BN Ch.22 The Cardiovascular System Flashcards
1
Q
Describe the three major layers of the heart wall and how they relate to the pericardium; identify the three layers of arteries and veins.
A
- The heart wall has three layers:
- Endocardium
- The endocardium (inner heart) is a membrane lining the heart’s interior wall. It is made up of endothelial tissue, small blood vessels, and some smooth muscles.
- Myocardium
- Thick, strong muscles make up the myocardium ( myo = muscle), the middle and thickest layer. Cardiac muscle (Chapter 18) is a unique type of involuntary muscle with lightly striated cells, found only in the heart.
- Epicardium
- The epicardium ( epi = upon) is the thin, outer layer of the cardiac wall (also called the visceral layer of the serous pericardium). It is composed of squamous epithelial cells over connective tissue.
- The epicardium portion of the heart wall, which also makes up the pericardium’s visceral layer, adheres to the heart’s surface.
- (A space between the visceral and parietal layers is the pericardial space or cavity.
- It houses a small amount of serous fluid, pericardial fluid , which acts as a lubricant and reduces friction between the layers as the heart contracts and relaxes.)
- The parietal layer:
- is the inner serous pericardium .
- The outermost layer:
- is the fibrous pericardium (composed of dense fibrous connective tissue).
- This tissue protects and anchors the heart in the mediastinum and prevents overfilling.
The layers within arteries and veins are as follows:
- Tunica adventitia , the outermost layer, is composed of connective tissues and nerve cells, as well as nutrient capillaries in larger vessels. This layer protects the outside of the vessel.
- Tunica media , the middle layer, contains the thickest elastic fibers, as well as connective tissue composed of polysaccharides. This layer is covered by a thick elastic band (the external elastic lamina ) and smooth muscle fibers, which control vessel’s caliber (size).
- Tunica intima , the innermost layer, is the thinnest, a single layer of simple squamous endothelium (Fig. 15-10), held together by an intercellular matrix. This layer is surrounded by connective tissue interlaced with elastic bands ( internal elastic lamina)
2
Q
Identify and describe the function of the heart chambers, major vessels that enter and exit each chamber, and the atrioventricular valves, semilunar valves, chordae tendineae, and papillary muscles.
A
Chambers The interior of the heart is divided into four chambers. (Right/Left Atrium, Right/Left Ventricle).
- Atria
- The two upper chambers are the right and left atria (singular: atrium).
- These thin-walled, low-pressure chambers are receiving centers for blood.
- Ventricles
- The two lower chambers are right and left ventricles .
- Ventricles are high-pressure chambers; they pump blood out of the heart.
- The left ventricle must contract with sufficient force to send blood to the entire body; therefore, its muscle walls are thickest and its internal pressures the highest.
- The right ventricle needs only to pump blood into the low-pressure lungs; therefore, it is a thinner walled chamber.
- The left ventricle contains the heart’s thickest muscles and must pump strongly enough to send blood out to the entire body.
- The right ventricle also has thick muscles; the muscles in the atria are thinner than those of either ventricle.
- Atrioventricular Valves
- The atrioventricular ( AV ) valves lie between the atria and ventricles.
- The valve between the right atrium and right ventricle, the tricuspid valve , is formed of three flaps (cusps) of tissue.
- The valve between the left atrium and left ventricle, the mitral or bicuspid valve , has only two flaps of tissue.
- The tissue flaps of these valves attach to tendon-like strands, the chordae tendineae (tendinous cords), which are anchored to papillary muscles located on the inner surface of the ventricles.
- Blood flows from the atria to the ventricles through open AV valves when ventricular pressure is lower than atrial pressure.
- During this time, the papillary muscles and chordae tendineae relax.
- As the ventricles contract, increased pressure causes the AV valves to close.
- The papillary muscles also contract at this time, tightening the chordae tendineae, to prevent the valve cusps from everting (turning inside out).
- If the AV valves, chordae tendineae, or papillary muscles become damaged, backflow of blood ( regurgitation ) into the atria can occur with ventricular contraction.
- Overflow valves
- Each ventricle empties through a valve with three crescent-shaped (half-moon) cusps, the semilunar valves.
- The pulmonary semilunar valve ( pulmonic valve ) separates the right ventricle from the pulmonary artery.
- The aortic (semilunar) valve separates the left ventricle from the aorta, the body’s largest artery.
- Increased ventricular pressure, as when the ventricles contract, opens the semilunar valves.
- As the ventricles relax, blood begins to flow backward toward the ventricles.
- Blood fills the semilunar cusps and causes the valves to close.
- Therefore, semilunar valves prevent backflow from their respective arteries into their ventricles.
3
Q
Compare and contrast the structure and function of arteries, capillaries, and veins.
A
- Arteries:
- Arteries are elastic and smooth (involuntary) thicker muscular tubes that, with the exception of the pulmonary artery, carry oxygenated blood to body cells.
- They are known as “resistance vessels” because they can support high pressures and hold large volumes of blood.
- Capillaries:
- A capillary is microscopic, about 8 μm (micrometers—1/8 millionth of a meter).
- Blood flow through capillaries is known as microcirculation .
- Capillaries are composed of a single layer of endothelial cells.
- They are so small that tiny red blood cells must pass through them in single file.
- Capillaries make up most of the great length of the body’s blood vessels.
- In the capillaries, overall resistance is very low, so blood flows very slowly, allowing time for oxygen and nutrients to leave blood vessels and enter body tissues.
- Veins:
- At the same time blood is delivering materials to cells, it is picking up waste products.
- From capillaries, blood starts back toward the heart through venules , the smallest veins.
- Venous branches grow larger and become fewer as they near the heart, until finally blood reaches the body’s largest veins, the superior vena cava ( SVC ) and inferior vena cava ( IVC ) (plural: cavae).
- These two large veins return blood to the right atrium.
- The SVC returns blood from the head, neck, and arms, and the IVC returns blood from the lower body.
- Venous blood is dark red because oxygen has been replaced with carbon dioxide and other wastes.
4
Q
Describe the path of an electrical impulse through the heart’s conduction system; describe the purpose of this electrical activity.
A
- SA (sinoatrial) node (pacemaker) →
- AV (atrioventricular) node →
- Bundle of His (AV bundle) →
- Right and left bundle branches →
- Purkinje fibers to muscles of ventricles
- The electrical activity of the heart must occur before mechanical, pumping, activity of the heart can respond with a heartbeat.
5
Q
Explain the events associated with S 1 and S 2 heart sounds, indicating where each of these sounds is best heard.
A
- The first normal heart sound ( S 1 ) is called the “lub” and is produced by closure of the AV valves when the ventricles contract.
- The second heart sound ( S 2 ) is called the “dub” or “dup” and is produced by the closure of the aortic and pulmonary semilunar valves when the ventricles relax.
- Thus, S 1 occurs at the beginning of systole and S 2 occurs at the beginning of diastole.
- The first sound is loudest and longest. It can be heard over the entire pericardium but is usually loudest at the apex of the heart.
- S 2 is more easily heard at the base of the heart.
6
Q
Describe cardiac output, including factors involved in its regulation.
A
- Cardiac output ( CO )
- The amount of blood pumped by the ventricles in 1 minute, is normally from 4 to 6 L in the resting adult.
- Stroke volume ( SV ), the volume of blood ejected by the left ventricle with each heartbeat, is only about two-thirds of the blood contained in the left ventricle.
- CO is related to SV and beats per minute (heart rate—HR)
- Factors called preload and afterload can affect SV.
- Preload is the amount of pressure or “stretching force” against the ventricular wall at end diastole (maximum relaxation of the heart).
- When more blood volume is returned to the ventricles, the muscle fibers in the ventricles stretch to accommodate the excess.
- Starling law states that the greater the stretch, the greater the following force of contraction ( contractility ).
- The greater the contraction, the more volume ejected, resulting in increased SV.
- Afterload , the amount of pressure or resistance the ventricles must overcome to empty their contents, must be powerful enough to overcome resistance in the aorta and other arteries.
7
Q
Differentiate between systolic and diastolic blood pressure, explaining the actions occurring during each. Identify major factors that affect blood pressure regulation.
A
- Systolic
- In less than 1 second, both atria contract as both ventricles relax.
- Immediately, both ventricles contract as both atria relax.
- This process is considered one cardiac cycle or one heartbeat.
- This sequence of dual contractions, the atria followed by the ventricles, is called systole .
- Systole takes up one-third of the cardiac cycle.
- Diastolic
- Atrial relaxation, followed by ventricular relaxation, is called diastole.
- Diastole takes up two-thirds of the cardiac cycle, allowing time for the chambers to fill adequately with blood.
- One cardiac cycle is made up of systole of the atria and ventricles and diastole of the atria and ventricles.
- These contraction and relaxation processes occur almost simultaneously on the left and right sides of the heart.
- The contraction that pumps blood from the heart is systole; the period of heart relaxation is diastole.
- The heart is actually in systole twice, once for the atria (atrial systole) and once for the ventricles (ventricular systole).
- In addition, both atria and ventricles have periods of diastole. Systole diastole = one cardiac cycle.
- The autonomic nervous system can respond to changes, such as increased exercise, and speed up the cardiac cycle.
- Blood pressure regulating systems include the nervous, endocrine, cardiovascular, and urinary systems.
8
Q
State changes in the cardiovascular system caused by aging. Discuss related nursing implications.
A
- Increased rigidity of blood vessels (decreased elasticity and calcification—arteriosclerosis)
- Fat and cholesterol deposits in arteries (atherosclerosis)
- Dilation of blood vessels, due to weakening muscle tone; blood vessel damage
- Reduced coronary artery blood flow
- Blood vessel occlusion
- Malfunction of venous valves
- Fibrosis in heart conduction system; fewer pacemaker cells; decrease in AV bundle fibers
- Calcification and fatty accumulation in heart valves
9
Q
The cardiovascular system consists of the
heart and the blood __________.
A
Vessels
10
Q
__________ heartbeats that increase with age should not automatically be considered an indicator of disease.
A
Ectopic
11
Q
To adapt to the body’s metabolic needs, the heart can alter its __________ output.
A
Cardiac
12
Q
__________ is the amount of pressure or resistance the ventricles must overcome to empty their contents.
A
Afterload
13
Q
The rhythmic expansion of the arterial wall
as the blood flows through it is the __________.
A
Pulse
14
Q
A membrane lining the heart’s interior wall
A
Endocardium
15
Q
Thick, strong muscles making up the middle layer
A
Myocardium
