HEART

HEART : 

 

Features : 

• Heart is a conical hollow muscular organ situated in the middle mediastnum. 
• It is enclosed within the pericardium .
• It pumps blood to various parts of the body to meet their nutritive requirements .
• The greek name for the heart is cardia from which we have the adjective cardia. 
• The latin name for the heart is cor from which we have the adjective coronary. 
• The heart is placed obliquely behind the body of the sternum and adjoining part of the costal cartilages, so that one-third of it lies to the right and two-third to the left median plane. 
• Measurements : The heat measures about 12 ✖ 9 cm and weight about 300 g in males and in females 250 g in female 
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External Features : 

• The human heart has four chambers . 
• These are the right and left atria and right and left ventricles. 
• The atria lie above and behind the ventricles. On the surface of the heart , they are separated from the by ventricle an atrioventricular groove. 
• The atria are separated from each other by an  interatrial groove. 
• The ventricles are separated from each other by an interventricular groove, which is subdivided into anterior and posterior parts . 
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The heart has : 

• An apex directed downwards, forwards and to the left,
• A base (posterior surface) directed backwards 
• Anterior / sternocoastal
• Inferior and lateral surfaces. 

The surfaces are demarcated by upper, inferior, right and left borders . 

Chambers : 

• The heart has four chambers, two upper atria, the receiving chambers, and two lower ventricles, the discharging chambers. 

  
  

•  The atria open into the ventricles via the atrioventricular valves, present in the atrioventricular septum. 

• This distinction is visible also on the surface of the heart as the coronary sulcus.  

• There is an ear-shaped structure in the upper right atrium called the right atrial appendage, or auricle, and another in the upper left atrium, the left atrial appendage. 

• The right atrium and the right ventricle together are sometimes referred to as the right heart. 

• Similarly, the left atrium and the left ventricle together are sometimes referred to as the left heart.

•  The ventricles are separated from each other by the interventricular septum, visible on the surface of the heart as the anterior longitudinal sulcus and the posterior interventricular sulcus.

Valves : 

• The heart has four valves, which separate its chambers. One valve lies between each atrium and ventricle, and one valve rests at the exit of each ventricle.
• The valves between the atria and ventricles are called the atrioventricular valves.  
• Between the right atrium and the right ventricle is the tricuspid valve. 
• The tricuspid valve has three cusps,which connect to chordae tendinae and three papillary muscles named the anterior, posterior, and septal muscles, after their relative positions. The mitral valve lies between the left atrium and left ventricle.
•  It is also known as the bicuspid valve due to its having two cusps, an anterior and a posterior cusp.

Heart wall : 

• The heart wall is made up of three layers: the inner endocardium, middle myocardium and outer epicardium.
•  These are surrounded by a double-membraned sac called the pericardium.

Pericardium

• The pericardium is the sack that surrounds the heart. 
• The tough outer surface of the pericardium is called the fibrous membrane. 
• This is lined by a double inner membrane called the serous membrane that produces pericardial fluid to lubricate the surface of the heart.