The Tracheo-bronchial Tree: the Gita’s “Root-Up Branches-Down” Tree

 

ūrdhvamūlamadhaḥśākhamakṣvatthaṃ prāhuravyayam |

chandāṃsi yasya parṇāni yastaṃ veda sa vedavit || 15.1 ||

adhakṣcordhvaṃ prasṛtāstasya śākhā guṇapravṛddhā viṣayapravālāḥ |

adhakṣca mūlānyanusantatāni karmānubandhīni manuṣyaloke || 15.2 ||

 

In the fifteenth chapter of the Bhagavad Gita, Krsna, with a view to imbue Arjuna with the feeling of dispassion (vairajna), introduces the metaphor (rupaka) of “samsara vrksa,” the tree of material existence. The tree that Krsna speaks of is an inverted one; it is a Asvattha (ficus religiosa) whose root (mula) is above (urdhva) and whose branches (sakham) are below (adhah). This “inverted tree” is supposed to represent samsara, with its transitory yet uninterrupted-flow-like (pravaha) nature. The (sub) branches of this “inverted tree” extend both up and down.

This “inverted tree” is the tracheo-bronchial tree of the lungs.

In order to fully appreciate this great metaphor, found also in the Katha Upanisad and the Mahabharata, one must keep in mind that Krsna is the immanent lord (paramatma), speaking to Arjuna within the microcosm. Further, “material existence,” in the context of the Upanisads, has more to do with the body—the respiratory process in particular—than with the (external) world of the sense-objects.

The “root”of this (respiratory) “tree” is the trachea while its “branches” are the various bronchi which go on branching dichotomously. The “leaves” of this “tree” are said to be the metres of the Vedas. There is a greater likelihood of these being the respiratory bronchioles as these exist at the terminal end of the tracheo-bronchial tree; but they may also stand simply for the bronchioles.

The acinus is like the zone of the leaves because it is here that "food" production takes place; it's here that the carbon dioxide is absorbed and oxygen is released. The acinus marks a different functional component in the r. tree, like the leaves which are functionally different from the branches

According to Govinda Misra, the inverted tree is situated in the form of a body; obviously he is referring to the virat purusa ("deha rupe sthita").

The different regions of the bronchial tree are compared to the different parts of a tree. So there's the trunk, the larger branches (these two, the central axial region, must constitute the central region of jambudvipa), the smaller branches, the leaves, the shoots and the fruits and the flowers. The branch region probably ends with the "twigs," the terminal bronchioles.

On the Identity of Puskaradvipa

 Puskaradvipa appears to be that division of the tracheobronchial tree that is located (very) distally to the hilum, towards the periphery of the respiratory lotus. It, the Brahma Purana, says, contains neither mountain nor river; so this must mean that it does not contain those respiratory conduits considered to be “weighty” and “big”—the bronchi and the bigger bronchioles (the first five generations of them?) and the pulmonary arterial conduits corresponding to these, which are the “rivers.” The mountain Manasottara which is supposed to be located at the centre of Puskaradvipa, is the heart. Its perimeter does go like a ring across the five continents beginning with Plaksa (seen in this light, the five dvipas, Plaksa and the rest, and also Puskara, do seem to belong to the lower region of the lung; the Surya Siddhanta’s words). It divides Puskaradvipa (thoracic region) into two halves (the two lungs). These two halves of the left and the right lung have been given the names “Mahavita” and “Dhataki.” Brahma is worshiped in Puskara; and it is in this continent that a lotus having thousands of petals is situated. This lotus is the metaphorical representation of the trachea and the entire tracheobronchial tree. Brahma, the mind-organ (manas), is present as the neural controller of the lungs; he sits atop the “pericarp” (primary bronchi) of this wondrous lotus.

A Jaina Source on Jambudvipa

The Buddhist and the Jaina traditions too seem to share the same Puranic micro-cosmography. Some Jaina sources, for example, talk of several “horizontal bands” separating Jambudvipa into identical northern and southern hemispheres. This can only refer to the two “hemispheres” of the right and the left lung. These “bands” refer to groupings of the three entities of the bronchus, the pulmonary artery and the pulmonary vein. The following excerpt is precious as it supplements and buttresses our conclusions regarding the identity of the cosmographical entities found in the Puranas:

The Jambu-Dvipa is divided into identical northern and southern hemispheres by horizontal bands of different widths formed by six main parallel mountain ranges running from the east to the west. The central band, containing Mt. Meru, is larger than the others, and is known as the region of Maha-Videha. On one side of Mt. Meru, excluding the regions at its base known as Dev-kuru and Uttara-kuru, is the land of eastern Videha and on the other side is the land of western Videha. (Indian Painting: Essays in Honour of Karl J. Khandalavala. P. 134) 

The "Central Band" contains the principal bronchus (Mt Meru)

 In the quote above, the six main mountain ranges that run from the east to the west (medially to peripherally?) seem to be the principal bronchus and the primary branches of the pulmonary artery and vein, three on either side. This triad may be said to constitute a “band” and as this triad courses through the lung, its width also changes as a result of the change in the width of the individual conduits. 

The region of Videha is the region of Meru, the principal bronchus. The regions at the base of Meru are said to have the names of “Dev-kuru” and “Uttara-kuru.” Now, we already know from our Puranic sources that the base of Meru is the Ilavrta region, containing the four “support” or “feet” mountains of Meru—Mandara and the rest. It is in fact four regions with four mountains (the secondary or lobar bronchi). On comparing these two descriptions one may conclude that “Dev-kuru,” which must be Bharata and “Uttara-kuru” refer to two of the four regions of Ilavrta. Therefore, if our assumptions are correct and if the Puranic cosmographer agrees perfectly with his Jaina counterpart, the varsa of Bharata in the Purana should refer to one of the lobar regions.