Objective: This study presents the microvasculature of the horse iris, ciliary process, retina, and choroid and discusses the functional significance of the vasculature. Procedure: Seven horses were used for this stud...Objective: This study presents the microvasculature of the horse iris, ciliary process, retina, and choroid and discusses the functional significance of the vasculature. Procedure: Seven horses were used for this study. The ocular vascular system was injected with methylmethacrylate resin via the carotid artery, and the vascular corrosion casts were observed using a scanning electron microscope. Results: The iridial vessels showed a wavy course. The ciliary process was supplied by 2 arterial routes: the iridial and ciliary arterial circles. The subjects displayed a paurangiotic retina with retinal vessels extending only a short distance around the disc. The retinal arterioles and venules ran in closely related pairs, and the capillaries formed hairpin loops. No central retinal artery was seen in the equine eyes examined. The choriocapillaris in the avascular retina was arranged in honeycomb hexagon lobules and formed a more densely packed network than that in the vascular retina. There were 2 distinct venous drainage systems in the horse choroid: the vortex veins and the posterior ciliary veins. The vortex vein ampulla was flattened and showed a slit-like lumen at the merge site with the ophthalmic vein. The vortex veins demonstrated a marked constriction before leaving the eye. Discussion: The 2 choroidal drainage systems may compensate each other in event of occlusion. The ampulla and the constriction in the vortex veins may act as a valve regulating the blood flow to keep the eye at an optimum size and the intraocular pressure within the normal physiological range.展开更多
The microvasculature of footpads in the dog and domestic cat was investigated using histology and scanning electron microscopy of corrosion casts. Methylmethacrylate resin vascular casts for scanning electron microsco...The microvasculature of footpads in the dog and domestic cat was investigated using histology and scanning electron microscopy of corrosion casts. Methylmethacrylate resin vascular casts for scanning electron microscopy, Indian ink injected whole mount and histological specimens were each prepared, in a series of 16 limbs of 4 adult dogs and 12 limbs of 3 adult domestic cats. The network of blood vessels in the dog paw pad appears to have an intricate pattern, especially with regard to venous outflow forming a peri-arterial venous network. Numerous arteriovenous anastomoses (AVAs) were found in the canine dermis. While, that of the domestic cat had less complex vascular pattern in the footpad without the peri-arterial venous network. AVAs were observed sporadically in the feline dermis. The peri-arterial venous network in the paw pad formed a countercurrent heat exchanger in dogs. When the foot pad is exposed to a cold environment in dogs, the countercurrent heat exchanger serves to prevent heat loss by re-circulating heat back to the body core, adopting an inhospitable environment. AVAs also play a role in regulating the body temperature. A lack of the peri-arterial venous network and few AVAs appear to make felines more prone to suffer from a cold condition than canines.展开更多
Background There have been no detailed reports of the three-dimensional structure and the relationship between the external and internal vascularizations observed successively for a long duration in the rat fetus, alt...Background There have been no detailed reports of the three-dimensional structure and the relationship between the external and internal vascularizations observed successively for a long duration in the rat fetus, although many authors have studied the vascular morphology of the developing brain. This study examined the three-dimensional structure of both the external and internal vascularizations of the prenatal rat telencephalon from embryonic days 12 (E12) to 20 (E20).Method A microvascular casting method for scanning electron microscopy (SEM) was used in this study, along with vascular staining using gold-gelatine solution-autometallography (GGS-AMG) after intravascular injection of colloidal gold, as well as hematoxylin-eosin ( HE) staining for paraffin embedded specimens.Results In GGS-AMG stains, E16 fetuses had a few short perforating cortical blood vessels (SPCVs); E17 fetuses had long perforating cortico-medullary vessels (LPCVs). Older fetuses had specific patterns of vascular networks in the cortex and the deeper subcortical part of the telencephalon. In the cortex, fine longitudinal blood vessels were connected by transverse channels. The deep telencephalon had fine blood vessels running in all directions. Using SEM, the external vascularization was already visible in E12 fetuses as arborizations of arterial branches, forming a mesh of fine vascular networks covering the telencephalon. A coralliform fine venous plexus was observed in the external vascularization of E16 fetuses. There were ring-like anastomoses and bud-like protrusions in the network of small blood vessels, most likely the angiogenesis of fetal vessels. From E12 to E16, an immature and incomplete internal vascularization began to appear. There were short blood vessels with ballooned terminals branching from the external vascularization. They penetrated the brain tissue to form networks in the superficial layer, comparable to SPCVs. In E17 to E20 fetuses, tortuous venous branches, straight arterial blood vessels, and a fine network of 展开更多
文摘Objective: This study presents the microvasculature of the horse iris, ciliary process, retina, and choroid and discusses the functional significance of the vasculature. Procedure: Seven horses were used for this study. The ocular vascular system was injected with methylmethacrylate resin via the carotid artery, and the vascular corrosion casts were observed using a scanning electron microscope. Results: The iridial vessels showed a wavy course. The ciliary process was supplied by 2 arterial routes: the iridial and ciliary arterial circles. The subjects displayed a paurangiotic retina with retinal vessels extending only a short distance around the disc. The retinal arterioles and venules ran in closely related pairs, and the capillaries formed hairpin loops. No central retinal artery was seen in the equine eyes examined. The choriocapillaris in the avascular retina was arranged in honeycomb hexagon lobules and formed a more densely packed network than that in the vascular retina. There were 2 distinct venous drainage systems in the horse choroid: the vortex veins and the posterior ciliary veins. The vortex vein ampulla was flattened and showed a slit-like lumen at the merge site with the ophthalmic vein. The vortex veins demonstrated a marked constriction before leaving the eye. Discussion: The 2 choroidal drainage systems may compensate each other in event of occlusion. The ampulla and the constriction in the vortex veins may act as a valve regulating the blood flow to keep the eye at an optimum size and the intraocular pressure within the normal physiological range.
文摘The microvasculature of footpads in the dog and domestic cat was investigated using histology and scanning electron microscopy of corrosion casts. Methylmethacrylate resin vascular casts for scanning electron microscopy, Indian ink injected whole mount and histological specimens were each prepared, in a series of 16 limbs of 4 adult dogs and 12 limbs of 3 adult domestic cats. The network of blood vessels in the dog paw pad appears to have an intricate pattern, especially with regard to venous outflow forming a peri-arterial venous network. Numerous arteriovenous anastomoses (AVAs) were found in the canine dermis. While, that of the domestic cat had less complex vascular pattern in the footpad without the peri-arterial venous network. AVAs were observed sporadically in the feline dermis. The peri-arterial venous network in the paw pad formed a countercurrent heat exchanger in dogs. When the foot pad is exposed to a cold environment in dogs, the countercurrent heat exchanger serves to prevent heat loss by re-circulating heat back to the body core, adopting an inhospitable environment. AVAs also play a role in regulating the body temperature. A lack of the peri-arterial venous network and few AVAs appear to make felines more prone to suffer from a cold condition than canines.
文摘Background There have been no detailed reports of the three-dimensional structure and the relationship between the external and internal vascularizations observed successively for a long duration in the rat fetus, although many authors have studied the vascular morphology of the developing brain. This study examined the three-dimensional structure of both the external and internal vascularizations of the prenatal rat telencephalon from embryonic days 12 (E12) to 20 (E20).Method A microvascular casting method for scanning electron microscopy (SEM) was used in this study, along with vascular staining using gold-gelatine solution-autometallography (GGS-AMG) after intravascular injection of colloidal gold, as well as hematoxylin-eosin ( HE) staining for paraffin embedded specimens.Results In GGS-AMG stains, E16 fetuses had a few short perforating cortical blood vessels (SPCVs); E17 fetuses had long perforating cortico-medullary vessels (LPCVs). Older fetuses had specific patterns of vascular networks in the cortex and the deeper subcortical part of the telencephalon. In the cortex, fine longitudinal blood vessels were connected by transverse channels. The deep telencephalon had fine blood vessels running in all directions. Using SEM, the external vascularization was already visible in E12 fetuses as arborizations of arterial branches, forming a mesh of fine vascular networks covering the telencephalon. A coralliform fine venous plexus was observed in the external vascularization of E16 fetuses. There were ring-like anastomoses and bud-like protrusions in the network of small blood vessels, most likely the angiogenesis of fetal vessels. From E12 to E16, an immature and incomplete internal vascularization began to appear. There were short blood vessels with ballooned terminals branching from the external vascularization. They penetrated the brain tissue to form networks in the superficial layer, comparable to SPCVs. In E17 to E20 fetuses, tortuous venous branches, straight arterial blood vessels, and a fine network of
