Cardiovascular System: Anatomy and Function

• The cardiovascular system's organs and functions and trace the blood flow, underscoring its importance and care.

Introduction

• The cardiovascular system comprises the heart and blood vessels, ensuring blood circulation.
• Blood carries oxygen to the lungs and nutrients to the digestive system.
• It transports waste to specific organ systems for removal.

The Heart: Structures

• The heart, a cone-shaped organ, resembles a loose fist in size.
• The heart resides in the mediastinum.
• Extends from the second to the sixth rib's level.
• Slightly positioned left of the midline.
• Bordered laterally by the lungs, posteriorly by the vertebral column, and anteriorly by the sternum.
• Inferiorly rests on the diaphragm.

Heart Coverings

• The pericardium covers the heart and attached large blood vessels.
• Visceral pericardium is the innermost layer directly on the heart.
• Parietal pericardium overlays the visceral pericardium.

Heart Walls

• Epicardium: the outermost layer mostly made of fat to cushion the heart.
• Myocardium is the middle layer primarily composed of cardiac muscle
• Endocardium is the innermost layer, thin, smooth, and stretches as the heart pumps.

Four Chambers

• Two Atria: upper, left, and right chambers, separated by the interatrial septum.
• Two Ventricles: lower, left, and right chambers, separated by the interventricular septum.
• The atrioventricular septum separates the atria from the ventricles.

Heart Valves

• Tricuspid valve: prevents backflow into the right atrium during right ventricle contraction.
• Bicuspid valve: prevents backflow into the left atrium during left ventricle contraction.
• Pulmonary valve: prevents backflow into the right ventricle.
• Aortic valve: prevents backflow into the left ventricle.

The Heart: Cardiac Cycle

• One heartbeat equates to one cardiac cycle.
• Atria contract and relax while ventricles then do so.
• Right atrium contracts: the tricuspid valve opens, and blood fills the right ventricle.
• Right ventricle contracts: the tricuspid valve closes, the pulmonary semilunar valve opens, and blood flows into the pulmonary artery.
• Left atrium contracts: the bicuspid valve opens, and blood fills the left ventricle.
• Left ventricle contracts: the bicuspid valve closes, the aortic semilunar valve opens, and blood is pushed into the aorta.

The Heart: Heart Sounds

• Each cardiac cycle produces two heart sounds, "lubb" and "dubb," from valve closures.
• Lubb is the first sound, made when the ventricles contract, the tricuspid and bicuspid valves snap shut.
• Dubb is the second sound, made when the atria contract, the pulmonary and aortic valves snap shut.

The Heart: Cardiac Conduction System

• A group of structures sends electrical impulses throughout the heart.
• Sinoatrial Node (SA node): located in the wall of the right atrium, generating impulses as the natural pacemaker, sending impulses to the AV node.
• Atrioventricular Node (AV node) locates between atria just above ventricles, causing atria to contract and sending impulses to the bundle of His.
• Bundle of His: located between the ventricles, with two branches and sends impulses to the Purkinje fibers.
• Purkinje Fibers: located in the lateral walls of the ventricles, causing ventricles to contract.

Blood Vessels: Arteries and Arterioles

• Arteries are the strongest blood vessels; carry blood away from the heart.
• High blood pressure regulates vasoconstriction and vasodilation.
• Aorta: takes blood from the heart to the body.
• Coronary arteries: supply blood to the heart muscle.
• Arterioles: small branches of arteries.

Blood Vessels: Veins and Venules

• Blood has no pressure in the veins.
• Blood does not move very easily in the veins.
• Skeletal muscle contractions and the sympathetic nervous system help move blood.
• Valves prevent backflow.
• Venules are small vessels formed when capillaries merge.
• Superior and inferior vena cava are the largest veins, carrying blood into the right atrium.

Blood Vessels: Capillaries

• They are branches of arterioles, the smallest type of blood vessel.
• Capillaries connect arterioles to venules and are only one cell layer thick.
• Oxygen and nutrients pass out of the capillary to a body cell.
• Carbon dioxide and other waste products pass out of a body cell into a capillary.

Blood Pressure

• The force blood exerts on the inner walls of blood vessels.
• Highest in arteries; lowest in veins.
• Systolic pressure: ventricles contract, blood pressure is at its greatest in the arteries.
• Diastolic pressure: ventricles relax, blood pressure in arteries is at its lowest.
• Reported as the systolic number over the diastolic number.
• Control is based mainly on the amount of blood pumped out of the heart.
• The amount of blood entering should equal the amount pumped from the heart.
• Starling's law of the heart: blood entering the left ventricle stretches the wall of the ventricle.
• The more the wall is stretched, the harder it will contract, and the more blood it will pump out.

Circulation

• Pulmonary circuit: right atrium → right ventricle → pulmonary artery trunk → pulmonary arteries → lungs → pulmonary veins → heart (left atrium).
• Systemic circuit: left atrium → left ventricle → aorta → arteries → arterioles → capillaries → venules → veins → vena cava → heart (right atrium).
• Arterial System: carries oxygen-rich blood away from the heart, but pulmonary arteries carry oxygen-poor blood.
• Arteries exist in pairs, left and right, sharing the same name.
• Venous System: carries oxygen-poor blood toward the heart, with the exception of the pulmonary veins.
• Most large veins share names with the arteries they are next to.
• Hepatic portal system: a collection of veins carrying blood to the liver.

Blood

• A type of connective tissue comprises red blood cells (erythrocytes), white blood cells (leukocytes), platelets (cell fragments), and plasma (fluid part of blood).
• Average-sized adult has 4 to 6 liters of blood, dependent on size, adipose tissue, concentrations of ions, and sex.
• Karl Landsteiner discovered the ABO blood system that contained 4 blood types in 1901.
• Blood loss can occur from surgery, injury, or illness. A person transfused with an incompatible blood type may have a life-threatening reaction, with the body's immune system (white blood cells) attacking it.
• Erythrocytes: red blood cells; transport oxygen throughout the body; small biconcave-shaped cells.
• Hemoglobin is a pigment in RBCs. Anemia indicates a low RBC count.
• Erythropoietin regulates the production of RBCs.
• Granulocytes:
  • Neutrophils (55%) destroy bacteria, viruses, and toxins in the bloodstream.
  • Eosinophils (3%) get rid of parasitic infections such as worm infections.
  • Basophils (1%) control inflammation and allergic reactions.
• Agranulocytes:
  • Monocytes (8%) destroy bacteria, viruses, and toxins in the blood.
  • Lymphocytes (33%) provide immunity for the body.
• Platelets: fragments of cells found in the bloodstream; also called thrombocytes.
• Play an important role in the clotting process of blood.
• Normal count: 130,000 to 360,000 platelets per cubic millimeter of blood.
• Plasma: liquid portion of blood composed mostly of water.
• Proteins such as Albumins are plasma proteins that pull water in to help maintain blood pressure, Globulins transport lipids and fat-soluble vitamins, and Fibrinogen needed for blood clotting.
• Nutrients include amino acids, glucose, nucleotides, and lipids from the digestive tract.
• Gases include oxygen, carbon dioxide, and nitrogen
• Also contains Electrolytes and Waste products
• Blood Types
  • Types are distinguished by antigen and antibodies.
  • Agglutination (clumping of red blood cells.
• Antigens on surface of RBCs bind to antibodies in plasma.
• Rh antigen – protein on RBCs.
• Rh-positive: RBCs contain the Rh antigen.
• Rh-negative: RBCs do not contain the Rh antigen.
• Rh-positive blood to Rh-negative person causes antibodies to form.

Diseases and Disorders of the Cardiovascular System

• Anemia: the blood doesn't have enough red blood cells or hemoglobin to carry an adequate amount of oxygen to the body's cells.
• Aneurysm: a ballooned, weakened arterial wall.
• Arrhythmias: abnormal heart rhythms.
• Carditis: inflammation of the heart.
• Endocarditis: Inflammation of the innermost lining of the heart.
• Myocarditis: Inflammation of the muscular layer of the heart.
• Pericarditis: Inflammation of the membranes that surround the heart (pericardium).
• Congestive Heart Failure: Weakening of the heart over time, heart unable to pump enough blood to meet body's needs
• Coronary Artery Disease (CAD): Atherosclerosis; narrowing of coronary arteries caused by hardening of the fatty plaque deposits within the arteries
• Hypertension: High blood pressure; consistent resting blood pressure equal to or greater than 140/90 mm Hg.
• Leukemia: bone marrow produces a large number of abnormal WBCS.
• Murmurs: abnormal heart sounds.
• Myocardial Infarction: Heart attack; damage to cardiac muscle due to a lack of blood supply
• Sickle Cell Anemia: abnormal hemoglobin causes RBCs to change to a sickle shape; abnormal cells stick in capillaries.
• Thalassemia: inherited form of anemia; defective hemoglobin chain causes small, pale, and short-lived RBCs.
• Thrombophlebitis: blood clots and inflammation develops in a vein.
• Varicose Veins: twisted, dilated veins.