WK 3 - 2 Structures of the cardiovascular system - location and structures

Cardiovascular System Overview

General Information

• The heart functions as a muscular pump to circulate blood throughout the body, a crucial process in maintaining homeostasis.

• It is divided into a right and left side, each serving distinct but complementary circulatory purposes:

  • Right Side: Pumps deoxygenated blood to the lungs via the pulmonary arteries, where carbon dioxide is exchanged for oxygen, essential for respiration and cellular function.

  • Left Side: Pumps oxygenated blood to the rest of the body through the aorta, supplying vital nutrients and oxygen to tissues and organs.

• The heart also helps maintain blood pressure through its rhythmic contractions, ensuring efficient blood flow. Additionally, it acts as an endocrine organ by releasing hormones such as atrial natriuretic peptide (ANP), which regulates blood volume and pressure.

Location of the Heart

• The heart is situated in the thoracic cavity, specifically within the mediastinum, resting between the lungs and above the diaphragm. It is enclosed by the pericardial cavity filled with serous fluid to reduce friction during heart movements.

• The pericardium surrounding the heart consists of:

  • Outer Fibrous Layer: Provides structural support and protection against external injury.

  • Inner Serous Membrane: Comprised of two layers:

    • Parietal Layer: Lines the fibrous pericardial sac, anchoring the heart to surrounding structures.

    • Visceral Layer: Directly covers the heart surface, also referred to as the epicardium, crucial for protecting heart tissue.

Anatomy of the Heart Wall

• The heart wall itself is composed of three distinct layers:

  • Outer Epicardium (Visceral Pericardium): A protective layer containing blood vessels and nerves that supply the heart.

  • Middle Myocardium: The thickest layer of the heart, made up of cardiac muscle tissue; its contraction is responsible for pumping blood. This layer adapts in thickness depending on the workload placed on the heart, such as during exercise.

  • Inner Endocardium: A smooth lining inside the heart chambers and valves, minimizing turbulence and ensuring efficient blood flow.

• The pericardial cavity contains serous fluid, which serves as a lubricant, reducing friction between heartbeats and preventing tissue damage.

Surface Anatomy of the Heart

• The heart has four main chambers:

  • 2 Atria (upper chambers): Receive blood returning to the heart; the right atrium receives deoxygenated blood from the body, and the left atrium receives oxygenated blood from the lungs.

  • 2 Ventricles (lower chambers): Pump blood away from the heart; the right ventricle sends blood to the lungs, while the left ventricle pumps it to the systemic circulation.

• Sulci: Grooves on the heart surface mark boundaries between the heart chambers:

  • Atrioventricular Sulci: Marks the boundary between the atria and ventricles, housing the coronary arteries.

  • Interventricular Sulcus: Divides the left and right ventricles, containing the interventricular artery that supplies blood to the ventricle muscles.

• The Apex of the Heart: Formed by the left ventricle, it is the pointed end of the heart that points downwards and rests on the diaphragm, playing a key role in the directional flow of blood.

Learning Outcomes

Students should be able to:

• Accurately describe the heart's location and its anatomical relationships within the thoracic cavity.

• Identify and explain the layers of the heart wall and pericardium, including their functions and significance.

• Recognize and describe the surface anatomy of the heart, including its chambers and associated structures, and understand how these contribute to its overall function in circulation.