Craniad is to the left of the photo, caudad to the right.

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

Dissection and Function

As the chest cavity had been opened, the sternohyoideus and sternothyroideus muscles dissected and reflected, and the heart and lungs removed in previous labs, the cranial arteries and nerves could be seen without further gross dissection. In order to distinguish between the different vessels the connective tissue between them was teased apart. The majority of the blood supply to the head and neck is provided by arteries arising from the three branches of the aortic arch. The brachiocephalic trunk arises anterior to the trachea and posterior to the left brachiocephalic vein, and ascends to the right side of the trachea, where it gives rise to the right subclavian artery and right common carotid artery. One of the most visible vessels in this dissection, the left common carotid artery forms the second branch of the aortic arch, and runs anterior to, and to the left of, the trachea, and dorsal to the sternohyoideus and sternothyroideus muscles of the neck. The left subclavian artery is the third branch off the aorta, and runs to the left of the left common carotid artery. At the level of the thyroid cartilage the common carotids split into the internal and external carotid arteries. The internal carotid artery does not branch in the neck, but rather enters the skull and becomes the main artery of the brain and orbit. The external carotid arteries run medial to the vagus nerve, branch in the neck, and supply structures external to the skull. [1]

The majority of the blood returns from circulation to the heart via the cranial (or superior) and caudal (or inferior) vena cava. The main vein responsible for drainage of the brain and superficial aspects of the neck is the internal jugular vein, which joins the brachiocephalic vein posterior to the sternal end of the clavicle. The internal jugular vein was not visible in this lab, but runs lateral to the trachea and dorsal to the sternohyoideus and sternothyroideus muscles. The brachiocephalic vein is also joined by the subclavian vein, which receives deoxygenated blood from the external jugular vein. The external jugular vein drains the majority of the face and scalp. The external jugular vein was not present in this dissection, as it had been removed when the animal was skinned. At the level of the first costal cartilage, the brachiocephalic veins join to form the cranial vena cava. This returns blood to the heart from all structures cranial to the diaphragm, with the exception of the lungs (see heart lab for discussion). [1] The cranial vena cava lies anterolateral to the trachea and posterolateral to the ascending aorta. The smaller veins joining the vena cava emerged almost directly from the body wall, and so were not able to be further identified.

Source:

1. Moore, Keith L. and Anne M. R. Agur. 1995. Essential Clinical Anatomy. Lippincott, Williams and Wilkins, Baltimore.

Links:

to Comparative Mammalian Anatomy home

to mammalian major vessels