🫁Honors Anatomy and Physiology Unit 10 – Cardiovascular System

Key Components and Structure

• Consists of the heart, blood vessels (arteries, veins, and capillaries), and blood
• Heart pumps blood through the circulatory system delivering oxygen and nutrients to tissues and removing waste products
• Arteries carry oxygenated blood away from the heart to the body's tissues (aorta)
• Veins return deoxygenated blood from the tissues back to the heart (vena cava)
  • Contain valves to prevent backflow of blood
• Capillaries are the smallest blood vessels where exchange of oxygen, nutrients, and waste products occurs between blood and tissues
• Cardiovascular system is a closed system meaning blood never leaves the network of blood vessels
• Pulmonary circulation carries deoxygenated blood from the heart to the lungs for oxygenation and returns oxygenated blood back to the heart
• Systemic circulation carries oxygenated blood from the heart to the body's tissues and returns deoxygenated blood back to the heart

Blood Composition and Function

• Blood is a connective tissue composed of plasma (liquid portion) and formed elements (red blood cells, white blood cells, and platelets)
• Plasma makes up about 55% of blood volume and consists of water, proteins, electrolytes, nutrients, and waste products
• Red blood cells (erythrocytes) contain hemoglobin, a protein that binds to oxygen, enabling oxygen transport throughout the body
  • Lack of red blood cells or hemoglobin leads to anemia
• White blood cells (leukocytes) are part of the immune system and defend the body against infections and foreign substances
  • Types include neutrophils, lymphocytes, monocytes, eosinophils, and basophils
• Platelets (thrombocytes) are essential for blood clotting to prevent excessive bleeding
• Blood helps maintain homeostasis by regulating body temperature, pH, and water balance
• Transports hormones and other signaling molecules throughout the body

The Heart: Anatomy and Function

• The heart is a muscular organ about the size of a fist located in the chest cavity
• Divided into four chambers: right atrium, right ventricle, left atrium, and left ventricle
• Atria are the upper receiving chambers that collect blood returning to the heart
• Ventricles are the lower pumping chambers that eject blood out of the heart
• Septum is a muscular wall that separates the left and right sides of the heart
• Heart valves (tricuspid, pulmonary, mitral, and aortic) ensure unidirectional blood flow through the heart
  • Valves open and close in response to pressure changes during the cardiac cycle
• Coronary arteries supply the heart muscle (myocardium) with oxygenated blood
• Pacemaker cells in the sinoatrial (SA) node spontaneously generate electrical impulses that initiate heart contractions
• Atrioventricular (AV) node delays the electrical signal before it reaches the ventricles allowing time for ventricular filling

Blood Vessels and Circulation

• Arteries are thick-walled, elastic vessels that carry blood away from the heart under high pressure
  • Smooth muscle in the arterial walls helps regulate blood pressure and flow
• Arterioles are small arteries that deliver blood to capillary beds
• Capillaries are thin-walled vessels that allow exchange of substances between blood and tissues
  • Capillary walls consist of a single layer of endothelial cells
• Venules are small veins that collect blood from capillary beds
• Veins are thin-walled vessels that carry blood back to the heart under low pressure
  • Contain valves to prevent backflow of blood
• Pulmonary circulation carries deoxygenated blood from the right ventricle to the lungs via pulmonary arteries and returns oxygenated blood to the left atrium via pulmonary veins
• Systemic circulation carries oxygenated blood from the left ventricle to the body's tissues via the aorta and returns deoxygenated blood to the right atrium via the vena cava
• Coronary circulation supplies the heart muscle with oxygenated blood via coronary arteries

Cardiac Cycle and Heart Rhythms

• The cardiac cycle is the sequence of events that occur during one complete heartbeat
• Consists of systole (contraction) and diastole (relaxation) of the atria and ventricles
• Atrial systole: atria contract, pumping blood into the ventricles
• Ventricular systole: ventricles contract, ejecting blood into the pulmonary artery and aorta
• Atrial diastole: atria relax and fill with blood from the veins
• Ventricular diastole: ventricles relax and fill with blood from the atria
• Heart sounds ("lub-dub") are caused by the closing of heart valves during the cardiac cycle
• Sinoatrial (SA) node generates electrical impulses that set the pace of heart contractions (natural pacemaker)
• Atrioventricular (AV) node delays the electrical signal before it reaches the ventricles
• Bundle of His and Purkinje fibers rapidly conduct the electrical signal throughout the ventricles
• Electrocardiogram (ECG or EKG) records the electrical activity of the heart
  • P wave represents atrial depolarization, QRS complex represents ventricular depolarization, and T wave represents ventricular repolarization

Cardiovascular Health and Diseases

• Atherosclerosis is the buildup of plaque in the arterial walls, narrowing the lumen and reducing blood flow
  • Risk factors include high blood pressure, high cholesterol, smoking, obesity, and diabetes
• Coronary artery disease (CAD) occurs when the coronary arteries become narrowed or blocked by plaque, reducing blood supply to the heart muscle
  • Can lead to angina (chest pain) or myocardial infarction (heart attack)
• Heart failure occurs when the heart is unable to pump enough blood to meet the body's needs
  • Can be caused by CAD, hypertension, valvular disorders, or cardiomyopathy
• Arrhythmias are abnormal heart rhythms caused by problems with the heart's electrical conduction system
  • Examples include tachycardia (fast heartbeat), bradycardia (slow heartbeat), and atrial fibrillation (irregular heartbeat)
• Valvular disorders occur when heart valves do not open or close properly, disrupting blood flow
  • Can be caused by congenital defects, infections, or degenerative changes
• Hypertension (high blood pressure) puts extra strain on the heart and blood vessels, increasing the risk of CAD, heart failure, and stroke
• Congenital heart defects are structural abnormalities of the heart present at birth
  • Examples include septal defects, patent ductus arteriosus, and tetralogy of Fallot

Diagnostic Tests and Procedures

• Electrocardiogram (ECG or EKG) records the electrical activity of the heart, helping diagnose arrhythmias, CAD, and heart attacks
• Echocardiogram uses ultrasound to create images of the heart, assessing its structure and function
  • Can detect valvular disorders, congenital defects, and abnormalities in heart wall motion
• Stress test evaluates the heart's response to physical exertion, helping diagnose CAD and determine exercise capacity
  • Can be done with ECG monitoring, echocardiography, or nuclear imaging
• Cardiac catheterization involves inserting a catheter into the heart through a blood vessel to measure pressures, assess valve function, and visualize coronary arteries
  • Coronary angiography uses contrast dye to visualize the coronary arteries and detect blockages
• Computed tomography (CT) and magnetic resonance imaging (MRI) provide detailed images of the heart and blood vessels
  • Can detect structural abnormalities, plaque buildup, and scar tissue
• Blood tests can measure levels of cardiac enzymes (troponin) released during a heart attack, helping diagnose and monitor the extent of damage

Cutting-Edge Research and Treatments

• Stem cell therapy involves using stem cells to regenerate damaged heart tissue and improve cardiac function
  • Promising results in animal studies and early human trials
• Gene therapy aims to correct genetic defects or introduce therapeutic genes to treat cardiovascular diseases
  • Targets include familial hypercholesterolemia and congestive heart failure
• Tissue engineering focuses on creating functional heart valves and blood vessels using a patient's own cells
  • Could reduce the need for donor organs and minimize rejection risk
• Percutaneous coronary intervention (PCI) uses a catheter to place a stent in a blocked coronary artery, restoring blood flow
  • Less invasive alternative to coronary artery bypass grafting (CABG) surgery
• Transcatheter aortic valve replacement (TAVR) is a minimally invasive procedure to replace a damaged aortic valve
  • Suitable for patients who are high-risk for traditional open-heart surgery
• Left ventricular assist devices (LVADs) are mechanical pumps that help the heart pump blood in patients with advanced heart failure
  • Can serve as a bridge to transplantation or as destination therapy
• Wearable and implantable devices (smartwatches, pacemakers, defibrillators) can monitor heart rhythm and deliver therapy when needed
  • Advances in miniaturization and wireless technology are expanding their capabilities