XB-ART-57669J Morphol January 1, 2021; 282 (3): 368-377.
Microvascular anatomy of the urinary bladder in the adult African clawed toad, Xenopus laevis: A scanning electron microscope study of vascular casts.
We studied urinary bladders of adult male and female Xenopus laevis using light microscopy of stained tissue sections and scanning electron microscopy (SEM) of vascular corrosion casts (VCCs). Results showed that bilaterally a vesical artery branched off the femoral artery. At the dorso-lateral serosal surface of the body of the bladder each artery splitted within a short distance into up to five smaller arteries that supplied body and neck regions. Arteries gave off short and long terminal arterioles, which fed the mucosal capillary meshwork. Long terminal arterioles followed dimensional changes of the bladder, while short ones anchored the capillary network to the arterial system. Capillary mesh sizes and shapes varied according to the filling state of the urinary bladder. In the highly to moderately distended (filled) bladder, capillaries were rather straight or undulated only slightly, in the contracted (emptied) bladder they undulated strongly and lay side by side. Postcapillary venules formed by two equally sized capillaries or from capillaries, which serially drained into a small postcapillary venule. Vesical venules formed a large dorsal vesical and a varying number of smaller lateral and ventral vesical veins. The dorsal vesical vein drained either directly or via the posterior hemorrhoidal vein into the common pelvic vein. Lateral and ventral vesical veins also drained into the latter. The vascular patterns found were discussed in respect to the bladder spatial movements during distention (filling) and relaxation (emptying). Furthermore, it was hypothesized that an extensively filled bladder could compress the overlaying abdominal vein forcing part of the blood otherwise drained towards the liver to be detoured via the renal portal veins to the kidneys.
PubMed ID: 33368528
PMC ID: PMC7898512
Article link: J Morphol
Species referenced: Xenopus laevis
Genes referenced: ncoa5
Article Images: [+] show captions
|FIGURE 1 Xenopus laevis, urinary bladder (ub) of an adult individual. (a) Ventral view at the spherical body of the exposed organ. Neck region is hidden. Stereomicroscopy. av abdominal vein, fb fat body, li large intestine, re rectum, ub urinary bladder. (b) Light microscopic structure of the wall of the bladder. Detail view. Paraplast embedded tissue section (7 μm). Goldner's trichrome stain. Note the comparatively thick transitional epithelium (ep). bsm bundle of smooth muscle cells, c capillary, lp lamina propria, lu lumen of bladder, mu muscularis, se serosa, v vein|
|FIGURE 2 Xenopus laevis, vascular anatomy of the urinary bladder (ub) in an adult individual. (a) Gross arterial supply and venous drainage of a moderately distended (filled) bladder displaying a spherical body (bo) and a funnel‐like neck (ne). Vascular corrosion cast. Lateral view. Scanning electron micrograph. Anterior is to the left, dorsal is at top. Note the abdominal vein (av) which slightly notches the ventral bladder surface (asterisk). Arrow points at a lateral vesical artery supplying the bladder neck region. (b) Vascular anatomy of a contracted (emptied) bladder. Ventral view. The bladder is dislocated to the left side. Anterior is to the right. Origin, course, and branching pattern of the vesical artery (va) can be seen. Inset: Origin of the vesical artery (va) from the femoral artery (fa). Note the prominent flow divider (arrows). cia common iliac artery. (c) Coiling of vesical arteries (va) in a contracted bladder. av abdominal vein, cpv common pelvic vein, phv posterior hemorrhoidal vein, ia ischiadic artery, iv ischiadic vein, ki kidney, li large intestine, pcv posterior caval vein, re rectum, rpv renal portal vein, ut uterus (posterior portion of oviduct)|
|FIGURE 3 Xenopus laevis, branching patterns and courses of vesical arteries (va) as seen from the serosal side. (a) Branching pattern of the vesical artery in a moderately distended bladder. Anterior is at the top. Interbranching distances of the vesical artery (va) are small. Branches course towards the apex, the lateral surfaces, and the neck region of the bladder (arrows). (b) Same as (a) but in a stronger distended bladder. (c) Arterial and venous patterns of the ventral neck region of the bladder. (d, e) Microvascular bed of distended (filled) bladders. Terminal vesical arterioles feed single capillary‐sized vessels (short arrows) overlaying mucosal capillaries (c). Note different calibers and lengths of terminal arterioles (long white arrows) and an arterial sphincter (long black arrow) in (e). (f) Microvascular bed of a contracted (empty) bladder. Note slightly undulating vesical arteries (va) and terminal vesical arterioles (arrows). Strongly undulating capillaries (c) form small meshes. Postcapillary venules meander (asterisks). cpv common pelvic vein, lvv lateral vesical vein, lu lumen of urinary bladder, rpv renal portal vein, ub urinary bladder, vv vesical vein, vvv ventral vesical vein|
|FIGURE 4 Xenopus laevis, patterns of mucosal vessels of the urinary bladder as seen from the mucosal side. (a) Distended bladder. Most mesh capillaries (c) are straight, a few capillaries only undulate. A maximum of three layers of vessels (capillaries, venules or small veins, arterioles, or small arteries) is seen. A local convolution of small vesical arteries (sva) is shown (encircled area). Arrow points at a bifurcation of a vesical artery with daughter vessels laying close aside. (b) Similar to (a), but less distended bladder displaying more undulating capillaries (c) and postcapillary venules (asterisks). Note small (short arrow) and large branching angles (long arrow) of a vesical artery (va). (c) Contracted (empty) bladder. Note strong undulating capillaries (c) and postcapillary venules (asterisks). (d) Strongly contracted bladder displaying narrow spaced mesh capillaries of dome‐shaped mucosal folds (d). svv small vesical vein, vvv vesical venule|
|FIGURE 5 Xenopus laevis, drainage of dorsal and dorso‐lateral areas of the urinary bladder. Dorsal view at the bladder shown in Figure 2(a). anterior is to the left. Asterisks mark wall areas where incomplete filling of the vasculature occurred. Note four vesical veins (vv) which form the dorsal vesical vein (dvv). Va vesical artery. Inset 1: Formation of a small vesical venule (svv) from postcapillary venules (pcvv). Inset 2: Postcapillary venule (pcvv) draining into a small vesical venule (svv). Note the relation of the calibers of the venules. Inset 3: Capillary (c) draining into a small vesical vein (svv). Inset 4: Undulating capillaries (c) drain in series bilaterally into a postcapillary venule (pcvv)|
|FIGURE 6 Xenopus laevis, venous drainage of the urinary bladder (ub). (a) Ventro‐caudal view at the large veins running aside the neck region of the bladder. Incomplete specimen. Anterior is at the top, posterior is at the bottom. A lateral vesical vein (lvv) is seen to join the right common pelvic vein (cpv) at its caudal aspect (arrow). (b) Vascular anatomy of the ventral neck region of the bladder after removal of the common pelvic veins (cpv). Anterior is at the left, posterior is to the right. A lateral vesical vein (lvv) is joined by a smaller one (arrow) to finally drain into right or left common pelvic vein (not shown). (c) Vascular anatomy of the cloacal region. Only remnants of the mucosal capillary bed (c) of the dorsal wall of the bladder are left. Note the dorsal vesical vein (dvv) which drains via the posterior hemorrhoidal vein (hv) into the left common pelvic vein (cpv). At its entrance at the caudal margin of the common pelvic vein, the posterior hemorrhoidal vein is broken (arrows). (d) Venous valves of the ischiadic veins (iv). Ventro‐caudal view. In the orthogradely filled large valve, the leaflet structure is clearly replicated (long arrows). Note small valves where retrograde resin flow was stopped at the valves (short arrows). Dashed arrows mark direction of blood flow, asterisks mark slit‐like opening of bladder into cloaca. av abdominal vein, cb conductive bridge, cl cloaca, rpv renal portal vein, va vesical artery|
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