Page 337 - Anatomy and Physiology of Farm Animals, 8th Edition

322 / Anatomy and Physiology of Farm Animals

and those having more than one digit per trunk. The pig, in contrast to other ungu-
lates, has two branches from the aortic
limb of course have a somewhat different
VetBooks.ir arrangement of arteries and veins in asso- arch: (1) the left subclavian artery supply-
ing the left forelimb and adjacent parts of
ciation with their specific anatomy.
the trunk and neck, and (2) the brachioce-
Aorta phalic trunk supply similar regions on the
right side plus the head and neck.
Aortic Arch. The left ventricle receives Thoracic Aorta. The thoracic aorta
oxygenated blood from the left atrium and passes caudad just ventral to the vertebral
pumps the blood throughout the systemic bodies. As it does so, pairs of segmental
circulation by way of the largest artery, the arteries arise from its dorsal aspect to
aorta. The aortic valve, at the junction of supply the thoracic wall and epaxial
the left ventricle and aorta, prevents muscles. Each of these intercostal arteries
backflow of blood from the aorta into the enters the corresponding intercostal space,
left ventricle when the ventricle relaxes. giving off a spinal branch that enters the
Two large vessels arise from the aorta
immediately distal to the aortic valve. vertebral canal to supply the spinal cord
and spinal nerve roots. The continuation
These are the right and left coronary of the dorsal intercostal artery follows the
arteries, and they are the arterial blood caudal border of each rib ventrad. Other
supply for the heart muscle (myocardium) branches of the thoracic aorta supply parts
itself. Most of the venous blood from the of the esophagus, lungs, and diaphragm.
myocardium is returned to the right atrium
by way of the coronary veins, which empty Abdominal Aorta. The aorta is called
directly into the right atrium by way of the the abdominal aorta after it passes
coronary sinus, adjacent to the opening of through the diaphragm at an opening called
the caudal vena cava. the aortic hiatus. Ventral to the last few
After emerging from the base of the lumbar vertebrae, it terminates by dividing
heart, the aortic arch courses dorsad and into two external iliac arteries (supplying
then caudad, just ventral to the bodies of the pelvic limbs) and two internal iliac
the thoracic vertebrae. The aorta continues arteries (supplying the gluteal and perineal
as the thoracic aorta until it passes region). Some species have a median
through the aortic hiatus of the diaphragm sacral artery, a small midline continuation
to become the abdominal aorta. Arteries of the aorta that continues ventral to caudal
that supply the head, neck, and thoracic vertebrae as the median caudal artery.
limbs branch from the aortic arch. The accompanying median caudal vein
In horses and ruminants, the aortic arch (tail vein) at this site is often used for
gives rise to a single large brachiocephalic collection of blood from adult cattle.
trunk, whose many branches distribute The abdominal aorta features paired
blood to the cranial half of the animal. The lumbar arteries (one pair per lumbar ver-
precise pattern of the main arterial tebra) arising from its dorsal side, supply-
branches is species dependent, but the fol- ing the abdominal wall and epaxial muscles
lowing generalities can be made: (1) the and giving off spinal branches that supply
main blood supply to the thoracic limbs the spinal cord and spinal nerve roots of
arises as right and left subclavian arteries; the lumbosacral region. Paired visceral
(2) the right and left costocervical trunks branches provide arterial blood to the kid-
provide arterial blood to regions of the neys (renal arteries) and gonads (gonadal
neck and cranial thoracic wall; and (3) right arteries, often called testicular or ovar-
and left common carotid arteries, a main ian arteries depending on the sex of the
source of blood for the head and brain, animal). Three unpaired visceral branches
arise together from a single bicarotid supply nearly all the abdominal viscera.