The
general structure of the circulatory system of the rat is almost identical to
that of humans. Pulmonary circulation carries blood through the lungs for oxygenation
and then back to the heart. Systemic circulation moves blood through the body
after it has left the heart. You will begin your dissection at the heart. It
is important that you do not cut the vessels as you carefully remove any muscles
and surrounding tissue to expose them.
Trace the flow of blood from the right atrium to the lungs and then back to the heart, you may not be able to locate all these structures due to the placement of the heart and vessels, but you should be able to find a few of them and label all of them on a diagram.
1. Blood from the posterior
portion of the body enters the right atrium of the heart through the inferior
vena cava. The inferior vena cava is also referred to as the caudal vena
cava.
2. Blood from the anterior parts of the rat enter the heart from the right
and left superior vena cava, also known as the cranial vena cava.
3. Blood flows from the right atrium to the right ventricle via
the tricuspid valve.
4. Blood is then pumped
through the pulmonary semilunar valve and into the pulmonary trunk,
which divides into the left and right pulmonary arteries - these are
the only arteries in the body that carry deoxygenated blood.
5. Blood then flows through the pulmonary arteries to the lungs where it is
oxygenated and then returns from the lungs to enter the left atrium via four
pulmonary veins.
5. Blood goes from the left atrium to the left ventricle via the
biscupid (or mitral) valve.
Blood leaves the left ventricle of the heart through the aortic semilunar valve and enters the aorta. The aorta has four general areas:
ascending aorta -
begins at the semilunar valve of the left ventricle and passes outside and over
the left and right atrial.
aortic arch - the place where the aorta bends to the left.
descending aorta - after the bend, the aorta can be traced toward the
diaphragm
abdominal aorta - the aorta passes through the diaphragm and supplies
blood to the lower extremities and organs
1. Coronary arteries
are located on top of the heart and supply the heart itself with blood.
2. The first visible branch from the aorta is the brachiocephalic artery,
it divides into the right common carotid artery, which supplies the right
side of the neck, and the right subclavian artery, which supplies the
right shoulder and arms.
3. At the most anterior part of the bend in the aortic arch is the left common
carotid artery, which supplies blood up the left side of the neck.
4. Immediately to the left of the left common carotid artery is the left
subclavian artery, which supplies blood to the left shoulder and arm.
*note that the branches
are not symmetrical. 
1. The right subclavian
artery branches from the brachiocephalic artery - it then passes under the clavicle
and branches into the right internal mammary artery (look alongside the
the chest wall) and the right axilllary artery which leads toward the
armpit.
2. The left subclavian artery branches in a similar way to form the left
internal mammary and the left axillary.
3. The right common cartoid passes along the neck toward the head where it gives
rise to the right external carotid artery and the right internal carotid
artery.
4. Similarly, the left common carotid can be traced toward the head where it
branches into the left external cartoid artery and the left internal
carotid artery.
Procedure:
Carefully tease away the muscles and tissue so that the right subclavian, the
right axillary and the right common carotid can be seen.
1. Push the abdominal organs
to the left to locate the arteris. The first arterial branch from the abdominal
aorta (below the diaphragm) is the celiac artery which branches to arteries
that supply the stomach (gastric artery), liver (hepatic artery),
spleen and pancreas (splenic artery) .
2. The second artery arising from the abdominal artery is the superior mesenteric
artery, which is larger than the celiac, and delivers blood directly to
the small intestine.
3. The renal arteries are short and lead directly to the kidneys.
4. Just posterior to the renal arteries are the genital arteries, which
lead to the testes or the ovaries.
5. Farther along the abdominal aorta, you can find the iliolumbar arteries
which lead to the dorsal muscles of the back.
6. Next, the inferior mesenteric artery leads to the intestinal mesenteries.
7. The abdominal aorta gives rise to the caudal artery, which goes on
into the tail.
8. The abdominal aorta finally divides to form the iliac arteries, which
deliver blood to the pelvis and hind legs.
9. The iliac arteries lead to the femoral artery in the leg.
Procedure:
Carefully tease away the muscles and tissue so that the the iliac and the femoral
arteries can be seen.
Trace
the Systemic Veins1. The left and right
superior vena cava conduct blood from the upper part of the body into the
right atrium. Trace these veins from the atrium until you find the small internal
jugular vein and continues as the subclavian vein.
2. The subclavian vein divies into the external jugular vein and the
axillary vein.
3. The inferior vena cava carries blood from the lower part of the body to the
right atrium. The hepatic vein drains the liver and enters the inferior
vena cava near the diaphragm.
4. Renal veins drain the kidneys.
5. Genital veins lead from the gonads and enter the inferior vena cava.
6. The iliac and
femoral veins drain the legs.
7. The caudal vein drains the tail.
A portal system is a system of veins that carries blood from one bed of capillaries to another bed of capillaries. The hepatic portal system carries blood from the mesenteries, small intestine, spleen, somach and pancres to the liver. Specifically, the gastic, splenic, and mesenteric veins drain the digestive system and unit to form the hepatic portal vein which carries the blood to the liver.
The liver is strategically located to receive blood after nutrients have been absorbed in the intestinal tract. The liver cells can easily modify these nutrients and remove toxins.
The vessels of the hepatic
portal system may be difficult to find. 