The Circulatory System

Circulatory System Also known as the Cardiovascular System Consists of: Heart Blood Vessels Blood

Functions of the Circulatory System Transports oxygen and nutrients to all body cells Transports carbon dioxide and metabolic materials away from the body cells

Blood Vessels Include: Arteries Veins Capillaries

Arteries Blood Vessels that carry blood away from the heart More muscular and elastic than the other vessels Largest artery is the Aorta Smallest branches are called arterioles Join with capillaries Contain oxygen rich blood except the Pulmonary Artery

Veins Blood vessels that carry blood back to the heart Venules , the smallest branches of veins, connect with the capillaries (join together and become larger veins) The 2 largest veins: Superior Vena Cava and Inferior Vena Cava Veins are thinner and less muscle tissue Most contain valves which keep the blood flowing in one direction

Capillaries Blood vessels that connect arterioles (smallest arteries) with venules (smallest veins) Smallest blood vessels Contain thin walls that allow oxygen and nutrients to pass through to the cells Also, allow carbon dioxide and metabolic waste products to enter these vessels for removal from the cell

Heart Muscular, hollow organ functions as pump Weighs less than one pound Size of closed fist Located in the mediastinal cavity, between the lungs, behind the sternum and above the diaphragm

Heart Facts The heart contracts about 100,000 times each day to pump the equivalent of 2,000 gallons of blood through the body. The human heart beats 35 million times in a year. In a lifetime, the heart pumps around 1 million barrels of blood.

Layers of the Heart Three layers of tissue include: Endocardium – smooth layer which lines the inside of the heart Myocardium – thick, middle muscular layer Pericardium – double layered membrane or sac that covers the outside of the heart A lubricating fluid, pericardial fluid, fills the space between the two layers. This fluid helps prevent friction and damage to the membrane as the heart beats.

Septum A muscular wall that separates the heart into a right side and a left side Prevents blood from moving between the 2 sides Upper part of the septum is called the interatrial septum Lower part of the septum is called the interventricular septum

Heart Chambers The heart is divided into four parts, or chambers. 2 upper chambers are called atrias (atriums) 2 lower chambers are called ventricles

Blood Flow (Right Side of Heart) The Right Atrium receives blood as it returns from the body cells via the Superior Vena Cava and Inferior Vena Cava. The Right Ventricle receives blood from the Right Atrium and pumps the blood into the Pulmonary Artery, which carries the blood to the lungs for oxygen.

Blood Flow (Left Side of the Heart) The Left Atrium receives oxygenated blood from the lungs via the Pulmonary Veins. The Left Ventricle receives blood from the Left Atrium. The blood is pumped into the Aorta for transport to the body cells.

Heart Valves One way valves in the chambers of the heart keep the blood flowing in the right direction.

Heart Valves on Right Side The Tricuspid Valve is located between the right atrium and the right ventricle (contains 3 cusps or leaflets). The Pulmonary Valve is located between the right ventricle and the pulmonary artery (contain 3 cusps or leaflets).

Heart Valves on Left Side The Mitral (Bicuspid) Valve is located between the left atrium and the left ventricle (contains 2 cusps or leaflets). The Aortic Valve is located between the left ventricle and the aorta (2 cusps or leaflets).

Heart Valves This three dimensional image shows the heart valves functioning. Look close at the 3D of the heart (on the right), the leaflets of the tricuspid and aortic valves are partly visible. The 2 left images show the tricuspid and mitral valves (above) and aortic and mitral valves (below). http://www.heart-valve-surgery.com/heart-surgery-blog/2008/03/21/what-do-normal-heart-valves-look-like/

Cardiac (Heartbeat) Cycle Even though the 2 sides of the heart are separated by the septum, these 2 sides work together in a cyclic manner. The cycle consists of a brief period of rest called diastole, followed by a period of ventricular contraction, called systole.

Cardiac Cycle Start of a cycle Atria contracts Blood pushed into ventricle Atria relaxes Blood enters from superior & inferior vena cava on right side and blood enters from pulmonary veins on left side Atria filling, systole begins, and the ventricle contract Contraction of ventricles pushes blood into pulmonary artery on right side and pushes blood into aorta on the left side

Beating Heart http://www.innerbody.com/anim/heart.html

Pulmonary Circulation Blood on the right side of the heart is deoxygenated meaning it is very oxygen poor and high in carbon dioxide. The blood enters the lungs via the pulmonary artery. When the blood arrives in the lung, the carbon dioxide is released into the lungs, and then oxygen is taken into the blood (occurs in capillary beds in lungs) . Once the blood returns to the heart on the left side, it is filled with oxygenated blood (oxygen rich).

Review Right Side of Heart Left Side of Heart Deoxygenated Blood Oxygenated Blood (Oxygen Poor) (Oxygen Rich)

Blood Flow Through Right Side of Heart Superior Vena Cava and Inferior Vena Cava Right Atrium Tricuspid Valve Right Ventricle Pulmonary Valve Pulmonary Artery To the Lungs DEOXYGENATED BLOOD

Blood Flow Through Left Side of Heart From Lungs Pulmonary Veins Left Atrium Mitral (Bicuspid) Valve Left Ventricle Aortic Valve Aorta To the Body OXYGENATED BLOOD

Conductive Pathway Electrical impulses cause the cyclic contractions of the heart. These impulses start in the atria and then move down through the ventricles. Sinoatrial (SA) Node – group of nerve cells in the right atrium. “Pacemaker” of the heart. Atrioventricular (AV) Node – group of nerve fibers between the atria and ventricles.

Conductive Pathway 3) Bundle of His – group of nerve fibers in the septum. 4) Right Bundle Branch and Left Bundle Branch – nerve fibers that carry the impulse down the ventricles. 5) Purkinje Fibers – a network of nerve fibers located throughout the ventricles.

Electrocardiogram This electrical conduction pattern occurs approximately every 0.8 seconds. The electrical impulses can be recorded on an electrocardiogram (ECG or EKG) and used to detect abnormal activity or disease.

EKG: Electrocardiogram

Arrhythmias If something interferes with the normal electrical conduction pattern of the heart, then arrhythmias occur. These abnormal heart rhythms can be life threatening. Ventricular fibrillation (V-Fib) occurs when the ventricles contract without coordination which decreases blood output. A defibrillator (device which shocks the heart with a electrical current) is used. After a successful shock, the SA node is able to regain control.

Heart Review