Cardiovascular II: Conduction, Histology, and Development PDF

Cardiovascular II: Conduction, Histology, and Development Course Learning Objectives: Cardiovascular: Recall the networks that allow for the exchange of gases and nutrients throughout the body by tracing blood flow and identifying related structures in the cardi...

Cardiovascular II: Conduction, Histology, and Development Course Learning Objectives: Cardiovascular: Recall the networks that allow for the exchange of gases and nutrients throughout the body by tracing blood flow and identifying related structures in the cardiovascular system  Lecture Learning Objectives 1. Trace the heart’s conducting system, 6. Visually identify the histological identifying and ordering structures and structures and layers in cardiac fibers that impulses travel through 2. Identify and describe the events in the muscle cardiac cycle, focusing on the structures 7. Describe the following major involved in diastole, systole, lub, and dub events of heart development 3. Recall the anatomical location to Formation of heart tube auscultate each chamber of the heart Cardiac wall layers 4. Describe the autonomic innervation of Folding the heart, including its origins and structures Heart partitioning 5. Describe how referred pain from the Valve development heart impacts dermatomes in the upper limb 8. Trace primordial heart circulation  Heart Conduction 1. Review associated heart structures 2. Learn nervous structures associated with heart conduction and the order they are excited 3. Bring it together  LO 1 Cardiac Conduction System 1 Sinoatrial node Coordinates contraction of atrial and ventricular musculature that allows for 2 unidirectional excitation/contraction Nodes and networks of specialized 3 cardiac muscle cells 1. Sinoatrial node (SA)- at crista 3 terminalis (SVC and r. atrium) 2. Atrioventricular node (AV)- at opening of coronary sinus 3. Atrioventricular bundle -> left and 4 right bundle branches 4 4. Subendocardial plexus, formed by Purkinje fibers, to papillary muscles and ventricular walls Grant’s Atlas of Anatomy, Ager and Dalley (2013)  LO 1 Cardiac Conduction System Coordinates contraction of atrial and ventricular musculature that allows for unidirectional excitation/contraction Nodes and networks of specialized cardiac muscle cells 1. Sinoatrial node (SA)- at crista terminalis (SVC and r. atrium) 2. Atrioventricular node (AV)- at opening of coronary sinus 3. Atrioventricular bundle -> left and right bundle branches 4. Subendocardial plexus (branching nerves deep to endocardium), formed by Purkinje fibers, to papillary muscles and ventricular walls  Pumping of the Heart Two synchronized pumps Cardiac cycle: synchronous pumping action of the heart’s two atrioventricular (AV) pumps Right side of the heart sends blood to? Left side of the heart? Wikipedia  LO 2 Pumping of the Heart Diastole- filling of ventricles Systole- shortening and emptying of the ventricle Muscle relaxes Blood flows from atria into Muscle contracts ventricles via AV valves, mostly Blood flows into great due to passive blood flow vessels from ventricles via semilunar valves Blood travels due to difference Blood travels in one direction in chamber pressure due to difference in chamber pressure Unless otherwise stated, diastole and systole refer to ventricular movements. Gray’s Basic Anatomy, Drake et al., 2018  LO 2 Lub- Dub: Heart Sounds-Created by closing of valves Lub- Closing of AV valves at beginning Dub- Closing of semilunar valves at of systole beginning of diastole DUB LUB Gray’s Basic Anatomy, Drake et al., 2018  LO 3 Auscultation of the Heart: Where to Listen for Heart Sounds To listen for valve sounds, place stethoscope downstream from the blood flow of the valve Right atrioventricular/Tricuspid: just left of the lower part of the sternum near the 5th intercostal space Left atrioventricular/Bicuspid (mitral): over the apex of the heart in the left 5th intercostal space at the mid clavicular line Pulmonary semilunar: over the medial end of the left 2nd intercostal space Aortic semilunar: over the medial end of the right 2nd intercostal space Gray’s Basic Anatomy, Drake et al., 2018 Innervation of the Heart  Autonomic Innervation to the Sympathetic contributions Heart Parasympathetic contributions  LO 4 Cardiac Innervation- Visceral Sensory (Afferent) Chemoreceptors and baroreceptors Convey information related to blood pressure and composition of blood to CNS Vagus nerve (CNX)- sensory from aorta Glossopharyngeal nerve (CN IX)- sensory from carotid body Visceral pain carried by sympathetic or parasympathetic? First Aid for Basic Science: Organ Systems, Le et al., 2017  LO 4 Cardiac Innervation- Visceral Motor (Efferent) Autonomic nervous system Sym Para regulates Heart rate Heart rate Force of contraction Force of contraction Cardiac output Cardiac output Sympathetic Fibers travel through cervical and thoracic (T1-T5) portions of sympathetic trunk Parasympathetic Involve nucleus ambiguus Fibers travel with Vagus nerve (CN X) Allow for cardiac reflexes (efferent) due to autonomic sensory input First Aid for Basic Science: Organ Systems, Le et al., 2017  LO 4 Cardiac Innervation- Visceral Efferent Cardiac plexus- formed form parasympathetic (CN X) and sympathetic fibers (cardiopulmonary splanchnic nerves) Deep cardiac plexus- anterior to trachea Superficial cardiac plexus- anterior to aorta Gray’s Basic Anatomy, Drake et al., 2018 LO 4  LO 5 Clinical Application: Referred Pain Impulses from certain viscera are perceived by the cerebral cortex as originating from skin dermatomes “The basis for referred Cutaneous and visceral sensory neurons often pain may be convergence ascend through the same tract in spinal cord of somatic and visceral pain fibers on the same Sensory cortex is unable to differentiate second-order neurons in between the source of the stimulus the dorsal horn of the spinal cord that project higher brain regions.” Clinically Oriented Anatomy, Moore et al., 2018  LO 5 Clinical Application: Referred Pain Cardiac Histology  LO 6 Cardiac Muscle Histology Striated Branching Large round nuclei Intercalated discs  LO 6 Cardiac Muscle Histology Cardiac muscle 1. Branching fibers 2. Intercalated 1 discs 3 3. Nucleus of 2 cardiomyocytes  LO 6 Cardiac Muscle Histology 1 3 Cardiac muscle 2 1. Branching fibers 2. Intercalated discs 5 3. Nucleus of cardiomyocytes 4. Myofibril 4 5. Cross striations  LO 6 Cardiac Muscle Histology Cross section 1 Cardiac muscle 1. Nucleus of cardiomyocytes  Cardiac LO 6 Muscle Histology 1. Epicardium CT, adipocytes, nerves and vessels 2. Myocardium Cardiac muscle, CT, small vessels Cardiac muscle fibers 3. Endocardium CT lined with endothelium (simple squamous) Heart Embryology  (A) A representation of a saggital section through the unfolded embryo at the beginning of the fourth week. The cardiogenic mesoderm lies cephalad to the (B) The box in A is expanded to oropharyngeal membrane with the septum show the detail. Note that the transversum lying further cephalad again. pericardial cavity at this stage is dorsal to the heart tube. Note also the close proximity of the endoderm of the foregut. https://thoracickey.com/chapter-3-development-of-the-heart/  (C) With the marked expansion of the neural plate the heart moves ventrally and caudad. https://thoracickey.com/chapter-3-development-of-the-heart/  (D) With further growth of the neural tissue the amniotic cavity extends further ventrally and caudally, and the developing heart now comes to lie caudad to the oropharyngeal membrane with the pericardial cavity ventrally. With lateral folding of the embryo the foregut develops, and the stalk of the yolk sac is constricted. The septum transversum in which the liver will develop now lies ventral and caudad to the heart. https://thoracickey.com/chapter-3-development-of-the-heart/  (E) Further folding brings the heart to its final position. https://thoracickey.com/chapter-3-development-of-the-heart/  LO 7 Major Events of Heart Development A. Formation of heart tube D. Folding of heart tube B. Differentiation and formation of E. Partitioning of primordial heart cardiac layers (atrium/ventricle, atria, ventricle, aorta/pulmonary trunk) C. Change in heart tube shape- dilations and constrictions F. Development of cardiac valves First Aid for Basic Science: Organ Systems, Le et al., 2017 https://thoracickey.com/ca LO 7 rdiac-development/ https://www.youtube.com/watch?v=a0qyagIgBPw  LO 7 Formation of the Heart Tube Formed from mesoderm and neural crest cells Two tubes are formed form mesoderm (A-B) Fuse to form a single heart tube late in 3rd week (B-C) Held within a space, the pericardial cavity Further formation of the heart occurs from induction form anterior endoderm Before We are Born, Moore et al., 2019  LO 7 Formation and Differentiation of Cardiac Layers Wall of the heart tube Endothelial tube- internal lining of heart tube that forms endocardium Cardiac jelly- gelatinous-matrix CT separating primordial myocardium from internal developing heart Primordial myocardium- the external layer of the heart tube Epicardium- mesothelial cells that spread over myocardium Before We are Born, Moore et al., 2019  LO 8 Change in Heart Tube Shape Before We are Born, Moore et al., 2019 Heart tube will develop dilations and constrictions Truncus arteriosus Bulbus cordis Primordial ventricle Primordial atrium Sinus venosus First Aid for Basic Science: Organ Systems, Le et al., 2017  LO 7 Folding of Heart Tube Heart tube will grow and elongate through mitosis of cardiomyocytes forming a venous and arterial end Tube will begin to fold ventrally due to faster growth of some structures (bulbus cordis and ventricle) Venous and arterial ends will be positioned close together posteriorly Before We are Born, Moore et al., 2019  LO 8 Primordial Heart Circulation 1. Blood enters sinus venosus How does blood enter the heart? from three locations Embryo (common cardinal veins) Placenta (umbilical veins) Umbilical vesicle (vitelline veins) 2. Sinoatrial valve 3 3. Primordial atrium 2 4. Atrioventricular canal 1 7 5. Primordial ventricle 6 4 6. Bulbus cordis 7. Truncus arteriosus 5 Before We are Born, Moore et al., 2019  LO 8 Primordial Heart Circulation Truncus arteriosus sends blood to 1. Aortic sac 2. Pharyngeal arch arteries Embryo (dorsal aorta) Umbilical vesicle (vitelline arteries) Placenta (umbilical arteries) Before We are Born, Moore et al., 2019  LO 7 Partitioning of Primordial Atrium from Ventricle Weeks 4-8 (organogenesis) In atrioventricular canal: endocardial cushions grow from walls fuse to separate atria and ventricles: Form right and left atrioventricular canals → what will form here? Cushions formed from specialized mesoderm and neural crest cells (will go on to help form AV valves) Atlas of Fetal Echocariography, Shah and Pandya, 2011  LO 7 Partitioning of Primordial Atrium and Formation of Foramen Ovale 1. Septum primum and foramen primum form Shunts oxygenated blood from right to left atria, mostly bypassing ventricles; will degenerate 2. Foramen secundum forms via apoptosis 3. Septum secundum forms from outgrowth; septum primum remains inferiorly only 4. Septa primum and secundum overlap to form one way valve → foramen ovale (was foramen secundum) 5. Superior portion of septum primum degenerates completely First Aid for Basic Science: Organ Systems, Le et al., 2017  LO 7 Partitioning of Primordial Ventricle 1. Muscular interventricular septum grows from floor of primordial ventricle near apex; creates interventricular foramen Trabeculae carneae, papillary First Aid for Basic Science: Organ Systems, Le et al., 2017 muscles, and chordea tendineae (membranous part) form from outgrowths in ventricular wall 2. Aorticopulmonary septum forms in bulbus cordis and truncus arteriosus 3. Fuses inferiorly with muscular ventricular septum to close interventricular foramen Before We are Born, Moore et al., 2019  LO 7 https://www.youtube.com/watch?v=a0qyagIgBPw  LO 7 Formation of the Aorta and Pulmonary Trunks Formed from portioning of bulbus cordis and truncus arteriosus Ridges of tissue form and Left Ventricle grow, spiraling 180 Right Ventricle degrees Forms aorticopulmonary septum between aorta and pulmonary trunk  LO 7 Formation of the Aorta and Pulmonary Trunks Formed from portioning of bulbus cordis and truncus arteriosus Ridges of tissue form and grow, spiraling 180 degrees Forms aorticopulmonary septum between aorta and pulmonary trunk Before We are Born, Moore et al., 2019  LO 7 Cardiac Valve Formation Semilunar Form from swellings of tissue and contributions form neural crest cells around orifice of aorta and pulmonary trunk Atrioventricular Proliferation of tissue around atrioventricular canals Before We are Born, Moore et al., 2019