Cardiovascular System Part-2 2023-24 PDF

Cardiovascular System Part-2 Anatomy Course ANAT 211, 212 and 213 Term 2, 2023-24 Basic Sciences Department, COSHP, KSAU-HS, KSA Cardiovascular System Part-2 By the end of this session the student should be able to: Describe internal features of the heart in terms of chambers, openings and valves. D...

Cardiovascular System Part-2 Anatomy Course ANAT 211, 212 and 213 Term 2, 2023-24 Basic Sciences Department, COSHP, KSAU-HS, KSA Cardiovascular System Part-2 By the end of this session the student should be able to: Describe internal features of the heart in terms of chambers, openings and valves. Differentiate between arteries and veins. Define arterioles, capillaries and venules. Right Atrium Consists anteriorly of a small muscular pouch-like appendage called the right auricle, and posteriorly of a main cavity (sinus venarum). Sinus venarum is smooth walled main part of the atrium, lies posterior to the muscular ridge. The superior and inferior vena cavae and the coronary sinus empty into sinus venarum The crista terminalis is a muscular ridge that separates the anterior and posterior portions of the right atrium from the inside. Externally it is indicated by the sulcus terminalis The part of the atrium anterior to the ridge, the auricle is roughened by presence of bundles of muscle fibres called the pectinate muscles. Right Atrium The interatrial septum It separates the right atrium from the left atrium, which lies posteriorly and to the left of the right atrium The fossa ovalis (oval fossa) It is located in the right atrium on the interatrial septum. It is a remnant of the fetal foramen ovale. It closes at birth Openings in the Right Atrium The superior vena cava (SVC) opens into the upper part of the right atrium. It returns blood to the heart from the upper half of the body The inferior vena cavae (IVC) opens into the lower part of the right atrium. It returns blood from the lower half of the body The coronary sinus opens into the right atrium near the opening of the IVC. It returns blood from the walls of the heart Right atrioventricular orifice (opening) lies anterior to the IVC opening. It leads to the right ventricle and is guarded by tricuspid valve Right Ventricle It forms most of the sternocostal surface of the heart. The walls are thicker than those of the right atrium and have numerous irregular muscular ridges called trabeculae carneae Conus arteriosus (infundibulum) is the funnel shaped, outflow tract of the right ventricle which gives rise to the pulmonary trunk Septomarginal trabeculae (moderator band) a free band of cardiac muscle, that crosses the cavity of the ventricle from the interventricular septum to the base of the anterior papillary muscle. Right Ventricle Papillary muscles are three irregular muscle bundles, lining the wall of the ventricle except at the infundibulum. They connect the ventricular wall to the atrioventricular (tricuspid) valve Anterior papillary muscle Posterior papillary muscle Septal papillary muscle Chordae tendineae are slender, fibrous threads that arise from apices of the papillary muscles and insert into the free edges and ventricular surfaces of the valve cusps, connecting the papillary muscles to the cusps of tricuspid valve Tricuspid Valve and Pulmonary Valve Right atrioventricular (tricuspid) valve It is located between the right atrium and right ventricle. The valve is formed by three fibrous cusps This valve blocks the reflux of blood into the right atrium when the right ventricle contracts. Pulmonary valve It lies at the apex of the conus arteriosus. It consists of three semilunar cusps that are concave when viewed from above. When the ventricle relaxes, these cusps open up like pockets to prevent the backflow of blood. Left Atrium Left atrium forms most of the posterior (base) surface of the heart Left auricle is a pouch-like appendage of the left atrium, containing musculi pectinati. Pectinate muscles are found only in the auricle The inflow portion is the posterior half of the atrium, it receives the four pulmonary veins. It has smooth walls Left Ventricle Left ventricle forms apex of the heart and has the thickest muscular walls Why? Atrioventricular (mitral or bicuspid) valve It is located between left atrium and left ventricle The valve is formed by two cusps, anterior and posterior cusps It blocks the backflow of blood to the left atrium when the left ventricle contracts Papillary muscles: two large muscles, anterior and posterior, which are connected to the mitral valve Chordae tendineae are thicker but less numerous than the right side Aortic valve are similar in structure to the pulmonary valve. Inside the aorta, deep to the cusps of the aortic valves, there are aortic sinuses. The right and left coronary arteries arise from the right and left aortic sinuses. Valves of the Heart Blood Vessels Blood is carried in a closed system of vessels that begins and ends at the heart Three major types of vessels: Arteries, Capillaries, and Veins Arteries always carry blood away from the heart Veins always carry blood toward the heart Capillaries contact tissue cells and directly serve cellular needs Capillaries join arteries and veins Arteries branch into smaller vessels called arterioles. They feed into the capillaries, where gas and nutrient exchange occurs Veins become progressively larger as they merge and get closer to the heart General Structure of Blood Vessels Arteries and veins are composed of three layers: Tunica interna (tunica intima) Tunica media Tunica externa (tunica adventitia) Types of Arteries 1-Conducting or Elastic Arteries (directly from and/or are closer to heart): aorta, common carotid, subclavian, and pulmonary trunk 2-Distributing or Muscular Arteries (distal to elastic arteries): external and internal carotids, brachial, femoral, renal, and splenic arteries Arterioles are smallest arteries; lead to capillary beds Capillaries Capillaries are the smallest blood vessels through which exchange of metabolites and gases take place. There are three structural types of capillaries: Continuous, Fenestrated, and Discontinuous Veins Venules are formed when capillary beds unite Veins are formed by union of venules Special adaptations of veins: Large lumens offer little resistance to blood flow Valves prevent backflow of blood