Chapter 22 Heart

Why have a heart? Move nutrients and oxygen through the body.

How does the heart do its job? First, get oxygen into the blood Second, get oxygenated blood to the rest of the body

Location of heart Slightly left of center, posterior to sternum Fig. 22.2 Location of heart Slightly left of center, posterior to sternum Rotated; right border sits anterior to left border Base of heart is posterior and superior formed by left atrium Superior border formed by ascending aorta, pulmonary trunk, superior vena cava Conical bottom end is apex Inferior border formed by right ventricle Superior border 2nd rib Right border Left border Sternum Diaphragm Inferior border (a) Borders of the heart

Location of heart From anterior view, right ventricle is most obvious Fig. 22.2 Trachea Location of heart Right lung Left lung From anterior view, right ventricle is most obvious Left ventricle sits behind Aortic arch Superior vena cava Pulmonary trunk Ascending aorta Right atrium Left ventricle Right ventricle (b) Heart and lungs, anterior view

Blood flow Fig. 22.6 Blood flows into the heart from the superior vena cava and the inferior vena cava Superior vena cava carries blood from head, neck, arms, superior trunk Inferior vena cava carries blood from lower limbs, inferior trunk This blood is high in CO2 and low in O2 Superior vena cava Pulmonary artery Right atrium Opening for inferior vena cava Right ventricle Inferior vena cava

Blood first enters the right atrium, then the right ventricle Fig. 22.6 Blood first enters the right atrium, then the right ventricle The right ventricle pumps blood out the pulmonary arteries to the lungs In the lungs, the blood exchanges CO2 for O2 Superior vena cava Pulmonary artery Pulmonary artery Pulmonary trunk Right atrium Opening for inferior vena cava Right ventricle Inferior vena cava

Flow and gas exchange in lungs is called pulmonary circulation Fig. 22.1 Systemic circulation 4 Flow and gas exchange in lungs is called pulmonary circulation Lung Lung Basic pattern of blood flow 2 2 Pulmonary circulation 1 Right side of heart Right side Right side 1 3 2 Lungs Pulmonary circulation Oxygenated blood Left side Left side 3 Left side of heart Deoxygenated blood Heart Gas exchange 4 Systemic cells 4 Systemic circulation

Fig. 22.5b Heart, Posterior View Blood returns to the heart through the pulmonary veins The pulmonary veins empty into the left atrium Fig. 22.5b Heart, Posterior View Left pulmonary artery Right pulmonary artery Left pulmonary veins Right pulmonary veins Left atrium Right atrium Left ventricle Right ventricle

The left atrium pumps blood into the left ventricle The left ventricle pumps blood out the aorta to the body Fig. 22.6 Aortic arch Ascending aorta Descending aorta Left atrium Right atrium Left ventricle Right ventricle

Fig. 22.6 Form and Function What differences do you notice between the atria and the ventricles? What’s different between the right and left ventricle? Left atrium Right atrium Left ventricle Right ventricle

Form and Function Atria do not make powerful contractions Fig. 22.6 Atria do not make powerful contractions Left ventricle makes more powerful contractions than right ventricle How does the body ensure blood flows in only one direction? Left atrium Right atrium Left ventricle Right ventricle Copyright © McGraw-Hill Education. Permission required for reproduction or display.

Valves Both atria fill at the same time, contract at the same time Contraction of atria forces open valves between atria and ventricles Right atrioventricular valve (AKA tricuspid valve) separates right atrium from right ventricle Left atrioventricular valve (AKA bicuspid valve) separates left atrium from left ventricle

Valves Fig. 22.7 Right atrioventricular valve (AKA tricuspid valve) separates right atrium from right ventricle Left atrioventricular valve (AKA bicuspid valve) separates left atrium from left ventricle Posterior Left atrioventricular valve Right atrioventricular valve Aortic semilunar valve Fibrous skeleton Pulmonary semilunar valve Anterior

Valves Left atrium Atrioventricular valves are attached to inside of ventricles by chordae tendineae attached to papillary muscles inside ventricle prevents inversion of valve flaps when ventricle contracts typically 3 papillary muscles in right ventricle, 2 in left ventricle Left A/V valve Right A/V valve Chordae tendineae Papillary muscles

Valves Contraction of ventricles forces atrioventricular valves closed and opens semilunar valves

Valves Fig. 22.7 Pulmonary semilunar valve separates right ventricle from pulmonary trunk Aortic semilunar valve separates left ventricle from aorta As ventricles relax, semilunar valves close Posterior Left atrioventricular valve Right atrioventricular valve Aortic semilunar valve Fibrous skeleton Pulmonary semilunar valve Anterior

Valves Semilunar valves don’t have chordae tendineae Left A/V valve Pulmonary semilunar valve Semilunar valves don’t have chordae tendineae Cupped structure of valve fills with blood as ventricles contract, pushing valve back into place Aortic semilunar valve Right A/V valve Chordae tendineae Papillary muscles

Copyright © McGraw-Hill Education Copyright © McGraw-Hill Education. Permission required for reproduction or display. (a) Ventricular Systole (Contraction)

Copyright © McGraw-Hill Education Copyright © McGraw-Hill Education. Permission required for reproduction or display. (b) Ventricular Diastole (Relaxation)

Sounds of a heartbeat Lub-dub, lub-dub, lub-dub “lub” is sound of atrioventricular valves closing “dub” is sound of semilunar valves closing Sounds are not heard best in exact spot of valve Pulmonary semilunar valve Aortic semilunar valve Left atrioventricular valve Right atrioventricular valve Actual location of heart valve Area where valve sound is best heard Locations of individual heart valves and the ideal listening sites for each valve are shown.

Walls of heart chambers Wall between atria is interatrial septum Wall between ventricles is interventricular septum Interatrial septum Interventricular septum

Pericardium Heart sits inside pericardium fibrous sac – very tough Fig. 22.2 Pericardium Mediastinum Left lung Heart sits inside pericardium fibrous sac – very tough serous lining made of two layers of epithelial tissue with tiny amount of water between Ascending aorta Pleura (cut) Pericardium (cut) Apex of heart Diaphragm (cut) (c) Serous membranes of the heart and lungs

Pericardium Restricts heart movement, prevents bouncing Fig. 22.2 Pericardium Posterior Restricts heart movement, prevents bouncing Prevents heart overfilling with blood Thoracic vertebra Right lung Left lung Aortic arch (cut) Heart Sternum Anterior (d) Cross-sectional view

Pericardium Outer layer is fibrous pericardium Fibrous pericardium Fig. 22.3 Pericardium Fibrous pericardium Outer layer is fibrous pericardium dense connective tissue attached to diaphragm and base of aorta, pulmonary trunk, vena cava Parietal layer of serous pericardium Pericardial cavity Visceral layer of serous pericardium (epicardium) Fibrous pericardium Parietal layer of serous pericardium Pericardial cavity

Pericardium Inner layer is serous pericardium Fibrous pericardium Fig. 22.3 Pericardium Inner layer is serous pericardium double layer formed from single “balloon” stretched around heart parietal layer connected to fibrous pericardium pericardial cavity contains serous fluid secreted by serous membranes visceral layer covers outside of heart (AKA epicardium) Fibrous pericardium Parietal layer of serous pericardium Pericardial cavity Visceral layer of serous pericardium (epicardium) Fibrous pericardium Parietal layer of serous pericardium Pericardial cavity

Pericarditis Inflammation of pericardium makes blood vessels leaky Fig. 22.3 Pericarditis Inflammation of pericardium makes blood vessels leaky Fluid accumulates in pericardial cavity prevents heart from pumping fully

External anatomy of heart Fig. 22.5a External anatomy of heart Coronary arteries supply blood to heart muscle Coronary veins return blood from heart tissue back to right atrium Blood enters atrium through coronary sinus Left coronary artery (in coronary sulcus) Circumflex artery (in coronary sulcus) Right coronary artery (in coronary sulcus)

transverse (T) tubules Fig. 22.10 Openings of transverse (T) tubules Intercalated disc Cardiac muscle Folded sarcolemma fibers are striated intercalated discs have desmosomes and gap junctions link cells electrically and mechanically impulses sent immediately form one cell to next Desmosomes Intercalated discs Gap junctions Endomysium Sarcolemma Cross section of cardiac muscle cells Nucleus (b) Intercellular junctions Mitochondrion

Fig. 22.11 1. Muscle impulse is generated at the sinoatrial node. It spreads throughout the atria and to the atrioventricular node by the internodal pathway. Sinoatrial node (pacemaker) Internodal pathway Atrioventricular node Atrioventricular bundle (bundle of His) Purkinje fibers Left bundles Purkinje fibers Right bundle Heart is autorhythmic starts its own beating Specialized cells that initiate and conduct muscle impulses are collectively the conducting system

2. Atrioventricular node cells delay the Fig. 22.11 Sinoatrial node (pacemaker) Internodal pathway Atrioventricular node Atrioventricular node Atrioventricular bundle 2. Atrioventricular node cells delay the muscle impulse as it passes to the atrioventricular bundle (Bundle of His).

Fig. 22.11 Sinoatrial node (pacemaker) Internodal pathway Atrioventricular node Atrioventricular node Atrioventricular bundle 3. The atrioventricular bundle (bundle of His) conducts the muscle impulse into the interventricular septum. Atrioventricular bundle Interventricular septum

Fig. 22.11 4. Within the interventricular septum, the left and right bundles split from the atrioventricular bundle. Atrioventricular bundle Interventricular septum Left and right bundles

Fig. 22.11 5. The muscle impulse is delivered to Purkinje fibers in each ventricle and distributed throughout the ventricular myocardium. Atrioventricular bundle Interventricular septum Left and right bundles Purkinje fibers

Fig. 22.11 Superior vena cava Right atrium Left atrium Sinoatrial node (pacemaker) Internodal pathway Internodal pathway Atrioventricular node Atrioventricular node Atrioventricular bundle (bundle of His) Interventricular septum Atrioventricular bundle Right bundle Purkinje fibers Left bundles Purkinje fibers 1 Muscle impulse is generated at the sinoatrial node. It spreads throughout the atria and to the atrioventricular node by the internodal pathway. 2 Atrioventricular node cells delay the muscle impulse as it passes to the atrioventricular bundle. Atrioventricular bundle Interventricular septum Left and right bundles Purkinje fibers 3 The atrioventricular bundle (bundle of His) conducts the muscle impulse into the interventricular septum. 4 Within the interventricular septum, the left and right bundles split from the atrioventricular bundle. 5 The muscle impulse is delivered to Purkinje fibers in each ventricle and distributed throughout the ventricular myocardium.

R P wave T wave Q S QRS complex 1 2 3 0.8 second +1 Millivolts –1 1 2 3 T wave P wave QRS complex The events of a single cardiac cycle as recorded on an electrocardiogram.

Ventricular systole Contraction of ventricles Semilunar valves open Fig. 22.13a Copyright © McGraw-Hill Education. Permission required for reproduction or display. (a) Ventricular Systole (Contraction) Ventricular systole Aortic arch Blood flow into ascending aorta Ascending aorta Pulmonary trunk Contraction of ventricles Semilunar valves open Blood flows into arteries Larger of blood pressure measurements Blood flow into right atrium Blood flow into pulmonary trunk Right atrium Left atrium Ventricular contraction pushes blood against the open AV valves, causing them to close. Contracting papillary muscles and the chordae tendineae prevent valve flaps from everting into atria. Ventricles contract, forcing semilunar valves to open and blood to enter the pulmonary trunk and the ascending aorta. Atrioventricular valves closed Semilunar valves open Right ventricle Left ventricle Cusp of atrioventricular valve Cusp of semilunar valve Blood in ventricle Posterior Left AV valve (closed) Right AV valve (closed) Left ventricle Right ventricle Aortic semilunar valve (open) Pulmonary semilunar valve (open) Anterior Transverse section

Ventricular diastole Relaxation of ventricles AV valves open Copyright © McGraw-Hill Education. Permission required for reproduction or display. Fig. 22.13b (b) Ventricular Diastole (Relaxation) Ventricular diastole Aortic arch Blood flow into right atrium Blood flow into left ventricle Relaxation of ventricles AV valves open Blood flows into ventricles from atria Smaller of blood pressure measurements Right atrium Left atrium During ventricular relaxation, some blood in the ascending aorta and pulmonary trunk flows back toward the ventricles, filling the semilunar valve cusps and forcing them to close. Blood flow into right ventricle Ventricles relax and fill with blood both passively and then by atrial contraction as AV valves remain open. Atrioventricular valves open Semilunar valves closed Right ventricle Left ventricle Atrium Cusp of atrioventricular valve Blood Cusps of semilunar valve Chordae tendineae Papillary muscle Posterior Left AV valve (open) Right AV valve (open) Left ventricle Right ventricle Aortic semilunar valve (closed) Pulmonary semilunar valve (closed) Anterior Transverse section

Fetal Circulation Where does oxygen come from? Where does blood get filtered? Where do nutrients come from? Different needs of fetal circulation: Transport blood to and from placenta Return blood to fetal circulatory system Bypass developing liver and lungs

Umbilical Cord Deoxygenated blood travels to placenta through umbilical arteries Oxygenated blood arrives from placenta through umbilical vein Maternal and fetal blood do not mix

Bypassing the Liver Umbilical vein splits near liver ~2/3 blood travels to developing liver through hepatic portal vein Ductus venosus carries ~1/3 of blood to inferior vena cava

Bypassing the Lungs Blood flows into right atrium Foramen ovale is hole between right and left atria Most blood flows through foramen ovale A small amount flows into right ventricle and through pulmonary trunk

Bypassing the Lungs Ductus arteriosus is connection between pulmonary artery and aorta Most blood in pulmonary artery goes through ductus arteriosus, bypassing pulmonary circuit

Fetal Cardiovascular Structure Postnatal Structure Ductus arteriosus Ligamentum arteriosum Ductus venosus Ligamentum venosum Foramen ovale Fossa ovalis Umbilical arteries Medial umbilical ligaments Umbilical vein Round ligament of liver (ligamentum teres)