Ventral view of the ferret neck, craniad to the top of the photo and caudal to the bottom of the photo.

Ventral and deep view of the ferret neck, craniad to the top of the photo and caudad to the bottom of the photo.

For comparison, see vessels of a bat, a fox, and a tree shrew.

Our dissection of the heart in the previous lab revealed the great veins. We could easily identify these vessels because the animal had a colored latex injection. In a double-injected animal, the veins are injected with bright blue latex to indicate that they had held deoxygenated blood. The great vessels are ventral to the trachea and esophagus and dorsal to the sternum. When the sternum and ribs are removed, the cranial vena cava is clearly visible, as are the left and right subclavian veins and the left and right external jugular veins. The subclavian veins bring blood from the brachii and the external jugular veins descend from the head. Both sets of vessels drain into the cranial vena cava. The five-point intersection of these vessels is three to four centimeters caudal to the shoulder joints. The drainage point of the subclavian veins is just caudal to that of the external jugulars.

The cranial vena cava has a diameter of three to four millimeters and is the largest vessel cranial to the heart. The external jugular veins are much larger than the subclavians, and are nearly the same size as the cranial vena cava. We could not immediately see the internal jugular veins. The large size of the external jugulars suggests that the internal jugulars do not have a great diameter. Other carnivores with enlarged external jugular veins have reduced or nonexistent internal jugulars. The right and left vertebral veins also flow into the superior vena cava, but they run deep within the vertebral foramina in the cervical vertebrae and we could not observe them.

We removed the external jugular veins and the subclavian veins to observe the deeper arteries. The left internal jugular vein can be identified once the superficial veins are removed. It is just lateral to the left common carotid artery, and the two vessels are enclosed in a sheath with the vagus nerve. This sheath is just lateral to the trachea. The internal jugular is much smaller than all of the superficial veins. We never found the right internal jugular, probably because it was destroyed when the animal was injected with latex. The difference in size between the external and internal jugular veins suggests that most of the principal veins of the head drain into the external jugular. The external jugular veins run lateral to the internal jugulars, and they have a greater diameter just cranial to the heart. There are no communications between the two veins until they both drain into the cranial vena cava.

We observed the arterial system once the superficial veins had been removed; the arterial system is dorsal to the venous system. In a double-injected specimen, the arteries are injected with red latex to indicate that they had held oxygenated blood. We removed the aortic arch with the heart, so we could not see the branch point of the brachiocephalic and left subclavian arteries. The arteries have small diameters compared to the veins. The brachiocephalic artery has a diameter of two millimeters. The brachiocephalic artery branches into the right subclavian artery and the right and left common carotids at the thoracic inlet [1]. We had cut the left common carotid during the dissection of the heart. We found the right vagus nerve just lateral to the right common carotid. The common carotid arteries branch into the internal and external carotids just posterior to the larynx [1], but we could not locate this branch point. A possible reason is that the internal carotid artery is very small in the ferret, and we may have misinterpreted it as a smaller artery branching off the common carotid. The difference in size between the internal and external carotids suggests that most of the arteries of the head branch off the external carotid.

Reference

1. Fox, J.G. 1998. Biology and Diseases of the Ferret (2nd Ed.). Williams & Wilkins, Baltimore.

Links:

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