๐๐ฉ๐ง๐ช๐๐ฉ๐ช๐ง๐ ๐ค๐ ๐ฉ๐๐ ๐๐๐๐ง๐ฉ
The heart is divided into the left and right side by partitions called septa (singular septum).
The interatrial septum separates the two upper chambers, called atria (from atri/o, meaning "upper chambers").
The interventricular septum separates the two lower chambers, called ventricles (from ventricul/o, meaning "lower chamber).
๐๐๐ ๐๐๐๐ง๐ฉ ๐พ๐ค๐ฃ๐จ๐๐จ๐ฉ๐จ ๐ค๐ ๐๐ค๐ช๐ง ๐พ๐๐ก๐ก ๐๐๐ฎ๐๐ง๐จ:
The endocardium (from endo- + cardi/o +ium, meaning "inner layer of the heart") is formed by endothelial cells, and it lines the interior of the heart chambers and valves.
The myocardium (from my/o + cardi/o + -ium, meaning "heart muscle") is the muscular middle layer of the heart that consists ofheart muscle cells.
The epicardium (from epi- + cardi/o + -ium, meaning "outer layer of the heart") is formed by epithelial cells, and forms the outer cell layer of the heart.
The pericardium (from peri- + cardi/o +-ium, meaning "surrounding the heart") is a membranous sac that surrounds the heart. It consist of two layers called the visceral pericardium (adheres to the epicardium) and parietal pericardium (the outer coat). The space between these two layers is called pericardial cavity and it contains pericardial fluid.
๐๐๐๐ง๐ฉ ๐พ๐๐๐ข๐๐๐ง๐จ ๐๐ฃ๐ ๐๐๐ก๐ซ๐๐จ
The human heart has four chambers, which are responsible for pumping blood and maintaining blood circulation throughout the body.
The four chambers are named:
The right atrium
The left atrium
The right ventricle
The left ventricle
Blood is only pumped to one direction. Four heart valves ensure that blood does not flow backward within the heart.
๐๐๐ ๐๐ค๐ช๐ง ๐๐๐๐ง๐ฉ ๐๐๐ก๐ซ๐๐จ ๐๐ง๐ ๐๐๐ข๐๐:
*• The tricuspid valve (from tri- + cuspid, meaning "having threepoints") located between right atrium and ventricle.
* The pulmonary valve (from pulmon/o, meaning "lungs") located between right ventricle and pulmonary artery. Also called semilunarvalve.
*• The mitral valve, also called bicuspid valve ( from bi-+ cuspid, meaning "having two points") located between left atrium and ventricle.
*• The aortic valve located between left ventricle and aorta. The tricuspid and bicuspid valves are also called atrioventricular valves (meaning "located between the atrium and ventricle").
The pulmonary artery will deliver the deoxygenated blood to the lungs, where gas exchange occurs.
Oxygen is taken from the air into the blood (now called oxygenated blood), while carbon dioxide is expelled from the blood into the air. The oxygenated blood returns to the left side of the heart via the pulmonary veins.
The oxygenated blood enters the left atrium.
The left atrium pumps blood into the left ventricle. The mitral valve prevents blood from flowing backward into the left atrium.
The left ventricle pumps the blood into the aorta and systemic circulation. The oxygenated blood is delivered everywhere in the body (besides the lungs).
๐๐๐ป๐ฐ๐๐ถ๐ผ๐ป ๐ผ๐ณ ๐๐ต๐ฒ ๐๐ฒ๐ฎ๐ฟ๐
The heart functions to circulate blood around the body. The right and left side of the heart pump blood into two different circulations.
The right side pumps deoxygenated (from de- + oxygenated, meaning
"without oxygen") blood into the pulmonary circulation, while the
left side pumps oxygenated blood into the systemic circulation. The right atrium receives deoxygenated blood from the body tissues via the superior (from super- meaning "above") and inferior (meaning below) vena cava (from ven/o meaning "vein").
The blood enters the right atrium, which pumps the blood into the right ventricle. The tricuspid valve prevents blood from flowing backward into the right atrium. The right ventricle pumps the blood into the pulmonary artery via the pulmonary valve.
๐ฝ๐ก๐ค๐ค๐ ๐พ๐๐ง๐๐ช๐ก๐๐ฉ๐๐ค๐ฃ
Blood circulates around the body via two distinct pathways; the pulmonary circulation and the systemic circulation.
Together they create a closed pathways that keep the deoxygenated and oxygenated blood separated.
๐๐ช๐ก๐ข๐ค๐ฃ๐๐ง๐ฎ ๐พ๐๐ง๐๐ช๐ก๐๐ฉ๐๐ค๐ฃ
Pulmonary circulation begins at the right ventricle, where the deoxygenated blood from the body tissues is pumped into the pulmonary arteries and to the lungs.
In the lungs, the blood exchanges carbon dioxide (waste product of cellular respiration) to oxygen.
The oxygenated blood them travels back to the heart and the left atrium, via the pulmonary vein.
๐๐ฎ๐จ๐ฉ๐๐ข๐๐ ๐พ๐๐ง๐๐ช๐๐ฉ
The systemic circulation begins at the left ventricle that pumps oxygenated blood into the aorta.
Aorta branches out into smaller arteries, which carry the oxygenated
blood to the rest of the body (with the exception of lungs).
Oxygen is delivered to the body tissues and exchanged to carbon dioxide. The now deoxygenated blood is carried back to the heart and the right atrium via veins.
๐ผ๐ง๐ฉ๐๐ง๐๐๐จ ๐ซ๐จ ๐๐๐๐ฃ๐จ
The blood vessels that carry blood AWAY from heart are called arteries.
The blood vessels that carry blood TOWARD the heart are called veins.
Only in systemic circulation arteries carry oxygenated blood, while in the pulmonary circulation arteries carry deoxygenated blood.
๐๐ผ๐ป๐๐ฟ๐ฎ๐ฐ๐๐ถ๐ผ๐ป ๐ผ๐ณ ๐๐ต๐ฒ ๐๐ฒ๐ฎ๐ฟ๐
The contraction of the muscular wall of the heart chambers, called myocardium generates the force to pump blood.
The heart contraction is divided into two phases: systole (meaning "contraction") and diastole (meaning "relaxation").
Blood is pumped from the chambers during a contraction phase. The heart chambers are filled with blood during a relaxation phase.
๐๐ฃ๐ ๐ง๐ค๐ช๐ฃ๐ ๐ค๐ ๐๐๐๐ง๐ฉ ๐๐ค๐ฃ๐ฉ๐ง๐๐๐ฉ๐๐ค๐ฃ๐จ ๐๐๐ฃ ๐๐ ๐๐๐ซ๐๐๐๐ ๐๐ฃ๐ฉ๐ค ๐ฉ๐๐ ๐๐ค๐ก๐ก๐ค๐ฌ๐๐ฃ๐ ๐ฅ๐๐๐จ๐๐จ:
Relaxation phase → Blood flows from the atria into the ventricles passively via open atrioventricular valves.
The atrial systole → Contraction of atria. Pumps the rest of the blood into the ventricles.
The ventricular systole → Contraction of the ventricles. Forces blood into the pulmonary and systemic circulation. (During the ventricular systole, the atria relax and begin to fill with blood arriving from vena cava or the pulmonary veins.
Ventricular diastole → The ventricles and atria are relaxed.
๐ฆ๐ถ๐ป๐ผ๐ฎ๐๐ฟ๐ถ๐ฎ๐น (๐ฆ๐) ๐ก๐ผ๐ฑ๐ฒ
Myocardium contracts after it receives an electrical impulse generated by a specialized tissue located within the right atrium.
This is called the sinoatrial node (SA node), also called the pacemaker of the
heart. The SA node is a bundle of neurons that triggers the contraction of
the atria during the cardiac cycle.
The electrical currents next reach the ventricles, which contract after the atria. The SA node initiates approximately 75 electrical impulses each minute, with
variation between individuals' age and general health
๐๐๐ฟ๐ถ๐ผ๐๐ฒ๐ป๐๐ฟ๐ถ๐ฐ๐๐น๐ฎ๐ฟ ๐ป๐ผ๐ฑ๐ฒ (๐๐ฉ ๐ป๐ผ๐ฑ๐ฒ)
This small mass of neuromuscular tissue is situated in the wall of the atrial septum near the atrioventricular valves. Normally, the AV node merely transmits the electrical signals from the atria into the ventricles. There is a delay here; the electrical signal takes 0.1 of a second to pass through into the ventricles. This allows the atria to finish contracting before the ventricles start.
The AV node also has a secondary pacemaker function and takes over this role if there is a problem with the SA node itself, or with the transmission of impulses from the atria. Its intrinsic firing rate, however, is slower than that set by the SA node (40-60 beats per minute)
๐ง๐ต๐ฒ ๐ฃ๐๐ฟ๐ธ๐ถ๐ป๐ท๐ฒ ๐๐ถ๐ฏ๐ฒ๐ฟ๐
The Purkinje fibers are cells in the inner ventricle walls, just beneath the endocardium. These fibers run between the ventricles to the apex (bottom) of the heart. The Purkinje fibers play a crucial role in the cardiac cycle.
When an electrical stimulus leaves the AV node, it travels via the bundle of His and branches to the Purkinje fibers. These fibers then carry the impulse through the inner wall of each ventricle. This causes the ventricles to contract after the atria contract.
The ventricle contraction forces blood from the right ventricle to the lungs (pulmonary circulation) and from the left ventricle to the body (systemic circulation).
These three elements generate a healthy heart rhythm known as sinus rhythm. The rhythm, or contraction of the heart pumps blood throughout the body. In roughly a minute's time, blood travels from the heart to the body and back.
By : @ummedsaini_
