Cardiovascular System Study Guide

• Exam 2 Study Guide covers Blood, The Heart and Cardiovascular Function, and Blood Vessels and Circulation

Blood Volume and Properties

• Blood volume in males is 5-6 liters, while in females it is 4-5 liters.
• Blood temperature is approximately 38°C (100.4°F).
• Blood pH ranges from 7.35 to 7.45, making it slightly alkaline.
• Blood is a liquid connective tissue, thicker than water and slightly sticky.

Functions of Blood

• Blood transports gases (O₂ and CO₂), nutrients, hormones, and waste products.
• Blood maintains pH, body temperature, and osmotic pressure.
• Blood provides clotting mechanisms and immune cells (white blood cells) along with proteins for protection.

Components of Blood

• Blood plasma is composed of 91.5% water and 8.5% solutes, primarily proteins like albumin and fibrinogen, that maintain osmotic balance.
• Red Blood Cells (RBCs/Erythrocytes) have a biconcave disc shape to maximize surface area for oxygen exchange.
• RBCs lack a nucleus and mitochondria and live for about 120 days.
• Males average 5.4 million RBCs/µL, while females average 4.8 million RBCs/µL.
• Hemoglobin in RBCs contains four polypeptide chains, each with a heme group that binds oxygen.
• White Blood Cells (WBCs/Leukocytes) are divided into granular (neutrophils, eosinophils, basophils) and agranular (lymphocytes, monocytes) types.
• Neutrophils are the most common WBCs and are key phagocytes.
• Lymphocytes include B cells (antibody production), T cells (cell-mediated immunity), and NK cells (tumor/infected cell destruction).
• Leukocytosis (increased WBC count) is a normal response to stress/infection, while leukopenia is harmful.
• Platelets (Thrombocytes) are small cell fragments produced by megakaryocyte fragmentation.
• Platelets are essential for hemostasis, aggregating to form plugs and initiate the clotting cascade, with a short lifespan of 5–9 days.

Additional Blood Concepts

• Polycythemia is an abnormally high percentage of RBCs, increasing blood viscosity and potentially impeding flow.
• Erythropoietin (EPO) stimulates RBC production (erythropoiesis).
• Thrombopoietin (TPO) stimulates platelet production.
• Blood groups are based on A and B antigens (and the Rh factor).
• Type A blood has antigen A and contains anti-B antibodies.
• Type B blood has antigen B and contains anti-A antibodies.
• Type AB blood has both A and B antigens, making it the universal recipient.
• Type O blood lacks both A and B antigens, making it the universal donor.

Heart Anatomy and Orientation

• The heart resides in the mediastinum, between the lungs, extending from the sternum to the vertebral column.
• The apex is the inferior, leftward-pointing tip of the heart resting on the diaphragm.
• The base is the superior surface of the heart.
• The atria (upper chambers) receive blood, while the ventricles (lower chambers) pump blood out.
• Interatrial and interventricular septa separate the left and right sides of the heart.
• Atrioventricular Valves: Tricuspid (right) and Mitral/Bicuspid (left) open during atrial contraction and close during ventricular systole.
• Semilunar Valves: Pulmonary (right) and Aortic (left) prevent backflow during ventricular relaxation.

Blood Flow and Circulatory Routes

• Systemic Circulation: Left atrium → Mitral valve → Left ventricle → Aortic valve → Aorta → Body tissues → Superior/Inferior vena cava → Right atrium, transporting oxygenated blood to the body.
• Pulmonary Circulation: Right atrium → Tricuspid valve → Right ventricle → Pulmonary valve → Pulmonary trunk → Pulmonary arteries → Lungs (oxygenation) → Pulmonary veins → Left atrium, transporting deoxygenated blood to the lungs and returns oxygenated blood.

Layers of the Heart Wall and Pericardium

• Epicardium: Outermost protective layer of the heart wall.
• Myocardium: Thick, muscular middle layer of the heart wall (95% cardiac muscle).
• Endocardium: Smooth, innermost lining of the heart wall that minimizes friction.
• Pericardium: Double-layered membrane consisting of the fibrous pericardium (outer, tough layer) and the serous pericardium (inner, with parietal and visceral layers).
• The pericardial cavity, located between the pericardial layers, contains lubricating fluid.

Cardiac Conduction and Regulation

• The conduction system starts at the Sinoatrial (SA) Node (the natural pacemaker in the right atrium), passes to the Atrioventricular (AV) Node, then through the Bundle of His, bundle branches, and finally through Purkinje fibers to stimulate ventricular contraction.
• The autonomic nervous system regulates heart function: Epinephrine increases heart rate and contractility, while acetylcholine decreases heart rate.
• Thyroid hormones further modulate heart rate and strength of contraction.
• Cardiac Output = Stroke Volume × Heart Rate.
• Regulating Factors of Cardiac Output: Preload (degree of stretch), contractility, and afterload (pressure to overcome).

Clinical Terms and Conditions

• Stenosis: Narrowing of a valve restricting blood flow (e.g., mitral stenosis).
• Mitral Valve Prolapse: Incomplete closure of the mitral valve.
• Congestive heart failure describes a loss of pumping efficiency.
• Left ventricle failure often leads to pulmonary edema; right ventricle failure to peripheral edema.
• Auscultation: Heart sounds (“Lubb” = closure of atrioventricular valves; “Dupp” = closure of semilunar valves) are used to assess valve function.
• A patent foramen ovale or Tetralogy of Fallot (“blue baby”) are examples of congenital defects that affect normal blood flow.

Types and Structure of Blood Vessels

• Arteries carry blood away from the heart and typically have thick, muscular walls (tunica media) for withstanding high pressure.
• Veins return blood to the heart and have thinner walls, larger lumens, and valves to prevent backflow.
• Capillaries are the smallest vessels where the exchange of gases, nutrients, and waste occurs.

Hemodynamics and Vascular Resistance

• Vascular Resistance Factors: Lumen size (vasoconstriction increases resistance), blood viscosity (thicker blood increases resistance), and vessel length (longer vessels create more friction).
• Blood Pressure Measurement: Typically measured at the brachial artery using a sphygmomanometer.
• Korotkoff Sounds: The first audible sound marks systolic pressure, and the disappearance of sound marks diastolic pressure.
• Shock: A state where the cardiovascular system fails to deliver sufficient oxygen and nutrients.
• Types of Shock: Hypovolemic (low blood volume), cardiogenic (poor heart pump), vascular (excessive vasodilation), and obstructive (blockage in circulation).

Major Vessels

• The ascending aorta gives off the coronary arteries.
• The arch of the aorta branches into the brachiocephalic trunk, common carotid, and subclavian arteries.
• The superior and inferior vena cava return deoxygenated blood to the right atrium.
• Specific veins (e.g., coronary sinus, jugular veins) drain defined regions of the body.