Anatomy of the Heart and Arterial System: A Comprehensive Guide

Posted on Apr 30, 2024 in Biology

Heart Anatomy

External Morphology

The adult heart measures approximately 12cm in length, 6cm anteroposteriorly, and 8cm transversely. It weighs around 300g in males and 250g in females. The coronary sulcus divides the heart into distinct portions. The heart consists of four layers: the pericardium, epicardium, myocardium, and endocardium.

Location and Orientation:

  • Enclosed by the pericardium and situated within the middle mediastinum.
  • Rests on the diaphragm with a cone-shaped base.
  • Positioned at an oblique angle of 40°.

Surfaces:

  • Base (Superior): Extends from the coronary sinus to the bifurcation of the pulmonary trunk, receiving drainage from six veins (four pulmonary veins and two venae cavae).
  • Sternal (Anterior) Surface: Formed by the right ventricle and conus arteriosus.
  • Diaphragmatic (Inferior) Surface: Directed downward and backward, resting on the central tendon of the diaphragm and formed by the ventricles.
  • Pulmonary (Lateral) Surface: Faces left, back, and up, primarily formed by the left ventricle with a small contribution from the left atrium.
  • Apex (Inferior Tip): Points forward and to the left, predominantly formed by the left ventricle.

Pericardium

The pericardium is a double-layered sac that surrounds and protects the heart. It consists of two layers:

  • Fibrous Pericardium (Outer Layer): A tough, fibrous sac that anchors the heart within the mediastinum and prevents excessive dilation.
  • Serous Pericardium (Inner Layer): A thin, double-layered membrane with a parietal layer lining the fibrous pericardium and a visceral layer (epicardium) adhering to the heart’s surface. The space between these layers contains pericardial fluid, which reduces friction during heartbeats.

Internal Morphology

Chambers:

  • Left Atrium: Cuboidal in shape with smooth walls, except for the pectinate muscles within the auricle. It features the oval fossa, a remnant of fetal circulation.
  • Right Atrium: Ovoid in shape and larger than the left atrium. Its walls are smooth, except for the pectinate muscles in the auricle.
  • Left Ventricle: Cone-shaped with thick, muscular walls and trabeculae carneae (irregular muscular ridges). Its walls are three times thicker than those of the right ventricle.
  • Right Ventricle: Triangular in shape with thinner walls compared to the left ventricle. It features trabeculae carneae and the moderator band, a muscular bundle that carries part of the conduction system.

Arterial System

Coronary Arteries

The coronary arteries supply oxygenated blood to the heart muscle. There are two main coronary arteries:

Left Coronary Artery:

  • Originates from the aorta and travels between the pulmonary trunk and the left atrium.
  • Divides into two main branches: the left anterior descending (LAD) artery and the left circumflex artery.
  • The LAD artery supplies blood to the anterior wall of the left ventricle and the interventricular septum.
  • The left circumflex artery supplies blood to the lateral wall of the left ventricle.

Right Coronary Artery:

  • Originates from the aorta and travels in the right coronary sulcus.
  • Supplies blood to the right atrium, right ventricle, and the posterior wall of the left ventricle.

Aorta

The aorta is the largest artery in the body and carries oxygenated blood from the heart to the systemic circulation. It has several segments:

  • Ascending Aorta: Originates from the left ventricle and gives rise to the coronary arteries.
  • Aortic Arch: Curves over the heart and gives rise to three major branches: the brachiocephalic trunk, left common carotid artery, and left subclavian artery.
  • Descending Aorta: Divided into the thoracic aorta and abdominal aorta, supplying blood to the organs and tissues of the thorax, abdomen, and lower limbs.

Carotid Arteries

The carotid arteries supply blood to the head and neck. There are two common carotid arteries, one on each side of the neck:

  • Left Common Carotid Artery: Originates from the aortic arch.
  • Right Common Carotid Artery: Originates from the brachiocephalic trunk.

Each common carotid artery divides into two branches:

  • External Carotid Artery: Supplies blood to the external structures of the head and neck, including the face, scalp, and thyroid gland.
  • Internal Carotid Artery: Supplies blood to the brain and eyes.

Subclavian Arteries

The subclavian arteries supply blood to the upper limbs, shoulders, and neck. They have three parts:

  • Prescalene Part: Located medial to the anterior scalene muscle.
  • Interscalene Part: Located posterior to the anterior scalene muscle.
  • Postscalene Part: Located lateral to the anterior scalene muscle and continues as the axillary artery.

Branches of the subclavian artery include the vertebral artery, internal thoracic artery, thyrocervical trunk, and costocervical trunk.

Axillary Artery

The axillary artery is a continuation of the subclavian artery and supplies blood to the shoulder and upper limb. Its branches include the subscapular artery, thoracoacromial artery, lateral thoracic artery, and anterior and posterior circumflex humeral arteries.

Subscapular Artery

The subscapular artery is a branch of the axillary artery and supplies blood to the muscles of the shoulder and back. Its branches include the thoracodorsal artery and the circumflex scapular artery.

Upper Thoracic Artery

The upper thoracic artery is a small branch of the axillary artery that supplies blood to the pectoral muscles and chest wall.

Conclusion

Understanding the anatomy of the heart and arterial system is crucial for comprehending cardiovascular health and disease. This guide provides a comprehensive overview of the key structures and their functions, serving as a valuable resource for students, healthcare professionals, and anyone interested in human anatomy.