The Circulatory System

Part 1Lecture # 3

Overview of Cardiovascular System

Gross Anatomy of the Heart

Cardiac Conduction System and Cardiac Muscle

Electrical and Contractile Activity of Heart

The Heart

(Chapter 19)

The Circulatory

System

Heart

Blood vessels

-Blood

It transports substances from place to place in the body.

It is the liquid medium in which these substance travel.

They ensure the proper routing of blood to its destination.

It is the pump that keeps the blood flowing.

-Cardiovascular System

Arteries

Veins

Capillaries

They carry blood away from the heart.

They carry blood back to (toward) the heart.

They connect the arteries with the veins.

Blood Vessels

Veins (4)

Pulmonary Arteries (2)

Cardiovascular System Pulmonary Circuit

Systemic Circuit

It carries blood to the lungs for gas exchange and returns it to the heart.

It supplies blood to every organ of the body, including the heart itself.

Vena cava Aorta

Pulmonary

Gas exchange

Systemic CircuitIt supplies blood to every organ of the body, including the heart itself.

O2 rich blood through

ARTERIESO2 poor blood through VEINS

O2 poor blood through

ARTERIES

O2 rich blood through VEINS

Pulmonary CircuitIt carries blood to the lungs for gas exchange and returns it to the heart.

Tissue

Arteriole Venule

Capillary

Lung

CO2

WastesO2

Nutrients

Venule Arteriole

O2 rich,CO2 poor

blood

O2 poor,CO2 rich

blood

Gas Exchange

Capillary

CO2 O2

Venae cavae

Aorta

Pulmonary arteries (2)

Pulmonary veins (4)Pulmonary

Circuit

SystemicCircuit

Position, Size, and Shape of the HeartThe heart is located in the thoracic cavity, in the mediastinum, between the lungs.

The base is the wide, superior portion of the heart, the great blood vessels attach here.

The apex is the inferior end, tilts to the left.

The heart is enclosed in the pericardium.

The PericardiumThe pericardium is a double-walled sac (pericardial sac) that encloses the heart.

Parietal pericardium Superficial fibrous layer of connective tissue Deep, thin serous layer.

Visceral pericardium or epicardium

Pericardial cavity It is the space inside the pericardial sac filled with 5-30 mL of pericardial fluid.

1- It allows the heart to beat without friction.2- It provides room to expand, yet resists excessive expansion.

Functions of the Pericardium:

Pericarditis: It is the inflammation of the membranes. It produces a painful friction rub with each heartbeat.

The Heart Wall

Epicardium (visceral pericardium)It is a serous membrane covering heart. Also includes a thick layer of adipose tissue in some places. The coronary blood vessels travel through this layer.

Epicardium (visceral pericardium)

MyocardiumIt is a layer of cardiac muscle proportional to work load.It also contains a framework of collagen and elastic fibers, which:

- Provides structural support and attachment for cardiac muscle and anchor for valve tissue.- Is an electrical insulation between atria and ventricles, so the atria can not stimulate the ventricles directly.

Myocardium

Endocardium

Endocardium

It is the smooth inner lining of heart and blood vessels. It covers the valve surfaces and is continuous with the endothelium of blood vessels.

Endocarditis is the inflammation of the inside lining of the heart chambers and heart valves (endocardium). Most people who develop endocarditis have heart disease of the valves.

The Heart WallMesothelium

Fibrous tissue

Areolar tissue

Pericardial cavity

Parietal pericardium

EPICARDIUM

MYOCARDIUM

(cardiac muscle tissue)ENDOCARDIUM

Mesothelium

Areolar tissueVisceral pericardium

EndotheliumAreolar tissue

RIGHT ATRIUM LEFT

ATRIUM

RIGHT VENTRICLE

LEFT VENTRICLE

Aorta

To the rest of the body

Poor oxygen blood

Reach oxygen blood

Gas exchangeSuperior

vena cava

Inferior vena cava

Coronary sinus

Pulmonary arteries

Pulmonary veins

The Heart

TISSUES

It drains oxygen-poor blood from tissues and organs superior to the diaphragm to the right atrium.

It drains oxygen-poor blood from tissues and organs inferior to the diaphragm to the right atrium.

Coronary sinus (no shown)It drains oxygen-poor blood from the heart tissues to the right atrium.

It carries oxygen-poor blood from the right ventricle to the lungs.

Superior vena cava

Pulmonary trunk

They carry oxygen-rich blood from the lungs to the left atrium.

Aorta It carries oxygen-rich blood from the left ventricle to the whole body.

Pulmonary veins (4)Inferior vena cava

Right atrium

Right ventricle

Left atrium

Left ventricle

Anterior view

Posterior view

Left auricleCoronary or atrioventricular

sulcus

Coronary or atrioventricular sulcus

Anterior interventricular

sulcus

Posterior interventricular

sulcusInterventricular

septum

Interatrial septum

Trabeculae carneae

Pectinate muscles

The Chambers of the Heart

Right atrium It receives O2 poor blood returning to the heart through the superior and inferior vena cava and the coronary sinus (no shown).

Right ventricle It pumps O2 poor blood to the lungs through the pulmonary arteries.

Superior vena cava

Inferior vena cava

Left atrium It receives blood returning from the lungs through the pulmonary veins (4).

Pulmonary veins

Left ventricleIt pumps O2 rich blood through the aorta artery to every organ of the body.

Pulmonary trunk

Aorta

Pulmonary arteries

Pulmonary veins

Blood Flow Through Heart Chambers

The Valves

Left AV(bicuspid)

valve

Left AV(bicuspid or

mitral) valve

Right AV(tricuspid)

valve

It prevents back flow of blood from the LV to the LA

Pulmonary semilunar

valve

Right AV(tricuspid)

valveIt prevents back

flow of blood from the RV to the RA

It prevents back flow of blood from

the pulmonary trunk to the RV

Pulmonary semilunar

valve

Aortic semilunar valve

It prevents back flow of blood from the aorta to the LV

Aortic semilunar

valveChordae tendineae

Papillary muscles

The valves ensure a one-way flow, by preventing back flow of the blood.

Blood Flow Through Heart Chambers

Endoscopic photo of the aortic valve, viewed from above.

Papillary muscles and tendinous cords seen from within the right ventricle.

The Coronary CirculationIf you heart lasts 80 years and beats an average of 75 times a minute, it will be beat more than 3 000 000 000 times and pump more than 200 000 000 liters of blood.

The heart is a remarkable hardworking organ and needs an abundant supply of O2.

The blood vessels of the heart wall constitute the coronary circulation.

A polymer cast of the coronary circulation.

The coronary circulation supplies the myocardium with about 250 mL of blood per minute.

Left coronary artery (LCA) Right coronary

artery (RCA) Circumflex branch of LCAIt supplies left atrium and posterior wall of left ventricle.

It supplies both ventricles and anterior two-thirds of the inter-ventricular septum.

It supplies right atrium and sinoatrial node (pacemaker).

Anterior view

Right marginal branch of RCAIt supplies lateral aspect of right atrium and ventricle.

It supplies posterior walls of ventricles.

The Coronary Circulation

Left marginal branch of LCAIt supplies posterior wall of left ventricle.

Anterior interventricular branch of LCA

Great cardiac vein

Posterior interventricular branch of RCA

Posterior view

Right coronary artery (RCA)

Posterior interventricular branch of RCA

Right marginal branch of RCA

Left marginal branch of LCA

Posterior interventricular vein or middle cardiac vein

Left marginal vein

The Coronary Circulation

Coronary sinusIt collects blood and empties into right atrium.

The Circulatory System

Part 2Lecture # 3

Overview of Cardiovascular System

Gross Anatomy of the Heart

Cardiac Conduction System and Cardiac Muscle

Electrical and Contractile Activity of Heart

The Heart

(Chapter 19)

Conduction SystemIt is composed of an internal pacemaker and nervelike conduction pathways through myocardium that generate and conduct rhythmic electrical signals.

It initiates each heartbeat and determines heart rate.

Sinoatrial node(pacemaker)

Atrioventricularnode

It acts as insulator to prevent currents from getting to the ventricles from any other route, and delays the electrical excitation.

Atrioventricularbundle

It is a pathway by which the signals leave the AV node.

Left bundle branchRight bundle branchPurkinje fibers

Purkinjefibers

They distribute the electrical excitation to the cardiocytes of the ventricles.

Cardiac Conduction System

-70 mV -70 mVOutside positive

Outside positive

Inside positive

-70 mV -70 mVOutside positive

Outside positive -65 mV

-80 mV

DEPOLARIZATION

HYPERPOLARIZATION

Resting potential

Resting potential

-65 mVOutside positive

Depolarization

-80 mVOutside positive

Inside negative

Hyperpolarization

Gated sodium channels are open

Gated Potassium channels are open

-40 mV

Action PotentialPacemaker

Potential -60 mV

Resting Potential

-60 mV

Action Potentials: They are changes in the transmembrane potential that, once initiated, affect an entire excitable membrane

Each depolarization of the SA node sets off one heartbeat. At rest, fires every 0.8 seconds or 75 bpm

Slow Na+ inflow

Fast Ca+ and Na+ inflow

Fast K+ outflow

SA node does not have a stable resting membrane potential. It starts at -60 mV.

It drifts upward because of a slow inflow of Na+.

When it reaches a threshold of -40 mV, voltage-gated Ca2+ and Na+ channels open and a faster depolarization occurs peaking at 0 mV.The K+ channels then open and K+ leaves the cell causing repolarization.

+1

0

Mill

ivol

ts

P

Q

R

S

TDepolarization of

atria

QRS complexDepolarization of

ventricles

Repolarization of ventricles

PQ segment

Atrial systole

100 msec

ST segment

Ventricular systole

It represents the time during which the ventricles contract and eject blood

The Electrocardiogram

An ECG is a composite of all action potentials of nodal and myocardial cells, detected, amplified and recorded by electrodes on arms, legs and chest.

+1

0

–1

Mill

ivol

ts

0.8 second

T wave

QRS interval

R

S

P wave

PRinterval

QTinterval

PQsegment

STsegment

Q

QRS complex

1- Atrial depolarization begins.

2- Atrial depolarization complete (atria contracted).

3- Ventricles begin to depolarize at apex; atria repolarize (atria relaxed).

4- Ventricular depolarization complete (ventricles contracted).

5- Ventricular repolarization begins at apex (ventricles begin relaxation).

6- Ventricular repolarization complete (ventricles relaxed).

Extra heart beats produced in any region of spontaneous firing other than the SA node.

It is the failure of any part of the of the cardiac conducting system to transmit signals.

The Cardiac RhythmIt is the normal heartbeat triggered by the SA node.Sinus rhythm:

At rest, the sinus rhythm is about 70 to 80 times per minute (rates from 60 to 100 bpm).

Any region of spontaneous firing other than the SA node. The most common ectopic focus is the AV node, which produces a nodal rhythm. It is the cardiac rhythm produced by the AV node. It is a slower heartbeat of 40 to 50 bpm. If neither the SA nor AV nodes is functioning, an artificial pacemaker is required.Arrhythmia: It is any abnormal cardiac rhythm.

Heart block:

Extra-systoles:

Ectopic focus:

Tachycardia: It is a persistent, resting adult heart rate above 100 bpm.

Bradycardia: It is a persistent, resting adult heart rate below 60 bpm.

If the SA node is damaged, other part of the myocardium may take over the governance of the heart rhythm.

Nodal rhythm:

0.8 sec

75 bpm

0.5 sec

120 bpm Tachycardia

1.4sec

46 bpm Bradycardia

1.4sec 0.5 sec 0.3 sec 1.4sec

Arrhythmia

Nodal Rhythm Extrasystole

Heart block Ventricular fibrillation

Sinus Rhythm (normal)