11 Oct 2015

Circulatory system anatomy

The Circulatory system is one of the important organ systems in The human body consists of Heart and great vessels that circulate blood and transport nutrients, oxygen/carbon dioxide and hormones to various cells in the body.

Consists of,
        Blood vessels (Arteries, Veins, Capillaries)
        Blood consists of plasma, RBC, WBC, and platelets.

HEART: A muscular organ located in the chest at mediastinum between the lungs behind the sternum and above the diaphragm muscle. It pumps oxygenated blood to the various parts of the body and deoxygenated blood to the lungs. 

The heart wall has three layers (Outer epicardium, Middle myocardium, & Inner endocardium) Heart is enclosed by a sac called pericardium with pericardial fluid.

In the human heart, there are four chambers,

     1. Right and Left atrium
     2. Right and Left ventricle.

There are four valves present in the human heart,

 1.  Aortic valve - Between left ventricle and Aorta.
 2.  Pulmonary valve - Between the right ventricle and pulmonary artery.
 3.  Bicuspid valve / mitral valve - Between left atrium and left ventricle.   
 4.  Tricuspid valve - Between right atrium and right ventricle.

The heart valves are attached to the ventricular walls via the chordae tendineae 
they are attached to the papillary muscles so that the cusps are held in position.

The pericardium is double-walled sac covering the heart and greater vessels. Contain pericardial fluid.

Pulmonary circulation and Systemic circulation

The pulmonary circulation is the circulation of the blood between heart and lungs for purification of blood. The oxygen-less blood from the Superior and Inferior vena cava enters into the right atrium of the heart and flows through the tricuspid valve into the right ventricle; from their blood is pumped to the lungs through the pulmonary artery.

Gas exchange happens in the lungs at alveoli. The carbon dioxide is moved from blood capillaries to the lungs and oxygen is moved from lungs to blood capillaries. 

Four pulmonary vein returns the oxygen-rich blood to the left atrium of the heart. 

The systemic circulation is the circulation of the blood to all parts of the body from the heart. Systemic circulation is the portion of the cardiovascular system which transports oxygenated blood away from the heart through the aorta from the left ventricle.

Coronary Circulation: Supplying blood to heart muscles by Right and Left Coronary arteries.  The vessels that remove the deoxygenated blood from the heart muscle are known as cardiac veins.

Branches of the coronary circulation,  

From Aorta

      1. Right coronary artery (RCA)
                AV node artery
                Right marginal artery
                Posterior descending artery
                Posterio-lateral artery

      2.  Left coronary artery / Left main coronary artery (LMCA)
               Left circumflex artery (LCX)
                    Obtuse marginal artery
               Left anterior descending artery (LAD)
                    Diagonal artery 

The Aorta is the largest artery in the human body arises from the left ventricle of the heart. The aorta distributes oxygenated blood to all parts of the body through the systemic circulation.

The venae cava are large veins that return deoxygenated blood from the body into the heart. The superior vena cava and the inferior vena cava, both empty into the right atrium.

Arteries: Carry oxygen-rich blood away from the heart. Arteries branch into small passages called arterioles and then into the capillaries

Capillaries: Are the smallest and thinnest of the blood vessels in the body.  Capillaries carry blood very close to the cells of the tissues of the body in order to exchange gases, nutrients, and waste products

Veins: Carry oxygen-poor blood back to the heart. Capillaries merge into Venules – Veins - Vena cava.

The arteries possess stronger and thicker walls than the veins, three layers are,    
        1.  Tunica intima         
        2.  Tunica media          
        3.  Tunica externa

Electrical conduction system of the heart

The heart has the ability to create its own electrical impulses for continues involuntary functioning.

Impulses travel in the following order,

       1.   The sino-atrial (SA) node
       2.   The atrioventricular (AV) node
       3.   The bundle of His
       4.   The LT & RT bundle branches
       5.   The Purkinje fibres

Blood: The human body contains about 4 to 5 litres of blood. Blood is made up of RBC, WBC, platelets and plasma.

           Erythrocytes transport oxygen in the blood through the red pigment hemoglobin

            Important functions in the body’s immune system.
            Neutrophils, eosinophils, basophils, lymphocytes and monocytes

    C. PLATELETS / Thrombocytes
           Responsible for the clotting of blood.
           Platelets normally remain inactive in the blood until they reach damaged tissue or leak out of the blood vessels through a wound.

          The liquid portion of the blood that makes up about 55% of the blood’s volume.
          Around 90% of plasma is made of water.

BLOOD PRESSURE: Refers to the pressure in large arteries of the systemic circulation,   

          SYSTOLIC   -  Ventricles contracts
          DIASTOLIC -   Ventricles relax

Normal Values:
    Normal BP: 120 / 80 mmHg

    Pulse rate - 72 beat per min

    RBC – 4 to 6 million cells per microliter of blood

    WBC – 4000 to 11000 per microliter of blood

    Platelet – 150,000 to 450,000 cells per microliter of blood

Common Disease of Circulatory System:

1. Aortic aneurysm - is a bulge in a section of the aorta.   

2. Coronary artery disease (CAD) – is a disease in which a waxy substance called plaque builds up inside the coronary arteries.        

3. Deep vein thrombosis - A blood clot in a deep vein, usually in the legs.

4. Rheumatic Heart disease – Permanent damage to heart valves is caused by rheumatic fever.

5. Atherosclerosis – Is a disease of the arterial vessels, in which the walls of the blood vessels became thickened and hardened by plaques.

6. Hypertension – Is a condition in which the arteries have persistently elevated blood pressure.

7. Hypercholesterolemia – Is the presence of high levels of cholesterol in the blood.

8. Myocardial Infarction - is the irreversible death (necrosis) of heart muscle secondary to prolonged lack of blood (oxygen) supply.


1.  Heart                     - Cardio
2.  Vessels                  - Angio / Vasculo / Vaso                                 
3.  Artery                   - Arterio                    
4.  Veins                     - Phlebo       
5.  Blood                    - Hemato
6.  RBC                      - Erythrocytes          
7.  WBC                     - Leukocytes
8.  Platelet                 - Thrombocytes


1. ABI - Ankle-brachial index

2. ABG - Arterial blood gas

3. ASHD - Arteriosclerotic heart disease

4. BP - Blood pressure

5. CABG - Coronary artery bypass graft

6. CAD - Coronary artery disease

7. CHF - Congestive heart failure

8. CPR - Cardiopulmonary resuscitation

9. CVP - Central venous pressure

10. DVT - Deep vein thrombosis

11. ECG – Electrocardiogram

12. ESR - Erythrocyte sedimentation rate

13. FHT - Fetal heart tones

14. HB – Hemoglobin

15. HDL - High-density lipoprotein

16. HTN – Hypertension

17. ICA - Internal carotid artery

18. LAD - left anterior descending

19. LCA - Left coronary artery

20. LDL - Low-density lipoprotein

21. LVH - Left ventricular hypertrophy

22. MI - Mitral insufficiency; myocardial infarction

23. PICC - Peripherally inserted central catheter

24. PTCA - Percutaneous transluminal coronary angioplasty

25. RVH - Right ventricular hypertrophy

26. SVT - Supraventricular tachycardia

27. WBC - White blood cell


Test your Knowledge:

                A. Circulatory System Anatomy Quiz