Cerebral microvascular architecture in the common tree shrew (Tupaia glis) revealed by plastic corrosion casts.

The vascularization of the cerebrum (cerebral cortex and basal ganglia) in the common tree shrew (Tupaia glis) has been studied in detail using vinyl injection and vascular corrosion cast/SEM techniques. It is found that the arterial supply of the cerebral cortex are from cortical branches of the middle cerebral artery (MCA) and of the anterior cerebral artery (ACA). These arteries are in turn branches of the internal carotid artery (ICA). In addition, the cerebral cortex receives the blood from the cortical branches of the posterior cerebral artery (PCA) that originates from the basilar artery (BA). These cortical arteries gives rise to rectilinear orientated intracortical arteries that are divided into dense capillary networks to supply the cerebral cortex. The capillary networks drain the blood into intracortical veins and then into the tributaries of major superficial cerebral veins. The basal ganglia (caudate and lentiform nuclei) are supplied by central or perforating branches of the ACA and MCA. These central or medullary arteries give rise to arterioles that ramify into dense capillary plexuses. The venous blood from both nuclei drains into venules and finally into the tributaries of internal cerebral veins. It is obvious that on the ventral aspect, the diameter of the lateral striate artery (LSA) and of the penetrating arterioles from the MCA are much smaller than that of the MCA. These arterioles have few side branches while the peripheral branches of the superficial cerebral arteries exhibit several series of branches that are gradually reduced in diameter before branching into intracortical arteries. This could be one of the reasons why the rupture of cerebral arteries in man mostly occurs in the those originating from the ventral surface rather than from the dorsolateral surface.

Angioarchitecture of the coeliac sympathetic ganglion complex in the common tree shrew (Tupaia glis).

The angioarchitecture of the coeliac sympathetic ganglion complex (CGC) of the common tree shrew (Tupaia glis) was studied by the vascular corrosion cast technique in conjunction with scanning electron microscopy. The CGC of the tree shrew was found to be a highly vascularised organ. It normally received arterial blood supply from branches of the inferior phrenic, superior suprarenal and inferior suprarenal arteries and of the abdominal aorta. In some animals, its blood supply was also derived from branches of the middle suprarenal arteries, coeliac artery, superior mesenteric artery and lumbar arteries. These arteries penetrated the ganglion at variable points and in slightly different patterns. They gave off peripheral branches to form a subcapsular capillary plexus while their main trunks traversed deeply into the inner part before branching into the densely packed intraganglionic capillary networks. The capillaries merged to form venules before draining into collecting veins at the peripheral region of the ganglion complex. Finally, the veins coursed to the dorsal aspect of the ganglion to drain into the renal and inferior phrenic veins and the inferior vena cava. The capillaries on the coeliac ganglion complex do not possess fenestrations.

Microvascularization of the common tree shrew (Tupaia glis) superior cervical ganglion studied by vascular corrosion cast with scanning electron microscopy.

Microvascularization of the superior cervical ganglion (SCG) of the common tree shrew (Tupaia glis) was investigated by the vascular-corrosion-cast technique in conjunction with scanning electron microscopy. It was found that the SCG of the tree shrew is a highly vascularized organ. It receives arterial blood from branches of the external and common carotid arteries which enter the rostral and caudal portions of the ganglion. These arteries give rise to a subcapsular capillary plexus before branching off to form a group of densely packed intraganglionic capillaries. Moreover, the intraganglionic capillaries tend to follow a tortuous course that is essentially parallel to the longitudinal axis of the ganglion, and they form anastomoses with each other. In addition, the intraganglionic capillaries are also connected to a subcapsular capillary plexus. The capillaries of the SCG converge into venules and collecting veins which subsequently drain rostrally and caudally into the systemic veins. However, neither a pattern of blood vessels resembling glomeruli nor a portal-like intraganglionic microcirculation was observed.