Heart Anatomy and Blood Flow Pathway

External and Internal Structures: The heart is a four-chambered muscular organ responsible for pumping blood throughout the body. It consists of two upper chambers called atria and two lower chambers called ventricles.
Layers of the Heart: The heart wall is composed of three layers: the epicardium (outermost), the myocardium (middle muscular layer), and the endocardium (innermost layer lining the chambers).
Pericardium: The heart is enclosed in a double-layered sac called the pericardium, which provides protection and lubrication.
Mediastinum: The heart is located in the mediastinum, the space between the lungs in the chest cavity.

Pathway of Blood Flow: Blood enters the right atrium from the body, travels through the tricuspid valve to the right ventricle, and is pumped through the pulmonary valve to the lungs for oxygenation. Oxygenated blood returns to the heart through the left atrium, passes through the mitral valve to the left ventricle, and is pumped out through the aortic valve to the body.
Pulmonary Circuit vs. Systemic Circuit: The pulmonary circuit involves the flow of blood between the heart and lungs, while the systemic circuit encompasses the flow of blood between the heart and the rest of the body.

Valves: The heart has four valves: the tricuspid valve, pulmonary valve, mitral valve, and aortic valve. These valves prevent backflow of blood and ensure unidirectional flow.
Supporting Structures: The valves are supported by chordae tendineae (tendinous cords) and papillary muscles, which prevent valve prolapse.
Electrical Activity: The heart's rhythmic contractions are controlled by its own electrical system. Specialized cells, called pacemaker cells, generate electrical impulses that travel through the heart, stimulating muscle contraction.

Cardiac Cycle: The cardiac cycle refers to the sequence of events that occur during one heartbeat, including atrial and ventricular contraction and relaxation.
Cardiac Output: Cardiac output is the volume of blood pumped by the heart per minute. It is influenced by heart rate and stroke volume.
Control of Cardiac Output: Cardiac output is regulated by factors such as the autonomic nervous system, hormones (e.g., epinephrine), and blood volume.

Cardiodynamics: This term refers to the forces involved in the circulation of blood. It encompasses the concepts of pressure, resistance, and flow.
Stroke Volume: Stroke volume represents the volume of blood ejected from the ventricle during each contraction.
End Diastolic Volume (EDV): The amount of blood in the ventricle at the end of diastole (relaxation).
End Systolic Volume (ESV): The amount of blood remaining in the ventricle after contraction.
Heart Rate: The number of times the heart beats per minute.
Venous Return: The rate at which blood flows back to the heart.

Blood Vessels: Blood vessels are the conduits for transporting blood throughout the body.
General Anatomy: Arteries carry oxygenated blood away from the heart, veins return deoxygenated blood to the heart, and capillaries facilitate the exchange of gases, nutrients, and waste products between blood and tissues.
Driving Force of Blood Circulation: The driving force for blood circulation is the pressure generated by the heart's contractions.
Physical Laws of Blood Flow & Pressure: Blood flow is governed by physical laws, including Poiseuille's Law: flow is proportional to the pressure gradient and inversely proportional to resistance.
Mean Arterial Pressure (MAP): The average arterial pressure over a single cardiac cycle, crucial for maintaining blood flow to tissues.

Factors that influence blood circulation: Cardiac output, blood volume, blood viscosity, and resistance within the blood vessels.
Resistance: Resistance to blood flow is affected by vessel diameter, vessel length, and blood viscosity.
Intrinsic Control of Blood Flow: Local mechanisms, such as changes in tissue metabolism, directly regulate blood flow within specific tissues.
Extrinsic Control of Blood Flow: The nervous system, hormones, and other systemic factors contribute to the regulation of blood flow.