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Cross Sectional Anatomy

Dr Ramachandrappa

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Topics

Study of the prepared sections and photographs:

The study of human organs or system by radiology and dissection will help us to know the 2 dimensional picture of the structure whereas cross sectional approach to anatomy provides a synthesis of putting together the knowledge gain by dissection into easily understandable three dimensional picture.

The three dimensional sense can be obtained by studying serial sections following a given single system or single structure, following back and forth and also following the series of sections for a study of another structure of system present in the series and noting their inter relations. Similar study of all the structures of all the system in a given series of adjacent sections can be interpreted and final outlook of a given cross section, given structure of system can be obtained.

After having obtained a sense of 3 dimensional picture using cross sectional anatomy , the same knowledge can be made use to study the pictures obtained by the newer radiological techniques for diagnostic purpose by CT, PET, MRI.

Basic principles in the study of cross sectional anatomy:

Study of cross sectional anatomy of any section may not reveal the complete 3 dimensional relations of any organs of system, hence a series of adjacent sections have to be studied to get the dimensional picture. Eg; The horizontal sections of the neck of 1 or 2 cm’s thickness at the level of C5 may fail to reveal the presence of the parathyroid gland which measures hardly 5 to 6mm in length.

Correlation between cross sectional anatomy and newer imaging techniques;

  1. The size and shape of an object can vary in different sections (oblique and horizontal ) and in different scans.
  2. The successive sections taken close together will never appear same.
  3. Scans with contrast medium will be showing extremely denser areas, in relation to dense object.
  4. Extremely thin structures like menicus and intervertebral disc may be difficult to identify in sections and also in the scan thus they should be kept in mind while interpreting the scans.
  5. The shadows of the object in the CT scans will produce a varying spectrum of light which vary from extreme white to extreme black with 64 different type of shades. The appearance of this grey nature will depend on the density/volume of the object which depends on the ionic composition of the object which will be proportional to the linear absorb coefficient or attenuation coefficient of the object. (Enclosure: I B)

Attenuation coefficient of the object is the permeability of the tissue for the x-rays hence the objects with higher density will appear white. Eg: Bone, cardiac muscle, kidney, liver, pancreas and larger blood vessels.

The objects with less density will appear jet black or shades of grey example lungs, adipose tissue. The density value of the objects are standardized taking the density value of water as zero houns field units, that of air as -1000 hounsfield units. The density value of compact bone is +250 units spongy bone +130 units, thyroid +70 units, liver +65 units, coagulated blood +80 units, venous blood +55 unit, exudates +18 units, fatty tissue -90 units. (Enclosure VII and VIII ).

Conclusion

  1. The knowledge of cross sectional anatomy is of use for the sonologists to determine the size the location, the shape, the volume of the pathlogical lesions and to guide the clinicians of surgeons for effective therapeutic and surgical measures particularly in laser and microsurgery. Eg: The treatment of the recurring myeloma 4.5 mm in size using sterotactic radiosurgery first of its kind in India was under taken by Dr. Reddy and his team in Apollo Hospital , Madras. The advantage of this is:

    1. It is an out patients procedure.
    2. Does not involve anaesthesia. Saving of head of blood transfusion. (Indian Express dated 9th June 1995)

  2. Knowledge of cross sectional anatomy will help in the identification of certain areas which have not made their significance in Gross anatomy Eg: Inferior aortic recess. Right pulmonic recess of transverse sinus.

  3. It will be of immense help in the diagnosis of congenital disease of heart and gastro intestinal tract.

  4. Hence the knowledge of cross sectional anatomy is a must for everyman and woman of the medical profession without which the practice of medicine will be a failure.

  5. The knowledge of cross sectional anatomy can be obtained only in the department of anatomy not anywhere else, the knowledge of cross sectional anatomy can be imported to the undergraduate and post graduate courses irrespective of the inclusion- non inclusion in the curriculum of teaching.

  6. Anatomical society of Karnataka being a professional body should recommend to the academic councils of all the Universities in the state and the country and to the Medical council of India to include cross sectional anatomy in the curriculum like that existing in USA wherein they have made the study of cross sectional anatomy compulsory for surgical residency programmer.

  7. I may be permitted by this August house to suggest to the Association of anatomists of Karnataka to initiate conduction of workshops in cross sectional anatomy.

I may be permitted to conclude saying,

“Strange how much you have got to know before realizing how little you know!”

References

  1. A cross sectional approach to anatomy by Roy R Peterson
  2. Cross sectional anatomy- An atlas for computerized tomography by Robert S Ledley
  3. Whole body computerized tomography by O.H Wegener
  4. Cross sectional anatomy, computerized tomography and ultrasound correlation by Barbara L. Carter
  5. Cross sectional anatomy: Preparation of teaching specimens: by R.D. Peppler Anatomical record July 1993
  6. An educational method of cross sectional anatomy combined with gross anatomic practice by Saraki K Dept of anatomy Yokohama City University School of Medicine Japan June 1994

Dr Ramachandrappa
Deputy Registrar, Rajiv Gandhi University of Health Sciences.
Karnataka, Bangalore
Formerly Professor and Head of the Department
Department of Anatomy
Dr B R Ambedekar Medical College, Bangalore


Deputy Registrar, Rajiv Gandhi University of Health Sciences.
Karnataka, Bangalore
Formerly Professor and Head of the Department
Department of Anatomy
Dr B R Ambedekar Medical College, Bangalore

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