Anatomy, L.1 Level 1- Semester 2- Module 3A- CVS
External feature of the heart
Defination:
The heart is a hollow muscular organ inside the pericardium.
Position
- It lies in middle mediastinum behind the body of the sternum and costal cartilages.
-One third of the heart is to the right and two thirds are to the left of median plane.
Direction:
- Its long axis is directed downwards forwards and to the left.
Size:
- It measures 12 × 9 × 6 cm.
Weight:
- Adult females: 200 gm.
- Adult males: 300 gm.
Shape of the heart:
- The heart is conical in shape. It has:
▪ An apex.
▪ A base (posterior surface).
▪ Four borders.
▪ Four surfaces.
▪ Four grooves.
▪ Four chambers.
• Apex of the heart:
- Formed by the left ventricle.
- Directed downwards, forwards and to the left.
- Lies opposite the left 5th intercostal space 3.5 inches (9cm)
from the median plane just inside the midclavicular line.
- Overlapped by the left pleura and lung.
Page | 1
, Anatomy, L.1 Level 1- Semester 2- Module 3A- CVS
• Base of the heart:
- Quadrilateral in shape.
- Formed by the left atrium (mainly) and
to a small extent by the right atrium.
- Directed backwards and to the right.
- Lies opposite the middle four thoracic vertebrae (from 5th
to 8th)
- The base is limited inferiorly by the posterior part of the
coronary groove.
- Esophagus and descending aorta lie posterior to the base.
Borders of the heart:
1) Upper border:
• Oblique and is formed by the two atria (mainly the left atrium).
•Masked anteriorly by the pulmonary trunk,
ascending aorta and superior vena cava.
2) Right border:
• Vertical and is formed by the right atrium
only and extends form the SVC opening to
the IVC opening.
3) Left border:
• Rounded, ill defined and convex.
• Directed upwards and to the left.
• formed mainly by the left ventricle and partly by the left atrium.
4) Lower border:
• Sharp, horizontal and concave downwards due to the upward convexity of the diaphragm.
• Formed mainly by the right ventricle and partly by the left ventricle.
• Separates the sternocostal from the diaphragmatic surface.
Page | 2
External feature of the heart
Defination:
The heart is a hollow muscular organ inside the pericardium.
Position
- It lies in middle mediastinum behind the body of the sternum and costal cartilages.
-One third of the heart is to the right and two thirds are to the left of median plane.
Direction:
- Its long axis is directed downwards forwards and to the left.
Size:
- It measures 12 × 9 × 6 cm.
Weight:
- Adult females: 200 gm.
- Adult males: 300 gm.
Shape of the heart:
- The heart is conical in shape. It has:
▪ An apex.
▪ A base (posterior surface).
▪ Four borders.
▪ Four surfaces.
▪ Four grooves.
▪ Four chambers.
• Apex of the heart:
- Formed by the left ventricle.
- Directed downwards, forwards and to the left.
- Lies opposite the left 5th intercostal space 3.5 inches (9cm)
from the median plane just inside the midclavicular line.
- Overlapped by the left pleura and lung.
Page | 1
, Anatomy, L.1 Level 1- Semester 2- Module 3A- CVS
• Base of the heart:
- Quadrilateral in shape.
- Formed by the left atrium (mainly) and
to a small extent by the right atrium.
- Directed backwards and to the right.
- Lies opposite the middle four thoracic vertebrae (from 5th
to 8th)
- The base is limited inferiorly by the posterior part of the
coronary groove.
- Esophagus and descending aorta lie posterior to the base.
Borders of the heart:
1) Upper border:
• Oblique and is formed by the two atria (mainly the left atrium).
•Masked anteriorly by the pulmonary trunk,
ascending aorta and superior vena cava.
2) Right border:
• Vertical and is formed by the right atrium
only and extends form the SVC opening to
the IVC opening.
3) Left border:
• Rounded, ill defined and convex.
• Directed upwards and to the left.
• formed mainly by the left ventricle and partly by the left atrium.
4) Lower border:
• Sharp, horizontal and concave downwards due to the upward convexity of the diaphragm.
• Formed mainly by the right ventricle and partly by the left ventricle.
• Separates the sternocostal from the diaphragmatic surface.
Page | 2
