Chapter 11- Part 1The Cardiovascular System

The Cardiovascular SystemThe Cardiovascular System A closed system of the heart

and blood vessels The heart pumps blood

Blood vessels allow blood to circulate to all parts of the body

The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products

The HeartThe Heart

Location Within the bony

thorax and is flanked on each side by the lungs

Shape and Size Pointed apex directed toward left hip and rests

on the diaphragm The broader base (posterior/superior aspect of

heart) points towards the right shoulder and lies beneath the 2nd rib

About the size of your fist

The Heart: CoveringsThe Heart: Coverings The heart is covered by a

double sac of serous membrane, the pericardium.The pericardium contains twolayers:1. Visceral Pericardium (Epicardium) – Layer

next to heart; Tightly hugs the exterior surface of the heart; Actually forms part of the heart wall

2. Parietal Pericardium - Outside layer; Fibrous layer that helps protect the heart and anchors it to surrounding structures (diaphragm and sternum)

The Heart: CoveringsThe Heart: Coverings

Serous Fluid - Fills the space between the layers of the pericardium Slippery, lubricating fluid Allows the heart to beat easily in a relatively

frictionless environment as the pericardial layers slide smoothly across each another

Pericarditis – Inflammation of the pericardium; Often results in the decrease in the amount of serous fluid Painful adhesions result that interfere with

heart movements (layers stick to each other)

The Three Layers of the Heart WallThe Three Layers of the Heart Wall

1. Epicardium Outside layer This layer is the

visceral pericardium already described

Connective tissue layer2. Myocardium

Middle layer Mostly cardiac muscle; layer that actually contracts

3. Endocardium Inner layer Thin glistening sheet of endothelium that lines the

heart chambers

The Heart: ChambersThe Heart: Chambers

Right and left side act as separate pumps

Four chambers Atria - Receiving chambers

• Not important in the pumping activity of the heart• Right atrium and left atrium

Ventricles - Discharging chamber Actual pumps of the heart Thick walled Right ventricle and left ventricle

The Heart: ChambersThe Heart: Chambers

The heart is somewhat twisted: Anterior surface of the

heart is formed mostly by the right ventricle

The apex of the heart is formed by the left ventricle

The Heart: ChambersThe Heart: Chambers

Septums that divide the heart longitudinally: Interventricular Septum – Divides

and separates the two ventricles from each other

Interatrial Septum - Divides and separates the two atria from each other

The Heart: ChambersThe Heart: Chambers

The heart functions as a double pump: Right Side:

Pulmonary circuit pump

Left Side: Supply all body tissues

The Heart: Associated Great VesselsThe Heart: Associated Great Vessels

Aorta - Leaves left ventricle

Pulmonary Arteries - Leave right ventricle

Vena Cava - Enters right atrium

Pulmonary Veins (four) - Enter left atrium

Blood CirculationBlood Circulation

1. The superior and inferior vena cava deliver oxygen poor blood from the veins of the body to the right atria

2. Right ventricle

3. Pulmonary arteries to the lungs to get oxygen and drop off carbon dioxide

4. Oxygen rich blood is returned to the left side of the heart through the four pulmonary veins

5. Left atria

6. Left ventricle

7. Oxygen rich blood is pumped out of the heart into the aorta, from which the systemic arteries branch to supply essentially all body tissues

Blood CirculationBlood Circulation1. Pulmonary Circulation – Circulation from the

right side of the heart to the lungs and back to the left side of the heart • It’s only function is to carry blood to the lungs for

gas exchange and then return it to the heart

2. Systemic Circulation – Circulation from the left side of the heart to the body tissues and back to the right side of the heart• It supplies oxygen- and nutrient-rich blood to all

body organs

Blood CirculationBlood Circulation

Figure 11.3

Thickness of the VentriclesThickness of the Ventricles Left Ventricle

Is the systemic pump that pumps blood over a much longer pathway Its walls are

substantially thicker than those of the right ventricle

More powerful pump than the left ventricle

Right Ventricle Not as powerful or as

thick as the left ventricle

The Heart: ValvesThe Heart: Valves Allow blood to flow in

only one direction Four valves total (two

AV valves and two semilunar valves) Atrioventricular (AV) Valves – Located

between the atria and ventricles Left AV Valve – Called the bicuspid valve or the

mitral valve (contains two cusps or flaps) Right AV Valve – Called the tricuspid valve

(contains three cusps or flaps)

The Heart: ValvesThe Heart: Valves

Semilunar Valves – Located between the ventricle and artery Pulmonary

Semilunar Valve – Right side of heart (contains three cusps)

Aortic Semilunar Valve – Left side of heart (contains three cusps)

The Heart: ValvesThe Heart: Valves

Valves open (flaps hang limply) as blood is pumped through

Close to prevent backflow

As the ventricles contract, the pressure causes the flaps to be forced upward, closing the valves

The Heart: ValvesThe Heart: Valves The flaps of the AV

valves are held in a closed position by the chordae tendineae

Tiny white cords

Anchor the cusps to the walls of the ventricles, so that they don’t blow upward into the atria (like an umbrella being turned inside out by a gusty wind)

The Heart: ValvesThe Heart: Valves Each set of valves operates at a different time -

The AV Valves: Open during heart relaxation Closed when the ventricles are contracting

Semilunar Valves: Open (forced open) when the ventricles contract Closed during heart relaxation

The “lub-dup” sound of the heart is from the opening and closing of the valves.

Faulty ValvesFaulty Valves The heart can function

with “leaky” valves as long as the damage is not too great.

However, severely deformed valves can seriously hamper cardiac function. If blood backflows too much, the heart repumps

the same blood. If the flap stiffens, the heart’s workload increases,

and ultimately the heart weakens and may fail.

Faulty ValvesFaulty Valves

Treatment: A faulty valve can be replaced with a synthetic valve or a valve taken from a pig heart.