External Heart
External Anatomy of the Heart
Heart as an extremely active organ
Beats approximately 100,000 times a day
Approximately 35,000,000 heartbeats in a year
Total heartbeats in an average lifetime: approximately 2,500,000,000
Average weight of the heart
Average size female: approximately 250 grams
Average size male: approximately 300 grams
Dimensions of the Heart
Length of the heart: approximately 12 centimeters (5 inches)
Width of the heart: approximately 9 centimeters (3.5 inches)
Depth of the heart: approximately 6 centimeters (2.5 inches)
General size equates to that of a closed fist
Location of the Heart
Heart sits on the diaphragm
Diaphragm: muscle separating thoracic cavity from abdominal cavity
Thoracic cavity contains lungs in pleural cavities
Mediastinum region
Space between left and right pleural cavities
Contains several organs, including the heart
Pericardial Cavity
The space surrounding the heart
Located between visceral pericardium and parietal pericardium
Filled with serous fluid to reduce friction, facilitating smooth heart movement
Heart is protected by:
Sternum (bone)
Costal cartilages (connect ribs to sternum)
Ribs that form lateral and posterior walls of thoracic cavity
Trachea and esophagus located posteriorly to the heart
Thoracic vertebral bones also positioned posteriorly
Structure of the Heart
Apex of the heart
Pointy part that sits on the diaphragm
Base of the heart
Wider part opposite the apex
Heart orientation
Approximately two-thirds of the heart lies on the left side of the midline; one-third on the right side
Chambers of the Heart
Four chambers:
Upper chambers (atria)
Right atrium
Left atrium
Lower chambers (ventricles)
Left ventricle
Right ventricle
Function of the chambers
Atria receive blood from veins
Blood flows from atria to ventricles
Ventricles pump blood out into arteries
Blood Flow Through the Heart
Right side of the heart contains deoxygenated blood
Blood loses oxygen after flowing through tissues
Deoxygenated blood returns to the right atrium
Right ventricle pumps deoxygenated blood to the lungs
Oxygenation of blood occurs in the lungs
Left side of the heart contains oxygenated blood
Left atrium receives oxygenated blood
Left ventricle pumps oxygenated blood into arteries for distribution to organs and tissues
Coronary Sulcus and Grooves
Coronary sulcus: groove wrapping around the heart
Anterior interventricular sulcus: located between the two ventricles
Posterior interventricular sulcus: also located between the two ventricles
Coronary Blood Vessels
Aorta supplies the heart wall
First branches from aorta: coronary arteries
Right coronary artery: branches include
Marginal branch (supplies right ventricle with oxygenated blood)
Posterior interventricular artery or inferior interventricular artery (supplies both ventricles posteriorly)
Left coronary artery: branches include
Anterior interventricular artery (or left anterior descending artery, LAD) supplying anterior ventricles
Circumflex branch supplying left atrium and left ventricle
Venous Return From the Heart
Collection of deoxygenated blood from heart wall
Great cardiac vein collects from anterior side of ventricles
Drains into coronary sinus (large vein with thin walls on the posterior side)
Middle cardiac vein located in posterior interventricular sulcus
Anterior cardiac vein drains directly into the right atrium
Small cardiac vein located deep within the coronary sulcus
Summary of Venous Drainage
Most veins drain into the coronary sinus which then opens into the right atrium
Internal Anatomy of the Heart
Prepared to discuss internal structures of the heart