HEALTH ASSESSMENT NOTES

HEALTH ASSESSMENT HEART AND NECK VESSELS

Structure and Function of the Cardiovascular System

• The cardiovascular system is a highly complex system comprising the heart and a closed system of blood vessels.

Heart and Great Vessels

Heart

• The heart is a hollow, muscular, four-chambered organ, divided into left and right atria and left and right ventricles.
• It occupies the middle of the thoracic cavity between the lungs, in a space known as the mediastinum.
• Size: approximately the size of a clenched fist
    - Weight in women: approximately 255 g (9 oz)
    - Weight in men: approximately 310 g (10.9 oz)
• Position: extends vertically from the left second to the left fifth intercostal space (ICS) and horizontally from the right edge of the sternum to the left midclavicular line (MCL).
• Shape: anatomically resembles an inverted cone.
    - The upper portion (base) is located near the left second ICS.
    - The lower portion (apex) is near the left fifth ICS and the left MCL.
• Precordium: the anterior chest region that overlies the heart and great vessels.
• Circulation:
    - Right side of the heart pumps blood to the lungs for gas exchange (pulmonary circulation).
    - Left side of the heart pumps blood to all parts of the body (systemic circulation).
• Great Vessels: large veins and arteries leading directly to and away from the heart.
    - Superior vena cava: returns blood to the right atrium from the upper torso.
    - Inferior vena cava: returns blood to the right atrium from the lower torso.
    - Pulmonary artery: exits the right ventricle, bifurcates, and carries blood to the lungs.
    - Pulmonary veins: two from each lung return oxygenated blood to the left atrium.
    - Aorta: transports oxygenated blood from the left ventricle to the body.

Heart Chambers and Valves

• The heart consists of four chambers or cavities:
    - Two upper chambers: right and left atria.
    - Two lower chambers: right and left ventricles.
• Septum: partitions right and left sides of the heart.
• Left ventricle: thicker than the right because it has a greater workload.
• Atrioventricular (AV) valves: located at the entrance into the ventricles.
    - Tricuspid valve: composed of three cusps or flaps; located between the right atrium and right ventricle.
    - Bicuspid (mitral) valve: composed of two cusps; located between the left atrium and left ventricle.
• Chordae tendineae: collagen fibers that anchor the AV valve flaps to papillary muscles within the ventricles.
• Semilunar valves: located at the exit of each ventricle, beginning of the great vessels.
    - Pulmonic valve: located at the entrance of the pulmonary artery as it exits the right ventricle.
    - Aortic valve: located at the beginning of the ascending aorta as it exits the left ventricle.
• Valves open during ventricular contraction and close when the ventricles relax due to blood pressure.

Heart Covering and Walls

• Pericardium: tough, inextensible, loose-fitting fibrous sac surrounding the heart.
• Parietal pericardium: serous membrane lining; secretes pericardial fluid for friction-free movement.
• Epicardium: serous membrane covering the outer surface of the heart.
• Myocardium: thickest layer of the heart, made up of contractile cardiac muscle cells.
• Endocardium: thin layer of endothelial tissue forming the innermost layer, continuous with the endothelial lining of blood vessels.

Electrical Conduction of the Heart

• Cardiac muscle cells possess the unique ability to spontaneously generate and conduct electrical impulses.
• Cardiac cycle: generated and conducted impulses regulate the filling and emptying of cardiac chambers.
• Pathways:
    - Sinoatrial (SA) node: located on the posterior wall of the right atrium, generates impulses (60 to 100 per minute) that cause atrial contraction.
    - Conducting pathway:
      - Atria → AV node (located in the lower interatrial septum): slightly delays impulses and relays to AV bundle (Bundle of His).
      - Impulse travels down right and left bundle branches and Purkinje fibers in both ventricles, causing simultaneous contraction.
    - If SA node is nonfunctional, activity shifts to other areas like the Bundle of His (40 to 60 discharges per minute).

Electrical Activity

• Electrical impulses generated by the SA node can be detected on skin surface via electrocardiography (ECG or EKG):
    - Records depolarization and repolarization phases of cardiac muscle.
    - Phases of the ECG: P, Q, R, S, T.
    - P wave: atrial depolarization; impulse conduction through atria.
    - PR interval: time from start of atrial depolarization to start of ventricular depolarization.
    - QRS complex: ventricular depolarization; impulse conduction through ventricles.
    - ST segment: period between ventricular depolarization and beginning of repolarization.
    - T wave: ventricular repolarization; resting state of ventricles.
    - QT interval: total time for ventricular depolarization and repolarization; varies with heart rate.
    - U wave: may be present, follows T wave; represents final phase of ventricular repolarization.

Cardiac Cycle

• Refers to filling and emptying phases of the cardiac chambers.
• Consists of two phases:
    - Diastole (relaxation phase, filling): lasts about two-thirds of the cycle.
    - Systole (contraction phase, emptying): the remaining one-third of the cycle.

Diastole

• During ventricular diastole, AV valves are open; ventricles are relaxed. Pressure in atria exceeds ventricles, causing blood flow from atria to ventricles.
• Protodiastolic filling: early rapid filling phase.
• Followed by a period of slow filling, ending with atrial contraction (presystole or atrial kick), increasing left ventricular pressure.

Systole

• Filled ventricles create higher pressure than atria, resulting in closure of AV valves (S1 sound), marking beginning of systole. Closure prevents regurgitation into atria.

Heart Sounds

• Produced by valve closures; opening of valves is silent.
• Normal sounds: characterized as