The Arterial System of Guinea Pig

The Arterial System:

I. The left aorta (right is absent) arises from the base of the left ventricle, turus left, forms an arch round the left bronchus and runs posterodorsally as the dorsal aorta, through an aperture in the diaphragm. The aortic arch has three portions—the ascending aorta, aortic arch and dorsal aorta.

1. Coronary artery:

Two or three small vessels arise close to the base of ascending aorta and supply blood to the heart.

2. Brachiocephalic artery:

First branch of aortic arch. It divides into a lateral branch, the right subclavian artery and a medial short, stout branch forming the base of the right and left common carotids.

A. Right subclavian:

Arising from the bra­chiocephalic artery it runs outward between the first rib and clavicle and sends following branches.

i. Vertebral to cranial cavity, para­vertebral musculatures and spinal cord.

ii. Caudal thyroid runs forward ob­liquely to the left, divides into right and left caudal thyroid, proceed anteriorly by the sides of the trachea, supply the thyroid gland.

iii. Superficial cranial supply the muscles of neck region.

iv. Internal thoracic supply the sternal region.

v. Costocervical supply the neck, up­per part of thoracic wall and dia­phragm.

3. Axillary:

The portion of the artery be­yond the origin of costocervical up to the bra­chial artery.

It sends the following branches:

i. External thoracic supplies pectoral and trapezius muscles and axillary lymph nodes.

ii. Lateral thoracic supplies muscles of pectoral region.

iii. Subscapular supplies upper arm, scapula and thorax.

4. Brachial continues to the extremity of the forelimb and divides into a number of branches.

5. Common carotid:

Left and right com­mon carotid arise from a common base.

a. Right Common carotid runs to the head lying parallel and right to the trachea. Sending a branch to the lymph node the artery divides into two—external and internal and supplies the right side in the anterior region.

i. Internal carotid enters the skull and supplies to the brain and deep struc­tures of the head.

ii. External carotid branches to supply head, tongue, jaw, parotid gland, pharynx, oesophagus and thyroid gland.

b. Left common carotid branches similar to right common carotid.

B. Left subclavian:

Arises directly from the aortic arch at a short distance from the brachio­cephalic artery. Branches are similar to those of the right subclavian, except lacking caudal thyroid.

6. Dorsal aorta:

Runs posteromedially and sends following branches to the middle and posterior part of the body:

i. Intercostal:

A few pairs of small ar­teries supply thoracic region.

The dorsal aorta pierces the dia­phragm, enters the abdominal cav­ity.

The branches in the abdominal region are:

ii. Coeliac:

A large unpaired vessel, send branches to oesophagus, stomach, spleen, pancreas, liver, major part of intestine, caecum, ascending trans­verse and descending colon, and other associated structures.

iii. Renal:

Two pairs. The anterior pair supply kidneys, and send branches to adrenal and diaphragm as caudal phrenic arteries. The posterior pair ends in Kidneys.

iv. Genital:

Paired, supply gonads and their ducts.

v. Lumbar:

A few paired arteries poste­rior to genitals, supply dorsomedian muscles of the lumbar region.

vi. Median sacral:

Arises at the junction of two common iliacs and supplies sacral and coccygeal region.

vii. Caudal mesenteric:

Unpaired, arises from the dorsal aorta in between sec­ond and third pairs of lumbars and sends branches to descending colon, rectum and anal region.

viii. Common iliac:

Paired, the right and left common iliacs are formed by the bifurcation of the dorsal aorta. Each divides into two major branches, external and internal.

a. External iliac:

Supplies abdominal wall and urinogenital organs through pseudoepigastric branch and continues as femoral artery in the hind-limb.

Caudal abdominal:

Two. Arise from external iliacs and supply the structures in the posterior abdomen.

b. Internal iliac:

Runs backward and supplies the pelvic region and urinary bladder.

II. Pulmonary trunk:

Originate from the right ventricle, courses towards the dorsal side and bifurcates into right and left. The right pulmonary artery passes dorsal to the aortic arch, divides into four branches to supply four lobes of the right lung. The left pulmonary artery passes ventral to the aortic arch, divides into three branches to sup­ply three lobes of left lung.