine embolization or in pregnancy, more than 80% of blood flow can be provided by the ovarian artery.

*Perspective Chapter: Total Vaginal Hysterectomy for Unprolapsed Uterus DOI: http://dx.doi.org/10.5772/intechopen.101383*

#### **Figure 7.**

*Arterial supply of uterus and vagina. 1 = arterial trunk of hypogastric artery, 2 = Main trunk of the uterine artery, 3 = the ascending branch of the uterine artery, 4 = the descending branch of uterine artery (superior vaginal artery), five = inferior vaginal artery, 6 = umbilical vesical artery, 7 = ureteral branches from the uterine artery, 8 = middle hemorrhoidal artery, nine = ovarian artery, ten = ovarian arch between ovarian and uterine branches, 11 = tubal arch between ovarian and uterine branches, 12 = fundal branch of the uterine artery, 13 = arcuate arteries from right side, 14 = anastomotic branch between the uterine artery and ovarian arch, 15 = funicular branch (round ligament) artery.*

	- A branch from the uterine artery.
	- The vaginal artery.
	- The middle hemorrhoidal artery.

The source of the uterine artery is composed of vesicovaginal and cervicovaginal branches and ensures the blood flow for the upper part of the vagina. The correct vaginal artery (lower vaginal artery or large vaginal artery) originates from the hypogastric artery. The artery from both sides anastomose in the midline and forms the longitudinal artery from the cervix to the vulva named the *azygos artery of the vagina*. The hemorrhoidal artery emits some branches for the posterior side of the vagina.


The bilateral ligature of the anterior trunk of hypogastric arteries cannot stop the blood flow into the pelvis. Two primary sources ensure arterial collateral circulation of the pelvis:

*Branches of the hypogastric artery*


*Systemic circulation*


#### **5.2 Venous blood supply**

Venous blood from the uterine body comes from the veins located in the thickness of the myometrium, which is venous sinuses with reduced endothelial cover. Venous blood drains into two collecting veins on each side of the uterus, with anastomoses in between. The collateral venous blood supply is significant concerning the alternative route for blood flow in case of significant obstruction of main venous branches.

Collateral venous circulation of the uterus can be done in three main ways:


The venous blood supply of the vagina consists of veins that come from each side of the vagina and anastomose on the median line on the same path as the azygos arteries. The blood flow is oriented to uterine veins at the level of the cervix.

Veins are mainly located on the sides of the vagina and anastomose each other at the extremities of the vaginal canal. In the middle region of the vagina, anastomoses are carried out in the azygous arteries draining the blood to the uterine veins at the level of the cervix. The uterine veins are anastomosis with the average hemorrhoidal veins, which, in turn, communicate with the upper hemorrhoids, forming at this level a porta-cave anastomose. The *long vaginal vein* is the artery satellite of the same name when it exists, and it flows into the hypogastric vein.
