1. THE HEART Ch 19 Human Anatomy Sonya Schuh-Huerta, Ph.D. Leonardo Da Vinci, Human Heart

2. The Heart: An Amazing Piece of Machinery Although it’s not where you keep your emotions, it’s an amazing vital organ of your body

3. The Heart A muscular double pump –Pulmonary circuit  takes blood to & from the lungs –Systemic circuit  vessels transport blood to & from body tissues –Atria  receive blood from the pulmonary & systemic circuits –Ventricles  the muscular pumping chambers of the heart

4. The Pulmonary & Systemic Circuits Oxygen-rich, CO 2 -poor blood Oxygen-poor, CO 2 -rich blood Capillary beds of lungs where gas exchange occurs Capillary beds of all body tissues where gas exchange occurs Pulmonary veins Pulmonary arteries Pulmonary Circuit Systemic Circuit Aorta and branches Left atrium Heart Left ventricle Right atrium Right ventricle Venae cavae

5. Location & Orientation Within the Thorax Heart  typically weighs 250–350 grams (~healthy heart) Largest organ of the mediastinum –Located between the lungs –Apex lies to the left of the midline –Base is the broad posterior surface

6. (c) Superior vena cava Left lung Aorta Parietal pleura (cut) Pericardium (cut) Pulmonary trunk Diaphragm Apex of heart Location of the Heart in the Thorax Heart Posterior Right lung (b) Mediastinum Pericardium (cut) Fat in epicardium Rib 5 Left lung Aorta Mediastinum Apex of heart (d) Right auricle of right atrium Superior vena cava Right ventricle Diaphragm (a) Rib 2 Midsternal line

7. Structure of the Heart – Coverings Pericardium – 2 primary layers –Fibrous pericardium Strong layer of dense connective tissue –Serous pericardium Formed from 2 layers –Parietal layer of the serous pericardium –Visceral layer of the serous pericardium (= epicardium)

8. Layers of the Pericardium & of the Heart Wall Fibrous pericardium Parietal layer of serous pericardium Pericardial cavity Epicardium (visceral layer of serous pericardium) Myocardium Endocardium Pulmonary trunk Heart chamber Heart wall Pericardium Myocardium

9. Structure of the Heart – Layers of the Heart Wall Epicardium –Visceral layer of the serous pericardium Myocardium –Consists of cardiac muscle – all the muscle of the heart –Muscle arranged in circular & spiral patterns Endocardium –Endothelium resting on a layer of connective tissue –Lines the internal walls of the heart

10. Circular & Spiral Arrangements of Cardiac Muscle Bundles Cardiac muscle bundles

11. Heart Chambers Right & left atria –Superior chambers Right & left ventricles –Inferior chambers Internal divisions –Interventricular septa –Interatrial septa External markings –Coronary sulcus –Anterior interventricular sulcus –Posterior interventricular sulcus

12. Gross Anatomy of the Heart Left common carotid artery Left subclavian artery Aortic arch Ligamentum arteriosum Left pulmonary artery Left pulmonary veins Auricle of left atrium Circumflex artery Left coronary artery (in coronary sulcus) Left ventricle Great cardiac vein Anterior interventricular artery (in anterior interventricular sulcus) Apex Brachiocephalic trunk Superior vena cava Right pulmonary artery Ascending aorta Pulmonary trunk Right pulmonary veins Right atrium Right coronary artery (in coronary sulcus) Anterior cardiac vein Right ventricle Right marginal artery Small cardiac vein Inferior vena cava

13. Inferior View of the Heart (d) Inferior view; surface shown rests on the diaphragm (base of heart). Aorta Left pulmonary artery Left pulmonary veins Auricle of left atrium Left atrium Great cardiac vein Posterior vein of left ventricle Left ventricle Apex Superior vena cava Right pulmonary artery Right pulmonary veins Right atrium Inferior vena cava Right coronary artery (in coronary sulcus) Coronary sinus Posterior interventricular artery (in posterior interventricular sulcus) Middle cardiac vein Right ventricle

14. Right Atrium Forms right border of heart Receives blood from systemic circuit Pectinate muscles –Ridges inside anterior of right atrium Crista terminalis –Landmark used to locate veins entering right atrium Fossa ovalis –Depression in interatrial septum Remnant of foramen ovale (from embryonic developmt)

15. Right Ventricle Receives blood from right atrium through the tricuspid valve Pumps blood into pulmonary circuit via –Pulmonary trunk Internal walls of right ventricle –Trabeculae carneae –Papillary muscles –Chordae tendineae Pulmonary semilunar valve –Located at opening of right ventricle & pulmonary trunk

16. Heart Chambers Aorta Left pulmonary artery Left atrium Left pulmonary veins Mitral (bicuspid) valve Aortic valve Pulmonary (semilunar) valve Left ventricle Papillary muscle Interventricular septum Epicardium Myocardium Endocardium (e) Frontal section Superior vena cava Right pulmonary artery Pulmonary trunk Right atrium Right pulmonary veins Fossa ovalis Pectinate muscles Tricuspid valve Right ventricle Chordae tendineae Trabeculae carneae Inferior vena cava

17. Left Atrium Makes up heart’s posterior surface Receives oxygen-rich blood from lungs through pulmonary veins Opens into the left ventricle through: –Mitral valve (= bicuspid; left atrioventricular valve)

18. Left Ventricle Forms apex of the heart Very thick strong muscle Internal walls of left ventricle –Trabeculae carneae –Papillary muscles –Chordae tendineae Pumps blood to systemic circuit via –Aortic semilunar valve (= aortic valve)

19. Heart Valves Each valve composed of –Endocardium with connective tissue core Atrioventricular (AV) valves –Between atria & ventricles  tricuspid & bicuspid Aortic & pulmonary valves –At junction of ventricles & great arteries  pulmonary & aortic semilunar

20. Heart Chambers & Valves Aorta Left pulmonary artery Left atrium Left pulmonary veins Mitral (bicuspid) valve Aortic (semilunar) valve Pulmonary (semilunar) valve Left ventricle Papillary muscle Interventricular septum Epicardium Myocardium Endocardium (e) Frontal section Superior vena cava Right pulmonary artery Pulmonary trunk Right atrium Right pulmonary veins Fossa ovalis Pectinate muscles Tricuspid valve Right ventricle Chordae tendineae Trabeculae carneae Inferior vena cava

21. Fibrous Skeleton Surrounds all 4 valves –Composed of dense connective tissue Functions: –Anchors valve cusps –Prevents overdilation of valve openings –Main point of insertion for cardiac muscle –Blocks direct spread of electrical impulses

22. Fibrous Skeleton & Valve Structure Pulmonary valve Aortic valve Area of cutaway Mitral valve Tricuspid valve Myocardium Tricuspid (right atrioventricular) valve Mitral (bicuspid, left atrioventricular) valve Aortic valve Pulmonary valve Fibrous skeleton Anterior

23. The Beating Heart Blood returning to the heart fills atria, putting pressure against atrioventricular valves; atrioventricular valves are forced open. As ventricles fill, atrioventricular valve flaps hang limply into ventricles. Atria contract, forcing additional blood into ventricles. (a) AV valves open; atrial pressure greater than ventricular pressure Direction of blood flow Atrium Ventricle Cusp of atrioventricular valve (open) Chordae tendineae Papillary muscle 1 2 3

24. The Beating Heart Ventricles contract, forcing blood against atrioventricular valve cusps. Atrioventricular valves close. Papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria. (b) AV valves closed; atrial pressure less than ventricular pressure Atrium Blood in ventricle Cusps of atrioventricular valve (closed) 1 2 3

25. The Beating Heart As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open. As ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close. (a) Semilunar valves open (b) Semilunar valves closed Aorta Pulmonary trunk

26. Heart Sounds “Lub-dub”  sound of valves closing –First sound “lub” The AV valves closing –Second sound “dub” The semilunar valves closing

27. Heart Sounds Pulmonary valve Aortic valve Area of cutaway Mitral valve Tricuspid valve Myocardium Tricuspid (right atrioventricular) valve Mitral (left atrioventricular) valve Aortic valve Pulmonary valve Fibrous skeleton Anterior “Lub” “dub”

28. Pathway of Blood Through the Heart Beginning with oxygen-poor blood in the superior & inferior venae cavae –Go through pulmonary & systemic circuits –Blood passes through all structures sequentially Atria contract together Ventricles contract together

29. Blood Flow Through the Heart Right atrium Aorta To body To heart To lungs Mitral valve Left ventricle Left atrium Left atrium Aorta Left ventricle Four pulmonary veins Right ventricle Superior vena cava (SVC) Inferior vena cava (IVC) Coronary sinus Right atrium Pulmonary trunk Pulmonary veins Pulmonary arteries Aortic semilunar valve Tricuspid valve Tricuspid valve Pulmonary trunk Right ventricle Pulmonary semilunar valve Pulmonary semilunar valve IVC SVC Two pulmonary arteries carry the blood to the lungs (pulmonary circuit) to be oxygenated. Oxygen-rich blood returns to the heart via the four pulmonary veins. Oxygen-poor blood returns from the body tissues back to the heart. Oxygen-rich blood is delivered to the body tissues (systemic circuit). Oxygen-rich blood Oxygen-poor blood Mitral valve Aortic semilunar valve Coronary sinus

30. Heartbeat 70–80 beats per minute at rest (adult) –Systole  contraction of a heart chamber –Diastole  expansion (relaxation) of a heart chamber Systole & diastole also refer to –Stage of heartbeat when ventricles contract & expand

31. Structure of Heart Wall Walls differ in thickness –Atria  thin walls –Ventricles  very thick walls (especially left) –Systemic circuit Longer than pulmonary circuit Has greater resistance to blood flow

32. Structure of Heart Wall Left ventricle: 3 times thicker than right –Exerts more pumping force –Flattens right ventricle into a crescent shape Right ventricle Left ventricle Interventricular septum

33. Cardiac Muscle Tissue Forms a thick layer called myocardium –Striated like skeletal muscle –Contractions pump blood through the heart & into blood vessels

34. Cardiac Muscle Tissue Cardiac muscle cells –Short –Branching –Have 1 or 2 nuclei –Not fused muscle cells like skeletal muscle fibers

35. Cardiac Muscle Tissue Cells join at intercalated discs –Complex junctions –Form cellular networks Cells are separated by delicate endomysium –Binds adjacent cardiac fibers –Contains blood vessels & nerves

36. Intercalated Discs Intercalated discs  complex junctions –Adjacent sarcolemmas interlock –Possess 3 types of cell junctions Desmosomes Fasciae adherens  long desmosome-like junctions Gap junctions

37. Fasciae adherensGap junctions Microscopic Anatomy of Cardiac Muscle NucleusIntercalated discsCardiac muscle cell (a) Nucleus I bandA band Cardiac muscle cell Sarcolemma Z disc Mitochondrion T tubule Sarcoplasmic reticulum I band Intercalated disc (b)

38. Cardiac Muscle Tissue Triggered to contract by  Ca 2+ entering the sarcoplasm –Signals sarcoplasmic reticulum (SR) to release Ca 2+ ions –Ions diffuse to sarcomeres What does this trigger?  sliding filament mechanism – remember this?

39. Cardiac Muscle Tissue Not all cardiac cells are innervated –Will contract in rhythmic manner without innervation –Inherent rhythmicity Is the basis of the rhythmic heartbeat – heart can beat on its own!

40. Conducting System Cardiac muscle has intrinsic ability to: –Generate & conduct impulses –Signal cells to contract rhythmically Conducting system: –A series of specialized cardiac muscle cells –Sinoatrial (SA) node (= pacemaker) sets the inherent rate of contraction  generates the electrical impulses

41. Conducting System of the Heart The Sinoatrial (SA) node (pacemaker) generates impulses. Internodal pathway Superior vena cavaRight atrium Left atrium Purkinje fibers Inter- ventricular septum The impulses pause (0.1 sec) at the Atrioventricular (AV) node. The atrioventricular (AV) bundle of His connects the atria to the ventricles. The bundle branches conduct the impulses through the interventricular septum. The Purkinje fibers stimulate the contractile cells of both ventricles. 1 2 3 4 5

42. Thoracic spinal cord The vagus nerve (parasympathetic) decreases heart rate. Cardioinhibitory center Cardio- acceleratory center Sympathetic cardiac nerves increase heart rate and force of contraction. Medulla oblongata Sympathetic trunk ganglion Dorsal motor nucleus of vagus Sympathetic trunk AV node SA node Parasympathetic fibers Sympathetic fibers Interneurons Innervation of the Heart Heart rate is altered by external controls Nerves to the heart include –Visceral sensory fibers –Parasympathetic branches of the vagus nerve –Sympathetic fibers  from cervical & upper thoracic chain ganglia

43. Blood Supply to the Heart Functional blood supply –Coronary arteries Arise from the aorta –Located in the coronary sulcus –Main branches Left & right coronary arteries

44. Blood Supply to the Heart Right ventricle Right coronary artery Right atrium Right marginal artery Posterior interventricular artery Anterior interventricular artery Circumflex artery Left coronary artery Aorta Anastomosis (junction of vessels) Left ventricle Superior vena cava (a) The major coronary arteries Left atrium Pulmonary trunk Superior vena cava Anterior cardiac veins Small cardiac vein Middle cardiac vein Great cardiac vein Coronary sinus (b) The major cardiac veins

45. Disorders of the Heart Coronary artery disease –Atherosclerosis  fatty deposits –Angina pectoris  chest pain –Myocardial infarction  blocked coronary artery Heart attack! –Silent ischemia  no pain or warning; lack of blood & O 2 to certain area of heart

46. Disorders of the Heart Heart failure –Progressive weakening of the heart –Cannot meet the body’s demands for oxygenated blood Congestive heart failure (CHF) –Heart enlarges –Pumping efficiency declines Pulmonary arterial hypertension –Enlargement & potential failure of right ventricle

47. Disorders of the Conduction System Arrhythmias  variation from normal heart rhythm (irregular); often valve problems –Ventricular fibrillation Rapid, random firing of electrical impulses in the ventricles Results from crippled conduction system Common cause of cardiac arrest Ventricles cannot beat together in synchrony

48. Disorders of the Conduction System Arrhythmias –Atrial fibrillation Impulses circle within atrial myocardium, stimulating AV node Can promote formation of clots –Leads to strokes Occur in episodes characterized by: –Anxiety, fatigue, shortness of breath, palpitations

49. Disorders of the Heart Congestive heart failure (CHF)

50. Development of the Heart Heart folds into thorax region ~Day 20–21 Heart starts pumping on ~Day 22! Earliest heart chambers are unpaired Heart in near-final form by Day 35 Blood travels different route than in adult – blood doesn’t pick up O 2 from lungs, but from placenta/mom! Atrium Aorta Superior vena cava Inferior vena cava Ventricle Tubular heart Ventricle 4a 4 3 2 1 Foramen ovale Ductus arteriosis Pulm trunk

51. Congenital Heart Defects Can be traced to month 2 of development –Most common defect is ventricular septal defect 2 basic categories of defect –Inadequately oxygenated blood reaches body tissues –Ventricles labor under increased workload

52. Congenital Heart Defects Occurs in ~1 in every 500 births Occurs in ~1 in every 1500 births Narrowed aorta Occurs in ~1 in every 2000 births (a) Ventricular septal defect. The superior part of the inter- ventricular septum fails to form; thus, blood mixes between the two ventricles. More blood is shunted from left to right because the left ventricle is stronger. (b) Coarctation of the aorta. A part of the aorta is narrowed, increasing the workload of the left ventricle. (c) Tetralogy of Fallot. Multiple defects (tetra = four): (1) Pulmonary trunk too narrow and pulmonary valve stenosed, resulting in (2) hypertrophied right ventricle; (3) ventricular septal defect; (4) aorta opens from both ventricles.

53. The Heart in Old Age Some age-related changes  1.Hardening & thickening of heart valve cusps 2.Decline in cardiac reserve* (= extra pumping ability) 3.Fibrosis of cardiac muscle  excess fibrous connective tissue; less elastic & contractile *Cardiac reserve = the difference between the rate at which the heart pumps blood at a particular time & its maximum capacity for pumping blood

54. The Heart in Old Age Heart usually functions well throughout life But in America, heart disease has become the #1 cause of death! Regular aerobic exercise increases the strength & efficiency of the heart Decreases bad cholesterol levels (LDL) & lowers blood pressure So, again  exercise is key!

55. What You Can Do… Exercise 150 minutes+/week (of moderate exercise) Or exercise 75 minutes+/week (of vigorous exercise) Helps clear fatty deposits in coronary arteries & maintains good cardiovascular health throughout life Also increases life expectancy! (Recommendations by AHA)

56. Some Hot Current Research Stem cells to study human heart cells (their development, growth, & function) Future promise for regenerative medicine Cardiomyocytes derived from human stem cells (all in the dish!)

57. Questions…? What’s Next? Lab: Sheep Heart Dissection! & Start Blood Vessels Wed Lecture: Blood Vessels Wed Lab: Blood Vessels & Respiratory Sys