Veterinary Gross Anatomy-II

FOURTH VENTRICLE

• The fourth ventricle or rhomboid fossa is the cavity of the hindbrain. It communicates behind with the central canal of the spinal cord and in front with the third ventricle through the cerebral aqueduct.
• The floor is formed by the medulla and the pons. The posterior part narrows to a point at its communication with the central canal and this part is termed the calamus scriptorius.
• The lateral wall is formed by the restiform body and anterior cerebellar peduncles.
• The roof is formed by the vermis and the anterior and posterior medullary vela.
• The fourth ventricle communicates, with the cisterna magna by a central and two lateral microscopic foramina Megendie, Key and Retzius respectively in the posterior medullary velum.