The Human Circulatory System

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RATIONAL One of the most important systems of all living organisms, entails the cardiovascular system. without the cardiovascular system we would not exist. It is important that students learn of the cardiovascular system and to investigate possible abnormalities that many people face on a daily basis.


OBJECTIVES STUDENTS WILL BE ABLE TO: Identify key terms Identify the structure of the heart identify the blood vessels Identify the electrical activity of the heart Lab: dissection of cow heart Lab: stress test Identify possible careers Identify EKG reports Understand medical conditions related to the heart


INTRODUCTION: The cardiovascular system is sometimes called the circulatory system Consists of the heart and a closed system of vessels called arteries, veins, and capillaries As in adults, survival of the developing embryo depends on the circulation of blood to maintain homeostasis. Therefore its appearance reaches a functional state long before any other major organ system Heart begins to beat in the 4th week after fertilization




LOCATION OF THE HEART 4 chambered muscular organ Shaped/sized roughly like a person’s closed fist Lies in the mediastinum between the points of attachment of the 2nd through 6th rib 2/3 of heart located on left side of the midline and 1/3 on the right. Posteriorly against T5th to T8th The position allows one to perform CPR


ANATOMICAL POSITION APEX: The lower border, which form a blunt point and lies on the diaphragm pointing toward the left Apex is formed by the ventricles To count the apical beat, one places a stethoscope directly over the apex at the 5th intercostal space on a line with the midpoint of the left clavicle. BASE the upper border of the heart, lies just below the 2nd rib The boundaries of course indicate its size and have considerable clinical importance.


SIZE AND SHAPE OF HEART At birth the heart is transverse (wide) and appears large in proportion to the diameter of the chest In infants it is 1/130 of the total body weight compared to 1/300 in an adult Between puberty and 25 yrs the heart attains its adult shape and weight About 300 g is average male and 225 g for females In adults the shape tends to resemble that of the chest (tall and thin the heart is elongated. Short and stocky the heart has a greater width)



Structure of the Heart Covering : 

Structure of the Heart Covering PERICARDIUM is a loose-fitting sac and consist of two parts: Fibrous portion tough, loose, and inelastic sac around the heart Serous portion consist of two layers PARIETAL LAYER: lining inside of the fibrous pericardium EPICARDIUM is a covering also known as the visceral layer It attaches to the large blood vessels emerging form the top of the heart but not to the heart itself PERICARDIAL SPACE is a slight space between the visceral layer (epicardium) and the parietal layer Contains 10-15 ml of lubricating fluid secreted by the serous membrane known as PERICARDIAL FLUID

Function of the Heart Coverings : 

Function of the Heart Coverings Provides protection against friction as long as the serous pericardium remains normal and continues to produce lubricating serous fluid



Wall of the Heart : 

Wall of the Heart Three layers of tissue make up the heart wall: Epicardium Myocardium Endocardium

Epicardium : 

Epicardium Outer layer Meaning “on the heart” Is actually the visceral layer of the serous pericardium

Myocardium : 

Myocardium Makes up the bulk of the heart wall Is the thick, contractile middle layer of specially constructed and arranged cardiac muscle cells Cardiac muscles cannot produce tetanus and thus do not fatigue

Endocardium : 

Endocardium The lining of the interior of the myocardial wall Composed of delicate layer of endothelial tissue, which line the heart and blood vessels

Chambers of the Heart : 

Chambers of the Heart Interior is divided into 4 chambers (cavities) ATRIA (ATRIUM) Two upper chambers VENTRICLES Two lower chambers SEPTUM the left chambers is separated form the right chambers by this heart wall

Atria : 

Atria Often called the “receiving chambers” They receive blood from vessels termed veins Veins are large blood vessels that return blood (not just de-oxygenated) from various tissues to the heart Atrial walls are not thick because they do not require great pressure to move blood such a small distance to the ventricles Auricle each part of an atrium has an earlike flap protruding form them

Ventricles : 

Ventricles Are the lower chambers Receive blood from the atria and pump blood out of the heart into arteries Are the “primary pumping chambers” of the heart Since more force is needed to pump blood the myocardium is thicker. The myocardium of the left is thicker because it has to push blood through most vessels of the body whereas the right pushes blood only to the vessels for the lungs Left ventricular heart failure is very serious because it hampers blood flow to the body Right ventricular heart failure causes fluid build up within the lungs (CHF) (TX. with lasix)

Values of the heart : 

Values of the heart Are mechanical devices that permit the flow of blood in one direction only Four sets of valves are important to the normal functioning of the heart. Two Atrioventricular valves (AV) Guard the opening between the atria and the ventricles Two Semilunar valves (SL) Located where the pulmonary artery (right ventricle) and the aorta (left ventricle) arise

Atrioventricular Valves : 

Atrioventricular Valves Tricuspid valve: The right atrioventricular valve guards the right atrioventricular orifice consisting of three flaps (cusps). The free edge of each flap is anchored to the papillary muscles by several cordlike structures termed chordae tendineae Bicuspid (or mitral valve): the left atrioventricular valve guards the left orifice Only has two flaps attached the same as the right. Both allows blood to flow from atria into ventricles but prevents it from flowing back into the atria because ventricular contraction place great force upon the AV to keep them closed

Semilunar Valves : 

Semilunar Valves Consist of half-moon shaped flaps growing out from the lining of the pulmonary artery and aorta Pulmonary semilunar valve Aortic semilunar valve When these valves are closed blood fills the spaces between the flaps and the vessel wall, which look like tiny filled buckets. Inflowing blood smoothes the flaps against the wall, collapsing the buckets and opening the valves Closure of the SL prevents backflow and ensures forward flow of blood

Surface projection(demo with stethoscopes) : 

Surface projection(demo with stethoscopes) When listening to the sounds of the heart on the body surface one must have an idea of the relationship between the valves and the surface of the thorax Base of heart = sternal notch Pulmonary semilunar valve = 2nd intercostal space on the left, close to sternum Aortic semilunar valve and mitral valve = 3rd intercostal space on the left with the aortic semilunar closer to the sternum Tricuspid valve = 4th intercostal space on the right side of sternum Apex = 5th intercostal space on left in line with clavicle

Blood Flow Through the Heart : 

Blood Flow Through the Heart

Blood Supply of Heart Tissue : 

Blood Supply of Heart Tissue

View of Heart: As if in your Chest : 

View of Heart: As if in your Chest


RESOURCES CLASSROOM CLIPART, October 30, 2005, Thibodeau, Gary; Patton, Kevein. “Anthony’s Textbook of Anatomy & Physiology”. 17th edition. Mosby