UNIT 1: THE CARDIOVASCULAR SYSTEM (pt.1)

Epicardium, Myocardium, Endocardium

Anatomical Layers of the Heart:

Epicardium

Thin visceral layer of pericardium covering the heart exterior.

Myocardium

Thick muscular middle layer responsible for pumping action

Endocardium

 Inner endothelial lining continuous with blood vessel linings

pulmonary circulation

The right atrium and ventricle pump deoxygenated blood through ___

systemic circulation

the left atrium and ventricle pump oxygenated blood through ____

Tricuspid Valve and Mitral (Bicuspid) Valve

Atrioventricular (AV) Valves:

Tricuspid Valve

Located between the right atrium and right ventricle.

Mitral (Bicuspid) Valve

Located between the left atrium and left ventricle

Atrioventricular (AV) Valves

Prevent backflow into atria during ventricular systole; anchored by papillary muscles & chordae tendineae

Pulmonic Valve and Aortic Valve

Semilunar Valves:

Pulmonic Valve

Located between right ventricle and pulmonary artery

Aortic Valve

Located between left ventricle and aorta.

Semilunar Valves

Prevent regurgitation of blood back into ventricles during diastolic relaxation phase

Left Main Coronary Artery, Right Coronary Artery (RCA), Diastolic Perfusion

Myocardial Perfusion Pathways:

Left Main Coronary Artery

Branching into the Left Anterior Descending (LAD) and Circumflex arteries, supplying anterior and lateral left ventricle walls.

Left Anterior Descending (LAD) and Circumflex arteries

Left Main Coronary Artery branches into the ____, supplying anterior and lateral left ventricle walls.

Right Coronary Artery (RCA)

Supplies the right atrium, right ventricle, inferior wall of left ventricle, and conduction nodes (SA & AV).

Diastolic Perfusion

Coronary arterial flow occurs predominantly during ventricular diastole when aortic valves close

Sinoatrial (SA) Node, Atrioventricular (AV) Node, Purkinje System

Cardiac Conduction Pathways:

Sinoatrial (SA) Node

Primary pacemaker located at junction of superior vena cava and right atrium.

60–100 bpm.

Sinoatrial (SA) Node Intrinsic firing rate:

Atrioventricular (AV) Node

Delays electrical impulse allowing atrial kick & ventricular filling.

Atrioventricular (AV) Node

Secondary pacemaker

40–60 bpm

Atrioventricular (AV) Node firing rate

 Bundle of His, bundle branches, and Purkinje fibers

Purkinje System includes:

Purkinje System

Includes Bundle of His, bundle branches, and Purkinje fibers.

Purkinje System

Rapidly depolarizes ventricles

20–40 bpm

Purkinje System firing rate:

Cardiac Output (CO)

The amount of blood pumped by each ventricle in liters per minute.

Cardiac Output (CO)

 It reflects systemic tissue perfusion adequacy.

Stroke Volume

he amount of blood ejected from the ventricle with each heartbeat

60 to 70 m

average adult resting SV is

CO = HR x SV

CO =

4-8L

Resting Cardiac Output/Min:

Preload, Afterload, Contractility, Heart Rate Control

Determinants of Stroke Volume

Preload

Degree of myocardial stretch at the end of diastole.

Preload

 Direct relation to end-diastolic volume as described by Frank-Starling Law.

Frank-Starling Law

Preload is a direct relation to end-diastolic volume as described by __

Afterload

Resistance to ejection of blood from the ventricle

Afterload

Determined by systemic vascular resistance (SVR) and aortic pressure.

Contractility

Inherent force of myocardial contraction independent of preload, enhanced by sympathetic stimulation and positive inotropes

Heart Rate Control

Modulated by autonomic nervous system

sympathetic stimulation

___ increases HR

parasympathetic vagal tone

____ decreases HR

Arteries & Arterioles

Thick elastic walls & smooth muscle layers

Arteries & Arterioles

Resistance vessels; regulate blood flow & systemic blood pressure

High pressure, high resistance system

Arteries & Arterioles Hemodynamic Profile

Capillaries

Single layer of endothelial cells

Capillaries

Microcirculation exchange of nutrients, oxygen, & metabolic wastes

Low pressure, slow velocity flow

Capillaries Hemodynamic Profile

Veins & Venules

Thin-walled, high compliance with valves

Veins & Venules

Capacitance vessels; store ~64% of circulating total blood volume

Low pressure, high volume capacity

Veins & Venules Hemodynamic Profile