The Circulatory System (a.k.a. The Cardiovascular System)

Consists of the heart, blood vessels, and blood Function: ◦Transports oxygen and nutrients to body cells ◦Transports carbon dioxide and metabolic materials away from body cells

The Heart Muscular hollow organ Often called the pump of the body Weighs less than one pound About the size of a closed fist Contracts about 100,000 times each day to pump the equivalent of 2,000 gallons of blood through the body Located in the medial to the lungs, deep to the sternum, and superior to the diaphragm

Three layers of tissue form the heart Endocardium ◦Smooth layer of cells ◦Lines the inside of the heart ◦Allows for smooth flow of blood Myocardium ◦Thickest layer ◦Muscular middle layer Pericardium ◦Double layered membrane or sac ◦Covers outside of heart ◦Fluid fills space between two layers and prevents friction and damage to membranes as the heart beats, or contracts

The Septum Muscular wall Separates heart into a right and left side Prevents blood from moving between the right and left side of the heart

Heart Chambers Heart is divided into four parts (chambers) Two upper chambers are called atria Two lower chambers are called ventricles

Heart Chambers Right atrium receives blood as it returns from the body Right ventricles ◦Receives blood from the right atrium (Pushes blood into the pulmonary artery, which carries the blood to the lungs for oxygen) Left atrium receives oxygenated blood from the lungs by way of pulmonary vein Left ventricle ◦Receives blood from the left atrium ◦Pushes blood into the aorta so it can be carried to the body

Valves One way valves in the chambers of the heart keep blood flowing in the proper direction

TRICUSPID VALVE Located between the right atrium and right ventricle Closes when right ventricle contracts and pushes blood into the lungs Prevents blood from flowing back into the right atrium

Pulmonary Valve Located between right ventricle and pulmonary artery (blood vessel that carries blood to lungs) Closes when right ventricle has finished contracting and pushing blood into pulmonary artery Prevents blood from flowing back into right ventricle

Mitral Valve Located between left atrium and left ventricle Closes when left ventricle is contracting and pushing blood into aorta so blood can be carried to the body Prevents blood from flowing back into left atrium

Aortic Valve Located between left ventricle and aorta, largest artery in the body Closes when left ventricle is finished contracting and pushing blood into aorta Prevents blood from flowing back into left ventricle

The right and left sides of the heart work together in a cyclic manner even though they are separated by the septum.

The Cardiac Cycle  Electrical impulse originating in heart causes myocardium to contract in cyclic manner  Cycle consists of brief period of rest, called diastole, followed by of ventricular contraction called systole

Is the blood in the right side of the heart oxygenated or deoxygenated? Left?

Conductive Pathway

Electrical impulses originating in the heart triggers cyclic contraction of muscles.

Sinoatrial (SA) Node Electrical impulse starts in the SA node Group of nerve cells located in right atrium Also called the “pacemaker” Sends out electrical impulse that spreads out over muscles in atria Atrial muscles then contract and push blood into ventricles After electrical impulse passes through atria it reaches atrioventricular (AV) node

Atrioventricular (AV) node Group of nerve cells located between atria and ventricles AV node sends electrical impulse through nerve fibers in the septum called the bundle of HIS

Bundle of HIS Nerve fibers in septum Divides into a right and left bundle branch

Right and Left Bundle Branches Pathways that carry the impulse down through ventricles Bundles continue to subdivide into network of nerve fibers throughout ventricles called Purkinje fibers

Purkinje Fibers Final fibers on conduction pathway Spread electrical impulse to all muscle tissue in ventricles Ventricles then contract

Electrical conduction pattern occurs approximately every 0.8 seconds Movement of electrical impulse can be recorded on an ECG/EKG and used to detect abnormal activity or disease

Arrhythmias Interference with normal electrical conduction pattern of the heart which causes abnormal heart rhythms

Arrythmias can be mild to life-threatening ◦Premature atrial contraction (PAC), an early contraction of the atria, can occur in anyone and usually goes unnoticed ◦Ventricular fibrillation, in which ventricles contract at random without coordination decreases or eliminates blood output and causes death if not treated Cardiac monitors and electrocardiograms (ECG) are used to diagnose arrythmias

Treatment of arrythmias Life-threatening fibrillations are treated with a defibrillator ◦Device that shocks the heart with an electrical current ◦Stops uncoordinated contraction ◦Allows SA node to regain control

Internal Artificial Pacemaker Small battery-powered device with electrodes Electrodes are threaded through a vein and positioned in right atrium and in apex of right ventricle Pacemaker monitors heart’s activity and delivers electrical impulse through electrodes to stimulate contraction

Educate your patients with pacemakers to not store cell phones in shirt pocket. It could alter signals sent from the pacemaker.

Blood Vessels Blood leaving the heart is carried throughout the body in blood vessels Heart and blood vessels form a closed system for flow of blood Three main types of blood vessels are: ◦Arteries ◦Capillaries ◦Veins

Arteries Carries blood away from the heart Aorta ◦Largest artery in the body ◦Receives blood from left ventricle of the heart ◦Branches off into all other arteries that supply blood to the body Arterioles ◦Smallest branches of arteries ◦Join with capillaries

Capillaries Connect arterioles with venules, the smallest veins Located in close proximity to almost every cell in the body Have thin walls that contain only one layer of cells Allow oxygen and nutrients to pass through the cells At the same time, carbon dioxide and metabolic products from the cells enter the capillaries

Veins Blood vessels that carry blood back to the heart Venules- ◦Smallest branches of veins ◦Connect with capillaries ◦Venules join together and become larger to form veins

Veins Superior and Inferior Vena Cava ◦Two largest veins ◦Superior vena cava brings blood from upper part of the body ◦Inferior vena cava brings blood from lower part of the body ◦Both vena cava empty blood into right atrium **Most veins contain valves that keep blood from flowing backward**

Blood Composition

Blood is often called a tissue because it contains many kind of cells About four to six quarts of blood are in the average adult Blood circulates throughout the body continually

Blood transports many substances ◦Oxygen from lungs to the body cells ◦Carbon dioxide from body cells to lungs ◦Nutrients from digestive tract to cells ◦Metabolic waste products from cells to organs of excretion ◦Hormones produced by endocrine glands to organs in the body

Plasma Plasma is the fluid or liquid portion of blood (Plasma makes up 55% of our blood) About 90% of plasma is water Many substances are dissolved or suspended in the water ◦Blood proteins ◦Nutrients ◦Mineral salts or electrolytes ◦Gases ◦Wastes ◦Hormones ◦Enzymes

Blood Cells

Blood cells are the solid elements of blood Three main kinds of blood cells ◦Erythrocytes ◦Leukocytes ◦Thrombocytes

Erythrocytes (red blood cells) Produced in the red bone marrow at a rate of about 1 million per minute Live about 120 days before being broken down by the liver and spleen There are million erythrocytes per cubic ml (one gtt) OR 25 trillion in the body

Erythrocytes contain a protein called Hemoglobin Composed of a protein molecule called globin and an iron compound called heme Carries both oxygen and carbon dioxide When hemoglobin carries oxygen, it gives blood its characteristic red color If blood contains a lot of oxygen it is bright red When there is less oxygen and more carbon dioxide, blood is a much darker red

Leukocytes (white blood cells) Not as numerous as erythrocytes Formed in the bone marrow and lymph tissue and usually live about 3-9 days Normal count is leukocytes per cub ml of blood Leukocytes can pass through capillary walls and enter body tissue Main function is to fight infection

Leukocytes continued… Phagocytosis- process by which some leukocytes engulf, ingest, and destroy pathogens, or germs