08/10/20151 Cardiovascular system (CVS) CVS consists of the heart and a series of blood vessels (arteries, veins and capillaries).

Introduction 1) A functional cardiovascular system is vital for 2)supplying oxygen and nutrients to tissues and removing wastes from them. 3)The heart is the strongest muscle in the body 4)The heart must pump blood throughout the body day & night 5)The heart is 2 pumps working side by side. On your right side is the heart that pumps blood to your lungs where it picks up O2.

1)On your left side is the heart that pumps this O2-soaked blood out to your body. 2)Heart pumps 200,000000L blood in a lifetime 3)Both pumps are divided into 2 spaces called chambers so your heart is actually a 4-chambered pumper 4)The 2 sides do not work independently; they are precisely timed.

08/10/20154

Main functions of the circulatory system 1)Transport and distribute essential substances to the tissues. 2)Remove metabolic byproducts. 3)Adjustment of oxygen and nutrient supply in different physiologic states. 4)Regulation of body temperature. 5)Humoral communication.

Cardiovascular system

The Blood Vessels The CVS has three types of blood vessels: Arteries (and arterioles), Capillaries, Veins (and veinules) The Arteries and arterioles take blood away from the heart. The largest artery is the aorta. The middle layer of an artery wall consists of smooth muscle that can constrict to regulate blood flow and blood pressure. Arterioles can constrict or dilate, changing blood pressure

Capillaries have walls only one cell thick to allow exchange of gases and nutrients with tissue fluid. Capillary beds are present in all regions of the body but not all capillary beds are open at the same time. Contraction of a sphincter muscle closes off a bed and blood can flow through an arteriovenous shunt that bypasses the capillary bed. Veins Venules drain blood from capillaries, then join to form veins that take blood to the heart. Veins have much less smooth muscle and connective tissue than arteries. Veins often have valves that prevent the backward flow of blood when closed. Veins carry about 70% of the body’s blood and act as a reservoir during hemorrhage.

Figure 15-3: Metarterioles

. The heart is divided into 4 hollow chambers-2 atria (upper) & 2 ventricles (lower) Right chambers & valves: 1)right atrium Receives blood from 2 large veins called the superior vena cava & the inferior vena cava; coronary sinus also drains blood into the right atrium from the myocardium 1)Tricuspid valve (3 cusps) guards the atrioventricular orifice between the right atrium & the right ventricle; it permits blood to move from the right atrium into the right ventricle & doesn’t allow it to move in the opposite direction;

Chambers of the heart  The atria are smaller with thin walls, while the ventricles are larger with thick walls (much stronger): The left ventricle has thicker wall than the right because it needs to pump blood to the whole body.

Right ventricle pumps blood a short distance to the pulmonary trunk (lungs); blood goes to pulmonary trunk which divides to form the left & right pulmonary arteries (deoxygenated blood) 1) Pulmonary valve (3 cusps) – guards the base of the pulmonary trunk; opens as the right ventricle contracts Left chambers & valves: 1)left atrium receives blood from the lungs through 4 pulmonary veins – 2 from right & 2 from left lungs 2) The blood passes from the left atrium into the left ventricle through the atrioventricular orifice; bicuspid or mitral valve guards the left atrioventricular orifice; it prevents blood from flowing back into the left atrium from the ventricle when the ventricle contracts 3)The left ventricle pumps blood by way of the aorta (large artery) into systemic circulation an aortic valve guards the base of the aorta

The left ventricle’s myocardium is thicker than the right ventricle’s myocardium in order to: contract with a greater pressure

Heart Valves

- Which blood vessel receives blood from the left ventricle during systole? aorta

Heart Valves Atrioventricular 1)Tricuspid 2)Bicuspid or mitral Prevent blood from flowing back to Right or left atrium Semilunar valves 1)Aortic 2)Pulmonary Prevent blood from flowing back to Right or left Ventricle

When aortic pressure is greater than the ventricular pressure: the aortic semilunar valve closes

- When aortic pressure is less than ventricular pressure, this causes:. the aortic semilunar valve to open

The Heart: Pumps 1) The right heart pump:  receives deoxygenated blood from all parts of the body except the lungs (through superior & inferior vena cava)  pumps deoxygenated blood to the lungs Pulmonary circulation  Pulmonary circulation The left heart pump:  receives oxygenated blood from the lungs (through pulmonary veins)  pumps oxygenated blood to the rest of the body Systemic circulation  Systemic circulation

Type of circulation

08/10/ Blood Flow Through Heart

20-27 Blood Flow Through Heart

Cardiovascular system Cardiac cycle -It is the period which passes from the beginning of one beat until the beginning of the next one. -The cardiac cycle takes 0.8 sec. when the heart rate is 75 beats per minute. -During the cardiac cycle there are certain stages which are: 1.Stage of filling of the heart with blood. 2.Stage of contraction of the cardiac muscle. 3.Stage of ejection of blood. 4.-stage of relaxation.

The Heartbeat  Each heartbeat is called a cardiac cycle.  When the heart beats, the two atria contract together, then the two ventricles contract; then the whole heart relaxes.  Systole:- is the contraction of heart chambers;  Diastole:- is the relaxation of heart chambers  The heart sounds:- Lub-dup,  Lub:- is due to the closing of the atrioventricular valves,  Dup:- is due to closing of the semilunar valves.

The tricuspid valve is normally closed: while the ventricles are in systole

The Heart: Systole Systole: Systole:It is the contraction of the entricles. When the ventricles contract  they force the blood into the great arteries.  From the left ventricle into the aorta  From the right ventricle into the pulmonary artery. The increased pressure that result due to the contraction of the ventricles is called systolic pressure.

The Heart: Diastole Diastole : It is the relaxation of the ventricles.  When the ventricles relax  they receive the blood from the atria.  The decreased pressure due to the relaxation of the ventricles is called diastolic pressure.

Cardiac out put Is the volume of blood ejected by the left ventricle per minute The cardiac output=C.O.P= S V x HR S V : Stroke volume: is the volume of blood ejected by each ventricle per beat. = 75 ml of blood HR: = Heart rate: is the number of heart beat per minute = 72 beat/ minute COP= 75x 72= 5,400 L/ minute 33

Cardiovascular system Stroke volume -It is the volume of blood pumped by each ventricle per beat. -Normally it is about 70 ml/beat. -The stroke volume of left ventricle = that of right side ‼ -The stroke volume is determined by the venous return. -Cardiac output (COP) -It is the amount of the blood pumped by each ventricle per minute. -It is about 6 liters / minute at rest. -It can increase to 25 liters/min. during violent exercise.

Cardiovascular system _ Cardiac output = stroke volume x heart rate. -So, the COP is increased by an increase in stroke volume or heart rate or both. -Factors affecting cardiac output. 1.Venous return. 2.Force of heart contraction. 3.Frequency of the heart rate. 4.Blood pressure.

- Excessively high heart rate (>180) can reduce cardiac output because: it reduces the time for ventricular filling which reduces stroke volume