The Heart A-Chapter Identify the layers of the heart wall and state the type of tissue in each layer.

Transcription

1 Objectives: The Heart AChapter Identify the layers of the heart wall and state the type of tissue in each layer. Label a diagram of the heart, identifying the chambers, valves, and associated vessels. 3. Trace the pathway of blood flow through the heart, including chambers, valves, and pulmonary circulation. 4. Identify the major vessels that supply blood to the myocardium and return the deoxygenated blood to the right atrium. 5. Describe the components and function of the conduction system of the heart. 6. Summarize the events of a complete cardiac cycle and correlate the heart sounds heard with a stethoscope with these events. 7. Explain what is meant by cardiac output and describe the factors that affect these values. I. Introduction A. Importance of the heart 1. Pump which supplies blood to all cells/tissues 3. Normal adult B. Relationships with other systems. P. 224 II. Overview of the heart A. Form, size & location of the heart 1. Position & importance thoracic cavity/middle mediastinal region CPR, ECG s

2 d. Posterior to sternum, anterior to spinal column 2 3. Apex=tip, pointed end of the heart Direction of apex is inferior, anteriorly and to the left 4. Base ~superiorly, posteriorly & to the right 5. Size of the heart is size of a closed fist B. Coverings of the heart 1. Pericardium surrounds heart & proximal vessels visceral pericardium fibrous d. parietal pericardium serous e. f. Pericardial cavity is filled with fluid. This reduces friction between the membranes Pericarditisinflammation of the pericardium. This disrupts the heart contractions. III. Structure of the heart A. Layers of the heart wall (3 layers) fig thin, protective layer firmly attached to middle layer location of blood vessels which nourish the heart wall MYOCARDIUM (middle layer of heart) thick layer made of cardiac muscle tissue d. tissue/cells are connected & communicate they lay at different angles & Form the force to pump the blood 3. ENDOCARDIUM (inner layer of heart) smooth surface allows blood forms valves of the heart

3 RA LA LUNGS RV LV AORTA B. Chambers of the heart fig. 13 (4 chambers) 1. Atria/Atriums (2right, left) thin walledonly pumps to lower chambers of the heart vena cava s (superior/inferior) coronary sinus return deoxygenated blood from heart muscle to Right atrium holding chamber d. e. Left atrium high O2, low CO2 receives blood from 4 pulmonary veins returning to the heart from the lungs (oxygenated) ~Pumping chambers ~Both ventricles hold same amount of Blood Right ventricle receives blood from RA and pumps blood to the lungs and back blood low in O2, high in CO2 receives blood from LA and pumps blood to the entire body very thick myocardium C. Valves of the heart fig. 14,15 1. to keep blood in a chamber to keep blood flowing in one direction long cords inside control the opening valves between atrium & ventricles closes to prevent backflow into atrium when ventricles contracting

4 3. d. Left AV valve=bicuspid valve located at base of large vessels where blood leaves the heart Right side blood leaves RV & enters aorta going to the body ~disease may damage heart valves & they won t work properly ~backflow of blood may occur ~valvular stenosis=valves become stiff & won t fully open E. Pathway of blood through the heart fig Remember~ both atriums contract at the same time (squeeze together) both ventricles contract at the same time heart functions as 2 separate pumps Right side Left side Pulmonary circulation heartlungheart Systemic circulationheartbodyheart deoxygenated blood enters the RA from the inferior/superior vena cava atriums contract pushing blood through the AV valve and to the RV ventricles contract pushing blood through semilunar valves into pulmonary arteries blood travels to the lung in the pulmonary arteries where gases are exchanged. CO2O2 Blood returns to heart by way of the pulmonary veins & enters the LA LA contracts pushing blood through the AV valve and into the LV

5 Ventricles contract pushing blood through semilunar valves into the aort F. 1. Myocardium needs a constant supply of O2/nutrients heart muscle CANNOT build up O2 debt like skeletal muscle heart has extensive network of blood vessels to serve the heart itself coronary arteries anterior interventricular artery 3. Greatest flow when heart contracting Angina pectoris=chest pain due to demand for O2 greater than you have. Nitroglycerin tablets dilates vessels to release pressure MI (myocardial infarction) heart attack blockage of coronary causes death of heart tissue enzymes are released when heart muscle is damaged. You can tell if you ve had a mild heart attack by reading enzyme levels 4. Cardiac veins returns deoxygenated blood to the right atrium Read p. 230 Pioneers of Anatomy & Physiology Werner Forssmann IV. A. Conduction Systemintro 1. Heart must be synchronized & act as one (cells connected by channels for communication) Contraction of chambers by cardiac muscle cells of the conduction system 3. B. Components of the conduction system fig posterior wall of RA near entrance to the S. Vena cava

6 PACEMAKER of the heart d. cause BOTH atria to contract together e. impulse initiates second part of system Atrioventricular node (AV node) dub sound impulse travels slower than SA allows time for atria to finish contracting When cells contract out of the pattern, it is called an arrhythmi It can lead to tachycardia (heart racing) and then death. 3. Impulses conducted through the heart produce electrical currents which can be measured on the surface of the body C. Cardiac Cycle fig Definedalternating contraction & relaxation of the myocardial walls coordinated by the conduction system during one heartbeat Systole 3. Diastolewhen the heart relaxes 4. D. Heart sounds 1. one hears the closing of heart valve when listening with a stethoscope Lubdub sound 3. E. Cardiac output 1. Definedthe volume of blood pumped through a ventricle in 1 minute cardiac output=volume x heart rate Ex. 70 ml/beat x 72 beats/min = 5040 ml/min 3. The heart recycles all your blood in 1 minute! 4. Cardiac output changes with amount of activity

7 5. Heart rate changes in heart rate controlled by medulla oblongata of the brain affected by oxygen needs depression CO2 concentrations