Anatomy and Histology of CVS PDF

Cardiovascular System By-Tirufat Tiruneh(MSc.in Clinical Anatomy)  Thoracic cavity 2 09/24/2024 Introduction The thoracic cavity: is cone shaped space bounded by thoracic wall Freely communicates to the root of the neck and closed inferiorly b...

Cardiovascular System By-Tirufat Tiruneh(MSc.in Clinical Anatomy)  Thoracic cavity 2 09/24/2024 Introduction The thoracic cavity: is cone shaped space bounded by thoracic wall Freely communicates to the root of the neck and closed inferiorly by the diaphragm 3  Divisions of the thoracic cavity has 3-divisions: Two pleural cavities (Right & Left) occupy lateral part & contain the lungs Mediastinum Massive space b/n the two pleural cavities Contains several structures (visceras) 4 5 Mediastinum 6  The Mediastinum all of organs(space) between the left and right mediastinal pleurae is called mediastinum. It extends from the sternum in front to the vertebral column behind, and from the thoracic inlet above to the diaphragm below.  Divisions of mediastnum Transverse thoracic plane (imaginary plane connecting sternal angle to lower border of T4) divides mediastnum into two: 1. Superior mediastnum- from the superior thoracic aperture to transverse thoracic plane below Contents of superior mediastnum (anterior to posterior) are: Upper part of thymus Great vessels Veins – left brachiocephalic, upper half of SVC Arteries – arch of aorta & its branches Nerves Vagus nerve, phrenic nerve, Left recurrent laryngeal nerve (a branch of left vagus) & Cardiac plexus Trachea Esophagus (upper thoracic part) Sympathetic trunk 8 9  2. Inferior mediastnum- from the transverse thoracic plane to the diaphragm inferiorly  The inferior mediastnum is sub-divided in to 3 by the fiberous pericardium enclosing the heart: Anterior, middle and posterior 1 09/24/2024 0 A.Anterior mediastinum – Behind the sternum & anterior to fiberous pericardium Contents: Remains of lower part of thymus in adults sternopericardial ligaments & parasternal lymph nodes B. Middle mediastinum – enclosed by pericardial sac Contents - pericardium and its contents  Contents within the pericardium are: heart and roots of great vessels (aorta, pulmonary trunk , SVC, IVC and pulmonary veins) 12 The pericardium is a fibro-serous closed sac protects the heart; anchors the heart; and prevents sudden overfilling Has two components 1. fibrous pericardium 2. serous pericardium 13 09/24/2024  Fibrous pericardium Is tough fibrous connective tissue outer layer Anteriorly attached to the ends of body of sternum by sternopericardial ligaments Has: Apex directs upward lies at the level of sternal angle fused with roots of great vessels Base attached to the central tendon of diaphragm 14 Serous pericardium Double layered serous membrane outer layer – parietal pericardium; fused with inner surface of fibrous pericardium inner layer – visceral pericardium, attached to the surface of heart & also called epicardium The two layers are continuous to each other at the roots of great vessels  b/n visceral serous & parietal serous layer is the pericardial cavity filled with thin film of pericardial fluid creates a relatively friction-free environment 16 c. Posterior mediastinum  anterior to bodies of T5-T12 and  behind pericardial sac & portion of diaphragm  contains esophagus (lower part), thoracic aorta, sympathetic ganglion chain & thoracic duct 17 rdium & pericardial cavity 18 Pericardial sinuses Pericardial reflection from the parietal to visceral forms sinuses on the posterior aspect of the heart Oblique sinus bounded by IVC and four pulmonary veins Transverse sinus Above the oblique sinus b/n SVC posteriorly and pulmonary trunk & aorta anteriorly used for legating large vessels during cardiac surgery 19 21  The heart 22 09/24/2024  Introduction The heart is central pumping organ for blood right side of heart: receives oxygen poor blood from the body tissues through SVC, IVC & coronary sinus and then pumps it to the lungs left side of heart: receives oxygenated blood from the lungs through the 4- pulmonary veins and then pumps through aorta 09/24/2024 23  Size, location and position of heart The heart is about the size of a fist It weighs between 250 - 350 grams It extends from the 2nd rib to 5th intercostal space Two thirds of the heart lies to the left of the mid- sternal line 24 09/24/2024 Pathway of circulation Pulmonary circulation The blood vessels that carry blood to and from the lungs form the pulmonary circulation Involves: Two Pulmonary arteries & four pulmonary veins The pulmonary circulation, served by the right ventricle through pulmonary trunk (arteries), is a low pressure circulation 25 09/24/2024 Systemic circulation The vessels that carry blood to and from all the body tissues form the systemic circulation The left side of the heart is the systemic pump The left ventricle pumps blood into the aorta and from there into many distributing arteries and to capillaries Blood then returns to the right atrium of the heart via systemic veins and the cycle continues 09/24/2024 26  27 09/24/2024  Heart Chambers The heart has four chambers separated by septa Atria two atria two ventricles The atria lie above and behind ventricles Upper part of each atrium has an appendage called auricle Ventricles Septum 28 09/24/2024  Coronary Grooves Sulcus Indicate the boundaries of its four chambers externally (marks septum internally) coronary sulcus (Atrioventricular groove) encircles the junction of the atria and ventricle inter-ventricular sulcus (Anterior and posterior) b/n the right and left ventricles Grooves contain fat, in which vessels are embedded Anterior Interventricular 29 09/24/2024 Sulcus Parts of the heart The apex Base points downwards, forwards and to the left lies in left 5th intercostal space 9cm from mid-line formed by left ventricle Left atrium The base (posterior surface) directs to the right shoulder Lies on the bodies of T6 –T9 formed mainly by left atrium & small part of right atrium Left ventricle apex 09/24/2024 30 Borders Right – vertical, formed by right atrium Left – oblique, formed mainly by left ventricle & partly by left auricle Inferior – horizontal, formed mainly by right ventricle; left ventricle near the apex Superior – irregular, formed by the two atria 09/24/2024 31 Surfaces  Diaphragmatic (inferior) surface Rests on central tendon of diaphragm Formed by mainly by left ventricle (about 2/3rd ) and right ventricle  Right pulmonary surface Formed by right atrium 09/24/2024 32 Surfaces  Sternocostal (anterior) surface Faces anteriorly, superiorly and to the left Formed mainly by right ventricle & right aurcle; and partly by left ventricle & left auricle  Left pulmonary surface Formed by left ventricle 09/24/2024 33  Surface marking of the heart The outline of the heart can be represented on the surface by the irregular quadrangle bounded by the following four points: 1. the 2nd left costal cartilage (1.2cm) from the edge of the sternum 2. the 3rd right costal cartilage (1.2cm) from the sternal edge 3. the 6th right costal cartilage (1.2cm) from the sternum 4. the 5th left intercostal space (9cm) from the midline (corresponding to the apex beat) 09/24/2024 34  35 09/24/2024  Right atrium Receives venous blood from the body through SVC, IVC and coronary sinus & pumps it to right ventricle through right AV orifice Upper end is prolonged to left to form right auricles ear like appendages, increase the atrial capacity 36 09/24/2024 Sulcus terminalis shallow groove along right border run vertically from SVC to IVC Surface land mark of internal muscular elevation (cristae terminalis) Sulcus terminalis 09/24/2024 37 Internal features of right atrium The interior has 2 parts The smooth posterior part (sinus venarum) SVC & IVC opens into it Coronary sinus opens between IVC orifice and right AV orifice The rough anterior part Present a series of transverse muscular ridges, pectinate muscles Arise from crista terminalis and run towards AV orifice 09/24/2024 38 09/24/2024 39  4 09/24/2024 0 Interatrial septum Separate the two atria Possesses a shallow depression, fossa ovalis Remnant of the opening, foramen ovale, existed in the fetal heart Limbus fossa ovalis: a prominent margin of fossa ovalis; valve of foramen ovale 09/24/2024 41  Right ventricle Receive blood from right atrium and pump into pulmonary trunk Superiorly tapers into a cone shaped out let which opens in to pulmonary trunk This cone shaped smooth part is called conus arteriosu (infundibulum) 42 09/24/2024 Internal structure of right ventricle Inflow part – rough due to muscular ridges called trabeculae carneae The smooth outflow part is separated from inflow part by supraventricular crest 09/24/2024 43 Papillary muscles Conical or finger like muscular projections arise from ventricular wall Are 3: anterior, posterior & septal Contract before contraction of ventricle, to hold cusps (leaflets of AV-valve) 09/24/2024 44 The tips of Papillary muscles are anchored to free margins of cusps through tendon like fiberous cords called chordae tendineae Prevent inversion of cusps in to the atrium during ventricular contraction 09/24/2024 45 Interventricular septum Partition b/n the two ventricles Has two parts Membranous part – thin superoposterior part devoid of muscle Muscular part – thick , anteroinferior major portion of the septum 09/24/2024 46 Septomarginal trabecula (moderator band) Muscular ridge connecting interventricular septum to base of anterior papillary muscle Facilitate conduction time toward papillary muscle 09/24/2024 47  4 09/24/2024 8 Left atrium Receives the four pulmonary veins 2 right and 2 left Interior Is smooth pectinate muscles are found only in the auricle 49 09/24/2024  Left Ventricle Receive blood from left atrium via left AV valve & pumps into the aorta The cavity is circular and longer than the right The wall of the left ventricle is 2-3 times thicker than that of the right ventricle Due to the work load 50 09/24/2024  Internal structure of left ventricle posterosuperior part is smooth but the rest part is roughed by: Trabeculae carneae which are finer and more numerous than the right Papillary muscles: two; anterior and posterior Smooth walled part– aortic vestibule, leads to aortic orifice (opening) 09/24/2024 51 Left Ventricle: Internal structure 52 09/24/2024 Contraction and relaxation of the heart The two atria contract together, followed by the simultaneous contraction of the two ventricles The synchronous pumping action of the heart two pumps constitute cardiac cycle The cycle begins with ventricular elongation (relaxation) and filling with blood termed as diastole and ends with a period of ventricular shortening (contraction) and emptying called a systole Systole and diastole refers to the ventricles which are the dominant heart chambers 09/24/2024 53  Heart Valves Heart valves that are placed b/n the atria and the ventricles are called AV- valves and those b/n the ventricles and the large arteries that leave the heart are called semilunar valves The valves are formed by more than one cusps (flexible flaps of endocardium reinforced by connective tissue) Valves open and close in response to differences in blood pressure 54 09/24/2024 Atrioventricular (AV) Valves Right AV valve (tricuspid): has three cusps anterior, posterior septal Left AV valve (bicuspid): has two cusps anterior & posterior 09/24/2024 55  Cusps have two surfaces atrial – smooth ventricular – rough The bases of each cusps are attached to fibrous ring (part of the fibrous skeleton of the heart surrounding AV orifice) The fibrous ring resists (limits) dilation of orifices 09/24/2024 56 When the atria contract, force blood into the ventricles through open AV valve When the ventricles begin to contract, intra- ventricular pressure rises forcing blood superiorly against the valve flaps (the pressure closes the valve) The chordae tendonae and the papillary muscles anchor the flaps in their closed position 57 09/24/2024 Semilunar (SL) Valves The aortic and pulmonary semilunar valves are found at the bases of aorta & pulmonary trunk respectively Each semilunar valve is made up of three pocket like cusps All the cusps are concave superiorly 09/24/2024 aortic 58 The Aortic Semilunar Valve (ASL) has posterior, right & left cusps B/n the three semilunar cusps & the wall of the ascending aorta are pocket-like spaces-the aortic sinuses Blood in sinuses prevents cusps from sticking to wall of the vessel and forces the cusps closed 59 09/24/2024 The pulmonary Semilunar Valve (PSL) has anterior, right & left cusps B/n the cusps & the wall of pulmonary trunk is –pulmonary sinuses 60 09/24/2024  Valve disease Valve problems consist of two basic types: incompetence (insufficiency) which results from poorly functioning valves Stenosis a narrowing of the orifice, caused by the valve's inability to open fully Both problems lead to a poorly functioning valve and subsequent heart changes 61 09/24/2024 Heart Sounds The closing of the heart valves causes vibrations in the adjacent blood and heart walls that account for the familiar “lub-dup” sounds of the heartbeat The “lub” is produced by the closing of the AV valves at the start of ventricular systole The “dup” is produced by the closing of the semilunar valves at the end of ventricular systole 09/24/2024 62 Listen for heart sounds using stethoscope at the left 2nd intercostal space near the sternum (pulmonary semilunr) At right 2nd intercostal space near the sternum (aortic semilunar) At left 5th intercostal space 9cm from mid- sternal line (mitral or apex beat) At right 5th intercostal space near the sternum (tricuspid) 6 09/24/2024 3  6 09/24/2024 4  Layers of the Heart Wall The walls of all four heart chambers consist of three major layers or tunics: the internal endocardium the middle myocardium the external epicardium All three layers are richly supplied with blood vessels 65 09/24/2024  Vasculature of the heart Coronary vasculature (arterial blood supply to the heart & venous blood return from the heart itself) is the shortest path of circulation in the body Comprise two coronary arteries, coronary sinus and cardiac veins These vessels course just deep to epicardium, embedded in fat and mainly supplies myocardium and epicardium endocardium obtains oxygen & nutrient from the blood inside the chambers 66 09/24/2024 Coronary arteries anastamose with each other 09/24/2024 67 Right coronary artery Arise from right aortic sinus and runs in right coronary groove Near its origin it gives off SA nodal branch that supply SA node As it approaches the right side of the heart in coronary groove, it gives off the right marginal branch which supplies the right side of the right ventricle (along inferior margin) Then it turns to the left and continues in posterior part of right coronary groove 68 09/24/2024 Right coronary artery At crux of heart (junction of interatrial & interventricular septa posteriorly) it gives rise to AV nodal branch Then gives off large branch, posterior inter-ventricular artery, that run in posterior interventricular groove to the apex of the heart. Terminal branch continues for short distance in posterior part of left coronary groove and is called left ventricular branch 69 09/24/2024  70 09/24/2024 Right coronary artery supplies The whole of right atrium Most of the right ventricle Part of left ventricle (diaphragmatic surface) by its posterior intervenricular and left ventricular branches posterior 1/3rd of interventricular septum by perforating branches of posterior intervenricular artery 09/24/2024 71  The left coronary artery Arise from left aortic sinus The proximal part of LCA (near its origin), is sandwiched b/n left side of pulmonary trunk and left auricle As it emerges to enters the left coronary sulcus, at the superior end of the anterior IV groove, it divides into two: Anterior inter-ventricular branch & Circumflex branch 09/24/2024 72 Anterior IV (interventricular) branch Descends in the anterior interventricular groove to the apex It turns over the apex & anastomose with posterior IV- branch of the right Supplies sternocostal surfaces of both ventricles and anterior 2/3rd of interventricular septum It also gives lateral (diagonal) branch 09/24/2024 73 The circumflex branch Runs in left coronary groove to posterior surface of left ventricle In 40% of people, it gives SA nodal branch It also gives left marginal artery which supplies left side of left ventricle 09/24/2024 74 Left coronary artery supplies The left atrium Most of the left ventricle Part of sternocostal surface of right ventricle anterior 2/3rd of interventricular septum SA node (in 40% of people) 09/24/2024 75  Veins of the heart Coronary sinus Wide venous channel that lies in the posterior part of left coronary sulcus It receives the veins draining the heart right atrium empties directly into the right atrium 76 09/24/2024 The great cardiac vein is the main tributary of the coronary sinus. Its 1st part, accompanies anterior IV artery Its 2nd part turns left & lies at the left coronary sulcus with the circumflex branch of the LCA Ends at left end of coronary sinus 77 09/24/2024 The middle cardiac vein accompanies the posterior IV-artery Opens at the right end of coronary sinus The small cardiac vein accompanies the right marginal branch of the RCA 78 09/24/2024  79 09/24/2024 Anterior cardiac vein from the anterior aspect of right ventricle empty directly to auricles of right atrium Smallest cardiac veins (venae cordis minimae) begin in myocardium and open directly into all chambers 80 09/24/2024 The oblique vein of the left atrium (of Marshall) is a small vein, descends over the posterior wall of the left atrium merges with the great cardiac vein to form the coronary sinus 81 09/24/2024 Lymphatic drainage of heart Lymphatic vessels in myocardium and sub endocarial tissue pass to subepicardial lymphatic plexus Vessels from the plexus follow coronary arteries A single vessel ascends between pulmonary trunk and left atrium and ends in inferior trachio bronchial lymph nodes 09/24/2024 82  Innervation of the heart Although the heart’s inherent rate of contraction is set by the SA node, this rate can be increased or decreased by extrinsic neural controls Parasympathetic nerves From branches of the Vagus nerve in the cardiac plexus Postsynaptic cell bodies are located in the atrial wall and near SA and AV nodes and along coronary arteries slows the heart rate, reduces force of contraction and constricts coronary arteries Sympathetic nerves From the cervical and upper thoracic sympathetic chain ganglia forming cardiac plexus Postsynaptic fibers end in SA and AV nodes and along coronary arteries increases the rate and force of heart contractions & produce dilation of coronary arteries 83 09/24/2024 Histology of the heart The heart wall can be viewed as a three t layered structure. – a. Inner layer = Endocardium – b. middle Layer = myocardium – c. Outer layer = Epicardium (also called the pericardium) 85 09/24/2024  Heart Wall Myocardiu m Endocardi Epicardiu um m 86 09/24/2024  Endocard ium The endocardium is the inner layer of the heart wall and consists. Composed of: – 1. The endothelial lining made of Simple squamous epithelium – 2. The underlying connective tissue layers – Subendocardium: Is in contact with cardiac muscle and contains small vessels, nerves, and Purkinje Fibers. 2 1 8 09/24/2024 7  Purkinje Impulse conducting fibers Fibers Large modified muscle cells – Cell Cluster in groups together – 1to 2 nuclei and stain pale due to fewer myofibrils 8 09/24/2024 8  % ,) Endocardium ’“ Purkinje Fibers (ÇXt 8 09/24/2024 9  Mayocardi um Thickest layer of the heart Thickest in left ventricle because must pump hard to overcome high pressure of systemic circulation Right atrium the thinnest because of low resistance to back flow Consist of cardiac muscle cells = myocytes – Different from smooth or skeletal muscle cells due to placement of nuclei, cross striations, and intercalated disks 90 09/24/2024  Eranchi ng myocyt es Central nuclei Fibers with Cross Striations 9 09/24/2024 1  Intercalated disks Are (gap junctions) link the cells together and define their borders. Intercalated discs are the major portal for cardiac cell-to-cell communication, which is required for coordinated muscle contraction and maintenance of circulation Allow muscle action potentials to spread from one cardiac muscle fiber to another 92 09/24/2024  Electron micrograph of a longitudinal section of heart muscle. Note the striation pattern and the alternation of myofibrils and mitochondria rich in cristae. Note the sarcoplasmic reticulum (SR), which is the specialized calciumtstoring smooth endoplasmic reticulum. x30,000. 93 09/24/2024  Epicardium Outermost layer of the heart Composed of connective tissue with nerves, vessels, adipocytes and an outer layer of mesothelium Mesothelium secretes pericardial fluid Covers and protects the heart 9 09/24/2024 4  Anatomy and histology of Blood Vessels Arteries and veins are composed of three tunics – – tunica interna – tunica media – tunica externa Lumen – central blood-containing space surrounded by tunics 95 09/24/2024  Tunica intima Tunica media Tunica adventitia 1.Endothelial 1.Smooth muscle 1. Mostly collagenous cell lining cells, collagen fibers 2.Subendothelia fibers, and ground 2.Elastic fibers l CT layer substance (not lamellae) 3.Internal 2.Elastin in the 3.Fibroblasts elastic lamina form of fenestrated and 3.External macrophages elastic lamina 4. Vasa vasorum 96 09/24/2024  Structure of Vessels 1 6 97 09/24/2024  Types of Blood vessels: Arteries Elastic Arteries: Thick-walled arteries near the heart; the aorta and its major branches. Large lumen allows low-resistance conduction of blood. Contain elastin fibers in all three tunics. walls stretch and recoil to propel blood Withstand and regulate large blood pressure fluctuations.  Allow blood to flow fairly continuously through the body 98 09/24/2024  nica ntima Internal elastic lamin External elastic lam 9 09/24/2024 a 9  100 09/24/2024  Muscular(Distributing) arteries – distal to elastic arteries; deliver blood to body organs – Have thick tunica media with more smooth muscle and less elastic tissue – Active in vasoconstriction Arterioles – smallest arteries; lead to capillary beds – Control flow into capillary beds via vasodilation and constriction 101 09/24/2024  Muscular (distributing) arteries medium sized vessels tunica media contain more smooth muscle; less elastin major area of vaso- constriction & dilation to regulate blood flow 102 09/24/2024  103 09/24/2024 Arterioles (diameter of 0.3 mm or less)  smallest arteries; lead to capillary beds.  close to capillaries t single layer of muscle spiralling around the endothelial lining  regulates blood flow to capillary 104 09/24/2024  105 09/24/2024  Capillary 1 09/24/2024 0  Types of Capillaries Continuous capillaries. – No gaps between endothelial cells. – Adjacent cells held together with tight junctions. – Less permeable to large molecules than other capillary types. – Capillaries found in muscle, nervous tissue, adipose tissue Fenestrated capillaries – Have pores (fenestrae). – Highly permeable. – Found in intestinal villi, ciliary process of eye, choroid plexus, glomeruli of kidney Sinusoids capillaries. – Large diameter fenestrated capillaries – Very leaky with large lumens. – Blood flows sluggishly, allowing for modification in various ways – Found liver, bone marrow, lymphoid tissue and some endocrine organs. – Venous sinuses are similar in structure but even larger. E.g., spleen 09/24/2024 107  Structure of Capillary Walls 108 09/24/2024  Venules and Small Veins Venules drain capillary network – Endothelial cells and basement membrane with a few smooth muscle cells. – As diameter of venules increases, amount of smooth muscle increases. Small veins- Smooth muscle cells form a continuous layer. Addition of tunica adventitia made of collagenous connective tissue 109 09/24/2024  Veins and Venules (Contrasted to Arteries) Thinner walls Larger diameter Closer to skin Less muscle Less elastic Figure 15-3: Metarterioles 3 7 110 09/24/2024  Venules In Small Intestine 1 09/24/2024 1 Medium size veins Veins in these locations have a well developed muscular adventitia (muscle cells are oriented longitudinally). 112 09/24/2024  1 09/24/2024 1  Large veins – Formed when venules converge – Composed of 3 tunics Thin tunica media with circularly arranged smooth muscle cells. Thick tunica externa consisting of collagen fibers and elastic networks 114 09/24/2024  115 09/24/2024  * Vein 400X tunica externa tunica media tunica interna 116 09/24/2024  Venous System: Valves Veins have much lower blood pressure and thinner walls than arteries To return blood to the heart, veins have special adaptations – Large-diameter lumens, which offer little resistance to flow – Valves (resembling semilunar heart valves), which prevent backflow of blood Venous sinuses – specialized, flattened veins with extremely thin walls (e.g., coronary sinus of the heart and dural sinuses of the brain) 1 09/24/2024 1  1 09/24/2024 1  1 09/24/2024 1  1 09/24/2024 2  Artery Vs veins 1 09/24/2024 2  T ha nk You 12 09/24/2024 2