Anatomy and physiology of heart

A small and clear introduction of Heart Anatomy and its function.

1. Anatomy And Physiology Of The Heart Amrutha Nayaka P, 2 nd year Bsc Nursing, Kidwai College Of Nursing, Bengaluru .

2. Contents General Features of the Heart External Features of the Heart Chambers of the Heart Circulation of the Heart Difference between Artery And Vein Cardiac Cycle

3. General Features Heart is a pumping organ, that pumps blood to all parts of the body. It is conical in shape with base upwards and apex below. It is 350gms in Males and 250gms in females. Heart is appoximately the sixe of a persons closed fist. It is located in the chest cavity between the two lungs. It is places obliguely behind the sternum, ¼ to the right of the sternum & ¾ to the left of sternum. It extends b/w 2 nd to 6 th rib on the left side & is placed over the diaphragm

4. External features Heart consists of 4 chambers, 2 Atrium and 2 Ventricles On anterior surface of atria, there is lace like structure called Auricle. Atria are separated from the ventricles by the AV groove. Opening into the right atrium are; SVC [superior Vena Cava] IVC [Inferior Vena Cava] Opening of the coronary sinus

5. Opening into left Atrium are 4 pulmonary veins, two from each lungs. Arising from the right ventricle is the pulmonary trunk, which divides into two pulmonary arteries near the base of the heart. Arising from the Left Ventricle is the Aorta which form the arch of Aorta, near the base of The heart. Heart shows the right border, left border, inferior border, a base & an apex.

6. Chambers of the Heart : Right Atrium : It forms the right border of Heart. On Anterior surface on the right side, there is yellow lace like structure called Auricle, which helps to increase the capacity of the Right Atrium. Cut section shows inside the right atrium there are important structure, SA Node AV Node Fossa Ovalis

7. Conted …… Opening into the right Atrium are, SVC ( superior Vena Cava) IVC (Inferior Vena Cava) Opening of the common sinus Opening of the right aurical into Right Ventrical called Right Atrio ventricular opening, where the opening is guarded by the right AVV or tricuspid valve.

8. Right Ventricle It forms the inferior border Of the heart. Cut section shows right Ventrical is sepreted from left ventrical by the inter Ventricular septum. Cut section of wall shows 3 layers Outter most pericardium Middle thick Myocardium, Inner most E ndocardium. Inside the right ventricle there is a rough lower area & smooth upper area

9. The rough area is due to a network of muscular fibres called Trabeculae cornae from which arises 3 pyramid shaped muscular structres called Papillary Muscles. The tips of the papillary muscles give attchment to one end of a chordae tendinae , the other end is attached to tricuspid valve. From the upper smooth area arises the pulmonary trunk, the opening of the pulmonary trunk is guarded by semilunar valve. pulmonary trunk rises upwards and near the base of the heart, it divides into 2 pulmonary arteries, one for each lung.

10. Left Atrium It forms a base of the heart On the surface of the left side, there is a yellow lace like structure called auricle, which helps to increase the capacity of left atrium. Inside the left atrium it is very smooth. Four pulmonary vein, 2 form each lung open into the left atrium. Left atrium opens into left ventricle through the left AV opening which is guarded by the bicuspid value or mitral valve.

11. Left Ventricle It forms the left border of the Heart. Cut section shows left ventricle Is separated from right ventricle, by the intra ventricular septum. Cut section of walls shows 3 layer, Outer most pericardium Middle thick myocardium Inner most endocardium

12. Inside the left ventricle there is a rough area , due to a network of muscle fibres called Trabeculae Cornae, from which arise two pyramid shaped muscular structures called papillary muscles. The tips of papillary muscles gives attachment to one end of a chordae tendinae , while the other end is attached to the Bicuspid valve. From the upper smooth area arises the Aorta whose opening is guarded by the Semilunar Valve.

13. Circulation Of the Heart 3 main circulations play an important role in blood circulation of the heart, They are; Systemic Circulation Pulmonary Circulation Portal Circulation

14. 1 . Systemic Circulation : Pure blood flows from the left Ventricle, p usses out through The Aorta & distributed to all the Tissues in the body, where it Burst Up into 5 blood capillary. All the capillaries in the tissue, joins to form veins, that carry impure blood & return it to the right Atrium.

15. 2. Pulmonary Circulation: Impure blood from the right atrium enters the right Ventricle is carried forward by the pulmonary Trunk & to the pulmonary artery enters the lungs. In the lung the blood gets oxygenated & pure blood is brought back from the lungs to the atrium, through four pulmonary veins, two from each lung.

16. 3.Potal Circulation It is the special type of circulation of blood , seen only in human beings, In this type of circulation there are 2 sets of capillaries, one in the intestine and one in the liver. All the digested food, drugs are absorbed in the intestine by the superior and inferior misentric veins. These 2 veins rises upwards & open into the splenic vein coming from the spleen, to form the portal vein.

17. Portal vein runs horizontally towards the right, rises upwards to enter the liver. Before entering the liver, cystic vein and left gastric vein from the stomach, opens into the portal vein. Inside the liver, portal vein breaks up into the second set of capillaries. All the capillaries joint to form 4 to 5 hepatic veins that open into the Inferior vena cava on the posterior surface of the liver. By this portal circulation of blood, all the harmful substances, drugs, alcohol removed or detoxified in the liver and purified blood is sent into general circulation.

18. Difference Between Artery And Veins Sl No. Feature Artery Veins 01 Valves Absent Present 02 Direction Blood towards the heart Away from the heart 03 Lumen size Small Large 04 Type of blood Oxygenated blood Dioxygenated blood 05 Tunica media Thicker thinner 06 Location Always deep Superficial or deep 07 Pressure in the blood vessles Pressure present No pressure 08 Flow of blood Towards gravity Against Gravity

19. Cardiac Cycle Definition : The changes taking place in the heart during one beat, it is repeated in the same order, beat after beat, this is called Cardiac Cycle. Cardiac cycle time is 0.8 sec .

20. 1} On set of ventricular contraction: Just before the ventrical are going to contract, AVV close producing 1 st sound ‘S1’ 2} Isometric Contraction Period : Semilunar valve will not open, until the pressure in the ventricles is very high, then that in the aorta or pulmonary trunk, until the ventricles are contracting as closed cavities, this is called Isometric contraction period. 3} Maximum ejection period: After sometimes the pressure in the ventricles is more, then that in the aorta or pulmonary trunk, i.e. SLV open & blood rushes out, this is called Maximum Ejection period.

21. 4} Isometric Relaxation Period: Once the blood goes out into the aorta and pulmonary trunk , pressure inside the ventricles falls, as a result, blood tries to fall back into the ventricle, but SLV are like pockets which closes And Produc e ‘S2’ . AVV will not open until the presser in the ventricle is very low, as there relaxing, mean while pressure is build up in the Atria as they are getting filled up with blood, i.e. the ventricles are relaxing as close cavity, this is called Isometric Relaxation period. 5} 1st Rapid Filling Period : After some time, the p ressure in the Aorta is very high, then that in the ventricles , AVV open and blood rushes into ventricles produces 3 rd sound that is ‘S3’ . This is called 1 st rapid filling period.

22. 6} Last rapid filling period: Any remaining blood in the Atria is pushed into ventricles Producing 4 th sound ‘S4”. This is called last rapid filling period. Now AVV close and cycle is repeated .

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