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Let's talk a little bit about

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the olfactory tracts or dendrites,

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that continue in the tract and terminate in the

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olfactory trigone and tuberculum,

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in correspondence with the anterior perforated substance,

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which can be found just anterosuperior

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to the pituitary gland and fossa.

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So, the perforated substance is going to be right here.

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The tuberculum is located right here, so I'm going to draw

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in the olfactory bulb and tract containing its dendrites lying

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directly over the gyrus rectus between

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it and the cristal gally.

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It comes back, and it is going to divide

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into five structures here in a minute.

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This little sulcus right here is the olfactory sulcus.

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This is the medial olfactory gyrus.

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This is the orbital frontal gyrus and the sulcus

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separating them. Now inside are our dendrites.

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I'm going to make them pink, and as they come back,

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they're going to split into five divisions.

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One is the lateral olfactory stria that goes off to the side.

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See, here's our trigonal area right here, this little shelf.

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And then another one is going to go obliquely to the amygdala.

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This is known as the diagonal band or diagonal band of Broca.

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And I will mark the amygdala as kind of a round,

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puffy little structure right here.

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Then a pretty vestigial, small intermediate stria.

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We've got a medial stria, medial olfactory stria.

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And then a little bit higher up, coursing obliquely, merging

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with the anterior commissure, which we don't see on this

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particular cut, is the commissural communication

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of these dendrites.

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So now

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once we've hit the amygdala,

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something else interesting happens.

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You've got another group of fibers that cross over.

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They're kind of arc-shaped and they

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go up towards the thalamus.

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So I'm going to make the thalamus a different color, even

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though we're not at the level of the thalamus.

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Let's make it bright green.

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So this would be the thalamus.

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And this portion of the thalamus that is involved in olfaction

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consists of the stria medullaris, the lamina,

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the medial nucleus of the thalamus.

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You also have a little bit of the hypothalamus involved,

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the lateral hypothalamus. And right behind it,

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the habenular commissure is also involved.

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So these dendrites do reach these structures in the thalamus.

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And the habenular commissure,

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which was looking for a function for many years,

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it is involved in olfaction.

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So now let's go up a little bit.

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By the way,

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here's the perforated substance that lies just antero superior

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to the pituitary gland a little bit off to the

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side right here should be seen on both sides.

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Again, here's the perforated substance on the opposite side.

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And now let's go up to the level of the thalamus.

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So in the medial portion of the thalamus is.

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Where you're going to have these arc-shaped

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tracts that came from the amygdala.

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So you got the diagonal band going this way to

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the amygdala then back over to the thalamus.

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You're going to have a group of arc-shaped tracts there and

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they have various names that maybe isn't so important.

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Like the medial telencephalic fasciculus reaches

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the thalamus and then, as we said,

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the striatal amygdalae and the medial nucleus of thalamus

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are located here with a habenula immediately behind it.

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You can see we're near the pineal gland.

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Maybe I've drawn it a little bit too big.

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I won't isolate the habenula right now,

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but I think you get the picture.

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So in summary,

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you've got dendrites that course laterally, medially.

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They do cross the midline and before ending two striata diverge

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the lateral stria is connected with the lateral olfactory

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nucleus and it's also directed to the amygdaloid body.

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And the medial olfactory stria is directed

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to the septal nuclei. And hypothalamus.

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Cortical projections of olfactory function are identified

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mostly in the prepiriform and the entorhinal cortex.

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Where's the entorhinal cortex? Right here.

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Let's go, coronally. Let's find your temporal lobe.

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And there is your entorhinal cortex right there.

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So that completes our discussion of the olfactory pathway

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which includes, by the way, the cingulate gyrus,

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the sulcus of the corpus callosum,

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the longitudinal stria of the corpus callosum and the dentate

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gyrus. And as stated, the uncus and amygdala.

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Let's move on, shall we?

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Pomeranz out.