Heart n Circulation.pptx for GnM students

What is the circulatory system?
Your heart and blood vessels make up the circulatory system. The main function of the circulatory system is to provide oxygen, nutrients and hormones to muscles, tissues and organs throughout your body. Another part of the circulatory system is to remove waste from cells and organs so your body can dispose of it.

Your heart pumps blood to the body through a network of arteries and veins (blood vessels). Your circulatory system can also be defined as your cardiovascular system. Cardio means heart, and vascular refers to blood vessels.

Anatomy of the human circulatory system.
The circulatory system provides blood to all the body's tissues so they can function.

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Function
What does the circulatory system do?
The circulatory system’s function is to move blood throughout the body. This blood circulation keeps organs, muscles and tissues healthy and working to keep you alive.

The circulatory system also helps your body get rid of waste products. This waste includes:

Carbon dioxide from respiration (breathing).
Other chemical byproducts from your organs.
Waste from things you eat and drink.
How does the circulatory system work?
Your circulatory system functions with the help of blood vessels that include arteries, veins and capillaries. These blood vessels work with your heart and lungs to continuously circulate blood through your body. Here’s how:

The heart’s bottom right pumping chamber (right ventricle) sends blood that’s low in oxygen (oxygen-poor blood) to the lungs. Blood travels through the pulmonary trunk (the main pulmonary artery).
Blood cells pick up oxygen in the lungs.
Pulmonary veins carry the oxygenated blood from the lungs to the heart’s left atrium (upper heart chamber).
The left atrium sends the oxygenated blood into the left ventricle (lower chamber). This muscular part of the heart pumps blood out to the body through the arteries.
As it moves through your body and organs, blood collects and drops off nutrients, hormones and waste products.
The veins carry deoxygenated blood and carbon dioxide back to the heart, which sends the blood to the lungs.
Your lungs get rid of the carbon dioxide when you exhale.
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Anatomy
What are the circulatory system parts?
The parts of your circulatory system are your:

Heart, a muscular organ that pumps blood throughout your body.
Blood vessels, which include your arteries, veins and capillaries.
Blood, made up of red and white blood cells, plasma and platelets.
What are the circulatory system circuits?
Your circulatory system has three circuits. Blood circulates through your heart and through these circuits in a continuous pattern:

The pulmonary circuit:

1. CARDIOVASCULAR SYSTEM Prepared by: Mr. Sajjadhusen.S.S .

2. HEART The heart is a roughly cone-shaped hollow muscular organ. It is situated in the thoracic cavity in between two lungs, the area is known as mediastenum .

3. It is about 10 cm long and is the size of the owner’s fist. It weighs about 225 gm in women and is heavier in men (about 300-350 gm).

4. POSITION: The heart lies in the thoracic cavity in the mediastenum between to lungs. It lies obliquely, a little more to the left than the right, and presents base above, and apex below. The base extends at the level of 2 nd intercostals space and apex rests at 5 th intecostal space. The apex of heart is about 9 cm away from the midline.  

5. Organs associated with the heart: Inferiorly: diaphragm (apex rests) Superiorly: the great blood vessels, i.e. the aorta, superior venacava , pulmonary artery and pulmonary vein. Posteriorly : the esophagus, trachea, left and right bronchus, descending aorta, inferior venacava and thoracic vertebrae. Laterally: the lungs (right and left) Anteriorly : the sternum, ribs and intercostals muscles.

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7. STRUCTURE OF HEART: The heart is composed of three layers of tissue: Pericardium Myocardium Endocardium

8. Pericardium: The pericardium is made up of two sacs. The outer sac consists of fibrous tissue and the inner of a continuous double layer of serous membrane.

9. Myocardium: The myocardium is composed of specialized cardiac muscle found only in the heart. It is not under voluntary control .

10. Endocardium : This forms the lining of the myocardium and the heart valves. It is a smooth, glistening membrane which permits smooth flow of blood inside the heart. It consists of flattened epithelial cells.  

11. INTERIOR TO THE HEART: The heart is divided into four chambers. Longitudinally it is divided into left and right . Horizontally it is divided into upper and lower, upper one is called atria and lower one is called ventricles . Longitudinally each side is divided by a partition, called atrioventricular septum . Horizontally each side is divided by atrioventricular valves . The right atrioventricular valve ( tricuspid valve) has three flaps or cusps and left atrioventricular valve ( bicuspid valve/ mitral valve ) has two cusps.

12. FLOW OF BLOOD THROUGH THE HEART: The two largest veins of the body, the superior and inferior vena cavae , empty their content into the right atrium. This blood passes via the right atrioventricular valve in to the right ventricle, and from there it is pumped into the pulmonary artery or trunk (the only one artery in the body which carries deoxygenated blood). The opening of pulmonary artery is guarded by pulmonary valve , formed by semilunar cusps . This valve prevents backflow of blood into the right ventricle. After leaving the heart pulmonary artery divides into left and right pulmonary arteries, which carry the venous blood to the lungs where exchange of gases takes place, i.e. carbon dioxide is excreted and oxygen is absorbed.

13. Blood supply to the heart:   Arterial blood supply: the heart is supplied with arterial blood by the right and left coronary arteries which are branches of aorta (1st branch of ascending aorta). Venous drainage: venous blood is collected into small veins that join to form the coronary sinus which opens in to the right atrium.

14. CONDUCTING SYSTEM OF THE HEART: The heart has an intrinsic system whereby the cardiac muscle is automatically stimulated to contract without the need for a nerve supply from the brain. There are small groups of specialized neuromascular cells in the myocardium which initiate and conduct impulses causing coordinated and synchronized contraction of the heart muscle.

15. Sinoatrial node (S.A. node): This is small mass of specialised neuromascular cell situated in the right atrium near the opening of the superior vena cava. The SA node is the pace maker of the heart because it normally initiates impulses more rapidly than other groups of neuromascular cells.  

16. Atrioventricular node (A.V. node): This is small mass of neuromascular tissue situated in the wall of the atrial septum near the atrioventricular valves. Normally the AV node is stimulated by impulses that sweep over the atrial myocardium. However, it too is capable of initiating impulses that cause contraction but at a slower rate than the SA node.  

17. Atrioventricular bundle (AV bundle or bundle of His): This is a mass of specialized fibres that originate from the AV node. The AV bundle crosses the fibrous ring that seprarates atria and ventricles then, at the upper end of the ventricular septum, it divides into right and left bundle branches.

18. Within the ventricular myocardium the branches break up into fine fibres , called the purkinje fibres . The AV bundle, bundle branches and purkinje fibres convey electrical impulses from the AV node to the apex of the myocardium where the wave of ventricular contraction begins, then sweeps upwards and outwards, pumping blood into the pulmonary artery and the aorta.

19. F actors affecting heart rate Autonomic nervous system: The rate at which the heart beats is a balance of sympathetic and parasympathetic activity and this is the most important factor in determining heart rate. Circulating chemicals: The hormones adrenaline and noradrenaline , secreted by the adrenal medulla, have the same effect as sympathetic stimulation, i.e. they increase the heart rate Other hormones including thyroxine increase heart rate by their metabolic effect. Some drugs, dissolved gases and electrolytes in the blood may either increase or decrease the heart rate. Position.: When the person is upright, the heart rate is usually faster than when lying down.

20. Exercise. Active muscles need more blood than resting muscles and this is achieved by an increased heart rate and selective vasodilatation. Emotional states. During excitement, fear or anxiety the heart rate is increased. Other effects mediated by the sympathetic nervous system may be present. Gender. The heart rate is faster in women than men. Age. In babies and small children the heart rate is more rapid than in older children and adults.

21. THE CARDIAC CYCLE: The function of the heart is to maintain a constant circulation of blood throughout the body. The heart acts as a pump and its action consists of a series of events known as the cardiac cycle. During each heartbeat, or cardiac cycle, the heart contacts and then relaxes. The period of contraction is called systole and the period of relaxation is called diastole.

22. Stages of the cardiac cycle: The normal number of cardiac cycles per minute ranges from 60-80. Taking 74 as an example each cycle lasts about 0.8 of a second and consists of: Atrial systole: contraction of the atria Ventricular systole: contraction of the Complete cardiac diastole: relaxation of the atria and ventricles.

23. Heart sounds . Two sounds, separated by a short pause, can be clearly distinguished. They are described in words as ' lub dup'. The first sound, ' lub ', is fairly loud and is due to the closure of the atrioventricular valves. This corresponds with ventricular systole. The second sound, 'dup' , is softer and is due to the closure of the aortic and pulmonary valves. This corresponds with atrial systole.

24. Elecrocardiogram (ECG) The pattern of electrical activity may be displayed on an oscilloscope screen or traced on paper. The apparatus used is an electrocardiograph and the tracing is an electrocardiogram (ECG).  

25. The normal ECG tracing shows five waves which, by convention, have been named P, Q, R, S and T.

26. The P wave arises when the impulse from the SA node sweeps over the atria.   The QRS complex represents the very rapid spread of the impulse from the AV node through the AV bundle and the Purkinje fibres and the electrical activity of the ventricular muscle.   The T wave represents the relaxation of the ventricular muscle.  

27. The ECG described above originates from the SA node and is known as sinus rhythm . The rate of sinus rhythm is 60 to 100 beats per minute . A faster heart rate is called tachycardia and a slower heart rate, bradycardia .

28. Cardiac output     The cardiac output is the amount of blood ejected from the heart. The amount expelled by each contraction of the ventricles is called stroke volume .

29. Cardiac output is expressed in litres per minute (1/min) and is calculated by multiplying the stroke volume by the heart rate(measured in beats per minute): Cardiac output = Stroke volume x Heart rate.

30. The normal stroke volume is approximately 70 ml and if the heart rate is 72 per minute, the cardiac output is 51/minute