Human Heart

Overview

The human heart is pumping organ in the body which pumps the blood through the blood vessels. It is a muscular organ. The blood pumps by the heart provide oxygen and nutrients to the body organs as well as remove metabolic wastes from the tissues of the body.

It is divided into four chambers
Right and left atria
Right and left ventricle.

The chambers in some animals have different numbers. For example, fish has two chambers while the reptile has 3 chambers.

It is covered by a protective sac which is known as the pericardium.

1.  Epicardium
2.  Myocardium
3.  Endocardium

The rhythmicity of the human heart is under the control of pacemaker cells which are named as sinoatrial node. The heart receives oxygenated blood from the systemic circulation and from there it is pumped into the pulmonary circulation and becomes oxygenated in the lungs.

The oxygenated blood comes back to the heart. The heart then pumped the oxygenated blood into the aorta.

In the resting stage, the heart beats at a rate of  70 beats per minute. The rate may be increased in exercise or in various other activities.

The diseases which affect the heart are the leading cause of deaths.

 

What is the location of the human heart?

The human heart is situated in the middle mediastinum at the level of 5 to 8 thoracic vertebrae ( T5 to T8). The pericardium a protective sac surrounds the heart and attached to the mediastinum.

The front side of the heart sits behind the sternum while the back surface lies near the vertebral column.

The upper of the heart is located at the level of third costal cartilage and provides an attachment point for many large blood vessels.

The Apex of the heart lies between the junction of fourth and fifth ribs near their articulation with cartilages.

 

What is the shape of the human heart?

The heart is cone-shaped. The base of the heart positioned upwards and appearing down to the Apex.

Mass.          250-350 grams
Length.      12 cm
Width.        8 cm
Thickness. 6 cm

 

What are the chambers of the human heart?

There are four chambers in the human heart which are,

1. Right atrium
2.  Left atrium
3.  Right ventricle
4.  Left ventricle

The atria opens into the ventricles of the heart via atrioventricular valves.

The ventricles of the heart are separated by the interventricular septum.

The atria and ventricles are separated by an atrioventricular septum.

 

What are the valves present in the human heart?

There are four valves in the heart. Two valve lies between atrium and ventricles. The remaining two valves are present in the ventricles one in each ventricle at the exit.

The valve which is present between the right atrium and right ventricle is known as a tricuspid valve and it has three cusps. The cusps are attached to the chordae tendinae and three papillary muscles.

The valve which is present between the left atrium and left ventricle is known as the Mitral valve or bicuspid valve and it has two cusps.

The other valves are present in ventricles and these are a pulmonary valve and aortic valve. These both the valve has three cusps.

 

Heart wall

The human heart wall is made up of three layers the endocardium, endocardium, and epicardium.

These layers are surrounded by a protective double-membrane sac known as the pericardium.

The endocardium is the innermost layer that covers the valves and chambers.

The myocardium is the middle layer which is cardiac muscles surrounded by a framework of collagen.

 

What is pericardium?

The pericardium is a protective sac that surrounds the human heart. The pericardium has two layers an outer layer and an inner layer.

The outer layer is known as the fibrous pericardium while the inner layer is known as the serous pericardium.

The part of the inner layer of the pericardium which is attached to the outer layer of the pericardium is called the parietal pericardium.

The part of the serous pericardium which is attached to the heart is called visceral pericardium.

The function of the pericardium is to lubricate its movement against the structures within the chest to keep the position of the heart stabilized.

 

What is coronary circulation?

The heart is a pumping organ and it needs to be supplied with oxygen and nutrients. This task is done through coronary circulation.

Coronary circulation includes arteries, veins, and lymphatic’s.

The two main arteries present in the coronary circulation are the right coronary artery and the left coronary artery.

The veins involved in the coronary circulation are a great cardiac vein, posterior cardiac vein, middle cardiac vein, and small cardiac vein. These veins drain into the coronary sinus which then drains into the right atrium.

The anterior cardiac vein is also involved in the coronary circulation and it drains directly into the right atrium.

The lymphatic involved in the coronary circulation is plexuses which are present beneath each of the three layers of the heart.

 

nerve supply of the human heart

The nerve supply comes from the cardiac plexus which is made by the vagus nerve and nerve arising from the sympathetic trunk.

Vagus nerve acts to decrease the heart rate.

Nerves from the sympathetic trunk act to increase the heart rate.

The function of these nerves is to influence not to control the heart rate.

 

physiology of the human heart

It pumps the blood into the vessels of the circulatory system and maintains a continuous flow of blood throughout the body.

The circulation of blood in the body is achieved by two types of circulation which are systemic circulation and pulmonary circulation.

In the systemic circulation, the blood is pumped into the body while in the pulmonary circulation the blood is pumped into the lungs for oxygenation.

Both type of circulation also includes the flow of blood from the body and lungs to the heart.

The right heart receives deoxygenated blood while the left heart receives the oxygenated blood.

To get nutrients and oxygen the heart gets its supply from the coronary circulation.

 

What is the cardiac cycle?

The sequence of events that occurs when the heart contract or relaxes is known as the cardiac cycle.

 

What is cardiac output?

The amount of blood which is pumped by each ventricle in one minute is known as cardiac output.

The average cardiac output ranges from 4 to 8 liters per minute.

 

Electrical conduction

Sinoatrial nodes established a normal heartbeat by creating electric signals which travel through the heart and cause the contraction of the heart muscles.

The signals which are created by the sinoatrial nodes then travel along with the bundle of his to the right and left bundle branches.

The signal from the bundle branches is carried by Purkinje fibers into the heart muscles.

 

Heart sounds

The heart has two sounds which are known as S1 and S2. S1 described as lub produced when the atrioventricular valve closes.

S2 described as dub produced when the semilunar valves close.

Other heart sounds are also present which are known as S3 and S4.

S3 and S4 give rise to gallop rhythms.

 

Heart conditions

Coronary artery disease
Stable angina pectoris
Unstable angina pectoris
Myocardial infarction
Arrhythmia
Congestive heart failure
Cardiomyopathy
Pericarditis
Pericardial effusion
Atrial fibrillation
Pulmonary embolism
Heart valve disease
Heart murmur
Endocarditis
Mitral valve prolapse
Sudden cardiac death
Cardiac arrest

Heart tests

To check heart health various heart tests are used some of them are

Electrocardiogram
Echocardiogram
Cardiac stress test
Cardiac catheterization
Holter monitor
Event monitor

Heart treatments

Exercise
Angioplasty
Percutaneous coronary intervention
Coronary artery stenting
Thrombolysis
Lipid-lowering agents
Diuretic
Beta-blockers
ACE inhibitors
Aspirin
Clopidogrel
Antiarrhythmic medications
AED
ICD
Pacemaker