The Human Heart and Circulatory System

Study Notes

The Human Heart

The heart is protected by the rib cage and sternum, with lungs located on either side
The heart pumps oxygen-poor blood through the lungs and oxygen-rich blood to the rest of the body
Deoxygenated blood enters the heart through the inferior and superior vena cava
Oxygenated blood returns to the heart through the four pulmonary veins
The heart receives blood supply from the coronary arteries, which are embedded in the epicardial adipose tissue
Coronary arteries carry oxygenated blood to the heart
Coronary sinus carries deoxygenated blood back into the heart
A heart attack occurs when coronary arteries become blocked or narrowed, preventing blood flow and oxygen delivery to heart muscles

Blood Vessels and Valves

The aorta is the main artery that pumps oxygen-rich blood to the body
The pulmonary artery carries deoxygenated blood to the lungs
The heart contains four valves:
- Aortic: Prevents backflow from the aorta to the left ventricle
- Pulmonary: Prevents backflow from the pulmonary artery to the right ventricle
- Mitral: Prevents backflow from the left ventricle to the left atrium
- Tricuspid: Prevents backflow from the right ventricle to the right atrium

Cardiac Cycle: Heart Pumping Action

The heart contracts (systole) to pump blood and relaxes (diastole) to fill with blood
Atrial contraction pumps blood into the ventricles
Ventricular contraction pumps blood into the pulmonary artery (right ventricle) or aorta (left ventricle)
The contraction of the ventricular muscles creates pressure to open the valves, allowing blood to flow -Tricuspid valve is open during right atrial contraction, pulmonary valve is open during right ventricular contraction, mitral valve is open during left atrial contraction, aortic valve is open during left ventricular contraction

Electrical Conduction System

The heart's electrical system initiates and regulates its pumping action
The sinoatrial (SA) node, the heart's natural pacemaker, generates electrical impulses at 60-80 beats per minute
The impulses are propagated through internodal tracks to the atria, causing atrial contraction
The atrioventricular (AV) node delays the impulse, allowing the ventricles to fill with blood before contracting
The bundle of His transmits the impulse to the right and left bundle branches, then to the Purkinje fibers, which rapidly propagate the impulse to the ventricular muscle cells
If the SA node fails, the AV node can generate 40-60 impulses per minute
If both SA and AV nodes fail, the bundle of His can produce 20-40 impulses per minute

Electrocardiogram (ECG)

An ECG measures the electrical activity of the heart
The P wave represents atrial depolarization (contraction)
The QRS complex represents ventricular depolarization (contraction)
The T wave represents ventricular repolarization (relaxation)

Pericardium

The pericardium is a protective sac that surrounds the heart
It consists of two layers with a fluid-filled space between them
The fluid acts as a lubricant, preventing friction during heart contractions

Systemic vs. Pulmonary Circulation

The systemic circulation transports oxygen-rich blood from the heart to the body and back, while the pulmonary circulation transports deoxygenated blood from the heart to the lungs and back
The left ventricle has a thicker muscle layer than the right ventricle because it pumps blood to the entire body, requiring more force

Description

Explore the intricate structure and function of the human heart and blood vessels in this quiz. Understand how blood circulates, the role of coronary arteries, and the importance of heart valves. Test your knowledge on heart health and potential conditions like heart attacks.