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heart- anatomy physiology and its function

What is the circulatory system?

The human circulatory system also called the blood vascular system consists of a heart, arteries, veins, capillaries, and blood. size of the heart is a clenched fist. It is protected by a double-walled membranous bag called the pericardium, which enclosed the pericardial fluid. 

In the human circulatory system, the heart acts as a pump. The arteries, veins, and capillaries act as a pipe through which blood flows. There are 3 types of blood vessels of the human body, arteries, veins, and capillaries.

Heart definition 

The human heart is a triangular-shaped, muscular organ, located in the chest cavity (thoracic
cavity) between the 2 lungs, slightly tilted towards the left side, and made up of special muscular tissues called cardiac muscle, these muscles work continuos contraction and relaxation without any rest. it is protected by the rib cage. the main function of the heart is to receive and pump blood throughout the body.


The human heart continuously beats up producing a lube-dub sound called heartbeat. in normal healthy adults, the heartbeats 72 times in a minute. 

Location of heart

Human heart located behind the ribcage and between the lungs, a little to the left of the middle of the body. 

Compartment (chambers) of the heart 

The heart has 4 compartments (chambers) inside it. The walls of ventricles
are much thicker than that of the atria

 Chambers Left Right Our heart has 4 chambers
 Upper Chambers Left Artia Right Artia The Upper 2 chambers (Artia)are small and, receives blood from the two main veins.
 Lower Chambers Left ventricle Right Ventricle. while the lower 2 chambers (Ventricles) are bigger.
transport blood to the entire body and the lungs.

The upper 2 chambers of the heart are called atria (singular atrium).

 Interatrial septum Inter-ventricular septum Atrioventricular septum.
 A thin wall, interatrial septum separates
 the right and the left atria, 
A thick-walled separates the left and the right ventricles. The atrium and the ventricle of the same side are also separated by a thick fibrous tissue known as the atrioventricular septum.

through which the two chambers of the same side are connected. 

The valves of the heart 

Purposes of the heart valve

The left atrium is connected to the left ventricle through a valve. and the right atrium is connected to the right ventricle through another valve. these valves prevent the backflow of blood into the atria when the ventricles contract to blood out of the heart to the rest of the body this is because when the ventricles contract, the valvesV1, and V2 close automatically.

All the atria and ventricles of the heart contract and relax (expand) at a fixed time and make the heart behave like a pump. ventricles have to pump blood into various organs with high pressure, they have thicker walls than atria. 

The outer layer of the heart is called the pericardium protects the muscular heart. The chambers of the heart are separated by a partition called the septum.

 Tricuspid valve  Bicuspid valve Semilunar valves.  Importance of heart valves
The opening between the right atrium and
the right ventricle is guarded by a valve,
consists of 3 muscular flaps or cusps.
 guards the opening between the left atrium and the left ventricle.  The openings of the right and the left ventricles into the pulmonary artery and the aorta respectively with the semilunar valves. The valves in the heart allow the flow of blood only in one direction.

These valves prevent any backward flow.

Cardiac muscles

 Nodal tissue Sino-atrial node (SAN) Atrioventricular node (AVN).  Purkinje fibers
 A specialized cardiac musculature called the nodal tissue is distributed in the heart. A patch of nodal tissue is present in the right upper corner of the right atrium called the sino-atrial node (SAN).  A mass in the lower-left corner of the right atrium close to the atrioventricular septum called the atrioventricular node (AVN).  A bundle of nodal fibers, atrioventricular bundle (AV bundle) continues from the AVN which passes through the atrioventricular septa to emerge on the top of the interventricular septum and immediately divides into a right and left bundle.

These branches give rise to minute fibers throughout the ventricular musculature of the respective sides and are called Purkinje fibers. 

The sino-atrial node is called the pacemaker of our heart. Why

The nodal musculature has the ability to generate action potentials without any external stimuli, i.e., it is auto excitable. 

However, the number of action potentials that could be generated in a minute varies at different parts of the nodal system. 

The SAN can generate the maximum number of action potentials and is responsible for initiating and maintaining the rhythmic contractile activity of the heart (average 72 beats min in a minute).  Therefore, it is called the pacemaker. 

blood vessels of the heart

 Superior vena cava Inferior vena cava Pulmonary veinsPulmonary artery Aorta
 It is a large vein that brings deoxygenated blood from the upper parts of the body ( head, shoulders). It is a large vein that brings deoxygenated blood from the lower part of the body (trunk, legs).they bring oxygenated blood from the left and right lungs and open into the left auricle. It is carrying the deoxygenated blood to the lungs for oxygenation. leaves the right ventricle. It leaves the left ventricle. carries oxygenated blood to the rest of the body.

Pulmonary circulation
transports blood only between the heart and the lungs.

Systemic circulation
transports blood between the heart and the entire body.

Mechanism of heart:

  1. When the muscles of the four chambers of the heart are relaxed, the pulmonary vein brings the oxygenated blood from the lungs into the left atrium of the heart.
  2. When the left atrium contracts, the oxygenated blood is pushed into the left ventricle through valve V1.
  3. When the left ventricle contracts, the oxygenated blood is forced into the main artery called the aorta.
  4. The main artery carries blood to all the organs of the body. And the oxygenated blood passes through the capillaries of the body organs, then it gives oxygen to the body cells and blood loses oxygen (De-oxygenated). The blood also gives the digested food and other dissolved materials to the body this time carbon dioxide produced as waste material during respiration enters into the blood. The De-oxygenated blood from the organs enters into the main vein called vena cava. The main vein carries the De-oxygenated blood to the right atrium of the heart.
  5. When the right atrium contracts, De-oxygenated blood pushed into the right ventricle through valve V2.
  6. When the right ventricle contracts, the De-oxygenated blood is pumped into the lungs through the pulmonary artery. In the lungs, De-oxygenated blood releases its carbon dioxide and absorbs fresh oxygen from the air, so blood becomes oxygenated This oxygenated blood is again sent to the left atrium of the heart by the pulmonary vein for circulation in the body.

Circulate the blood in the human body :

Double circulation: a circulatory system in which the blood travels twice through the heart in one complete cycle of the body is called double circulation.

Pulmonary circulation: in the human circulation system the pathway of blood from the heart to the lungs and back to the heart is called pulmonary circulation.

Systemic circulation: the pathway of blood from the heart to the rest of the body and back to the heart is called systemic circulation.

The function of the heart:

The human circulatory system transports food and oxygen to various parts of the body and brings back carbon dioxide to the lungs. 

The human heart performs the following function, they are,

💗 transport nutrient,

💗 transport oxygen,

💗 transport hormones,

💗 removal of metabolic waste material, such as carbon dioxide, nitrogenous waste.

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