It is the specific thalamic projection nucleus for the auditory system, and it projects axons by way of the internal capsule to the neocortex of the temporal lobe. This nucleus protrudes from the caudolateral aspect of the thalamus and extends caudally beside the mesencephalon (see Figs 2-5, 2-6). This brachium is located on the lateral side of the mesencephalon and courses rostrally to the medial geniculate nucleus of the thalamus. Cerebral peduncles (3.27B)Īlexander de Lahunta DVM, PhD, DACVIM, DACVP, Eric Glass MS, DVM, DACVIM (Neurology), in Veterinary Neuroanatomy and Clinical Neurology (Third Edition), 2009 Thalamocortical PathwayĪxons in the conscious projection pathway arise primarily from cell bodies in the caudal colliculus that project rostrally in the brachium of the caudal colliculus. The role of the midbrain in the control of pupil size is discussed in Clinical Box 3.11. The inferior colliculi are part of a complex pathway between the cochlea and primary auditory cortex. involuntary turning towards a novel or unexpected stimulus). The superior colliculi (collectively: the optic tectum) give rise to the tectospinal tracts which co-ordinate head, neck and eye movements during orientation reflexes (e.g. The tectum bears four smooth elevations or colliculi (Latin: colliculus, little hill). The large portion in front of the aqueduct (making up half of the midbrain on each side, excluding the tectum) consists of the left and right cerebral peduncles. The small part of the midbrain dorsal to the aqueduct is the tectum or ‘roof’ of the midbrain (Latin: tectum, roof). It contains the cerebral aqueduct which runs between the third ventricle (above) and the fourth ventricle (below). The midbrain is the most rostral part of the brain stem ( Figs 3.26 and 3.27). Paul Johns BSc BM MSc FRCPath, in Clinical Neuroscience, 2014 Midbrain Catheterization may be difficult when inflammation is severe. Thick mucopurulent discharge or even some bloody discharge may be present ( Figure 33-13). Seminal vesiculitis (vesicular gland adenitis) sometimes is characterized by inflammation of the entire ejaculatory duct, which may appear red and swollen ( Figure 33-12, A and B). Direct flushing of the vesicular gland is better accomplished by placing a catheter with an inflatable cuff. 1 It also helps to guide the scope head into the seminal vesicle (catheter diameter should be 8 to 9 mm) ( Figures 33-10 and 33-11). The catheter is inserted into the instrument channel of the videoendoscope and serves as a route for direct aspiration of fluid or instillation of pharmacologic solutions for direct treatment. The vesicular glands can be easily catheterized using a small-diameter (3 to 5 French), flexible polyethylene catheter or a stylet ( Figure 33-9). Rectal massage of the prostate may improve visualization of these ducts.
The prostatic ducts are smaller and disseminated laterally and proximally to the colliculus seminalis and are difficult to see unless the stallion has been stimulated. Ejaculatory duct hyperplasia has been described in some stallions, but its significance is not clear. Occasionally, the openings of the ductus deferens and the vesicular glands can be individually identified. Visualization of the ejaculatory ducts may be difficult initially if they are collapsed. 4, 14, 15 The ejaculatory ducts can be identified on the lateral aspect of these structures and correspond to the area where both the ductus deferens and the vesicular gland open ( Figure 33-8). The colliculus seminalis is situated dorsally approximately 3 to 4 cm cranial to the ischial arch and is recognized as a prominent papilla. AHMED TIBARY, in Current Therapy in Equine Reproduction, 2007 Examination of the Colliculus Seminalis
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