Cardiovascula system

THE CARDIOVASCULAR SYSTEM

ANATOMY OF THE HEART

1. The heart is located in the mediastinum; about two-thirds of its mass is to the left of the midline.

2. The heart is shaped like a cone lying on its side; its apex is the pointed, inferior part, whereas its base is the broad, superior part.

3. The pericardium is the membrane that surrounds and protects the heart; it consists of an outer fibrous layer and an inner serous pericardium, which is composed of a parietal and a visceral layer.

4. Between the parietal and visceral layers of the serous pericardium is the pericardial cavity, a potential space filled with a few milliliters of pericardial fluid that reduces friction between the two membranes.

5. Three layers make up the wall of the heart: epicardium (visceral layer of the serous pericardium), myocardium, and endocardium.

6. The epicardium consists of mesothelium and connective tissue, the myocardium is composed of cardiac muscle tissue, and the endocardium consists of endothelium and connective tissue.

7. The heart chambers include two superior chambers, the right and left atria, and two inferior chambers, the right and left ventricles.

8. External features of the heart include the auricles (flaps on each atrium that slightly increase their volume), the coronary sulcus between the atria and ventricles, and posterior surfaces of the heart, respectively.

9. The right atrium receives blood from the superior vena cava, inferior vena cava, and coronary sinus. It is separated from the left atrium by the interatrial septum, which contains the fossa ovalis. Blood exits the right atrium through the tricuspid valve.

10. The right ventricle receives blood from the right atrium. It is separated from the left ventricle by the interventricular septum and pumps blood through the pulmonary valve into the pulmonary trunk.

11. Oxygenated blood enters the left atrium from the pulmonary veins and exits through the bicuspid (mitral) valve.

12. The left ventricle pumps oxygenated blood through the aortic valve into the aorta.

13. The thickness of the myocardium of the four chambers varies according to the chamber’s function. The left ventricle, with the highest workload, has the thickest wall.

14. The fibrous skeleton of the heart is dense connective tissue that surrounds and supports the valves of the heart.

HEART VALVES AND CIRCULATION OF BLOOD

Normal Vs Prolapse Mitral Valve

1. Heart valves prevent backflow of blood within the heart. The atrioventricular (AV) valves, which lie between atria and ventricles, are the tricuspid valve on the right side of the heart and the bicuspid (mitral) valve on the left. The semilunar (SL) valves are the aortic valve, at the entrance to the aorta, and the pulmonary valve, at the entrance to the pulmonary trunk.

2. The left side of the heart is the pump for the systemic circulation, the circulation of blood throughout the body except for the air sacs of the lungs. The left ventricle ejects blood into the aorta, and blood then flows into systemic arteries, arterioles, capillaries, venules, and veins, which carry it back to the right atrium.

Mitral Valve Stenosis

3. The right side of the heart is the pump for pulmonary circulation, the circulation of blood through the lungs. The right ventricle ejects blood into the pulmonary trunk, and blood then flows into pulmonary arteries, pulmonary capillaries, and pulmonary veins, which carry it back to the left atrium.

4. The coronary circulation provides blood flow to the myocardium. The main arteries of the coronary circulation are left and right coronary arteries; the main veins are the cardiac vein and the coronary sinus.

CARDIAC MUSCLE TISSUE AND THE CARDIAC CONDUCTION SYSTEM

1. Cardiac muscle fibers usually contain a single centrally located nucleus. Compared to skeletal muscle fibers, cardiac muscle fibers have more and larger mitochondria, slightly smaller sarcoplasmic reticulum, and wider transverse tubules, which are located at Z discs.

2. Cardiac muscle fibers are connected via end-to-end intercalated discs. Desmosomes in the discs provide strength and gap junctions allow muscle action potentials to conduct from one muscle fibers to its neighbors.

3. Autorhytmic fibers form the conduction system, cardiac muscle fibers that spontaneously depolarize and generate action potentials.

4. Components of the conduction system are the sinoatrial (SA) node (pacemaker), atrioventricular (AV) node, atrioventricular (AV) bundle (bundle of His), bundle branches, and Purkinje fibers.

5. Phases of an action potential in a ventricular contractile fiber include rapid depolarization, a long plateau, and repolarization.

6. Cardiac muscle tissue has a long refractory period, which prevents tetanus.

The SA node, AV node, bundle of His and branch bundles

7. The record of electrical changes during each cardiac cycle is called an electrocardiogram (ECG). A normal ECG consists of a P wave (atrial depolarization), a ORS complex (onset of ventricular depolarization), and a T wave (ventricular repolarization).

8. The P-Q interval represents the conduction time from the beginning of atrial excitation to the beginning of ventricular excitation. The S-T segment represents the time when ventricular contractile fibers are fully depolarized.

EKG/ECG

THE CARDIAC CYCLE

1. A cardiac cycle consists of the systole (contraction) and diastole (relaxation) of both atria, plus the systole and diastole of both ventricles. With an average heartbeat of 75 beats/min, a complete cardiac cycle requires 0.8 seconds.

2. The phases of the cardiac cycle are (a) atrial systole, (b) ventricular systole, and (c) relaxation period.

3. S1, the first heart sound (lubb), is caused by blood turbulence associated with the closing of the atrioventricular valves. S2, the second sound (dupp), is caused by blood turbulence associated with the closing of semilunar valves.

CARDIAC CYCLE

SYSTOLE is the phase of contraction and DIASTOLE is the period of heart relaxation.

PHASES

1. Relaxation - the heart muscle repolarizes. Isovolumetric Relaxation - As the heart

relaxes, it expands. The volumes of the ventricles increase until ventricular pressure is lower than atrial pressure, the AV valves open and ventricular filling (by trickling) begins. The diastole lasts 0.4 seconds at rest.

2. Completion of Ventricular filling. The atria send the final 25% of blood by

contracting. Then 130 ml of blood (END

VENTRICULAR DIASTOLIC VOLUME) is present in each ventricle at rest.

3. Isovolumetric contraction - the ventricles begin to contract and the semilunar valves have not opened.

4. Ventricular ejection - 70 ml of the 130 E.D.V. is ejected, 70 ml is the stroke volume. The end systolic volume is 60 ml.

The red line is the EKG. The blue line is aortic

pressure. The green line shows heart sounds.

Blood Pressure and Sounds

The systolic pressure is the pressure read at the first sound heard in a stethoscope when the blood pressure cuff, which has closed off flow of the brachial artery, is released and the first spurt of blood comes through the artery below the cuff.

The diastolic pressure is read when the last sound is heard.

Blood Pressure and Sounds

The numbers, e.g., 120 systolic/80 diastolic, are normal for an adult.

During ventricular contraction, the atrio-ventricular valves make turbulence which makes the 'lubb' sound;

Semilunar valves snap shut and produce turbulence which makes a 'dupp' sound.

Elevation of B.P. above 140 systolic indicates arteriosclerosis or other problems which cause increased blood volume or heart rate.

The red line is the EKG. The blue line is aortic

pressure. The green line shows heart sounds.

CARDIAC OUTPUT

1. Cardiac output (CO) is the amount of blood ejected per minute by the left ventricle into the aorta (or by the right ventricle into the pulmonary trunk). It is calculated as follows: CO (mL/min) = stroke volume (SV) in mL/beat x heart rate (HR) in beats per minute.

2. Stroke volume (SV) is the amount of blood ejected by a ventricle during each systole.

3. Cardiac reserve is the difference between a person’s maximum cardiac output and his or her cardiac output at rest.

CARDIAC OUTPUT

At rest CO = stroke volume (70ml) X = heart rate (75/min) = 5250

ml/min STRESS (EXERCISE) CO = 140ml/beat (x) 150 beats/min = 21,000 ml/min The four fold rise in cardiac output is due to an increased

rate of ventricle filling and increased contractile force due to additional stretching of muscle fibers.

Cardiac reserve is that extra (above resting) capacity of cardiac output. The cardiac reserve of athletes may be seven or eight times the resting output.

4. Stroke volume is related to preload (stretch on the heart before it contracts), contractility (forcefulness of contraction), and afterload (pressure that must be exceeded before ventricular ejection can begin).

5. According to the Frank-Starling law of the heart, a greater preload (end-diastolic volume) stretching cardiac muscle fibers just before they contract increases their force of contraction until the stretching becomes excessive.

REGULATION OF STROKE VOLUME 1. Preload factors increase stretch and contractility.

Rapid filling and the stretching of the cardiac muscle of the ventricles during diastole by larger volumes of blood increases the force of the contracting muscle fibers. This is called the FRANK- STARLING LAW OF THE HEART.

When heart rate exceeds 160/min. heart efficiency declines. Why?

Remember the outputs of the right and left ventricles are the same normally.

REGULATION OF STROKE VOLUME2. Contractility The sympathetic accelerator neurotransmitters,

NE from the sympathetic cardiac accelerator nerves, and NE and EP from the adrenal medulla increase the rate of Ca++ movement through the slow Ca++ channels of the Pacemaker cells.

The parasympathetic Vagus nerve secretions of Ach have the opposite effect. Ep and NE bind to beta receptors to increase heart rate.

REGULATION OF STROKE VOLUME

3. Afterload factors - the pressures of blood in the pulmonary trunk and the aorta must be exceeded before blood can move out of the heart. Arteriosclerosis increases afterload pressures.

6. Nervous control of the cardiovascular system originates in the cardiovascular center in the medulla oblongata.

7. Sympathetic impulses increase heart rate and force of contraction; parasympathetic impulses decrease heart rate.

8. Heart rate is affected by hormones (epinephrine, norepinephrine, thyroid hormones), ions (Na+, K+, Ca2+), age, gender, physical fitness, and body temperature.

EXERCISE AND THE HEART

1. Sustained exercise increases oxygen demand on muscles.

2. Among the benefits of aerobic exercise are increased cardiac output, decreased blood pressure, weight control, and increased fibrinolytic activity.

Blood Supply to the Myocardium


The heart muscle requires a rich oxygen supply to meet its own metabolic needs. The coronary arteries (R & L) branch of the aorta just above the aortic valve, encircle the heart, and penetrate the myocardium. They supply the capillaries of the myocardium with blood.

Blood Supply to the Myocardium (cont.)The Right coronary artery (RCA) and its

branches perfuse the right atrium, right ventricle, inferior portion of the left ventricle, and posterior septal wall, the sinoatrial (SA) node, and the atrioventricular (AV) node.


The left coronary artery (LCA) has two major branches, the left anterior descending (LAD) and the circumflex arteries.

Blood Supply to the Myocardium (cont.)

The LAD supplies blood to the anterior wall of the left ventricle, the anterior ventricular septum, and the apex of the left ventricle.

Blood Supply to the Myocardium (cont.)The circumflex artery provide blood to the left atrium, the lateral and posterior surfaces of the left

ventricle, and occasionally the posterior interventricular

septum. In some clients, the circumflex artery, the

circumflex artery supplies the SA and AV nodes.


Unlike other arteries, 75% of the coronary artery blood flow occurs during diastole, when the heart is relaxed. For adequate blood flow through the coronary arteries, the diastolic blood flow increases with increased activity and increased stimulation of the sympathetic nervous system.

The coronary veins return blood from the myocardium to the right atrium. These veins usually run parallel to the arteries.

Heart Rate

Normal 60-100X/mnt. Dipengaruhi oleh exercise, ukuran tubuh, usia, sex,

hormone, temperature, bekanan darah, kecemasan dan stress, dan sakit.

Olah raga dapat meningkatkan HR. Seorang athlete memiliki HR yang lebih rendah, seorang yang lebih besar juga memiliki HR yang lebih rendah.

Bayi memiliki HR yang lebih cepat (120-160) Wanita memiliki HR lebih cepat dari laki-laki.

Cardiac Pressure

Tekanan ini dapat diambil dengan menggunakan sebuah kateter pulmonary artery pressure (Swan-Ganz).

Tekanan di dalam jantung dapat diukur dan ukuran ini untuk menentukan seperti preload, afterload, volume filling pressure, dan resistance.

Cardiac Pressure

Nilai Normal Pulmonary Artery: Systole (15-30mmHg); Diastole (3-

12mmHg) Aorta: Systole (96-140mmHg); Diastole (60-90mmHg) Left Atrium: 4-12mmHg Right Atrium: -1 – 8mmHg Left Ventricle: Systole (15-28mmHg); Diastole (4-

12mmHg) Right Ventricle: Systole (100-140mmHg); Diastole (0-

8mmHg)

Arterial Pressure

Arterial pressure adalah: Tekanan darah yang melawan dinding arteri.

Tipe dari arterial pressure adalah:Systolic pressureDiastolic pressurePulse pressureMean arterial pressure

Systolic & Diastolic Pressure

SP adalah tekanan maximum darah yang melalui pembuluh darah pada saat jantung kontraksi. Normal 100-140mmHg.

DP adalah tekanan darah melalui pembuluh darah pada saat jantung relaksasi. Normal 60-90mmHg.

BP sering mengekspresikan tekanan systolic/diastolic.

Pulse pressure

Pulse pressure adalah perbedaan tekanan antara sistolik dan diastolik 40-60mmHg, hal ini merefleksikan stroke volume dan elastisitas arteri.

Mean Arterial Presssure (MAP)

MAP adalah sama dengan 1/3 dari pulse pressure (PP) + diastolic blood pressure (DBP)

MAP 1/3 PP + DBP MAP digunakan untuk Hemodynamic

monitoring. Dua hal penentu dari BP adalah CO dan

peripheral vascular resistance (PVR) dengan vormula: BP = CO X PVR

Sirkulasi Darah sangat bergantung pada: CO PVR Elastisitas arteri Volume darah Blood viscosity (kekentalan darah)

Venous Pressure

VP adalah tekanan darah di dalam vena. Di dalam vena yang kecil tidak terdapat tekanan. Tekanan vena antara 12-15 mmHg.

In large veins leading to the heart (e.g., jugular vains), pulsations reflect back from right arterial contractions. Blood flows back to the heart via the venous system with assistance from:

vessel wall tone, The pumping action of skeletal muscles The negative thoracic pressure during inspiration.

DEVELOPMENT OF THE HEART

1. The heart develops from mesoderm. 2. The endocardial tubes develop into the

four-chambered heart and great vessels of the heart.

Health & Medicine

Cardiovascula system