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Cardiovascular system (CVS)

CVS consists of the heart and a series of blood vessels (arteries, veins and capillaries).

Introduction•A functional cardiovascular system is vital for supplying oxygen and nutrients to tissues and removing wastes from them.•The heart is the strongest muscle in the body •The heart must pump blood throughout the body day & night •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.•On your left side is the heart that pumps this O2 soaked blood out to your body.•Heart pumps 200,000000 L blood in a lifetime.•Both pumps are divided into 2 spaces called chambers so your heart is actually a 4-chambered pump.

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Main functions of the circulatory system

1) Transport and distribute essential

substances (oxygen and nutrients )

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)

Arteries:• 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:• 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 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:

•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.

•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.

•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)

•Pulmonary valve (3 cusps) – guards the base of the pulmonary trunk; opens as the right ventricle contracts

Chambers of the heartChambers 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.

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.

3)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

4)The left ventricle pumps blood by way of the aorta (large artery) into systemic circulation an aortic valve guards the base of the aorta

Heart Valves

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

The Heart: PumpsThe Heart: Pumps1) 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 circulationPulmonary circulation

The left heart pump: receives oxygenated blood from the lungs

(through pulmonary veins)pumps oxygenated blood to the rest of the

body Systemic circulationSystemic circulation

Type of circulation

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Blood Flow Through Heart

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Blood Flow Through Heart

The Heart beat• Each heart beat 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 Heart: The Heart: SystoleSystole

Systole: Systole: It is the contraction of the ventricles.

• 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: The Heart: DiastoleDiastole

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 each ventricle per minute.

• The cardiac output=C.O.P= S V × 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= 75× 72= 5,4 L/minute24