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Chapter 11 The Cardiovascular System

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1 Chapter 11 The Cardiovascular System

2 The 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

3 The Heart Size of fist In thorax between lungs
Pointed apex toward left hip Size of fist

4 Heart Coverings & Wall Layers
Pericardium – double serous membrane Visceral - next to heart Parietal - outside layer Serous fluid fills space between the layers Three layers 1.Epicardium- Outside parietal pericardium Connective tissue 2.Myocardium- Middle Mostly cardiac muscle 3.Endocardium - Inner Endothelium

5 External Heart Anatomy
Figure 11.2a

6 The Heart: Chambers Right and left act as separate pumps Four chambers
2 Atria - Receiving - Right atrium - Left atrium 2 Ventricles - Discharging - Right ventricle - Left ventricle

7 The 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”)

8 Operation of Heart Valves

9 The Heart: Associated Great Vessels
Aorta - Leaves left ventricle Pulmonary arteries - Leave right ventricle Vena cava - Enters right atrium Pulmonary veins (four) - Enter left atrium

10 Coronary 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

11 The 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

12 The Heart: Cardiac Cycle
Cardiac cycle – events of one heart beat Terms: Systole = contraction Diastole = relaxation Atria contract simultaneously Atria relax, then ventricles contract

13 The 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

14 Cardiac Output Regulation

15 The 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

16 Regulation of Heart Rate
Decreased Heart Rate 1. Parasympathetic nervous system 2. High blood pressure or blood volume 3. Decreased venous return Increased Heart Rate 1. Sympathetic nervous system Crisis Low blood pressure 2. Hormones Epinephrine Thyroxine 3. Exercise 4. Decreased blood volume

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