Introduction; The Cardiovascular System (CVS) Pathophysiology BMS 243 Lecture I Continued Introduction; The Cardiovascular System (CVS) Dr. Aya M. Serry 2015/2016

The human heart contains four valves: Cardiac valves and their functions The human heart contains four valves: Two Atrioventricular valves (AV valves) between the atria and the ventricles: Tricuspid valve between the right atrium and the right ventricle. Mitral valve between the left atrium and the left ventricle.

Cardiac valves and their functions Two semilunar valves: Aortic valve between the left ventricle and the aorta. Pulmonary valve between the right ventricle and the pulmonary artery.

Functions of the cardiac valves The cardiac valves allow the blood to pass only in one direction The AV valves : Allow for the blood to pass from the atria into the ventricles during ventricular diastole. During ventricular systole, the AV valves close to prevent back flow of blood from the ventricles into the atria.

Functions of the cardiac valves The semilunar valves: Allow for the blood to pass from the ventricles into the arteries during ventricular systole. During ventricular diastole, these valves prevent back flow of blood from the arteries into the ventricles (as these valves become closed during ventricular diastole).

The heart as a pump The heart is two pumps in series (the right and left sides) that are connected by the pulmonary and systemic circulations

PULMONARY AND SYSTEMIC CIRCULATIONS…

Blood Circulation In the human body, the blood circulates within the CVS in 2 circulations: Systemic or greater circulation: It starts from the left ventricle and it ends in the right atrium the heart as follows:

Blood Circulation The blood is pumped from the left ventricle of the heart to the aorta, then nutrients are given to the tissue cells and CO2 and waste products of metabolism are taken from them The blood is collected from the capillaries by the venules to the veins to the superior and inferior vena cava which carry the blood to the right atrium of the heart.

Blood Circulation Pulmonary or lesser circulation: It starts from the right ventricle and it ends in the left atrium of the heart as follows:

Blood Circulation The blood is then collected by the pulmonary veins which carry the blood to the left atrium of the heart. The blood then passes from the LA to LV where systemic circulation begin. The blood is pumped from the right ventricle to the pulmonary arteries & to the pulmonary capillaries (where exchange of O2 and CO2 occurs between the blood and the air in the alveoli of the lungs.

Blood flow from the heart During ventricular systole, blood is pumped into the circulation. During diastole, the pumping of blood stops and the ventricles get filled with blood. In this way, the flow of blood from the ventricles into the systemic and pulmonary circulations is an intermittent pulsatile flow.

Where Q = cardiac output, SV = stroke volume, and HR = heart rate. Cardiac output is the blood flow generated by each ventricle per minute. The cardiac output is equal to: ** the volume of blood pumped by one ventricle per beat (stroke volume) times the number of beats per minute (Heart Rate) Q = SV . HR Where Q = cardiac output, SV = stroke volume, and HR = heart rate.

Cardiac output The stroke volume for each ventricle averages 70 ml of blood, and a normal heart rate is approximately 70-75 beats/minute; therefore, the cardiac output at rest is ~ 5 L/min. The heart rate is under neural control. Cardiac sympathetic activity increases the heart rate, whereas parasympathetic impulses decreases heart rate.

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