2. Forth ventricle 1- Floor (rhomboid fossa ) 2- Roof 3- Borders

4. Floor of fourth ventricle 1- Median sulcus. calamus scriptorius 2- Medial eminence 3- Facial colliculus 4- Hypoglossal triangle 5- Vagal triangle 6-Funiculus separans 7- Area postrema 8- Sulcus limitance 9-Sup. and inf. fovea 10-Locus ceruleus/ substantia ferrugina 11- Vestibular area 12- Acoustic tubercle

8. Funiculus separans(32)

9. Circumoventricular organs

11. Roof of Forth ventricle 1- superior medullary velum 2- inferior medullary velum

12. superior medullary velum inferior medullary velum

13. superior medullary velum