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A qualitative and quantitative study of the lung of an ostrich, Struthio camelus

John N. Maina^* and Christopher Nathaniel

Department of Anatomical Sciences, The University of the Witwatersrand, 7 York Road, Parktown, Johannesburg 2193, South Africa

View larger version (136K): [in a new window]   Fig. 1. (A). Dorsal view of the trachea (circled) and the lung of the ostrich Struthio camelus. The lungs are deeply entrenched into the ribs on the dorsolateral aspects (arrowhead). Filled circle, right extrapulmonary primary bronchus (EPPB). Note that the right EPPB is relatively longer, rather horizontal and relatively narrower compared with the left EPPB. Scale bar, 1 cm. (B) Close up of the dorsal aspect of the lung showing the deep costal sulci (s). Trachea, circled; filled circle, right extrapulmonary primary bronchus. Scale bar, 2 cm.

View larger version (66K): [in a new window]   Fig. 2. A schematic illustration of the lung of the ostrich Struthio camelus showing various measurements of the air conduits. EPPB, extrapulmonary primary bronchus; IPPB, intrapulmonary primary bronchus; MVSB, medioventral secondary bronchi; MDSB, mediodorsal secondary bronchi; LVSB, lateral ventral secondary bronchus.

View larger version (134K): [in a new window]   Fig. 3. (A) Close up of the hilus of the lung of the ostrich Struthio camelus showing three medioventral secondary bronchi (filled circles) arising from the primary bronchus (p) (dissected out). Parabronchi, circled; a, pulmonary artery; v, pulmonary vein; n, cranial branch of the pulmonary artery. Each gradation on the scale bar, 1 cm. (B) A dental plastic impression at the hilus and the intrapulmonary primary bronchus (dashed line) showing the three medioventral secondary bronchi (filled circles). Parabronchi, circled; asterisk, a mediodorsal secondary bronchus. Each gradation on the scale bar, 1 cm.

View larger version (101K): [in a new window]   Fig. 4. (A,B) Views of dental plastic impressions of the hilus and the intrapulmonary primary bronchus (dashed line) of the lung of the ostrich Struthio camelus showing three medioventral secondary bronchi (filled triangles) and five mediodorsal secondary bronchi (filled circles). Open triangle, parabronchi; asterisk, lateroventral secondary bronchus; location of the neopulmonic parabronchi, circled. Each gradation on the scale bar, 1 cm.

View larger version (109K): [in a new window]   Fig. 5. Medial view of the left lung of the ostrich Struthio camelus showing the hilus and the three medioventral secondary bronchi (filled circles) arising from the primary bronchus (marked with a pencil). a, pulmonary artery; the arrow indicates ostium opening to the abdominal air sac. Each gradation on the scale bar, 1 cm. Open circles, parabronchi.

View larger version (104K): [in a new window]   Fig. 6. Lateral view of the left lung of the ostrich Struthio camelus showing mediodorsal secondary bronchi (filled circles) arising from the primary bronchus. s, costal sulci; open circles, parabronchi. Each gradation on the scale bar, 1 cm.

View larger version (109K): [in a new window]   Fig. 7. (A) A slice of the lung of the ostrich Struthio camelus at the level of the third costal sulcus showing stacks of anastomosing parabronchi (p), a mediodorsal secondary bronchus (b) and a pulmonary artery (a). Each gradation on the scale bar, 1 cm. (B) A slice of the lung at the level of the first costal sulcus showing parabronchi (p), a medioventral secondary bronchus (b) and a pulmonary artery (a). The circle shows a secondary bronchus. Each gradation on the scale bar, 1 cm.

View larger version (165K): [in a new window]   Fig. 8. (A) View of a medioventral secondary bronchus (filled circles) giving rise to parabronchi (p). (B) Parabronchial lumina (p) surrounded by exchange tissue (t); v, interparabronchial blood vessel. n, intraparabronchial blood vessel; Note the shallow atria (circled). Scale bars, 1 mm.

View larger version (156K): [in a new window]   Fig. 9. (A,B) Views of the ostrich Struthio camelus lung showing an interparabronchial blood vessel (v). Intraparabronchial vessel, circled; t, exchange tissue; p, parabronchial lumen; arrows indicate atrial muscles. Note that interparabronchial septa are lacking in the lung and the atria (open triangle) are very shallow. Scale bars, 5 µm.

View larger version (79K): [in a new window]   Fig. 10. (A) Exchange tissue of the lung of the ostrich Struthio camelus showing air capillaries (*) and blood capillaries (filled circles). The blood capillaries contain erythrocytes (filled squares). Open circles, blood–gas (tissue) barrier; filled arrowheads, tissue not involved in gas exchange, i.e. areas where blood capillaries join or where air capillaries lie adjacent to each other. Scale bar, 5µm. (B) A blood capillary showing the blood–gas (tissue) barrier (open circle); blood plasma (p) and an erythrocyte (filled square). Note the sporadic attenuation of the blood–gas (tissue) barrier and the numerous micropinocytotic vesicles, filled arrowheads. Asterisks, air capillaries. Scale bar, 1µm.

View larger version (45K): [in a new window]   Fig. 11. Views of three-dimensional computer designs based on actual measurements of the bronchial system of the ostrich Struthio camelus. The air conduits that are shown include the extrapulmonary primary bronchi (EPPB, filled circles), the intrapulmonary primary bronchi (IPPB, filled squares) and the medioventral secondary bronchi (MVSB, filled triangles) (see also Fig.2). The size and angulation of these air conduits are the most important features in the generation of inspiratory aerodynamic valving (IAV), i.e. the shunting of the inspired air past the openings of the MVSB. (A) Side view of an extrapulmonary primary bronchus, an intrapulmonary primary bronchus terminating in an ostium (asterisk) and three MVSB. (B,C) Views of the air-conduits in the right and left lungs. Note that only the sizes and the geometry at the origins of the MVSB, the most critical areas in IAV, are shown in the constructions. Subdivision and subsequent angulation of the bronchi is evident in Fig.2 and in the actual specimens (Fig.3, Fig.4A, Fig.5).