Phlebography

Impedance 4A04X51

Phleborrhaphy

Phlebotomy

Pulmonary and Systemic Circulation

Pulmonary Circulation

Pulmonary circulation begins with the right side of the heart, sending blood to the lungs to absorb oxygen (O₂) and to release carbon dioxide (CO₂). Note in Figure 9-2 that the vessels that carry blood to the lungs from the heart are blue—to show the blood as being deoxygenated, or oxygen deficient. Once the oxygen is absorbed, the blood is considered oxygenated, or oxygen rich. Note also in Figure 9-2 that the vessels traveling away from the lungs are red—to show oxygenation. The blood then progresses back to the left side of the heart, where it is pumped out to begin its route through the systemic circulatory system.

oxygen = ox/i, ox/o, oxy-

carbon dioxide = capn/o

Systemic Circulation

Systemic circulation carries blood from the heart to the cells of the body, where nutrient and waste exchange takes place. Certain organs of the body are key to the process of waste removal. During systemic circulation, blood passes through the kidneys. This part of systemic circulation is known as renal circulation. In this phase, the kidneys filter much of the waste from the blood to be excreted in the urine. Blood also passes through the small intestine during systemic circulation. This phase is known as portal circulation. Here, the blood from the small intestine collects in the portal vein, which passes through the liver. The liver filters sugars from the blood and stores them for use as needed. On return to the right side of the heart, the blood is pushed out to the lungs to dispose of its CO₂, absorb O₂, and repeat the cycle. Figure 9-2 shows the oxygenated/deoxygenated status of blood.

heart = cardi/o, coron/o, cordi/o

kidney = nephr/o, ren/o

renal

 ren/o = kidney

 -al = pertaining to

liver = hepat/o

lung = pulmon/o, pneum/o, pneumat/o

In systemic circulation, the blood traveling away from the heart first passes through the largest artery in the body called the aorta. From the aorta, the vessels branch into conducting arteries, then into smaller arterioles, and finally to the capillaries. Note in Figure 9-2 that the color has changed from the red of oxygenated blood to a purple color at the capillaries. This is the site of exchange between the cells’ fluids and the plasma of the circulatory system. Oxygen and other substances are supplied, and carbon dioxide is collected, along with a number of other wastes. Once the blood begins its journey back to the heart, it first goes through venules, then veins, and finally into one of the two largest veins, the superior or inferior vena cava. The great vessels include the pulmonary arteries and veins, the superior vena cava, and the thoracic aorta. The inferior vena cava is classified as a lower vein.

aorta = aort/o

vessel = vascul/o, angi/o, vas/o

artery = arteri/o

arteriole = arteriol/o

venule = venul/o

vein = ven/o, phleb/o

All of the vessels of the cardiovascular system (including the heart) share a lining of endothelial cells. While all carry blood, each type of vessel has a slightly different, but significant structure. Figure 9-3 illustrates these differences. The muscular, thick arteries are composed of three tunics, or coats: the outer layer is called the tunica externa (adventitia), the muscle layer and elastic layer are called the tunica media, and the inner layer is called the tunica interna (intima). Compare the thickness and structure of an artery to the thinner, valvular nature of veins. Veins do not have the thick muscle coat of the arteries to propel the blood on its journey through the circulatory system but instead rely on one-way valves that prevent the backflow of blood. In addition, skeletal muscle contraction provides pumping action. The capillaries have no coats, and their diameters are so tiny that only one blood cell at a time can pass through them.

 Note

The inferior vena cava is classified as a lower extremity vein. Remember, inferior means lower. Most of that vein is below the diaphragm.

 Exercise 1:

Pulmonary and Systemic Circulation

Match the following combining forms with their meanings. More than one answer may be correct.

____ 1. vein ____ 2. artery ____ 3. heart ____ 4. venule

____ 5. lung

____ 6. aorta

____ 7. arteriole

____ 8. vessel

A vas/o

B pulmon/o

C angi/o

D phleb/o

E arteri/o

F ven/o

Coronary Circulation and Blood Flow Through the Heart

Using Figure 9-5 as a guide, follow the route of the blood through the heart. The picture and arrows in this diagram are shaded red and blue to represent oxygenated and deoxygenated blood. Deoxygenated blood is returned to the heart through the venae cavae. The superior vena cava returns blood from the upper body, whereas the lower body is drained by the inferior vena cava. Blood is squeezed from the right atrium (RA) to the right ventricle (RV) through the tricuspid valve (TV). Valves are considered to be competent (capable) if they open and close properly, letting through or holding back an expected amount of blood. Once in the right ventricle the blood is squeezed out through the pulmonary semilunar valve into the pulmonary arteries (PA), which carry deoxygenated blood to the lungs from the heart. These are the only arteries that carry deoxygenated blood. The main pulmonary artery (pulmonary trunk) divides into right and left arteries to supply each lung. The conus arteriosus is the cone-shaped extension of the right ventricle into the pulmonary trunk. In the capillaries of the lungs, the CO₂ is passed out of the blood and O₂ is taken in. The now-oxygenated blood continues its journey back from the lungs to the left side of the heart through the pulmonary veins (PV). These are the only veins that carry oxygenated blood. The blood then enters the heart through the left atrium (LA) and has to pass the mitral valve (MV), also termed the bicuspid valve, to enter the left ventricle (LV). When the left ventricle contracts, the blood finally pushes out through the aortic semilunar valve into the aorta (the largest artery in the body) and begins yet another cycle through the body. The first part of the aorta, the ascending aorta, rises toward the head, then bends into the aortic arch and continues downward through the chest as the descending thoracic aorta. Once it passes the diaphragm, it is termed the abdominal aorta.

Each valve has a fibrous ring at its base called the annulus. The bicuspid valve has two leaflets (cusps) that are attached to two nipple-like papillary muscles by the chordae tendineae, cordlike tendons. The papillary muscles open and close the heart valves. The tricuspid valve has three leaflets attached to three papillary muscles, connected again by chordae tendineae. When a writer refers to heartstrings being tugged at in sentimental situations, he/she is referring to the chordae tendineae.

The amount of blood expelled from the left ventricle compared with the total volume of blood filling the ventricle is referred to as the stroke volume and is a measure of the ejection fraction of cardiac output. Typically around 65%, this amount is reduced in certain types of heart disease.

If a woman’s heart rate is 80 beats per minute (BPM), that means her heart contracts almost 5000 times per hour and more than 100,000 times per day, every day, for a lifetime. Truly an amazing amount of work is accomplished by an individual’s heart without a bit of conscious thought!

The heart muscle has its own dedicated system of blood supply, the coronary arteries (Fig. 9-6). The two main coronary arteries are called the left and right coronary arteries (LCA, RCA). The right coronary artery branches to form the posterior (interventricular) descending artery, which divides to form the atrioventricular artery and finally the posterior septal artery. The other main branch of the RCA is the marginal artery that divides to form the acute marginal artery. The left coronary artery branches to form the anterior (interventricular) descending branch, which continues to the anterior septal artery. It also forms a circumflex branch that divides into anterior and posterior ventricular branches. They supply a constant, uninterrupted blood flow to the heart muscle. Table 9-1 illustrates the path of blood through the coronary arteries. The return to the circulatory system is via the coronary veins, which deposit the deoxygenated blood into the coronary sinus, a small cavity where the blood is collected before it empties into the right atrium. The shallow grooves that hold these arteries on the surface of the heart are termed the left and right coronary sulci (sing. sulcus). In the human embryo, the sinus venosus is a hollow space that holds the blood as it returns to the heart. In normal development, the right side of the space becomes part of the right atrium. On the left side it becomes the coronary sinus and the oblique vein. One type of heart defect, an abnormal opening between the upper chambers of the heart (termed atrial septal defect) can result from abnormal development of the right side of this embryonic structure. The areas of the heart wall supplied by the coronary arteries are designated as the inferior, lateral, anterior, and posterior walls. The left margin (also called the obtuse margin) is formed mainly by the left ventricle. Table 9-1 shows where the blood goes after leaving the ascending aorta.

Table 9-1

Schematic Showing Coronary Arteries

Conductive Mechanism System

Systemic and pulmonary circulations occur as a result of a series of coordinated, rhythmic pulsations, called contractions and relaxations, of the heart muscle. The cardiac muscle is controlled by the autonomic nervous system, so (thankfully) the heart beats involuntarily. The normal rate of these pulsations in humans is 60 to 100 bpm and is noted as a patient’s heart rate. Figure 9-7 illustrates various pulse points, places where heart rate can be measured in the body. Blood pressure (BP) is the resulting force of blood against the arteries. The contractive phase is systole, and the relaxation phase is diastole. Blood pressure is recorded as systolic pressure over the diastolic pressure. Optimal blood pressure is a systolic reading less than 120 and a diastolic reading less than 80. Normal blood pressure is represented by a range. See the table below for blood pressure guidelines.

Blood Pressure Guidelines

	Systolic	Diastolic
Optimal	Under 120 and	Under 80
Normal	120-139 or	80-84
High-normal	130-139 or	85-89

The cues for the timing of the heartbeat come from the electrical pathways in the muscle tissue of the heart (Fig. 9-8) termed the conductive mechanism. The heartbeat begins in the right atrium at the sinoatrial (SA) node, called the natural pacemaker of the heart. The initial electrical signal causes the atria to undergo electrical changes that signal contraction. This electrical signal is sent to the atrioventricular (AV) node, specialized cardiac tissue that is located at the base of the right atrium proximal to the interatrial septum. From the AV node, the signal travels next to the bundle of His (also called the atrioventricular bundle), which carries the electrical impulse from the top to the bottom chambers. This bundle is in the interatrial septum, and its right and left bundle branches transmit the impulse to the Purkinje fibers in the right and left ventricles. Once the Purkinje fibers receive stimulation, they cause the ventricles to undergo electrical changes that signal contraction to force blood out to the pulmonary arteries and the aorta. If the electrical activity is normal, it is referred to as a normal sinus rhythm (NSR) or heart rate. Any deviation of this electrical signaling may lead to an arrhythmia, an abnormal heart rhythm that compromises an individual’s cardiovascular functioning by pumping too much or too little blood during that segment of the cardiac cycle.

 Note

If you see a bundle of Kent, you should realize that this is a congenital abnormal pathway between an atrium and a ventricle, not a normal anatomical structure.

Figure 9-9 is a visual representation of the conductive mechanism of the heart through the use of an electrocardiogram (EKG/ECG). You can see the relationship of the electrical activity of the heart to the flow of blood through its chambers.

electrocardiogram

 electr/o = electricity

 cardi/o = heart

 -gram = recording

When the SA node (the pacemaker of the heart) fires, the voltage of both atria decreases (referred to as depolarization). This drop in voltage appears as an upward tracing (termed a deflection) called a P wave. The P wave represents the atria contracting to push blood through their respective valves and into the ventricles.

The impulse next travels to the AV node, the AV bundle, and the Purkinje fibers. Once these fibers are activated, this sequence causes the ventricles to relax and contract. This depolarization appears as the QRS segment on an EKG.

The repolarization (the T wave) represents the recovery time when the atria fill with blood from the venae cavae and pulmonary veins.

The ST segment is an indicator of heart muscle function. Figure 9-10 shows the comparison among the normal tracing of an ECG with the one from a STEMI (ST elevation myocardial infarction) and one from an NSTEMI (non-ST elevation myocardial infarction).

 Exercise 2:

Heart and Great Vessels

A. Match the word parts with the meanings below.

____ 1. atri/o ____ 2. endocardi/o ____ 3. pericardi/o ____ 4. ventricul/o ____ 5. aort/o ____ 6. myocardi/o ____ 7. lun/o ____ 8. valv/o, valvul/o ____ 9. apic/o ____ 10. sept/o ____ 11. auricul/o ____ 12. trabecul/o ____ 13. chord/o ____ 14. cusp/o ____ 15. papill/o ____ 16. precordi/o ____ 17. epicardi/o ____ 18. coron/o

A heart muscle

B cord (used to describe the “heartstrings”)

C point

D structure that allows blood to flow through in one direction

E top chamber of heart

F little ear (structure on atrium)

G inner lining of the heart

H pointed extremity

I largest artery in the body

J moon

K little beam (used to describe fleshy tissue in ventricles)

L lower chamber of heart

M wall, between chambers

N sac surrounding the heart

O nipplelike structure (supports chordae tendineae)

P in front of the heart

Q structure on top of the heart

R heart, crown

Upper Arteries

After leaving the aortic arch, the upper arteries (Fig. 9-11) branch toward the arms and head. The route of blood to the arms is slightly different on the right than on the left. On the right, the innominate (also called the brachiocephalic) artery is considered a first order branch.

From it, the second order branch is the right subclavian artery, then the axillary artery, then the brachial artery, which divides into the radial and ulnar arteries, and finally those rejoin to form the palmar arches of the hand. On the left side of the body, the blood flows from the aortic arch to the left subclavian artery, on to the axillary artery, then to the brachial artery, which again divides into the radial and ulnar arteries, and then rejoins for the arteries of the hand at the palmar arch.

The blood supply to the right side of the head occurs through the right common carotid to the right internal and external carotid arteries, and from the right subclavian to the right vertebral artery. On the left, blood flows to the left common carotid and branches to the left internal and external carotid arteries. The external carotids branch to supply blood to the face through the facial artery (also called the external maxillary artery). The external carotids also branch to form the superficial temporal artery and the internal maxillary artery. The right and left subclavian also carry blood to the neck through the left and right vertebral arteries. In the brain, the vertebral arteries merge to form a single basilar artery which supplies the posterior part of the circle of Willis, a circular formation of arteries that supply blood to the brain. These arteries in the skull are referred to as intracranial arteries.

The main blood supply to the chest is carried from the thoracic aorta to the right and left internal mammary arteries (also called the internal thoracic arteries [ITA]) that branch from the right and left subclavian arteries. The blood supply to the thyroid is divided in two. The superior thyroid artery receives blood from the external carotid artery and supplies the upper part of the gland. The inferior thyroid artery, which supplies the lower part of the gland, receives its blood supply from the right and left subclavian arteries. The intercostal, bronchial, pericardial, esophageal, mediastinal, and superior phrenic arteries supply blood to the expected organs and structures.* Table 9-2 illustrates blood flow through the upper arteries.

Table 9-2

 Schematic Showing Upper Arteries

Upper Veins

The upper veins (Fig. 9-13) return blood to the heart from the head, neck, arms, and chest cavity. If you remember that the word parts for many of the veins tell you where they are returning blood from, you just need to pay special attention to which ones drain into the larger veins that collect blood from several different ones (e.g., the jugulars, brachiocephalics, and subclavians).

In the head and neck, the facial veins drain the superficial parts of the face while the intracranial veins (e.g., ophthalmic, cerebral) drain the deeper structures of the skull. The vertebral veins drain the blood from the brain near the bones of the neck. The external jugular veins drain the superficial veins of the head and neck, while the internal jugular veins drain blood from the deeper veins of the head and neck (including the intracranial veins). Both the internal and external jugular veins drain into the subclavian veins, located under the collarbones. The vertebral veins drain directly into the subclavian veins without a direct connection to one of the jugulars. The internal jugular joins the subclavian to form the brachiocephalic veins where the right and left sides merge to drain into the superior vena cava.

Blood is drained from the veins of the arms starting with the fingers and hands (e.g., palmar/volar digital and metacarpal veins). The deeper drainage of the lower arms is handled by the radial (lower lateral forearm) and ulnar (lower medial forearm) veins that anastomose (join) at the brachial vein. The brachial vein drains the upper arm, where it is eventually joined by the axillary vein, draining the area under the arm and continuing to join the subclavian, then brachiocephalic (innominate) vein, and finally the superior vena cava.

Superficial drainage of the arm is carried by the basilic veins that drain the hands and lower arm on the medial side of the arm and the cephalic veins on the lateral side. Both drain into the axillary vein and follow the same path back to the heart as the deeper veins described above. The median cubital vein (also referred to as the median basilic or antecubital vein) connects the basilic and cephalic veins and is often used as a site for blood draws. Note that the combining form cubit/o refers to the area of the elbow.

The chest area is drained by the azygos vein (azyg/o means “without a yoke,” meaning that it is a singular, not paired, vein) that resides in the thoracic cavity along with the hemiazygos vein and accessory hemiazygos vein that together collectively drain blood from the organs and tissues of the thoracic cavity. This includes the superior intercostal veins (draining the area between the upper ribs), the bronchial veins (draining the area around the airways of the lungs), and the pericardial veins (draining the sac surrounding the heart). The azygos vein drains the right side of the cavity, whereas the hemiazygos and accessory hemiazygos veins return blood from the left side of the same veins. These veins then drain back directly to the superior vena cava or through the brachiocephalic vein and then to the superior vena cava.