Bat major vessels
Photo and text: Kathy Coulombe and Sarah Winstanley
Having removed the heart from the thorax, we were able to notice three vessels descending through the diaphragm. These are (from ventral to dorsal): posterior vena cava, esophagus, and descending aorta.
The vessels superior to the heart ascend and move deep to the muscles of the neck. It was necessary to cut and reflect all of these muscles, such as the platysma, sternohyoid and sublingual muscles.
Three relatively small vessels are observable on the lateral portions on the ventral side of the neck. Note that it is very difficult to differentiate between veins, arteries and nerves in the neck as they are all of similar size and origin, and all are white. However, after close inspection we were able to notice that the veins are flatter, and that the arteries are rounder. This is due to the fact that artery walls are thicker and more muscular in order to effectively pump the blood to the face and skull (and rest of the body in general). The veins have comparatively thinner walls, so that they become easily flattened when blood is not filling the tube. Using this method of differentiation, we were able to follow the common and external carotid artery cranially until the branches become too small to dissect in the sublingual region.
In general, for the microchiropterans, Tandler (1899) reports that the vessels of the head are similar to those in other insectivores.(1)
The common carotid artery splits into the internal and external branches at the base of the head, even with the bottom of the jaw (anterior portion of the neck). (1)
Kallen (1977) reports that the brain is supplied predominately by the vertebral arteries, and that the nasal cavity is mainly supplied by continuations of the brain vessels into the rostrum.
In the Microchiroptera, drainage of the veins in the head is almost exclusively into the external jugular vein. (1)
Our preliminary research showed that in bats where the auditory bulla is large (esp. in insectivorous species), the carotid bifurcation is near it. (1) Given that our species Tadarida braziliensis is insectivorous, we expected to find this lateralization of the carotid arteries. In our dissection, it was confirmed that the splitting of the common carotid to the external and internal carotid occurs at the level of C1, lateral and close to the auditory bullae.
The external carotid artery provides the laryngeal and salivary gland supplies, and feeds the internal maxillary artery.(1) The internal carotid artery is less prominent in this species.
The subclavian artery was dissected and clearly observable. The subclavian
artery runs laterally on the ventral side of the shoulder to supply the wing
membrane and associated muscles. Note that this artery is relatively large and
prominent. This may be due to the fact that the bat uses its forelimbs greatly
for locomotion and therefore needs a large circulation of blood to the forelimb
muscles.
| ARTERIAL BRANCH | ARTERIAL SOURCE OF BLOOD |
| auricular | internal carotid artery |
| superficial temporal | supplied by the posterior temporal, from the internal carotid artery |
| facial | external carotid artery |
| infraorbital (infraorbital supplies area below the eye orbit) | supplied by the internal maxillary, which is supplied by the external carotid artery |
| lingual | common carotid artery-at the common carotid split; the internal carotid splits off from the common carotid dorsally, while the lingual artery splits off ventrally (perfuses the tongue) |
| maxillary | external carotid artery -split is above the common carotid split, and about even with the anterior tip of the mandible internal maxillary artery originates at the base of the skull, near the medial portion of the mandibular ramus and condyle; this vessel is the continuation of the external carotid artery, and terminates as the infraorbital artery. |
| MINOR VEIN | DRAINS INTO |
| facial | External jugular |
| lingual | External jugular via the antereior facial vein |
| anterior auricular | External jugular via the antereior facial vein |
| posterior auricular | External jugular |
| submental | External jugular via the lingual vein |
| inferior labial | External jugular via the antereior facial vein |
| superior labial | External jugular via the anterior facial vein |
*All tabular information of the vessels from:
1. Kallen, F.C. 1977. "Cardiovascular system of bats", p. 289-483
in Wimsatt, W.A. (ed.) Biology of Bats: Vol. 4. Academic Press, New York.
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