Lab 7

Question 1

What layer of the diaphragm does the fibrous pericardium fuse to?

Answer 1

• epimysium of diaphragm

- travelling along superficial surface of the fibrous pericardium is the phrenic nerve

Question 2

How might a stenosed pulmonary artery affect the thickness of the wall of the right ventricle?

Answer 2

• right ventricular hypertrophy
• stenosed pulmonary artery increases the resistance in the vessel so right ventricle has to pump harder because of increased pressure in right ventricle

Question 3

What results from plaque irritating the endothelium of a vessel wall?

Answer 3

• platelet deposition and subsequent thrombosis
• over time a thrombus, a fibrin network derived from clotted blood, deposits in the lumen of these vessels
• thrombus blocks the flow of blood, compromising the blood supply to the heart

Question 4

Why does the QRS complex have a larger amplitude than the P wave?

Answer 4

• ventricular muscles are larger
• electrical impulses in the atria are shorter and less voltage
• ventricles are large therefore give a larger wave on ECG when depolarized
• if edema is present, amplitude can’t properly spread so QRS is small

Question 5

At what point in the ECG does the S1 heart sound occur? What is happening to atrial and ventricular blood pressures at this time?

Answer 5

• occurs soon after ventricular systole near end of QRS wave

- pressure in both is rising

Question 6

At what point in the ECG does the S2 heart sound occur? What is happening to the pressure of blood in the aorta and the left ventricle at this time?

Answer 6

• S2 occurs when aortic semilunar valve closes at the end of the T wave
• pressure in aorta rises (dicrotic wave) due to rebounding of blood off closed cusps of semilunar valve
• ventricular pressure is dropping

Question 7

Describe the relationship between ECG and pulse

Answer 7

• pulse is wave of pressure you can feel through artery walls
• QRS complex represents electrical signal that tells ventricles to contract
• QRS on ECG and pulse wave signify systole

Question 8

Why is there a delay between the QRS complex and the upswing in the finger pulse record?

Answer 8

• QRS is electrical activity that occurs just before contraction
• slight delay to get to finger
• finger pulse is delayed in relation to heart sounds
• finger pulse’s rise begins after 1st sound and reaches peak at 2nd sound
• carotid wave would begin after 1st sound and would show dicrotic notch following 2nd sound
• dicrotic notch would allow 2nd sound

Question 9

Describe the pressure in the artery when taking systolic BP

Answer 9

• cuff creates high pressure that causes artery to collapse
• pressure in the cuff is released slowly and when the systolic pressure in the artery is greater than that in the cuff, blood flows momentarily to the arm through the partially collapsed artery
• this produces Korotkoff sounds at which stage cuff pressure is taken to approximate systolic pressure

Question 10

What are the 4 functions of the fibrous skeleton of the heart?

Answer 10

• electrically separate atria and ventricles
• maintain valve diameter
• structural foundation for valves
• provides attachment site for muscle of the heart

Question 11

What regulates the opening and closing of semilunar valves?

Answer 11

• changes in pressure on either side of the valve

- aortic and pulmonary valve have 3 semilunar cusps

Question 12

The aorta is classified as an elastic artery. What is the purpose of the elastic fibres in the aorta?

Answer 12

• help propel blood onwards while ventricles are relaxing
• walls stretch when blood is ejected into aorta and elastic fibres store mechanical energy acting as pressure reservoir
• elastic fibres recoil and convert stored energy in vessel into kinetic energy of blood

Question 13

How does atherosclerosis affect blood pressure?

Answer 13

• atherosclerosis causes narrowing of vessels which increases vascular resistance which increases blood pressure
• all patients with atherosclerosis have arteriosclerosis; arteriosclerosis is stiffening or hardening of atrial walls
• those with arteriosclerosis might not necessarily have atherosclerosis and increase in blood pressure is a risk factor for atherosclerosis

Question 14

What is continuous with the fibrous pericardium?

Answer 14

• connective tissue making up tunica adventitia of the major vessels and the epimysium of the diaphragm
• laterally where the pericardium is adjacent to the lungs the parietal (mediastinal) serous pleura is attached to the outer surface of the fibrous pericardium

Question 15

What is friction rub?

Answer 15

• does not demonstrate a murmur as the abnormal components of the sound are produced by inflamed pericardium chafing and sticking to the heart itself
• sound has been described as a leather against leather sound
• sounds like a 3 beat rhythm or a horse cantering
• abnormal component is a rough, scratchy sound, resulting from pericarditis

Question 16

What is mitral valve prolapse?

Answer 16

• when the mitral valve is separating the left atrium and ventricle is no longer adequately held in place by the chordae tendinae, it can evert during ventricular contraction
• this valve prolapse leads to blood flowing back into the left atrium
• abnormal vibration of the mitral valve is heard as a buzzing sound
• a mid-systolic click is also characteristic of mitral valve prolapse