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Human Heart

December 2, 2024 • Science

swaraj barik
swaraj barik

#poet #writer I live with pride and self-respect.Writing is not my profession but my addiction . Medical Consultant,NursingStaff onlinemedical tutor 

Brief information about the Human Heart

Human Heart by swaraj barik Introduction to the Human Heart The heart is a muscular organ that is situated in the front of the chest. It pumps blood all through the body in a process called circulation. Apart from the heart, the blood vessels and blood as a unit constitute the cardiovascular system. The human heart is one of the most important organs responsible for sustaining life. It is a muscular organ with four chambers. The size of the heart is the size of about a clenched fist. The human heart functions throughout a person's lifespan and is one of the most robust and hardest working muscles in the human body. Besides humans, most other animals also possess a heart that pumps blood throughout their bodies. Even invertebrates such as grasshoppers possess a heart like pumping organ, though they do not function the same way a human heart does.Position of Heart & The Function of Heart The human heart is located between the lungs in the thoracic cavity, slightly towards the left of the sternum (breastbone). It is derived from the embryonic mesodermal germ layer. The function of the heart in any organism is to maintain a constant flow of blood throughout the body. This replenishes oxygen and circulates nutrients among the cells and tissues. Following are the main functions of the heart: One of the primary functions of the human heart is to pump blood throughout the body. Blood delivers oxygen, hormones, glucose and other components to various parts of the body, including the human heart. The heart also ensures that adequate blood pressure is maintained in the body There are two types of circulation within the body, namely pulmonary circulation and systemic circulation.Structure of the Human Heart The human heart is about the size of a human fist and is divided into four chambers, namely two ventricles and two atria. The ventricles are the chambers that pump blood and the atrium are the chambers that receive blood. Among these both the right atrium and ventricle make up the "right heart," and the left atrium and ventricle make up the "left heart." The structure of the heart also houses the biggest artery in the body the aorta. The right and the left region of the heart are separated by a wall of muscle called the septum. The right ventricle pumps the blood to the lungs for re-oxygenation through the pulmonary arteries. The right semilunar valves close and prevent the blood from flowing back into the heart. Then, the oxygenated blood is received by the left atrium from the lungs via the pulmonary veins. Read on to explore more about the structure of the heart.External Structure of Heart Pericardium The human heart is situated to the left of the chest and is enclosed within a fluid-filled cavity described as the pericardial cavity. The walls and lining of the pericardial cavity are made up of a membrane known as the pericardium. The pericardium is a fibre membrane found as an external covering around the heart. It protects the heart by producing a serous fluid, which serves to lubricate the heart and prevent friction between the surrounding organs. Apart from the lubrication, the pericardium also helps by holding the heart in its position and by maintaining a hollow space for the heart to expand itself when it is full. The pericardium has two exclusive layers- Visceral Layer: It directly covers the outside of the heart. Parietal Layer: It forms a sac around the outer region of the heart that contains the fluid in the pericardial cavity.Structure of the Heart Wall The heart wall is made up of 3 layers, namely: Epicardium - Epicardium is the outermost layer of the heart. It is composed of a thin-layered membrane that serves to lubricate and protect the outer section. Myocardium - This is a layer of muscle tissue and it constitutes the middle layer wall of the heart. It contributes to the thickness and is responsible for the pumping action. Endocardium - It is the innermost layer that lines the inner heart chambers and covers the heart valves. Furthermore, it prevents the blood from sticking to the inner walls, thereby preventing potentially fatal blood clots.Internal Structure of Heart The internal structure of the heart is rather intricate with several chambers and valves that control the flow of blood. Chambers of the Heart Vertebrate hearts can be classified based on the number of chambers present. For instance, most fish have two chambers, and reptiles and amphibians have three chambers. Avian and mammalian hearts consists of four chambers. Humans are mammals; hence, we have four chambers, namely: Left atrium Right atrium Left ventricle Right ventricle Atria are thin and have less muscular walls and are smaller than ventricles. These are the blood-receiving chambers that are fed by the large veins. Ventricles are larger and more muscular chambers responsible for pumping and pushing blood out into circulation. These are connected to larger arteries that deliver blood for circulation. The right ventricle and right atrium are comparatively smaller than the left chambers. The walls consist of fewer muscles compared to the left portion, and the size difference is based onBlood Vessels In organisms with closed circulatory systems, the blood flows within vessels of varying sizes. All vertebrates, including humans, possess this type of circulation. The external structure of the heart has many blood vessels that form a network, with other major vessels emerging from within the structure. The blood vessels typically comprise the following: Veins supply deoxygenated blood to the heart via inferior and superior vena cava, and it eventually drains into the right atrium. Capillaries are tiny, tube-like vessels which form a network between the arteries to veins. Arteries are muscular-walled tubes mainly involved in supplying oxygenated blood away from the heart to all other parts of the body. Aorta is the largest of the arteries and it branches off into various smaller arteries throughout the body.Valves . Valves are flaps of fibrous tissues located in the cardiac chambers between the veins. They ensure that the blood flows in a single direction (unidirectional). Flaps also prevent the blood from flowing backwards. Based on their function, valves are of two types: Atrioventricular valves are between ventricles and atria. The valve between the right ventricle and right atrium is the tricuspid valve, and the one which is found between the left ventricle and left atrium is known as the mitral valve. Semilunar valves are located between the left ventricle and the aorta. It is also found between the pulmonary artery and the right ventricle.Types of Circulation Pulmonary circulation is a portion of circulation responsible for carrying deoxygenated blood away from the heart, to the lungs and then bringing oxygenated blood back to the heart. Systemic circulation is another portion of circulation where the oxygenated blood is pumped from the heart to every organ and tissue in the body, and deoxygenated blood comes back again to the heart. Now, the heart itself is a muscle and therefore, it needs a constant supply of oxygenated blood. This is where another type of circulation comes into play, the coronary circulation. Coronary circulation is an essential portion of the circulation, where oxygenated blood is supplied to the heart. This is important as the heart is responsible for supplying blood throughout the body. Moreover, organs like the brain need a steady flow of fresh, oxygenated blood to ensure functionality. The circulatory system plays a vital role in supplying oxygen, and nutrients and removing carbon dioxide and other wastes from the body. Let us gain a deeper insight into the various anatomical structures of the heart:thank you . check out more topic

The Cardiovascular System: A Lifeline of Circulation

The cardiovascular system is the body’s central transport network, comprising:

Cardio (Heart): Acts as a pump, ensuring a continuous flow of blood.

Vascular (Blood Vessels): A network of conduits guiding blood throughout the body

Dual Circulation of the Heart

1. Pulmonary Circulation: Transports deoxygenated blood from the heart to the lungs and returns oxygen-rich blood.

2. Systemic Circulation: Delivers oxygenated blood to tissues and brings back deoxygenated blood.

The Heart: Guardian of Homeostasis

The heart sustains balance in the body by ensuring oxygen and nutrient supply while expelling waste products.

Fascinating Heart Facts

Beats 100,000 times daily, totaling ~35 million beats annually.

Circulates 5 liters of blood per minute, ensuring tissue nourishment.

Pumps 14,000 liters per day, traversing 120,000 km of blood vessels.

The scientific study of the heart is called Cardiology.

Homeostasis refers to the body's ability to maintain stable internal conditions.

Heart Anatomy: The Powerhouse of Circulation

A cone-shaped muscular organ, about 10 cm long and roughly the size of a clenched fist.

Weight:

Men: ~310 g

Women: ~225 g

Location: Resides in the mediastinum within the thoracic cavity.

Neighboring Structures

Inferiorly: Apex

Superiorly: Aorta, Pulmonary Artery, Superior Vena Cava

Posteriorly: Esophagus, Trachea, Thoracic Vertebrae

Laterally: Lungs

Anteriorly: Sternum, Ribs, Intercostal Muscles

Layers of the Heart Wall

1. Endocardium (Inner Layer):

Lines heart chambers and valves.

Composed of smooth epithelial tissue.

2. Myocardium (Middle Layer):

Thick, muscular layer responsible for contractions.

Composed of involuntary, striated cardiac muscle.

3. Epicardium (Outer Layer):

Protective covering with two layers:

Outer Sac: Fibrous tissue.

Inner Sac: Serous membrane for lubrication.

Internal Heart Structure

The heart is divided into four chambers:

1. Right Atrium: Receives deoxygenated blood from the body.

2. Left Atrium: Collects oxygenated blood from the lungs.

3. Right Ventricle: Pumps deoxygenated blood to the lungs.

4. Left Ventricle: Distributes oxygen-rich blood to the body.

Valves Ensuring One-Way Flow

Atrioventricular (AV) Valves:

Tricuspid Valve (Right side)

Mitral Valve (Left side)

Semilunar Valves:

Pulmonary Valve (Directs blood to lungs)

Aortic Valve (Regulates flow to the body

Pathway of Blood Through the Heart

Deoxygenated Blood Flow:

1. Enters Right Atrium via Superior & Inferior Vena Cava.

2. Moves through the Tricuspid Valve into the Right Ventricle.

3. Ejected through the Pulmonary Valve into the Pulmonary Artery, reaching the lungs.

Oxygenated Blood Flow:

1. Returns via Pulmonary Veins into the Left Atrium.

2. Passes through the Mitral Valve into the Left Ventricle.

3. Propelled through the Aortic Valve into the Aorta, supplying the body.

The Heart’s Own Blood Supply

Coronary Arteries: Deliver oxygen and nutrients to heart tissues.

Venous Drainage: Blood from the heart muscle drains into the Coronary Sinus, which empties into the Right Atrium.

Electrical Conduction: The Heart’s Rhythmic Pulse

The heart beats through an intricate electrical conduction system, ensuring coordinated contractions.

SA Node (Pacemaker): Triggers the heartbeat.

AV Node: Delays impulses for proper ventricular filling.

Bundle of His & Purkinje Fibers: Distribute impulses for contraction.

The Cardiac Cycle: Phases of a Heartbeat

1. Atrial Systole (0.1 sec): Atria contract, pushing blood into ventricles.

2. Ventricular Systole (0.3 sec): Ventricles contract, propelling blood forward.

3. Complete Cardiac Diastole (0.4 sec): The heart relaxes, refilling with blood.

Heart Sounds (Auscultation Clues):

Lub (S1): Closure of Tricuspid & Mitral Valves (AV valves).

Dup (S2): Closure of Aortic & Pulmonary Valves (Semilunar valves).

Electrocardiogram (ECG): Mapping Electrical Activity

P Wave: Atrial depolarization (SA node firing).

QRS Complex: Ventricular depolarization.

T Wave: Ventricular repolarization.

Cardiac Output (CO): Measuring Heart Performance

Formula:

CO = Stroke Volume × Heart Rate

Stroke Volume: Amount of blood pumped per beat (~70 ml).

Factors Influencing Cardiac Output

Increase: Sympathetic stimulation, adrenaline, exercise.

Decrease: Parasympathetic activity, blood loss, dehydration.

Blood Pressure (BP) Regulation

Formula:

BP = CO × Peripheral Resistance

Systolic BP (~120 mmHg): Maximum arterial pressure during ventricular contraction.

Diastolic BP (~80 mmHg): Pressure during ventricular relaxation.

Regulatory Mechanisms:

Neural Control: Baroreceptors adjust heart rate.

Hormonal Influence: Adrenaline and aldosterone modify vessel tone.

Blood Vessels: The Circulatory Network

Types of Blood Vessels:

1. Arteries & Arterioles: Transport oxygenated blood away from the heart.

2. Capillaries: Micro-vessels facilitating nutrient and gas exchange.

3. Veins & Venules: Return deoxygenated blood to the heart

Collateral Circulation & Anastomoses:

Anastomoses: Natural bypass routes ensuring blood flow in case of blockage.

Found in the brain, heart, hands, feet, and joints.

Common Cardiovascular Disorders

Coronary Artery Disease (CAD):

Cause: Plaque buildup in arteries (Atherosclerosis).

Risk Factors: Smoking, hypertension, diabetes, high cholesterol, obesity, genetics.

Impact: Reduced blood supply to the heart, leading to angina or myocardial infarction (heart attack).

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