Circulatory System I

Circulatory System I

• The circulatory system comprises the heart, blood vessels, and blood. It's also called the cardiovascular system.
• The circulatory system's main function is transporting substances throughout the body.
• Blood acts as the liquid medium for transporting materials.
• Blood vessels direct blood flow to different destinations.
• The heart pumps blood to keep it flowing.

Functions of the Circulatory System

• The circulatory system is vital for transporting substances throughout the body.
• It includes the heart and blood vessels.

Pulmonary and Systemic Circuits

• The cardiovascular system has two main divisions: the pulmonary circuit and the systemic circuit.
• The pulmonary circuit carries blood to the lungs for gas exchange and returns it to the heart.
• The systemic circuit delivers blood to every body organ
• It includes other parts of the lungs and the heart wall itself.

The Right Half of the Heart

• The right half of the heart handles the pulmonary circuit.
• It receives blood from the body that has circulated.
• Blood is then pumped into the pulmonary trunk, a large artery.
• Oxygen-poor blood is directed to the lungs, where it releases carbon dioxide and picks up oxygen.
• It returns to the left side of the heart via pulmonary veins.

The Left Half of the Heart

• The left side of the heart handles the systemic circuit.
• It pumps blood into the aorta, the body's largest artery.
• Oxygen-rich blood is circulated to every organ in the body, and carbon dioxide is picked up.
• Blood returns to the heart through the largest veins (superior and inferior vena cava).

Position, Size, and Shape of the Heart

• The heart is located in the thoracic cavity's mediastinum, between the lungs and behind the sternum.
• About two-thirds of the heart is to the left of the body's midline.
• The broad superior part of the heart is called the base.
• The heart's inferior end is the apex, located above the diaphragm.

The Pericardium

• The heart is enclosed in a double-walled sac called the pericardium.
• The outer wall (pericardial sac) has a tough fibrous layer and a thin serous layer.
• The serous layer forms the epicardium, which covers the heart's surface.
• The space between the parietal and visceral membranes is the pericardial cavity.

The Heart Wall

• The heart wall consists of three layers:
• Epicardium (outer layer)
• Myocardium (middle, muscular layer)
• Endocardium (inner layer, lines the heart chambers)

The Chambers of the Heart

• The heart has four chambers: two atria (receiving chambers) and two ventricles (pumping chambers).
• The atria are located at the top of the heart, and ventricles at the bottom.
• Atria receive blood returning to the heart; ventricles pump blood out of the heart.

The Valves

• The atrioventricular (AV) valves regulate blood flow between the atria and ventricles (Right: tricuspid; Left: mitral).
• Semilunar valves regulate blood flow from the ventricles into the artery (Pulmonary and aortic).
• Valves ensure one-way blood flow through the heart.

Pathway of Blood Flow

• Blood flows through the heart in a specific pathway, divided into pulmonary and systemic circuits.
• Oxygen-poor blood enters the right side of the heart and travels to the lungs.
• Oxygenated blood returns to the left side of the heart and is pumped to the body.
• In normal heart function, the valves ensure blood flows in the correct direction.

Coronary Circulation

• Coronary arteries supply blood to the heart muscle itself.
• The coronary sinus returns deoxygenated blood to the heart's right atrium.

The Conduction System

• The heart's conducting system coordinates the heart chambers' rhythmic contractions.
• Pacemaker cells initiate the heartbeat and regulate the heart rate.
• Electrical signals spread through the heart's conducting tissues, causing the heart muscles to contract.
• The heart's conducting system coordinates the coordinated activity of the atria and ventricles, enabling proper pumping activity.