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.
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
6. GENERAL ANATOMY INCLUDING ATRIUM AND CHAMBERS
INTERNAL FEATURES
Right 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
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.
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