1. The Circulatory System
Lecture # 3
The Heart
(Part 1)
(Chapter 19)
Overview of Cardiovascular System
Gross Anatomy of the Heart
Cardiac Conduction System and Cardiac Muscle
Electrical and Contractile Activity of Heart

2. The Circulatory System
-Blood
It is the liquid medium in which these substance travel.
The Circulatory System
-Cardiovascular System
Blood vessels
They ensure the proper routing of blood to its destination.
It transports substances from place to place in the body.
Heart
It is the pump that keeps the blood flowing.

3. Cardiovascular System
Systemic Circuit
It supplies blood to every organ of the body, including the heart itself.
Cardiovascular System
Pulmonary Circuit
It carries blood to the lungs for gas exchange and returns it to the heart.
Pulmonary
Arteries (2)
Pulmonary
Veins (4)
Blood Vessels
Vena cava
Aorta
Arteries
They carry blood away from the heart.
Veins
They carry blood back to (toward) the heart.
Capillaries
They connect the arteries with the veins.

4. Pulmonary Circuit Systemic Circuit
Gas exchange
Pulmonary Circuit
It carries blood to the lungs for gas exchange and returns it to the heart.
O2 rich blood through VEINS
O2 poor blood through ARTERIES
Systemic Circuit
It supplies blood to every organ of the body, including the heart itself.
O2 rich blood through ARTERIES
O2 poor blood through VEINS

5. Lung Tissue CO2 O2 CO2 O2 Arteriole Venule Capillary Gas Exchange
Pulmonary arteries (2)
Pulmonary veins (4)
Pulmonary
Circuit
O2 rich,
CO2 poor blood
Tissue
CO2
Wastes O2
Nutrients
Systemic
Circuit
Venae cavae
Aorta
Capillary
Arteriole
Venule
O2 poor,
CO2 rich blood

6. Position, Size, and Shape of the Heart
The 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.

7. Functions of the Pericardium:
The pericardium is a double-walled sac (pericardial sac) that encloses the heart.
Parietal pericardium
Superficial fibrous layer of connective tissue
Pericardial cavity
Visceral pericardium or epicardium
Deep, thin serous layer.
It is the space inside the pericardial sac filled with 5-30 mL of pericardial fluid.
Functions of the Pericardium:
1- It allows the heart to beat without friction.
2- It provides room to expand, yet resists excessive expansion.
Pericarditis: It is the inflammation of the membranes. It produces a painful friction rub with each heartbeat.

8. The Heart Wall Epicardium (visceral pericardium) Myocardium
Endocardium
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.
Myocardium
Endocardium
It 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.
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.

9. (cardiac muscle tissue)
The Heart Wall
Fibrous tissue
Parietal pericardium
Areolar tissue
Mesothelium
Pericardial cavity
EPICARDIUM
Mesothelium
Visceral pericardium
Areolar tissue
MYOCARDIUM
(cardiac muscle tissue)
ENDOCARDIUM
Endothelium
Areolar tissue
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.

10. The Heart Poor oxygen blood Gas exchange Superior vena cava
Pulmonary arteries
Inferior vena cava
Coronary sinus
Reach oxygen blood
Pulmonary veins
RIGHT ATRIUM
LEFT ATRIUM
To the rest of the body
Aorta
TISSUES
RIGHT VENTRICLE
LEFT VENTRICLE

11. Superior vena cava
It drains oxygen-poor blood from tissues and organs superior to the diaphragm to the right atrium.
Pulmonary trunk
Aorta
It carries oxygen-poor blood from the right ventricle to the lungs.
It carries oxygen-rich blood from the left ventricle to the whole body.
Pulmonary veins (4)
Inferior vena cava
It drains oxygen-poor blood from tissues and organs inferior to the diaphragm to the right atrium.
They carry oxygen-rich blood from the lungs to the left atrium.
Coronary sinus (no shown)
It drains oxygen-poor blood from the heart tissues to the right atrium.

12. The Chambers of the Heart
Left auricle
Coronary or atrioventricular sulcus
Anterior interventricular sulcus
Pectinate muscles
Left atrium
Anterior view
Right atrium
Interatrial septum
Right ventricle
Left ventricle
Trabeculae carneae
Coronary or atrioventricular sulcus
Interventricular septum
Posterior interventricular sulcus
Posterior view

13. Blood Flow Through Heart Chambers
Pulmonary arteries
Aorta
Pulmonary trunk
Superior vena cava
Left atrium
It receives blood returning from the lungs through the pulmonary veins (4).
Pulmonary veins
Pulmonary veins
Right atrium
It receives O2 poor blood returning to the heart through the superior and inferior vena cava and the coronary sinus (no shown).
Left ventricle
It pumps O2 rich blood through the aorta artery to every organ of the body.
Inferior vena cava
It pumps O2 poor blood to the lungs through the pulmonary arteries.
Right ventricle

16. The valves ensure a one-way flow, by preventing back flow of the blood.
Left AV
(bicuspid or mitral) valve
Right AV
(tricuspid) valve
Aortic semilunar valve
It prevents back flow of blood from the aorta to the LV
Pulmonary semilunar valve
Left AV
(bicuspid) valve
It prevents back flow of blood from the pulmonary trunk to the RV
Aortic semilunar valve
It prevents back flow of blood from the LV to the LA
Right AV
(tricuspid) valve
Chordae tendineae
Pulmonary semilunar valve
Papillary muscles
It prevents back flow of blood from the RV to the RA

17. Blood Flow Through Heart Chambers

18. Endoscopic photo of the aortic valve, viewed from above.
Papillary muscles and tendinous cords seen from within the right ventricle.

19. The Coronary Circulation
If you heart lasts 80 years and beats an average of 75 times a minute, it will be beat more than times and pump more than liters of blood.
A polymer cast of the coronary circulation.
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.
The coronary circulation supplies the myocardium with about 250 mL of blood per minute.

20. The Coronary Circulation
Left coronary artery (LCA)
Right coronary artery (RCA)
Circumflex branch of LCA
It supplies right atrium and sinoatrial node (pacemaker).
Anterior interventricular branch of LCA
It supplies left atrium and posterior wall of left ventricle.
Right marginal branch of RCA
Posterior interventricular branch of RCA
Great cardiac vein
It supplies lateral aspect of right atrium and ventricle.
It supplies both ventricles and anterior two-thirds of the inter-ventricular septum.
Left marginal branch of LCA
It supplies posterior walls of ventricles.
It supplies posterior wall of left ventricle.
Anterior view

21. The Coronary Circulation
Coronary sinus
It collects blood and empties into right atrium.
Left marginal branch of LCA
Left marginal vein
Right coronary artery (RCA)
Posterior interventricular vein or middle cardiac vein
Right marginal branch of RCA
Posterior interventricular branch of RCA
Posterior view

22. The Circulatory System
Lecture # 3
The Heart
(Part 2)
(Chapter 19)
Overview of Cardiovascular System
Gross Anatomy of the Heart
Cardiac Conduction System and Cardiac Muscle
Electrical and Contractile Activity of Heart

23. Conduction System
It is composed of an internal pacemaker and nervelike conduction pathways through myocardium that generate and conduct rhythmic electrical signals.
Sinoatrial node
(pacemaker)
Atrioventricular
bundle
It initiates each heartbeat and determines heart rate.
It is a pathway by which the signals leave the AV node.
Atrioventricular
node
It acts as insulator to prevent currents from getting to the ventricles from any other route, and delays the electrical excitation.
Left bundle branch
Right bundle branch
Purkinje fibers
They distribute the electrical excitation to the cardiocytes of the ventricles.
Purkinje
fibers

24. Cardiac Conduction System

26. Gated sodium channels are open Gated Potassium channels are open
DEPOLARIZATION
Gated sodium channels are open
-70 mV
Outside positive
-65 mV
Outside positive
-65 mV
Depolarization
Resting potential
HYPERPOLARIZATION
Gated Potassium channels are open
-70 mV
Outside positive
Inside positive
-80 mV
Outside positive
Inside negative
-80 mV
Hyperpolarization

27. -40 mV
Resting Potential
Fast Ca+ and Na+ inflow
Action Potential
Pacemaker Potential
-60 mV
Fast K+ outflow
-60 mV
Slow Na+ inflow
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.
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

28. The Electrocardiogram+1
Millivolts R
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.
QRS complex
Depolarization of ventricles
Depolarization of atria T P
Repolarization of ventricles Q S
PQ segment
ST segment
It represents the time during which the ventricles contract and eject blood
100 msec
Atrial systole
Ventricular systole

29. QRS complex +1 Millivolts –1 R PQ segment ST segment T wave P wave PR–1
Millivolts
0.8 second R
QRS complex PQ
segment ST
segment
T wave
P wave PR
interval Q S QT
interval
QRS interval

30. 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).

31. The Cardiac Rhythm Sinus rhythm:
It is the normal heartbeat triggered by the SA node.
At rest, the sinus rhythm is about 70 to 80 times per minute (rates from 60 to 100 bpm).
Tachycardia:
It is a persistent, resting adult heart rate above 100 bpm.
Bradycardia:
It is a persistent, resting adult heart rate below 60 bpm.
Extra-systoles:
Extra heart beats produced in any region of spontaneous firing other than the SA node.
If the SA node is damaged, other part of the myocardium may take over the governance of the heart rhythm.
Ectopic focus:
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.
Nodal rhythm:
If neither the SA nor AV nodes is functioning, an artificial pacemaker is required.
Arrhythmia:
It is any abnormal cardiac rhythm.
Heart block:
It is the failure of any part of the of the cardiac conducting system to transmit signals.

32. Ventricular fibrillation Heart block
0.8 sec
0.5 sec
75 bpm
Sinus Rhythm (normal)
120 bpm
Tachycardia
1.4sec
1.4sec
0.5 sec
0.3 sec
46 bpm
Bradycardia
Arrhythmia
Extrasystole
Nodal Rhythm
Ventricular fibrillation
Heart block