The Cardiovascular System

Amazing Heart Facts Your heart is about the same size as your fist. An average adult body contains about five quarts of blood. All the blood vessels in the body joined end to end would stretch 62,000 miles or two and a half times around the earth. The heart circulates the body's blood supply about 1,000 times each day. The heart pumps the equivalent of 5,000 to 6,000 quarts of blood each day. Weighs less than 1 lb.

Introduction A. Fully formed by the 4th week of embryonic development B. Hollow Muscular Organ That Acts as a 2 sided, Double Pump – Pump #1 – rt. side - O2 deficient - to the lungs; Pump #2 – left side – O2 rich – to the body C. Continuous pump - once pulsations begin, heart pumps endlessly until death

Heart Anatomy General 1. Size: approximately the size of a person’s fist 2. Location: in the mediastinum; between the lungs in the thoracic cavity Positioned partially to the left of the sternum

Coverings: Pericardium Double layered sac – parietal and visceral Contains 10 - 20 cc. Of pericardial fluid to reduce the friction of the beating heart Parietal layer: fibrous membrane; outer layer Visceral layer: serous membrane; also called the epicardium; attached to myocardium 3 tissue layers: Pericardium – double membrane that covers the outside of the heart; provides lubrication bvetw the heart and surrounding structures to prevent tissue damage

Heart Wall 1. Myocardium: heart muscle; thickest layer 2. Endocardium: smooth layer of cells lining the inside of the heart chambers; and forms the valves

Chambers: Atria a. 2 upper chambers of heart b.Thin walls, smooth inner surface c.Foramen ovale: passageway between the 2 atria so that the lungs are bypassed in the developing fetus d.Fossa ovale: scar tissue where the foramen ovale existed until it closed up shortly after birth Heart has 4 chambers – 2 upper = atria; 2 lower = ventricles

Atria Continued e.Responsible for receiving blood f. Right atrium receives deoxygenated (oxygen poor) blood from the body through the superior and inferior vena cava g. Left atrium receives oxygenated (oxygen rich) blood from the lungs through the pulmonary veins

Chambers: Ventricles a. 2 lower chambers of the heart b. Thicker walls, irregular inner surface c. Contain papillary muscles and chordae tendineae (prevent heart valves from turning inside out when ventricles contract) d. Left wall 3 times as thick as right wall; forms apex of heart

Ventricles Continued e.Responsible for pumping blood away from the heart f. Right ventricle sends deoxygenated blood to the lungs via the pulmonary arteries g. Left ventricle sends oxygenated blood to all parts of the body via the aorta

Accessory Structure a. Septum: muscular wall dividing the heart into right and left halves b. Heart valves - prevents the backflow of blood c. Papillary muscles d. Chordae tendineae 4 chambers of the heart are separated by the partitions called the septa. The interatrial septum divides the 2 upper chambers; the intraventricular septum divides the 2 ventricle. 4 Valves – prevent back flow of blood. Papillary muscles and chordae tendineae prevent heart valves from turning inside out when the ventricles contract

Great Vessels 1. Superior and inferior vena cava: receive deoxygenated blood from all parts of the body 2. Coronary sinus: carry O2 to the heart muscle itself 3. Pulmonary arteries: carry deoxygenated blood to the lungs from the right ventricle 4. Pulmonary veins: carry oxygenated blood to the left atrium from the lungs 5. Aorta: carries oxygenated blood to distribute to all parts of the body

Pathway of Blood through Heart Inferior/Superior Vena Cava Right Atrium Tricuspid Valve Right Ventricle Pulmonary Valve Pulmonary Artery Lungs Pulmonary Veins Left Atrium Bicuspid (mitral) Valve Left Ventricle Aortic Valve Aorta Body

Pathway of Blood through Body Aorta Arteries Arterioles Capillaries Venules Veins Superior/ inferior vena cava

Valves 1.Tough fibrous tissue between the heart chambers and major blood vessels of the heart 2.Gate-like structures to keep the blood flowing in one direction and to prevent regurgitation or backflow of blood

Atrio-ventricular valves When ventricles contract, blood is forced upward and the valves close; attached by papillary muscles and chordae tendineae a. Tricuspid valve: between the right atrium and the right ventricle b. Bicuspid/mitral valve: between the left atrium and the left ventricle A-V valves separate the atria from the ventricles; Cusp = flaps of the valves

Semilunar Valves: 3 half moon pockets that catch blood and balloon out to close the opening a. Pulmonary semilunar valve: between the right ventricle and the pulmonary arteries b. Aortic semilunar valve: between the left ventricle and the aortic arch/aorta

Heart Sounds a. When the AV (atrioventricular) and semilunar valves close, they make the sound heard as “lub- dub” (auscultated with stethoscope) b. First sound = S1 - ventricles are contracting and forcing blood to the lungs and entire body (AV valves closing) c. Second sound = S2 - atria are contracting and the semilunar valves are closing d.Abnormal heart sounds = murmur; valve pathology (M1, M2)

A. Nerve Supply to Heart 1. Alters rate and force of cardiac contraction 2. Vagus nerve (parasympathetic nervous system): slows heart rate 3. Sympathetic nerves: increase heart rate 4. Epinephrine/norepinephrine: increase heart rate 5. Sensory (afferent) nerves: detect atria being stretched and lack of oxygen (changes rate of contractions) Angina: chest pain due to lack of oxygen in coronary circulation

Arteries Veins Carry Blood away from heart Carry blood TOWARD heart All BUT Pulmonary vein carries unoxygenated blood Layers much thinner; elastic Series of internal valves that work against the flow of gravity to prevent reflux Inferior/superior vena cava:largest Venules:smallest Carry Blood away from heart All BUT pulmonary artery carries oxygenated blood Aorta:largest artery Arterioles: smallest Coronary arteries: nourish heart

Capillaries 1. Tiny, microscopic vessels 2. Walls one cell layer thick 3. Function: to transport and diffuse essential materials to and from the body’s cells and the blood

Circulation

Function of Circulatory System An efficient pumping system to supply all body systems with oxygen and nutrients Transport cellular waste products from the cells to the kidneys for excretion An important role in the immune system – distributes hormones and antibodies throughout the body Helps control body temperature and maintain electrolyte balance