The Cardiovascular System

The functions of the cardiovascular system are: – Supply oxygen to tissues from the lungs – Supply nutrients to tissues from the digestive tract – Remove wastes from tissues and take them to the lungs or kidneys or liver. The study of the heart and diseases associated with it is termed cardiology. The heart lies in the mediastinum between the lungs with about 2/3 of it on the left of the body’s midline. The heart is the size of a closed fist.

Coverings of the Heart The pericardium surrounds and protects the external heart and holds it in place. – 3 parts to the pericardium from the outside to the inside: Fibrous pericardium- Tough, inelastic connective tissue that prevents overstretching. Parietal pericardium- Fused to the fibrous pericardium. Visceral pericardium- Also called the epicardium and adheres tightly to the heart.  Between the parietal and visceral layers is the pericardial space containing pericardial fluid which reduces friction as the heart moves.  Inflammation of the pericardium is called pericarditis.

The inside of the hollow heart (where the blood flows) is a smooth covering called the endocardium. The majority of the heart is the myocardium which is the cardiac muscle that pumps the blood throughout the body.

Heart Chambers The heart has four internal chambers: two atria (right/left) on top and two ventricles (right/left) on bottom. – Atria receive blood returning to the heart and have thin walls. On the exterior surface of each is a wrinkled pouch-like structure called an auricle. – The thick-muscled ventricles pump blood to out of the heart. The left ventricle is considerably larger. – The right and left atria are divided by an interatrial septum. – The right and left ventricles are separated by an interventricular septum.

Valves are one-way “doors” that open and close in response to pressure changes. They allow blood to flow in one direction in the heart. Atrioventricular valves (AV) are between the atria and ventricles. The right AV valve is the tricuspid and the left AV valve is the bicuspid or mitral. Both of these valves have tendonlike cords called chordae tendineae. Chordae tendineae are attached to papillary muscles in the inner heart wall that contract when ventricles contract to prevent the backflow of blood through the AV valves. Heart Valves

Heart Valves continued…. In between the ventricles and the major arteries taking blood away from the heart are 2 semilunar valves (SL). The right SL valve is the pulmonary valve and the left SL valve is the aortic valve.

Major Heart Blood Vessels Superior Vena Cava- Returns blood to the right atrium from above the heart. Inferior Vena Cava- Returns blood to the right atrium from below the heart. Pulmonary Trunk- Carries blood from the right ventricle and branches into the right and left pulmonary arteries leading to the lungs. Pulmonary Veins- Return oxygenated blood to the left atrium. Aorta- Carries oxygenated blood away from the left ventricle and directs it to the body.

Label the Heart

How the Chordae Tendineae Work

Blood Vessel Types There are 5 types of blood vessels in the cardiovascular system: – Arteries- Carry blood away from the heart – Arterioles- Smaller arteries – Capillaries- Smaller arterioles that are 1 cell thick – Venules- Groups of capillaries – Veins- Return blood to the heart

Blood Vessels

Flow of blood through heart and body There are 2 branches of the cardiovascular system: pulmonary and systemic circulation. Pulmonary circulation- The right side of the heart pumps blood to the lungs to pick up oxygen and drop off carbon dioxide. Systemic circulation- The left side of the heart pumps blood to the body to drop off the oxygen and pick up carbon dioxide waste. **Pulmonary and Systemic circulation happen simultaneously

Pulmonary Circulation Blood Flow

Systemic Circulation Blood Flow

Differences in Right and Left Ventricles- Now that you know the blood flow, why is the left ventricle so large?

Blood Supply to the Heart The first branches off of the aorta, which carry freshly oxygenated blood, are the right and left coronary arteries that feed the heart muscle itself. Branches of the coronary arteries feed many capillaries of the myocardium. When these arteries become clogged due to the build up of fats and cholesterol, new arteries must be attached to “by pass” these clogged arteries. Cardiac veins drain blood from the heart muscle and carry it to the coronary sinus (large vein on posterior side of heart), which empties into the right atrium.

Coronary Sinus

Coronary Arteries Bypass Graft Animation Bypass Graft Animation

SHEEP HEART DISSECTION: External: Aorta Superior Vena Cava R/L Auricle R/L Atrium R/L Ventricle Pericardium Myocardium Apex Base Pulmonary Artery Pulmonary Vein R/L Coronary Artery Coronary Sinus Internal: Tricuspid Valve Mitral/Bicuspid Valve Pulmonary Valve Aortic Valve Chordae Tendineae Papillary Muscle Endocardium Interventricular Septum R/L Atrium R/L Ventricle Pulmonary Artery Pulmonary Veins Aorta

Stress and Heart Disease Prolonged stress can wreak havoc on your cardiovascular system. Stress means that we are operating in a “fight or flight” manner- Preparing the body to meet a challenge This reaction is caused by the release of adrenaline Adrenaline causes the heart beat to increase, blood pressure to increase, blood sugar levels to increase, and the digestion and immune systems to become suppressed. The body frequently experiencing this can be damaging.

The Heart Beat The heart beat is due to electrical impulses flowing throughout the heart. This begins in the Sinoatrial (SA) node (node=group of muscles) in the right atrium just below the opening of the Superior Vena Cava. The SA node is called the “pacemaker” because it regulates the heart rate. This signals the muscle tissue in the right and left atria to simultaneously contract- forcing blood into the ventricles. The Atrioventricular (AV) node located in the interatrial septum also receives the message from the SA node and forwards it onto the atrioventricular bundle, then onto the right and left bundle branches and finally the Purkinje fibers.

Heart Beat continued… When the message is received by the Purkinje fibers, the ventricles contract (including the papillary muscles inside of them).

Putting it all together… The atria contract at the same time, followed by the ventricles contracting at the same time. When the atria fill, pressure in the atria is greater than that of the ventricles, which forces the AV valves open. Pressure inside atria rises further as they contract (due to the SA node), forcing the remaining blood into the ventricles. When ventricles contract (due to the Purkinje fibers), pressure inside them increases sharply, causing the aortic and pulmonary valves to open. - As the ventricles contract, papillary muscles contract, pulling on chordae tendineae and preventing the backflow of blood through the AV valves.

When the atria fill with blood, the AV valves open and 75% of the blood in the atria passes down into the ventricles When the atria get the message to contract, the remaining 25% of the blood is forced into the ventricles. Ventricles Operation of the AV valves AV valves open

When the ventricles contract, blood is forced against the AV valves, forcing them to close. Chordae tendineae tighten, preventing valve flaps from everting into the atria AV valves closed

As ventricles contract, blood is pushed up against semilunar valves, forcing them open Aorta Pulmonary trunk Semilunar valve open Semilunar valve closed As ventricles relax, blood flows back from the arteries, filling the leaflets of the semilunar valves and forces them to close

Heart Sounds Heart sounds can be described as a "lubb-dupp" sound. The first sound (lubb) occurs as ventricles contract and AV valves are closing. The second sound (dupp) occurs as atria contract and SL valves are closing. A heart murmur is an abnormal sound consisting of a rushing or gurgling noise. Most often this is due to a valve disorder.

The Heart: Cardiac Cycle The term systole means contraction and diastole means relaxation. The cardiac cycle consists of 3 phases: 1. Relaxation period- Brief period of time when all 4 chambers are relaxed. 2. Atrial systole (ventricular diastole)- This is when the atria contract and the AV valves are open (SL closed). 3. Ventricular systole (atrial diastole)- This is when the ventricles contract and the SL valves are open (AV closed).

Electrocardiogram Electric currents that run through the heart can be picked up by electrodes that are placed on a person’s skin. A recording of the electrical changes during a person’s heart beat is called an electrocardiogram or ECG or EKG. There are 3 waves viewed during an EKG: – 1. P wave- when the current passes from the SA node throughout the atria- which causes them to contract. – 2. QRS complex- When the current spreads throughout the ventricles- which causes them to contract. – 3. T wave- Current change of the ventricles as they start to relax.

Normal ECG

Valves open Valves closed Active node and/or nerves Sound made EKG wave Ventricular Systole Atrial Systole

Common Heart Disorders Heart block- Disorder when the electrical system of the heart is damaged. Angina pectoris- Chest pain due to reduced blood flow to the myocardium. Arrhythmia- Irregular heart rhythm Tachycardia- Heart beat that is too rapid. Bradycardia- Heart beat that is too slow. Fibrillation- Rapid, irregular, and unsynchronized contraction of muscle fibers. Cardiac arrest- Cessation of a regular heart beat.

A pacemaker is an electronic device placed most often below your collarbone on the left or right side of your chest. A pacemaker contains a battery and computer circuitry in a metal case to correct slow heart rhythms. The pacemaker monitors your heart all the time, and if it detects a slow rhythm issue, it sends out small undetectable electrical signals to correct it.