Heart-blogwriterjony

 Heart

Defination:

The heart is a conical hollow muscular organ situated in the middle mediastinum,that pumps blood to and from various parts of the body.

Position:

The heart lies obliquely behand the body of the sternum and adjoining parts of the costal cartilages.So,one-third of it lies to the right and two-third to the left of the median plane.

Structure of the heart: 

The heart is composed of three layers of tissue:

1.pericardium

2.myocardium.

3.Endocardium.

Surfaces of the heart:

  1.Anterior or sternocostal surface.

2.Inferior or diaphragmatic surface.

3.Posterior surface or base.

Base of the heart:  

The great veins enter the base of the heart -four Pulmonary veins enter the left atrium ;and superior and inferior venae cavae the right atrium.

Apex of the heart:  

The apex projects from the heart forwar, dawnward and to the left.

Border of the heart:

1.Right border.

2. Inferior border,at the left extremely of which is the apex.

3. Left border,which separates the anterior and left surface of the heart.

Chember of the heart:

Mention the different chembers of the heart.

The heart has four chambers: right and left atria,and right and left ventricles.The tissue separating the two atria is the interatrial septum,and that separating the two ventricles is the interventricular septum.

Right atrium:

It is the right upper chamber of the hear.. It receive venous blood from the whole body through three vessels:

1.Superior vena cava.

2.Inferior vena cava.

3. Coronary sinus,which retruns blood from the walls of the heart itself.

Right atrium pumps blood to the right ventricle through the right atrioventricular or tricuspid opening.

Internal features of Right atrium:

1. The interior of the right atrium is divided into two continuous spaces: smooth-walled posterior part and rough-walled anterior part.Internally, this division is marked by the crista terminalis,which is a smooth,muscular ridge.it corresponds to sulcus terminalis externally.

2.Rough anterior part presents musculi pectinati, which fan out from the crista terminalis like the 'teeth of a comb.

3. Interatrial septum,that separating the right atrium from the left atriu, presents fossa ovalis,It is a depression just above the orifice of the inferior vena cava.

Right ventricle:

The right ventricle is a triangular chamber which receives blood from the right atrium and pumps it to the lungs through the pulmonary trunk and pulmonary arteries.

Internal features of right ventricle:

1. The outflow trach of the right ventricle,which leads to the pulmonary trunk,is the conus arteriosus. This area is smooth.

2. Trabeculae carnae are irregular muscular ridges.

3. Papillary muscles. There are three papillary muscles lying among the trabeculae carnae.These are-anterior,posterior and septal.    

Left atrium:

The left atrium is a quadrangular chamber situated posteriorly.it recives oxygenated blood from the lungs through four pulmonary veins,and pumps it to the left ventricle through left atrioventricle orifice.

Left ventricle:

Left ventricle is a conical chamber,is longer than the right ventricle,and has the thickest layer of myocardium.

Internal features of the left ventricle:

1. Trabeculae carnae.

2.Two Pulmonary muscle -anterior and posterior.

3.Two orifices -left atrioventricular or mitral orifice and aortic orifice.

 

Valves of the heart:

 

For maintaining unidirectional blood flow through the heart,it contains four valves in its orifices: tricuspid, Pulmonary, mitral, aortic. 

 

Tricuspid valves : 

1.The right atrioventricular valve is known as the tricuspid valve because it has three cusps or leaflets.

2. The three cusps are named as - anterior, septal and posterior cusps.

3. The base of each cusps is attached to the febrous ring that surrounds the atrioventricular orifice.The febrous ring helps to maintain the shape of the opening. 

4. The free margins of the cusps are attached to the chordae tendinae, which arise from the tips of the papillary muscles.

Mitral valves:

1. The left atrioventricular valve is known as the bicuspid valve because it has two cusps. It is also referred to as the mitral valve.

2. The two cusps are named as - anterior and posterior cusps.

3.The bases of the cusps are attached to a fibrous ring surroundings the left atrioventricular opening. 

4. The valve acts by coordinated action of the papillary muscles and chordae tendinae.

Function of tricuspid and mitral valve:

Prevent back flow of blood from the ventricles into the area.

Blood suply of the heart :

The heart is supplied with arterial blood by the right and left coronary artery.