anatomy lecture 3 - encephalon-sectionalanatomy.ppt

8/10/2019 Anatomy Lecture 3 - Encephalon-SectionalAnatomy.ppt

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Sectional anatomy of

encephalon


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Basic elements of sectional geometry

Although classic definition of section refers only to

the intersection of a surface with a plane, for the

anatomical study, the sections can be consideredas geometrical objects, surfaces and lines.


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Thereby, we consider that:

The intersection of an object (three-dimensional) with a planegenerates a surface (two-dimensional) - for example:

parenchimatous organs, fusiform muscles;

The intersection of a surface (two-dimensional) with a plane

generates a line (one-dimensional)for example: the diaphragm,

serous, meninges;

The intersection of a line (one-dimensional) with a plane generates

a point (zero-dimensional)for example: vessels, nerves.


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For the orientation of sections, the main axes and orientation planesof the human body must be studied. In a three-dimensional space(as the one used in human anatomy), from a certain point, threestraight axes, perpendicular to each other can be drawn, whichdetermine two by two a plane, the third one being perpendicular tothis plane.

Thereby:

- Median plane contains vertical and anterior-posterior axes and isperpendicular to the transverse axis

- Frontal plane contains vertical and transverse axes and isperpendicular to the anterior-posterior axis

- Horizontal plane contains transverse and antero-posterior axes andis perpendicular to the vertical axis

In the study of human anatomy, the most frequent sections are theones drawn through these planes.


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Median section through encephalon

Due to the fact that the median plane is the single symmetry plane of the

human body, the median section is a single one

Other standard sections, being perpendicular to the symmetry plane, are

symmetrical Median section is the only standard asymmetric one

So, it is easy to recognize it, because of the characteristic shape of corpus

callosum (with its rostrum, genu, body and splenium) and of cerebellar

vermis (Arbor vitae- the tree of life)


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We study:

- the three levels of brain stem (medulla oblongata, pons and

mesencephalon),

- the 4thventricle with superior medullary velum and inferior medullary velum

- vermiss lobulation (archicerebellum, paleocerebellum, neocerebellum),

- 3rdventricle (with thalamus, hypothalamus and epithalamus)

- the gyrations and fissures of cerebral hemisphere - medial aspect


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On sections of the entire cephalic extremity, there can be observed:

- paranasal sinuses of median bones (anterior frontal sinus, and sphenoidsinus in the center of the section, under the hypophysis lodge)

- the three levels of pharynx (nasopharynx, oropharynx and laryngopharynx),having anterior the corresponding cavities:

- nasal fossa with conchas and their meati (superior,middle and inferior meatus)

- oral cavity with vestibule (anterior)- isthmus faucium with tonsil and palatine velum (velumpalatinum)- posterior,

- larynx with the vestibule, vestibular fold, ventricle, vocalcord and infraglotic cavity


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Fronta l sect ions th rough encephalon

Are symmetric sections

In theory, there are infinity sections drawn perpendicular

to the anterior-posterior axis, but, practically, anterior,

middle and posterior sections are used.


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For their identification and orientation, we use the cavities insideencephalon (cerebral ventricles):

- In anterior sections, the anterior horns of lateral ventricles appear as twoclosely related cavities and separated by the narrow pellucid septum.

- In middle sections, a three cavities system with a T disposition isobserved: two horizontal, superiorly located (lateral ventricles) and onevertical, narrow, underneath them (III ventricle); inferior, on the medial sideof the temporal lobe, the hippocampus is located, with its particular shape

(sea-horse shape)

- In posterior sections, inferiorly, brain stem is located (with peduncles,substantia nigra and lower, the pons) and cerebellum with its above situatedcerebellar tentorium (tentorium cerebelli), which separates it from cerebraloccipital lobes with the posterior horns of lateral ventricles.


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Anter ior fronta l sect ions throu gh encephalon


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Middle fronta l sect ions throu gh encephalon


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Poster ior fronta l sect ions throu gh encephalon


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On frontal sections of the entire cephalic extremity, one can notice:

- ethmoidal cells, nasal fossa with their conchas and meati

as well as their relations with the neighboring cavities of the face:

- oral cavity with the vestibule and dental arches;

- laterally: the orbit, maxillary sinuses, temporal and infratemporal fossa.


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Horizontal sections through encephalon

The skull and the encephalon contained within, have an ovoid

shape, prolonged anterior. So, we recognize horizontal sections by

their diameter, parallel with the symmetry axis (anterior-posterior),

which is larger than the one perpendicular to the axis (transverse).

In theory, there are infinity sections drawn perpendicular to the

vertical axis. But practically, superior, middle and inferior sections

are used.


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For their identification and orientation, we use, once more, the cavities

inside encephalon (lateral ventricles):

- In superior sections, ventricles are not included, or, there can be noticed, atmost, their central part (parietal); orientation is achieved only by the ovoid

shape: the narrowest pole (frontal) is anterior located and the broadest

(occipital), posterior.

- In middle sections, anterior (frontal) horns of lateral ventricles are observed,

as comma shaped cavities, closely related to each other and separated by

a double, narrow wall (pellucid septum); posterior (occipital) horns are

triangular and apart.

- In inferior sections, cerebellum is posteriorly located (first one can observe the

culmen of vermis and then the hemispheres), and anteriorly, we find inferior

(temporal) horns of lateral ventricles.


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Encephalon hor izontal sect ions


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In inferior horizontal sections of the entire cephalic extremity, are observed:

- frontal and sphenoid sinuses (in pairs, although the thin separation wall isasymmetric)

- ethmoidal cells

- nasal fossa

- oral cavity with vestibule and dental arches

- pharynx

- lateral, are observed: - the orbit- maxillary sinuses

- temporal and infratemporal fossa

Both on frontal and horizontal sections, are noticed the relations between

cerebral ventricles and grey matter of the brain


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Lateral to lateral ventricles, there are the caudate nuclei (nucleus):

- the head is found lateral to the anterior horn

- the body- lateral to the central part

- the tail- lateral to the inferior horn;

Posterior horn does not have relations with basal nuclei.


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Lateral to the 3rd ventricle, we find the thalamus.

After it, there is an alternation of white and grey substances:

- internal capsule

- lentiform nucleus

- external capsule

- claustrum

- extreme capsule

- insular cortex


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Clinical c orrelat ions


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anatomy lecture 3 - encephalon-sectionalanatomy.ppt

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