Cardiovascular System: Heart & Blood Vessels Kirby - BHCC

An Overview of the Cardiovascular System Pulmonary circuit – blood to and from the lungs System circuit – blood to and from the rest of the body – Vessels carry the blood through the circuits Arteries carry blood away from the heart Veins carry blood to the heart Capillaries permit exchange

The Heart

Structure of Heart Pericardium – surrounds heart – protection & reduces friction Layers: – Epicardium- thin, transparent covering – Myocardium-cardiac muscle tissue – Endocardium- connective tissue surrounding chambers & valves Chambers: two atrium (top), two ventricles (bottom) Valves: – Two atrioventricular valves: tricuspid and bicuspid (mitral) – Two semilunar valves: pulmonary and aortic

Pulmonary Circuit Pathway: – Deoxygenated blood through the vena cava to the right atrium – Deoxygenated blood through the right atrioventricular valve to the right ventricle – Deoxygenated blood through the pulmonary semilunar valve to the pulmonary trunk and the lungs – Oxygenated blood through the pulmonary veins to the left atrium – Oxygenated blood through the left atrioventricular valve to the left ventricle

Systemic System Pathway: – Oxygenated blood through the aortic semilunar valve to the aorta – Oxygenated blood through branching arteries and arterioles to the tissues – Oxygenated blood through the arterioles to capillaries – Deoxygenated blood from capillaries into venules and veins – Ultimately to the vena cava and into the right atrium

Phases of the Cardiac Cycle

Conduction System 1. Sinoatrial (SA)node - pacemaker, located at the surface of the right atrium, impulse causes both atria to contract (rate BPM); a conduction pathway called Bachman's bundle runs from right to left atrium allowing for simultaneous atrial contractions. SA node sends impulse to the AV node via the anterior, medial and posterior internodal pathways. 2. Atrioventricular (AV) node - (rate BPM)last part of atria to be depolarized, sends impulse down the: 3. Bundle of His- distributes action potential over medial surfaces of the ventricles (rate BPM) runs to the top of the interventricular septum to the: 4. Right and left bundle branches - Actual contraction stimulated by conductive myofibers called Purkinje fibers that pass into the fibers of the myocardium of the ventricles.

EKG - Electrocardiogram A recording of the electrical events occurring during the cardiac cycle – The P wave accompanies the depolarization of the ventricles – The QRS complex appears as the ventricles depolarize – The T wave indicates ventricular repolarization

Heart Sounds Auscultation – listening to heart sound via stethoscope Four heart sounds – S 1 – “lubb” caused by the closing of the AV valves – S 2 – “dupp” caused by the closing of the semilunar valves – S 3 – a faint sound associated with blood flowing into the ventricles – S 4 – another faint sound associated with atrial contraction

Blood Vessels of the Heart

Blood Vessels – Arteries: carry oxygenated blood away from heart – Veins: carry deoxygenated blood back to the heart. – Capillaries: exchange of nutrients, waste, and defensive cells between vessel and tissue

Structure of Blood Vessels Composed of three layers (tunics) – Tunica intima – composed of simple squamous epithelium – Tunica media – sheets of smooth muscle Contraction – vasoconstriction Relaxation – vasodilation – Tunica externa – composed of connective tissue Lumen – Central blood-filled space of a vessel

Structure of Arteries, Veins & Capillaries

Arteries vs. Veins Arteries Transports blood away from heart Carry oxygenated blood (except pulmonary artery) Relatively narrow lumens More elastic/muscle tissue Transports blood under high pressure Do not have valves Veins Transports blood toward heart Carry deoxygenated blood (except pulmonary vein) Relatively wide lumens Less elastic/muscle tissue Transports blood under low pressure Has valves

Blood Pressure the force of the blood pushing against the walls of the arteries systolic pressure – blood pressure is at its highest when the heart beats, pumping the blood diastolic pressure – When the heart is at rest, between beats, your blood pressure falls

Top number (systolic) in mm Hg Bottom number (diastolic) in mm Hg Your category*What to do** Below 120andBelow 80 Normal blood pressure Maintain or adopt a healthy lifestyle or80-89Prehypertension Maintain or adopt a healthy lifestyle or90-99 Stage 1 hypertension Maintain or adopt a healthy lifestyle. If blood pressure goal isn't reached in about six months, talk to your doctor about taking one or more medications. 160 or moreor100 or more Stage 2 hypertension Maintain or adopt a healthy lifestyle. Talk to your doctor about taking more than one medication.