Introduction; The Cardiovascular System (CVS) Pathophysiology BMS 243 Lecture I Introduction; The Cardiovascular System (CVS) Dr. Aya M. Serry 2017

10 20 40 100 SUBJECT GRADE Quizzes First Assessment Exam Second Assessment Exam Self Learning (Project) Final Exam 40 TOTAL 100

Course Objectives Upon Completion of this course you should be able to: Understand the relationship between the symptoms and the disease, which might be helpful in differential diagnosis Understand mechanisms of different diseases Discuss the etiology, pathogenesis, morphology and clinical significance of selected disorders of the cardiovascular, pulmonary, Female reproductive, renal, GIT and endocrine systems Understand the causes and systemic, cellular and sub-cellular mechanisms of the development of the most significant diseases and their symptoms and syndromes.

Definition of Pathophysiology

Lecture Objectives… Identifying the Components of the cardiovascular system 1 Revising the general structure of the heart and its Basic Functions 2

CVS Introduction The main function of the Cardiovascular System which consists of the heart and blood vessels, is transportation. It delivers oxygen and nutrients needed for metabolic processes to the tissues. It also circulates electrolytes and hormones needed to regulate body function.

Introduction The cardiovascular system (CVS) consists of the heart and blood vessels. It is a closed system in which blood circulates, hence the synonym ‘circulatory system’.

Components of the CVS The Heart: The heart is a four-chambered pump consisting of: Two Atria (the right atrium, which receives blood returning to the heart from the systemic circulation, and the left atrium, which receives oxygenated blood from the lungs) Two ventricles (a right ventricle, which pumps blood to the lungs, and a left ventricle, which pumps blood into the systemic circulation).

Components of the CVS The Heart:

Heart Chambers The Two atria (right and left) are separated from each other by the interatrial septum. While, The Two ventricles (right and left) are separated from each other by the interventricular septum. **The wall of the left ventricle is about 3 times thicker than the wall of the right ventricle; The increased thickness of the left ventricular wall results from the additional work this ventricle is required to perform in order to move oxygenated blood to the extremities.

Functions of The Atria The atria have 2 main functions: 1)They act as blood reservoir for the blood returning back from the body to the heart. 2)They act as pumps (primer pumps). Atrial contraction pushes about 25% of the blood filling the ventricles during ventricular diastole.

Functions of The Ventricles The function of the ventricles : Are the powerful cardiac pumps filling the arteries with blood. The right ventricle pushes blood into the pulmonary arteries, while the left ventricle pushes blood into the aorta during ventricular systole.

Layers of the Heart The heart is a hollow muscular organ. The wall of the heart is composed of an outer epicardium, which lines the pericardial cavity; the myocardium or muscle layer; and the smooth endocardium, which lines the chambers of the heart

Components of the CVS Blood Vessels: The blood vessels are systems of tubes including: Arterial System; which carries the blood from the heart to all parts of the body. The arterial system consists of the large- and medium-sized arteries and the arterioles. Arteries are thick-walled vessels with large amounts of elastic fibers. The elasticity of these vessels allows them to stretch during systole, when the heart contracts and blood enters the circulation, and to recoil during diastole, when the heart relaxes.

Components of the CVS Blood Vessels: The blood vessels are systems of tubes including: b) Venous System; which carry the blood back from the tissues to the heart. The venules collect blood from the capillaries, and the veins transport blood back to the right side of the heart. c) Capillary System; which form a network of fine vessels connecting the arteriols with the venules, and they are the sites of exchange of gases (O2 & CO2).

Blood Circulation The circulatory system can be divided into two parts: The pulmonary circulation, which moves blood through the lungs and creates a link with the gas exchange function of the respiratory system The systemic circulation, which supplies all the other tissues of the body

PULMONARY AND SYSTEMIC CIRCULATIONS…

Blood Circulation The pulmonary circulation [ starts from the right ventricle, ends in the left ventricle] The pulmonary circulation consists of the right heart, the pulmonary artery, the pulmonary capillaries, and the pulmonary veins. The large pulmonary vessels are unique in that the pulmonary artery is the only artery that carries venous blood and the pulmonary veins are the only veins that carry arterial blood.

Blood Circulation The pulmonary circulation The Pulmonary circulation is considered low pressure and low resistance since it is a short system only involving blood to and from the lungs. The low pressure of the pulmonary circulation allows blood to move through the lungs more slowly, which is important for gas exchange.

Blood Circulation The systemic circulation[ starts from the left Ventricle, ends in the right Atrium] The Systemic Circulation consists of the left heart, the aorta and its branches, the capillaries that supply the brain and peripheral tissues, and the systemic venous system and the vena cava. The veins from the lower portion of the body merge to form the inferior vena cava, and those from the head and upper extremities merge to form the superior vena cava, both of which empty into the right heart.

Blood Circulation The systemic circulation This circulation is more complex with higher pressures since it involves a complex vascular tree that provides substantial resistance to blood flow due to the effects of gravity.

Heart beats A heart beat consists of a systole + a diastole of cardiac chambers. The heart of a normal adult male beats automatically and regularly at a rate of 75 beats/minute during rest. The normal range of heart rate is between 60 – 100 beats /minute.

Heart beats The heart rate determines the frequency with which blood is ejected from the heart. Therefore, as the heart rate increases, cardiac output tends to increase. As the heart rate increases, the time spent in diastole is reduced, and there is less time for the ventricles to fill. At a heart rate of 75 beats/minute, one cardiac cycle lasts 0.8 second, of which approximately 0.3 second is spent in systole and approximately 0.5 second in diastole.

Heart beats As the heart rate increases, the time spent in systole remains approximately the same, whereas that spent in diastole decreases. This leads to a decrease in stroke volume and, at high heart rates, a decrease in cardiac output. One of the dangers of ventricular tachycardia is a reduction in cardiac output because the heart does not have time to fill adequately.

Abnormal Heart beats hhjhttnjngh Tachycardia Heart rate that exceeds the normal range. A resting heart rate over 100 beats per minute is generally accepted as tachycardia. Bradycardia Heart rate that is under the normal range. the resting heart rate of under 60 beats per minute is generally accepted as bradycardia.

Cardiac output The efficiency of the heart as a pump often is measured in terms of cardiac output or the amount of blood the heart pumps each minute Cardiac output is the blood flow generated by the heart per minute. The cardiac output is equal to: ** the volume of blood pumped by one ventricle per beat (stroke volume) times the number of beats per minute (Heart Rate) CO = SV . HR

Cardiac output The stroke volume for each ventricle averages 70 ml of blood, and a normal heart rate is approximately 70-75 beats/minute; therefore, the cardiac output at rest is ~ 5 L/min. The heart rate is under neural control. Cardiac sympathetic activity increases the heart rate, whereas parasympathetic impulses decreases heart rate.

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