Chambers of heart

The heart has four chambers: two atria and two ventricles. The right atrium receives oxygen-poor blood from the body and pumps it to the right ventricle.

1. Chambers Of Heart PREPARED BY: Dr. Jaishree Tiwari (P.T)

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3. • Upon completing this chapter students should be able to: 1.Define Heart. 2. Brief Description about chambers of heart 3 Learning Objectives

4. INTRODUCTION The   heart  consists of four  chambers  in which blood flows. Blood enters the right atrium and passes through the right ventricle. The right ventricle pumps the blood to the lungs where it becomes oxygenated. The oxygenated blood is brought back to the  heart  by the pulmonary veins which enter the left atrium . • The heart is composed of 4 chambers . Right atrium , Right ventricle, Left atrium , Left ventricle. 4

5. IMAGE DESCRIPTION OF HEART 5

6. GENERAL ANATOMY INCLUDING ATRIUM AND CHAMBERS INTERNAL FEATURES R ight atrium - The interior of the right atrium is split into 2 parts: • A. Main smooth posterior part – the sinus venarum, and. • B. Rough anterior part – the atrium proper. The two parts are separated from every other by crista terminalis. The coronary sinus receives blood from the coronary veins. It opens into the right atrium between the inferior vena cava orifice and the right atrioventricular orifice. 6

7. Septal wall of the right atrium Developmentally it is originated from septum primum and septum secundum . The septal wall inside presents the following features: • A. Fossa ovalis , a shallow oval/saucer-shaped depression in the lower part, created by septum primum . – It represents the site of foramen ovale in the foetus. • B. Annulus ovalis /limbus fossa ovalis , creates the distinct upper and lateral margin of the fossa ovalis . – It represents the free edge of the septum secundum . Inferiorly the annulus ovalis is continuous with the left end of the valve of IVC. • C. Triangle of Koch, a triangular area bounded in front by the base of septal leaflet of tricuspid valve, behind by anterior margin of the opening of coronary sinus and above by the tendon of Todaro - a subendocardial ridge. – The atrioventricular node is located in this triangle. • D. Torus aorticus , an elevation in the anterosuperior part of the septum produced due to bulging of the non-coronary sinus of ascending aorta. 7

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9. 9 Right ventricle • The right ventricle is the thick-walled triangular chamber of the heart which interacts with the right atrium via right atrioventricular orifice and with the pulmonary trunk via pulmonary orifice. EXTERNAL FEATURES • A. It creates the majority of sternocostal surface and small part of the diaphragmatic surface of the heart . It also creates the inferior border. • B. It is divided from the right atrium by a more or less vertical anterior part of the coronary sulcus/ atrioventricular groove INTERNAL FEATURES A. The interior of right ventricle is composed of 2 parts: – (a) A large, lower rough inflowing part, and – (b) A small upper outflowing part, the infundibulum. • The 2 parts are divided from every other by a muscular ridge , the supraventricular crest ( infundibuloventricular crest ).

10. 10 B. The cavity of right ventricle is flattened by the forward bulge of the interventricular septum. In transverse section it is crescent shaped . C . The wall of the right ventricle is thinner than that of the left ventricle (ratio 1:3).

11. 11 Left Atrium • The left atrium receives oxygenated blood from the four pulmonary veins , and pumps it through the left atrioventricular orifice (guarded by the mitral valve) into the left ventricle. • In the anatomical position, the left atrium forms the posterior border (base) of the heart. • The left auricle extends from the superior aspect of the chamber , overlapping the root of the pulmonary trunk. • The interior surface of the left atrium can be divided into two parts , each with a distinct embryological origin: • Inflow portion – receives blood from the pulmonary veins. Its internal surface is smooth and it is derived from the pulmonary veins themselves. • Outflow portion – located anteriorly, and includes the left auricle . It is lined by pectinate muscles, and is derived from the embryonic atrium.

12. 12 EXTERNAL FEATURES left atrium • A. It is a thin-walled quadrangular chamber situated posteriorly behind and to the left side of right atrium . It creates greater part (left 2/3rd) of the base of the heart. • B. Its upper end is prolonged anteriorly to create the left auricle, which overlaps the infundibulum of right ventricle. • C. Behind the left atrium is located: – (a) Oblique sinus of serous pericardium – (b) Fibrous pericardium, which separates it from the esophagus . INTERNAL FEATURES of left atrium • A. The interior of left atrium is smooth, but the left auricle possesses muscular ridges in the form of reticulum. • B. The anterior wall of left atrial cavity presents fossa lunata , which corresponds to the fossa ovalis of the right atrium.

13. 13 Left Ventricle • The left ventricle receives oxygenated blood from the left atrium , and pumps it through the aortic orifice (guarded by the aortic valve) into the aorta . • In the anatomical position, the left ventricle forms the apex of the heart, as well as the left and diaphragmatic borders. Much like the right ventricle, it can be divided into an inflow portion and an outflow portion . • Inflow Portion • The walls of the inflow portion of the left ventricle are lined by trabeculae carneae , as described with the right ventricle . There are two papillary muscles present which attach to the cusps of the mitral valve. • Outflow Portion • The outflow part of the left ventricle is known as the aortic vestibule . It is smooth-walled with no trabeculae carneae , and is a derivative of the embryonic bulbus cordis .

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15. 15 Q.1 The terms systole and diastole refer to: A) sounds from the heart B) the major artery and vein from and to the heart C) heart contractions and relaxations D) rates of heart pulse Q.2 The blood pressure is measured by an instrument known as a: A) electrocardiogram B) electroencephalograph C) sphygmomanometer D) CAT scan machine Q.4 The interventricular septum and the intra-atrial septum separate the: A) chambers of the heart B) chambers of the lungs C) aorta and pulmonary artery D) bicuspid and tricuspid valves Q.3 The only vein in the body that transports oxygen-rich blood is the: A) coronary vein B) hepatic portal vein C) pulmonary vein D) aortic vein

16. REFERENCES Reference Books : BD chaurasia V ol 3 anatomy https ://teachmeanatomy.info/thorax/organs/heart/atria-ventricles/ 16