THE HUMAN HEART
An educational presentation
Introduction to the Human Heart
The human heart is a vital organ responsible for pumping blood throughout the body.
Location: Thoracic cavity, between the lungs
Function: Circulates blood, providing oxygen and nutrients to tissues while removing waste.
Pericardium: A double-layered sac that surrounds and protects the heart.
Myogenic: Heartbeat originates within the heart muscle itself.
Double Circulation: Blood passes through the heart twice in each complete circuit.
Diagram: Introduction to the Human Heart
(Imagine a diagram here showing the location of the heart in the chest, the pericardium surrounding
it, and an overview of the double circulatory system.)
Structure of the Human Heart
The heart comprises several key structures that work together:
Chambers: Four chambers - two atria (right and left) and two ventricles (right and left).
Septa: Interatrial and interventricular septa separate the chambers.
Wall Thickness: Ventricles have thicker walls than atria; the left ventricle is the thickest.
Pericardium Layers: Fibrous, Parietal, and Visceral layers surround the heart.
Diagram: Structure of the Human Heart
(Imagine a diagram here clearly labeling the four chambers, the septa, and the different layers of the
pericardium.)
Major Blood Vessels
The heart is connected to the body via major blood vessels:
Vena Cava: Superior and inferior vena cava bring deoxygenated blood to the right atrium.
Pulmonary Artery: Carries deoxygenated blood from the right ventricle to the lungs.
Pulmonary Veins: Carry oxygenated blood from the lungs to the left atrium.
Aorta: Carries oxygenated blood from the left ventricle to the body.
Diagram: Major Blood Vessels
(Imagine a diagram here showing the heart with labeled vena cava, pulmonary artery, pulmonary
veins, and aorta, indicating blood flow direction.)
Valves of the Heart
Valves ensure unidirectional blood flow through the heart:
AV Valves: Atrioventricular valves (tricuspid and mitral) between atria and ventricles.
Semilunar Valves: Pulmonary and aortic valves at the exits of the ventricles.
Chordae Tendineae: Fibrous cords that anchor AV valves to papillary muscles.
Papillary Muscles: Prevent AV valves from prolapsing into the atria during ventricular
contraction.
Circulation Pathways
Blood follows two main circulatory pathways:
Double Circulation: Systemic and pulmonary circuits.
Pulmonary Circuit: Blood flows from the heart to the lungs and back to the heart (gas
exchange).
Systemic Circuit: Blood flows from the heart to the rest of the body and back to the heart
(nutrient/waste exchange).
Importance: Efficient oxygen delivery and waste removal from tissues.
Cardiac Cycle
The cardiac cycle involves alternating phases of contraction and relaxation:
Phases: Systole (contraction) and Diastole (relaxation).
Heart Sounds: 'Lub' (AV valves closing) and 'Dub' (semilunar valves closing).
Timing: Each cardiac cycle lasts approximately 0.8 seconds.
Regulation of Heartbeat
The heartbeat is regulated by intrinsic and extrinsic mechanisms:
Nodal Tissue: Sinoatrial (SA) node (pacemaker) and atrioventricular (AV) node.
Autonomic Control: Sympathetic (increase heart rate) and parasympathetic (decrease heart
rate) nervous systems.
ECG – Electrocardiogram
An ECG records the electrical activity of the heart:
Waves: P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave
(ventricular repolarization).
Clinical Significance: Detects abnormalities in heart rhythm, heart attack, etc.
Functions of the Heart
The heart performs several crucial functions:
Pumping: Drives blood circulation throughout the body.
Pressure: Generates blood pressure to ensure adequate tissue perfusion.
Supply/Removal: Delivers oxygen and nutrients; removes carbon dioxide and waste products.
Adjustment: Modulates cardiac output based on the body's needs (exercise, stress).
Quick Revision / Fun Facts
Heart Rate: Average resting heart rate is 60-100 beats per minute.
Blood Volume: Pumps approximately 5 liters of blood per minute at rest.
Beats per Day: Beats around 100,000 times per day.
Muscle Type: Cardiac muscle (involuntary, striated).
References
NCERT Biology Textbooks
CBSE Curriculum Materials
Medical Anatomy and Physiology Textbooks
Medical Diagram Databases
