Page 338 - Anatomy and Physiology of Farm Animals, 8th Edition

Anatomy of the Cardiovascular System / 323

The internal carotid arteries or their
These are, from cranial to caudal, the derivatives enter into an anastomotic ring of
VetBooks.ir celiac, cranial mesenteric, and caudal vessels on the base of the brain called the
mesenteric arteries.
The celiac artery arises shortly after the
cerebral arterial circle (formerly circle of
aorta passes through the diaphragm. This Willis) (Fig. 17‐7B). The cerebral arterial
is a large unpaired artery that supplies the circle gives rise to arteries that primarily
stomach (left gastric artery), the spleen supply the cerebral hemispheres. More cau-
(splenic artery), and the liver (hepatic dal parts of the brain, the brainstem, and the
artery). The exact branching pattern of cerebellum receive most of their blood sup-
this artery depends to a great extent upon ply from branches of the basilar artery.
the type of stomach; the ruminant has a This single ventral artery is formed by the
much more complex distribution of the joining of right and left vertebral arteries.
celiac artery than do animals with a simple The robust vertebral arteries ascend from
stomach. their origin in the thorax, run alongside the
Immediately caudal to the celiac artery cervical vertebrae, enter the foramen mag-
is the cranial mesenteric artery. This num of the skull, and there merge to become
large, unpaired artery branches into a the basilar artery (coursing rostrad) and the
number of smaller arteries that supply ventral spinal artery (running caudad).
blood to most of the small intestine and
much of the large intestine. The number
and distribution of the branches of the Arterial Distribution to the
cranial mesenteric artery vary among Thoracic Limb
species.
The caudal part of the large intestine The right and left subclavian arteries follow
and the rectum receive blood from a rela- the same course on each side of the body
tively small unpaired artery, the caudal and each gives off similar branches. Within
mesenteric artery. the thorax each subclavian artery gives off a
number of branches that supply blood to
the caudal part of the neck, much of the
Arterial Distribution to the Head thoracic wall, and the dorsal part of the
shoulder. The subclavian artery passes
Most of the structures of the face, head, cranial to the first rib on the respective side,
and cranial neck are supplied by the right passing into the axilla (armpit) of the tho-
and left common carotid arteries, each of racic limb, where it is called the axillary
which runs craniad in a connective tissue artery. The axillary artery enters the limb,
sheath with the vagosympathetic trunk of becoming the brachial artery in the region
the same side (Fig. 17‐7A). This carotid of the brachium and then the median
sheath lies in a groove dorsolateral to the artery as it continues distal to the elbow.
trachea. Branches of the common carotid The largest terminal branch of the median
arteries supply the thyroid gland and artery in the horse is the medial palmar
larynx. In the region of the larynx, the artery, which passes distad in the metacar-
common carotid artery gives off the inter- pus to the fetlock, where it divides into
nal carotid artery, a primary source of medial and lateral digital arteries
blood for the brain. The continuation of (Fig. 17‐8). In ruminants, the median artery
the common carotid artery is the external is continued in the manus as the palmar
carotid artery, whose many branches sup- common digital artery. Branches of it
ply the face, tongue, and structures of the together with distal continuations of other
oral and nasal cavities. The facial artery is arteries in the metacarpus provide axial
convenient for taking a pulse as it passes and abaxial digital arteries to each of the
across the mandible. two weight‐bearing toes.