Sectional Anatomy of the Telencephalon

The cross-sectional anatomy of the telencephalon is shown on the following pages. As in almost all other sections of this book, MRI cuts are taken following conventional planes.

Axial cuts are parallel to Talairach's bicommissural plane (a plane passing through the anterior and posterior commissures, as identified on the midsagittal plane). Coronal cuts are taken perpendicular to the axial ones; sagittal cuts are parallel to the interhemispheric fissure.

On each page the anatomical cut obtained with a Tl-w inversion recovery sequence is fully described. In addition, the same anatomical cut obtained with a T2-w FSE sequence is printed. At the bottom of the page, reference images on the other two planes of the space are shown, with the aim of giving spatial information that can aid in mentally identifying and locating the plane studied.

Cross-sectional anatomy needs no special comments as the anatomical structures are better described in the chapters relative to their functions.

Some comments concern the white matter macroscopic morphology. It consists of fibers, varying in size and arranged in bundles, and may be divided into three distinct systems.

• Projection fibers connect the hemisphere with the lower parts of the brain and the spinal cord.

• Transverse or commissural fibers unite the two hemispheres.

• Association fibers connect different structures in the same hemisphere; in many cases, these are collateral branches of the projection fibers, but others are axons of independent cells.

Axial cross-sections of the brain, when taken above the corpus callosum, show a mass of white matter on each hemisphere referred to as "centrum semiovale". Below it, projection fibers arising from the cortex and directed towards the internal capsule, together with fibers ascending from below towards the cortex, form the "corona radiata". The former occupy a narrow space on each side of the bodies of the lateral ventricles.

Similarly, a special contingent of fibers comes from the lateral geniculate body and reaches the occipital cortex, passing laterally to the occipital horn of the lateral ventricles, be ing more horizontally oriented. They are the optic radiations, i.e. the final part of the visual pathway.

Finally, in the axial cuts a mild asymmetry between the hemispheres can be observed.

This asymmetry is due to the hemispheric dominance. It is commonly known that 95% of right-handed people have hemispheric dominance on the left, while in 50 to 75% of left-handed individuals the dominant hemisphere is the left one. The dominance is anatomically expressed by a mild hemispheric hypertrophy that is at its most in the occipital region: the left occipital lobe, in such cases, extends slightly farther back than the right one, sometimes scalloping the occipital bone, sometimes bulging on the midline. The left occipital horn is usually longer than the contralateral, and the left transverse venous sinus is lower and smaller than the right one in about 50% of individuals.

Precentral gyrus Central sulcus Postcentral gyrus

Inferior frontal sulcus

Inferior precentral sulcus

Inferior frontal gyrus (F3), pars triangularis

Inferior frontal gyrus (F3), pars operculars

Inferior frontal gyrus (F3), pars orbitalis

Superior temporal gyrus (Tl)

Superior temporal sulcus

Middle temporal gyrus (T2)

Inferior temporal gyrus (T3)

Lateral fissure (of Sylvius)

Anterior transverse temporal gyrus

Postcentral sulcus

Supramarginal gyrus

Sulcus intermedius primus (Jensen)

Angular gyrus

Superior temporal sulcus, horizontal posterior segment

Middle occipital gyrus (02), superior part

Lateral occipital sulcus

Lateral temporo-occipital incisure

Middle frontal gyrus (F2)

Subcentral gyrus

Precentral Central gyrus sulcus

Postcentral gyrus

Inferior frontal sulcus

Inferior precentral sulcus

Inferior temporal sulcus

Inferior temporal gyrus (T3>

Anterior transverse temporal gyrus

Inferior frontal sulcus

Inferior precentral sulcus

Inferior frontal gyrus (F3), pars operculars

Inferior frontal gyrus (F3), pars triangularis

Inferior frontal gyrus

(F3), pars orbitalis

Lateral fissure (of Sylvius)

Superior temporal gyrus (Tl)

Superior temporal sulcus

Middle temporal gyrus (T2)

Middle frontal gyrus (F2)

Subcentral gyrus

Inferior temporal sulcus

Precentral Central gyrus sulcus

Postcentral gyrus

Inferior temporal gyrus (T3>

Anterior transverse temporal gyrus

Postcentral sulcus

, Supramarginal gyrus

Superior temporal sulcus, posterior ascending segment

Angular gyrus

Superior temporal sulcus, horizontal posterior segment

, Middle occipital gyrus (02), superior part

V Lateral occipital sulcus

V Latera! temporo-occipital incisure

, Supramarginal gyrus

Superior temporal sulcus, posterior ascending segment

Postcentral sulcus Supramarginal gyrus Angular gyrus

Superior temporal sulcus, posterior horizontal segment

Middle occipital gyrus (02), superior part

Lateral occipital sulcus

Lateral te m poro-occipital incisure

Inferior temporal inferior temporal Lateral fissure, of Sylvius, with sulcus gyrus (T3) middle cerebral artery peripheral branches

Inferior frontal sulcus

Subcentral gyrus

Prêtent ra I gyrus

Central sulcus

Postcentral gyrus

Middle frontal gyrus (F2), superior part

Inferior precentral sulcus

Inferior frontal gyrus (F3), pars triangularis

Inferior frontal gyrus (F3), pars operculars

Inferior frontal gyrus (F3), pars orbitalis

Lateral orbital sulcus

Lateral orbital gyrus

Superior temporal gyrus (T1)

Middle temporal gyrus (T2)

Postcentral sulcus Supramarginal gyrus Angular gyrus

Superior temporal sulcus, posterior horizontal segment

Middle occipital gyrus (02), superior part

Lateral occipital sulcus

Lateral te m poro-occipital incisure

Inferior temporal inferior temporal Lateral fissure, of Sylvius, with sulcus gyrus (T3) middle cerebral artery peripheral branches

Middle frontal gyrus (F2)t Circular insular Precentral Central Postcentral superior part sulcus gyrus sulcus gyrus

Inferior frontal sulcus

Inferior frontal gyrus (F3), pars operculars

Inferior frontal gyrus (F3), pars triangularis

Superior temporal gyrus(T1)

Middle temporal gyrus (T2)

Lateral occipital sulcus

Middle occipital gyrus (02), inferior part

Inferior occipital gyrus (03)

Angular gyrus

Middle occipital gyrus (02), superior part

Anterior transverse temporal gyrus

Long Insular gyrus gyrus (T3)

sulcus gyrus (T4)

Middle frontal gyrus (F2)t Circular insular Precentral Central Postcentral superior part sulcus gyrus sulcus gyrus

Middle frontal gyrus (F2), inferior part

Frontomarginal gyrus Lateral orbital gyrus Short Insular gyrus Limen insulae

Lateral occipital sulcus

Middle occipital gyrus (02), inferior part

Inferior occipital gyrus (03)

Inferior frontal sulcus

Intraparietal gyrus

Inferior frontal gyrus (F3), pars operculars

Angular gyrus

Inferior frontal gyrus (F3), pars triangularis

Middle occipital gyrus (02), superior part

Superior temporal gyrus(T1)

Anterior transverse temporal gyrus

Middle temporal gyrus (T2)

Long Insular gyrus gyrus (T3)

sulcus gyrus (T4)

Intraparietal gyrus

Middle frontal Precentral Central Postcentral gyrus (F2) gyrus sulcus gyrus

Central insular sulcus

Circular insular sulcus

Short insular gyrus Frontomarginal gyrus Lateral orbital gyrus

Lateral fissure of Sylvius

Limen insulae

Superior temporal gyrus (Tl)

Middle temporal gyrus (TZ)

Inferior temporal Fusiform Long insular Temporal horn gyrus (T3) gyrus (T4) gyrus of lateral ventricle intra parietal sulcus

Angular gyrus

Anterior transverse temporal gyrus

Superior temporal sulcus

Middle occipital gyrus (02), superior part

Lateral occipital sulcus

Middle occipital gyrus (02), inferior part

Inferior occipital gyrus (03)

Posterior transverse collateral sulcus

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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