Anatomy and Function of the Heart #1

The Heart - A Muscular Pump

• The heart is a powerful pump that circulates blood throughout the body, transporting nutrients, oxygen, waste, heat, hormones, and immune cells.
• The heart's primary function is to maintain pressure gradients, creating high pressure to pump blood out and low pressure to draw it back in.
• This pressure gradient is measured as blood pressure, reflecting the strain on arteries as the heart moves approximately 5 liters of blood at around 60 beats per minute.

Heart Anatomy

• The average adult heart is about the size of two fists clasped together and weighs approximately 250 to 350 grams.
• Situated in the mediastinum cavity between the lungs, it sits at an angle, with one end pointing towards the left hip and the other towards the right shoulder.
• The heart is encased in a double-walled sac called the pericardium, comprising the fibrous pericardium (outer layer) and the serous pericardium (inner layer).
• The serous pericardium contains two layers separated by fluid, acting as a lubricant to prevent friction during heartbeats.
• The heart wall consists of three layers: the epicardium (outer), myocardium (middle, composed of cardiac muscle), and endocardium (inner, thin epithelial tissue).

Heart Chambers and Valves

• The heart is divided into two sides by a septum, creating four chambers: two atria (superior, low pressure) and two ventricles (inferior, high pressure).
• Each chamber has a corresponding valve that acts as a one-way gate, allowing blood flow in one direction and preventing backflow.
• The "lub-DUB" sound heard when listening to a heartbeat results from the opening and closing of the heart valves.

Blood Circulation: Pulmonary and Systemic Loops

• Blood returning to the heart from the body enters the right atrium and is then pumped to the lungs via the pulmonary circulation loop.

• The right ventricle pumps deoxygenated blood through the pulmonary valve into the pulmonary artery, which branches into the lungs.

• In the lungs, carbon dioxide is exchanged for oxygen, and the now oxygenated blood returns to the heart through the pulmonary veins and enters the left atrium.

• The systemic loop begins in the left ventricle, where oxygenated blood is pumped into the aorta, the body's largest artery, delivering oxygen to body tissues.

• After delivering oxygen, the deoxygenated blood returns to the heart through the superior and inferior vena cava veins, entering the right atrium, completing the double-loop cycle.

Blood Pressure

• Systolic blood pressure measures the peak pressure created by the contracting ventricles during blood ejection.
• Diastolic blood pressure measures the pressure in the arteries when the ventricles are relaxed.
• Blood pressure that is too high or too low can indicate health problems and affect the body's ability to circulate oxygen.

Summary

• The heart, a vital organ, acts as a powerful pump maintaining pressure gradients to circulate blood throughout the body.
• Its anatomy, including chambers, valves, and layers, work in harmony to ensure efficient blood flow.
• The pulmonary and systemic circulation loops deliver oxygen to body tissues and remove waste products, maintaining homeostasis.
• Blood pressure, measured as systolic and diastolic pressures, reflects the health of the cardiovascular system and its ability to deliver oxygen.