The Heart and Major Blood Vessels

Identify the major features of the heart

• Heart and Mediastinum

Describe the anatomical pathway of blood through the heart

Superior/Inferior vena cava (from body) --> right atrium --> tricuspid valve --> right ventricle --> pulmonary valve --> pulmonary artery --> lungs --> pulmonary veins --> left atrium --> mitral (bicuspid) valve --> left ventricle --> aortic valve --> aorta (to body)

Identify the major blood vessels of the head, heart, abdomen, and upper and lower limbs

The first thing you need to know in identifying blood vessels is how to tell an artery and a vein apart. Both arteries and veins have three main layers: a tunica intima (simple squamous endothelial lining), tunica media (elastic tissue and smooth muscle), and tunica externa (elastic tissue and collagen), though the relative thickness of each depends on the type of vessel. Arteries carry blood away from the heart and since it is usually at a high pressure, the muscular tunica media is quite thick in order to help withstand the pressure. Veins carry blood back to the heart and has a much thinner tunica media, plus a higher ratio of collagen to elastin. Since the pressure is much lower in veins, they have valves to prevent backflow.

Major vessels of the head

The major vessels supplying the head are the carotid arteries. There are two common carotid arteries (left and right). The left common carotid branches directly off the ascending aorta, whereas the right common carotid branches off the brachiocephalic trunk. Each of the common carotid arteries branches into an internal carotid and an external carotid. The internal carotid supplies the brain, whereas the external carotid supplies the face.

The major vessels draining the head are the jugular veins. The external jugular veins drain the back of the head, whereas the internal jugular veins drain the face. The jugular veins drain into the subclavian veins, uniting to form the brachiocephalic veins. The brachiocephalic veins (left and right) drain into the superior vena cava, which goes to the right atrium.

Major vessels of the heart

The major vessels supplying the heart are the coronary arteries, which are the first arteries to come off the ascending aorta. The pattern of arteries supplying the heart can be very variable, but there are some that are pretty common to most people. Most people have a left and right coronary artery, and the left usually branches off into the anterior interventricular artery (a.k.a. left anterior descending artery) and left circumflex artery.

Major vessels of the abdomen

The major vessels supplying the abdomen are the branches of the descending aorta. There are three sets of paired arteries, as well as three unpaired arteries. The three paired arteries are the suprarenal arteries (supplying the adrenal glands), the renal arteries (supplying the kidneys), and the gonadal arteries (supplying the ovaries or testes). The three unpaired arteries are the coeliac artery, superior mesenteric artery, and inferior mesenteric artery.

The venous system has similar paired veins, but there's also something interesting going on: the hepatic portal system. The mesenteric veins, which drain the intestines, take the food that we've just absorbed to the liver via the hepatic portal vein. From there, the liver is drained by the hepatic veins. In the liver, we have veins going to capillaries which are going to veins, rather than arteries going to capillaries which are going to veins.

Major vessels of the upper limb

Some of the vessels of the upper limb are really just one big vessel joined together, but named different things depending on which region you're looking at. At the top of the upper limb, where the clavicle is, the arteries are called subclavian arteries. The subclavian arteries become the axillary and then the brachial arteries as they go down. The brachial arteries then divide into the radial and ulnar arteries, depending on which bone they are next to. Veins are named similarly, though there are some superficial veins as well.

Major vessels of the lower limb

The lower limb vessels are similar to the upper limb vessels, in that they run into each other: you have iliac arteries that become femoral arteries that branch into anterior and posterior tibial and fibular arteries. Once again, veins are kind of similar, plus a few superficial veins.