Circulatory System I

Circulatory System I

• The circulatory system includes the heart, blood vessels, and blood.
• The cardiovascular system refers only to the heart and blood vessels.
• The circulatory system transports substances throughout the body in the blood.
• Blood is the liquid medium for transporting materials.
• Blood vessels route blood to destinations.
• The heart is the pump that keeps blood flowing.
• Without valves, more effort is needed to move blood.

Functions of the Circulatory System

• The circulatory system moves substances from one place to another.
• Blood carries substances like nutrients and oxygen throughout the body.
• The circulatory system is vital for gas exchange, removing carbon dioxide and delivering oxygen.

Pulmonary and Systemic Circuits

• The cardiovascular system has two major divisions: the pulmonary and systemic circuits.
• The pulmonary circuit carries blood to the lungs for gas exchange (oxygenation/carbon dioxide removal).
• The systemic circuit supplies blood to every body organ and picks up the waste products.

The Right Half of the Heart

• The right half of the heart supplies the pulmonary circuit.
• It receives blood from the body to be sent to the lungs.
• Blood unloads carbon dioxide and absorbs oxygen in the lungs.
• The oxygenated blood returns to the left side of the heart via pulmonary veins.

The Left Half of the Heart

• The left half of the heart supplies the systemic circuit.
• It receives oxygenated blood from the lungs.
• It pumps blood to the body's largest artery, the aorta.
• Branches of the aorta supply organs with oxygen and collect waste products.
• Blood returns to the right atrium via the vena cava.

Position, Size, and Shape of the Heart

• The heart is located in the thoracic cavity, specifically the mediastinum.
• It sits between the lungs and behind the sternum.
• Roughly two-thirds of the heart is found to the left of the sternum.
• The superior portion of the heart is the base, where major vessels connect.
• The bottom point of the heart is the apex.

The Pericardium

• The heart is enclosed in a double-walled sac called the pericardium.
• The outer wall (parietal pericardium) is a fibrous layer, tough and superficial.
• The inner layer (visceral pericardium) is a thin, serous layer.
• The space between the layers is the pericardial cavity.

The Heart Wall

• The heart wall has three layers: epicardium (outer), myocardium (middle, muscular), and endocardium (inner).
• The epicardium is a thin layer on the heart's outer surface.
• The myocardium is thick and muscular.
• The endocardium is a thin layer lining the heart chambers.

The Chambers of the Heart

• The heart has four chambers: two atria (thin-walled receiving chambers) and two ventricles (pumping chambers).
• The atria receive blood entering the heart.
• The ventricles pump blood away from the heart.

The Valves

• Atrioventricular (AV) valves (tricuspid and mitral) control blood flow between atria and ventricles.
• Semilunar valves (pulmonary and aortic) control blood flow from the ventricles to the arteries.
• Valves prevent backflow during heart contractions.

Pathway of Blood Flow

• Blood flows from the body to the right atrium through the vena cava.
• Blood then enters the right ventricle and goes to the lungs through pulmonary artery. Oxygenated blood returns to the left atrium and then to the left ventricle.
• From the left ventricle, blood is pumped out to the body via the aorta.

Coronary Circulation

• Coronary circulation supplies blood to the heart muscle itself.
• The coronary arteries branch off the aorta and supply oxygenated blood to the heart muscle.
• Blood then returns to the heart through the coronary veins, which drain into the coronary sinus.

Conduction System

• The cardiac conduction system initiates and spreads electrical signals that cause heart contractions.
• The SA node is the pacemaker, generating electrical impulses.
• Impulses travel through specialized pathways to stimulate contractions in coordinated fashion in the atria and ventricles.

Explore the functions and components of the circulatory system, including the heart, blood vessels, and blood. This quiz covers the cardiovascular system's role in transporting nutrients and gases throughout the body, as well as the differences between pulmonary and systemic circuits.