Anatomy of the Thorax - Cardiovascular System

Anatomy of the Thorax

• Lectures for 2024-2025
• Writer: Amal Alismail & Mariyyah Al Bladi
• Reviewer: Maryam Alanazi
• Notes include doctor explanations, abbreviations, key information, and references.
• Specific notes for 221-223 are included.

Cardiovascular System

• Structure of Heart and Blood Vessels
• Theme 14, Part A
• Dr. Naheed Kausar, Assistant Professor
• Anatomy Division, Biomedical Sciences
• College of Medicine, King Faisal University
• Date: 12/22/2024

The Heart (Right and Left)

• The Right heart receives deoxygenated blood from the body and pumps it to the lungs.
• Superior Vena Cava (SVC) and Inferior Vena Cava (IVC) carry blood, connecting in the right atrium.
• The Left heart receives oxygenated blood from the lungs and pumps it around the body.
• Blood is pumped through the pulmonary artery to the lungs for oxygenation.
• The pulmonary veins carry oxygenated blood to the heart.
• The aorta distributes blood to the body.

Learning Objectives

• Orientation of the heart in the thoracic cavity
• Anatomy of the heart including layers, chambers, apex, base, and septum
• Structure and function of heart valves (semilunar, tricuspid, mitral) and papillary muscles
• Conducting system of the heart, including structure
• Blood vessels of the heart (coronary arteries and coronary sinus)
• Vagus nerve and sympathetic trunk effects on heart function and pericardial sac
• Pericardium structure and function

The Heart (General)

• The heart is a pump, roughly the size of a fist
• It has four chambers: two atria and two ventricles
• The chambers work in a coordinated cycle to pump blood in two different directions
• The cardiac cycle involves the pumping actions of two atrioventricular (AV) pumps.
• The cycle starts with a phase of ventricular filling and ends with a phase of ventricular emptying.

Heart as a Pyramid

• The heart is roughly pyramid-shaped in three dimensions.
• The heart has four faces, an apex, and a base.
• Anterior surface, diaphragmatic surface, left pulmonary surface, and right pulmonary surface are important anatomical regions.

Orientation of Heart in Thoracic Cavity

• The apex of the heart points downwards and slightly to the left, deep to the 5th intercostal space.
• The base of the heart is positioned opposite the apex, facing posteriorly, opposite T6-T9 when standing.

The Apex of the Heart

• Formed by the inferolateral part of the left ventricle.
• Typically located approximately 9 cm from the median plane.
• Mitral valve closure sounds are maximal at the apex beat.

The Base of the Heart

• Formed primarily by the left atrium
• Faces posteriorly
• Is separated from the vertebrae by the pericardium

The Cardiovascular System (How it Works)

• Deoxygenated blood enters the right atrium from the superior and inferior vena cava.
• The right atrium pumps the blood to the right ventricle.
• The right ventricle pumps the blood to the pulmonary artery, which carries it to the lungs.
• The lungs oxygenate the blood.
• Oxygenated blood returns to the left atrium via the pulmonary veins.
• The left atrium pumps the blood to the left ventricle.
• The left ventricle pumps the blood into the aorta, which distributes it throughout the body.

External Features of the Heart

• The heart has four borders.
• There are grooves that separate the chambers

Layers of Wall of Heart

• Endocardium, the innermost layer, lines the heart chambers and covers the valves.
• Myocardium, the middle layer, mostly cardiac muscle.
• Epicardium, the outermost layer (visceral pericardium), covers the heart and the beginning of the great vessels.

Valves of the Heart

• The heart has four valves: two atrioventricular (AV) valves (tricuspid and mitral) and two semilunar valves (pulmonary and aortic).
• Tricuspid valve is between the right atrium and the right ventricle
• Mitral valve is between the left atrium and the left ventricle
• Pulmonary valve is at the exit of the right ventricle
• Aortic valve is at the exit of the left ventricle
• Semilunar valves prevent backflow in the heart

Semilunar Valves

• Pulmonary and aortic valves, each with three cusps
• These valves do not have tendinous cords.

Heart Sounds

• Heart sounds are produced by the snapping shut of heart valves.
• Lub (1st sound) – closure of the AV valves
• Dub (2nd sound) – closure of the semilunar valves.

The Conducting System of the Heart

• SA node initiates the heartbeat.
• SA node signals travel through the heart and cause muscle contractions.

Arterial Supply to Heart

• Coronary arteries supply blood to the heart tissue.
• The right coronary artery and left coronary artery branch off the aorta and supply different parts of the heart.
• Multiple branches are present

Venous Drainage of the Heart

• The coronary veins collect deoxygenated blood from the heart
• Coronary sinus is the major vessel
• Several veins drain into the coronary sinus
• Anterior cardiac veins drain directly into the right atrium.

Autonomic Innervation

• The heart receives input from both the parasympathetic and sympathetic nervous systems.
• Vagus nerve influences the heart with parasympathetic stimulation.
• The sympathetic nervous system accelerates the heart and constricts the coronary arteries.

Pericardium

• A double-layered membrane surrounding the heart and the roots of the great vessels.
• Consists of fibrous and serous layers.
• Lubricates the heart and the tissues for movement and protection

The Pericardial Cavity

• A potential space between the parietal and visceral layers of the serous pericardium.
• Contains fluid for lubrication and protection of tissues in heart movement.

References

• Clinically Oriented Anatomy (8th ed.)