The Cardio-Vascular System The Heart, Blood Vessels, Blood Types

The Closed Circulatory System ……….typical of all vertebrates, in which blood is confined to vessels and is distinct from the interstitial fluid. The heart pumps blood into large vessels that branch into smaller ones leading into the organs.

The Cardiovascular System 3 Major Elements :– Heart, Blood Vessels & Blood 1. The Heart - cardiac muscle tissue – highly interconnected cells – Located in the thoracic cavity – 4 chambers Right atrium Right ventricle Left atrium Left ventricle

The Cardiovascular System ….contd 2. Blood Vessels -A network of tubes –Arteries  arterioles Carry blood away from heart and carry it to the capillaries Made of elastic fibers – Capillaries Microscopic vessels where gas exchange between cells and blood takes place –Veins  Venules Receive blood from capillaries and carry it back to the heart

3. The Blood A.Plasma Liquid portion of the blood. Contains clotting factors, hormones, antibodies, dissolved gases, nutrients and waste B. Blood Cells i.Erythrocytes/Red Blood Cells/RBCs  Carry hemoglobin and oxygen.  Do not have a nucleus and  live only about 120 days.  Can not repair themselves. The Cardiovascular System ….contd

ii.Leukocytes/White Blood cells/WBCs  Fight infection and are formed in the bone marrow  5 types – lymphocytes, monocytes, neutrophils, eosinophils & basophils. iii.Thrombocytes/Platelets  These are cell fragment that are formed from magakaryocytes in the bone marrow.  Clot Blood by sticking together – via protein fibers called fibrin. The Cardiovascular System ….contd

Size, Shape & Location of the Heart Size of a closed fist (The hand closed tightly with the fingers bent against the palm) Shape –Apex: Blunt rounded point of cone –Base: Flat part at opposite of end of cone Located in thoracic cavity in mediastinum

4 chambers –2 atria –2 ventricles Auricles (a small sac in the atrium of the heart) Major veins –Superior vena cava –Pulmonary veins Major arteries –Aorta –Pulmonary trunk External Anatomy of Heart

–Interatrial septum Separates atria –Interventricular septum Separates ventricles –Atrioventricular valves Located between atrium and ventricle Ensure one-way flow from atrium to ventricle Internal Anatomy of Heart

Functional Anatomy of Heart Left ventricular myocardium much thicker than right –Reflects functional difference in load Valves ensure one-way flow of blood –Prevent backward flow (regurgitation) Fibrous skeleton supports valves and muscle cells

What is Heart Skeleton ?  Consists of plate of fibrous connective tissue between atria and ventricles  Fibrous rings around the valves to support them  Serves as electrical insulation between atria and ventricles  Provides site for muscle attachment

Circuits of Heart Heart Pumps Blood into 2 circuits in Sequence Pulmonary circuit To and from the lungs Systemic circuit To and from the rest of the body Pulmonary circuit The blood pathway between the right side of the heart, to the lungs and back to the left side of the heart. Systemic circuit The pathway between the left and right sides of the heart.

Why Heart is Called a Double Pump ? 2 Sets of Pumping Chambers in Heart –Right atrium Receives systemic blood –Right ventricle Pumps blood to lungs (pulmonary) –Left atrium Receives blood from lungs –Left ventricle Pumps blood to organ systems (systemic)

Why Heart is Called a Double Pump ? contd

Blood Flow in Heart

Passage of Blood Through the Heart Superior and Inferior vena cava (O 2 -poor)  Right Atrium. R Atrium  Tricuspid Valve  Right Ventricle. R Ventricle  Pulmonary SL valve  Pulmonary Arteries  Lungs. Pulmonary veins (O 2 -rich)  Left Atrium. L Atrium  Mitral valve  Left Ventricle. L Ventricle  Aortic SL valve  ALL body tissues.

Passage of Blood Through the Heart ……Contd

Layers of the Heart Wall 3 layers –Epicardium: This is serous membrane of smooth outermost surface of heart –Myocardium: Middle layer (thicker) composed of cardiac muscle cell and responsibile for heart contraction –Endocardium: Smooth inner surface of heart chambers

Valves of the Heart Atrioventricular –Tricuspid (Right) –Bicuspid or mitral (Left) Semilunar –Aortic –Pulmonary 1.Prevent blood from flowing back (Regurgitation). 2.Control the flow of blood in one direction. 3.Involved in the production of heart sound

Valves of the Heart …..contd Right atrioventricular Valves: it is also called tricuspid as it has 3 cusps. These are 1.Anterior or infundibular 2.Posterior or marginal 3.Medial or septal Left atrio-ventricular valves: It is also called mitral or bicuspid valve as it has 2 cusps. These are 1.Anterior 2.Posterior Semilunar valve: 2 in number, one in aortic and another in pulmonary opening. They each have 3 cusps.

Functions of the Heart  Generating blood pressure  Routing blood –Heart separates pulmonary and systemic circulations  Ensuring one-way blood flow –Heart valves ensure one-way flow  Regulating blood supply –Changes in contraction rate and force match blood delivery to changing metabolic needs

Junction tissues of the Heart

1.SA Node Situation: it is situated in the right atrium at the junction of superior vanacava and right auricular appendage. It extends downwards for about 2 cm. Junction tissues of the Heart …..contd

Function of SA Node: 1.It can initiate the physiological cardiac impulse before any other part of the heart. 2.It can discharge impulse at a rate of about impulse/min SA Node is Known as PACE MAKER Pace Maker: Means the regulation of motion. SA node is called pace maker of the heart. Because it can initiate normal physiological impulse at first and the rate of discharge in greater than any other part of the heart. Junction tissues of the Heart …..contd

2. Internodal Pathway: It is the pathway that conduct the impulse from the SA node to AV node and left atrium. These internodal tracts contain purkinje type of fibers. Goldman has described 3 internodal pathway a.Anterior internodal tracts b.Middle internodal pathway c.Posterior internodal pathway Function: the interior internodal tracts serves as preferential pathways for conduction of impulse from SA node to AV node and left atrium. Junction tissues of the Heart …..contd

3. AV node: Situation: it is situated at the posterior and right border of the interatrial septum near the opening of the coronary sinus. Function: 1.It receives impulse originating from SA node and transmit it to the ventricle through the bundle of His at a rate of 0.1 m/sec 2.AV node can produce impulse when SA node can fail to produce impulse. So it is called “Reserve pace- maker” 3.The rate of AV nodal impulse is impulse/ min Junction tissues of the Heart …..contd

4. Bundle of His : Situation: it extends from AV nodes. It gives off a left bundle branch at the top of the inter ventricular septum and continues at the right bundle branch. Function: 1.Conduction: its main function is to conduct the atrial impulse into ventricle 2.Rhythmicity: When SA node and AV node fails, the bundle of his can originate cardiac impulse at a rate of impulse/min Junction tissues of the Heart …..contd

5. Purkinje Fiber : Situation: It arises from the branches of the bundle of his, spread from interventricular septum directly to the papillary muscle and then to the lateral walls of the ventricle ending ultimately with the subendocardial network. Function: 1.To conduct impulse quickly to every part of ventricular muscle fiber 2.It can also initiate impulse incase of atrio-ventricular dissociation at a rate of 15 to 40 impulse/min. Junction tissues of the Heart …..contd

What is Pace maker ? The general meaning of pace maker is that the rider or runner who sets the pace (to set the rate of speed for) of the race. SA node is called the pace maker. It produces impulse/min, which is coincides with the heart rate. SA node is called the pace maker because 1.It originates the impulse at first 2.It maintains the normal cardiac rhythm 3.The rate and rhythm originated by SA node is higher than that of all.

Reserve pace maker When the SA node fails to generate impulse then the AV node become the pace maker and produces impulse at its own rate of impulse/min. so it is called reserve pace maker. Then the heart contracts at a rate of impulse/min. Ectopic Pace Maker: A Pace maker elsewhere than SA node is called ectopic pace maker. Obviously, an ectopic pace maker causes an abnormal sequence of contraction of different part of heart. This often occurs in the AV node or in purkinje fibers.

Location of Heart Valves