Table 1.
Specimens Dissected.
Fig 1.
Ventral views of Pseudemys, Corallus, and Anolis.
(A) the turtle trachea and esophagus are seen to pass straight. (B) the emerald tree boa’s trachea and esophagus are seen to stay in the midline. (C) the anolis trachea’s course is straight. (D) the anolis esophagus passes midsagittally. Tra = trachea; Eso = esophagus. Emerald tree boa image courtesy of R. DePalma.
Fig 2.
Alligator mississippiensis and Crocodylus niloticus.
(A) ventral view of A. mississippiensis trachea. (B) radiograph of alligator trachea. (C) ventral view of the Nile crocodile’s trachea and esophageal course. Tra = trachea; Eso = esophagus; Tra loop = tracheal loop. Nile crocodile image courtesy of J. Reidenberg.
Fig 3.
Ancestral state reconstruction phylogeny of tracheal displacement.
For ease of understanding tracheal placements in bird taxa. Esophageal placement has, essentially, almost no variability and so is not plotted. Red = right lateral; green = left lateral; black = right lateral and left lateral; blue = right lateral and midsagittal; gray = midsagittal.
Fig 4.
Duck and goose trachea and esophagus.
(A) right lateral view of the neck of Aix sponsa showing displacement of the organs occurring quickly after exiting the oropharynx. (B) radiograph of Aix sponsa. (C) ventral view of the neck of Branta canadensis showing a gradual displacement of the organs so that they are lateralized only in the posterior region of the neck. (D) radiograph of lateral view of Branta canadensis. Tra = trachea; Eso = esophagus.
Fig 5.
Pigeons showing individual variation of the degree and immediacy of displacement.
A and C show a more gradual displacement of the trachea while B and D show a more immediate displacement of the trachea. D also shows a strongly dorsolateral placement of the trachea having been pushed dorsally due to a filled crop. Tra = trachea; Eso = esophagus.
Fig 6.
The course of the trachea and esophagus in P. auritus.
(A and B) lateral view of hatchling P. auritus. (C) ventral view of juvenile P. auritus showing a midsagittal placement of the trachea. (D) lateral view of adult P. auritus. Tra = trachea; Eso = esophagus.
Fig 7.
Phalacrocorax auritus radiographs.
(A) hatchling double-crested cormorants. (B) adult. Tra = trachea.
Fig 8.
(A) dissection. (B) radiograph. Tra = trachea; Eso = esophagus.
Fig 9.
(A) lateral view of ring-billed gull. (B) lateral view of ring-billed gull. (C) ventral view of ring-billed gull showing the trachea on the left side of the neck. (D) radiograph of the gull from C with a left ventrolateral trachea.
Fig 10.
(A) Accipiter cooperii placement of the trachea and esophagus are on the left side of the neck. (B) radiograph of A. cooperii also showing the trachea on the left. (C) Buteo jamaicensis ventral view showing a more typical right lateralization. (D) Buteo platypterus ventral view displaying a midsagittal position of the trachea. The trachea is also twisted nearly 180°. Tra = trachea; Eso = esophagus.
Fig 11.
Bradypus tridactylus views of the tracheal loop.
(A) lateral radiograph of the course of the trachea. (B-D) views of the tracheal loop. Tra = trachea; Tra loop = tracheal loop.
Table 2.
Summary of Vertebrate Tracheal and Esophageal Positions from Dissections and Personal Observations.
Fig 12.
Lateral view of the cervical musculature of Alligator mississippiensis.
M. sternomastoideus is reflected away ventrally to expose the m. omohyoideus and m. scalenus.
Fig 13.
Lateral views of the cervical musculature of Branta canadensis.
(A) anterior muscles. (B) posterior muscles.
Fig 14.
Cucullaris and tracheal muscles of Branta canadensis.
(A) Left: dorsal view of the posteriormost portion of the neck with the skin peeled back to reveal the m. cucullaris cervicis and capitis. Right: dorsal view of the skin of the neck peeled back to display the m. cucullaris capitis. (B) view of the inside of the thorax to show the m. tracheolateralis and m. sternotrachealis of the goose.
Fig 15.
A. mississippiensis cervical and infrahyoid musculature.
(A) lateral view of the neck and infrahyoid musculature. (B) ventral view of the m. episternobranchialis and m. sternohyoideus. (C) ventral view of the ventralmost cervical muscles with the trachea, esophagus and infrahyoid muscles pushed aside.
Table 3.
Differences in Neck and Tracheal Lengths in Birds.
Fig 16.
Radiographs of P. auritus neck.
(A) “Rostral loop” is the upper half of the “S” shape of the bird neck; while the “caudal loop” is the lower half. Terminology after Van der Leeuw et al. [63]. Lateral view showing the course of the trachea and its oblique points (point where the trachea crosses planes (medial to lateral and vice versa). (B) ventral view showing the course of the trachea and its oblique points.
Fig 17.
Top: bird neck cut to show the extent of rotation of the trachea and esophagus. Bottom: Illustrations of normality and displacement. Bottom left: an illustration of the normal, midsagittal, condition. Bottom right: an illustration of tracheal and esophageal displacement. Rotation is evident. Orange lines outline the mid-dorsal portions of the organs. In TED, the organs can be seen to have been rotated so that their mediodorsal points face inward toward the vertebral complex.