The Systemic Left Heart Circulation

Aortic (left semilunar, aortic semilunar) valve

Svstemic arteries

Superior vena cava

Key:

Aortic (left semilunar, aortic semilunar) valve

Svstemic arteries

Superior vena cava

Key:

Fig. 11.6 An overview of the systemic (left heart) circulation.

(by-KUS-pid) valve. The bicuspid valve is a one-way valve having ''two'' (bi-) leaf-like flaps with ''points'' (cusps). Since the bicuspid valve is on the left side of the heart, it is also called the left atrioventricular or left A-V valve. In anatomy, of course, we have a multitude of names. Thus, the bicuspid or left atrioventricular (left A-V) valve is also known by a third name, the mitral (MY-tral) valve. This strange name comes from the fact that the valve closely resembles an inverted (upside-down) pointed hat of a bishop, which is called a miter (MY-ter). Hence, mitral literally ''pertains to'' (-al) a bishop's ''miter'' (mitr) (see Figure 11.7, A).

Blood is pushed through the bicuspid (left atrioventricular or mitral) valve, down into the left ventricle. The left ventricle is the main pump for the systemic circulation (including all the blood vessels in the entire body, except for those in the pulmonary circulation). The left ventricle powerfully contracts, sending blood up through the aortic (ay-OR-tik) valve. The aortic valve gets its name from the fact that it sits near the base of the aortic arch. Its alternate name is the left semilunar valve, since (like the right semilunar valve) its flaps are shaped much like half-moons. Thus the preferred name for this valve is the combined phrase, aortic semilunar valve (see Figure 11.7, B).

The blood goes up through the aortic semilunar valve, and into the aortic arch. Now, the aortic arch (and the lower portions of the aorta) send out numerous branches (smaller arteries), which either directly or indirectly

R semilunar (pulmonary, or pulmonary semilunar valve)

Fig. 11.7 Detailed anatomy and symbolism of the two types of heart valves. (A) A visual explanation for the alternate names of the left A-V valve. (B) A visual explanation for the names of the right and left semilunar valves.

Fig. 11.7 Detailed anatomy and symbolism of the two types of heart valves. (A) A visual explanation for the alternate names of the left A-V valve. (B) A visual explanation for the names of the right and left semilunar valves.

supply all the organ systems of the body (except for the lungs). Consequently, we can provide a general name and call these the systemic arteries. Particular systemic arteries are usually named for the bones by which they pass, or the parts of the body through which they pass. Familiar examples would include the brachial artery (in the ''arm''), and the femoral artery (in the ''thigh,'' or along the ''femur'').

Tissue 3

Tissue 3

As these systemic arteries go into some organ (such as a particular bone, skeletal muscle, the liver, or the brain), they branch into many systemic arterioles. Like rivers that successively divide into smaller creeks, the systemic arterioles subdivide into numerous systemic capillaries.

The systemic capillaries, being extremely thin walled, dump their oxygen (O2) molecules off to the tissue cells. As the O2 molecules diffuse out of the blood, and into the tissue cells, there is a diffusion of CO2 in the opposite direction. As a result, the blood in the second half of the systemic capillaries turns back to blue (actually dark, ''bluish''-red) in color.

The systemic capillaries merge together to join with the systemic venules. The systemic venules (like all types of venules) run together to create the systemic veins. The systemic veins carry blood away from the body organs, and back towards the heart. The systemic circulation finally ends with the two largest systemic veins - the superior and inferior vena cavae (KAY-veye). To briefly summarize:

THE SYSTEMIC (LEFT HEART) CIRCULATION: Begins with the left atrium —> Goes to and includes both the (and its left auricle) superior & inferior vena cavae

[Study suggestion: Go back and look through Figures 11.5 and 11.6. How many total one-way valves are present in the entire heart? How many of these are atrioventricular (A-V) valves? How many of these are semilunar valves?]

0 0

Post a comment