Circulation and Blood World’s Best Notes ...

Blood vessels

Arteries are defined as blood vessels that carry blood away from the heart. In most cases they are delivering oxygenated blood to the body tissues. This is the SYSTEMIC CIRCULATION (since it is going to the systems)

This is part of the PULMONARY CIRCUIT The pulmonary artery transports deoxygenated blood from the heart to the lungs. This is part of the PULMONARY CIRCUIT

Veins are defined as blood vessels that transport blood back to the heart. In the systemic circuit, they transport deoxygenated blood; In the pulmonary circuit, they transport oxygenated blood;

Arteries and veins have structural differences as well. The arterial wall are able to expand and receive a quantity of blood every time the heart pumps. Approximately 70 ml is pumped into the aorta with each contraction of the left ventricle. The resulting expansion of the walls of the arteries is detected as the pulse.

Arteries and veins have structural differences as well. The veins are relatively thin-walled. They do not receive any large volumes of blood or pressures from blood flow. Veins also contain valves to assist with the upward movement of blood back to the heart. The valves prevent back flow.

The third type of blood vessels are capillaries The third type of blood vessels are capillaries. These blood vessels are so tiny that they will only allow blood cells through them one at a time. They are also very thin-walled… thus helping with the delivery of materials to and from cells in a process of capillary fluid exchange

Two other types of blood vessels are often described Two other types of blood vessels are often described. They are arterioles and venules (small arteries and small veins). All the features of arteries and veins apply to arterioles and venules (respectively), but on a smaller scale. In addition, arterioles leading into a particular organ or region are equipped with sphincter muscles. When triggered, these can dilate or constrict to regulate blood pressure and flow to the intended capillary beds.

MAJOR BLOOD VESSELS

This is the major blood vessel carrying AORTA This is the major blood vessel carrying oxygenated blood out of the heart. It leaves the left ventricle, loops over the top of the heart creating the structure known as the aortic arch before descending along the inside of the backbone (= dorsal blood vessel). Branches from this blood vessel feed all the body systems except the lungs.

Coronary arteries and veins The very first branches off the aorta are the coronary arteries. These relatively small blood vessels can be seen on the surface of the heart. They feed the heart muscle. The heart does not receive its nutrients from the blood that travels through it. The muscle tissue is too dense and thick and the blood is travelling though it too hard and fast. The coronary veins take the "spent blood" back to the vena cava.

Carotid arteries These branches of the aortic arch take the blood to the head (including the brain). They are highly specialized in that they contain a number of different types of nerve endings: chemoreceptors that detect oxygen content, and pressure receptors that detect blood pressure changes. These features are essential for homeostasis. The carotid arteries run reasonably close to the surface, and the pulse in the carotids can usually be easily found along the sides of the neck.

Jugular veins Unlike most arteries, which are paired with veins having a corresponding name, the jugular veins are the match for the carotid arteries. As such, they conduct blood out of the head region to the anterior vena cava. The jugular veins do not contain valves. The blood flowing through them is under the influence of gravity. (When you stand on your head, the blood stays in your head!)

Subclavian arteries and veins The subclavian arteries also branch from the aorta (see diagram). The subclavians, as their name suggests travel under the clavicle (collarbone) and branch to feed the arms (brachial artery) and the chest wall etc. An interesting feature of the subclavian veins is that just before they join the anterior vena cava to return the blood to the heart, they meet up with the major lymphatic ducts.

Mesentaric arteries These arteries branch off the aorta as it travels posteriorly. They go to the intestines where they subdivide to form the capillaries that can be identified in the villi. In addition to feeding the organs of the digestive system, they pick up the newly digested nutrients and carry them away. The mesentaric vein is reduced in structure and function because of the hepatic portal vein.

Hepatic portal vein This vein transports blood rich with nutrients directly from the intestines to the liver. Hepatic means liver;portal indicates that there is a capillary bed on both ends of it. The liver detoxifies blood, destroys aged red blood cells, and regulates the glucose concentration in the blood

Hepatic vein When the blood leaves the liver it returns to the venous system. The hepatic vein carries the blood to the posterior vena cava.

Renal arteries and veins The renal arteries branch off the dorsal aorta as it passes through the lumbar region of the body. They take blood to the kidneys while the renal veins take blood away from the kidneys and back to the posterior vena cava.

Iliac arteries and veins When the dorsal aorta gets to the pelvic region, it branches into two iliac arteries, one goes down each leg. The femoral artery is a major branch of the iliac artery . The femoral artery services the large quadriceps muscle of the leg.

Anterior and Posterior Vena Cava The vena cavae collect up all the blood from the various veins of the systemic circuit and conduct it back into the right atrium. The anterior vena cava services the anterior part of the body, while the posterior services the posterior part. Note: anterior = superior posterior = inferior

Pulmonary veins and arteries Reflecting back on the difference between systemic and pulmonary circuits, all of the blood vessels listed so far are part of the systemic circuit. The pulmonary circuit is comprised of the pulmonary trunk and arteries that take deoxygenated blood from the right ventricle to the lungs while the pulmonary veins take oxygenated blood from the lungs to the left atrium.

For the rest … Blood, Antigens and Antibodies as well as Capillary Fluid Exchange, Fetal Circulation and the Lymphatic System see the handout. Once you’ve had a good read attempt the Vocabulary exercise for Unit J.