Chapter 11The Cardiovascular System

The Cardiovascular SystemThe Cardiovascular System

A closed system of the heart and blood vessels

-heart pumps blood

-blood vessels - circulate to all parts of body

Deliver oxygens & nutrients and to remove carbon dioxide & waste products

The HeartThe Heart In thorax between lungs

Pointed apex toward left hip

Size of fist

Heart Coverings & Wall LayersHeart Coverings & Wall LayersPericardium – double

serous membrane

Visceral - next to heart

Parietal - outside layer

Serous fluid fills space between the layers

Three layers1.Epicardium- Outside

parietal pericardium Connective tissue

2.Myocardium- Middle Mostly cardiac muscle

3.Endocardium - Inner Endothelium

External Heart AnatomyExternal Heart Anatomy

Figure 11.2a

The Heart: ChambersThe Heart: Chambers

Right and left act as separate pumps

Four chambers2 Atria - Receiving

- Right atrium

- Left atrium

2 Ventricles - Discharging

- Right ventricle

- Left ventricle

The Heart: ValvesThe Heart: Valves Allow blood to flow in only one direction Four valves

2 Atrioventricular valves – between atria & ventricles Bicuspid valve (left) Tricuspid valve (right)

2 Semilunar valves - between ventricle & artery Pulmonary semilunar valve Aortic semilunar valve

Held in place by chordae tendineae (“heart strings”)

Operation of Heart ValvesOperation of Heart Valves

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

Coronary CirculationCoronary Circulation

Blood in heart doesn’t nourish the heart

Heart’s nourishing circulatory system

- Coronary arteries

- Cardiac veins

- Blood empties into the right atrium via the coronary sinus

The Heart: Conduction SystemThe Heart: Conduction System Intrinsic conduction system (nodal system)

Heart muscle cells contract, without nerve impulses, in a regular, continuous way

- Sinoatrial node – Pacemaker initiates contraction

- Sequential stimulation occurs at other autorhythmic cells

- Atrioventricular node

- Atrioventricular bundle

- Bundle branches

- Purkinje fibers

The Heart: Cardiac CycleThe Heart: Cardiac Cycle Cardiac cycle – events of one heart beat

Terms: Systole = contraction Diastole = relaxation

Atria contract simultaneously

Atria relax, then ventricles contract

The Heart: Cardiac OutputThe Heart: Cardiac Output

Cardiac output (CO) Amount of blood pumped by

each side of the heart in one minute

CO = (heart rate [HR]) x (stroke volume [SV])

Stroke volume [SV] Volume of blood pumped by

each ventricle in one contraction

Cardiac Output RegulationCardiac Output Regulation

The Heart: Regulation of Heart RateThe Heart: Regulation of Heart Rate Stroke volume usually remains relatively

constant

- Starling’s law of the heart: the more that the cardiac muscle is stretched, the stronger the contraction

Changing heart rate is the most common way to change cardiac output

Regulation of Heart RateRegulation of Heart Rate

Increased Heart Rate1. Sympathetic nervous

system Crisis Low blood pressure

2. Hormones Epinephrine Thyroxine

3. Exercise

4. Decreased blood volume

Decreased Heart Rate

1. Parasympathetic nervous system

2. High blood pressure or blood volume

3. Decreased venous return