Thorax and Heart Anatomy

Thorax Overview

• Thorax: The space within the thoracic cage, located inside the chest.
• Thoracic cage: Bones, muscles, skin, and other tissues that form the wall around the thorax.
• Superior thoracic aperture: Opening at the top of the thoracic cage, allowing structures to pass in and out.
• Inferior thoracic aperture: Opening at the bottom of the thoracic cage.
• Diaphragm: Separates the thoracic cavity from the abdominal cavity; dome-shaped when relaxed, flattens when contracted to aid breathing.
• The ribs and thoracic cage cover part of the abdomen.
• Thoracic cavity: Smaller than the entire thoracic cage due to the diaphragm extending upwards.
• Mediastinum: Region in the center of the thorax where the heart and great vessels are located; subdivided into superior and inferior parts.
• Pericardium: Connective tissue surrounding the heart, holding it in place and facilitating movement.

Heart Anatomy & Orientation

• The lungs are thin anteriorly; everything in the thorax is tightly packed.
• Heart location: Centrally located but projects to the left.
• Heart chambers: Four chambers: two atria (superiorly) and two ventricles (inferiorly).
• Atria: Receive blood. The Right atrium receives blood from the body; the left atrium receives blood from the lungs.
• Ventricles: Pump blood out. The Right ventricle pumps blood to the lungs; the left ventricle pumps blood to the body.
• The Left ventricle has a thicker muscular wall due to its larger job of pumping blood throughout the body.
• The right ventricle is the anterior chamber, making it more susceptible to damage from a blow to the sternum.

Great Vessels

• Great Vessels: Large blood vessels attached to the heart.
• Superior vena cava: Carries deoxygenated blood from the body into the right side of the heart.
• Aorta: The largest vessel leaving the left ventricle, distributing blood throughout the body; has important branches.
• Pulmonary trunk: Carries deoxygenated blood from the right ventricle to the lungs; splits into left and right pulmonary arteries.
• Pulmonary arteries: Transport deoxygenated blood to the lungs.
• Pulmonary veins: Carry oxygenated blood from the lungs back to the left atrium of the heart.
• The Left atrium is posterior to other structures.
• Inferior vena cava: Passes through the diaphragm and enters the right atrium.
• Brachiocephalic veins: Drain blood from the head, neck, and upper limbs; form the superior vena cava.
• Subclavian vein: Drains blood from the upper limb.
• Internal jugular vein: Drains blood from the head and neck.
• External jugular vein: Drains blood from the head and neck.
• Aorta Curve: Curves from right to left and from the middle of the thoracic cavity to the posterior wall.
• Aorta Branches: Gives off three branches: the brachiocephalic trunk, the left common carotid artery, and the left subclavian artery.
• Brachiocephalic trunk: Gives rise to the right common carotid artery and the right subclavian artery.
• Right Common carotid artery: Supplies blood to the brain, face, and neck.
• Subclavian artery: Supplies blood to the upper limb.
• Coronary arteries: The first branches of the aorta; supply blood to the heart muscle.

Lung Anatomy

• The Lungs fill most of the space in the thoracic cavity.
• The left lung is smaller due to the heart's position.
• The Right lung: Has three lobes which are the upper, middle, and lower lobes.
• The Left lung: Has two lobes which are the upper and lower lobes.
• Oblique fissure: Separates the upper and lower lobes of the left lung.
• Horizontal fissure & Oblique fissure: separates the lobes of the right lung
• The Lower lobes are located posteriorly; the upper lobes are anterior.

Airways

• Trachea: Main airway (windpipe) running from the larynx in the neck down into the thorax.
• Carina: Point where the trachea bifurcates into left and right main bronchi.
• Main bronchi: Divide into lobar bronchi (one for each lobe).
• Extensive branching: Airways branch extensively to maximize surface area for gas exchange.

Esophagus & Thoracic Aorta

• Esophagus location: Posterior to the trachea; muscular tube for transporting food.
• The Esophagus shifts to the left before passing through the diaphragm to reach the stomach.
• Thoracic aorta location: Posterior to the esophagus; descends through the thorax, sending off branches.
• Aorta sections: Ascending part, arch, and descending part (thoracic aorta).
• Intercostal arteries: Branches of the thoracic aorta that run around the thoracic cage with the ribs.

Posterior Thoracic Structures

• Much of the lung volume is located posteriorly, near the vertebral column.
• Azygos and hemiazygos veins: Collect blood from the intercostal spaces and drain into the superior vena cava.
• Azygos vein: Loops over structures going to and from the lungs before entering the superior vena cava.
• Diaphragm openings: The aorta, inferior vena cava, and esophagus pass through openings in the diaphragm.