Cerebral Hemisphere White Matter: Commisural Fibers

Question 1

Commissure

Answer 1

Band of white matter connecting part of CNS on one side with the same part of opposite side crossing middle line helping to coordinate activities of both hemispheres

Question 2

5 major commissures

Answer 2

1. Corpus callosum
2. Anterior commissure
3. Posterior commissure
4. Hippocampal commissure
5. Habenular commissure

Question 3

Corpus callosum

Answer 3

Arched mass of fibers 10 cm long connecting nearly all area of both cerebral hemispheres except anterior parts of temporal lobes which are connected by anterior commissure

Question 4

Corpus callosum site

Answer 4

Lies at median longitudinal fissure bottom nearer to frontal lobe than occipital lobe

Question 5

Corpus callosum contents

Answer 5

1. Genu
2. Rostrum
3. Body (trunk)
4. Splenium

Question 6

Blood supply corpus callosum

Answer 6

All supplied by anterior cerebral anterior except splenium which is supplied by posterior cerebral artery

Question 7

Genu site

Answer 7

Most anterior part of corpus

Question 8

Genu attachment

Answer 8

Its posterior aspect gives attachemnet to septum pellucidum in median plane and forms anterior limit of lateral ventricle anterior horn each side

Question 9

Genu fibers

Answer 9

Fibers passing through curve forwards and medial into frontal lobe forming forceps anterior (minor) connecting prefrontal region on either side

Question 10

Rostrum site

Answer 10

Connected to optic chiasma by grey matter sheet, lamina terminalis

Question 11

Rostrum attachment

Answer 11

Its upper surface is attached to septum pellucidum in median plane and forms anterior horn floor of lateral ventricle on each side

Question 12

Rostrum fibers

Answer 12

Fibers passing through connect orbital surfaces of both frontal lobes

Question 13

Body site

Answer 13

Extends from genu to splenium lying at median longitudinal fissure bottom

Question 14

Body attachment

Answer 14

1. In median plane, it’s lower surface gives attachment to septum pellucidum in front
2. It’s closely related to fornix body behind
3. On each side, it’s lower surface forms roof of anterior horn and central part lateral ventricle

Question 15

Body fibers

Answer 15

Fibers passing through connect both parietal lobes and posterior parts of both frontal lobes

Question 16

Splenium site

Answer 16

Most posterior part of corpus callosum

Question 17

Splenium fibers

Answer 17

1. Fibers passing through curve backwards and medial into occipital lobe forming forceps posterior (major) causing bulging into posterior horn medial wall of lateral ventricle, bulb of posterior horn
2. Some of the fibers of splenium and body posterior part form roof and lateral wall of lateral ventricle posterior horn as they pass lateral then downwards into occipital and temporal lobes, constituting tapetum

Question 18

Anterior commissure

Answer 18

Small round bundle of fibers crossing middle line within lamina terminalis forming part of 3rd ventricle anterior wall

Question 19

Anterior commissure fibers

Answer 19

Some of its fibers join olfactory tract lateral root but the remainder pass to temporal lobe cortex of….
It connects temporal lobes,….

Question 20

Hippocampal commissure

Answer 20

Crosses midline between bodies and 2 cura of fornix, connecting hippocampi of both sides

Question 21

Posterior commissure

Answer 21

Slender bundle of fibers lying in pineal stalk lower aspect connecting right and left:
1. Superior colliculi
2. Pretectal nuclei
3. Medial longitudinal bundles

Question 22

Habenular commissure

Answer 22

Bundle of fibers lying in pineal stalk upper aspect above pineal recess and posterior commissure connecting right and left Habenular nuclei